BIOL 2113 Chapter 13 notes (Periphreal nervous system)

Adjusting Muslce Spindle sensitivity

When (y) gamma neurons are stimulated by brain, spindle is streched, and contraction force is maintained or increased. If gamma neurons are inhibited, spindle becomes nonresponsive, and muscle relaxes. Important as speed and difficulty increase. (ex. gymnast on balance beam)

nystagmus

is strange eye movements during and immediatly after rotation, accompanied by vertigo

Lamellar (Pacinian) corpuscles

large receptors respond to deep pressure and vibration when first applied (then turn off) Located in deep dermis

dislike for sourness and bitterness

protective way of warning us if something is spoiled or poisonous

vanilloid receptor

protein in nerve membrane is main player. Acts as ion channel that is opened by heat, low pH, chemicals (ex. capsaicin in red peppers)

PNS (peripheral nervous system)

provides link from and to world outside our body. Consists of all neural structures outside brain and spinal cord.

pattern recognition

recognition of familiar or significant patterns in stimuli (melody in piece of music)

Chemoreceptors

respond to chemicals (respond to smell, taste, changes in blood chemistry.)

Bulbous corpuscles (Ruffini endings)

respond to deep, continuous pressure, in dermis

Photoreceptors

respond to light energy (ex. retina)

Receptors for hearing and balance

respond to seperate stimuli and are activated independently

Mechanoreceptors

respond to touch, pressure, vibration, stretch.

Learn (aquired) reflexes

result from practice or repetition (ex. driving skills)

perception of pain

warns of actual or impending tissue damage so protective action can be taken. Stimuli include: extreme pressure and temperature, histamine, K+, ATP, acids, and bradykinin

phasic receptors

(fast adapting) send signals at beginning or end of stimulus (Ex. receptors for pressure, touch, and smell)

eyelids

(palpebrae) two movable flaps of skin which cover and uncover each eyeball. Seperated at palpebral fissure. Meet in corers at medial and lateral commissure. Eyelids brink reflexively every 3-7 seconds, offers protection form foreign objects and spreads secretions to moisten the eye.

Functional anatomy of photoreceptors

(rods and cones) are modified neurons that resemble upside-down epithelial cells with tips embedded in pigmented layer of retina. Outersegment: light-receving region- contains visual pigments (photopigments) that change shape as they absorb light. Inner segment of each joints cell body. Inner segment is connected via cilium to outer segement and to then to cell body. In rods, inner segment is connected to cell body via an outer fiber. Cell body is then connected to synaptic terminal via inner fibers. Plasma membrane of outer segment folds back to form many discs. Visual photopigments are embedded in discs. Pigments change shape as they absorb light. Photoreceptors are vulerable to damage if retina detached, destroyed by intense light, vision is maintained becayse outer segment is renewed eyvery 24 hours. Tips fragement fall off and are phagocytized.

Third-order sensory neurons

conduct impuses to the cerebral cortex (perceptual level)

Activation of taste receptors

*Binding of food chemical (tastant) depolarizes taste cell into gustatory epithelial cell membrane, causing release of neurotransmitter. Neurotransmitter binds to dendrite of sensory neuron and initiate a generator potential that leads to action potentials. Different gustatory have different thresholds for activation, bitter receptors are most sensitive. All adapt in 3-5 seconds, with complete adaptation in 1-5 minutes.

Anatomy of Crista Ampullaris

- Each crista has supporting cells and hair cells that extend into gel-like mass called ampullary cupula - Dendrites of vestibular nerve fibers encircle base of hair cells

light and dark adaptation

-Rhodopsin is so sensitive that bleaching occurs even in starlight *In bright light, bleaching occurs so fast that rods are virtually nonfunctional -Cones respond to bright light -So, activation of rods and cones depends on: *Light adaptation *Dark adaptation

Anatomy of a macula

- Each is a flat epitheliaal patch containing HAIR CELLS - The hair cells have sterocilia plus one kinocilium - Located next to tallest stereocilia. - Stereocilia are embedded in otolith membrane, jelly-like mass studded with otoliths. Otoliths increase membrane's weight and increase its inertia. Utricle maculate are horizonal with vertical hairs. Respond to change along a horizonal plane, such as tilting head. Foreward/backward movements stimulate utricle. Saccule maculae are vertical with horizonal hairs. Respond to change along a verical plane. Up/down movements stimulate saccule (ex. acceleration of an elevator.) Hair cells synapse with fibers of vestibular nerve whose cell bodies are located in superior and inferior vestibular ganglia. Part of vestibulocochlear cranial nerve (VIII)

Light Transduction Reactions

- Light-activated rhodopsin activates G protein transducin - Transducin activates PDE, which breaks down cyclic GMP (cGMP) - In dark, cGMP holds channels of outer segment open Na+ and Ca2+ depolarize cell - In light cGMP breaks down, channels close, cell hyperpolarizes > Hyperpolarization is signal for vision

Light adaptation

- When moving from darkness into bright light we see glare because: • Both rods and cones are strongly stimulated • Large amounts of pigments are broken down instantaneously, producing glare • Pupils constrict - Visual acuity improves over 5-10 minutes as: • Rod system turns off • Retinal sensitivity decreases • Cones and neurons rapidly adapt

Vestibulocochlear nerves

-Afferent fibers from hearing receptors (cochlear division) and equilibrium receptors (vestibular division) pass from inner ear through internal acoustic meatuses, and enter brain stem at pons-medulla border -Mostly sensory function; small motor component for adjustment of sensitivity of receptors -GFormerly auditory nerve

Innervation of Visceral Muscle and Glands

-Autonomic motor endings and visceral effectors are simpler than somatic junctions -Branches form synapses en passant ("synapses in passing") with effector cells via varicosities - Acetylcholine and norepinephrine act indirectly via second messengers -Visceral motor responses are slower than somatic responses

Levels of Motor Control

-Cerebellum and basal nuclei are the ultimate planners and coordinators of complex motor activities -Complex motor behavior depends on complex patterns of control 1. Segmental level 2. Projection level 3. Precommand level

Projection level

-Consists of Upper motor neurons that initiate direct (pyramidal) system to produce voluntary skeletal muscle movements -Brain stem motor areas that oversee indirect (extrapyramidal) system to control reflex and CPG-controlled motor actions -Projection motor pathways send information to lower motor neurons, and keep higher command levels informed of what is happening

The olfactory pathway

-Filaments of olfactory nerves synapse with mitral cells located in overlying olfactory bulb -Mitral cells are second-order neurons that form olfactory tract - Synapse occurs in structures called glomeruli -Axons from neurons with same receptor type converge on given type of glomerulus - Olfactory bulb also contains amacrine granule cells that can inhibit mitral cells so that only highly excitatory impulses are transmitted - Impulses from activated mitral cells travel via olfactory tracts to piriform lobe of olfactory cortex. - from here, two major pathways take information to various parts of brain. - One pathway bring information to frontal lobe. Smell si conscously interpreted and identified here. Some smells may pass through thalamus first. Some information sent to hypothalaus, amygdala, and other regions of limbic system. Emotional responses to odor are elicited here.

tendon reflex

-Involves polysynaptic reflexes -Helps prevent damage due to excessive stretch -Important for smooth onset and termination of muscle contraction - Produces muscle relaxation (lengthending) in response to tension. - Contraction or passive strech activates tendon reflex. - Afferent impulses transmitted to spinal cord. - Contracting muscle relaxes; antagonist contracts (reciprocal activation) - Information transmitted sumultaneously to cerebellum and used to adjust muscle tension.

CNS axons

-Most CNS fibers never regenerate -CNS oligodendrocytes bear growth-inhibiting proteins that prevent CNS fiber regeneration -Astrocytes at injury site form scar tissue -Treatment: neutralizing growth inhibitors, blocking receptors for inhibitory proteins, destroying scar tissue components

Smell transduction

-Odorant binds to receptor, activating a G protein *Referred to as Golf-G protein activation causes cAMP (second messenger) synthesis -cAMP opens Na+ and Ca2+ channels -Na+ influx causes depolarization and impulse transmission -Ca2+ influx causes decreased response to a sustained stimulus, referred to as olfactory adaptation *People can't smell a certain odor after being exposed to it for a while

Neural impulses from cochlear biolar cells reach auditory cortex via following pathway

-Spiral ganglion (auditory bipolar cell bodies) -Cochlear nuclei (medulla) --Superior olivary nucleus (pons-medulla) -Lateral leminiscus (fiber/tract) -Inferior colliculus (midbrain auditory reflex center) -Medial geniculate nucleus (thalamus) -Primary auditory cortex (conscious awareness of sound) Some fibers cross over, some do not; so both auditory corticles recieve input from both ears.

