Exam 3 Lectures - exam studying notes PDF

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SENSORY PATHWAYS ● Coding of stimulus location ○ Fingers, hands, and face, are very good at two-point discrimination ● Dorsal Columns carry 2 point discrimination to S1 in postcentral gyrus of parietal lobe(ascending) ○ Tracts ■ Fasciculus Gracilis for lower extremity,Fasciculus Cuneatus for upper extremity ● 1st order neurons ● Ascend ipsilaterally ● Synapse and cross in medulla ○ Gracilis synapses in nucleus gracilis ○ Cuneatus synapses in nucleus cuneatus ■ Medial Lemniscus ● 2nd order neurons ● From dorsal column nucleus up to thalamus ● Ascends to thalamus + synapses in thalamus ■ 3rd order neurons ascend (internal capsule) to s1 ● Common area for stroke ○ Thalamus is major sensory relay center ○ Info transmitted ■ Conscious proprioception ■ Discriminative touch ■ Pressure ○ Receptors ■ Mechanoreceptors ○ Very direct pathway ● Anterolateral System(ascending) ○ First order neuron is afferent ○ Second order is in spinal cord ○ Tracts ■ Spinothalamic ● Spinal cord to thalamus ● PAIN information ■ Spinotectal ● Spinal cord to midbrain roof ● Eye movements ■ Spinoreticular ● Spinal cord to reticular formation ● Covers medulla pons and midbrain ● Role in movement control and tone ■ First order neurons synapse with second order neurons in the spinal cord and cross before ascending ○ Info Transmitted ■ Pain ■ Temperature ■ Crude touch ● Hard to localize ○ Very Divergent ■ Information projects to reticular foramen ● Cortex ○ Somatosensory Cortex: Postcentral Gyrus ● Stereognosis ○ Quick clinical screen of sensory function ● Pain ○ Receptors are free nerve endings ■ Slower-conducting afferents(unmyelinated usually) ■ Project elsewhere in cord and brainstem, as well as to thalamus and cortex

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○ Pain afferents release transmitter Substance P ○ Info relayed via anterolateral system Analgesic System ○ Stimulation of certain areas in cord and brainstem produce analgesia(pain relief) ■ Substantia gelatinosa (spinal cord) ■ Raphe magnus nucleus (medulla) ■ Periaqueductal grey (midbrain) ○ Opiate neurotransmitter ■ Released by descending analgesic neurons ■ Block substance P release ○ Endorphins block calcium Nervous system organization ○ Each system contains synaptic relays ○ Each systems is composed of several distinct pathways ○ Each system is topographically organized ○ Most pathways cross the midline and are bilaterally symmetrical ■ Exception of vision

MOTOR CONTROL ● Vestibular system ○ Inner ear ○ Balance and posture require continuous info about position and motion of all body parts ○ Has static and dynamic equilibrium ○ Receptors are hair cells ■ Type of mechanoreceptor ■ Have stereocilia ■ Head makes them bend, firing potentials ○ Static equilibrium ■ Head tilt and position ■ Transduced by hair cells of utricle ○ Dynamic equilibrium(rate of change of movement) ■ Linear acceleration/deceleration ● Transduced by utricle(horizontal) and saccule(vertical) ■ Angular acceleration/deceleration ● Transduced by semicircular canals ○ Vestibular System neural pathway ■ Stimulation of hair cells in vestibular apparatus activates sensory neurons of CN8(vestibulocochlear) ■ Sensory fibers transmit impulses to cerebellum and vestibular nuclei of medulla ■ Projection to oculomotor center ● Neurons in oculomotor enter control eye movements ● Control of Movement ○ Control of movement must control both tonic(background tone) and phasic contractions(reaching out and touching the nose) ○ Three classes ■ Reflex(knee jerk, flexor withdrawal, programmed by lower center like spinal cord, hard to control) ■ Rhythmic(hopping, stereotypic movement, same basic movement over and over, walking, hopping, running, swimming) ■ Voluntary(planned movements, goal oriented) ● Motor control hierarchy ○ Higher centers ■ Decision making ■ Supplementary motor area and motor association cortex ○ Middle level( coordinator) ■ Convert commands ■ May specify individual postures and movements ■ M1( primary motor cortex) , Basal ganglia(nuclei), Thalamus, brainstem ○ Local Level (operator) ■ Specify regional movement ■ Levels of brainstem and spinal cord ■ Reflexes ● Spinal cord: local segmental control ○ Proprioception ○ Innervation of skeletal muscle (extrafusal(contract to perform movement) + intrafusal) ■ Motor ● Alpha and gamma(innervate muscle spindle, two ends contract to stretch middle) motor neurons ○ Muscle spindles are length detectors ■ Transduce both static length and rate of change of length of stretched muscle ■ Sensory ● Afferents from proprioceptors ■ Receptors

