Neurophysiology objectives

Describe the functions of four types of glia

* Largest number of cells in nervous system (90%), support neurons and maintain extracellular fluid (ie. play a critical role in the regulation of K+ balance) 1. Oligodendrocytes (CNS) and Schwann cells (PNS): form myelin sheath around neurons 2. Astrocyte: maintains extracellular fluid and supports metabolic activity of neurons 3. Microglia: macrophage-like cell that participates in immune functions 4. Ependymal cells: comprise lining of cerebral ventricle and regulate cerebrospinal fluid

describe the anatomy and physiology of the semicircular canals

- crista: sensory epithelium - semi-circular canal: anterior, posterior, horizontal - ampulla there are oriented approx. 90 degrees with respect to each other - stereocilia of hair cells project into the cupula function of semicircular canals: - respond to rotational acceleration of the head (i.e., sudden turning movements) - head rotation causes the movement of cupula in opposite direction of rotation (flow of endolymph is in the opposite direction of the roation of head: turn to the right, endolymph flows to the left --> <--) neuronal responses of semicircular canals: - neuronal responses are opposite on each side - the activity increases on that side where you turn your head - activity changes only during head roatation (during rotational acceleration and deceleration) - there are 3 canals: rotational acceleration in any direction will be detected.

describe the functions of the pinna, tympanic membrane, and middle ear bones

- pinna: collect sound waves and channels them into the ear canal, where the sound is amplified - tympanic membrane: It separates the outer ear from the middle ear. When sound waves reach the tympanic membrane they cause it to vibrate. The vibrations are then transferred to the tiny bones in the middle ear. - middle ear bones: (malleus, incus, stapes at oval window) transfer the vibrating signals to the inner ear. roles: protection against loud sounds, filter low tones in a loud environment: this will help to understand the human speech easier The cochlea and semicircular canals comprise the inner ear: - the cochlea is a bony spiral tube with 3 fluid-filled spaces within the tube (when stretched out, the spiral tube is approx. 30 mm in length) - the scala vestibuli and scala tympani join at the helicotrema. - the middle ear bones convert a mechanical displacement to a hydraulic displacement: movement of perilymph molecules in scala vestibuli

list the structures in the main central auditory pathway

- primary and secondary auditory cortex - medial geniculate complex of the thalamus: relay for all auditory information - inferior colliculus: auditory space map, analysis of complex sounds - superior olivary nucleus: neurons here receive inputs from both ears. this is the primary nucleus where horizontal sound localization occurs - cochlear nuclei: central terminals of spiral ganglion cell terminate ipsilaterally in the dorsal, posteroventral and anteroventral cochlear nuclei in the medulla. these nuclei contain the 2nd order sensory neurons of the auditory system.

sketch a motor unit, define the "size principle," and describe the relationship between motor units and the size principle

1- motivation (the highest level. in cerebral cortex) 2- initiation 3- execution (motor cortex and other cortical areas) 4a- direct pathways 4b- indirect pathways 5- movement 6- coordination of ongoing movement

Define the functional classes of neurons. Define the terms ipsilateral, contralateral, nerve, tract, funiculus, and fasciculus

1. Afferent (sensory) neurons: aka primary sensory neurons are from the body to the CNS (muscle to central nervous system) 2. Efferent (motor) neurons: from the CNS to effectors (brain to muscle) 3. Interneurons: aka local circuit neurons within the CNS 4. Projection neurons: sends axons to distant targets within the CNS - ipsilateral: on the same side - contranlateral: on the opposite side - nerve: bundle of axons in the peripheral nervous system that usually contains both afferent and efferent fibers - tract: collection of axons with the origin (cell bodies) in one area or nucleus that projects to a discrete target - funiculus: large collection of axons that may contain multiple tracts with many different terminations but found within a defined region of the CNS - faciculus: discrete collection of axons in the CNS

identify the four major EEG wave patterns. describe how the pattern of the EEG changes as you go from stage 1 to stage 4 sleep, and the unusual characteristics of REM sleep

1. Beta: awake with eyes open 2. Alpha: relaxed with eyes closed 3. Theta: light sleep 4. Delta: deep sleep three states of wakefulness and sleep 1. Awake: desynchronized EEG, alert, and "conscious" 2. Slow-wave sleep aka non-REM (NREM) sleep: synchronized EEG 3. REM (Rapid Eye Movement) (aka paradoxical sleep because resembles awake in EEG): desynchronized EEG, but this is not alert or "conscious" state; this is sleep . Four stages of sleep: 1. alpha and some theta waves 2. theta and delta waves 3. delta waves 4. REM sleep - EEG waves are desynchronized and similar to the awake state, but this is the deepest sleep stage

Sketch the spinal cord and label its major structures. Divide the spinal cord segments into five categories

1. Gray matter: central, butterfly-shaped cord region. Contains cell bodies of neurons and glia, dendrites, axonal processes. Appears gray due to lack of myelin 2. White matter: surronds gray matter. Consists primarily of axons; those with myelin give the color. White matter tracts connect regions of spinal cord, or spinal cord with brain 3. Dorsal roots: sensory (afferent) input reaches cord via dorsal roots, which consist of the axons of sensory neurons 4. Dorsal root ganglia: contain cell bodies of the pseudounipolar sensory neurons 5. Ventral roots: motor (efferent) output leaves the cord via ventral roots, which consist of the axons of motor neurons Spinal nerves - formed by joining of dorsal and ventral roots - 31 paird of spinal nerves divided into five groups (2 enlargements: cervical and lumbar) 1. Cervical (8 pairs) 2. Thoracic (12 paris) 3. Lumbar (5 pairs) 4. Sacral (5 pairs) 5. Coccygeal (1 pair)

list four refractive errors and how they are corrected

1. Hyperopia (farsightedness) is the inability to see near objects easily and clearly - eyeball is too short and a far away object is focused behind the retina - the lens accommodates (rounder and thicker) to the far object by increasing the refractive power. now the image falls on the retina - a near object is focused even further behind. the lens cannot accommodate much more, it cannot become more rounder, so the close object cannot be focused. - to correct this, we use a convex lens that increases tractive ability. (glasses) 2. Myopia (nearsightedness) is inability to see objects at a distance - eyeball is too long and a far object is focused in front of the retina. with the relaxed eye (i.e., when the lens is flat), a near object is focused on the retina - a far object cannot be focused though, because a flat, non-accommodated lens cannot become more flatter - to correct this, we use a concave lens that reduces the refractive power. this "pushes" the object back to the retina 3. Presbyopia: the lens becomes stiffer with age and cannot assume a more round configuration. this reduced accommodation and requires vision correction (convex lens) 4. Astigmatism: this is due to an uneven surface of the cornea, which has the effect of focusing an object at two separate places on the retina, producing blurry vision. - corrections for astigmatism: farsightedness (hyperopia): convex lens nearsightedness (myopia): concave lens - these are two spherical lenses that focus into a point - astigmatism is corrected with a cylindrical lens that focuses light into a line instead of a point

Describe the anatomy of the cerebral ventricles

1. Lateral ventricles: right and left, deep in cortex connexted to 2. Third ventricle: within diencephalon, connected in midbrain to: 3. Fourth ventricle: between cerebellum and brainstem (pons and medulla) Meninges: membranous coverings of the brain - dura mater: thickest and toughest, adjacent to skull - arachnoid: middle layer - pia mater: adjacent to brain and spinal cord - all three support the CNS - subarachnoid space, between arachnoid and pia, is where CSF circulates

List the similarities and differences amount the three major types of neurons

1. Multipolar- have multiple densritic processes. Most tract neurons and neurons with peripheral processes are multipolar. 2. Pseudounipolar- have a single "stem" that bifurcates to make distal and proximal processes that project to the target organ and the central nervous system, respectively. This is the typical cell type in dorsal root ganglia (Sensory neurons) 3. Bipolar and unipolar- bipolar have two procesess, mainly associated with the special senses. Unipolar is a type of neuron in which only one process extends from the cell body.

