Neurophysiology

Normal intraocular pressure

*15 mmHg (range = 12-20 mmHg)*: tonometer can be used to measure intraocular pressure = small footplate placed on anesthetized cornea --> small force applied to footplate = displaces cornea inward --> distance of displacement = calibrated in terms of intraocular pressure

Rate of formation of aqueous humor

*2-3 microliters/min* - active transport of Na+ from epithelium --> causes Cl- and HCO3- to follow --> osmosis

Refractive power of *lens*

*20 diopters*: total refractive power of eye = 59 diopters

Warm receptors respond to what temperatures?

*30 - 49 C* - peak response at 44 C

Receptive field of Ruffini corpuscle

*60 mm^2* = encapsulated endings located in skin & deeper tissues & in joint capsule = little adaptation & signal continuous touch & pressure applied to skin or movement around joint where they are located

Cold receptors respond to what temperatures?

*7 - 44 C*: Both cold & warmth receptors can be stimulated with temperatures in range of 31-43 C: (peak response at *24-25* C)

Fibers responsible for localization of pain stimulus

*A-delta pain fibers*: Neospinothalamic tract facilitates pain localization; axons from lamina I that form neospinothalamic tract cross midline close to their origin & ascend white matter of spinal cord as part of ALS --> some fibers terminate in brain stem reticular formation, but most project all the way to VPL nucleus of thalamus (ventrobasal thalamus) --> project to primary somatosensory (SI) cortex = *localization of painful stimuli*

When multiple terminals are excited simultaneously, the EPSP generated may exceed the threshold for firing and induce an

*AP* via spatial summation = enables EPSPs to exceed threshold value for AP

Pacinian corpuscle most likely connected to spinal cord via

*Abeta* nerve fibers = large, rapidly conducting myelinated fibers --> detect most rapid vibratory stimuli (30-800 cycles/sec) via posterior column-medial lemniscus pathway = group II fibers

Pacinian corpuscle fiber type

*Abeta* nerve fibers = touch

Mechanism of fluid secretion

*Active transport of Na+ by epithelial cells*: Cl- follows Na+ = immediate osmosis of water

*Myelinated* free nerve endings fiber type

*Adelta*: free nerve endings linked to small myelinated, type Adelta fibers & unmyelinated type C fibers that conduct at relatively slow velocities

What pH *increases neuronal excitability*?

*Alkalosis* - epileptic attack - pH change from 7.4 to 8 usually induces seizures

Form direct synaptic contact with skeletal *extrafusal* muscle fibers

*Alpha motor neurons* - intrafusal muscle fibers innervated by Gamma motor neurons

What structure connects Wernicke's area to Broca's area in cerebral cortex?

*Arcuate fasciculus* = form part of superior longitudinal fasciculus = connects caudal temporal cortex (Wernicke) & inferior parietal cortex to locations in frontal lobe (Broca)

Inability to recognize objects by touch

*Astereognosis* = via lesions involving primary somatosensory cortex

Loud noise initiates reflex contraction, causing ossicular system to develop rigidity

*Attenutation / stapedius / auditory / acoustic reflex* - both muscles (*stapedius, tensor tympani*) involved - attenuates vibration going to cochlea - can reduce sound transmission by 30-40 decibels - *protects cochlea* & *dampens low frequency sounds* (own voice ~ 1000 Hz) - takes 40-80 msec to activate Reflex damping of malleus is performed by stapedius muscle = acts as antagonist to tensor tympani --> rigidity of ossicular chain is increased & conduction of sound, at lower frequencies, is greatly reduced - same mechanism used to diminish sensitivity to one's own speech

Restricts entry of water soluble drugs used to treat tumors or infections

*BBB* - AIDs virus hides behind BBB

Where are enkephalins and dynoprhins found?

*Brainstem and spinal cord* - endogenous opiates Neurons in periaqueductal gray & nucleus raphe magnus have opiate receptors on surface membranes --> stimulated by exogenously administered opioid compounds (analgesics) or by *endogenous opioid NT agents (endorphins & enkephalins) found in brain* = pain suppression circuitry activated = reduced pain perception

Epileptic seizure triggered under

*Bright lights and hyperventilation* - Generalized tonic-clonic seizures can in susceptible individuals by: strong emotional stiumli, *alkalosis caused by hyperventilation*, drugs, fever, loud noise or *flashing light* - brain trauma & tumors can lead to seizure activity - pH change from 7.4 to 8 - hyperexcitable hippocampus

What ion is higher during facilitation in a presynaptic neuron?

*Calcium*: Each excitatory post-synaptic current (EPSC) is triggered by pre-synaptic calcium concentrations

Heat activated calcium channel

*Capsaicin receptor* - normally opens between 37 and 45 degrees C --> capsaicin + receptor = sensation of *heat felt*

Posterior and lateral hypothalamus, in combo with preoptic area, are involved in control of what function?

*Cardiovascular* functions involving blood pressure and heart rate

What condition cannot be corrected by placing lens system in front of eye?

*Cataracts* = precipitated proteins - myopia = can put lens in front of retina

What component of basal ganglia plays major role in control of *cognitive (memory-guided)* motor activity?

*Caudate nucleus* = control of motor patterns linked to memory of previous experience; when judgement or memory of past experience associated with movement, it is likely that circuits via caudate nucleus are involved in controlling the actions

Ion most likely to have least effect on membrane potential

*Chloride* = inhibitory

Red light rays focus posteriorly compared to blue light rays. Eye can tell which is better focus and relay info to accomodation mechanism. This is known as

*Chromatic aberration* = color fringing / purple fringing = common optical problem = lens *unable to bring all wavelengths of color to same focal plane* or when wavelengths of color are focused at different positions in focal plane

- Inflammation of skin of canal - tender pain - repeated over time --> stenosis --> small pinpoint opening --> hearing loss - treatment = antibiotics

*Chronic External Otitis / Swimmer's Ear* = not enough earwax in ear, too much water in ears, overcleaning ear canal

What type of papillae is located in posterior part of tongue?

*Circumvallate papillae*: fungiform papilla are found on anterior 2/3 of tongue, circumvallate papillae form V-shaped configuration on posterior third of tongue, foliate papillae found along lateral margins of tongue

What is thought to change the metabolic rate of the receptor?

*Cold or warm* --> changes rate of intracellular reactions - stimulatory mechanism in thermal receptors via temperature-induced changes in metabolic rate in nerve fiber - For every 10 C temperature change, there is a twofold change in rate of intracellular chemical reactions - density of thermal receptors on skin surface is small --> temp changes that affect only small surface area not as effectively detected as temp changes that affect large areas of skin - Entire body stimulated? --> temp change as small as 0.01 C detected - thermal signals transmitted through CNS in parallel with pain signals

What type of lens diverges light rays?

*Concave* lens: at lens perimeter, light waves are refracted so they travel perpendicular to wave front / interface & are bent away from those passing through central region = *divergence*

*GJB2* locus on chromosome *13q11* encodes for

*Connexin 26* protein = most common cause of *congenital sensorineural hearing loss* (at least 20% of all genetic hearing loss & 10% of all childhood hearing loss) = involved in K+ homeostasis in cochlea of inner ear = found in supporting cells, fibrocytes of spiral ligament, & in cells of spiral limbus - common locus across populations - all different types of mutation

Mechanism of Accommodation

*Contraction of ciliary muscle* --> pulls ligament forward --> *relaxes* tension on *suspensory ligament* = makes lens *thicker (rounder)*: refractive power of lens is 20 diopters --> can be increased to 34 diopters by making lens thicker

Functional role of intermediate zone of cerebellum

*Controls movements that involve distal cortex of intermediate zone*; projects to globose & emboliform nuclei --> transmitted to cerebral cortex & basal ganglia limb musculature

What provides spatial summation?

*Convergence from single source* - multiple terminals from single incoming fiber terminate on same neuron - 2 or more presynaptic axon terminals activated simultaneously --> ind. effects are summated = postsynaptic potential increased - Enables EPSPs to exceed the threshold value for an AP

What type of lens *focuses* light rays?

*Convex* lens: light rays that pass through lens perimeter are bent / refracted toward those that pass through central region (to make themselves perpendicular to wave front) --> light waves converge

Naloxone used to...

*Counter effects of opiate overdose* *Congenital insensitivity to pain (congenital analgesia)* - overproduction of endorphins, lack of voltage-gated Na+ channels *Congenital insensitivity to pain with anhydrosis (CIPA)* - lack neurons that transmit pain, heat, cold

Withdrawal reflex is initiated by stimulation delivered to what receptor?

*Cutaneous free nerve ending*: withdrawal/flexor reflex via *pain receptors* in skin --> muscles activated required to remove body part away from painful stimulus = typically *flexor* muscles in the limbs --> sensory fibers terminate on pool of spinal cord interneurons = excitatory input to appropriate ventral horn motor neurons

Underlying basis of dark current in outer segment of photoreceptors

*Dark currents via influx of sodium ions via cGMP-dependent sodium channels* - in dark/absence of photic stimulation --> rod outer segment membranes "leaky" to sodium = sodium ions *enter* outer segment --> alter membrane potential from -70/-80 mV to move positive -40 mV = *dark/sodium current*

In a muscle spindle receptor, what type of muscle fiber is responsible for dynamic response?

*Dynamic nuclear bag fiber* - responds to rate of change of length of muscle spindle receptor = dynamic response of muscle spindle - nuclei aggregated or clumped in central region - typically, muscle spindle contains one to three nuclear bag fibers and 3-9 nuclear chain fibers - mainly associated with primary endings - gamma motor neurons distributing to nuclear bag fibers = dynamic

Sensory receptors that detect light

*Electromagnetic* = photoreceptors = detect light that strike retina

Pool of presynaptic neurons innervate dendrites of postsynaptic neuron. Electrical signals are transferred from dendrites to soma of postsynaptic neuron by what process?

*Electrotonic conduction*: dendrites contain few voltage-gated ion channels & are not able to propagate APs --> instead, they serve to spread electrical current via *electrotonic conduction* = subject to decay (decrement) over time & space

Excessive contraction of ciliary muscle in attempt to focus; contraction of facial muscles...

*Eye strain* - difficulty in focusing eyes --> excessive contraction of ciliary muscle & muscles of face, such as when person squints to sharpen focus of an object --> contraction can lead to eye & facial pain = *eyestrain type of headache* - emotional tension can cause muscles of head, especially those attached to scalp & neck, to become spastic & irritate the attachment areas - irritation of nasal & accessory nasal structure can lead to "sinus headache"

Function of Merkel discs

*Form and texture perception* = expanded tip receptors; in glabrous skin; slowly adapting; signal continuous touch of objects against skin

What lobe of the cerebral cortex contains small bilateral cortical area that controls *voluntary fixation movements*?

