Test 2 Flashcards

Question

Olfactory Projection Pathways: - L6, page 39

Answer 1

Optic nerves Axons arising from the RETINA of the eye to form OPTIC NERVE Each optic nerve passes through its OPTIC FORAMEN of the orbit Nerves converge to form the OPTIC CHIASM (axons partially cross over) & continue on as OPTIC TRACTS Enables VISION

Answer 2

Visual Processing: 1) Retina Processing Steps: Local currents produce in response to light Rods & Cones > Bipolar neurons > Ganglion cells > Optic nerve > Subcortical & cortical visual areas

Answer 3

Visual Processing Each nasal retina sees a TEMPORAL VISUAL FIELD/WORLD Each temporal retina sees NASAL VISUAL FIELD/WORLD Left side of each retina sees the RIGHT VISUAL FIELD/WORLD Right side of each retina sees the LEFT VISUAL FIELD/WORLD

Answer 4

VIsual processing Optic Tract: Crossed axons from NASAL RETINA & uncrossed axons from TEMPORAL RETINA

Answer 5

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Answer 6

Oculomotor Nerves Axons extend from VENTRAL MIDBRAIN & pass through the SUPERIOR ORBITAL FISSURE to the EYE

Answer 7

III. Oculomotor Nerves: Somatic (voluntary) motor axons to 4 of the 6 extrinsic eye muscles - move EYEBALL to LEVATOR PALPEBRAE superior muscle - raising UPPER EYELID

Answer 8

III. Oculomotor Nerves: Parasympathetic (autonomic) motor axons to CONSTRICTOR muscles of IRIS - causing pupil to CONSTRICT to CILIARY muscle - controlling shape of LENS for visual focusing

Answer 9

III. Oculomotor Nerves In sum: provides most of the MOVEMENT of each eye ALSO: - Opening of eyelid - Constriction of pupil - Focusing

Answer 10

IV. Trochlear Nerves Axons emerge from DORSAL MIDBRAIN, course ventrally around midbrain, pass through the SUPERIOR ORBITAL FISSURE to the EYE

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IV. Trochlear Nerves Provide EYE MOVEMENT Damage causes DOUBLE VISION & inability to rotate eye INFEROLATERALLY

Answer 12

V. TRIGEMINAL NERVES Axons extend from FACE TO PONS & PONS TO MUSCLES Cell bodies of sensory neurons are located in large TRIGEMINAL GANGLION

Answer 13

V. Trigeminal Nerve Axons run from FACE TO PONS via SUPERIOR ORBITAL FISSURE Convey SENSORY IMPULSES from skin of anterior scalp, upper eyelid & nose, & from nasal cavity mucosa, cornea & lacrimal (tear) gland

Answer 14

V. Trigeminal Nerves: Mandibular division (V3) Axons pass through skull via FORAMEN OVALE Convey SENSORY IMPULSES from anterior tongue (except taste bud), lower teeth, skin of chin, & temporal region of scalp

Answer 15

V. Trigeminal Nerves: Mandibular division (V3) MOTOR BRANCH Supply MOTOR AXONS to (carry proprioceptor axons from) muscles of mastication

Answer 16

V. Trigeminal Nerves LARGEST cranial nerve MAIN SENSORY NERVE TO FACE (transmitting afferent impulses from touch, temperature & pain receptors) Supply motor axons to MUSCLES OF MASTICATION DAMAGE produces loss of sensation & impaired chewing

Answer 17

VI. Abducens Nerves Axons leave INFERIOR PONS & pass through SUPERIOR ORBITAL FISSURE to EYE (lateral rectus muscle) Provide EYE MOVEMENT (abducts the eyeball) DAMAGE results in inability to rotate eye laterally & at rest eye rotates medially

Answer 18

VII. Facial Nerves Axons emerge from PONS enter temporal bone via INTERNAL AUDITORY MEATUS and run w/in bone (through inner ear cavity) before emerging through styloid foramen; course to LATERAL ASPECT OF FACE

