VMED 2000 exam 2

What is the difference between the lumbar plexus and the sacral plexus?

lumbar-cranial and medial thigh function

sacral-caudal thigh, crus, pes, and perineal functions

What is the origin of the lumbosacral plexus roots?

L4-S3

Where does the genitofemoral nerve travel? what regions does it supply? what clinical relevance does it have?

-detaches from femoral branches to skin of proximomedial thigh and branches to scrotum/prepuce or mammary/vulva

-supplies inguinal region and external genitalia

-useful for nerve blocks on scrotum/udder

Where does the femoral nerve travel? what regions does it supply? what clinical relevance does it have?

-arises from cranial part of plexus and travels through psoas muscles (adductors)

-sole motor supply for quadriceps

-injury to femoral nerve = collapsing at the knee, inability to extend stifle and weight bear. also causes patellar reflex

Where does the obturator nerve travel? what regions does it supply? what clinical relevance does it have?

-follows medial ilium and exits pelvis via obturator foramen

-supplies adductor muscles

-injury in cattle: can be caused from pelvic damage during birthing— “downer cows” (legs splay outward)

where do cranial and caudal gluteal nerves travel? what regions do they supply? what clinical relevance do they have?

innervates middle and deep gluteals, essential for hip extension and stabilization

What is the sciatic nerve?

longest nerve in the body, innervates the hamstrings before dividing into tibial and common fibular nerves

Where does the fibular nerve travel? what regions does it supply? what clinical relevance does it have?

-over lateral head of gastrocnemius

-supplies craniolateral muscles which flex the hock and extend the digits

-injury = knuckling and dragging of the limb

Where does the tibial nerve travel? what regions does it supply? what clinical relevance does it have?

-enters leg b/n two heads of gastrocnemius

-supplies all muscles on the caudal aspect of the tibia/fibula, including digital flexors and hock extensors

-injury = dropped hock

Where does the pudendal nerve travel? what regions does it supply? what clinical relevance does it have?

medioproximal leg, perineal sensation and external sphincters

damage = incontinence

What composes the axial skeleton?

skull, vertebral column, ribs, sternum

What is the spinous process of a vertebra?

dorsal, prominent

What is the transverse process of a vertebra?

separate dorsal and ventral trunk muscles (wings)

What is unique about/the function of cervical vertebra? (include first two)

-supports neck motility

1st vertebra: atlas, no body, prominent wings

2nd vertebra: axis, pivot of neckw

what is unique about thoracic vertebra?

-articulate with ribs

-tall spinous processes

-small transverse processes

What is unique about lumbar vertebra?

-has all four processes (transverse, spinous, accessor, mamillary)

-supports abdominal weight and locomotion

What is the function of intervertebral discs? What are their parts?

mechanical shock absorbers

-nucleus pulposus: pulpy nucleus, originates from notochord

-annulus fibrosus: fibrous rings surrounding and supporting nucleus pulposus

What is IVDD?

interventricular disc disease, annulus fibrosus breaks allowing nucleus pulposus to escape into the vertebral canal

What is the nuchal ligament?

-very important ligament in large animals like horses

-gives support to head and neck

NOT PRESENT IN CATS OR PIGS

-allows muscle weakness to result in dropped neck/head

What are the three types of ribs?

sternal-directly articulate with the sternum via cartilage

asternal-indirectly articulate with the sternum via costal arch

floating-no connection

Differentiate costovertebral vs costotransverse joint

costovertebral-connects rib head to bodies of two vertebra

costotransverse-sliding articulation between rib tubercle and transverse process

In skeletal muscle fibers does calcium release from the sarcoplasmic reticulum occur independently of stimulation at the neuromuscular junction?

no

What is the method and symptom of tetanus toxin?

-tetanospasmin toxin targets SNARE, which is required for synaptic vesicle fusion and NT release

-retrograde axonal transport

-blocks exocytosis of inhibitory muscular NTs like GABA and Glycine

-results in spastic paralysis

What is the method and symptom of botulism?

-presynaptic, targets SNARE

-blocks RELEASE of excitatory NTs (like ACh) at the neuromuscular junction

-results in flaccid paralysis

What is the method and symptoms of myasthenia gravis?

-immune system produces antibodies against POSTSYNAPTIC ACh receptors

-inhibits acetylcholinergic nicotinic receptors → fewer receptors → skeletal muscle weakness

-symptoms: food in esophagus = impaction/aspiration pneumonia, stretched esophagus

What are method and symptoms of white muscle disease?