*Frontal* - Voluntary fixation controlled by *frontal eye fields (Brodmann's area 8) and area in occipital lobe that represents portion of secondary visual cortex (area 19)* - *lesion* of this region = makes it difficult for person to *unlock their eyes* from one point of fixation and move them to another point

Function of lateral hemispheres of cerebellum

*Function with cerebral cortex to plan movements* = receive input primarily from cerebral cortex via basilar pontine nuclei; *plan of intended, sequential movement is thought to be transmitted from premotor & sensory cortex to basilar pons & then to cerebellar nuclei & cortex of lateral hemisphere*

States that stimulation of type A-beta fibers from peripheral tactile receptors can decrease transmission of pain signals

*Gate theory of pain*: non-painful input closes "gates" to painful input --> prevents pain sensation from traveling to CNS = stimulation by non-noxious input is able to suppress pain

*Increased nervous activity* leads to increased spillover of what into synapses

*Glutamate* --> triggers astrocytic *calcium wave* --> vasodilatory *prostaglandins* = *arterioles dilate*

Excitatory transmitter of A-delta pain fiber nerve ending

*Glutamate* = *pain transmission (Adelta & C fibers)*; excitatory NT (60% of brain synapses); involved in long-term potentiation of hippocampal neurons

Can be used to differentiate between lesion affecting 1st and 2nd order neuron from lesions affecting 3rd order neuron

*Hydroxyamphetamine* - causes *forced release* of NE from vesicles - 3rd neuron damaged --> no NE in vesicles at nerve ending --> pupil will not dilate following application of hydroxyamphetamine

Altered perception of pain such that stimuli which would normally induce a trivial discomfort causes significant pain

*Hyperalgesia* - often caused by damage to nociceptors or peripheral nerves - activation of pain receptors becomes progressively greater as pain stimulus continues - local tissue damage or local release of certain chemicals can lower threshold for activation of pain receptors & subsequent generation of pain signals

Brain structure that serves as major controller of limbic system

*Hypothalamus* - controls most of vegetative and endocrine functions of body and many aspects of behavior - major output source - communicates with brain stem nuclei through medial forebrain bundle --> conducts signals in 2 directions: toward brain stem and back to forebrain

CN for overall vision

*II* = SSA nerve that subserves *vision* & *pupillary light reflex*

Increase in what best describes the basis for transduction of sensory stimuli into nerve impulses?

*Increased ion permeability* - virtually all mechanical stimuli causes increase in ion permeability (usually to *sodium*) in mechanoreceptors

Analysis of visual detail occurs in what secondary visual area?

*Inferior ventral and medial regions of occipital and temporal cortex* - visual info from primary visual cortex (Brodmann's area 17) is relayed to Brodmann's area 18 More ventral pathway, from V-1 into adjacent V-2, & temporal association cortex carry X cell info necessary for analysis of visual details --> used to recognize textures, letters, & words with color of objects = *WHAT*

What structure carries axons from neurons in ventral posterolateral nuecleus of thalamus to primary somatosensory cortex?

*Internal capsule* - Dorsal column nuclei: axons of cells in cuneate & gracile nuclei form medial lemniscus --> crosses midline in caudal medulla as sensory decussation --> fiber bundle continues rostrally to thalamus --> axons terminate in ventrobasal complex via VPL --> axons of VPL neurons enter posterior limb of internal capsule --> project to primary somatosensory cortex (SI) in postcentral gyrus

Signals from the 2 eyes are kept apart in the

*LGN* - layers 2, 3, 5 receive input from ipsilateral eye - layers 1, 4, 6 receive input from contralateral eye Info from 2 eyes remains segregated in DLGN, as does input from X & Y retinal ganglion cells - DLGN = laminated structures that consists of 6 concentrically arranged layers - retinal axons that terminate in DLGN arise from contralateral nasal retina & ipsilateral temporal retina & thus carry point-to-point info from contralateral visual field

Where do Type C pain fibers teminate?

*Laminae II and III* --> 2nd neuron crosses immediately to opposite side & passes to brain in anterolateral columns: Type C fibers = slow pain = transmitted in paleospinothalamic tract; Substance P is excitatory transmitter of type C pain fiber nerve endings; poor localization of slow pain, often just affected limb or part of body

Mechanism of Gate theory of pain

*Lateral inhibition* of pain fiber by mechanosensory fiber - mechanism of action of: massage, liniments, electrical stimulation of skin - stimulation of type Abeta fibers can reduce pain transmission - *Audioanalgesia* can reduce pain & suffering during labor

What allows sodium entry into postsynaptic neuron?

*Ligand-gated* channels open to allow sodium...

Abnormal movements of Huntington's disease thought to be caused by

*Loss of GABA-secreting neurons in caudate nucleus and putamen* = appears in 4th or 5th decade of life = choreiform (flicking) movements at certain joints, severe dementia; perhaps also loss of ACh neurons in brain; short arm of chromosome 4 responsible

If person has head injury, rising ICP, rapid change in GCS, posturing, blow pupil, treatment should be

*Mannitol* = 1-2 g/kg - 100 g - normal BMI - give a bolus, not an infusion - otherwise, has reverse effect

What structures carry axons from nucleus gracilis to thalamus?

*Medial lemniscus* - carries axons from nucleus gracilis and cuneatus to thalamus - crosses midline in caudal medulla as sensory decussation --> continues rostrally to thalamus = axons terminate in ventrobasal complex, mainly ventral posterior lateral nucleus (VPL) --> axons of VPL neurons enter posterior limb of internal capsule & project to primary somatosensory cortex (SI) in postcentral gyrus

Elongated, encapsulated receptor found in dermal pegs of glabrous skin and especially abundant on lips and fingertips

*Meissner's corpuscle* = mediate fine discriminative tactile sensation via posterior column-medial lemniscus pathway = group II fibers = rapidly adapting

Inflammation of meninges causes severe headache...

*Meningitis* = pain involving entire head

What artery would have the most effect on the *entire* cortex?

*Middle cerebral artery* - most common place for cerebrovascular accidents - partial blood supply for every lobe of cerebral cortex

Symptoms of Horner's Syndrome

*Miosis* = constricted pupil Partial *ptosis* (droopy eyelid) - loss of sympathetic to superior tarsal muscle (Muller's muscle) - ipsilateral *decreased* facial sweating, *enophthalmos* (posterior displacement of eyeball in orbit, flushing of skin - *heterochromia* (children) = difference in eye color via lack of symp. stimulation interferes with melanin pigmentation - aortic dissection, carotid dissection (3rd order neurons), pancoast tumor, tuberculosis (lung apex, preganglionics)

Each of the principle types of sensation: touch, pain, sight, sound - is called a

*Modality of Sensation*: specificity of nerve fibers for transmitting only one modality of sensation is called the *labeled line principle* = sensory receptors are highly sensitive to one particular type of stimulus modality

Used to counter the effects of opiate overdose (heroin, morphine, etc.)

*Naloxone* = blocks opioids, especially in overdose

Type of cholinergic receptor found at synapses between preganglionic and postganglionic neurons of sympathetic system

*Nicotinic* - type of Acetylcholine receptor; located on postsynaptic nerve cells of both sympathetic & parasympathetic nervous sytems

Neurons in what area release serotonin as their neurotransmitter?

*Nucleus raphe* - endogenous pain suppression system: termination of these neurons in spinal cord on interneurons --> release enkephalin --> block incoming signals from pain fibers

Middle ear sclerosis

*Otosclerosis* - air conduction low - bone transduction inhibited - most commonly, stapes becomes stuck in place causes - measles infection - stress fractures to bone surrounding middle ear - immune disorders - tends to run in families

The peripheral sensory input that activates the ascending excitatory elements of the reticular formation comes mainly from

*Pain signals* - pain signals traveling through the ALS Activity in Paleospinothalamic system may impart unpleasant perception of pain: axons of lamina V cross midline near level of origin --> ascend in ALS --> axons terminate in brain stem = reach *reticular formation*, superior colliculus, & periaqueductal gray --> fibers proceed rostrally to intralaminar nuclei & posterior nuclei of thalamus --> *pain signals transmitted over pathway & localized only to major part of body*

Responsible for *poor localization* of slow pain, often to just the affected limb or part of body

*Paleospinothalamic* tract: Slow, burning pain via C fiber

Group of neurons in the pain suppression pathway that uses enkephalin as neurotransmitter

*Periaqueductal gray area*: periaqueductal gray & nucleus raphe magnus have opiate receptors on surface membranes --> stimulated by exogenously administered opioid compounds or *enkephalins* found in brain --> pain suppression circuity activated = reduced pain perception

What cell group is considered the punishment center?

*Periventricular hypothalamus and Midbrain central gray area* - areas that, when stimulated, evoke aversive behavior = midbrain periaqueductal gray, periventricular zones of thalamus & hypothalamus, amygdala, hippocampus

Drugs that are sympathomimetic drugs

*Phenylephrine* (alpha receptors), Isoproterenol (beta1 & beta2 receptors), albuterol (beta2) --> act on adrenergic effector organs

Why do Albinos have decreased visual acuity?

*Photophobia* - abnormal tolerance to visual perception of light - discomfort or pain to eyes due to light exposure - lack of retinal pigment epithelium = increased scattering of light in eyeball - not enough pigment in iris to block light *Increased decussation of temporal fibers* - 20% of temporal fibers decussate at optic chiasm and project to contralateral dorsal LGN rather than ipsilateral nucleus

Enhanced responsiveness following repetitive stimulation

*Post-tetanic facilitation* = build-up on calcium ions in pre-synaptic terminals --> causes more vesicular release of transmitter - subsequent activation of synapse may require less current & produce enhanced response - when repetitive (tetanic) stimulation applied to excitatory synapse followed by brief period of rest

What molecules move from the endolymph into the sterocilia and depolarize the hair cell?

*Potassium* ions - although most cells in nervous system depolarize in response to sodium entry, hair cells are one group of cells that depolarize in response to potassium ions - When *stereocilia* are bent toward kinocilium, *potassium* channels in cilial membrane are opened --> *potassium* from scala media fluid enters --> hair cell depolarized

Voluntary fixation of eye movement controlled by area in

*Premotor cortex* - *frontal eye fields (Brodmann's area 8) & area in occipital lobe (portion of secondary visual cortex (area 19)* - involuntary fixation mechanism causes eye to "lock" on object of attention found within voluntary fixation mechanism

Nuclei for pupillary light reflex & *accomodation of lens*

*Pretectal nuclei* --> activate pupillary light reflex

Fine motor movement of index finger can be elicited by stimulation of what brain area?

*Primary motor cortex* (in precentral gyrus / Brodman's area 4): area related to control of *fine movements of hand* located in *premotor cortex* just anterior to hand region of area 4 --> damaged = muscles of hand are not paralyzed, but certain movements are lost = *motor apraxia*

Fine motor movement of index finger can be elicited by stimulation of what brain area?