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● Muscle spindles = intrafusal muscle ● Golgi tendon organs ● Others Alpha-Gamma Coactivation ○ Extrafusal Muscle(contractile muscle) ■ Alpha motor neurons ○ Intrafusal Muscle(spindle) ■ Gamma motor neurons (striated ends are innervated) ■ Sensory afferents ○ Co-activation of gamma motor neurons(innervating spindle fibers) causes ■ Contractile ends of spindle to shorten ■ Biases muscle spindle keeping it responsive at all muscle lengths Knee Jerk (deep tendon; stretch) Reflex ○ Stretch extensor muscle(only in spinal cord not up to brain, monosynaptic) ■ Extensor muscle spindle receptors activated ● Activate motor neurons to extensor muscle ○ Extensor muscle contracts ● Activate interneuron to flexor muscle ○ Inhibit motor neuron to flexor muscle ■ Flexor muscle reflexes Tension Monitoring Systems ○ Golgi tendon organs ■ Located in the tendons ■ Monitor tension in tendons ● Tension can be created by stretching and contracting ■ Respond most to tension on the tendon due to contracting muscle ■ Activation of GTOs can cause ● Inhibition of the contracting muscle and its synergists ● Activation of antagonistic muscles ● Interneurons involved Ascending Pathway ○ Information from proprioceptors travels in dorsal column system Role of proprioceptors ○ Feedback control and conscious awareness Spinal cord level: local segmental control ○ Spinal reflexes ■ Deep tendon reflex (knee jerk or stretch reflex) ■ Flexor withdrawal ■ Flexor withdrawal w/ crossed extension ● Painful stimulus at nociceptor ● Withdraw ipsilateral leg ● Extension of contralateral leg(opposite side of the body) ○ Crossed extensor reflex ○ Central pattern generator ■ Hard-wired for rhythmic stereotyped movements ● Spinal cat can walk on treadmill ● Spinal dog has scratch reflex ● Neonatal stepping reflex

MOTOR CONTROL II ● Middle level of movement control ○ Subcortical and brainstem nuclei influence movement ○ Two groups(descending) ■ Dorsolateral ● Lateral corticospinal ○ Controls fine movements of fingers ○ Damage affects fine distal goal oriented and exploratory movements ● Rubrospinal ○ Influences motor neurons innervating more distal muscles (wrist arm leg) ■ Ventromedial ● Anterior(ventral) corticospinal ○ M1 to spinal cord (neurons to axial muscles) ● Reticulospinal ○ Reticular foramen to spinal cord ● Vestibulospinal ○ Originates in vestibular nuclei and projects into spinal cord ● Tectospinal ○ Originates in midbrain tecture(roof = superior and inferior colliculi ● Functions of VM ○ Control axial and proximal muscle ■ Postural control ■ Equilibrium ■ Reticular Formation( core of grey matter in midbrain) ● Background facilitation of antigravity muscles’ tone via reticulospinal tract ○ Muscles that fight gravity(extensors in lower body, and flexors in upper body) ● Damage to cortex can release this facilitation from cortical inhibition causing spasticity ○ Internal capsule stroke ■ Disorders of tone: Spasticity ● Seen with interruption of descending pathways to spinal cord ○ Stroke and cerebral palsy ● Clasp-knife phenomenon seen in rapid stretch to spastic muscle ● Why? Inhibitory cortical input to brainstem/reticular formation centers normally modulates tone. Interruption of inputs releases brainstem facilitatory centers from inhibition ○ Strong facilitation of transmission in monosynaptic reflex pathway from Ia sensory fibers to alpha motor neurons ■ Basal Ganglia(basal nuclei) ● Nuclei important in motor control ○ Caudate, putamen, globus pallidus ● Receive input from cortex, thalamus, substantia nigra ● Caudate and putamen ● Lesions here cause bradykinesia(decrease speed of movement), changes in muscle tone, and abnormal involuntary movements. ○ Parkinson’s disease ■ Destruction of nigrostriatal pathway (substantia nigra to caudate/putamen) ● Loss of dopaminergic neurons ● Bradykinesia, akinesia, mask, resting tremor, festinating gait, high tone: cogwheel rigidity ○ Huntington’s disease ■ More rapid than ballismus, affects all parts of body