Answer 19

VII. Facial Nerves Major MOTOR AXONS OF FACE Supply motor axons to (convey proprioceptor impulses from) skeletal muscles of face (MUSCLES OF FACIAL EXPRESSION) Except for chewing muscles served by cranial nerve V Transmit PARASYMPATHETIC (AUTONOMIC) MOTOR impulses to lacrimal (tear) glands, nasal & salivary glands Convey SENSORY IMPULSES FROM TASTE BUDS of anterior 2/3 of tongue DAMAGE produces sagging facial muscles & disturbed sense of taste (missing sweet, salty & umami)

Answer 20

VII. Facial Nerves - Bells Palsy Characterised by PARALYSIS OF FACIAL MUSCLES (affected side) & PARTIAL LOSS OF TASTE SENSATION VIRAL INFECTION causing inflammation of facial nerve Symptoms: Lower eyelid droops, corner of mouth sags, tears drip continuously, eye cannot be completely closed, paralysed face is 'pulled' Treatment: Steroids, rest

Answer 21

VIII. Vestibulocochlear Nerves Axons arising from hearing & equilibrium apparatus w/in INNER EAR OF TEMPORAL BONE, passing through INTERNAL ACOUSTIC MEATUS to enter BRAINSTEM AT THE PONS-MEDULLA BORDER

Answer 22

VIII. Vestibulocochlear Nerves Provide HEARING (cochlea nerves) and sense of BALANCE (vestibular nerves DAMAGE produces - Deafness - Dizziness, nausea - Loss of balance - Vestibular nystagmus (rapid involuntary eye movements)

Answer 23

Temporal Lobe - Primary Auditory Cortex TRANSVERSE TEMPORAL GYRUS (inside lateral fissure) extending to superior margin of the SUPERIOR TEMPORAL GYRUS Processes AUDITORY INFO UNILATERAL DAMAGE (MIDDLE CEREBRAL ARTERY) = hearing loss BILATERAL DAMAGE = cortical deafness

Answer 24

IX. Glossopharyngeal Nerves Axons emerge from MEDULLA & leave skull through JUGULAR FORAMEN

Answer 25

IX. Glossopharyngeal Nerves Supply MOTOR axons to (carry proprioceptor fibres from) a PHARYNGEAL MUSCLE- stylopharyngeus Provide PARASYMPATHETIC MOTOR AXONS to parotid SALIVARY GLAND

Answer 26

IX. Glossopharyngeal Nerves Sensory axons conduct TASTE & GENERAL SENSORY IMPULSES from PHARYNX & posterior 1/3 of TONGUE Conducts sensory impulses from CHEMORECEPTORS in the CAROTID BODY & PRESSURE RECEPTORS of CAROTID SINUS

Answer 27

IX. Glossopharyngeal Nerves Provide control over SWALLOWING, SALIVATION, GAGGING, SENSATION from posterior 1/3 of tongue, control of BLOOD PRESSURE & RESPIRATION DAMAGE results in loss of bitter & sour taste & impaired swallowing

Answer 28

X. Vagus Nerve Axons emerge from MEDULLA, pass through skull via JUGULAR FORAMEN, descend through neck region into THORAX & ABDOMEN

Answer 29

X. Vagus Nerves Motor: - Supply motor axons to (carry proprioceptor fibres from) skeletal muscles of PHARYNX & LARYNX - Parasympathetic (autonomic) motor fibres supply HEART, LUNGS & ABDOMINAL VISCERA Sensory: - Conduct sensory impulses from THORACIC & ABDOMINAL VISCERA - Transmit sensory impulses from CHEMORECEPTORS in the CAROTID & AORTIC BODIES & PRESSURE RECEPTORS of CAROTID SINUS - Conduct sensory impulses from TASTE BUDS of posterior tongue & pharynx

Answer 30

X. VAGUS NERVES The only cranial nerve extending beyond the head & neck to the THORAX & ABDOMEN Majority of motor axons are PARASYMPATHETIC (AUTONOMIC) Provide SWALLOWING & SPEECH; regulate activities of MAJOR VISCERA DAMAGE causes hoarseness or loss of voice, impaired swallowing & digestive system mobility HYPOACTIVITY implicated in hypertension, anxiety disorders & depression