*Primary motor cortex* - are related to control of *fine movements of hand* located in premotor cortex just anterior to hand region of area 4 --> damaged = either paralyzed ore certain hand movements lost = *motor apraxia*

Probably important for determining *quality* of pain

*Primary somatosensory (SI) Cortex* - used primary during localization of painful stimuli

Glaucoma eye drops that: - increase outflow of fluid from eye

*Prostaglandin analogs* - change in iris color and growth of eyelashes = side effects

Enhances sensitivity of pain receptors but does not directly excite them

*Prostaglandins* & substance P

Serve as alternative pathway for signals from motor cortex to spinal cord

*Red nucleus* - control flexor muscles through rubrospinal tract Projections to *red nucleus* may provide alternate pathway for motor cortex to influence spinal cord via rubrospinal tract if corticospinal axons are damaged at a level caudal to red nucleus

Stimulation of what subcortical area can lead to contraction of single muscle or small groups of muscles?

*Red nucleus* - magnocellular portion = somatographic representation of all muscles of body, similar to motor cortex

- middle ear fluid, not infection - can occur via infection - poor eustachian tube function - dampens hearing but not painful - pediatrics mainly - 3 months or longer? --> drain fluid --> tubes! - need to do in children early for proper language progression - *chronic*

*Serous otitis media* (SOM) / Otitis media with effusion (OME) / Secretory otitis media = collection of non-infected fluid in middle ear space: may accumulate in middle ear as result of cold, sore throat, or upper respiratory infection

What cells in layer IV of the primary visual cortex detect orientation of lines and borders?

*Simple cells* - complex cells detect lines oriented in same direction but are not position specific - neurons in layer *IV of V1* = simple cells = maximally responsive to lines or edges that are aligned in *preferred orientation*

Push in needle --> push further = stimulation of different points...what is this?

*Spatial summation* = gradations or stimulus intensity signaled by involving variable number of "parallel" fibers in same nerve = 2 or more presynaptic axon terminals activated simultaneously = enables combined EPSPs to exceed threshold value for AP

Gradations in *signal intensity* can be achieved by:

*Spatial* summation - increased number of fibers stimulated *Temporal* summation - increasing rate of firing in given number of fibers

Preganglionic parasympathetic neurons that contribute to the innervation of the descending colon and rectum are found in what structure?

*Spinal cord levels S2 and S3*: Sacral parasympathetics innervate distal half of large intestine via pelvic nerves; sigmoidal, rectal, & anal regions have rich supply of parasympathetic fibers that function in defecation reflexes

3 major levels of CNS function

*Spinal cord* *Lower brain* - medulla, pons, mesencephalon, hypothalamus, thalamus, cerebellum, basal ganglia *Higher brain or cortical level*

Thought to mediate *lower back pain, arthritis, fibromyalgia*

*Substance P*

Excitatory transmitter of type C pain fiber nerve ending

*Substance P* & prostaglandins enhance sensitivity of pain receptors but do not directly excite them

67-year-old man has stroke. One week later, he experiences sudden and uncontrolled flailing, ballistic movements of his limbs. What part of the man's brain is most likely to have been damaged by the stroke?

*Subthalamic nucleus* of basal ganglia - Subthalamic lesions can cause flailing movements of an extremity, called *hemiballismus* - stroke = most common cause of hemiballismus in adults (rare) - Basal ganglia = caudate nucleus, putamen, globus pallidus, substantia nigra, *subthalamic nucleus*

What brain structure plays a major role in determining the direction from which a sound originates?

*Superior olivary nucleus* - receives auditory info from both ears and begins process of detecting direction form which a sound comes - primary sensory fibers from spiral ganglion --> brain stem --> terminate in dorsal & ventral cochlear nuclei --> sent to contralateral (& ipsilateral) *superior olivary nucleus* --> give rise to nerve fibers that enter lateral lemniscus --> terminates in inferior colliculus --> cells project to medial geniculate nucleus of thalamus --> signals transmitted to primary auditory cortex: transverse temporal gyrus of Heschl

Capsaicin selectively binds to

*TRPVI* / transient receptor potential cation channel subfamily, member 1 / capsaicin receptor - resides on membranes of pain & heat sensing neurons

Lies above stereocilia of hair cells

*Tectorial membrane* - stereocilia shear against tectorial membrane - apical surface of hair cells give rise to many stereocilia & a single kinocilium that project upward into overlying *tectorial membrane* --> basilar membrane vibrates = hair cilia embedded in tectorial membrane bent in one direction & then in the other direction --> movement mechanically opens ion channels = depolarization or hyperpolarization of hair cell, depending on direction of bending

Structural basis of blood-CSF barrier

*Tight junctions between adjacent choroid plexus cells* - endothelial cells of capillaries joined to one another

Unmyelinated free nerve endings fiber type

*Type C* = conduct at slow velocities

Condition of prosopagnosia usually results form dysfunction or damage to what area of the cereberal cortex?

*Underside of medial occipital and temporal lobes* (occipitotemporal) - Prosopagnosia = inability to recognize faces

Low CO2 has what affect on blood vessels?

*Vasospasm* - hyperventilate briefly - lower than 30 = vasoconstriction zone

What does Meniere's disease involve other than cochlea?

*Vestibular labyrinth* *lateral semicircular canals* = *lateral canal hydrops* - sensory organs for vestibular sense located in system of bony chambers in petrous portion of temporal bone --> each bone enclosure houses membranous chamber of tubular structure that contains the sensory hair cells & terminal ends of primary sensory fibers of 8th CN that leads into brain --> membranous structures include 3 semicircular canals or ducts & 2 larger chambers (utricle & saccule)

Why does highly localized organ damage cause little pain?

*Visceral* tissues have *few pain fibers* - widespread damage can cause severe pain

An area in the dominant hemisphere, when damaged, may leave sense of hearing intact but not allow words to be arranged into *comprehensive thought.*

*Wernicke's area* = area for language comprehension = superior temporal gyrus

Parvocellular path gets input from

*X type ganglion cells* (XP) - transmit color info - accurate point-to-point transmission

Magnocellular pathway (small percentage) gets input from

*Y* type ganglion cells (MY) - rapid changes in *black and white* - no color info - poor point-to-point transmission via limited number of Y cells Y cell input terminates in layers 1 & 2 = termed *magnocellular* because they contain large neurons Rapidly conducting pathway is color blind by carries effective localizing info

Glaucoma eye drops that: - decrease fluid production of fluid and increase drainage

*alpha agonists* --> if drug therapy fails, surgical procedures performed to open trabecular spaces or to drain trabecular meshwork directly into subconjunctival spaces outside the eyeball

Light rays bend when passing through

*angulated interface with different refractive index*: when light wave passes through angulated surface, it is bent/refracted at some angle if the refractive indices of 2 media are different; degree of refraction depends upon the refractive index of the barrier angle & the angle at which light strikes it

2 fluid chambers of eye

*aqueous humor* - in front of lens (free flowing fluid) *vitreous humor* - behind lens (gelatinous mass with little fluid flow)

Primary visual cortex lies in

*calcarine fissure/sulcus*: primary visual cortex/Brodmann's area 17/V1 = on medial surface of hemisphere lining both walls of calcarine sulcus near occipital pole

Intraocular fluid produced by

*ciliary body* at rate of 2-3 microliters/min

Postganglionic fibers of Edinger-Westphal nucleus send fibers through

*ciliary nerves* - control: ciliary muscle (lens focusing), sphincter of iris (constricts pupil) Parasympathetic fibers to eye originate in Edinger-Westphal nucleus & course via oculomotor nerve to *ciliary ganglion*, where postganglionic fibers originate & extend to eye via ciliary nerve

Rate of adaptation: Ruffini endings

*continuous/slow* - MR slow

Majority of neurons from cochlear nuclei synapse in

*contralateral (and ipsilateral) superior olivary nucleus* --> give rise to nerve fibers that enter lateral lemniscus --> terminates in inferior colliculus --> project to medial lemniscus of thalamus --> transmitted to primary auditory cortex / transverse temporal gyrus of Heschl

LGN receives gating control signals from

*corticofugal fibers* - originating in primary visual cortex - efferents / descending *reticular areas* of midbrain Both inputs are *inhibitory* --> can turn off signal transmission in select areas of LGN

Pain occurs whenever tissue is being

*damaged* - protective mechanism - causes ind. to remove painful stimulus - Slow pain associated with *tissue damage* = perceived as burning, aching, or chronic pain - fast pain felt within 0.1 second after painful stimulus; slow pain begins 1 second or more after painful stimulus

Prolonged activation of neurons by capsaicin...

*depletes presynaptic substance P* --> releives pain Capsaicin in over-the-counter creams = made from chilli peppers - selectively binds to *TRPVI* / capsaicin receptor - heat activated calcium channel that resides on membranes of pain & heat sensing neurons Substance P: mediates lower back pain, arthritis, fibromyalgia

Degree of refraction increases as

*difference in R.I. increases* --> degree of angulation increases (lens with higher refractive power causes greater bending of light rays)

Areas with most and least cold receptors

*highest on lips* (15 to 25 receptors per cm^2) *lowest on trunk* - small nerve ending - tips protrude into basal aspect of basal epidermal cells - signals transmitted via type Adelta sensory fibers - 3-10 times as many cold receptors as warmth receptor

Where are beta-endorphins found?

*hypothalamus and pituitary* - major endogenous opiates - derived from POMC (precursor of ACTH) - beta-endorphin = major endorphin found in brain Endorphinergic neurons found almost exclusively in *hypothalamus* (arcuate & pre-mamillary nuceli) --> project to hypothalamus, amygdala, nucleus accumbens, septal area, thalamus, locus ceruleus (midbrain, pons)

Causes of ischemic pain

*lactic acid buildup* *bradykinin* proteolytic enzymes Ischemia via insufficient blood flow

Superior olivary nucleus is divided into

*lateral* nucleus - detects direction by *difference in sound intensities between 2 ears* *medial* nucleus - detects direction by *time lag between acoustic signals entering ears*

CBF controlled by

*metabolic factors* - *CO2, H+, O2*, substances from astrocytes - any substance that increases acidity of brain = increased cerebral blood flowdecrease in cerebral tissue PO2 = increased cerebral blood flow via vasodilation of cerebral blood vessels

Minimum and Max. Glasglow Score

*min = 3* (deep unconsciousness) *max = 15* Glasgow Coma Scale (GCS) = records conscious state of person - assesses level of consciousness after head injury

Rate of adaptation: Pacinian corpuscle

*most rapidly adapting* = 30-800 cycles/sec --> linked to large, rapidly conducting myelinating fibers (Type Abeta)

Type of neuron: *motor neuron* of spinal cord

*multipolar*

What receptors are considered slowly adapting (tonic) receptors?