-NUTRITIONAL deficiency of Vitamin E and Selenium which are antioxidants

-causes buildup of reactive oxygen species which results in muscle weakness and eventual heart failure

What is CNS vs PNS?

CNS = central nervous system; brain and spinal cord

PNS = cranial nerves, spinal nerves, and ganglia which connect CNS to muscles and glands

What is afferent vs efferent?

afferent: sensory, carries impulses towards the spinal cord and brain

efferent: motor, carries impulses away from the brain and spinal cord

What is the somatic nervous system?

deals with sensory and motor functions including locomotion and skin stimulation

What is a nerve?

a collection of neuronal axons located in the peripheral nervous system

What are the tissue layers of a nerve?

endoneurium, perineurium, epineurium

What is a ganglion?

a collection of neuronal cell bodies in the PNS

What is a nucleus (nervous)?

a collection of neuronal cell bodies in the CNS

What is a multipolar neuron?

many dendrites, one axon (ex motor)

What is a bipolar neuron?

one dendrite, one axon (ex auditory)

What is a pseudounipolar axon?

one process that bifurcates into central and peripheral axonal branches (ex sensory ganglion)

What are the five functional segments of a neuron?

receptive-where stimuli change membrane potential (dendritic)

trigger-where impulses are generated

conductive-carries impulses

transmissive-where NTs are released

cell body segment-trophic center

What are the parts of the internal spinal cord?

gray matter-butterfly shape, composed of neuron cell bodies and supporting glia

white matter-surrounds gray, composed of myelinated axons grouped into tracts/funiculi

What are the regions of gray matter localized to?

dorsal horn-sensory

lateral horn-autonomic

ventral horn-motor

What are the three germ layers (which primarily forms the nervous system)?

ectoderm

mesoderm

endoderm

When does neural induction begin?

when ectoderm overlaying the notochord thickens to form the neural plate

What is the notochord?

structure in embryo that influences the ectoderm to change

What happens as a result of incomplete neuropore closure?

caudal neuropore: spina bifida

rostral neuropore: incomplete brain formation

What are neural crest cells?

cells that separate from neural folds, become:

-peripheral sensory neurons

-autonomic neurons

-enteric nervous tissue

-adrenal medulla

-melanocytes

-craniofacial cartilage

What are the layers of the developing neural tube wall? what do they become?

mantle layer → gray matter

marginal layer → white matter

What does the rostral neural tube form as the brain?

prosencephalon, mesencephalon, rhombencephalon

What do the lumen of the neural tube persist as?

the ventricular system of the brain

What is anterograde transport?

away from soma to periphery

What is retrograde transport?

towards soma from terminals (used by toxins)

Which directions of travel are kinesin and dyenin used for?

kinesin: anterograde

dyenin: retrograde

What produces myelin?

in CNS: oligodendrocytes

in PNS: schwann cells

What is the function of astrocytes?

support

What is the function of microglia?

phagocytic

What are ependymal cells?

columnar cells lining brain ventricles and central canals, joined by junctional complexes, no basement membrane

What is the primary physical barrier in the blood brain barrier?

tight junctions between endothelial cells, keep nearly all molecules out beside water and small lipidic molecules

What kind of drugs must be used to treat the central nervous system?

lipid-soluble

Where is the blood brain barrier absent?

circumventricular organs; pineal gland, area postrema, neurohypophysis

What makes a brain chamber a ventricle?

choroid plexus present

What order does CSF flow in the brain?

lateral ventricle → interventricular foramina → third ventricle → mesencephalic aqueduct → fourth ventricle

How does the spinal cord taper caudally?

tapers into conus medularis and filum terminale. elongated nerve roots form the cauda equina

What are the protective layers of the CNS?

dura mater-tough mother

arachnoid membrane-CSF occupies subarachnoid

pia mater-small mother

What are three spinal cord landmarks?

ventral median fissure-deep midline cleft center bottom

dorsal median sulcus-shallow groove on top

dorsolateral sulcus

What is associated with the lateral horn of the spinal cord?

gray matter-visceral/autonomic motor neurons

What are the differences between dorsal funiculi, lateral funiculi, and ventral funiculi?

dorsal: mainly sensory

lateral: motor interiorly, sensory exteriorly

ventral: mostly motor

What is the orientation of major ascending tracts in the spinal cord? give clinical relevance

these are sensory, located more dorsally; sacral tracts are more exterior than lumbar, so compression trauma first affects hindlimbs

Describe blood supply in the spinal cord

one ventral spinal artery supplies “core” gray matter

two dorsolateral spinal arteries supply peripheral white matter funiculi

gray receives almost 3x the density of blood supply as white matter

What is unique about the epidural venous plexus?