Stretch and Tendon Reflexes

-To smoothly coordinate skeletal muscle nervous system must receive proprioceptor input regarding -Length of muscle From muscle spindles -Amount of tension in muscle From tendon organs

Motion sickness

-sensory inputs are mismatched -Visual input differs from equilibrium input -Conflicting information causes motion sickness -Warning signs are excess salivation, pallor, rapid deep breathing, profuse sweating -Treatment with antimotion drugs that depress vestibular input, such as meclizine and scopolamine

how stretch reflex works

-stretch activates the muscle spindle -sensory neurons synapse directly with motor neurons in the spinal cord -motor neurons cause the stretched muscle to contract

innervation of skeletal muscle

-takes place at neuro-muscular junction - Neurotransmitter acetylcholine (ACh) is released when nerve impulses reach axon terminal. - Ach diffuses across synaptic cleft and attaches to ACh receptors on sarcolemma - ACh binding to receptors result in: Movement of Na+ and K+ across membrane. Depolarization of muscle cell. An end plate potential, spreads to adjacent areas of sarcolemma, which triggers opening of Na+ voltage-gated channels. Results in an action potential, which leads to muscle contraction.

circulation of aqueous humor

1. Aqueous humor forms by filtration from the capillaries in the ciliary processes 2. Aqueous humor flows from the posterior chamber through the pupil into the anterior chamber. Some also flows through the vitreous humor 3. Aqueous humor is reabsorbed into the venous blood by the scleral venous sinus

PNS Axon Regeneration Steps

1. Axon fragments and myelin sheaths distal to injury degenerate (wallerian degeneration); degeneration spreads down axon. 2. Macrophages clean dead axon debris; Schwann cells are stimulated to divide. 3. Axon filaments grow through regeneration tube. 4. Axon regenerates, and new myelin sheath forms.

Levels of neural integration in sensory systems

1. Receptor level—sensory receptors 2. Circuit level—processing in ascending pathways 3. Perceptual level—processing in cortical sensory areas

components of a reflex arc

1. Receptor: site of stimulus action 2. Sensory neuron: transmits afferent impulses to CNS 3. Integration center: Either monosynaptic or polysynaptic region within CNS 4. Motor neuron: conducts efferent impulses form integration center to effector organ 5. Effector: Muslce fiber or gland cell that responds to eferent impulses by contracting or secreting

Transmission of Sound to the Internal Ear

1. Tympanic membrane: sound waves enter external acoustic meatus and strike tympanic membrane, causing it to vibrate. The higher the intensity, the more vibration. 2. Auditory ossicles: transfer vibration of eardrum to oval window. Tympanic membrane is about 20x larger that oval window, so vibration transferred to oval window is amplified about 20x 3. Scala vestibuli: stapes rocks back and fourth on oval window with each vibration, causing wave motions in perilymph. Wave ends at round window, causing it to bulge outward into middle ear cavity. 4a. Helictrema path: Waves with frequencies below threshold of hearing travel through helictrema and scala tympani to round window. 4b. Basilar membrane path: sounds in hearing range go through cochlear duct, vibrating basilar membrane at specific location, according to frequency of sound

Capturing light process

1. pigment synthesis: Opsin and 11-cis retinal combine to form rhodopsin in dark. 2. Pigment bleaching: when rhodopsin absorbs light, 11-cis isomer of retinal changes to all-trans isomer. Retinal and opsin seperate (rhodopsin breakdown) 3. Pigment regeration: all-trans retinal converted back t0 11-cis isomer. Rhodopsin is regenerated in outer segments.

Cranial Nerves overview

12 pairs of cranial nerves are associated with brain. Two attach to the forebrain, the rest with the brain stem. Most are mixed nerves, but two pairs purely sensory. Each numbered (I-XII) and named from rostral to caudal.

spinal nerves

31 pairs of nerves arising from the spinal cord. ALl are mixed nerves named for point of issue from spinal cord. Supply all body parts except head and part of neck. 8 pairs of cervical nerves (C1-C8) 12 pairs of thoracic nerves (T1-T12) 5 pairs of lumbar nerves (L1-L5) 5 pairs of sacral nerves (S1-S5) 1 pair of tiny coccygeal nerves (C0)

Spinal nerves continued

7 cervical vertabrae give ride to 8 pairs of cervical spinal nerves because: each of the first 7 pairs (C1-C7) exits the vertebral canal superior to vertebra for which it is named. Last spinal nerve (C8) exits canal inferior to C7) so, vertebra C& has a nerve that leaves above it and one that leaves above it and one that leaves below it. Each of the other spinal nerves exits inferior to vertebra for which it is named.

ganglion

A cluster of nerve cell bodies, often of similar function, located in the PNS.

Cerebellum

Acts on motor pathways pathways through projection areas of brain stem, Acts on motor cortex via thalamus to fine--tune motor activity.

cochlea

A small spiral, conical, bony chamber, size of a split pea, extends from vestible, coils around bony pillar (modiolus), contains cochlear duct, which houses spiral organ (organ of corti) and ends at cochlear apex. Chochlear duct and osseous spiral lamina (thin, shelflike extension of bone) together divide cavity of bony cochlea into three chambers: Scala vestiblue: abucts oval window, contains perilymph Scala media (cochlear duct): contains endolymph Scala tympani: terminate at round window; contains perilymph Scale tympani and vestivuli are continuous with each other at helicotrema (apex) Vestibular membane "roof" of cochlear duct that seperates scala media from scala vestibuli. Stria vascularis: external wall of cochlear duct composed of mucosa that secretes endolymph. Floor of cochlear duct composed of: bony spiral lamina, basilar membrane, which supports spiral organ. Spiral organ contains cochlear hair cells, functionally arranged in one rows of outer hair cells. Hair cells are sandwitched between tectorial and basilar membranes. The cochlear branch of nerve VIII runs from spiral organ to brain.

Nonencapsulated (free) nerve endings

Abundant in epithelia and connective tissues Most are nonmyelinated, small-diameter group C fibers; distal terminals have knoblike swellings Respond mostly to temperature, pain, or light touch

constriction of pupil

Accomodation pupillary reflex involves constriction of pupils to prevent most divergent light rays from entering eye. Mediated by parasympathetic nervous system. Convergence of the eyeballs: Medial rotation of eyeballs causes convergence of eyes toward object being viewed. Controlled by somatic motor neuron innervation on medial rectus muscles.

Automonic (visceral) reflexes

Activate visceral effectors (smooth or cardiac muscle or glands)

pain tolerance

All perceive pain at same stimulus intensity Pain tolerance varies "Sensitive to pain" means low pain tolerance, not low pain threshold Genes help determine pain tolerance, response to pain medications Research to allow genes to determine best pain treatment

Strech reflex actions

All strech reflexes are monosynaptic and ipsilateral (motor activity is one the same side of body.) Positive reflex reactions provide two pieces of info: Prove that sensory and motor connections between muscle and spinal cord are intact. Strength of response indicates degree of spinal cord excitability

internal ear

Also known as the labyrinth (maze). Located in temporal bone behind eye socket. Two major divisions: Bondy labryrinth: system of tortuous channels and cavities that worm through the bone. Divided into thre regions: vestibule, semicircular canals, and cochlea, filled with perilymph fluid. Membranous labryrith; series of membranous sacs and ducts contained in bony labryrinth; filled with potassium-rich endolymph

Saturday night paralysis

An intoxicated person falls asleep with an arm draped over the back of a chair or sofa edge, cutting off blood supply to radial nerve

dermatome

Area of skin supplied by a single spinal nerve. All spinal nerves except C1 participate in dermatomes. Extent of spinal cord injuries ascertained by affected dermatomes. Most dermatomes overlap, so destruction of a single spinal nerve will not cause complete numbness.

Optic cranial nerve (II)

Arise from retinas; really a brain tract. Pass through optic canals, converge, and partially cross over at optic chiasma. Optic tracts continue to thalamus, where they synapse. Optic radiation fibers run to occipital (visual) cortex. Purely sensory (visual) function

Lumbar plexus

Arises from L1-L4 and innervates the thigh, abdominal wall, and psoas muscle.

Sacral plexus

Arises from L4-S4 - Serves the buttock, lower limb, pelvic structures, and perineum

Eye rotation

As rotation begins, eyes drift in direction opposide to rotation; then CNS compensation causes rapid jumb toward direction of rotation. As rotation ends, eyes continue in direction of spin, then jerk rapidly in opposite direction.