*muscle spindle* *golgi tendon apparatus* ruffini endings merkel discs *macula* *pain* *temperature* *chemo- & baroreceptors* - keep brain apprised of status of body with respect to its surroundings - will adapt to extinction as long as stimulus is present but may take hours or days

Fast pain (first pain) transmitted in

*neospinothalamic tract* - fast pain signal transmitted via Adelta fibers = 6-30 m/sec = excite neurons primarily in lamina I of dorsal horn --> ascend white matter of spinal cord as part of ALS --> some terminate in brain stem reticular formation but most project all the way to VPL nucleus of thalamus --> SI cortex

90% of glaucoma cases are caused by

*open angle glaucoma / chronic glaucoma* - insidious / no pain initially - reduced flow through trabecular meshwork (tissue debris, WBC, deposition of fibrous material)

Function/stimuli of *Myelinated* free nerve endings

*pain, temperature* - type Adelta nerve fibers - conduct at slow velocities = tactile receptors

Behavioral deficits, changes in personality, and diminished problem-solving ability are all signs of damage to the

*prefrontal association cortex*: prefrontal cortex = site of "working memory" = ability to hold & sort bits of info to be used in problem-soliving function; intellectual functions of the highest order

Important for controlling all *antagonistic pairs* of muscles

*reciprocal inhibition circuit* - important in preventing over-activity in brain

Level of pressure of intraocular pressure determined by

*resistance* to outflow of aqueous humor in *canal of schlemm*

Most Type C fibers terminate in

*reticular nuclei* of medulla, pons, and mesencephalon; tectal area of mesencephalon; *periaqueductal gray region* - only 10-25% of fibers terminate in thalamus

High stimulus causes what type of receptor potential response?

*small* (small stimulus cause big response)

In controlling the fine muscles of the hands and fingers, corticospinal axons can synapse primarily with

*spinal cord motor neurons* - majority of corticospinal axons synapse with pool of *spinal cord interneurons*, but some will synapse directly with motor neurons that innervate muscles controlling wrist and finger flexors

Accounts for 50% of adaptation of taste sensations

*taste buds* - central adaptation must occur but mechanism unknown Adaptation to taste occurs at receptor level, but most taste adaptation occurs through central mechanisms

Where is adenosine highest on a cerebral blood flow vs. mean arterial blood pressure graph?

*to the left of 100 mmHg* - blood vessels dilate because need to increase blood flow

Secondary visual ares are

*visual association areas* - where visual image is dissected and analyzed

Input neuron to diverging circuit causes membrane potential of target neuron to change from -65 mV to -55 mV. What is the EPSP?

+10 mV membrane potential - epsp's always + - ipsp's always -

Potential of Scala media

+80mV

Visual signal in *primary visual cortex* concerned mainly with

- *contrast* in visual scene (greater sharpness of contrast = greater stimulation) - direction of *orientation of each line and border* (each orientation of line = specific neuronal cell stimulated) - color constancy: changing color of light that illuminates a scene does not substantially alter hues of color in scene Primary visual cortex = Brodmann's area 17 = V-1

Mechanism of fatigue

- *transmitter depletion* - receptor inactivation - *accumulation of calcium ions* in synaptic bouton & exhaustion of NT supply - how *epileptic seizures stop*

Anterolateral system

- contains *smaller* myelinated & unmyelinated fibers for *slow* transmission (0.5 - 40 m/sec) - 3 neurons to sensory cortex/decussates in spinal cord - low degree of spatial orientation - transmits broad spectrum of modalities - *pain, thermal sensations, crude touch and pressure, tickle and itch, sexual sensations*

Atropine

- dilates puil (mydriasis) - inhibits accomodation - blocks parasympathetic effects = competitive antagonist for muscarinic ACh receptors - extracted from plant (*atropa belladonna*) - used by Egyptians & Europe - blocks vagus = increased heart rate = antimuscarininc

Characteristics of local potentials

- do no induce refractoriness - graded: bigger stimulus = bigger response - summate: multiple stimuli = summed response

Dorsal Column-medial lemniscal system

- large myelinated nerve fibers (30-110 m/sec) - 3 neurons to sensory cortex/*decussates in medulla oblongata* - high degree of *spatial orientation* maintained throughout tract - transmits info rapidly & with high degree of spatial fidelity (discrete types of mechanoreceptor info) - *transmits touch, vibration, position, fine pressure*

Resting potential of hair cell

-50 mV depolarization & repolarization of hair cells is mediated by K+

At what decibel can most people barely hear sound?

0

Each terminal on the dendrite account for how much of an EPSP?

0.5 - 1 mV

Pathophysiology of Noise-induced hearing loss

1 = decreased *stiffness* of stereocilia of *inner* hair cells 2 = loss of stereocilia 3 = loss of entire hair cells (via phagocytosis) - via cochlear inflammatory response / *reactive oxygen species* - treatment = *antioxidants*, cold water can protect cochlea after dizzy spell

Lens system focused on distant object can refocus on close object in less than

1 s

Brodmann's areas of Somatosensory area 1

1, 2, 3 - primary somatosensory area

Increased H+ concentration in brain can lead to

1. *Increased blood flow* 2. Decreased neuronal activity

2 principle functions of LGN

1. *Relay* info to primary visual cortex via optic radiation 2. *Gate control* of info to primary visual cortex

Classic Triad of symptoms in Meniere's Disease

1. Episodic vertigo 2. Fluctuating sensorineural hearing loss 3. Tinnitus and ear fullness *cochlear hydrops* = Reissner's membrane distorted throughout cochlea

1 decibel is an increase in sound energy of

1.26 times

Polycarbonate R.I.

1.58

Average life of taste bud

10 days

Physiology experiment conduct in which glass microelectrode is inserted into Pacinian corpuscle to record receptor potential during different levels of stimulation (from 0 to 100%). Increasing stimulus strength from 10% of max to 30% of max causes a 40% increase in amplitude of receptor potential. Increasing the stimulus potential from 70% of max to 90% of max is most likely to cause what increase in the amplitude of receptor potential (in %)?

10% - Amplitude of receptor potential from Pacinian corpuscle increases in stimulus intensity at lower levels of stimulus strength - Pacinian corpuscle discerns small changes in stimulus strength at low levels of stimulation & yet still responds to changes in stimulus strength when intensity of stimulation is high

Humans have a fixed angle of

104 degrees - our eyes are close together = visual fields overlap = allows accurate judgment of distance

How many possible chemical receptors in taste buds

13 - 2 for sodium - 2 for potassium - chloride - adenosine - inosine - 2 sweet - 2 bitter - glutamate - hydrogen ion

Power of accommodation - child: - 50 years old: - 70 years old:

14 diopters 2 diopters 0 diopters

What % of resting cardiac output is CBF?

15% - only 2% of body weight - high metabolic rate

Arterial occlusion of limb causes pain in what time frame?

15-20 s

Volume: CSF

150 mL

Fixed volume of cranium

1500-1600 mL

Volume: cranial vault

1600 mL

How far is retina behind refractive center of eye?

17 mm - so: eye has total refractive power of 59 diopters (1000/17)

Measures minimum distance at which 2 stimuli are resolved as distinct

2-pt discrimination - reflects how finely innervated an area of skin is

Visual perception is thought to be mediated by

3 parallel pathways that process info on motion, depth and form, and color

Interruption of brain blood flow for how long can lead to unconsciousness?

3 to 7 seconds - sleeper hold! - brain highly dependent on oxygen

How many taste buds does the human tongue have?

3,000 - 10,000

Speed of light in air

300,000 km/sec

Refractive power can be increased by how much?

34 diopters - by making lens thicker = *accomodation* = necessary to focus image on retina via parasympathetics

Cerebral blood flow supplied by

4 arteries - internal carotid - vertebral Circle of Willis

Analgesic effects mediated through

4 brainstem sites - para-brachial nucleus - medullary reticular formation - Raphe nuclei - Locus coeruleus

Hearing loss at what Hz?

4,000 - damage to cilia of *outer hair cells* first

Light shining in eyes (of cat) for 30 minutes causes

40% increase in occipital blood flow

Brodmann's areas of Somatosensory association area

5, 7 in parietal area - receives input from somatosensory cortex, ventrobasal nuclei of thalamus, visual and auditory cortex - deciphers complex sensory associations

What length of cessation of blood flow to brain will result in loss of consciousness?

5-10 s

How much CSF is formed each day?

500 mL - mainly by choroid plexus in lateral ventricles

Total refractive power of eye

59 - (1000 / 17) - 17 = distance retina is behind refractive center of eye

Know general structure of Cerebral Cortex

6 separate layers of neurons: I near surface, VI deep within cortex - incoming signals enter layer IV --> spread both up & down - layers I and II receive diffuse input from lower brain centers - II & III send axons to closely related portions of cortex - V & VI send axons to more distal parts of nervous system: layer V to brainstem & spinal cord, VI to thalamus

CBF is autoregulated extremely well over a pressure range of

60 mmHg to 140 mmHg - above 160 mmHg = blood flow increases with increasing pressure; blood vessels begin to stretch --> damage and eventual rupture (stroke) - can lower pressure to 60 before see substantial decrease in cerebral blood flow

What pH can induce a coma?

7.4 change to *7.0*

What pH change can induce seizures?

7.4 change to *8.0*

At what Glasgow score should one think about intubating?

8 - can't protect their aiway - lethargic, confused, altered mental status --> salivary problems

What can produce effective pain relief for up to 12 weeks in patients with neuropathic pain?

8% capsaicin patch applied to skin for 60 minutes in patients

Excitatory post synaptic potential (epsp)

= *isoelectric response* = decays with exponential time course - last epsp may be larger because it occurs before previous epsp is fully decayed (slide 25) = positive local potential = summated over time & space - spatial summation enables combined EPSPs to exceed threshold value for AP

Diopter

= measure of power of lens 1 diopter = ability to focus parallel light rays at distance of 1 meter

Accommodation: contraction of ciliary muscle is likely to

= thicker lens and relaxation of suspensory ligament

1st order = posterior root ganglion 2nd order = spinal cord laminae 1-5 3rd order = thalamus (VPL) 4th order = primary somatosensory cortex (body) - non-discriminative touch = 1 - pain = 5

ALS order neurons

Afferent axon type:Touch

Abeta - merkel, meissner, pacinian, ruffini cells - largish axon diameter

Meissner corpuscles fiber type

Abeta nerve fibers

Merkel discs fiber type

Abeta nerve fibers

Ruffini corpuscle nerve fiber type

Abeta nerve fibers

Type of seizure associated with spike and dome electroencephalogram pattern during seizure activity

Absence

Often accompanied by microtia (small external ear)

Absence of External Auditory Canal - replaced by bone - CN VII has abnormal course

Gigantocellular neurons of the reticular formation release what NT?

Acetylcholine - reside in pons & mesencephalon

What pH *depresses neuronal activity*?