Answer 31

XI Accessory Nerves CRANIAL root joins with axons of vagus nerve (X) to supply motor axons to LARYNX, PHARYNX & SOFT PALATE DAMAGE causes hoarseness or loss of voice & impaired swallowing SPINAL roots supplies motor axons to trapezius & sternocleidomastoid muscles, therefore provides HEAD, NECK & SHOULDER MOVEMENTS DAMAGE causes impaired head, neck & shoulder movement eg unable to shrug on one side if unilateral injury

Answer 32

XII. Hypoglossal Nerves Axons arise by a series of roots from MEDULLA, exit from skull via HYPOGLOSSAL CANAL to TONGUE Axons emerge b/w the PYRAMID & OLIVE

Answer 33

XII. Hypoglossal Nerves Supply somatic motor axons to muscles of TONGUE Provide TONGUE MOVEMENTS of speech, food manipulation & swallowing DAMAGE causes dificulties in speech & swallowing - Both sides - inabiluty to protrude tongue - One side - tongue deviates (leans) toward injured side & eventually results in ipsilateral atrophy

Answer 34

Cerebellum Consist of CORTEX, WHITE MATTER & DEEP NUCLEI 40 x more AFFERENT than EFFERENT very ORDERED structure concerned primarily with: - SYNCHRONISED, precisely timed movement - control of MUSCLE TONE (posture) - maintenance of BALANCE Receives vast amount of sensory info, but does not give rise to CONSCIOUS SENSORY perceptions

Answer 35

External Cerebellum (superior surface) Right and left hemispheres connected by VERMIS Parallel surface folds called FOLIA are grey matter

Answer 36

Cerebellar Lobes Anterior & posterior lobes co-ordinate MOVEMENT

Answer 37

Flocculonodular lobe helps with BALANCE

Answer 38

Cerebellum: Sagittal Sub-Divisions What are the zones? - Lateral zone - Intermediate zone

Answer 39

Spinocerebellum (vermis & intermediate zone): Receives PROPRIOCEPTIVE information Regulates BODY MOVEMENTS via ERROR CORRECTION

Answer 40

Cerebrocerebellum (lateral zone): Receives input from the PONS and CEREBRAL CORTEX, outputs to the THALAMUS and RED NUCLEUS PLANNING movements and motor learning Coordination of MUSCLES Important in VISUALLY GUIDED movements

Answer 41

Vestibullocerebellum (flocculonodular lobe): Receives inputs from the VESTIBULAR system, sends outputs back to the VESTIBULAR NUCLEI Controlling BALANCE OCULAR (eye) reflexes

Answer 42

Three major components: - Superficial gray matter (cortex) - White matter) - Deep nuclei (gray mattey)

Answer 43

What makes up the Deep Cerebellar Nuclei? - Fastigial - Interposed - Dentate

Answer 44

Cerebellar Cortex - Circuity Two main inputs: MOSSY FIBRES from spinal cord or brainstem neurons conveying motor or sensory input CLIMBING FIBRES mainly from inf. olivary nucleus = proprioceptive input MOSSY AXONS form excitatory synapses with GRANULE NEURONS in the cerebellar cortex The GRANULE NEURONS send their axon as a 'parallel fibre' to form exitatory synapses with the PURKINJE neurons

Answer 45

Cerebellar Cortex - Circuitry Climbing axons form EXCITATORY synapses directly with the PURKINJE NEURONS in the CEREBELLAR CORTEX PURKINJE neurons are the sole output of the cerebellar cortex - Inhibitory - synapse in DEEP CEREBELLAR NUCLEI - Work with input axons to regulate FIRING FREQUENCY and AMPLITUDE of the neurons in the deep cerebellar nuclei

Answer 46

Cerebellar Peduncles Inferior Cerebellar Peduncle (Medulla) Conveys SENSORY information to the cerebellum - From MUSCLE proprioceptors throughout the body - From the VESTIBULAR NUCLEI of the brainstem (equilibrium & balance) Contains both AFFERENT & EFFERENT axons