Visual Pathway to the Brain

Axons of retinal ganglion cells form optic nerve. Medial fibers from each eye cross over at the optic chiasma then contiune on as optic tracts, which means each optic contains fibers from lateral (temporal) aspect of eye on same side and medial (nasal) aspect of opposite eye. Each carries information from same half of visual field. Most fibers of optic tracts continue on to lateral genuculate nuclei of thalamas. From there, thalamic neurons form optic radiation which projects to primary visual cortex in occipital lobes. Conscious perception of visual images occurs here. Other optic tract fibers send branches to midbrain. One set ends in superior colliucli, area controlling extrinsic eye muslces. A small subset of ganglion cells in retina contains melaopsin (circadian pigment).

Back

Back is innervated by dorsal rami via several branches. Each branch innervates a strip of muscle and skin in line with where it emerges from spinal cord.

rootlets

Both ventral and dorsal roots are branched medially as ___ that then join laterally to form spinal nerve

strech reflex

Brain sets muscle's length via strech reflex. (ex. Knee-jerk reflex is a strech reflex that keeps knees from buckling when tou stand upright). Strech reflexes maintain muscle tone in large postural muscles and adjust it reflexively. Causes muscle contraction on side of spine in response to increased length (strech) on other side of spine.

Irritation of the phrenic nerve

Causes spasms of diaphragm (hiccups). If both phrenic nerves are severed, or if C3-C5 region of spinal cord is destroyed, diaphragm becomes paralyzed. Respiratory arrest occurs. Victim requires mechanical respirator, air is forced into the lungs breathing for them

Adaptation

Change in sensitivity in prescence of constance stimulus. Receptor membranes become less responsive. Receptor potentials decline in frequency or stop/

two sources of blood supply to retina

Choroid supplies the outer third (photoreceptors) and central artery and vein of the retina supply the inner two thirds. the central artery and veign enter/exit eye in center of optic nerve. Vessels are visible in a living person

Central pattern generation (CPGs)

Circuits that control locomotion and specific, often-repeated motor activity. Consist of networks of oscillating inhibitory and excitatory neurons, which set crude rhythms and patters of movement.

Nonencapsulated (free) nerve endings (thermoreceptors)

Cold receptors are activated by temps from 10 C to 40 C. Located in superficial dermis. Heat receptors are activated from 32 C to 48 C, located in deeper dermis. Outside those temperature ranges, nociceptors are activated and interpreted as pain.

Posterior segment

Contains vitreous humor: -transmits light -supports posterior surface of lens -holds neural layer of retina firmly against pigmented layer -contributes to intraocular pressure. Vitreous humor forms in embryo and last whole life

Functional anatomy of muscle spindles

Composed of 3-10 modified skeletal muslce fibers called intrafusal muscle fibers that are enclosed in a connective tissue capsule. Central regions of intrafusal fibers lack myofilaments and are noncontractile. End regions contain actin and myosin Myofilaments and can contract. Regular effector fibers of muscle referred to as extrafusal muscle fibers. Contractile end regions of spindle are innervated by gamma (y) efferent fibers. Help maintain spindle sensitivity. Note: Extrafusal fibers (contractile muscle fibers) are innervated by alpha (a) efferent fibers of large alpha (a) motor neurons

First-order sensory neurons

Conduct impulses from receptor level to spinal reflexes or second-order neurons in CNS

Clouding of lens (cataracts)

Consequence of aging, diabetes melitus, heavy smoking, and frequent exposure to intense sunlight. Some cogenital, crystallin proteins clump. Can be replaced surgically with artificial lens

Ventral roots

Contain Motor (efferent) fibers from ventral horn motor neurons. The fibers innervate skeletal muscles.

Dorsal roots

Contain sensory (afferent) fibers from sensory neurons in dorsal root ganglia and conduct impulses from peripheral receptors

primary visual cortex

Contains topographical map of retina, Neurons here respond in dark and bright edges and to object orientation, Provide form, color, motion inputs to visual association areas. Info is also passed on to temporal, parietal, and frontal lobes, where objects are identified and location in space is deturmined.

Brachial plexus and upper limb cords

Cords of brachial plexus give rise to nerves of the upper limb five of the most important are: 1. Axillary- innervates deltoid, teres minor, and skin and joint capsule of shoulder 2. Musculocutaneous- innervates biceps brachii and brachialis, coracobrachialis, and skin of lateral forearm. 3. Median- innervates skin, most flexors, forearm pronators, wrist and finger flexors, thumb opposition muscles. 4. Ulnar- supplies flexor carpi ulnaris, part of flexor digitorium profoundus, most intrinstic hand muslces, skin of medial aspect of hand, wrist/finger flexion. 5. Radial- innervates essentially all extensor muscles, supinators, and posterior skin of limb

Tendon organ

proprioceptors located in tendons that detect stretch

Sensorineural deafness

Damage to the neural structures at any point from the cochlear hair cells to the auditory cortical cells. Typically from gradual hair cell loss. Cochlear implants that convert sound energy into electrical signals are effective for congenital or age/noise cochlear damage. Inserted into drilled recess in temporal bone. So effective that deaf children can learn to speak

Capturing light

Deep purple pigment of rods is rhodopsin. arranged in rod's outer segment. Three steps of rhodopsin formation and breakdown: pigment synthesis, pigment bleaching, and pigment regeneration. Similar process in cones, but different types of opsins and cones require more intense light.

Loss of an eye or destruction of one optic nerve eliminates

Depth perception, periphreal vision on damaged side. If neural destruction occurs beyond optic chiasma then part or all of opposide half of the visual field is lost. Ex (stroke can affect left visual cortex, which leads to blindness in right half of visual field.

Retina detachement treatment and symptoms

Described as "curtain being drawn across the eye" or sootlike spots or light flashes. Treatment: reattachment of retina with laser surgery.

Projection (perceptual level)

Exact point in cortex activated always linked to activation of same sensory neuron

The eqilibrium pathway to the brain

Equilibrium information goes to reflex centers in the brain stem. Allows fast, reflexive responses to imblalance to we don't fall down. Impulses from activated vestibular receptors travel to either vestibular nuclei in brain stem or to cerebellum. Three modes of input for balance and orientation: vestibular receptors, Visual receptors, somatic receptors

joint kinesthetic receptors

proprioceptors that monitor joint position and motion

Where does the somatosensory system recieve inputs from?

Exeroceptors (external stimuli), propioceptors (body movements), and interoceptors (other internal stimuli). Imput is relayed toward head, but processed along the way.

Oculomotor cranial nerve (III)

Fibers extend from ventral midbrain through superior orbital fissures to four of six extrinsic eye muscles. Function in raising eyelid, directing eyeball, constricting iris (parasympathetic), and controlling lens shape

Trochlear cranial nerve (IV)

Fibers from dorsal midbrain enter orbits via superior orbital fissures to innervate superior oblique muscle. Primarily motor nerve that directs eyeball.

Hypoglossal cranial nerves (XII)

Fibers from medulla exit skull via hypoglossal canal. Innervate extrinsic and intrnsic muscles of tounge that contribute to swallowing and speech

Glossopharyngel cranial nerves (IX)

Fibers from medulla leave skull via jugular foramen and run to throat. Motor functions: innervate part of tounge and pharynx for swallowing and provide parasympathetic fibers to parotid salivary glands. Sensory functions: Fibers conduct taste and general sensory impulses from pharynx and posterior tongue, and impulses from carotid chemoreceptors and baroreceptors.

Brachial plexus and upper limb

Formed by ventral rami of C5-C8 and T1 (and often C4 and/or T2) Gives rise to nerves that innervate upper limb

Accessory cranial nerves (XI)

Formed from ventral rootlets from C1 to C5 region of spinal cord (not brain). Rootlets pass into cranium via each foramen magnum. Accessory nerves exit skull via jugular foramina to innervate trapezius and sternocleidmastoid muscles. Formerly spinal accessory nerve.

Processing at the Receptor Level

Generating a signal: For sensation to occur, the stimulus must excite a receptor, and the AP must reach CNS. Stimulus energy must match receptor specifically (toch receptors do not respond to light). Stimulus must be applied within receptive field (area receptor monitors). Small the field, more accurate location of stimulus by the brain. MUST REACH THRESHOLD= AP

Tibial nerve

Gives rise to sural nerve that serve parts of leg. At ankle, tibial nerve divides into medial and lateral plnar nerves that serve the foot.