Shortly describe chemical senses

1. Olfaction (smell) - olfactory nerve CN I - seven primary odors: camphor, musk, floral, peppermint, ethereal, pungent, putrid 2. Gustation (taste) - facial nerve CN VII, glossopharyngeal nerve (CN IX), vagus nerve (CN X) - five primary taste qualities: bitter, sour, salty, sweet, umami

Four major classifications of sensory receptors

1. Special: vision, hearing, taste, smell, balance, somatic sensation 2. Superficial: touch, pressure, flutter, vibration, tickle, warmth, cold, itch, pain - receptors are mostly located in skin 3. Deep: proprioception (aka kinesthesia), deep pressure, deep pain - proprioception refers to the sense of position and movement of the body in space. Our brain says, "hey, my hand is up and I'm walking!" - receptors are located in tissues, including deep skin, muscles, skeleton, joints, bones and connective tissue 4. Visceral: hunger, nausea, distention, visceral pain - receptors are located in the pelvis, abdomen, chest and intestines

Memorize the receptor type, axonal type, location, and function

1. free nerve endings - minimally specialized nerve endings - C, A(gamma) - all skin - pain, temperature, crude touch - slow adaptation - high threshold of activation 2. meissner's corpuscles - encapsulated - AB 6-12 um - skin or subcutaneous - vibration - rapid rate of adaptation - low threshold of activation 3. pacinian corpuscles - encapsulated - AB 6-12um - skin or subcutaneous - vibration - rapid rate of adaptation - low threshold of activation 4. merkel's disks - encapsulated - AB - skin or subcutaneous - vibration, static pressure - low threshold of activation 5. Ruffini's corpuscles - encapsulated - AB 6-12um - skin or subcutaneous - vibration or static pressure - slow rate of adaptation - low threshold of activation 6. muscle spindles - highly specialized - Ia and II - muscles, muscle length - both rapid and slow rate of adaptation - low threshold of activation 7. Golgi tendon organs - highly specialized - Ib - tendons, muscle tension - slow rate of adaptation - low threshold of activation 8. joint receptors - minimally - joints, joint position - rapid of adaptation - rapid rate of adaptation - low threshold of activation

Describe the neuronal mechanisms responsible for determining the stimulus type, stimulus intensity, stimulus location and stimulus duration

1. stimulus type: - modality: touch, vision, smell, etc.: 6 sensory systems- 6 modalities - signaled by type of receptor excited - a given receptor best detects the stimulus of one stimulus modality (touch, pain, light, sound, etc.) - always there are several sub modalities (eg. for somatic sensations: light touch, vibration, proprioception, pressure, pain and temperature). also determined by specific receptor - each type of sensory information is passed via a specific pathway ("labeled-line cone") 2. stimulus intensity: - amplitude of the receptor potential - frequency of action potentials - the amplitude of the receptor potential and frequency of action potentials depend on stimulus intensity - the number of axons recruited: frequency of APs is limited, however the stimulus intensity also is coded by the number of axons recruited 3. stimulus location - size of the receptive field - small receptive field gives better location of the sensory stimulus than large receptive field - two pont discrimination reflects the density of innervation - if center of the receptive field has the higher density of receptors than the periphery, then the same stimulus will induce the higher frequency of action potentials in response to stimulation of the center. - by comparing information coming in from several neurons with overlapping receptive fields, the brain can determine the location of the stimulus. - lateral inhibition improves the ability for stimulus location 4. Stimulus duration - type of response - coded by length of time a neuron is activated. - action potentials are generated during all time when a stimulus is present - rapidly adapting receptors are sensitive to speed (velocity) of stimulus - action potentials are generated when the stimulus changes. Plus, the action potential frequency is proportional to the speed of the stimulus, and frequency is zero once speed is zero - this pattern is typical of receptors signaling the sensation of flutter, low frequency vibration and movement of a stimulus across the skin

By looking at a cross-section, identify whether that cross-section is located in the spinal cord, medulla, pons or midbrain

Axons of 3 long tracts cross the midline ("decussation"). Left body is represented in the right cortex, right body is represented in the left cortex. 1. Dorsal column/medial lemniscal tract - crosses in the caudal medulla - conveys touch information - interruption of any part of this pathway will diminish the sense of touch 2. Spinothalamic tract (aka anterolateral system) - crosses in the spinal cord - conveys pain and temperature - interruption of any part of this pathway will diminish the sense of pain and temperature 3. Corticospinal tract (aka pyramidal tract) - crosses in the caudal medulla - controls voluntary movements - interruption of any part of this pathway will produce weakness (if partial damage) or muscle paralysis (if damage is total)

Describe the blood-brain barrier, and list substances that can or cannot cross the bbb

Brain recieves about 15% of the total blood supply CNS requires glucose to produce energy; short term lack of glucose causes neuronal death Blood-brain barrier: unique property of the vascular system in the body- it is found only in the brain and not other system organs - consist of two cell layers: endothelial cells of brain/spinal cord capillaries and glial cells (Astrocytes) - prevents large molecules from entering extracellular fluid; protective effect - lipid soluble substances can cross BBB, but not lipid-insoluble substances - due to this, many drugs cannot cross BBB

List the major division of the brain and describe their general functions

Brainstem, cerebellum, and forebrain 1. Brainstem: - consists of medulla oblongata, pons and midbrian - responsible for basic mechanisms of life: regulation of cv and respiratory functions, sleep and wakefullness, posture and balance, etc. - relays and integrates information from periphery to brain and vise versa - nuclei of most cranial nerves are located in brainstem - central core of the brainstem is the reticular formation, involved in integrating information from all sensory modalities and affecting motor outflow. Biogeneic amine nuclei are located in the reticular formation 2. Cerebellum: - coordinates ongoing movements, and learns new movements - recieves input from all muscles, and other brain regions responsible for movement - two major components - cortex: near surface, output cells from here project mainly to the deep nuclei. - deep nuclei: deeper in cerebellum, neurons in these nuclei provide output from cerebellum 3. Forebrain: - cerebral hemispheres: major divisions of the brain - cerebral cortex: outer shell of gray matter in each hemisphere, about 3 mm thick - fiber bundles connect regions of cerebral cortex and send information from cortex to other brain regions - corpus callosum connects two sides of cortex - pyramidal cells provude output from cortex; other neurons connect local regions of cortex.

define four aphasias: motor, sensory, conduction, and global. describe the characteristics of these four aphasias

Broca's area: 1. Motor aphasia Wernicke's area: 2. Sensory aphasia 3. Conduction aphasia Person is fluent and can comprehend but cannot repeat words well. Also, may substitute wrong words for correct ones. Naming is poor 4. Global aphasia: Includes characteristics of all of the above As discussed, Broca's and Wernicke's areas are located in the LEFT hemisphere Right side of the cortex in language areas influences prosody, the changes in stress, intonation, and rhythm of speech Damage to this area will cause aprosodia (loss of ability to express emotions by modulation of the speech patterns)

Draw and label the parts of the neuron and describe the general functions of each part

Cell body: cell maintenance Dendrites: most synaptic contacts Axon (aka nerve fiber): process from cell body to target Terminals: release of neurotransmitters Synapses or varicosities: release of neurotransmitters

list the pathological signs associated with cerebellar lesion

Cerebellar lesions produce ipsilateral deficits (except for midline lesions) - the main sign is asynergia: movement lack synergy; i.e., there is lack of cooperation between different parts of the body) 1. Decomposition of movement: breakdown of movement into individual parts 2. Dysmetria: inaccurate range and direction of movement. movements overshoot (hypermetria) or undershoot (hypometria) their target 3. Gait ataxia: the presence of abnormal, uncoordinated movements, e.g., wide stance, unsteady walking in gait (resembled drunkeness) 4. Dysdiadochokinesia: inability to perform rapid alternating movements Pathological signs associated with cerebellar damage: 1. intention tremor: oscillations as limb moves toward target 2. hypotonic muscles: due to denervation or loss of the deep cerebellar nuclei 3. nystagmus, vertigo: involuntary repetitive eye movements, illusion of movement 4. dysarthria: difficult or unclear articulation of speech that is otherwise linguistically normal

describe the physiology of the organ of the corti. describe the relationships around the tectorial membrane, hair cells, stereo cilia, basilar membrane, and sensory neurons.

Cochlear nerve (part of CN VIII) and organ or corti: - the sensory apparatus (organ of corti) is relatively small - hair cells, tectorial membrane, stereocilia, nerve fibers, basilar membrane, cochlear nerve - there are 16,000 hair cells in each cochlea.

define "conjugate eye movements", "saccades", "smooth pursuit eye movements", and "nystagmus"

Conjugate eye movements: eyes move in the same direction - three cranial nerves that control eye muscles (III, IV, VI) receive signals from (1) the vestibular nuclei and (2) superior colliculus 1. the vestibular nuclei contribute to conjugate eye movements to compensate for the brief/rapid motions of head 2. the superior colliculus is one of the recipients of direct projections from the retina also controls the conjugate eye movements, but during slow head motions or when we follow the objects with out eyes both (1) V.N. and (2) S.C. also receive projections from the motor cortex to regulate the eye movements. Saccades: fast movement of the eye from one fixation point to another Smooth pursuit: slow movements that track a target across the visual field Nystagmus: involuntary repetitive eye movements. - this makes it impossible for a person to keep the eyes focused on any given object - occurs when the semicircular canals are being stimulated while the head is not in motion (e.g., by disease vertigo) - the direction of ocular movement is related to the semicircular canal that is being stimulated

Cortex, subcortical nuclei, diencephalon, and limbic system:

Cortex is divided into four lobes: - frontal, parietal, occipital, and temporal - inputs to cortex arise from three major regions: thalamus, other regions of cotex, reticular formation - cortex is major integrating region of the brain and is area that makes humans human Subcortical nuclei: - groups of cell bodies deep within hemispheres; the most prominent are the basal ganglia - basal ganglia: caudate nucleus, putamen, globus pallidus - other nuclei associated with basal ganglia: sibstantia nigra, subthalmic nucleus - traditionally known as regions that help control movement, these cell groups also are known to be involved with higher cortical functions, such as cognition and memory Diencephalon: - Thalamus: the major relay station to the cortex. Most sensory inputs from the body must relay through the thalamus before reaching the cortex. Many motor outputs from the cortex also relay here. The thalamus is also involved in arousal and attention - Hypothalamus: this is the major endocrine center and is responsible for controlling body homeostasis Limbic system: Several structures contribute to this system which is responsible for - emotional responses, learning and memory, and integration of autonomic responses with emotional stimulation

define working, explicit, and implicit memory. describe types of memory that are included that are included in each of these broad categories

Declarative (explicit) Immediate: - ability to keep things in mind for fractions of a second as you are pondering something. The basis is synaptic potentials or activity in neuronal circuits. Working (immediate recall) - memory for activities you're doing now - working memory requires prefrontal cortex Short-term: - memory that lasts for minutes to hours - eventually it could be stored or lost - overlaps in time with working memory, but requires hippocampus Long-term: - consolidated memories that can be recalled days, weeks, or years later - divided into two categories: 1. Recent: memories that are up to 2-3 years old - declarative recent memory requires intact medial temporal/diencephalic memory system 2. Remote: memories older than 3 years - declarative remote memory does not require intact medial temporal/diencephalic memory system There are two major types of declarative (explicit) memory 1. Semantic: this is the general basis of knowledge that an individual has, or the memory for facts 2. Episodic: this is the recollection of an individuals experiences as they happened in a place and time, or the memory for events There are four major types of nondeclarative memory: - this category includes memories that are "recalled" unconsciously 1. Procedural 2. Priming 3. Non associative - the person learns aspects of a single stimulus - habituation: the response to stimulus gets smaller - sensitization: the response to a stimulus gets larger (e.g., hyperalgesia) 4. Associative: - classical conditioning: Pavlov's dogs - operant conditioning: positive or negative reinforcement changes the probability of a response (e.g., electrical stimulation of "pleasure centers")

describe the mechanism of depolarization and hyperpolarization of hair cells

Depolarization: - hair cells depolarize when sterecilia bend toward the tallest one. towards kinocilium. - mechanically-gated K+ channels (endolymph: high K+ low Na+; this creates a high "+" charge outside the cell) - when K+ channels open, K+ enters cell, producing depolarization --> upon depolarization Ca2+ enters cell, releasing glutamate --> action potentials are generated in neuronal terminals that innervate hair cells Hyperpolarization: - hair cells hyperpolarize when stereocilia bend toward the shortest ones. away from kinocilium The cochlear nerve innervates the organ of Corti: - inner hair cells (95% of innervation): sensory aparatus - outer hair cells (5% of innervation): these cells enhance the movement of the basilar membrane, thus, amplify the sound signal - the spiral ganglion contains the first order, bipolar neurons - all of the peripheral axons gather together to make the cochlear nerve

forgetting. define anterograde and retrograde amnesia. describe a lesion that can result in each of these types of amnesia

Forgetting is as important as learning. Two pathological aspects of forgetting 1. Inability to forget 2. Pathological forgetting that is called amnesia - anterograde amnesia: inability to learn new information BUT retention of working, long-term, and non-declarative memory. Bilateral medial temporal - retrograde amnesia: inability to retrieve information (cant remember). Typically is caused by lesion/injuries to the cerebral cortex, i.e., to the areas where consolidated long-term memory is stored. How to test a memory loss? 1. Short-term declarative memory: ask questions about evens that happened minutes ago 2. Long-term declarative memory: ask questions about events that happened years ago 3. Short-term and long-term procedural, nondeclarative memory: ask to ride a bike or play a musical instrument

identify the structures that comprise each part of the motor system hierarchy

Highest level: - includes various cortical regions (association, premotor, supplementary motor) that initiate the desire to move - function is to notify lower levels of the desired movements Middle level: - its function is the execute the movement commands intended by the highest level - this involves: (1) selecting the motor programs that are required for the movements and (2) coordinating these programs. Local level: - provides the actual command to contract muscles, at whatever intensity of contraction is specified by the higher centers

describe the mechanisms for horizontal and vertical sound localization

Horizontal sound localization occurs in the superior olivary nucleus Vertical sound localization is a function of the pinna - vertical sound localization is prevented if the pinna is covered up. - apparently, the ear somehow uses a comparison of a direct sound vs reflected sound to determine relative altitude of sound

Define primary and secondary hyperalgesia, and visceral pain

Hyperalgesia: enhanced sensation of pain in response to subsequent stimulu Primary hyperalgesia: enhances sensation of pain at the site of tissue damage Secondary hyperalgesia: enhanced sensation of pain in the undamaged area surrounding the damaged area. Visceral pain: poorly localized diffuse, aching, deep. - it is initiated by stimulation of nociceptors in the pelvis, abdomen, chest and intestines - it is commonly expressed as referred pain, in which the pain is referred to a somatic structure (e.g., during heart attacks, appendicitis, etc.) Referred pain: pain originating in the viscera often feels as if it is localized in a somatic structure

define seven major sleep disorders

Hypersomnia: excessive sleep during periods when you are normally awake - Narcolepsy: irresistible sleep attacks during the day. A person suddenly enters REM sleep without other stages- this suggests the involvement of ACh. patients have a loss of roughly 85-90% of orexin/hypocretin neurons- this suggests the possible cause - Cataplexy: abrupt loss of muscle tone, but full conscious awareness (typically triggered by emotions). loss of orexin/hypocretin neurons is also noted - Sleep paralysis: person becomes paralyzed as they drift into or out of sleep. person is awake, but can't move or talk - Hypnagogic hallucinations: graphic dreams, often frightening, usually auditory or visual, that occur at the sleep onset Insomnia: disorder of initiating or maintaining sleep during normal periods - sleep apnea: periodic cessation of breathing Parasomnia: dysfunction associated with sleep - somnambulism (sleep walking): this occurs in stage 3 of non-REM sleep. No recollection of the episodes. Can perform activities such as dusting, going to the bathroom, even speak incoherently - REM behavior disorder: paralysis of muscles during REM sleep does not occur, and person "acts out" dreams. this can be very violent

List the functions and locations of each of the cranial nerves and their nuclei

I- olfactory nerve - deals with smell - only sensory (Afferent) - olfactory bulb- contains cell bodies of second order sensory neurons, which axons compromise the olfactory tract, and travel to several cortical and subcortical regions II- optic nerve- MIDBRAIN: ROSTRAL - deal with sight - only sensory (afferent) - the optic chiasm is an X-shaped structure formed by the cross axons of the ganglion cells - from the eyeball to the optic chiasm the fiber bundle is called the optic nerve. It enters the brain at the level of posterior deincephalon to form synapses on neurons of the lateral geniculate nucleus (LCN) of the thalamus III- oculomotor nerve - motor (efferent) + sensory (afferent) + PNS - somatic motor components: CN III controls movement of 4 eye muscles: superior rectus (up), medial rectus (toward the midline of the body- adduction), inferior rectus (down) and inferior oblique (up and inward) - orientation of eye muscles help to predict eye movements - in addition, the somatic motor components of this nerve elevate upper eyelid - parasympathetic motor: preganglionic neurons project to ciliary ganglion. Postganglionic neurons constrict pupil (contraction of the circular muscle of the iris) and change lens shape - sensory: contains fibers that transmit sensory information from eye muscle sensory receptors IV- trochlear nerve- MIDBRAIN CAUDAL - motor (efferent) + sensory (afferent) - somatic motor: innervation the superior oblique muscle; it helps to oculomotor to move eyeball downward; and also causes inward rotation of eyeball - sensory: transmits sensory information from eye muscle sensory receptors (similar to oculomotor) - only cranial nerve that crosses the midline before emerging from the brain stem: as a result, lesion of this nucleus affect the contralateral eye (lesions of other cranial nuclei affect the ipsilateral side), and exits dorsally V- trigeminal nerve- MIDBRAIN PONS AND MEDULLA - motor (efferent) + sensory (afferent) - has three branches 1. Ophthalmic (V1): sensory input (pain, temperature, touch) from eye, orbit, forehead, rood of nasal cavity, and frontal sinuses. 2. Maxillary (V2): sensory input (pain, temperature, touch) from upper jaw and overlying skin, nasal cavity, palate and nasopharynx 3. Mandibular (V3): sensory input (pain temperature, touch) from mouth, lower law and anterior 2/3 younger. Motor outflow to chewing muscles VI- abducens nerve - motor (efferent) + sensory (afferent) - somatic motor: innervates lateral rectus and regulates lateral movement of eyeball (abduction) - sensory: from muscle receptors, similar to oculomotor (CN III) VII- facial nerve- PONS CAUDAL - motor (efferent) + sensory (afferent) + PNS - somatic motor: neurons control muscles of facial expression (main function of this nerve) - parasympathetic motor neurons control salivary glands (except parotid) and lacrimal glands (that produce tears) - sensory input from skin on lower part of ear and behind the ear, taste buds from anterior 2/3 of tongue VIII- vistibulocochlear nerve- MEDULLA ROSTRAL - only sensory (afferent) - the human ear IX- glossopharyngeal nerve MEDULLA ROSTRAL - motor (efferent) + sensory (afferent) + PNS - rostral part of the nucleus ambiguus: somatic motor neurons, preganglionic parasympathetic neurons - somatic motor: innervates a muscle involved in elevating the pharynx during swallowing and speech - parasympathetic motor: control of parotid gland - sensory: from carotid sinus (baroreceptors; blood pressure) and carotid bodies (chemoreceptors; blood oxygen levels). From part of ear (pain temp touch). From posterior 1/3 tongue (pain, temp, touch). From upper pharynx (pain, temp, touch) (it is an afferent never ending for gag reflex; pharyngeal reflex) X- vagus nerve MEDULLA MIDDLE Motor (efferent) + sensory (Afferent) + PNS - comprises most of the parasympathetic nervous system - motor component: smooth muscles and glands in pharynx, larynx, thorax, and abdomen (parasympathetic nervous system). Skeletal muscles in pharynx, larynx, and tongue (not all of them)- this is an efferent limb for gag reflex. - sensory component- from all visceral structures innervates by the vagus nerve; also from blood pressure receptors and chemoreceptors in the aortic arch. Parts of the ear, larynx, pharynx, and some taste buds XI- spinal accessory - only somatic motor (efferent) - somatic motor: this nerve control two neck skeletal muscles- sternomastoid and trapezius - cell bodies of motor neurons are actually located in upper cervical spinal cord. Axons emerge from the nucleus, ascend to the medulla and then exit the skull with the vagus nerve XII- Hypoglossal nerve MEDULLA MIDDLE - only somatic (efferent) - somatic motor: controls most of tongue muscles