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Ballismus ■ Originates proximally and uses limb as a whip Cerebellum(comparator) ● Functions ○ initiation , timing, coordination of movements ○ Motor learning ○ Motor planning ● Diseases/ablations typically causes disorders seen upon movement ○ Ataxia(wide gait) ○ Incoordination ○ Overshoot/undershoot ○ Intention tremor(tremor upon movement) Primary motor cortex ● Middle level of movement control ○ Precentral gyrus ○ Somatotopic organization - motor homunculus ● Recall Middle level (coordinator) ○ Convert commands and can specify individual postures and movements Primitive reflexes ● Present in infants ○ May be present with cerebral palsy, post stroke, and traumatic brain lesions ● As frontal lobes develop, they disappear ○ Development includes myelination of pyramidal(Corticospinal) tracts ● Examples ○ Rooting ○ Grasp ○ Startle ○ Tonic neck Highest level of motor control ● Premotor cortex ○ Complex strategies, motor preparation ● Supplementary motor cortex (association) ○ Motor planning (complex sequences) ● Posterior parietal cortex ○ Visual info for targeted movements

VISION ● Intro ○

Visual system transforms transient light stimuli on retina which constructs a stable 3D world Transformational process is creative and entirely dependent upon experience Not only receptors have receptive fields One transmitter can have two responses

○ ○ ○ ● Vision ○ Photoreceptors transduce energy in electromagnetic spectrum in receptor potentials ■ Visible spectrum is 400-700 nm ○ Neurons in the retina contribute fibers that are gathered together at the optic disk where they exit as the optic nerve ● Receptive Field ○ Position in visual space from which light stimuli will alter the activity of the visual cell ○ Can also be described as that region of the retina where the action of light alters the firing of the neuron ○ Retina receptive fields map visual world ○ The receptive field for a specific visual receptor is always the same specific location in your visual field T/F ■ True ○ Light stimuli from different location in your visual world will activate receptors occupying different locations on your retina ○ DIFFERENT PLACES IN VISUAL WORLD ACTIVATE DIFFERENT RECEPTORS ON THE RETINA ● Overview of visual pathway anatomy ○ Hierarchically arranged ■ Receptors (transduction) ● Rods and cones ○ Horizontal cells ■ LATERAL INHIBITION ● graded ■ Bipolar cells ● Amacrine cells ● graded ■ Retinal ganglion cells(axons enter optic nerve) ● M and P cells → superior colliculus ○ M cells are wired to rods ■ Low light and movement ○ P cells are wired to cones ■ Cones transduce color and help with form and depth ● Can do action potentials ● Activate thalamus ■ Thalamus - lateral geniculate nucleus ● M pathway, P blob pathways, P interblob ■ V1 - primary visual cortex ■ Association visual cortex ○ Left visual field on right hemisphere ○ Right visual field on left hemisphere ○ Nasal gets info from same side ■ Nasal retina crosses at optic chiasm ○ Temporal gets info from opposite side ○ First synapse in visual pathway is the retina Mechanism of vision ● Transduction ○ In dark, rods and cones, leaky to Na and Ca; vrest is -40mv and transmitter glutamate is released

