Neurology - 602 Post Midterm Information

Myotactic Reflex (stretch reflex) steps:

1. Lengthen of muscle stretches extrafusal and intrafusal fibers. 2. Sensory neuron around intrafusal fibers is stimulated (change in length or velocity) 3. Sensory signal is carried to spinal cord where it activates Alpha and Gamma motor neurons 4. Alpha motor neuron send action potential to extrafusal fibers to contract them 5. Gamma motor neurons send action potential to intrafusal fibers and tells them to be sensitive

What specific reflexes are a type a tendon-jerk reflexes?

Biceps reflex, triceps reflex, and patellar reflex

Myotactic Reflex (stretch reflex) function?

Correct for changes in muscle length when extrafusal fibers contract (get shorter) or stretch (get longer).

Are the myotactic and tendon-jerk reflex mechanistically similar?

Yes mechanistically, only difference is that the tendon-jerk is caused by the clinician by tapping the muscle belly or tendon and tendon-jerk is polysynaptic

Dermatome definiton

area of skin innervated by a single spinal nerve. Sensor afferent info from a single spinal nerve.

autonomous zone definition

area of skin innervated by one peripheral nerve (made of more than one spinal nerve), no overlap between adjacent nerves.

The dorsal funiculus carries primarily ____________________ tracts and is located between the dorsal median and dorsal lateral sulci

ascending

The spinal cord communicates with the brain through __________________ and _________________ pathways that from tracts in spinal white matter.

ascending, descending

Monosynaptic reflex definition

at least one synapse within the CNS

Reflex definition

automatic stereotyped responses to internal or external stimuli subconscious, relatively consistent or stereotypical responses to a particular stimulation

What part of the nervous system controls the smooth muscle contractions?

autonomic nervous system

What color do neoplastic tumors appear as in the spinal cord?

black - from compression

White matter includes decending fiber tracts. Where do these carry information to and from?

brain to periphery

What is the cauda equina?

bundle of nerve fibers that remain after the spinal cord has terminated. Includes sciatic and pudendal nerves, conus medullaris, and the spinal roots that exit the spinal cord and extend caudally to exit the vertebrae

What is the end of the spinal cord called that tappers off starting at the lumbar enlargement?

conus medullaris

Parasympathetic nervous system is controlled by the _____________________nerves that include cranial nerves and sacral portions of the spinal cord.

craniosacral

What does the addition of ATP to myosin head cause during a muscle contraction?

crossbridges detach from actin

Are motor neurons efferent or afferent?

efferent - leave through the ventral horn

What kind of cells does the central canal have in the spinal cord?

ependymal to move the CSF

What is the space called that is between the dura of the spinal cord and periosteum on vertebra?

epidural space - full of connective tissue, fat, and blood vessels

crossed extensor reflex: Activation of ____________ muscles and inhibition of ________________ on opposite side

extensors, flexors

White matter contains _________________ while grey matter contains _____________.

fiber tracts, cell bodies

The main purpose of the sympathetic nervous system is ___________________.

fight of flight response, mobilize resources

Groups of fiber tracts that run together within the same region of the spinal cord are called ______________________.

funiculus - contains one or more fiber tracts

What does the enteric nervous system control?

gut motility, works semi-independently from the symp/parasympathetic, loosely organizes cells and networks in walls of digestive system, facilitates communication within the gut.

Autonomic nervous system two main functions are __________________ and ___________________________.

homeostasis and gut motility

Signs of UMN lesion:

hyperreflexia, very tense muscles and atrophy is delayed (disuse atrophy)

Damaged LMN results in a _________________________ reflex

hypoactive or absent

What kind of neurons communicate within and between spinal cord segments?

interneurons - inbetween spinal input (peripheral nerves) and output (efferent)

What vertebral structure do spinal nerves exit the spinal cord through?

intervertebral foramen

what do gamma motor neuron innervate?

intrafusal muscles fibers - used for proprioception and reflexes

Autonomic nervous system is under ______________________ control and targets _____________________ muscle(s) and glands.