Acidosis - diabetic coma - pH from 7.4 to 7 will induce coma

- Arises on vestibular nerves - Schwannoma that arises from lining over nerve

Acoustic neuroma

- independent of stimulus strength = all or non - propagation unchanged in magnitude - summation not possible

Action Potential

40-year-old woman is admitted emergently to the hospital because of sudden, severe pain in her right eye. Tests show an intraocular pressure of 30 mmHg in her right eye; the intraocular pressure of her left eye is 15 mmHg. What is the most likely cause of eye pain in this woman?

Acute angle-closure glaucoma - Sudden closure iridocorneal angle prevents aqueous humor from reaching its outflow pathway in canal of Schlemm

- common in children - variability - increased vascularity - edema posteriorly = early sign

Acute otitis media

Disorientation of skins sensation across its space (hard to identify number of letter traced on hand)

Agraphesthesia

Determined by how much the basilar membrane is displaced

Amplitude

Blood supply of Frontal lobe

Anterior cerebral artery Middle cerebral artery - higher mental functions

Blood supply of Parietal lobe

Anterior cerebral artery Middle cerebral artery - sensory info from different modalities

Two pathways for sensory afferents

Anterolateral system - lateral root Dorsal column-medial lemniscal system (PCML) - medial root

The intraocular fluid of the eye flows from the canal of Schlemm into what location?

Aqueous veins - flows from anterior chamber of eye --> between cornea and iris through a meshwork of trabeculae into canal of Schlemm --> empties into extraocular aqueous veins

Occlusion of what structure would lead to communicating hydrocephalus?

Arachnoid villi - blockage either within subarachnoid space or at arachnoid villi --> prevents communication between subarachnoid space and superior sagittal sinus

Why do individuals in severe pain have difficulty sleeping with sedative medication?

Ascending pain pathways provide input to reticular formatino elements that comprise reticular activating system

Unequal focusing on light rays due to oblong shape of cornea

Astigmatism

Can reduce pain and suffering during labor

Audioanalgesia

Perceptual disturbance that occurs in a small % of migraine headache victims

Aura - precedes or occurs along with headache - often manifests as strange light, unpleasant smell, or confusing thoughts *Increased risk of ischemic stroke in those who have migraine with aura*

- Inflammatory --> can block ear canal - Caused by infection - Treatment = systemic & topical antibiotic or steroids

Aural polyp

Contains ~30,000 fibers which project from bony center of the cochlea, the modiolus

Basilar membrane

Signals form motor areas of the cortex reach the contralateral cerebellum after first passing through what structure?

Basilar pontine nuclei - main pathway linking cerebral cortex and cerebellum involves cortical projections to ipsilateral basilar pontine nuclei --> cells project to contralateral cerebellum

Glaucoma eye drops that: - decrease production of fluid

Beta blockers

Olfactory receptor cells belong to what group of cells?

Bipolar neurons

What taste sensation is most sensitive (has the lowest stimulation threshold)?

Bitter - protective function against many dangerous toxins in food

Causes an *internal release of Ca2+* & is more sensitive on molar basis compared to other taste sensations

Bitter taste

How should mannitol be administered?

Bolus - not infusion: will give reverse effect otherwise

Main cause of pain resulting from tissue damage (slow pain)

Bradykinin - also *potassium* & *proteolytic enzymes* contribute

Has ~2 min supply of glucose

Brain = glycogen in neurons

Ipsilateral symptoms: loss of motor function (hemiparaplegia), vibration sense, fine touch proprioception (position sense), two-point discrimination, and weakness Contralateral symptoms: loss of pain, temperature sensation, and crude touch

Brown-Sequard syndrome

Formula for Compliance

C = V/P (Vermont / Pennsylvania)

How does increased arterial CO2 cause vasodilation?

CO2 diffuses into brain tissue --> raises H+ ion concentration --> *H+ ions cause vasodilation* Increased H+ in brain = increased blood flow, decreased neuronal activity

Primary sensations of smell

Camphoraceous Musky Floral Pepperminty Ethereal Pungent Putrid As many as 100 smell sensations have been reported, but they have been narrowed to *7* primary odor sensations

Glaucoma eye drops that: decrease production of intraocular fluid

Carbonic anhydrase inhibitors (CAIs)

Projection system contained in superior cerebellar peduncle

Cerebellothalamic

Portions of cerebellum function in planning of sequential movement

Cerebrocerebellum and dentate nucleus

The sweat glands and piloerector muscles of hairy skin are innervated by what type of fibers?

Cholinergic postganglionic sympathetic

What space that lies outside the brain or spinal cord contains CSF?

Cisterna magna

Composition of CSF

Clear, colorless, similar to plasma - Na+ slightly less than plasma - Cl- = 15% higher than plasma - K+ = 40% of plasma - Glucose = 30% of plasma - plasma proteins = LOW = 1-2% of plasma Cl- = only molecules higher in CSF than plasma

10% of Glaucoma cases are caused by

Closed angle glaucoma - sudden closure of iridocorneal angle with sudden ocular pain

Where is the highest frequency in the basilar membrane?

Closes to stapes = short and stiff = closes to *base*

Used to target beam directly on tumor

Cobalt Radiation - sterotactic radiation - gamma knife: intracranial lesions - frame during imaging --> MRI scan - try to cover tumor with multiple shots

Current increases causes increased loudness

Cochlear Implant - electrode stimulation in different cochlear locations --> different pitches - tonotopic distribution of 8th nerve used: basal = high pitched, apical stimulation = low pitched sound - uses *coding* = natural sounding, pleasant sounding, max info to cochlea

In the central auditory pathway, what represents the correct sequence of structures in the pathway?

Cochlear nuclei - superior olive - inferior colliculus via lateral lemniscus - medial geniculate - auditory cortex

The condition of myopia is usually corrected by what type of lens?

Concave lens - myopia = focal point of lens system of eye is in front of retina --> concave lens will diverge light rays --> divergence of light rays will move focal point from in front of retina to position on retina

Impairment of tympanic membrane or ossicles

Conduction deafness - tumor in auditory canal - wax buildup

ANS uses what type of info transmission to control vascular tone, gut tone, heart rate?

Continuous output from *reverberating circuit* - can be *enhanced or suppressed* - not all reverberatory circuit fatigue

Functional role of cerebellar vermis

Controls and coordinates movements of *axial muscles*, as well as shoulder and hip

Allows summation of info from multiple sources

Convergence from *multiple separate sources* - correlates, summates, and sorts info

Boy sustains serious head and neck trauma. Physical exam shows positive Babinski sign. What part of the brain has most likely been damaged in this boy?

Corticospinal tract - positive Babinski sign occurs normally in children up to 2 years of age. - positive Babinski sign in adults = damage to corticospinal tract

What maneuver will attenuate the stretch reflex in skeletal muscle?

Creating a lesion in the contralateral *globus pallidus*: signals initiated in premotor cortex & supplementary cortex are transmitted to putamen & then onto globus pallidus; globus pallidus lesions cause writhing movements of hand & are or face = *athetosis*; Motor deficits seen in Parkinson's disease via abnormal signals transmitted from globus pallidus to thalamus

What would lead to vasodilation of systemic arterioles?

Decreased activity of postganglionic sympathetic neurons

Girl with fever is hyperventilating. What is most likely to occur in this girl?

Decreased brain oxygenation Increased neuronal activity - alkalinity increases neuronal activity in the brain - CO2 increases cerebral blood flow

What best describes the permeability to sodium and potassium in rod cells in response to light?

Decreased sodium permeability *No change in potassium permeability* - activated rhodopsin (metarhodopsin II) --> activates transducin in outer segment disc membrane --> activates phosphodiesterase --> hydrolyzes cGMP --> loss of cGMP closes cGMP-gated sodium channels --> decreases sodium permeability --> more negative (hyperpolarized) membrane potential - no change in potassium

Area of skin supplied by sensory neurons that arise from spinal nerve ganglion

Dermatome

Location of Ruffini corpuscle

Dermis

*Place principle* - different frequencies of sound cause basilar membrane to oscillate at different position

Determines the frequency of sound perceived

Signal amplification is achieved via

Diverging - amplification = type of divergence - ex. single pyramidal cell in motor cortex can stimulate 10,000 muscle fibers

Afferent signals from periphery of body travel to cerebellum in what nerve tract?

Dorsal and Ventral spinocerebellar

System that transmits somatosensory info with highest degree of temporal and spatial fidelity

Dorsal column-lemniscal system

Olfactory info transmitted to orbitofrontal cortex passes through what thalamic nucleus?

Dorsomedial

Because of the dual pathway of fast and slow pain, what occurs?

Double sensation of pain - sharp pain followed seconds later by slow pain

Cerebellar deficit in which there is failure to perform rapid alternating movements indicating failure of "progression" from one part of movement to the next

Dysdiadochokinesia - movements that include rapid alternation between flexion and extension are most severely affected

Why is 1 pre-synaptic neuron not enough for an AP induction?

EPSP too small to reach threshold

Parasympathetic preganglionic fibers of CN III arise from

Edinger-Wesphal nucleus --> synapse with *postganglionic* fibers in ciliary ganglion

Good source of choline

Eggs Choline... - must eat it for *ACh* - essential nutrient - discovered in 1998 - NT synthesis, cell structure

Subthreshold potential change

Electrotonic - proportional to stimulus strength (graded) - not propagated but decremental with distance - exchibits summation

Muscular tension / Tension headache...

Emotional tension may cause tension of muscles attached to neck and scalp --> causes irritation of scalp and coverings

Can cause both presynaptic and postsynaptic inhibition of incoming type C and type Adelta pain fibers where they synapse in dorsal horn

Enkephalin (opioid peptide)

Receptive field of Pacinian corpuscle

Entire finger of hand

Substance that activates adrenergic alpha and beta receptors equally well?

Epinephrine

Bilateral lesions involving ventromedial hypothalamus will lead to what deficits?

Excessive eating Rage and aggression Hyperactivity *Ventromedial nucleus = satiety center = inhibits urge to eat*

Input neuron to diverging circuit causes membrane potential of target neuron to change from -65 mV to -55 mV. What best describes this change in membrane potential (in mV)?

Excitatory postsynaptic potential = +10 - positive increase in membrane potential to less negative values = EPSP = always +

- Whitish growth = rock hard = bone - Common in Hawaii & CA via repeated exposure to cold water: surfers - Exposure of bone to cold: bone immediately under layer of epithelium - NOT tumor, benign

Exostosis

Body part represented most laterally and *inferiorly* within primary motor cortex

Face - territory of *middle cerebral artery*

Length of eye ball in Hyperopia

Far-sightedness = *short eyeball* - contraction of ciliary muscle increases strength of lens (reduces focal distance) - far-sighted person can focus near object on retina because of *accommodation* - corrected with *convex lens*

Two types of pain

Fast pain - body surface/first pain - Adelta fibers - 0.1 s after stimulus - sharp pain - not felt in deeper tissues Slow pain - body surface and deeper tissues - C / unmyelinated fibers - 1 s or more - throbbing or aching pain - tissue destruction (*bradykinin*)

Protective mechanism against excess neuronal activity

Fatigue

Exhaustion of stores of transmitter in synaptic terminals

Fatigue - excitatory synapses repetitively stimulated at rapid rate until postsynaptic discharge becomes progressively less - causes areas of nervous system to lose excitability after a while = protective mechanism against excess neuronal activity

Central Auditory Pathway...