Answer 47

Cerebellar Peduncles Middle Cerebellar Peduncle (Pons) Contains only AFFERENT axons (crossed axons from CONTRALATERAL PONTINE NUCLEI)

Answer 48

Cerebellar Peduncles Superior Cerebellar Peduncle (Midbrain) Formed by axons that arise from DEEP CEREBELLAR NUCLEI (main EFFERENT pathway) - Fibres decussate at various levels - either terminate in the RED NUCLEUS or continue rostrally to end w/in the THALAMUS (then to CEREBRAL MOTOR CORTEX)

Answer 49

Cerebrocerebellar Ciruit (Lateral Zone) Dentate nucleus receives SENSORIMOTOR information from LATERAL CEREBELLAR CORTEX, CEREBRAL CORTEX & PONS - Input to the VENTROLATERAL THALAMUS & RED NUCLEUS Controls MULTI-JOINTED movements of LIMBS, and contributes to MOTOR PLANNING

Answer 50

Spinocerebellar Circuit Fastigial nucleus receives SOMATOSENSORY information from VERMAL CEREBELLAR CORTEX & TRUNK - Input to VESTIBULAR NUCLEI & RETICULAR FORMATION Controls POSTURE via influencing axial muscles in TRUNK

Answer 51

Spinocerebellar Circuit (Intermediate Zone) Interposed nuclei receive SOMATOSENSORY information from INTERMEDIATE CEREBELLAR CORTEX & LIMBS - Inputs to the RED NUCLEUS Controls ACCURACY OF LIMB MOVEMENTS (precision of movements at joints)

Answer 52

Vestibulocerebellar Circuit (Flocculonodular Lobe) Flocculonodular lobe receives VESTIBULAR information - Input to the VESTIBULAR NUCLEI Controls BALANCE

Answer 53

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Answer 54

How is synergistic multijoint movement achieved? At the same time, the cerebellum receives information from proprioceptors THROUGHOUT THE BODY, as well as VISUAL & VESTIBULAR input

Answer 55

Sensation DETECTION of sensory stimulus Stimulus = change in the EXTERNAL or INTERNAL environment Perceptions INTERPRETATION of the meanings of the sensory stimuli Both sensation & perception occur in the BRAIN

Answer 56

Special Senses Each special sense organ projects to a specialized region of the brain. In the cerebrum, specialized region is called a PRIMARY SENSORY CORTEX Taste - lower end of POSTCENTRAL GYRUS Smell - medial TEMPORAL & ORBITOFRONTAL lobes Vision OCCIPITAL lobe Hearing - SUPERIOR temporal gyri/ TRANSVERSE temporal gyri Equilibrium - mainly to the CEREBELLUM

Answer 57

Sensory Receptors - Are specialized to respond to CHANGES in their ENVIRONMENT Classified by: - the type of STIMULUS they detect - their body LOCATION - their structural COMPLEXITY

Answer 58

Classification of Sensory Receptors by Stimulus Type 1) Mechanoreceptors - Are sensitive to a MECHANICAL FORCE (eg touch, pressure, vibration, stretch, itch) 2) Thermoreceptors - Are sensitive to TEMPERATURE changes 3) Photoreceptors - Respond to LIGHT ENERGY (the retina of the eye) 4) Chemoreceptors - Respond to CHEMICALS in solution (molecules smelt or tasted, or changes in blood chemistry) 5) Nociceptors (noci = harm) - Respond to potentially DAMAGING STIMULI that result in pain

Answer 59

Classification of Sensory Receptors by Location 1) Exteroceptors - are sensitive to stimuli arising OUTSIDE the body - are located NEAR or AT the body surface - include: - touch, pressure, pain & temperature receptors - receptors of special senses (VIsion, hearing) 2) Interoceptors or Visceroceptors - are sensitive to stimuli WITHIN the body - are located in the VISCERAL ORGANS & BLOOD VESSELS (eg chemical changes, tissue stretch, temperature)