involuntary, smooth and cardiac

The lateral funiculus carries ________________ tracts and is located between the dorsolateral and ventrolateral sulci

mixed - ascending and descending tracts

Is the myotactic reflex mono/polysynaptic?

monosynaptic

Polysynaptic reflex

more than one synapse in CNS, more common

Signs of LMN lesion

paresis/paralysis, hyporeflexia to aflexia, atrophy occurs rapidly and dec muscle tone

White matter includes ascending fiber tracts. Where do these carry information to and from?

periphery to brain

What needs to be removed from myosin to terminate a contraction?

phosphate needs to be removed Myosin light chain phosphatase dephosphorylates the myosin

What are the three meningeal layers that cover the spinal cord?

pia mater - inner most coating spinal cord and spinal rootlets Arachnoid membrane - middle layer Dura mater - outermost layer

Is tendon-jerk reflex mono/polysynaptic?

polystnaptic

Is the withdrawal reflex monosynaptic or polysynaptic?

polysynaptic, comes in a dorsal horn, synapses on many interneurons, eventually getting to motor neurons that synapse on the flexors or extensors

Is the panniculus reflex poly/monosynaptic?

polysynaptic, interneurons project onto alpha-motor neurons in ventral horn at C8, T1, and T2 that go to the cutaneous trunci muscle.

The release of ADP and Pi from the myosin head causes __________________________________ to occur

power stroke - pulling the actin closer to the dense body

dorsal and ventral roots are comprised of __________________.

rootlets

The nucleus pulposus in the intervertebral disc has a _________________ consistency while the annulus fibrosis is _____________ forming a ring.

semifluid/jelly-like, fibrous

What are some signs of equine motor neuron dz?

shifting weight on feet, prefernce for laying down, weight loss, and an awkward stance when standing.

SYMPATHETIC nervous system has a __(short/long)__ presynaptic neuron and a __(short/long)__ postganglionic neuron

short, long

What do alpha motor neurons innervate?

skeletal muscle

ANS targets _________________, _____________________, and ___________________.

smooth muscle, cardiac muscle, and glands

bilateral loss of a reflex = damage to __________________ whereas damage to a ___________________ = unilateral loss of function

spinal cord segment; nerve

What causes an AP in smooth muscle?

stretch of vessel wall or NT causing the Ca voltage gated channels in caveolae to open.

The ________________________ is formed by a cord of MENINGES at the caudal end of spinal cord.

terminal filament

Sympathetic nervous system is controlled by the ___________________ nerves including T1-L4/5

thoracolumbar

intermediolateral neurons are located in the _____________________________region and _______________________ portion of the spinal cord and are part of the autonomic nervous system.

thoracolumbar; sacral

What is the parasympathetic nervous system used for?

to conserve and store energy "rest and digest"

If a horse can walk better than it can stand is most likely has what dz?

Equine motor neuron dz

What spinal cord dz is characterized by death of lower motor neurons whose cell bodies are in the brainstem and spinal cord?

Equine motor neuron dz

Where do MOST of the Ca come from for smooth muscle contraction?

Extracellular fluid, also comes form SR but this is not well developed like in skeletal muscles so there is not as much Ca stored.

The somatic nervous system is under __________________ control and innervates ___(striated/unstriated)____ musculature through __(single/multiple)___ motor neuron(s) on a muscle fiber at a motor endplate.

voluntary, striated, single

Other names for flexor reflex

withdrawal reflex or nociception reflex

Are muscles innervated by more than one spinal nerve?

yes, spinal nerves come together to make peripheral nerves. Ex) bicep is innervated by the sciatic nerve that is comprised of branched from the L6, L7, and S1 spinal nerves

An example of degenerative disk disease is _________________________ Type I and II disk dz

Hansen's

What type of neurons are responsible for hardwiring spinal reflexes?

Interneurons - this is why new born animal have reflexes

Do smooth muscles have long or short contractions?

Long, Ca levels stay higher longer than in skeletal muscles because the Ca is removed slowly. Ca channels open slowly, stay open longer, deactivate slowly, and Ca accumulates slowly in smooth muscle cells

Are multi-unit smooth muscles contacted by one or multiple neurons? Are the cells coupled with gap junctions?