■ depolarizing stimulus(photon) → closes cation channels(Stops cations from leaking) receptor(aka generator) potential is a hyperpolarization, which causes decreased transmitter release Layers of retina ○ receptors (rods and cones) ■ Horizontal cells ● Lateral inhibition and contrast enhancement ○ Bipolar cells ■ Amacrine ■ On is light pathway ■ Off is dark pathway ○ Retinal ganglion cells ■ Axons = optic nerve Retinal Level: bipolar cells ○ Two kinds of bipolar cells are affected by glutamate released by receptors ■ On-pathway bipolar cells have inhibitory (mGluR) glutamate receptors ● Glutamate from rods and cones hyperpolarizes these cells ● Inhibited in the dark ■ Off-pathway bipolar cells have excitatory ionotropic glutamate receptors ● Glutamate depolarizes ● Off pathway excited in the dark ○ When photoreceptor stimulated by light ■ Photoreceptors hyperpolarize, stops releasing glutamate, and disinhibits on pathway Retinal ganglion cells ○ APs are first possible in retinal ganglion cells ■ All other retinal cells signal with graded potentials ○ RGCs receive input from multiple receptors via the bipolar cells ○ RGCs have more complicated receptive fields than receptors or bipolars and require contrast ○ Two types of RGCs as categorized by receptive field properties ■ On-center and off-center ○ REQUIRED CONTRAST TO RESPOND ○ RGCS ARE NOT INTERESTED IF THERE IS NOT CONTRAST WITHIN RF ■ IF ENTIRE RF IS LIT IT CAN’T FIRE LGN(thalamus) ○ Receives info about stimulus location and contrast ○ Rod(m) pathways and Cone(p) pathways are separated (parallel processing) ■ M pathway is movement ■ P-blob is color ■ P-interblob is form and depth Primary visual cortex ○ Info concerning form and orientation of stimulus is added ○ Cortical cells are choosy when it comes to adequate stimulus ○ All have preferred orientation and contrast at a preferred angle ■ Best stimulus = bar of light oriented at precise angle ■ Some require an end-stopped light stimulus (discontinuous edge) ■ Some require some movement across rf, in preferred direction and at preferred speed Association Visual cortex ○ Info from V1 sent to 30 visual areas for higher processing ■ Facial recognition cortex ■ Color processing ● V4 ○ ○

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THE LATERALIZED BRAIN ● Two cerebral hemispheres are not mirrors of each other ● Left ○ Analysis of right visual field ○ Stereognosis ○ Lexical and syntactic language ○ Wiritng ○ Speech ○ Damage causes aphasia ● Right ○ Analysis of left visual field ○ Stereognosis ○ Emotional coloring of language ○ Spatial abilities ○ Rudimentary speech ○ Damage causes agnosia(lack of knowledge), aprosodia(lack of tone), deficit in nonsyntactic processing of language, hard time distinguishing tone ● Speech is in frontal lobe ● Understanding language is in temporal lobe ● Stroke ○ Blood clot ○ Contralateral hemiplegia is caused by the middle cerebral artery ● Cerebrovascular accident ○ Common CVA site: middle cerebral artery ○ Affects internal capsule ■ Major somatosensory projection to S1 ● Axons of 3rd order neurons ■ Major descending projections from M1 ● Corticospinal axons that terminate on motor neurons to skeletal muscles ○ Results in contralateral hemiplegia ■ Left hemiplegia (right CVA) ● Retains speech and language functions ● May display aprosodia ● Neglect of affected left side ■ Right hemiplegia (left CVA) ● Apahsia ● High ability to interpret speech based on non-verbal cues ● Hemi Neglect ○ Right hemisphere damage is more common ○ Left sided neglect is due to inferior parietal lobe or superior temporal lobe of right hemisphere ○ Patients with left neglect act as though whole regions of space on the left don't exist