Fibers enter dorsal & ventral cochlear nuclei of upper part of medulla --> 2nd order neurons project through *trapezoid body* to *contralateral superior olivary nucleus* --> some fibers pass to ipsilateral superior olivary nucleus --> lateral lemniscus = superior --> inferior colliculus --> inferior colliculus --> medial geniculate --> medial geniculate --> auditory cortex

What type of papillae is located in the folds along the lateral surfaces of the tongue?

Foliate

Structure that connect hippocampus to limbic system

Fornix - connects hippocampus to anterior thalamus, hypothalamus, and limbic system

What has 100x more representation in cortex compared to peripheral portions of retina?

Fovea

Sensory receptors responsible for pain, crude touch

Free nerve endings

50% of all hereditary ataxias contributed to

Friedreich's ataxia - nerve degeneration

Excitatory of inhibitory effect of postganglionic sympathetic fiber is determined by what feature?

Function of postsynaptic receptor which it binds

Prolonged changes in neuronal activity usually achieved through activation of

G protein-coupled chanels

Binding of chemical odorant to receptor induces

G-protein transduced formation of cAMP --> opens sodium channels --> depolarization - *odorant-binding receptors* located on cilia

Up to 50% nonsyndromic HL caused by

GJB2 (Gap Junction beta 2) locus on chromosome 13q11 - small (680 base pair) gene encodes Connexin 26 protein - expressed in cochlea and epidermis - hexamers form channels to recycle K+

In what type of neuron does the axon form synaptic junctions with skeletal muscle cells (intrafusal fibers)?

Gamma motor neuron

Damage to optic nerve usually caused by high intraocular pressure (IOP)

Glaucoma

What substance is responsible for the umami taste sensation?

Glutamate

Sensory receptor most likely to mediate relaxation of muscles when tension is increased

Golgi tendon

Highest blood flow is found in what matter of brain?

Gray matter - more blood vessels, mitochondria, ATP production

Receptor organs that generate APs in response to sound vibrations

Hair cells - modulate how much input hair cells are exposed to

Irritation of meninges by alcohol breakdown products and additives

Hangover

Example of local or discrete sympathetic response

Heating of a patch of skin causes relatively restricted vasodilation in heated region

Patients unaware of items to one side of space

Hemineglect - unilateral neglect, hemispatial neglect, or spatial neglect

What is reduced in size in schizophrenics?

Hippocampus

State of post-synaptic cell in inhibitory response

Hyperpolarized - depresses excitability = inhibitory post-synaptic synaptic potential (ipsp) - ipsps can summate too

Gray matter of primary somatosensory cortex contains six layers of cells. What layer receives the bulk of incoming signals from somatosensory nuclei of the thalamus?

IV

CN that turns eye downward and laterally

IV - superior oblique

CN that senses carotid blood pressure

IX

In the patellar reflex, what will synapse directly on alpha motor neurons that innervate the muscle being stretched?

Ia sensory fiber - Ib sensory fibers synapse with inhibitory interneurons

Intraocular pressure of 25 mmHg. Experiences eye pain. Explanation?

Increased hydraulic resistance of trabecular meshwork

Astrocytes participating in metabolic control of cerebral blood flow have three events associating with process in what order?

Increased neuronal activity = Glutamate spillover --> Calcium wave --> Prostaglandin release

Relation between migraine and stroke

Increased risk of ischemic stroke in those who have migraine with *aura* (feelings and symptoms you notice shortly before headache begins)

Most common location of Incus erosion

Incus-stapedial joint

Example of divergence in multiple tracts

Info from *dorsal columns of spinal cord* take two directions 1. cerebellum 2. thalamus & cerebral cortex signal transmitted in 2 directions

Division of nervous system responsible for processing info and creation of memory

Integrative Division

Mechanism of pain from internal organ being perceived to originate from distant area of skin

Intermingling of second order neurons in dorsal horn of spinal cord from skin and viscera

Most common cause of stroke

Ischemia = 87%

2 types of stroke

Ischemic (87%) - interruption of blood supply Hemorrhagic (13%) - rupture of blood vessel

Permeability of what ions is increased with lower membrane potential?

K+ Cl-

What is most likely to be increased 6 months after ablation of the amygdala?

Kluver-Bucy syndrome - *lack of fear, extreme curiosity, forgetfulness, oral fixation, strong sex drive*

The axons of ganglion cells transmitting visual signals in the form of action potentials to the primary visual cortex are most likely to synapse in what structure?

Lateral geniculate nucleus

Capacity of excited neuron to reduce activity of neighboring neurons

Lateral inhibition - improves degree of contrast - occurs at every synaptic level (for dorsal column system) - dorsal column nuclei, ventrobasal nuclei of thalamus, cortex

Have greatest area of representation followed by face and thumb in somatosensory cortex...

Lips

How can hyperventilation induce seizures?

Low CO2 --> spontaneous and asynchronous firing of neurons --> affects all mental & psychological abnormalities (panic attacks, seizures, sleeping problems, depression, schizophrenia) - CO2 = major controlled of brain blood flow - low CO2 = brain vessel contriction

Structure maximally sensitive to linear hear movement in vertical plane

Macula of saccule - hair cells

What gender has higher pain threshold?

Males - females show more sensitivity to pain

Middle ear ossicle that is attached to tympanic membrane

Malleus

Sensory receptors that detect deformation

Mechanoreceptors - stretches membrane --> opens ion channels

Structure that is an important pathway for communication between limbic system and brain stem?

Medial forebrain bundle - extends from septal and orbitofrontal regions of cerebral cortex downward through center of hypothalamus to brain stem reticular area

Adaptation of Meissner corpuscles vs. Merkel discs

Meissner = rapid Merkel = slow

Tactile receptors located in: non-hairy skin close to surface (fingertips, lips, eyelids, nipples, & external genitalia)

Meissner corpuscles - motion detection, grip control - skin motion, grip control - skin motion, low frequency vibration - rapid adaptation - receptive field = 22 mm^2 - Abeta nerve fibers

Receptors used to read Braille letters

Merkel cell - each dot = action potential - activity patterns recorded from mechanosensory afferents in fingertip - 9 mm^2 = small receptive field!

Expanded tip tactile receptor found in dermis of hairy skin that is specialized to detect continuously applied touch sensation

Merkel's disc

What substance is most likely to increase in the rods of the retina when the light is turned on?

Metarhodopsin II - photons active rhodopsin to become metarhodopsin II in rods of retina = activated rhodopsin

Small external ear accompanying absence of external auditory canal

Microtia

Blood supply of Temporal lobe

Middle cerebral artery Posterior cerebral artery - Auditory perception, semantics, memory

Results from abnormal vascular phenomenon. Vasospasm followed by prolonged vasodilation.

Migraine - Vasodilation stretches coverings of blood vessels

What receptors are more plentiful for thermal sensations?

More *cold* receptors than warm receptors - density of cold receptors varies: highest on lips, lowest on trunk

Function of Meissner corpuscles

Motion detection Grip control

What receptors have the largest myelinated axon?

Muscle spindle - proprioception - 13-20 micrometer = fast conduction velocity - Ia, II

Temporal summation: How long does a NT open a membrane potential vs. the time-frame of a post-synaptic potential?

NT open membrane channel for *1 msec* Postsynaptic potential (EPSP or IPSP) for *15 msec*

Mechanical distortion increases

Na+ conductance - this receptor potential is an electrotonic potential

Groups of neurons with special characteristics of organization

Neuronal pools - comprise many different types of neuronal circuits: converging, diverging, reverberating, inhibitory

Type of cholinergic receptor found at synapses between preganglionic and postganglionic neurons of sympathetic system

Nicotinic

Are there lymphatics in the brain? How do leaked proteins return to blood?

No - Fluid leaks out of vessels regardless of blood-brain barrier: perivascular space: subarachnoid space --> *ARACHNOID VILLI* - Starling forces: lymphatic system = only mechanism that can transport protein out of interstitial spaces

Does the attenutation reflex protect against a shotgun blast?

No - too quick for protection

What sensory system has the smallest range of intensity discrimination?

Olfactory - presence or absence, rather than quantitative measurement

Why must smelling involve a central mechanism?

Olfactory receptors adapt very slowly, but olfactory sensation itself adapts rather rapidly

Gradual type of glaucoma

Open angle glaucoma - *90%* of cases in US - *Chronic* glaucoma - insidious / no pain initially - reduced flow through *trabecular meshwork* GO (Gradual Open)

- conductive hearing loss - bone pathology: only temporal bone - early manifestations: abnormal bone adjacent to stapes, next to oval window - fixes stapes in place: can't vibrate - could be via measles virus

Otosclerosis

Control sensitivity of inner hair cells for different sound pitches - auditory signals are transmitted by inner hair cells

Outer hair cells

Can deplete Substance P from local nerve endings and relieve pain

Over-the-counter creams containing *capsaicin* - made from chili peppers

Leads to down-regulation of membrane receptors

Overactivity - drug addict: haven't taken for long time --> membrane receptors upregulate = little works --> long time = receptors down-regulated = takes more drug to get effect

Formula for Pressure

P = QR (A = BC)

Percentage of words correct. - Repeat back 2 syllable word --> can't? = lost speech

PB Max - CN 8

Receptor with the highest rate of adaptation

Pacinian corpuscle

Most rapidly adapting receptor

Pacinian corpuscle - fluid between layers --> push = translocated fluid to other side - *no longer distorted after contact*

What fibers activate RAS?

Pain fibers = hard time sleeping - chronic pain

Minimum amount of pain that evokes report of pain

Pain perception threshold

Exhibit little or no adaptation

Pain receptors

What type of receptors *do not adapt* to stimulus?

Pain receptors = tonic

Reached when subject acts to stop pain

Pain tolerance threshold

Mechanism that focuses lens (accomodation) is controlled by

Parasympathetic nerves - excite sphincter muscle --> decrease pupillary aperture (miosis)

Accommodation regulated by what part of nervous system?

Parasympathetics

What allows the visual apparatus to accurately determine the distance of an object from the eye (depth perception)?

Phenomenon of *stereopsis* - because one eye is a little more than 2 inches to side of other eye, image on 2 retinas differ from one another = binocular parallax (stereopsis) = allows *person with 2 eyes far greater ability than person with only one eye to judge relative distances when objects nearby*

For the eye to adapt to intense light, what must occur?

Photochemicals in both rods and cones will be reduced to retinal and opsins - reduction of rhodopsin and cone pigments by light reduces concentrations of photosensitive chemicals in rods and cones --> sensitivity of eye to light is correspondingly reduced

Perivascular space (Virchow-Robin space) in brain is formed between wall of small penetrating vessels and what structure?