identify the locations of the area of cortex used in speech. identity Broca's and wernickes areas, and the arcuate fasciculus

Left hemisphere (using right hand)- responds linguistically "ball" Right hemisphere (using left hand)- responds by non-verbal means "something round". Has limited language capacity Broca's area: - located in the LEFT frontal cortex - involved in speech production: organizes motor commands for production of meaningful speech - individuals with damaged Broca's area speak slowly and with difficulty (loss of ability to produce speech), but have little or no difficulty understanding language (motor aphasia) - ex: "the ladies and gentlemen are now all invite into the dinning room" "Ladies, men, room" Wernicke's area: - located in the LEFT temporo-parietal cortex - involved in the comprehension of language - it is the sensory representation of words and symbols - individuals with damaged Wernicke's area cannot comprehend written or spoken language, but their speech is rapid. Usually their speech is effortless and makes no sense (sensory aphasia) - e.g., "where do you live?" "I came there before here and returned there"

Describe how the gate control system works. List four areas from which nociceptive input can be modified. List four ways to prevent or reduce pain.

Modulation of pain: gate theory of pain - this theory states that a neural mechanism in the dorsal form of the spinal cord acts like a gate which can increase or decrease the transmission of action potentials from peripheral fibers to the central nervous system via the spinothalamic tract. Pain can be reduced by: 1. interruption at the level of primary afferents 2. interruption at the level of spinal cord and ascending pathways (thalamus, midbrain, pons, medulla) 3. activating descending inhibitory pathways (hypothalamus, periaqueductal gray, locus coeruleus, raphe magnus)

Describe how myelin is formed, and the function of myelin

Myelin is composed of schwaan cells (periphery) and oligodendroglia (CNS). Nodes of ranvier are located between the myelin-forming cells The conduciton velocity along the axon is accelerated by meylin; the amount of acceleration depends on the size of the axon.

define the characteristic frequency of sensory neurons

Neuronal responses: - neurons respond with a "characteristic frequency" that depends on position of a hair cell on the basilar membrane that this neuron innervates - in addition, for a higher intensity (louder sound), a neuron responds with a greater number of action potentials. this is because a hair cell generates a larger amplitude receptor potential - also, since a louder sound will deform more of the basilar membrane, more neurons will be activated

compare and contrast Non-REM and REM sleep

Non-REM sleep: - ability to arouse proportional to sleep stage (stage 1 easiest, stage 3 hardest) - some muscle tone - some adjusting body movemets - no eye movements - no dreaming - normal autonomic activity, although low (body temperature, blood pressure and respiratory rate decrease) - slow waves are prominent in EEG REM sleep: - most difficult to arouse someone else, easiest for yourself (dreaming) - almost no muscle tone- atonia ("paralyzed muscles") - no movements, except rapid eye movements, muscles of inner ear and diaphragm - REM- rapid eye movements - Dreaming - variable autonomic activity (autonomic storms, no temperature regulation, heart rate and respiration are highly variable) - EEG is desynchronized, alpha and beta waves

If a cranial nerve or nucleus is damaged, describe the functional deficit that will occur

Olfactory nerve- CN I - if damaged: it will affect the sense of smell but also the ability to taste food Optic nerve- CN II - if damaged: vision in the affected eye may be partially or completely lost Oculomotor nerve- CN III - if damaged: loss of control of ipsilateral eye movements, pupil constriction, and upper eyelid elevation Trochlear nerve- CN IV - if damaged: inability to move the eye down and in toward the nose Trigeminal nerve- CN V - if damaged: trouble speaking and chewing Abducens nerve- CN VI - if damaged: loss of eyeball movement, can't abduct properly Facial nerve- CN VII - if damaged: weakness on one side of the face. Can cause problems will opening or closing the eyelid, droopy cheeks, slurred speech or a lopsided smile Vestibular nerve- CN VIII - if damaged: vertigo or a balance disorder, dizziness Glossopharyngeal nerve- CN IX - if damaged: difficulty swallowing, impairment of taste of 1/3 tongue, impaired sensation of 1/3 tongue, absent gag reflex, dysfunction of parotid gland Vagus nerve- CN X - if damaged: affect motor nerve called cranial nerve palsy or affect a sensory nerve causing pain or diminished sensation Spinal accessory nerve- CN XI - if damaged: impairment of function of the sternocleidomastiod and trapezius muscles Hyposglossal nerve- CN XII - if damaged: weakness of wasting of the tongue on the affected side

describe the characteristic deficits associated with Parkinson's disease, Huntington's disease, and ballism

Parkinson's disease is a prototype of hypokinetic disorders - loss of dopaminergic neurons in the substantial nigra. - reduced thalamocortical activity - reduced motor output - treatment: DOPA- replacement of DA Huntingtons disease is a prototype of hyperkinetic disorders - loss of GABA neurons in caudate and putamen - increases thalamocortical activity - increased motor output - treatment: improvement is provided by inhibiting DA synaptic release or DA receptors- this is equal to inactivation of the direct pathway Ballism is another case of hyperkinetic disorders - loss of excitatory neurons in the subthalamic nucleus - increased thalamocortical activity - increased motor output

identify the locations of lesions that will produce Parkinson's disease, Huntington's disease, or ballism

Parkinsons is a lesion in the dopaminergic (DA) axon, resulting in a decreased motor output Huntington's disease is a lesion in Put (putamen) which increases motor outpit Ballism is a lesion in STN which increases motor output

Choroid plexus

Part of lining of ventricles; appears tufted Ependymal cells secrete CSF - CSF circualtes through ventricles and spinal cord, and eventually returns to blood via the arachnoid villi, which are structures that project from the arachnoid to venous sinuses; these work similar to lymphatic vessels. Functions of CSF: - regulates extraceullular environment of neurons - protective function furing brain injuries

define the following terms: primary sensory (or motor) cortex, unimodal sensory (or motor) association cortex, and multimodal association cortex. Identify cortical regions that comprise each of these classifications of cortex

Primary cortex: - the corresponding sensory information is represented in the primary sensory cortex, but you do not have feelings yet. - the primary motor cortex is a representation of motor commands for a movement ("movement execution" once all decisions about the motor output are made) Unimodal association cortex: - integrate information related to a single sense and then interprets the sensory stimulus - for example, the unimodal somatosensory association cortex integrates information related to touch from widespread regions, to determine whether there is a massage or being punched, also shape, texture, etc. - the unimodal visual association cortex integrates information related to vision to determine location, motion and color of objects in the visual field - thus, unimodal sensory association cortex interprets information received from a single sense - unimodal motor association cortex (includes pre motor cortical regions) integrates information related to motor activity Multimodal association cortex: - cortex that "associates" or integrates multiple senses and relates sensory input to motor output (decides how to respond) - posterior association area: integrates information from several sensory modalities to provide a complete depiction of an object (e.g, for a baby's toy, this would integrate the shape, color, texture, smell, sound, location and movement of the object) - limbic association area: this region is concerned with emotional responses and formation of memories - anterior association area: responsible for thinking and planning movement. This area decides what to do in response to sensory input

identify the patterns of activity of the aminergic and cholinergic nuclei during different stages of wakefulness and sleep