Answer 60

Proprioceptors - Are sensitive to .... stimuli - Located in SKELETAL MUSCLES, TENDONS, JOINTS, LIGAMENTS & in CONNECTIVE TISSUE coverings of bones & muscles - EQUILIBRIUM receptors of the inner ear are sometimes included in this class - Constantly advise the brain of the body's MOVEMENT & LOCATION in SPACE

Answer 61

Classification of Sensory Receptors by Structural Complexity Complex Receptors of the special senses are located in SPECIAL SENSE ORGANS (eg rods & cones of retina) Simple Receptors of the general senses: - Tactile sensation - Temperature - Pain - Muscle sense Anatomically, these receptors are either FREE NERVE endings or ENCAPSULATED NERVE endings

Answer 62

Free (Unencapsulated) Nerve Endings Widely present dendrites forming small knoblike swellings, respond mainly to PAIN & TEMPERATURE (also overt pressure) Modified free nerve endings, respond to .... ....

Answer 63

Tactile Corpuscles (Meissners Corpuscles) - Numerous in NIPPLES, FINGERTIPS & soles of the FEET - LIGHT TOUCH & TEXTURE

Answer 64

Lamellated Corpuscles (pacinian Corpuscles) - SUBCUTANEOUS tissue of the skin - DEEP PRESSURE, STRETCH, TICKLE & VIBRATION

Answer 65

Ruffini Corpuscles - DERMIS, SUBCUTANEOUS tissue & JOINT capsules - DEEP PRESSURE & STRETCH

Answer 66

Muscle Spindles - W/in SKELETAL MUSCLES - Each consist of a bundle of MODIFIED skeletal muscle fibres in a CONNECTIVE TISSUE CAPSULE - MUSCLE STRETCH (proprioception)

Answer 67

Encapsulated nerves Endings: Joint Kinesthetic Receptors - Are PROPRIOCEPTORS that monitor stretch in the articular capsules that enclose synovial joints - Contribute to CONSCIOUS PROPRIOCEPTION

Answer 68

Ascending Somatosensory Exteroception & Proprioception Systems Recieves input from EXTEROCEPTORS & PROPRIOCEPTORS DORSAL COLUMNS - MEDIAL LEMNISCUS PATHWAY Pathway - fine touch, vibration & conscious proproiception = fin discrimination SPINOTHALAMIC Pathways - Pain, temperature, crude touch & pressure - ANTERIOR & LATERAL Pathways SPINOCEREBELLAR Pathways - unconscious proprioception

Answer 69

General Organzation of Somatosensory Systems 3) Cerebral neural circuits THIRD order neurons 2) Ascending pathways SECOND order neurons 1) Sensory receptors FIRST order neurons

Answer 70

1) Processing at the Receptor Level Propagation - generating NERVE IMPULSES to the SPINAL CORD/ MEDULLA Transduction - Converting STIMULUS ENERGY into changes in membrane potential in SENSORY axons Receptors - Detecting STIMULI

Answer 71

Processing at the Circuit level Ascending Sensory Pathways - Impulses delivered to the appropriate regions of the THALAMUS - OR impulses delivered to the CEREBRUM

Answer 72

3) Processing at the Perceptual Level | - INTERPRETATION of sensory input

Answer 73

Dorsal Column - Medial Lemniscus Pathway GRACILE TRACT carries impulses from lower limbs & inferior body trunk CUNEATE TRACT transmits afferent impulses from upper limbs, trunk & neck

Answer 74

Comparing Cross-section of Spinal Cord WHITE MATTER increases in dorsal columns from lumbar to cervical regions - reflects increasing addition of SENSORY fibres from caudal to rostral truck regions

Answer 75

Cuneate & Gracile tubercles (in closed medulla) receive SOMATOSENSORY information from CUNEATE FASCICULUS & GRACILE FASCICULUS spinal tracts, from the upper and lower body respectively

Answer 76

Spinothalamic Pathways Lateral Spinothalamic Pathway - Transmits impulses with PAIN & TEMPERATURE to opposite somatosensory cortex Anterior Spinothalamic Pathway - Transmits impulses concerned with CRUDE TOUCH & PRESSURE to opposite somatosensory cortex