Taste tranduction

Gustatory epithelial cell depolarization caused by: salty taste is due to Na+ influx that directly cuases depolarization. Sour taste is due to H+ acting intracellularly by opening channels that allow other cations to enter. Unique receptors for sweet, bitter, and umami, but all are coupled to G protien Gustducin. Activation causes release of stored Ca2+ that opens cation channels, causing depolarization and relase of neurotransmitter ATP

Activating receptors of a macula

Hair cells release neurotransmitter continuosly. Acceleration/deceleration causes a change in amount of neurotransmitter released. Leads to change in AP frequency to brain. Density of otolith membrane causes it to lag behind movement of hair cells when head changes positions. Base of stereocilia moves at same rate as head, but tips embedded in otolith are pulled by lagging membrane, causing hair to bend. Ion channels open and depolarizaion occurs. Bending of hairs in direction of kinocilia depolarizes hair cells, increases amount of neurotransmitter released. More impulses travel up vestibular nerve to brain. Bending of hairs away from kinocillia: Hyperolarizes receptors, less neurotransmitter released, reduces rate of impulse generation. Thus brain is informed of change in head movement.

Amplitude

Height of crest. Amplitude percieved as loudness: subjective interpretation of sound intensity. Measured in decibels (dB). Normal conversation is around 50 dB. Threshold of pain is 120 dB. Severe hearing loss can occur with prolonged exposure above 90 dB

Babinski's sign

If primary motor cortex or corticospinal tract is damaged, plantar reflex is replaced by an abnormal reflex called.... The great toe dorsiflexes and smaller toes fan laterally. Infants exhibit babinski's sign until they are about a year old because nervous systems are not completely myelinated. Although clinical relevant, physiological mechanism of babinkskis sign is not understood

Physiology of Smell

In order to smell something, it must be volatile, must be in gaseous state, oderant must also be able to dissolve in olfactory epithelium fluid.

Basal Nuclei

Inhibit various motor centers under resting conditions

injuries to brachial plexus

Injuries are common. Severe injuries can weaken or paralyze entire upper limb. Injuries may occur if upper limb is pulled too hard, streching plexus. (ex. When football tackler yanks on arm of running back. Blows to top of shoulder can force humerus inferiorly. injury to median nerve makes it difficult ot use pincer crasp (opposed thumb and index finger) to pick up small objects. Seen in carpal tunnel syndrom, where median nerve is compressed. Unlar nerve is very vulerable to injury. Severe or chronic damage to ulnar nerve can lead to sensory loss, paralysis, and muscle atrophy. Affected individuals have trouble making a fist and gripping objects. Little and ring fingers become hyperextended at the knuckles and flexed at distal interphalngeal joints. Causes claw hand. Striking the funny bone the spot where this nerve rest against medial epicondyle can make the little finger tingle. Trauma to the radial nerve results in wrist drop, inability to exted the hand at the wrist. Improper use of a crutch can compress radial nerve and impair its blood supply,.

Superior and inferior gluteal nerves

Innervate buttocks and tensor fascia lata muscle

Common fibular nerve (common peroneal nerve)

Innervates knee joint, areas of skin of leg, and muscles of leg.

Thermoreceptors

sensitive to changes in temperature

Processing at the perceptual level

Interpretation of sensory input depends on specific location of target neurons in sensory cortex

anterior segment

Iris divides anterior segment into two chambers: • Anterior chamber—between cornea and iris • Posterior chamber—between iris and lens • Entire segment contains aqueous humor, a plasma like fluid continuously formed (unlike vitreous humor) by capillaries of ciliary processes • Drains via scleral venous sinus (canal of Schlemm) at sclera-cornea junction • Supplies nutrients and oxygen mainly to lens and cornea but also to retina, and removes wastes

Trigeminal cranial nerves (V)

Largest cranial nerves; fibers exted from pons to face. Three divisions. 1. Ophthalmic (V1): passes through superior orbital fissure 2. Maxillary (V2): passes through the foramen ovale. Convey sensory impulses from various areas of face (V1 and V2)

Focusing for close vision

Light from close objects (<6 m) diverges as approaches eye Requires eye to make active adjustments using three simultaneous processes Accommodation of lenses (changing lens shape to increase refraction) Near point of vision (closest point on which eye can focus

Wavelength and color

Light: packets of energy (Photons) that travel win wavelike fashion at high speeds. When visible light passes through spectrupm, it is broken up into bands of colors (rainbow), the visible spectrum (rainbow). Red wavelengths are longest and have lowest energy. And violet are shortest and have most energy. Color that eye percieves is a reflection of that wavelength. Grass is green because it absorbs all colors except green. White reflects all colors, and black absorbs all colors

sciatic nerve

Longest and thickest nerve of the body. Innervates hamstring muscles, adductor mangnus, and most muscles in leg and foot. Composed of tibial and common fibular.

segmental level of motor control

Lowest level of motor heirarchy- Constists of refelex and automatic movements. Segmental circuits activate networks of ventral horn neurons to stimulate specific groups of muscles.

Lumbosacral plexus and lower limb

Lumbar and sacral plexuses have significant overlap Fibers of lumbar plexus contribute to sacral plexus via lumbosacral trunk Lumbosacral plexus serves mostly lower limb, but also sends some branches to abdomen, pelvis, and buttocks

Regeneration of Nerve Fibers

Mature neurons do not divide. If damage is severe or close ot cell body, entire neuron may die as well as other neurons stimulated by its axons. If cell body of damage nerve is intact, the periphreal axon may regenerate in PNS; however, regeneration does not occur in CNS.

Vascular layer

Middle pigmented layer of eye, also called uvea Three regions: choroid, ciliary body, and iris

Simple receptors of the general senses

Modified dendritic endings of sensory neurons Are found throughout body and monitor most types of general sensory information

Structure and classification of nerves

Most nerves are mixtures of afferent and efferent fibers and somatic and autonomic (viceral) fibers. Nerves are classified according to the direction they transmit impulses

excitation of inner hair cells

Movement of basilar membrane deflects hairs of inner hair cells. Cochlear hair cells have microvilli that contain many sterocilia (hairs) that bend at their base. Longest hair cells are connected to shortest hair cells via tip links. Tip links, when pulled on, open ion channels they are connected to. Bending of stereocilia toward tallest ones pull on tip links, causing K+ and Ca2+ ion channels in shorter stereocilla to open. K+ and Ca2+ flow into cell causing receptor potential that can lead to release of neurotransmitter (glutamate). Can trigger AP in afferent neurons of cochlear nerve. Bending of stereocillia toward shorter ones causes tip links to relax. Ion channels close, leading to repolarization (and even hyperpolarization)

Function anatomy of muscle spindles

Muscle spindles are stretched (and excited) in two ways. External strech: extreme fore lengthens entire muscle. Internal strech: Y motor neurons stimulate spindle ends to contract, thereby streching spindle. Streching results increased rate of impulses to the spinal cord. Contracting muscle could reduce tension on muscle spindle, and sensitivity would be lost. Situation avoided by muscle spinde also shortening by impulses from Y motor nurons that fire when a neurons fire. a-y coactivation maintains tension and sensitivity of spindle during muscle contraction

Problems associated with refraction related ot eyeball shape

Myopia (nearsightedness). Eyeball is too long, so focal point is in front of retina. Corrected with a concave lens. Hyperopis (farsightedness) eyeball is too short, so focal point is behind retina. Corrected with a convex lens.

Tone

One frequency (tuning fork). Sound quality provides richness and complexity of sounds (music)

Role of outer hair cells

Nerve fibers coiled around hair cells of outer row are efferent neurons that convey messages from brain to ear Outer hair cells can contract and stretch, which changes stiffness of basilar membrane This ability serves two functions: Increase "fine-tuning" responsiveness of inner hair cells by amplifying motion of basilar membrane Protect inner hair cells from loud noises by decreasing motion of basilar membrane

Events at the Neuromuscular Junction

Nerve impulse arrives at axon terminal Ach released into synaptic cleft Ach diffuses across cleft and binds with receptors on sarcolemma Electrical events Generation of action potential

Composition and optic nerves

Olfactory and optic nerves: Neuron cell bodies located within special sense organs. Other nerves with sensory information (V, VII, IX, and X). Neuron cell bodies located in cranial sensory ganglia. Some mixed nerves contain both somatic and autonomic fibers. Most motor neuron cell bodies in ventral gray matter of the brain stem. Some autonomic motor neurons in ganglia.

Vagus cranial nerves (X)

Only cranial nerves that extend beyond head and neck region. Fibers from medulla exit skull via jugular foramen. Most motor fibers are parasympathetic fibers that help regualte activites of heart, lungs, and abdominal viscera. Sensory fibers carry impulses from thoracic and abdominal viscera, barorecepotrs, chemoreceptors, and taste buds of posterior tounge, and pharynx.

Sclera fibrous layer of eye

Opaque posterior region, protects and shapes eyeball, anchors extrisic eye muscles, posteriorly, where optic nerve exits, sclera is continous with dura mater of brain.