Pia mater

What projection system is contained in the middle cerebellar peduncle?

Pontocerebellar

The more rapid the rate of terminal stimulation, the greater the

Post-synaptic potential* - *second opening of same membrane channel* can increased the post-synaptic potential to greater level

Stimulation by touching or pulling on what structure is least likely to cause a painful sensation?

Postcentral gyrus - *brain lacks pain receptors*

Blood supply of Occipital lobe

Posterior cerebral artery - visual processing center = visual cortex

What projection system is contained in inferior cerebellar peduncle?

Posterior spinocerebellar

21-year-old woman is right-handed musician of considerable talent. What brain structure is most likely to have been physically large in the dominant hemisphere compared with the nondominant hemisphere at birth?

Posterior temporal lobe - posterior temporal lobe is larger at birth in the dominant hemisphere of the brain, which is the left hemisphere in 95% of people

Area of brain that is involved in generating motor image of action in absence of actual movement

Premotor cortex - Brodmann's area *6*

Function of the round window

Pressure relief valve for cochlea - as stapes moves back and forth against oval window, increase and decrease in pressure caused by the in-and-out movement of oval window is relieved by opposite back-and-forth movement of round window

Fine motor movement of index finger can be elicited by stimulation of what brain area?

Primary motor cortex

What is the R.I. if speed in a substance is 200,000 km/sec?

R.I. = 300,000 / 200,000 = 1.5 - speed of light in air = 300,000 km/sec - R.I. = ratio of speed in air to speed in substance

When parallel light rays pass through a concave lens, what happens to the rays?

Rays *diverge* from each other - in contrast, a convex lens converges rays toward each other When a group "caves" in, they *diverge* from each other...

One of the few places where hyperpolarization can act as a stimulus for activation

Retina of eye: rods and cones - hyperpolarize on exposure to light - stimuli can cause either hyperpolarization or hypolarization (depolarization)

Transmit signals that depict accurate spatial detail and color

Retinal *X* ganglion cells --> LGN (*parvocellular*)

Light entering eye passes through what retina layer first?

Retinal ganglion layer

Night blindness (rods often go first) Decreased peripheral vision Loss of central vision in advanced cases

Retinitis Pigmentosa - main risk factor = family history - 1 in 4,000 - pigment deposition - no effective treatment - sunglasses to reduce UV exposure

Type of circuits that have: - positive feedback - discharge for long time

Reverberatory circuits

Window that allow fluid in cochlea to move?

Round window

Visual scene moving (turning head) = eye fix on highlight after another in visual field jumping at a rate of 2-3 jumps/sec. Jumps are known as: Movements are known as:

Saccades - occur very rapidly (10% of time spent making saccades) - vision suppressed during saccadic movements Opticokinetic movements

What molecules combine to form rhodopsin?

Scotopsin & 11-cis-retinal

Highest degree of pain localization comes from

Simultaneous stimulation of free nerve endings and tactile fibers - general sensation of pain is poorly localized, but tactile receptor & pain receptor stimultaneously stimulated = pain sensation localized with greater accuracy

Irritation of nasal structures leads to

Sinus headache

Stimuli of Meissner corpuscles

Skin motion *Low frequency vibration* (200 cycles/sec & below) Found in nonhairy (glabrous) areas of skin such as fingertips & lips - areas that are particularly sensitive to even the *lightest touch*

Stimuli of Ruffini corpuscle

Skin stretch

Adaptation speed of Ruffini corpuscle

Slow adaptation

In a neuron with a resting membrane potential of -65 mV, the distribution of what ion across the neuronal membrane represents the greatest potential electromotive force (EMF)?

Sodium - Nernst potential for sodium = +61 mV - resting membrane potential of +61 mV required to prevent sodium from moving across cell membrane - greater than either Nernst potential for K+ (-86 mV) or Cl- (-70 mV)

Basis for referred pain

Some visceral pain signals and pain signals from skin provide *convergent* input to common set of neurons in the dorsal horn - visceral pain fibers can provide input to anterolateral tract cells that also receive somatic pain from skin surface - convergence of these 2 types of pain signals onto single spinal cord neurons = basis for referred pain

Distant synapses whose epsp's overlap

Spatial summation

Middle ear ossicle that is attached to oval window

Stapes

Sound waves cause back and forth movement of the tympanic membrane, which moves what back and forth?

Stapes - causes displacement of fluid in cochlea & induces vibration in *basilar membrane*

Causes widespread arousal of nervous system

Stimulation of reticular areas of brain stem and intralaminar nuclei of thalamus (where pain fibers terminate)

Responsible for rapid directional movement of both eyes

Superior colliculus

What nucleus controls circadian rhythms?

Suprachiasmatic nucleus

Process of NT takes time

Synaptic delay - from delay, one can calculate number of neurons in a circuit

Function of what organ or system is dominated by sympathetic nervous system?

Systemic blood vessels

Function of Ruffini corpuscle

Tangential force Hand shape Motion detection

The stereocilia of hair cells are embedded in what membrane?

Tectorial - scala media is bordered by the basilar membrane and Reissner's membrane and contains a tectorial membrane

Successive epsp's from same synapse

Temporal summation

Damage to what brain regions leads to retrograde amnesia

Thalamus

Causes of ischemic stroke

Thrombosis - blood clot formed locally Embolism - blood clot from elsewhere Systemic hyptension - shock Venous thrombosis - dural venous sinuses

Disorder of trigeminal nerve; unilateral paroxysmal (sudden onset) facial pain. Can be triggered by touch or cold. Late onset: 60-70's

Tic Douloureux (painful tic)

Location of Merkel discs

Tip of epidermal ridges

= surgical removal - drill through *temporal bone* to get to tumors - opens up *semicircular canals* --> open up *posterior* part of canal - want to *preserve facial nerve* - tumor has to be peeled off facial nerve - any residual = hearing loss - muscle and fascia in mastoid cavity, belly fat put in ear

Translabyrinthine Approach

Have least area of representation in somatosensory cortex

Trunk and *lower body*

Functions to transmit vibrations in the air to the cochlea (inner ear)

Tympanic membrane - amplifies signal because area of tympanic membrane is 17 times larger than the oval window - connected to ossicles: malleus, incus, stapes

Malleus in center

Umbo - light reflex seen - semi-translucent membrane - pressure change can perforate (water ski, hit ear hard)

Leads to up-regulation of membrane receptors

Underactivity - drug addict: haven't taken for long time --> membrane receptors upregulate = little works --> long time = receptors down-regulated = takes more drug to get effect

Phenomenon of decerebrate rigidity can be explained by

Unopposed activity of *pontine reticular nuclei* - pontine reticular nuclei are tonically active = have stimulatory effect on *anti-gravity* muscles of body - decerebrate rigidity result when stimulatory signal from higher brain areas to medullary nuclei are absent

Old-age nerve deafness

Usually via long-term exposure to sounds that are too loud and last too long - damage to hair cells - do not grow back

CN for chewing

V

CN responsible for face and mouth touch and pain

V

Where are blood vessels most compressed in brain due to high ICP?

VENOUS end - lowest pressure - highest compliance - thin-walled

Responsible for control of body's behavioral functions

Ventral lateral geniculate

What structure in cerebellum has topographical representation of body?

Vermis and *intermediate hemisphere* --> reflects peripheral sensory input from muscles, tendons, joint capsules, & some cutaneous receptors

Hibernate in ganglia causing rash in associated dermatome

Viruses such as varicella zoster - Shingles follows dermatome - years after chickenpox infection, virus may break out of nerve cell bodies --> travel down nerve axons to cause viral infection of skin associated with nerve - rash occurs in dermatome of infected nerve cell

What best describes when the transmission of sound waves in the cochlea occurs?

When the foot of the stapes moves inward against the oval window and the round window bulges outward

CN that senses aortic blood pressure

X

CN that simulates digestive organs

X

CN that slows heart rate

X

Ganglion cells that respond best to color images and are most numerous of the three types of ganglion cells

X ganglion cells = 55%, receives input from at least one cone

Stomach referred pain localized where?

above umbilicus

Neural activity in brain is increased during what pH conditions?

alkaline conditions

Each taste bud can detect

all 5 flavors - every part of tongue includes receptors for every basic taste

Neurons that cause skeletal muscles to contract

alpha-Type A

What stops reverberatory circuits?

ans. fatigue of synaptic junctions - positive feedback - how epileptic seizures stop

As axons of motor neurons leave spinal cord and course peripherally to skeletal muscle, they must pass through what structure?

anterior root

CSF enter venous system primarily through

arachnoid villi

Most common cause of thrombosis

arteriosclerotic plaques in feeder arteries to brain

Action potentials only occur at

axon - motor part

Colon referred pain localized where?

below umbilicus

Major endogenous opiates

beta-endorphin, met-enkephalin, leu-enkephalin, dynorphin - enkephalins and dynorphin found in brain stem and spinal cord - beta-endorphin - found in hypothalamus & pituitary

Inhibition of pain signals by tactile stimulation of the skin is mediated by what type of afferent neurons from mechnoreceptors?

beta-type A - via lateral inhibition - mediated by inhibitory interneurons in dorsal column of spinal cord

Low stimulus causes what type of receptor potential response?

big

Cocaine effect on eyes...

blocks reuptake of NE at nerve ending --> dilation of normal pupil - *cocaine test is diagnostic* but does not localize lesion

Brain highly dependent on

blood flow and oxygen delivery - very little anaerobic metabolism - cessation of flow for 5-10 s = loss of consciousness

Over-treatment of diabetics with insulin causes

blood glucose to fall to low levels - can lead to psychotic disturbances and coma

Position sense, or more commonly proprioceptive sensation, involves muscles spindles and

both tactile and joint capsule receptors

Organ with the highest amount of cholesterol

brain!