AUTONOMIC NERVOUS SYSTEM ● Somatic nervous system control skeletal muscle ● Visceral nervous system ○ Efferent innervation of tissues other than skeletal muscle ○ Somatic is voluntary ○ Autonomic is involuntary ● Consists of ○ Visceral motor neurons ○ Target organs ■ Cardiac muscle ■ Smooth muscle ■ Adipocytes ■ Glands ● Visceral and Somatic motor neurons ○ Visceral neurons: pre and postganglionic neurons (Fibers), excitatory or inhibitory ○ Post is what innervates ○ Anywhere where 2 neurons make a synapse, neurotransmitter will be released ■ Cns, center of ganglion, target tissue ● Division of the ANS ○ Sympathetic ■ Fight of flight ○ Parasympathetic ■ Rest and digest ○ Innervation of target organs is typically paired (dual innervations) ■ Parasympathetic and sympathetic hit up both organs ● Sympathetic division organization ○ Preganglionic Neuron ■ Originate in CNS (T1-L2) ○ Postganglionic neuron ■ Trunks span spinal column, cervical to sacral ● Sympathetic chain ○ Majority of the postsynaptic fibers originate in this region ○ Directly adjacent to the spinal cord on both sides ○ Insert into organs/glands of head, heart, lungs ○ SYNAPSE ON BOTH SIDE ● Collateral ganglia ○ Ganglia are found in abdominal cavity close to target organs ■ Celiac ■ Superior mesenteric ■ Inferior mesenteric ■ DON’T NEED TO KNOW THESE ○ BOTH SIDES SYNAPSE ON VENTRAL SIDE ● Adrenal medulla ○ Specialized postganglionic cells form an endocrine gland ■ Chromaffin cells(modified postganglionic cells ■ Secrete 80% epinephrine and 20% norepinephrine into blood stream ● Parasympathetic ○ Preganglionic cell bodies originate from cranial nerves and sacral region of spinal cord ■ Cranial nerves ● 3, 7, 9, 10(only frat guys vape) ○ oculomotor , facial, glossopharyngeal, vagus ○ Tear production, production of saliva, production of saliva, regulates many structures ■ Spinal cord ● S2, S3, S4

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Functions ○ Sympathetic ■ Fight of flight ● Organized for mass discharge ● Passive is flight ● Active is fight ● Due to release of epinephrine and norepinephrine ○ Increased heart rate ○ Constrict BV in GI ○ Increased respiration rate ○ Sweating ○ Dialiate BV around skeletal muscle (BV is blood vessel) ○ Dilation of airways ■ Mediated by sympathetic nervous system ○ Parasympathetic ■ Not organized for mass discharge ● Decreased heart rate ● Increased GI activity ● Dilate BV around GI ● Airway constriction ● Decrease respiratory rate Neurons defined by Neurotransmitter produced ○ Cholinergic (CHOLINE) ■ Neurotransmitter released ● Acetylcholine ■ Where? ● All preganglionic cells ● Postganglionic neurons of PARAsympathetic ○ Adrenergic(only sympathetic) ■ Neurotransmitter ● epi(adrenaline) and norepi ■ Where? ● Postganglionic neuron of SYMPathetic ● Adrenal chromaffin cells Different receptors for acetylcholine ○ Nicotinic ■ Ionotropic ■ Agonist: acetylcholine, nicotine ● Found on postganglionic neurons of both division ○ Muscarinic ■ Metabotropic ■ Agonist: acetylcholine, muscarine ● On target organs (parasympathetic only) Adrenergic ○ Responds to epi and norepi ○ Only in sympathetic

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Body function is a balance ○ Dual innervation of body tissues leads to antagonistic control ○ Not mutually exclusive ■ Can work alone or work simultaneously to control normal function ■ Balanced of basal activity is tone

ENDOCRINE 1: MECHANICS OF HORMONE ACTION ● The endocrine system ○ A chemical messenger system within the body ○ Coordinates essential processes within the body by effecting changes at the cellular level ○ Decentralized ○ Endocrine glands are ductless ● Nervous system vs endocrine system ○ Nervous is localized, short duration, rapid recovery ○ Endocrine is global, long duration, long recovery ● Neurohormones ○ Adrenal medulla is an example ○ Secreted directly from neurons into the bloodstream ● Hormone control ○ Fuel metabolism ○ Vascular function ○ Reproduction ○ Cell growth ○ Cell differentiation ○ Behaviour ● Hormonal diversity ○ Over 50 different hormones ■ Vary in origin, structure , and function ● Structural classifications ○ Peptide ■ polypeptide/protein messengers ■ Synthesized as preprohormones ■ Processed as prohormones ■ Cleaved to become hormones ■ Examples are releasing hormones, glucagon, insulin ■ Need to be in vesicles ■ Water soluble ○ Steroid ■ Lipid soluble ■ Need transport proteins ■ Process cholesterol backbone ■ Cortical steroids ● Cortisol aldosterone ■ Sex steroids ● Estrogen, progesterone, testosterone ■ Can go right through membrane, don't need a receptor on extracellular ○ Amine ■ Derived from single amino acids ● Tyrosine ○ Thyroid hormone ■ Lipid s...