Answer 77

Spinocerebellar Pathways Transmit information about muscle or tendon stretch to the IPSILATERAL CEREBELLUM, which use this information to coordinate skeletal muscle activity Responsible for UNCONSCIOUS PROPRIOCEPTION

Answer 78

Hierarchy of Motor Control Highest: PRE-MOTOR CORTEX, BASAL GANGLIA & CEREBELLUM - PRECOMMAND level - PRE-ACTION level Middle PRIMARY MOTOR CORTEX & BRAINSTEM - PROJECTION level Lowest SPINAL CORD - SEGMENTAL level

Answer 79

1) Precommand Level - Programs & Instructions Includes the PREMOTOR CORTEX, CEREBELLUM & BASAL GANGLIA PREMOTOR CORTEX responsible for initiating plan for next intended movement - Innervates BASAL GANGLIA to release brake to start a specific movement - Innervates CEREBELLUM which precisely calculates the best way to achieve coordinated synergistic movements across multiple limb joints - also monitors muscle TONE & BALANCE

Answer 80

2) the Projection Level Made up of the PRIMARY MOTOR CORTEX (precentral gyrus) & BRAINSTEM

Answer 81

The Projecttion Level UPPER MOTOR NEURONS in the primary cortical motor areas & brainstem: - synapse with LOWER MOTOR NEURONS, which are motor neurons of the cranial nerves (brainstem) or spinal nerves Upper motor neurons from cortical motor areas produce the direct (PYRAMIDAL) system, eg: - Corticospinal tracts: - Regulates FAST & skilled movement - Plays some role in modulating SENSORY input - Corticobulbar tracts: - FACIAL expression, TOUNGE movements, movements of MASTICATION

Answer 82

The Projection Level Upper motor neurons from the brainstem motor areas form the indirect (MULTINEURONAL, EXTRAPYRAMIDAL) system - TECTOSPINAL tracts - Head, neck & eye movements - RUBRROSPINAL tracts - Flexor tone, large muscle movements & fine motor control - RETICULOSPINAL tracts - Maintains skeletal muscle tone and initiates the central pattern generator in the spinal cord - VESTIBULOSPINAL tracts - Maintains balance & muscle tone

Answer 83

Corticospinal tract: Direct (Pyramidal) Tract Origin is from the PRIMARY MOTOR CORTEX

Answer 84

Corticospinal Tract Decussation PYRAMIDS (OPEN MEDULLA) formed by the large pyramidal (corticospinal) tracts descending from the motor cortex PYRAMIDAL DECUSSATION (CLOSED MEDULLA) axons of the pyramidal tracts cross over to the opposite side at the medulla - spinal cord junction

Answer 85

Corticospinal Tracts - Summary CELL BODIES : "UPPER MOTOR NEURONS" - Precentral gyrus of the cerebral cortex BRAIN PATHWAY - Internal capsule, through midbrain (cerebral peduncle) and pons, passing into the pyramidal tract in the medulla DECUSSATION - Most fibres decussate at the medulla-spinal cord junction SPINAL PATHWAYS - Lateral corticospinal tracts (crossed & uncrossed), some fibres stay in ipsilateral anterior (ventral) corticospinal tract ENDPOINT: "LOWER MOTOR NEURONS" - Cell bodies in ventral horn of spinal gray matter

Answer 86

Corticospinal Tracts - Summary Most corticospinal neurons synapse on INTERNEURONS - regulate overall excitability In CERVICAL ENLARGEMENT of grey matter, some corticospinal neurons synapse DIRECTLY with motor neurons TERMINATION OF THE CORTICOSPINAL TRACT - 50% - cervical level - 20% - thoracic level - 30% lumbosacral level Brain "commands" are integrated by spinal neural circuits to produce COMPLEX MOVEMENTS

Answer 87

Corticobulbar Tract: Direct (Pyrimidal) Tract Origin is from the PRIMARY MOTOR CORTEX BILATERAL - Mainly contralateral Terminates in BRAINSTEM