(inner layer) Retina

Originates as outpocketing of brain; Contains: millions of photoreceptor cells that transduce light energy, other neurons for processing light, glial cells, and a delicate two-layered membrane.

fibrous layer of eye

Outermost layer; dense avascular connective tissue Two regions: sclera and cornea.

Eyebrows

Overlie supraorbital margins Functions: Shade eye from sunlight Prevent perspiration from reaching eye

PNS axons

PNS axons can regenerate if damage is not severe

Focusing light on the retina

Pathway of light entering eye: cornea, aqueous humor, lens, vitreous humor, entire neural layer of retina, photoreceptors. Light is refracted three times along path 1. Entering cornea 2. entering lens 3. leaving lens. Majority of refractory power is in cornea; however, it is constant and cannot change focus

afferent pathway

Pathway of receptor to control center

Processing at the circuit level

Pathways of three neurons conduct sensory impulses received from receptors upward to appropriate cortical regions

Information processing in the retina

Photoreceptors and bipolar cells only generate graded potentials (EPSPs and IPSPs) Not APs When light hyperpolarizes photoreceptor cells - Stop releasing inhibitory neurotransmitter glutamate to bipolar cells - Bipolar cells (no longer inhibited) depolarize, release neurotransmitter onto ganglion cells - Ganglion cells generate APs transmitted in optic nerve to brain

Choroid region

Posterior portion of uvea; Supplies blood to all layers of eyeball; Brown pigment absorbs light to prevent scattering of light, which would cause visual confusion.

mixed nerves

Pure sensory (afferent) or pure motor (efferent) nerves are rate; most nerves are mixed.

Refraction and Lenses

Refraction: bending of light rays. Due to change in speed of light when it passes from one transparent medium to another and path of light is an oblique angle. Ex (from liquid to air, straw in water). Lenses of eyes can also refract light because they are curved on both sides.

Interoceptors (visceroceptors)

Respond to stimuli arising in internal viscera and blood vessels Sensitive to chemical changes, tissue stretch, and temperature changes. Causes discomfort but usually person is unaware of their workings.

Exteroceptors

Respond to stimuli arising outside the body Receptors in the skin for touch, pressure, pain, and temperature Most special sense organs

Proprioceptors

Respond to stretch in skeletal muscles, tendons, joints, ligaments, and connective tissue coverings of bones and muscles Inform brain of one's movements. (ex. catching vall flying towards you. Loss of proprioception leads in inability to control or coordinate one's movements

Visual pigments

Retinal: Key light absorbing molecule that combines with one of four proteins (opsins) to form visual pigments. Synthesized from vitamin A. Four opsins are rhodopsin (found in rods only), and three found in cones: green, blue, red (depending on wavelength of light they absorb) Cone wavelengths do overlap, so same wavelength may trigger more that one cone, enabling us to see variety of hues of colors. yellow light stimulates red and green cones, but if more red are triggered, we see orange

Comparing Rod and Cone Vision

Rods are very sensitive to light, making them best for night and periphreal vision. Contian a sigle pigment, so vision is percieved in gray tones only. Pathways converge causing fuzzy, indistict images. 100 rods may converge into one ganglion. Cones have low senesitivity, so require bright light for activation. React more quickly than rods. Have one of three pigments, which allow for vividly colored sight. Nonconverging pathways result in detailed, high-resolution vision. Some cones have their own ganglion cell, so brain can put together accurate, high acuity resolution images.

Four major branches of the brachial plexus

Roots- Five ventral rami (C5-T1) unite to form Trunks- upper, middle, and lower, which unite to form.. Divisions- anterior and posterior, which unite to form.. Cords- lateral, medial, and posterior

vestibular nystagmus

Semicircular canal impulses are linked to reflex movements of eyes

Sensory Receptors and Sensation (Survival Needs)

Sensation: awareness of stimulus. Perception: Interphretation of meaning of stimulus.

olfactory cranial nerve (I)

Sensory nerves of smell, Run from nasal mucosa to olfactory bulbs. Pass through cribiform plate of ethmoid bone. Fibers synapse in olfactory bulbs. Pathway terminates in primary olfactory cortex. Purely sensory (olfactory) function

pigmented layer of retina

Single-cell- layer, thick lining next to choroid Extends anteriorly, covering ciliary body and iris Functions: Absorbs light and prevents its scattering Phagocytizes photoreceptor cell fragments Stores vitamin A

location and structure of taste buds

Sensory organs for taste. Most of 10,000 taste buds are located on tounghe in papillae, peglike projections of tongue mucosa. Each taste bud consists of 50-100 flask-shaped epithelial cells of two types. Gustatory epithelial cells. Taste receptor cells that have microvilli called gustatory hairs that project into taste pores, bathed in saliva. Sensory dendrites collect around gustatory epithelial cells send taste signals to brain. Thre types of gustatory epithelial cells. One releaes serotinin; others lack synaptic vesticles, but one releases ATP as neurotransmitter. Basal epithelial cells: dynamic cells that divide every 7-10 days.

Extrinsic eye muscles

Six straplike extrinsic eye muscles Originate from bony orbit and insert on eyeball Enable eye to follow moving objects, maintain shape of eyeball, and hold it in orbit Four rectus muscles originate from common tendinous ring; names indicate movements Superior, inferior, lateral, and medial rectus Two oblique muscles move eye in vertical plane and rotate eyeball Superior and inferior oblique muscles originate with rectus muscles; passes through trochlea (fibrocartiaginous loop); rotates eye downward and laterally. Inferior oblique muscle; rotates eye up and laterally.

flower spray endings (secondary sensory endings)

Small axons at spindle ends Stimulated by degree of stretch only

Types of fibers in mixed nerves

Somatic afferent (sensory from muscle to brain) Somatic efferent (motor from brain to muscle) Visceral afferent (sensory from organs to brain) Visceral efferent (motor from brain to organs)

Properties of Sound

Sound is dependant on an elastic medium-one that physically transmits vibrations. Travels much slower than light. Pressure disturbane (alternating areas of high and low pressure) produced by a vibrating object and propagated by molecules of the medium (air)

Rami

Spinal nerve rami and their main branches supply entire somatic region of body from neck down. Dorsal rami supply posterior body trunk. Ventral rami supply the rest of the trunk and limbs. All ventral rami except T2-T12 form interlacing nerve networks called nerve plexuses. Found in cervical, brachial, lumbar, and sacral areas. Only ventrical rami form plexuses. Within plexus, fibers crisscross so that 1. Each branch contains fibers from several different spinal nerves 2. FIbers from ventral ramus go to body periphery cia several routines. Means each limb muscles is innervated by more than one spinal nerve, so damage to one does not cause paralysis

Spinal roots

Spinal nerves emerge from vertebral column via their respective intervertebral foramina. Spinal roots become progressively longer superiorly to inferiorly down cord. Lumbar and sacral roots are very long and extend through lower vertebral canal as cauda equina. Spinal nerres are 1-2 cm long. Almost immediatly after exiting foramen, spinal nerves divide into three brances 1. Dorsal ramus: smaller branch. 2. Ventral branch: Larger branch 3. Meningeal branch: tiny branch that reenters vertebral canal to innervate meinges and blood vessels

Strech reflexes homeostatic imbalance

Strech reflexes can be hypoactive or absent if periphreal nerve damage or ventral horn injury has occured. Reflexes are absent in people with chronic diabetes mellitus or neurosyphilis and during coma. Strech reflexes can be hyperactive if lesions of corticospinal tract reduce inhibitory effect of brain on spinal cord.

General senses

Tactile sensations (touch, pressure, stretch, vibration), temperature, pain, and muscle sense. No "one-receptor-one-function relationship. Receptors can respond to multiple stimuli.

Lacrimal apparatus (tear draining)

Tears drain into the lacrimal sac and nasolacrimal duct, which empties into the nasal cavity

Abdominal reflexes

Tests integrity of cord from T8 to T12 Stimulus: stroking skin of lateral abdomen above, below, or to side of umbilicus Response: contraction of abdominal muscles and movement of umbilicus toward stimulus Vary in intensity from one person to another Absent when corticospinal tract lesions are present

Concave

Thicker at edges than in center. Lenses disperse light, preventing light from being focused.

Innervation of joints

To remember which nerves serve which synovial joint- Hilton's law: Any nerve serving a muscle that produces movement at joint also innervates joint and skin over joint

second-order neurons

Transmit impulses to third-order sensory neurons

Cornea

Transparent anterior one-sixth of fibrous layer. Forms clear window that lets light enter and ends light as it enters eye. Epithelium covers both surfaces. External sheet-outer surface protects from abrasions. Inner layer, corneal endothelium contains sodium pumps that help maintain clarity of cornea by keeping water content low. Numerous pain receptors contribule to blinking.