Under low or reduced light conditions, what chemical compound is responsible for the inward-directed sodium current in the outer segment of the photoreceptors?

cGMP - low light --> level of cGMP is high --> cGMP-dependent sodium channels in outer portions of rods and cones allow sodium ions to pass from extracellular space to intracellular space of photoreceptor

BBB is located in between what cells?

capillary endothelial cells - tight junctions between ECs - lipid nature of cell membranes - enzymatic barrier removes molecules from blood - efflux pumps: extrude fat-soluble molecules that crossed into cells

Contraction of *ciliary muscle* attached to ligament does what to lens?

causes lens to become thicker = increases refractive power of lens

Coup and Contrecoup brain injuries both associated with

cerebral contusions - brain bruised - Contrecoup injuries can also be caused by sudden acceleration or deceleration of brain in absence of impact against the skull (automobile accident / "shaken baby syndrome"

Open-angle glaucoma is the same thing as

chronic glaucoma

Myopia (near-sightedness) corrected with

concave lens

Rate of adaptation: Merkel cells

continuous/slow

Ganglion cells receiving info from rods and cones located in nasal portion of each retina terminate in

contralateral *lateral geniculate nucleus*

multiple terminal from single incoming fiber terminate on same neuron *provides*

convergence from single source - provides *spatial summation* spatial summation occurs when 2 or more presynaptic axon terminals are activated simultaneously --> ind. effects are summated = increased postsynaptic potential --> enables combined EPSPs to exceed threshold value for an AP

Hyperopia (far-sightedness) corrected with

convex lens

2/3 of refractive power of eye results from anterior surface of

cornea

Fibers that conduct pain signals to dorsal column of spinal cord

delta-Type A (fast pain) & type C fibers (slow pain)

Spatial resolution of stimuli on skin varies throughout body because

density of mechanoreceptors varies

Location of Pacinian corpuscle

dermis and deeper tissues

Fibers from nasal halves of retina (crossing to opposite side) and fibers from opposite temporal retina synapse in

dorsal lateral geniculate nucleus (LGN) of thalamus --> primary visual cortex via optic radiation

Stimuli of Merkel discs

edges, points, corners, curvature

Dendrites transmit signals by

electrotonic conduction - transmission of current by conduction in fluids of dendrites

BBB attributed PRIMARILY to

endothelial cells - astrocytes = slight role

ICP assess clinically by

extent of optic disk protrusion (papilledema) left not normal, right normal

Why are there no APs on dendrites?

few voltage-gated sodium channels - dendrites transmit signals via *electrotonic conduction*

Man has automobile accident that completely eliminates all nerve traffic in the right half of the spinal cord at C2. Loss of what function is most likely in the right hand of this man?

fine sensory - vibration sense, fine touch, proprioception, 2-point discrimination in dorsal-column medial lemniscal pathway cross to contralateral side in medulla *both motor and vibration sense* are lost on same side (ipsilateral) as cord lesion

What foramina allow cerebrospinal fluid to pass directly from ventricular system into subarachnoid space?

foramen and Magendie and two lateral foramina of Luschka - form communication channels between ventricular system within brain and subarachnoid space that lies outside brain and spinal cord

CBF can be measured using

functional magnetic resonance imaging & positron emission tomography

Form synaptic junctions with intrafusal muscle fibers

gamma motor neurons

What to do if you have a GCS less than 15 after hit in the head

get *CT* - concussion can be 14-15 with associated signs and symptoms

2nd leading cause of blindness worldwide

glaucoma (after cataracts)

Athetosis results when what area of the brain is dysfunctional?

globus pallidus - slow and continuous writhing movement of arm, neck, or face

If one intubates in sporadic conditions, the practitioner might cause

hypoxia - sedation might also cause hypoxia or hypotension - paramedics don't intubate children as much as adults because it's out of their comfort zone: may become hypoxic in between attempts

Progressive rise in receptor potential (becomes less negative) of typical mechanoreceptor is most likely to have proportional ...

increase on frequency of action potential in axon from that mechanoreceptor

Increased intraocular pressure is caused by

increased resistance to outflow of aqueous humor through network of trabeculae in canal of schlemm

epsp's and ipsp's result from

increases in membrane permeability

Release of NT at chemical synapse in CNS is dependent upon

influx of calcium into presynaptic terminal

90% of auditory signals are transmitted by

inner hair cells - 3-4x as many *outer hair cells* than inner hair cells - outer hair cells may control sensitivity of inner hair cells for different sound pitches Book says: Nearly *95%* of 8th CN sensory fibers that innervate cochlea form synaptic contact with *inner air cells*

Brain will get glucose, regardless of

insulin - glucose delivery to brain is *not* insulin dependent, unlike nearly all other tissue

What is likely increased in a patient with subdural hematoma

intracranial pressure - *decreased intracranial volume*

Types of receptors on postsynaptic terminal of chemical synapses

ionotropic receptor - cation/anion channels (ions) - rapid response / short-lived - small molecule transmitters (ACh, NE) metabotropic receptor - second messenger - prolonged responses, neuropeptides

Cut blood flow off to organ...

ischemia - ischemic tissues are *hypoxic*

Specificity of nerve fibers for transmitting only one modality of sensation is called the

labeled line principle - given neuron = only one type of sensory info only - one neuron goes to brain from sensory receptor

Flow path of CSF

lateral ventricles --> 3rd ventricle --> aqueduct of sylvius --> 4th ventricle --> foramen of magendie --> cistern magna --> subarachnoid space --> exits via arachnoid villi = one-way valves

Incoming sensory signal excites which layer of the cerebral cortex?

layer IV

Increased ICP leads to

loss of CSF reduction in venous volume to compensate for increase in brain volume process eventually becomes exhausted increased ICP can compress veins --> increases capillary hydrostatic pressure = brain swell herniation of brain, distortion and pressure on cranial nerves, as well as vital neurological centers

Loss of areas 5 and 7 in parietal areas

loss of Somatosensory association area - inability to recognize complex objects - neglect of contralateral world and even refusal to acknowledge ownership of contralateral body

Drugs are designed to cross BBB by

making them more soluble

Which olfactory is old vs. new?

medial = old lateral = new

Oldest part of brain

medulla oblongata - other parts simply added on - essential for breathing, autonomics, vaso-, etc.

Brain tissue itself is insensitive to pain. Pain sensitive structures include

membranes that cover brain and blood vessles - dura - blood vessles of dura - venous sinuses - middle meningeal artery = headache - dura mater & cranial nerve sheaths contain pain receptors transmit signals, which travel with CNs X & XII & enter spinal cord levels C2 & C3

Sympathetic nerves excite radial fibers of iris causing pupillary dilation. This is known as

mydriasis

Length of eyeball in myopia

near-sightedness = *long eyeball* - too much refractory power in lens system - no mechanism to focus distant objects on retina (contraction of ciliary muscle would make distant objects even less in focus) - objects come into focus as they move closer to eye - corrected with concave lens

Heart referred pain localized to

neck, left shoulder, and arm

High metabolic rate in nervous system is primarily due to high metabolic activity in

neurons

Image becomes better focused when lens thickness is changing in the right direction. This is known as

oscillation - degree of accommodation occurs all the time (2x per second)

What receptors are considered rapidly adapting (phasic) receptors?

pacinian corpuscle meissner's corpuscle semi-circular canals - respond only when change is taking place - rate & strength of response related to rate & intensity of stimulus - important for predicting future position or condition of body - balance & movement

Function/stimuli of *unmyelinated* free nerve endings

pain, temperature, itch - type C

Slow pain (second pain) transmitted in what tract?

paleospinothalamic tract

Accommodation is under control of

parasympathetics - when object moves toward eye --> ciliary muscle contracts --> thicker lens

Function of Pacinian corpuscles

perception of *distant events* through transmitted vibrations; *tool use*

Neuron is said to be *facilitated* if

potential is nearer the threshold for firing that normal but not yet to the firing level - easier to stimulate this neuron with subsequent input - increased transmitter released produced by AP follows closely upon preceding AP - prolonged elevation of pre-synaptic Ca2+ levels

What is there prolonged elevation of following synaptic activity in *facilitation*?

presynaptic calcium levels - calcium already high when second stimulus hit - voltage-gated calcium channels

Pupillary light reflex: light on reflex causes a few impulses to pass from optic nerves to

pretectal nuclei

Separation of signals from the 2 eyes is lost in the

primary visual cortex - signals from one eye enter every other column, alternating with signals from other eye - allows cortex to decipher whether 2 signals match

Flow of intraocular fluid

produced by ciliary body --> flows through pupil into anterior chamber --> between cornea and iris --> through trabeculae --> enters canal of schlemm = empties into aqueous veins --> extraocular veins

Presbyopia (inability to accommodate) caused by

progressive denaturation of proteins in lens - makes lens less elastic - Power of accommodation = 0 diopters by the age of 70

Rate of adaptation: Meissner's corpuscle

rapid/phasic - can be more than 2 with 1 nerve

Refractive index

ratio of speed in air to speed in substance - ex. if speed in substance = 200,000 km/sec, R.C. = 300,000/200,000 = 1.5

What determines the temperature sensation?

relative *degree of stimulation* of receptors - thermal receptors adapt to stimulus but not completely

Transmit rapidly changing B&W visual signals

retinal *Y* ganglion cells --> LGN (*magnocellular*)

For a sensory nerve fiber that is connected to a Pacinian corpuscle located on a palmar surface of the right hand, the synaptic connection with the subsequent neuron in the corresponding sensory pathway is located in the

right dorsal column nucleus - Pacinian corpuscle transmits modality of vibration that is transmitted in dorsal column-medial lemniscus system

APs only occur when receptor potential...

rises above threshold - increases stimulus intensity --> increases receptor potential --> increases AP frequency

What tastes cause *depolarization* of the respective taste cells?

salts sweets sours umami

Meniere's disease results from excess endolymph in

scala media and membranous labyrinth - vertigo, nystagmus, sudden hearing loss, tinnitus (ringing) - Endolymphatic sac ruptures & heals repeatedly (intermittent symptoms)

Neurons involved with endogenous analgesia system and with cell bodies in Raphe nucleus are most likely to secrete

serotonin - from *Raphe* nuclei - stimulates interneuons in dorsal column that, in turn, secrete enkephalin

What allows for 3-D/*stereoscopic* imaging?

slightly different images from each eye sent to brain, where impulses are fused to make single image

Adaptation rate of free nerve endings

slow adaptation

Speed of adaptation of muscle spindles

slow-adapting - need to know length of muscle at all time

Speed of adaptation of joint-capsule receptor

slow-adapting - position, angle of joint - *Ruffini*

Lesions that damage primary motor cortex and other surrounding motor cortical areas lead to

spastic paralysis in affected muscles

Shape or relaxed: lens

spherical in shape

2 muscles attach to ossicles:

stapedius --> stapes tensor tympani --> *malleus*

Freezing cold and burning hot are the same sensation because of

stimulation of pain receptors

Fixation movements of eyes results from negative feedback mechanism controlled at level of

superior colliculus - prevents objects of attention from leaving foveal portion of retina

Location of Free nerve endings

surface of body and elsewhere

Focal length dependent upon

thickness of lens

Fast pain (first pain) transmitted via

type *A-delta* fibers (velocity 6-30 m/sec)

Slow pain (second pain) transmitted by

type C fibers (0.5 - 2 m/sec)

On entering cord, pain fibers may travel...

up or down 1-3 segments and terminate on neurons in dorsal horn - *2nd neuron* crosses immediately to opposite side --> passes to brain in anterolateral columns - some neurons terminate in *reticular substance* but most go all the way to the *ventrobasal complex of the thalamus* - *3rd order neurons* go to cortex - fast, sharp pain can be *localized well* when other tactile receptors are simultaneously stimulated

*Optimal* stimuli of Pacinian corpuscle

vibration (*250 Hz* = optimal)

20/40 means...

what a normal person can see at 40 feet, this person must be at 20 feet to see