REM: - dreams ultimately are the result of activity of ACh neurons in the brainstem - atonia ("muscle paralysis") and rapid eye movement originate in pons - atonia prevents acting out of dreams

Axonal regeneration in humans

Severed axons in PNS can regrow to reinnervate the original target Severed axons in CNS do not regrow to target; they may sprout new endings, but the function is not regained.

identify the structures that comprise the basal ganglia system, and describe the primary functions of the basal ganglia

Structures of the basal ganglia system - thalamus (VA/VL): VA- ventroanterior n. VL- ventrolateral n. (excitatory "Glu") - caudate n. - Put: putamen (inhibitory to GPi "GABA") - GPe: putamen, external (inhibitory to STN) - GPi: globus pallidus, internal (Inhibitory to VA/VL) - STN: subthalamuc n. (excitatory to GPi) - SNc: substantia nigra, pars compacta - SNr: substantia nigra, pars compacta Direct pathway: inhibits thalamus (decreasing motor output) Indirect pathway: disinhibits thalamus (increasing motor output) Functions of Basal Ganglia: 1. initiation of movement 2. selection of movement programs appropriate for task 3. adjustment of body position appropriately for a given task 4. BG controls gross movements, i.e., those that require the whole body movement and which involved the large (core stabilizing) muscles of the body 5. BG is involved in non-declarative memory and learning related to motor activities

describe the general mechanism involving the suprachiasmatic nucleus for defining the rhythm of sleep. describe how the pattern of sleep changes with age

Suprachiasmatic nucleus (SNC) does not control entrance to sleep or arousal from sleep. it synchronizes body activities with the changing cycles of day and night REM sleep highest during development, lowest in elderly Children have more deep (non-REM) sleep, elderly very little deep sleep Overall amount of time spent sleeping declines with age

describe the characteristics of the following disorders: kluver-bucy, depression, bipolar, and schizophrenia

The Kluver-Bucy syndrome has 5 major characteristics: - visual agnosia: psychic blindness- inability to recognize objects by sight alone - increased oral tendencies: the monkeys places everything in their mouth as if they did not know what the object was - increased seeking behavior: the monkeys repetitively examined every object around them - hypersexuality: the monkeys would attempt to copulate with just about anything - docile: personality changes. emotions were flat; loss of the anger and fear responses Depression: - people have a reduced ability to experience please and to even seek pleasurable activities - this is a characteristic of major depressive disorder and anhedonia (inability to feel pleasure) - characterized by withdrawal, sadness, disinterest, lack of pleasure, irritability, anxiety Bipolar: - manic episodes in addition to depression. this is characterized by excessive energy, overconfidence, euphoria and irritability Schizophrenia: - withdrawal, emotionally unresponsive, inappropriate moods, delusions, hallucinations - overactive dopamine pathways contribute to schizophrenia

describe the roles of the amygdala and basal ganglia in behavior and list some examples of diseases related to abnormal amygdala function

The amygdala receives highly processed sensory information (e.g., information from association cortex) from every sense - a major function of the amygdala is to fill up this sensory information with emotional context - the memory of the sensory event is stored in the brain. when this memory is retrieved, the emotion accompanying that memory is also retrieved. The amygdala is required for learned fear - fear is a learned response. without the amygdala, fear cannot be learned. amygdala associates unconditioned stimuli with fear. most of our fears are associated. - stimuli that directly elicit fear reach the amygdala from any pathway for sensation (e.g., electric shock, unexpected loud noise, scary stories), then they are associated with other neutral signals/stimuli The amygdala influences autonomic and somatic responses related to emotional states - the amygdala sends projections to the brain regions that influence autonomic and somatic responses related to emotional states Damage to amygdala: - bilateral damage to the amygdala reduces or eliminates fear. in addition, patients cannot recognize fear in others, although the ability to detect other emotions is normal - the amygdala also is important for processing positive emotions, particularly those associated with rewards - enhanced amygdalar activity is associates with mood and anxiety disorders: major depressive disorder, panic disorder, agoraphobia- fear of places and situations, social anxiety, PTSD, general anxiety disorder The basal ganglia (BG) contribute to selecting appropriate behaviors: - the most well-characterized functions of the BG are related to the motor system. however, there are other pathways through the BG and one of them is associated with limbic functions - this pathway involves: 1. the nucleus accumbens: which is part of the ventral striatum in the BG 2. dopamine: which is the most important neurotransmitter related to reward Disorders related to the basal ganglia circuit: - disorders in the basal ganglia circuit cause a reduced ability to translate motivations into appropriate goal-directed behavior - people have a reduced ability to experience please and to even seek pleasurable activities - this is a characteristic of major depressive disorder and anhedonia (inability to feel pleasure) Psychoactive drugs: - enhance dopaminergic neurotransmission, thus exciting pleasure centers - however, this also disrupts the normal function of the basal ganglia circuitry - the ultimate result is that decision-making with respect to reward and punishment becomes disrupted - thus, the limbic system is important for normal decision-making

describe the processes for storage and retrieval of memories

The cerebellum stores some nondeclarative memories - if conditioned eye blink reflex is developed (e.g., in response to a sound), lesions of the cerebellum will prevent this conditioned response The dorsal striatum stores some nondeclarative procedural memories - lesions to the dorsal striatum will prevent memories on how to ride a bike, to type or to write The medial temporal lobe (MT) is critical for storing new declarative memories - learning represents the development of memory traces or engrams 1. Processed (unimodal and heteromodal) sensory input is relayed to the medial temporal lobe, which consists of the hippocampus, amygdala, and adjacent areas of the medial temporal cortex. 2. The amygdala attaches emotional significance to the sensory input and relays this information to the hippocampus and prefrontal cortex (for short-term and working memories) and frontal cortex (for thoughts and plans) 3. The hippocampus distributes the memory to appropriate regions of cortex (for development of long-term memories). Different aspects of the object are stored in different regions - for example, faces are stored in a part of the visual association cortex - voices associated with those faces are stored in the auditory association cortex - the feelings (whether good or bad) that are associated with seeing and hearing those people are probably stored in the amygdala For working/short-term memories to become long-term, memory "consolidation" must occur. - consolidation is the stabilization of an engram after its initial acquisition. The hippocampus and medial parts of the temporal lobe are required for this process for declarative memories - before memory consolidation occurs, the frontal cortex involves pathways 1 and 2 in retrieval of memory. Presumably, this is the basis for recent long-term memory - after memory is consolidated, the frontal cortex can directly access the memory (pathway 3). Presumably, this is the basis for remote long-term memory - memories probably occur as a result of synaptic plasticity, including changes in excitatory postsynaptic potentials (EPSPs) and protein synthesis

Describe the conceptual differences between the specific sensory pathways (eg. three neuron pathway) and non specific sensory pathways

The function of all sensory systems: transduction of physical or chemical energy into the energy of electrical potentials (sensory transduction) - a receptor responds best to only one sensory modality (e.g., vibration, light, pain, smell, taste, etc.) Receptor potentials ultimately initiate action potentials. - neuron terminals: touch, pain, temperature, and smell - epithelial sensory cells (aka receptor cells): vision hearing, balance, taste. examples are photoreceptor cells (rod and cones) of the retina and hair cells of the cochlea and semicircular canals. Receptor potential: potential caused by a stimulus to a neuronal terminal - stimulus causes opening of ion channels, typically a sodium, potassium, and/or chloride, which elects changes in membrane potential; this is analogous to an ESPS.

describe how the pattern of sleep changes during one night of sleep

The sleep cycle lasts about 90 minutes, and the duration of each stage changes throughout the night - the deep stage of sleep (stage 3) occurs early in the night, in the first 1-3 cycles - REM sleep is of longer duration in the early morning, in the last 1-2 cycles - often we wake up from the REM sleep

Define "sensory unit". Draw a sketch of a typical sensory unit on the index finger, and contrast that with a typical sensory unit of the back

a sensory unit is a sensory neuron along with its branches. - a peripheral afferent neuron is commonly termed a primary afferent because it is the first neuron in the sensory pathway sensory information is conveyed in specific and non-specific ascending pathways specific: transmit specific information (touch, temp, etc.) - leads to a specific determination regarding the site of stimulus non-specific pathways: transmit non-specific information, in effect saying that something happened but you don't know what - typically signals relay through reticular formation (RF): this is the area that integrates input from a wide variety of sensory modalities (RF neurons can respond to multiple sensory modalities- touch sound, etc.) - activation of the RF leads to alerting responses- arousal. - these signals also lead to emotional responses to a stimulus.