Anterolateral thorax and abdominal wall

Ventral rami of T2-T12 are intercostal nerves that supply muscles of ribs, anterlateral thorax, and abdominal wall. Givee off cutaneous brances to skin along course. Two special thoracic nerves: T1 (tiny), T12 which is a subcostal nerve.

Inner ear

Vestibule: central egg-shaped cavity of bony labryrinth. Contains two membranous sacs. Saccule is continuous with cochlear duct. Utricle is continuous with semicircular canals. Sacs house equlibrium receptor regions (Macuale) that respond to gravity and changes in position of head. Semicircular canals: three canals oriented in three planes of space: anterior, lateral, and posterior. Anter and posterior are at right angles ot each other, whereas the lateral canal is horizontal. Membraneous semicircular ducts line each canal and communicate with utricle. Ampulla: enlarged area of ducts of each canal that houses equlibrium receptor region called the crist ampullaris. Receptors respond to angular (rotational) movements of the head.

visceral pain

Visceral pain results from stimulation of visceral organ receptors Felt as vague aching, gnawing, burning Activated by tissue stretching, ischemia, chemicals, muscle spasms

Cones

Vision receptors for bright light. High resolution color vision.

dark adaptation

When moving from bright light into darkness, we see blackness because: Cones stop functioning in low-intensity light. Bright light bleached rod pigments, so they are still turned off. Pupuls dialate. Rhodopsin accumluates in the dark, so retinal sensitivity starts to increase. Transducin returns to outer segments. Sensitivity increases within 20-30 minutes.

Lumbar plexus injuries

When spinal roots of lumbar plexus are compressed, gait problems occur. Other symptoms are pain or numbness of the anterior thigh. Femoral nerve serves prime movers that flex hip and extend knee. Damage can be caused by a herniated disc. If obturator nerve is impaired, person experinces pain in the medial thigh

sciatica

a common problem, is characterized by stabbing pain radiating over course of the sciatic nerve. Injury could be caused by a fall, disc herniation, or badly placed injection into the buttock. If the nerve is transected, leg is nearly useless and cannot be flexed because hamstrings are paralyzed. Foot and ankle cannot move at all, so foot drops into plantar flexion, a condition called footdrop. Recovey from sciatic nerve injury is slow and incomplete. For lesions below knee, thigh miuscles are spared. If tibial nerve is injured, paralyzed calf muscles cannot plantar flex foot, and a shuffling gait develops.

tinnitus

a jingling; a ringing or buzzing in the ear. Due to cochlear nerve degeneration, inflammation of middle or internal ears side effects of asprin

Inborn (intrinsic) reflex

a rapid, involuntary, predictable motor response to a stimulus (Ex. Maintain posture, control visceral activites). Can be modifies by learning and consious effort.

Perceptual detection

ability to detect a stimulus (requires summation of impulses)

somatic reflexes

activate skeletal muscle

Tonic receptors

adapt slowly or not at all. (Ex. nociceptors and most proprioceptors)

Umami

amino acids glutamate and aspartate. Example: beef or cheese taste.

Bitter

alkaloids such as quinine and nicotine, caffeine, and nonalkaloids such as asprin

electromagnetic radiation

all energy waves, from lomg radio waves, to short x-rays; visible light occupies a small portion in the middle of the spectrum. Ligh has wavelengths between 400 and 700 nm. Eyes respond only to visual light.

encapsulated dendritic endings

almost all are mechanoreceptors whose terminal endings are encased in connective tissue capsule

reciprocal inhibition

also occurs-afferent fibers synapse with internurons that inhibit a motor neurons of antagonistic muslces. (ex. In patellar reflex, streched muscle (quadriceps) contracts, and antagonist (hamstrings) relax.

lens epithelium

anterior region of cuboidal cells that differentiate into lens fiber cells

Ciliary body

anteriorly, choroid becomes ciliary body. Thickend ring of tissues surrounding lens. Consists of smooth muscle bundles, cillary muscles, that control shape of lens. Capillaries of cillary processes secrete fluid for anterior segment of eyeball. Cillary zonule (suspensory ligament) extends from ciliary processes to lens. Holds lens in position.

Retinal isomers

are different 3-D forms. Retinal is bent in dark, but when pigment absorbs light, it is straight. Bent form called 11-cis-retinal. Straight form called all-trans-retinal. Conversion of bent to straight initiates reactions that lead to electrical impulses along optic nerve

Macula lutea

area at posterior pole lateral to blind spot, contains mostly cones

Blinking aids in spreading tears

blinking spreads tears toward medial commissure, where they enter paired lacrimal conaliculi via lacrimal puncta

Conduction deafness

blocked sound conduction to fluids of internal ear. Causes include: impacted earwax, perforated ear drum, otitis media, otosclerosis of the ossicles

depth perception

both eyes view same image from slightly different angles. Visual cortex fuses these slightly different images, resulting in a three-dimesional image, which leads to depth perception. REQUIRES BOTHE EYES

itch receptors in dermis

can be triggered by chemicals such as histamine.

Facial Nerve (VII)

carries impulses from anterior two-thirds of tongue

Glossopharyngeal (X)

carries impulses from posterior one-third and pharynx

Pupil

central opening that regulates amount of light entering eye. Close vision and bright light cause sphinceter pupillae (circular muscles) to contract and pupils to constrict. parasympathetic control. Distant vision and dim light cause dialator pupillae (radial muscles) to contract and pupils to dialate. Sympathetic control. Changes in emotional state-pupils dialate when subject matter is appelaing or requires problem solving skills.

Quality

characteristic of sounds. Most sounds are mixtures of different frequencies.

Chemicals (smell)

chemicals must be dissolved in aqueous solution to be picked up by chemoreceptors. Smell receptors are excited by chemicals dissolved in nasal fluids. Taste receptors respond to chemicals in salava

Perineurium

coarse connective tissue that bundles fibers into fascicles

Iris

colored part of eye that lies between cornea and lens, continuous with cilairy body.

Glacoma

condition in which drainage of aqueous humor is blocked, causing fluid to back up and increase pressure within the eye. Pressures may increase to dangerous levels and compress retina and optic nerve, leading to blindness. Detection intraocular pressure deturmined by directing puff of air at cornea and measuring amount of corneal deformation. Test should be done after age of 40 yearly.

nyctalopia (night blindness)

condition in which rod function is seriously hampered. Ability to drive at night is impaired. Due to rod degeneration, commonly caused by prolonged vitamin A deficiency. Vitamin a can restore rod function if detected early. Can also be caused by retinis pigmentosa.

Retinal detachment

condition where pigmented and neural layers seperate (detach), allowing jellylike vitreous humor to seep between them. Can lead to permanent blindness, Occurs when retina is torn during tramatic blow to head or sudden stopping head during movement. (Bungee jumping)

Strabismus (cross-eyed)

congenital weakness of external eye muscles. Eye rotates medially or laterally. Eyes may alternate focusing on objects, or only controllable eye is used. Brain will disreguard inouts from deviate eye, which can become functionally blind if not treaded early.

pinkeye

conjunctival infection caused by bacteria or viruses, highly contagious

Lacrimal apparatus

consists of the lacrimal gland and a number of ducts that drain the lacrimal secretions into the nasal cavity

Rami communicantes

contain autonomic nerve fibers that join ventral rami in thoracic region

Mixed nerves

contain both sensory and motor fibers. Impulses travel both to and from CNS>

Ganglia

contain neuron cell bodies associated with nerves in PNS. Ganglia associated with afferent nerve fibers contain cell bodies of sensory neurons. Dorsal root gagnlia. Ganglia associated with efferent nerve fibers contain autonomic motor neurons. Autonomic gaglia (motor, visceral) chapter 14.

nasal cavity mucosa

continuous with mucosa of lacrimal duct system, so a cold or nasal inflammation often causes lacrimal mucosa to swell. Swelling constricts the ducts and prevents tears from draining, causing watery eye

Nerve

cordlike organ of PNS. Bundle of myelinated and nonmyelinated peripheral axons enclosed by connective tissyre

Sound waves

created when an object moves. Air molecules that are displaced by object movement are pushed foreward into ajdacent area, adding to air molecules already there. Creates an area of high pressure due to compression of molecules together. As object returns to origional position, the area it leaves now has fewer air molecules. Referred to as rarefaction. Sound waves are alternating areas (waves) of compressions and raregfactions. Object vibrating causes waves to move outward in all diections as air all around it is compress and rarefied. Kinetic energy of object is transferred to air molecules, which then transfer it to other air molecules. Wave energy declines with time and distance. Illistrated as an S-shaped curve or sine wave. Compression shown as crests, rarefactions as troughs.