(associated with the spine)

valveless, allowing bidirectional flow, also creates risk of infection/neoplastic spread

What is a reflex?

an inherent, subconscious response to a particular stimulus involving the somatic nervous system, usually protective in nature

What are the five fundamental components of a reflex arc?

1. receptor to detect the stimulus

2. afferent limb (sensory) to transmit the signal

3. integration center in the CNS gray matter

4. efferent limb (motor) to carry instructions out

   1. effector organ to execute the response

What is a monosynaptic reflex?

a reflex arc that consists of only two neurons and a single synapse

-relatively uncommon, primarily in stretch/myotatic reflex (effector=muscles)

What is a polysynaptic reflex?

the most common type of reflex, consists of one or more interneurons between afferent input and motor output

What is it called when nerve fibers cross from one side of the brain/spinal cord to the other in an X shape?

decussation

What are the five brain divisions?

-telencephalon

-diencephalon

-mesencephalon

-metencephalon

-myelencephalon

What constitutes the forebrain vs midbrain vs hindbrain?

forebrain: telencephalon, diencephalon

midbrain: mesencephalon

hindbrain: metencephalon, myelencephalon

What is associated with the metencephalon?

pons, cerebellum

What is associated with the myelencephalon?

medulla oblongata

What is the function of the cerebrum?

cognition, behavior, sensation, and voluntary movement

What is the function of the cerebellum?

balance, posture, and coordination

What is the function of the brainstem?

cranial-nerve function, respiration, circulation

What does the transverse fissure separate?

cerebrum from cerebellum

Where is white/gray matter inside the brain?

white-more central

gray-towards outside

What parts of the brain are associated with the brainstem?

diencephalon, midbrain, pons, medulla oblongata

What is CN 1? What is its origin? What is its function?

olfactory, telencephalon-rostral end, special sensory for olfaction

What is CN II? What is its origin? What is its function? (what is unique?)

Optic nerve, in diencephalon-converges at optic chiasm, special sensory for vision

*technically a CNS tract rather than a peripheral nerve

What is CN III? What is its origin? What is its function?

Oculomotor nerve, mesencephalon, motor function for extraocular muscles as well as ciliary muscles for pupil constriction

What is CN IV? What is its origin? What is its function?

Trochlear nerve, emerges from the dorsal mesencephalon, functions as somatic motor to dorsal oblique of the eye

What is CN V? What is its origin? What is its function?

Trigeminal nerve, only nerve to emerge from the pons (and trapezoid bodies), has THREE FUNCTIONS

• ophthalmic-corneal/eye sensation

• maxillary-sensory for upper face

• mandibular-motor and sensory for lower half of face and jaw

What is CN VI? What is its origin? What is its function?

Abducent, emerges from lateral angle between trapezoids and pyramids, functions as a somatic motor to abduct the eye (injury = no lateral deviation)

What is CN VII? What is its origin? What is its function?

Facial nerve, emerges laterally from trapezoid body, innervates superficial muscles of facial expression, tear gland, mandibular and sublingual salivary glands, and caudal tongue taste sensation

What is CN VIII? What is its origin? What is its function?

Vestibulocochlear nerve, emerges laterally from the trapezoid body, functions as special sensory for hearing, as well as for balance and head position

What is CN IX? What is its origin? What is its function?

Glossopharyngeal nerve, along lateral aspect of the medulla, taste in caudal 1/3 of tongue, innervates pharyngeal muscles, supplies parotid and zygomatic salivary glands

loss = swallowing difficulty

What is CN X? What is its origin? What is its function?

Vagus nerve (wandering nerve); along lateral aspect of medulla; supplies sensation for pharynx, larynx, thoracic/abdominal viscera, and supplies autonomic control of heart, lungs, and digestive system

What is CN XI? What is its origin? What is its function?

Accessory nerve; along lateral aspect of medulla; functions as somatic motor nerve to some neck and shoulder muscles (trapezius, sternocephalicus, omotransversarius)

What is CN XII? What is its origin? What is its function?

Hypoglossal Nerve; emerges ventrally via several rootlets on lateral pyramids; somatic motor to all muscles of the tongue

Which cranial nerves are sensory?

I, II, VIII

Which cranial nerves are motor?

III, IV, VI, XI, XII

Which cranial nerves are both sensory and motor?

V, VII, IX, X

What is function of frontal lobe vs parietal lobe?

frontal-motor control

parietal-somatosensory processing

What is the function of the rhinencephalon?

supports smell and memory

What is the function of the limbic system?

emotional drive, survival