Multiple neurons, no to little coupling between cells. Found in iris and piloerector muscles of skin (goosebumps). Used in precise coordination

Will spinal reflexes be effected by damage further down the spinal cord?

No

Do smooth muscles have T-tubules?

No - but skeletal muscles do

Do smooth muscles have sarcomeres?

No - this is why there are no striations

Do you need the brain in a reflex arc?

No BUT the brain may play a role in communicating with the body

Can the crossed-extensor reflex be done on an animal laying down?

No, if the reflex still occurs that means that there is damage to the UMN, some kind of loss in communication

Are sensory neuron's bodies located in the dorsal horn?

No, no sensory neuron bodies but does contain interneuron cell bodies.

Are single-unit smooth muscles contacted by one or multiple neurons? Are the cells coupled with gap junctions?

One neuron, cells are coupled. Found in visceral organs, GI, bladder, uterus. Wave like contractions

What pumps are used to terminate a smooth muscle contraction?

SERCA - puts Ca in the SR Na/Ca exchanger - sends out Ca and brings in Na (This may not be an actual pump)

Reflex arc includes

Sensory Receptor - afferent nerve fiber Afferent Nerve fiber - info to spinal cord Central integration - spinal cord Efferent Neuron - LMN Effector - muscle, gland

____________ neurons send info BACK to the spinal cord, entering through the ______________ root

Sensory, dorsal

Is Hansen's Type II disk dz due to trauma or progessive?

Slowly progressing - fibroid gradually protrudes but remains within the annulus, compression is gradual. Appears in dogs 4-5yrs old

What shape are smooth muscle cells? Are they striated?

Spindle, no striations

How does extracellular Ca enter the smooth muscle cells?

Through caveolae in the sarcolemma

Perineal reflex steps:

•Light stimulation of perineum with forceps •Response: contraction of anal sphincter muscle and flexion of tail •Best test of function of sacral spinal cord segments and associated nerve roots

Can smooth muscles be contacted by more than one NT?

Yes - NE or Ach typically

What are the four anatomical features of the ANS?

1) controlled by 2 neurons connected in series 2) lower motor neurons that innervate organs 3)contact between visceral motor neurons and viscera are less differentiated than NMJ seen in somatic nervous system (varicosities or swellings) 4)ANS controlled by the hypothalamus, brainstem cranial nuclei, reticular formation, and spinal cord.

What are the steps in a smooth muscle contraction?

1. Calcium enters cell from outside 2. Calcium binds to calmodulin, creating the Ca-CAM complex 3. Ca-CAM complex activates the myosin light chain kinase 4. MLCK phosphorylates the myosin light chains in myosin and inc myosin ATPase activity 5. Myosin allows for crossbridge formation, and crossbridge cycle happens, so contraction happens This is a slow process in smooth muscles

What is bound to myosin head when they form crossbridging?

ADP and Pi

For a muscle contraction to continue you need __________ and ________levels to be high.

ATP and Ca

Where is smooth muscle found in the body?

All over - eyes, air ways, stomach, intestines, bladder, blood vessels, repro tract. Basically all the hollow organs

What are the three types of afferent neuronal cell bodies?

Alpha, gamma, and interneuron

which spinal nerves comprises the brachial plexus?

C6-8 and T1 & 2

Which spinal cord segments are used in the biceps reflex? Which nerve?

C6-C8, musculocutaneous

Which spinal cord segments are used in the extensor carpi radialis reflex? Which nerve?

C7-T2, radial n.

What structure anchors actin and myosin in smooth muscle?

Dense bodies (analogous to Z lines in skeletal muscle)

which spinal nerves comprises the lumbosacral plexus?

L4-7 and S1-3

Which spinal cord segments are used in the patellar reflex? Which nerve?

L4-L6, femoral n.

Which spinal cord segments are used in the pelvic flexor reflex? Which nerve?

L6-S1, sciatic n.

_______________ neurons from the spinal cord innervate skeletal muscles, leaving the spinal cord through the VENTRAL root.

Lower motor

How do you perform the panniculus reflex?