Activating receptors of crista ampullaris

cristae respond to changes in velocity of rotational movements of head Inertia in ampullary cupula causes endolymph in semicircular ducts to move in direction opposite body's rotation, causing hair cells to bend. Bending hairs in cristae causes depolarization, rapid impulses reach brain at faster rate; bending of hairs in opposite direction causes hyperpolarizations. Fewer impulses reach brain, thus brain is informed of head rotations. Axes of hair cells in complementary semicircular ducts are opposide. Depolarization occurs in one ear, while hyperolarization occurs in other ear. Endolymph will come to rest after a while, so this system will come to rest after a while, so this system onlt detects changes in movements

localization of sound

depends on relative intensity and relative timing of sound waves reaching both ears. If timing is increased on one side, brain interphrets sound as coming from that side.

retinis pigmentosa

degenerative retinal diseases that destroy rods. Tips of rods not replaced when they slough off.

Rods

dim light and peripheral vision receptors. More numerous and more sensitive to light than cones. No color vision or sharp images, Numbers greatest at periphery.

far point of vision

distance beyond which no change in lens shape is needed for focusing. 20 feet for emmetropic (Normal) eye. Cornea and lens focus light precisely on retina at this distance.

motor endings (PNS)

elements that activate effectors by relesing neurotransmitters. These elements innervate skeletal muscle, visceral muscle, and glands.

Anulospiral endings (primary sensory endings)

endings wrap around spindle; stimulated by rate and degree of stretch

Equlibrium and orientation

equilibrium is response to various movements of head that rely on input from inner ear, eyes, and strech receptors.

vestibular apparatus

equilibrium receptors in semicircular canals and vestibule. Vestibular receptors monitor static equilibrium. Semicircular canal receptors monitor dynamic equlibrium

Glacoma treatment

eye drops that increase rate of aqueous humor or decrease its production; laster therapy or surgery

Focusing for distant and close vision

eyes are best adapted for distant vision. Ciliary muscles are completely relaxed in distance vision, which causes a pull on ciliary zoneule; as a result, lenses are streched flat.

Abducens cranial nerves (VI)

fibers from inferior pons enter orbits via superior orbital fissures. Primarily a motor, innervating lateral rectus muscle.

Facial cranial nerves (VII)

fibers from pons travel through internal acoustic meatuses and emerge through stylomastiod foramina to lateral aspect of face. Cheif motor nerves of face with five major branches. Motor functions include facial expression, parasympathetic impulses to lacrimal, and salivary glands. Sensory function (taste) from anterior two-thirds of toungue

Wall of eyeball contains

fibrous layer, vascular layer, inner layer.

Eye internal cavity is

filled with fluid called humors

Cervical Plexus and the neck

first four ventral rami (C1-C4) form looping cervical plexus. Most branches of this form cutaneous nerves. Innervate skin of neck, ear, back of head and shoulders. Other branches innervate neck muscles

efferent pathway

flow from control center to effector

hair follicle receptors

free nerve endings that wrap around hair follicles. Act as light touch receptors that detect bending of hair follicles. Act as light touch receptors that detect bending of hairs. (allows you to feel bugs landing on your skin

lens fibers

form bulk of lens and are filled with transparent protein crystallin. Lens fibers are continually added, so lens becomes more dense, convex, and less elastic with age.

Epithelial tactile (Merkel discs)

function as light touch receptors, located in deeper layers of epidermis.

taste

gustation

Eyelashes

have follicles that are innervated, nerve endings initiate reflex blinking. Cillary glands between hair follicles are modified sweat glands.

middle ear (tympanic cavity)

hearing only. A small, air-filled, mucosa-lined cavity in temporal bone. Flanked laterall by eardrim and medially by bony wall containing oval and round membranous windows. Epitympanic recess: Superior portion of middle ear (roof of cavity) Mastiod antrum: canal for communication with mastoid air cells in mastoid process. Pharyngotympanic (auditory) tube: connects middle ear to naspharynx. Usually flattened tube but can be opened by yawning or swalloing to equalize pressure in middle ear cavity with external air pressure. Tympanic membrane cannot vibrate efficiently if pressures on both sides are not equal, sounds are distorted. Auditory ossicles: three small bones in tympanic cavity. Malleus: the hammer is secured to ear drum, Incus: the anvil. Stapes: the sturrup base fits into oval window. Synovial joints allow malleus to articulate with incus which articulates with stapes. Suspended by ligaments; transmit vibratory motion of eardrum to oval window. Tensor tympani and stapedius muscles contract reflexively in response to loud sounds to prevent damage to hearing receptors.

External ear

hearing only. Arucle (pinna): shell-shaped structure surrounding ear canal that functions to funnel sound waves into auditory canal. Helix: cartilagiouns rim. Lobule: fleshy ear lobe. External acoustic meatus (auditory canal). Short, curved tube lined with skin bearing hairs, sebaceous glands, and ceruminous (earwax) glands, transmit soundwaves to ear drum. Tympanic mebrane (eardrum) boundary between external and middle ears. Thin, translucent connective tissue membrane. Vibrate in response to sound. Transfers sound to bones of middle ear.

Sour

hydrogen ions in solution

feature abstraction

identification of more complex aspects and several stimulus properties

spatial discrimination

identifying site or pattern of stimulus (studied by two-point discrimination test)

perception of pitch

impulses from hair cells in different positions along basilar membrane are interpreted by brain as specific pitches

Motor (efferent) nerves

impulses only away from CNS

Sensory (afferent) nerves

impulses only toward CNS

Perception of Pain impulse travel

impulses travel on different fibers (sharp pain is carried by A delta fibers and burning pain is carried by nonmyelinated C Fibers that release neurotransmitters glutamte and stubstance P

conjunctivitis

inflammation of the conjunctiva

How are pain receptors blocked?

inhibitory endogenous opioids (endorphins) adaptation for escaping dangerous situations

superficial reflexes

initiated by gentle cutaneous stimulation of area. Clinically important reflexes signal problems in upper motor pathways or cord-level reflex arcs

Pudendal nerve

innervates muscle and skin of perineum

Femoral nerve

innervates quadriceps and skin of anterior thigh and medial surface of leg

magnitude estimation

intensity coded in frequency of impulses

Pretectal nuclei (visual path to brian)

involved with pupillary reflexes

Detection of loudness

is determined by brain as an increase in the number of action potentials (frequency) that result when hair cells experience larger deflections

flexor (withdrawal) reflex

is initiated by painful stimulus - Causes automatic withdrawal of threatened body part - Ipsilateral and polysynaptic • Many different muscles may be called into play, so needs to be polysynaptic - Protective and important to survival - Brain can override • Example: Knowing a finger stick for blood test is coming, brain overrides pulling arm away

Menier's syndrome

labryinth disorder that affects cochlea and semicircular canals. Causes vertigo, nausea, and vomiting. Treatment: anti-motion sickness drugs in mild cases or surgical removla of labyrinth in severe cases

Color blindness

lack of one or more cone pigments. Inherited as an X-linked condition, so more common in males. As many as 8-10% of males have it. Depending on which cone is missing, red can appear green, or vice versa. Rely on different shades to get cues of color

vallate papillae

largest taste buds with 8-12 forming "V" at back of tongue

lacrimal gland location

located in orbit above lateral end of eye and secretes lacrimal secretion (tears), a dilite saline solution containing mucus, antibodies, and antibacterial lysozome

Lacrimal caruncle

located on the medial commissure - contains oil and sweat glands

Endoneurium

loose connective tissue that encloses axons and their myelin sheaths (schwann cells)

presbyopia

loss of accomodation over age 50

Phrenic nerve

major motor and sensory nerve of the diaphragm. Major muscles for breathing (C3-C5) recieved.

bulbar conjunctiva

membrane that covers white of eyes (not cornea) Small blood vessels found in this membrane; seen easily in "bloodshot" eyes

palpebral conjunctiva

membrane that lines underside of eyelids

salty

metal ions (inorganic salts); sodium chloride (saltiest)

otitis media

middle ear inflammation. Commonly seen in children with sore throat. Especailly those with shorter, more horizontal pharyngotmpanic tubes. Common cause of hearing loss in children. Acute infectious forms cause eardrum to bulge outward and become inflammed. Most cases respond to antibiotics.

Tarsal glands

modified sebaceous glands produce oily secretion that lubricates lid and eye.

Resonance

movement of different areas of basilar membrane in respnse to a particular frequency. Basilar membrane changes along its length: fibers near oval window are short and stiff. Resonate with high-frequency waves. Fibers near cochlear apex are longer, floppier. Resonate with lower frequency waves. So basilar membrane mechanically processes sound even before signals reach receptors.