define "accommodation." describe how accommodation occurs

change in the refractive power of the lens is called accommodation cornea: most refractive power (~70%), but not adjustable lens: less refractive power (~30%), but adjustable - accommodation occurs when the ciliary muscle contracts. this causes relaxation of Zonular fibers and makes the lens more spherical - the muscle is innervated by the parasympathetic component of the oculomotor nerve (CN III) Unaccommodated: (FARAWAY object) - relaxed ciliary muscle (thin and flat lens) - increased tension of Zonule fibers - refractive power of the lens is lower Accommodated: (NEAR object) - contract ciliary muscle (thicker and rounder lens) - decreased tension of Zonule fibers - refractive power of the lens in higher With the relaxed eye (relaxed ciliary muscle), a faraway object will be focused directly on the retina. however, a near object will focus behind the retina. to focus the near object on the retina, the lens changes its shake.

define the two major types of hearing loss, and the treatments for each

conductive hearing loss: external or middle ear - ear wax, fluid, perforation of tympanic membrane, otosclerosis sensorineural hearing loss: inner ear, hair cells - noise, drugs, tumors, genetic mutations, loss of hair cells caused by the natural aging of the auditory system (presbycusis) central hearing loss: auditory pathways - with injuries up to the cochlear nuclei- there will be degrees of deafness on the ipsilateral side - past the cochlear nuclei- deafness does not occur because the pathway are bilateral tinnitus: ringing in the ears, or perception of sound without a stimulus (but also can be caused by problems not in the auditory system) treatments: hearing aids: with an intact auditory system but with inadequate numbers of hair cells, hearing aids simply amplify the incoming sounds cochlear implants: if hair cells are dead, a cochlear implant has a series of electrodes that directly stimulate the cochlear nerve

define the terms "upper motor neuron" and "lower motor neuron." compare and contrast the signs associated with damage to upper vs. lower motor neurons

damage to lower motoneurons produces different effects than damage to upper motoneurons 1. left motor neuron (LMN) refers to spinal or cranial alfa-motoneurons or nerves: damage causes: - decreased muscle tone - muscle atrophy - fasciculation of muscles or fibrillation of single fibers (due to up regulation of nAChRs) - absence of tendon and stretch reflexes - no Babinski sign (toes curl) Upper motor neurons (UMN): refers to corticospinal neurons or other descending neurons above the spinal cord damage causes: - decreased muscle tone, followed by increased muscle tone (due to loss of cortical inhibitory inputs that control spinal reflexes that involve spindles and GTO) - affects groups of muscle instead of a single muscle - muscle atrophy is rare - enhanced local tendon and stretch reflexes (hyperreflexia; due to loss of cortical inhibitory inputs) - babinski sign present (toes flex- babies under two)

Define "dermatome", and describe the anatomical basis for dermatomes

dermatome is the are of skin enervated by a single somatic nerve. - cervical, thoracic, lumbar and sacral nerves throughout the spinal cord. - V1, V2, V3 of the trigeminal nerve (CN V)

on a diagram of the ear, label the structures

functions: - focus from a large space to a small area of the tympanic membrane - amplification (around 3,000 Hz)

describe the center/surround configuration of ganglion cell receptive fields

ganglion cells have center-surround receptive fields - a visual receptive field of ganglion cells is approx. circular. it consists of the "center" and "periphery".

list the primary structures involved in the limbic system, and describe the general functions of each of these structures

hippocampus: - declarative memory Anterior cingulate cortex & medial prefrontal and orbital cortex: - these cortical areas are responsible for experiencing emotions (feelings) - amygdala attaches emotional significance to events, but you do not actually have feelings until the information reaches these cortical areas ventral striatum: aka nucleus accumbens - this portion of the basal ganglia helps to select the appropriate behavior for a situation, regulates rewrds hypothalamus: - role in autonomic and somatic responses to emotions (e.g., laughing and crying), primary motivations, rewards amygdala: - attaches emotional significance to events mediodarsal n. (MD) - this is the primary thalamic nucleus ("Thalamic Relay") associated with the limbic system

compare and contrast hyperkinetic and hypokinetic disorders. list examples of diseases for each of these classifications

hypokinetic: (low movement) - resting tremor - akinesia: problem with initiation of movements - bradykinesia: slowness of movement - rigidity: stiffness or inflexibility of the muscles hyperkinetic (high movement) - dyskinesia: abnormal, uncontrollable, involuntary movements - chorea: jerky involuntary movements - athetosis: involuntary writhing movements - ballism: abnormal swimming and jerking movements - tics: muscle twitches in the face (Tourettes) - reduced muscular tone

list the structures in the visual pathway from the retina to the occipital cortex. describe how the different portions of the visual receptive diets are transmitted to the occipital cortex. list deficits that can occur with damage to parts of the visual pathways

in the primary visual cortex: - the visual field is represented (visutopic organization) - left and right parts of the visual field are represented in the contralateral cortex - the representation is in the inverted fashion - the representation is disproportional in the retina and visual cortex, the visual field is inverted (rotated 180 degrees) - in the retina, the visual field is reversed from right to left - axons from each nasal hemiretina cross over - axons from each temporal hemiretina stay - each 1/2 of the visual field is projected to the contralateral cortex.

list the eye movement produced by each of the six eye muscles

lateral and medial rectus produce logical eye movements - pairs of eye muscles are wired so that if one muscle is excited to produce a movement, then the muscle that opposes that movement is inhibited. in another eye, the excitation/inhibition occurs in opposite muscles for example: - right eye: lateral rectus is excited, medial rectus is inhibited - left eye: medial rectus is excited, lateral rectus is inhibited - as a result, both eyes will turn to the right

on a diagram of the eye, label the structures

memorize these: - sclera - choroid: highly vascularized tissue - lens: fine-tuned refraction for focusing light on retina - aqueous humor - cornea: transparent external surface, major refractive component - pupi - iris: consists of two muscles, circular (PNS) and radial (SNS); pupillary diameter depends on activity of these muscles - ciliar muscle: this muscle controls thickness of lens during accommodation - zonular fibers - retina - optic disk - where blood vessels enter the eyeball - fovea centralis: center of macula (0.35mm in diameter); only cones are found here; the area of the highest activity - macula: center area of retina (5mm in diameter); site where light falls if one looks straight ahead - vitreous humor

describe the structure of the basilar membrane and list the areas of the basilar membrane that are sensitive to low and high frequency sounds

movement of perilymph causes displacement of the basilar membrane movement: oval window --> perilymph --> Reissners membrane --> endolymph --> basilar membrane then movement of perilymph is suppressed at the round window the basilar membrane has a tonotopic organization - apex: wide and floppy: more flexible - base: narrow and stiff: less flexible - thus, the cochlea acts as mechanical frequency analyzer

identify the major functions of the dorsal and ventral pathways from the primary visual cortex.

neurons in primary visual cortex respond to different aspect of visual field: neuronal responses: motion, shape, color. the neurons are organized in cortical columns with about 2mm of cortex per side - each column is responsible for analyzing a particular point in space - each column has the ability to determine all of the important information of its territory: shape, motion, and color - microcolumns encode similar features - information from these columns is sensory to the higher order associated cortex, where the information from each individual column is combined into objects. the dorsal pathway conveys "where" information and the ventral pathway coveys "what" information - dorsal "where?" pathway is involved with detecting the location of objects in space, detection of motion of objects and also is involved with visually guided movements - bilateral lesions of the dorsal pathway make it impossible to perceive a moving object (akinetopsia) - ventral (what?) pathway is involved with the identification of objects. areas of cortex in this pathway help to assemble visual information into recognizable objects - lesions in this region can lead to loss of color perception (achroma tops), loss of the ability to name objects (anomia), or loss of the ability to recognize familiar faces (prosopagnosia)

Define the two components of pain, and the afferent fibers that transmit them. List five chemicals that can sensitize nociceptors

nociception: is a chain of events in the CNS initiated when specialized sensory receptors (nociceptors) are activated by harmful or potentially harmful stimuli (chemical, mechanical or thermal). Nociception triggers a variety of physiological and behavioral responses. - pain is a perception of an aversive or unpleasant sensation Several other chemicals are released following tissue damage and sensitive (i.e., increase the sensitivity) of nociceptors: - bradykinin, serotonin, histamine, prostaglandins, cytokines

describe the mechanism of phototransduction

phototransduction converts light into a chemical signal and then into an electrical signal ultimate result of phototransduction is change in release of neurotransmitter - guanylyl cyclase: converts GTP into cGMP - Na+/Ca2+ channel releases positive change into cell (dark current). opened by cGMP - cation channel closes with light - phosphodiesterase - transducin - retinal (light absorbing molecule) - photopigment (opsin) absorption of light hyperpolarizes the photoreceptor cell: - membrane potential at dark is depolarized. it is -40mV. - a neurotransmitter, glutamate, is continuously released - light closes the channel, and this causes cell hyperpolarization - as a result, a photoreceptor releases less glutamate

identify the locations of primary and secondary auditory cortices

primary auditory cortex: - is located in the superior portion of the temporal lobe - integrates the auditory information for perception - neurons have a tonotopic arrangement - some neurons are tuned to intensity secondary auditory cortex: - surrounds the primary auditory cortex - provides interpretation of complex sounds - is part of Wernicke's area, which is important for understanding human speech

define "refraction," and list the two parts of the eye which produce refraction. identify which of these two structures produces greater refraction