Answer 88

Corticobulbar Tracts - Summary Neurons arise from ventral part of PRIMARY MOTOR CORTEX Starts out in company with the corticospinal tract in INTERNAL CAPSULE Synapse in MOTOR NUCLEI of CRANIAL NERVES in the pons (V, VII) and medulla (X, XI & XII) Provide FACIAL expression, TONGUE movement & movements of MASTICATION

Answer 89

Clinical Notes - Corticospinal Tract Deficits: Contralateral Deficit: - If lesion ABOVE pyramidal decussation on right = left upper limb & lower limb muscles affects Ipsilateral Deficit: - If lesion BELOW the pyramidal decussation on right = right limbs below the lesion affected

Answer 90

Indirect (Extrapyramidal) System Upper motor axons arise from several BRAINSTEM NUCLEI Four major nuclei/regions are: - SUPERIOR COLLICULUS located in tectum or roof of midbrain - RED NUCLEUS in the midbrain - RETICULAR FORMATION in pons & medulla - VESTIBULAR nuclei in medulla Four major pathways - TECTOspinal tracts - RUBROspinal tracts - RETICULOspinal tracts - VESTIBULOspinal tracts

Answer 91

Tectospinal Tracts Axons arise from SUPERIOR COLLICULUS Receives projections from axons originating from the OPTIC tracts & the OCCIPITAL & inferior PARIETAL lobes Descending fibres innervate spinal nerve motor neurons of CERVICAL SPINAL CORD and motor neurons of MIDBRAIN (III, IV) & PONS (VI) cranial nerves Mediates contralateral head and neck movements in response to VISUAL stimuli Specifically HEAD, NECK & EYE movement to allow eyes to track a moving object

Answer 92

Rubrospinal Tracts Axons arise from RED NUCLEUS Descending fibres innervate spinal nerve motor neurons of CERVICAL SPINAL CORD Mediates FLEXOR TONE, large MUSCLE movements & FINE MOTOR CONTROL in the opposite upper body

Answer 93

Retticulospinal Tracts Axons arise from RETICULAR FORMATION of the PONS & MEDULLA Maintains SKELETAL MUSCLE TONE & initiates the CENTRAL PATTERN GENERATOR in the SPINAL CORD

Answer 94

Vestibulospinal Tracts Axons arise from the LATERAL VESTIBULAR NUCLEUS Maintains BALANCE & MUSCLE TONEvia activation of axial (trunk) and limb extensor muscles

Answer 95

the projection Level - Summary The PYRAMIDAL tracts - originate from the primary motor cortex - Synapse with lower motor neurons either in the brainstem or ventral horn of the spinal cord - Concerned with voluntary, discrete, skilled movements The EXTRAPYRAMIDAL tracts - originate from the brainstem - Synapse with lower motor neurons in the ventral horn of the spinal cord - Mediates vouluntary movement, muscle tone (posture), balance, and regulates the central pattern generator

Answer 96

The Segmental Level - Spinal Cord The LOWEST level of the motor hierarchy Consist of the SEGMENTAL circuits of the SPINAL CORD Activating VENTRAL HORN motor neurons of .a single spinal cord segment stimulates a specific group of muscle fibres

Answer 97

Lower Motor Neurons Receive input from upper motor neurons of the PYRAMIDAL and EXTRAPYRAMIDAL pathways described earlier

Answer 98

Action potential ----> Events at NMJ 1) Voltage-sensitive CALCIUM channels open 2) Influx of CALCIUM ions 3) Synaptic vesicles fuse to PRESYNAPTIC MEMBRANE 4) release ACETYLCHOLINE into SYNAPTIC CLEFT 5) Diffusion across CLEFT 6) Binds to NICOTINIC RECEPTORS receptors on POSTSYNAPTIC MEMBRANE 8) AP in MUSCLE CELL & contraction of muscle 9) NEUROTRANSMITTER broken down by ACETYLCHOLINESTERASE

Test 2 Flashcards

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