Generating a signal (transduction)

must occur-energy of stimulus is converted into graded potential called generator potential or receptor potential.

precommand level

neurons in cerebellum and basal nuclei act as precommand areas that control outputs from cortex and brain stem motor centers that function to: reguate motor activity, precisely start or stop movements. Coordinate movements with posture, block unwanted movements, monitor muscle tone, perform unconsious planning and discharge in advace of willed movements.

Chalazion

obstruction of an oil gland of the eyelid that may result in a firm, usually painless bump

Spinal reflexes

occur without direct involvement of higher brain centers. Brain is still advised on spinal reflex on the relfex. Testing of somatic reflexes is important clinically to assess condition of nervous system. If exaggerated, distorted, or absent, may indicate degeneration or patholofy of specific nervous system regions. Common assesments are strech, flexor, and superficial reflexes.

diplopia (double vision)

occurs when movements of external muscles of two eyes are not perfectly coordinated. Person connot properly focus images of same area of visual field from each eye, so sees two images instead of one.

crossed extensor reflex

occurs with flexor reflexes in weight-bearing limbs to maintain balance - consists of ipsilateral withdrawal reflex and contralateral extensor reflex and contralateral extensor reflex. Contralateral side extended. (Ex. Stepping barefoot on broken glass causes damaged leg to withdraw and opposite leg to extend to support weight shift). Someone grabbing your arm causes that arm to flex and opposite arm to extend to pull body away.

superachiasmatic nucleus (visual path to brain)

of hypothalamus. timer for daily biorhythms.

smell

olfaction

Anosmias

olfactory disorders resulting from head injuries that tear the olfactory nerves. Aftereffects of nasal cavity inflammation. May be caused by neurological disorders, such as parkinson's disease, also may be an early sign of alztimers diseases.

foliate papillae

on side walls of tongue. Taste buds also found on soft palate, cheecks, pharynx, epiglottis

Referred pain

pain that is felt in a location other than where the pain originates. Visceral and somatic fibers travel along same nerves, so brain assumes stimulus comes from common (somatic) region (left arm pain during heart attack)

Sty

painful inflammation of any of the sebaceous glands at the base of an eyelash.

Somatosensory system

part of sensory system serving body wall and limbs

obturator nerve

passes through obturator foramen to innervate adductor muscles

Pitch

perception of different frequencies. Higher the frequency, higher the pitch.

Phototransduction

process by which light energy is converted into a graded receptor potential

stereocilia

project into K+ rich endolymph, with longest hairs enmeshed in gel-like tectorial membrane

visual processing

retinal cells split input into channels - color, brightness, angle, direction, speed of movement of edges - primary visual cortex, neurons respond to dark and bright images - Lateral inhibition decodes edge information job of amacrine and horizonal cells - Ganglions pass information to later geniculate of nuclei of thalamus to be processed for depth perception, with cone of input emphasized.

Glacoma symptoms

seeing halos around lights and blurred vision

Nociceptors

sensitive to pain-causing stimuli (e.g. extreme heat or cold, excessive pressure, inflammatory chemicals). Stimulate thermoreceptors, mechanoreceptors, and chemoreceptors.

Maculae

sensory receptors for static equilibrium. One organ located in each saccule wall and one in each utricle wall. Monitor the position of head in space. Play a key role in control of posture. Respond to linear acceleration forces, but not rotation

Conjunctival sac

space between palpebral and bulbar conjunctiva. (area for contact lens)

Lens

seperates internal cavity into anterior and posterior segments. Biconvex, transparent, flexible, and avascular. Changes shape to precisely focus light on retina.

optic disc

site where the optic nerve exits the eyeball. Lacks photoreceptors, referred to as blind spot. Retinal has quarter-billon photoreceptors.

Tactile (Meissner's) corpuscles

small receptors involved in discriminative touch Found just below skin, mostly in sensitive and hairless areas (fingertips)

Eye

some of 70% of body sensory receptors are in eye. Half of cerebral cortex is involved in visual processsing. one-sixth of surface is visible. enclosed and protected by fat cushion and bony orbit. Consists of accesssory structures and the eyeball.

Sensory receptors

specialized to respond to changes in environment (stimuli). activation results in graded potentials that trigger nerve impulses. Awareness of stimulus is occuring in the brain.

muscle spindles

spindle-shaped proprioceptors that respond to muscle stretch

Sweet

sugars, saccharin, alcohol, some amino acids, some lead salts

Tarsal plates

supporting connective tissue for folds, as well as anchor orbicularis oculi and levator palpebrae superioris muscles

Fibers

synaps in the solitary nucles of the the medulla travel to thalamus, and then to gustatory cortex in the insula. Hypothalamus and limbi system are involved; allow us to deturmine appreciation of taste.

plantar reflex

tests the integrity of the spinal cord from L4-S2; Stimulus: stroke lateral aspect of sole of foot. Response: downward flexion of toes

quality discrimination

the ability to identify submodalities of a sensation (e.g., sweet or sour tastes)

wavelength

the distance between two consecutive peaks or troughs in a wave shorter wave length= higher frequency of sound. Wavelenth is consistant for a constant sound.

Frequency

the number of waves that pass a given point per second. Pure tone has repeating crests and troughs. Range of human hearing is 20-20,000 hertz. MOst sensitibe between 1500 and 4000 Hz

olfactory epithelium

the organ of smell located in the roof of the nasal cavity. Covers superior nasal conchae. Contains olfactory sensory neurons. Bipolar neurons with radiating olfactory cilia. Supporting cells surround and cushion olfactory receptor cells. Olfactory stem cells lie at base of epithelium. Olfactory neurons are unusal bipolar neurons. Thin apical dendrites terminate in knob. Long, largely nonmotile cilia, olfactory cilia, radiate from knob. Covered by mucus (solvent for odorants). Budles of nonmyelinated axons of olfactory receptor cells gather in fascicles that make up filaments of olfactory nerve (cranial nerve I). Olfactory neurons have stem cells that give rise to new neurons every 30-60 days.

convex

thicker in center that at edges. Lenses bend light passing through it, so that rays converge at focal point. Image formed at focal point is upside down and reversed from left to right

fovea centralis

tiny pit in center of macula lutea that contains all cones, so is region with best visual acuity. Eye movement allows us to focus on an object so that fovea can pick it up.

Fungiform papillae

tops of these mushroom-shaped structures house most taste buds; scattered across tongue

Epineurium

tough fibrous sheath around all fascicles to form the nerve

Vagus nerve

transmits from epiglottis and lower pharynx

neural layer of retina

transparent layer that runs anteriorly to margin of ciliary body. Anterior end has serrated edges called ora serrata. Composed of photoreceptors, bipolar cells, gaglion cells. Signals spread from photoreceptors to bipolar cells to ganglion cells. Ganglion cells exit the eye as the optic nerve.

conjunctiva

transparent mucous membrane that produces a lubricating mucous secretion

gustatory pathway

two main cranial nerve pairs carry tate impulses from tounge to brain.

Astugmatism

unequal curvatures in different parts of cornea or lens. Corrected with cylindrically ground lenses or laster procedures.

olfactory hallucinations

unplesant odor, usually caused by temporal lobe epilepsy that involves olfactory cortex. Some people have olfactory auras prior to epilieptic seizures.

Equlibrium problems

unplesant; can cause nausea, diziness, and loss of balance. Nystagmus in the absense of rotational stimuli may be present.

Causes of taste disorders include

upper respiratory tract infections, head injuries, chemicals or medications, head and neck radiation for cancer treatment. zinc supplements may help some cases of radiation tase induce disorders.

receptors for special senses

vision, hearing, equilibrium, smell, and taste. All are housed in complex sense organs

Difference between roots and rami

~Roots lie medial to and from spinal nerves. Each root is purely sensory or motor. ~Rami lie distal to and are lateral branches of spinal nerves. Can carry both sensory and motor.

The Cristae Ampullares

• Receptor for rotational acceleration is crista ampullaris (crista) - Small elevation in ampulla of each semicircular canal • Cristae are excited by acceleration and deceleration of head - Major stimuli are rotational (angular) movements, such as twirling of the body - Semicircular canals are located in all three planes of space, so cristae can pick up on all rotational movements of head

Specificity of Olfactory Receptors

• Smells may contain 100s of different odorants • Humans have ~400 "smell" genes active in nose - Each encodes a unique receptor protein • Protein responds to one or more odors - Each odor binds to several different receptors - Each receptor has one type of receptor protein • Pain and temperature receptors are also in nasal cavities - Respond to irritants, such as ammonia, or can "smell" hot or cold (chili peppers, menthol)

Physiology of Taste

• To be able to taste a chemical, it must: - Be dissolved in saliva - Diffuse into taste pore - Contact gustatory hairs