refraction occurs at two sites: cornea (~70%) and lens (30%) - the principle of eye function is the formation of focused image on the retina - this occurs because of the refraction (bending) of the light

list the major structures in the central vestibular pathways

scarpa's ganglion contains bipolar sensory neurons - its spiral ganglion in the auditory system, CN VIII Major vestibular pathways: 1. three cranial nerves: control the eye movements (III, IV, VI) - pathways from the vestibular nuclei connect nuclei of these 3 cranial nerves to coordinate eye movements 2. some neurons descend to spinal alpha-motor neurons via vestibulospinal tract 3. some neurons project to ventral posterior (VP) nucleus of the thalamus, when then send projections to the vestibular cortex 4. some neurons project to the cerebellum

describe the function and operation of the Golgi tendon organ

the Golgi tendon organ senses muscle force (not length): - consists of a capsule containing the branches of sensory fibers that are connected to collagen fibers of the tendon - the number of action potentials is proportional to the amount of tension, or force, on the tendons, and therefore the muscle - Golgi tendon organs are part of the tendon reflex that operates as a negative feedback loop to regulate muscle tension (force)

describe the primary function of the cerebellum

the cerebellum receives input from sensory receptors in muscles and skin and from special senses. however, lesions of cerebellum do not produce sensory deficits or muscle weakness - instead, cerebellar lesions produce deficits in: coordination of movements, muscle tone, posture. the primary functions of the cerebellum are 1. coordination of ongoing movements and 2. error correction (smooth execution and appropriate completion of ongoing movements)

identify the locations and functions of the cortical regions that give rise to the corticospinal tract

the cerebral cortical motor regions control voluntary movements 1. motor cortex: cortical areas that produce movements when electrically stimulated. they control voluntary movements - primary motor cortex: somatotropin organization, representation of the body is contralateral, representation is disproportional, low intensity electrical stimulation produces focal movements that can be limited to a single muscle (e.g., muscle of a finger) - is what people usually think of when they think of motor cortex. located anterior of central sulcus- in the precentral gyrus - produces movement execution - provides contralateral control of unilateral movements - controls fractionated movements (i.e., movements across a single join such as fingers and hands) - receives input from the complementary (i.e., similar) region of the somatosensory cortex; therefore, primary motor cortical neurons have somatic receptive fields that allows them to rapidly respond to a sensory stimulus. 2. premotor cortex: - also has somatic organization, but less than the primary - electrical stimulation also produced movements. however: this required the intensity of stimulation higher than that to evoke the movements when stimulation the primary motor cortex. larger muscle groups are generally excited. - supplementary motor cortex: controls both sides of the body - located on the medial side of cerebral hemisphere - somatotopic organization (but less than the primary) - "plans big picture" - coordinates bimanual movements, learns new movement sequences and rehearses them (including mental rehearsal), adjusts posture when we move (e.g., when lifting a weight) - these functions explain the bilateral representation in the supplementary motor cortex. - lateral premotor cortex: "goal-directed movements" - located on the lateral side of the cerebral hemisphere - somatotopic organization (but less than the primary) - plans goal- directed movements, particularly reaching and grasping objects. - organizes movements based on environmental cues- visually guided movements - adjusts posture needed for a movement - cingulate motor cortex: not much is known but this region may have similar functions to supplementary motor (medial premotor) cortex - frontal eye field: together with the superior colliculus, it controls voluntary saccadic eye movements (from one fixation to another) electrical stimulation of the FEF on one side causes saccades on the opposite side. damage to this area, by stroke, trauma, or infection causes tonic deviation of the eyes towards the side of the injury Somatosensory cortex: - relays touch signal to the complementary motor region - descending output from the somatosensory cortex to the spinal cord modulates sensory input that ultimately influences the motor activity (e.g.m can reduce pain transmission during a fight or flight response so the individual can concentrate on the motor response without being bothered by pain) Parietal lobe: - receives inputs from the somatosensory and premotor cortex - it also is the destination of the dorsal "where" pathway from visual cortex. the parietal lobe serves as the sensory processing center for organization of visually guided movements (i.e., movements in relation to objects in the environment) - parietal lobe sends projections to the lateral premotor cortex that serves as a center for organization of the motor activity in relation to visually guided movements.

Identify the structures of the dorsal column- medial lemniscal system, spinothalamic system, and trigeminal system. Compare and contrast the anatomy and functions of these three systems. Identify the location and sensory modality on the body and head that are lost following lesions in the spinal cord or brain that damage one of these three systems

the dorsal column- medial lemniscal system coveys "touch" information from the body. - sensory fibers (primary afferents) enter spinal cord along its whole length, and ascend in the dorsal columns on the same side - lower half of body, fibers make up the gracile fasciculis - upper half of body, fibers make up the cuneate fasciculus - axons exiting the gracile and cuneate nuclei cross to the opposite side, and ascend to the thalamus in the medial lemniscus - fibers in medial lemniscus synapse on cell bodies ventroposterior lateral nucleus of thalamus - fibers exiting the ventroposterior lateral nucleus ascend to synapse on cell bodies in the somatosensory cortex. termination sites are somatopically organized. the somatosensory cortex is located in the anterior portion of the parietal lobe. - somatotopic organization: the body is represented in the cortex. the spinothalamic system (aka anterolateral system) conveys pain and temperature from the body - projects similar cortical area as the DC/ML system - spinothalamic axons immediately cross to the opposite side to ascend in the ventrolateral quadrant of the spinal cord in the spinothalamic tract. - fibers ascend throughout the brainstem in the sponothalamic tract - fibers in the spinothalamic tract synapse on cell bodies in the ventroposterior lateral nucleus of thalamus - fibers exiting the ventroposterior lateral nucleus ascend to synapse on cell bodies in the somatosensory cortex. termination sites are somatotopically organized the trigeminal system conveys sensory information from the face 1. Non-nociceptive (touch) information: - primary afferents synapse on neurons in the trigeminal main sensory nucleus - axons leaving the main sensory nucleus cross to the opposite side and ascend to synapse on cell bodies in the ventroposterior medial nucleus of the thalamus - fibers exiting the ventroposterior medial nucleus ascend to synapse on cel bodies in the face region of the somatosensory cortex. 2. Nociceptive information: - primary afferents synapse on neurons in the spinal trigeminal nucleus - axons leaving the spinal bigeminal nucleus cross to the opposite side and ascend to synapse on cell bodies in the ventroposterior medial nucleus of the thalamus - fibers exiting the ventroposterior medial nucleus ascend to synapse on cell bodies in the face region of the somatosensory cortex.

identify the reward centers in the brain, and the primary neurotransmitter associated with these centers

the hypothalamus regulates primary motivations or drives: - motivation is the general desire or willingness of someone to do something. there are two types of motivations: primary (or drives) and secondary Primary motivations: drives; are regulated by the hypothalamus - these motivations are related to biologic functions that ensure the survival of the individual and the species - they are related to homeostatic mechanisms: feeding and drinking, fighting or fleeing, temperature regulation, sex Secondary motivations: derived from primary drives - what to eat, what to drink, what clothes to put on, etc. - most human behaviors consists of the secondary motivations - the selection of secondary motivations is regulated by a circuit that includes the hypothalamus and prefrontal and cingulate cortices. There are four major reward areas in the brain: 1. septal area 2. lateral hypothalamus 3. ventral tegmental area 4. dorsal pons - if an electrode is impacted into the lateral hypothalamus and an animal has accesses to electrical stimulation, it will be pressing a bar 2000 times per hour until exhausted. Basal ganglia: Conceptually this circuit works in the following way: - dopamine enhances activity in the direct pathway: this stimulates activities that leads to rewards - dopamine reduced activity in the indirect pathway: this reduces activities that lead to punishments - however, for the rewards, the ventral striatum- nucleus accumbens- is involved (and not the dorsal striatum) - dopamine, therefore, is one of the most important neurotransmitters related to moods.