Pinch skin until there is a shiver or tightening of the skin. There will be a bilateral response even though the stimulus is just unilateral

What kinds of Hansen's disk dzs are chronic and which is acute?

Type I - acute Type II - chronic

What structure divides the ventral spinal cord into right and left halves?

Ventral median fissure

what sulcus of the spinal cord do efferent (motor) neurons exit through?

Ventrolateral

What vitamin deficiency has been linked to equine motor neuron dz?

Vit E

What is the purpose of smooth muscle?

carry out unconscious internal movements to maintain the body in good working condition.

Where does the C8 spinal nerve exit the spinal cord?

caudal to C7 vertebra, all spinal nerves leave caudal to their associated vertebra.

________________ and __________________ enlargements on the spinal cord are where extra neurons innervate limbs.

cervical (thoracic limb), lumbar (pelvic limbs)

What elicits a myotactic relex?

change in posture

What is cauda equina syndrome?

compression of a nerve in the cauda equine that leads to pain, atrophy of muscles, or incotinence

What disc dz is characterized by "moth-eaten" appearance of white matter?

degenerative myelopathy

What disc dz is characterized by diffuse degeneration of spinal cord myelin and axons of the white matter of spinal cord?

degenerative myelopathy

What disc dz is characterized by deficient hopping, postural thrust, and proprioception issues?

degenerative myelopathy - older onset (6-9yrs)

What structure is pulled together in a smooth muscle contraction?

dense bodies

The pia mater meningeal layer thickens to form a longitudinal cord called the ______________________ ligament that attaches laterally midway between dorsal and ventral roots.

denticulate

What are the two supporting structures of the spinal cord?

denticulate ligament and terminal filament

The ventral funiculus carries ______________________ tracts and is located between the ventrolateral sulcus and ventral median fissure

descending

What vertebral disc dz is caused by inflammation?

discospondylitis - caused by bact/fungal inf

Afferent processes are located in the __________ horn and are used for pain, vibration, touch, and proprioception.

dorsal

Which sulcus divides the dorsal spinal cord into right and left halves?

dorsal median sulcus

Sensory input enters the spinal cord at the ______________ horn and motor output exits through the __________________ horn.

dorsal, ventral

what sulcus of the spinal cord do afferent (sensory) neurons enter through?

dorsolateral

PARASYMPATHETIC nervous system has a __(short/long)__ presynaptic neuron and a __(short/long)__ postganglionic neuron

long, short

What happens to myosin heads when they hydrolize ATP?

myosin head is reoriented and energized

What is happening during Hansen's Type I disk dz?

nucleus pulposus calcifies, rigidity leads to tears in annulus allowing for nucleus material to extrude into vertebral canal. Usually acute and occurs in young animals (2mo-3yrs). Leads to hypoxia, edema, ischemia, damage to spinal cord causing necrosis and demyelination.

How is the intervertebral disk changing in Hansen's Type I disk dz?

nucleus pulposus degenerates and become calcified not allowing it to absorb compression pressure.

What changes are occurring to the intervertebral disc in Hansen's Type II disk dz?

nucleus pulposus degenerates and is replaced with fibrocartilage.

the intervertebral disc is made of the _________________________ and ____________________________.

nucleus pulposus, annulus fibrosis

Withdrawal reflex steps

•Pinch or squeeze paw = animal withdraws limb •SENSORY Receptor = pain receptor = bare nerve endings •Afferent fiber = flexor reflex afferents -2 different fiber types carry fast pain or slow, long lasting pain respectively -Afferents enter spinal cord, synapse in dorsal horn -Central integrator: Polysynaptic pathway final termination on motor neurons in ventral horn -CROSS EXTENSOR REFLEX (Reciprocal Innervation) - This is part of the withdrawal reflex and should not be considered a separate reflex.

tendon-jerk reflex steps:

•Stretch receptors •Afferent = large myelinated axon •Central integration = synapse on extensor alpha motor neuron •Synapse on inhibitory interneuron •Interneuron synapses on flexor muscle alpha motor neurons •Reciprocal innervation of agonist (extensor) EPSP and antagonist (flexor) IPSP