list four primary functions of the limbic system and provide an example of each

the limbic system has four primary functions: 1. olfaction: - smells have emotional significance - the limbic system has connections with olfactory system 2. emotional processing: - all sensory inputs reach the limbic system, which then fills up this sensory information with emotional context - limbic system provides behavioral and motor outputs (i.e., organizes emotional and motor responses to sensory stimuli) - limbic system controls drives, seeking rewards, and avoiding punishments 3. memory: - limbic system is required for consolidation of declarative memories - limbic system attaches emotional significance to memories 4. homeostatic functions: - hypothalamus, some parts of which belong to the limbic system, regulates the autonomic nervous system - hypothalamus regulates endocrine functions

describe the function and operation of the muscle spindle. describe the effects of gamma motoneurons on spindle function

the muscle spindle senses muscle length - regular skeletal muscle fibers are called extrafusal fibers. they are innervated by alpha-motoneurons - muscle spindles consist of specialized muscle fibers- intrafusal fibers. they are innervated by gamma-motoneurons lengthening the spindle increases action potentials (in the alpha motor neuron) - the larger the amount of stretch, the greater the number of action potentials - muscle spindles are part of the stretch reflex that operates as a negative feedback loop to regulate muscle length - the parameters (i.e., relaxation and contraction) of extrafusal and intrafusal fibers must match each other - if not a supporting mechanism, the muscle spindles would not responsive when the muscle is fully contracted or fully relaxed. Gamma motoneurons set the sensitivity of the spindle: - during actual movements, alpha-motoneurons and gamma-motoneurons are activated at the same time. this scales the cell activities - by changing the activity of gamma-motor neurons, the CNS adjust the sensitivity of spindles to the level that is appropriate for the forthcoming movement

identify examples of substances that can induce sleepiness, and the primary substance thought to initiate sleep

the precise mechanisms for falling asleep are not known, but there are many sleep approaches and substances that influence sleep - reduction of sensory input (e.g., turning off lights, ear plugs, eye mask) helps you fall asleep - there are more than 30 factors that are associated with sleep. when they occur in high concentrations, then people tend to sleep - there is no single "most important" factor but adenosine is important for the "sleep drive". it accumulates throughout the day in the ventrolateral preoptic area (VLPO) in the hypothalamic and excites the GABA neurons in VLPO - there is a connection between sleep and the immune system A variety of substances produce sleepiness: a. Muramyl peptides b. Growth hormone releasing hormone c. Prostaglandin D2 d. Interleukin 1 (when fighting an infection, you sleep more)

Describe how receptors signal changes in the environment

the sensory information is transmitted to the cerebral cortex: - most of the signals are filtered and do not reach out consciousness - if the cortex believes that the information is relevant, then the information reaches consciousness and becomes a sensation (physical feeling) - the individual will interpret the significance of the sensation, and this becomes the perception. perception: a mental impression. this is a way of regarding, understanding, or interpreting the sensation. - a given person can respond to the same stimulus in different wats depending on the state of the body and the environment. - the sensory information is identical, but the intimate perception can be different.

sketch the circuits for the stretch, tendon, withdrawal, and crossed extensor reflexes. identify which of these reflexes is the only monosynaptic reflex.

the stretch reflex regulates muscle length, is the fastest and the only monosynaptic reflex: Sequence: muscle lengthens --> spindles stretch --> activation of Ia (or II) fibers --> excitation of alpha- motoneurons monosynaptically --> muscle contraction - activation of either monosynaptically or via excitatory interneurons, of other synergistic muscles (muscles with the same function, such as extension) - inhibition, via inhibitory interneurons, of the antagonistic muscles (muscle with the opposite function, such as flexion) - branches of Ia and II fibers also ascend to higher centers to inform brain of status of muscle length the tendon reflex helps to regulate muscle force: muscle tension increases --> GTO is activated --> activation of Ib fibers --> activation of inhibitory interneurons --> inhibition of alpha-motoneurons --> muscle relaxes - inhibition, via inhibitory interneurons, of other synergistic muscles (extensors) - activation, via excitatory interneurons, of the antagonistic muscles (flexors) - branches of Ib fibers also ascend to higher brain centers to provide information on muscle tension (force) the withdrawal and crossed extensor reflexes are protective - sequence for withdrawal reflex: activation of pain fibers (flexor reflex afferents) --> excitation of excitatory interneurons innervating flexor alpha-motoneurons innervating extensor alpha-motoneurons --> withdraws from the painful stimulus - sequence for crossed extensor reflex: on opposite side of the flexion response, activation of pain fibers (flexor reflex afferents) --> excitation of excitatory interneurons innervating extensor alpha-motoneurons and inhibitory interneurons innervating flexor alpha-motoneurons --> the center of gravity is moved to this side of the body

describe the general anatomy and physiology of the three major functional regions of the cerebellum. list the cerebellar deep nuclei associated with each functional region

the three functional groups are 1. spinocerebellum: control of body and limb movements 2. cerebrocerebellum: planning, initiation and timing of movements, but also memory and learning 3. vestibulocerebellum: posture and equilibrium

describe the anatomy and physiology of the otolith organs

the utricle and saccule are the otolith organs - responding to: linear acceleration of the head, static head positions (e.g., head tilt) otoliths or otoconia: crystals of calcium carbonate, that make the membrane heavier, so that the otolithic membrane can be more easily displaced - when the head moves, this results in a change in the force of gravity to the head. the change in gravity causes the otoliths to move. depolarization if movement is toward the kinocilium and hyperpolarize if the reverse all cells on right side of tilted picture are DEpolarized all cells on the left side of tilted picture are HYPERpolarized utricle is mainly oriented horizontally and the saccule vertically - these organs are capable of transmitting information about liner force in any direction - striola seperated the two halves vestibular neurons are characterized by a relatively high level of spontaneous neuronal activity. this level changes during head tilts or linear accelerations

vestibular system

the vestibular system in mammals is the sensory system that provides the sense of balance and spatial orientation 1. proprioception: senses of posture and balance by monitoring the movements and positions of body and head. also, spatial orientation 2. motor control: adjustment of muscular contraction to maintain posture and balance 3. vestibuloocular reflex: adjustment of eye movements so that a visual target remains on retina in response to head movements sensory cells: hair cells fluids: endolymph, perilymph movement of hair cell processes (cilia) changes frequency of action potentials in associated nerve terminals in a Manny similar to cochlear mechanisms

identify the structures in the vestibuloocular reflex, and describe the mechanism of this reflex

the vestibuloocular reflex coordinates head and eye movements - this is the reflex that maintains a visual image on the retina during brief/rapid head turning - it does this by automatically adjusting eye position for the movement of the head - if the head turns to the left, the eyes will move to the right - this includes the coordinated contraction and relaxation of eye muscles on both sides.

list the brainstem descending pathways that make up the lateral and medial systems. identify the general functions of the medial and lateral systems pathways

there are two major lateral pathways (lateral pathways mainly control muscles of arms and legs, thus, control fine dexterous movements): one direct and one indirect 1. corticospinal tract (aka lateral cut) - mainly crossed (85%) - mainly excites flexors and inhibits extensors in distal limbs and sights 2. rubrospinal tract - crossed - mainly excites flexors and inhibits extensors in proximal limbs there is one direct medial pathway: 1. ventral CST: - medial pathway crosses the midline in the spinal cord and innervates neck, shoulders and trunk muscles - primarily influences posture there are two major indirect medial pathways: 1. vestibulospinal tract: - uncrossed - mainly excites extensors and inhibits flexors 2. reticulospinal tract - uncrossed (mainly) and crossed (contralateral) - pontine reticulospinal tract mainly excites extensors and inhibits flexors - medullary reticulospinal tract mainly excites flexors and inhibits extensors

sketch the pathway for the blink reflex, and describe how this reflex works

touching the cornea causes the corneal blink reflex - this reflex is consensual the blink reflex can be initiated by: - touching cornea (trigeminal; CN V) - bright light (optic nerve; CN II) - loud sounds (vestibulocochlear nerve; CN VIII)

list three vestibular disorders

vertigo: illusion of movement, typically spinning. it is usually worse when the head is moving Meniere's disease: excessive endolymph production causes excessive force on hair cells and their damage - the result can be: deafness, tinnitus, vertigo motion sickenss: caused by mismatch between sensory signals (for example vestibular and visual) Nystagmus: involuntary repetitive eye movements. occurs with all of the above disorders

define "visual acuity," and identify the area of the retina with the greatest and least acuity

visual activity is a measure of the ability to distinguish two points - the greater the number of photoreceptors, and the better the refractive ability of the higher, the higher the acuity - 20/20 vision: you can see at 20 feet (the first number) what a person with normal vision can see at 20 feet (the second number) - 20/40 vision: you can see at 20 feet what a person with normal vision can see at 40 feet - in addition, the visual field is dividing into the 360 degrees of a circle. for 20/20 vision you can see an object that takes up about 0.083 degrees of space both eyes can see about 120 degrees; each eye can see another 30 degrees on its side. fovea has the greatest acuity (2 degrees) macular (15 degrees) near peripheral (50 degrees) peripheral (180 degrees)

sketch the pathway of the pupillary light reflex, and describe how this reflex works. list the characteristic deficits to this reflex with damage to the optic nerve or oculomotor nerve

visual reflexes- mitosis in response to light - decrease in diameter of the pupil of the eye in response to light, circular muscle constriction causes pupillary diameter to decrease (mitosis) - light shone into one eye will cause pupillary constriction in both eyes. this reflex is therefore said to be consensual. constriction of the pupil in which the light is shone is termed the direct response, and constriction of the other pupil is termed the consensual response - ipsilateral and contralateral nuclei containing preganglionic cell bodies of parasympathetic motor neurons of the oculomotor nerve (CN III) radial muscle constriction produced puillary dilation (mydriasis) - intermediolateral nucleus of the spinal cord (upper throacic region) contains preganglionic sympathetic neurons - sympathetic activation, such as the fight or flight response, will result in puillary dialation