week 5 Flashcards
what cord segments does the pudendal nerve come from
S1-3
what are the branches of the pudendal nerve?
dorsal n. of penis (sensory) caudal rectal (motor) nerve to urethralis sphincter perineal nerves (sensory to rectum)
what can you see when the pudendal nerve is damaged
fecal and urinary incontinence; perineal reflex absent; in large animals can see exposure of penis due to flaccid paralysis of retractor penis muscle
what is the definiton of the spinal reflex
man made instaneous motor response to a man made afferent stimulates;
spinal reflexes are automatic and only require
afferent neuron
3 or more spinal cord segmetns
efferent neuron
are we concerned with the afferent neuron in spinal reflex
no; not true with cn reflex
patellar reflex involves what spinal cord segments
L4, L5, L6
Will reflexes work without umn? without brain?
yes! wont be normal; but will be there
what occurs during a reflex
Afferent neuron, spinal cord, ascending projection, then descending projecting neuron;
we look for a _______ response mediated by the lmn, the efferent neuron in the reflex
motor
what are the two important questions to ask during a reflex?
does it work?
is it normal?
it works,
LMN intact
if it does not work
lmn damaged
if it is normal
lmn intact
if it is not normal and depressed/absent
some Lmn damage
if it is not normal and exaggerated
umn dammage
grading reflexes +0
Absent; lmn problem (areflexia)
grading relfexes +1
depressed; lmn problem (hyporeflexia)
grading reflexes +2
normal; normoreflexia
grading reflexes +3
exaggerated; umn problem (hyperreflexia)
grading reflexes +4
clonus; UMN problem;
what are the components of a reflex (except tendon reflexes- no interneurons)
receptor, afferent neuron (all excitatory), interneuron (excitatory or inhibitory); efferent neuron (excitatory); effector organ
multisynaptic reflexes
internurons involved
monosynpatic relfexes
tendon relfexes; no interneurons
withdrawal reflex is what kind of reflex
multisynaptic, but reliable!
withdrawal reflex involves
stimulus (nociception) at any nerve;
flexion of all joints on thoracic limb
If withdrawal reflex is working, what else is working?
C6-T2 spinal nerves and spinal cord segments
is the crossed extensor a normal reflex?
Not normal in recumbant animal; normal in a standing animal because the brain should sense that you are in lateral recumbancy
what does crossed extensor indicate?
umn damage cranial to the limb you are testing (considered a 5th UMN sign)
what are the tendon reflexes?
biceps reflex
triceps reflex
extensor carpi radialis reflex
extensor thrust reflex (also hindlimb)
how do you do the biceps reflex?
hook finger around tendon, then hit finger on upper limb; motor response should be flexion of the elbow joint (in the horse just look for m. contraction)
afferent and efferent nerve of biceps reflex
musculocutaneous
if the biceps reflex is absent
means nothing; but still put +0 on exam report
if biceps reflex is working
musculocutatneous nerve is working (LMN are working)
how do you do the triceps reflex
rotate limb to get elbow pointed out laterally; want to see extension or feel for extension of limb
what is the afferent and efferent nerve for this reflex
radial nerve
how do you do the extensor carpi radialis reflex
tap muscle belly (using pointed end); can do on recumbant horse right at musculotendinous junction
what is the afferent and efferent nerve for the extensor carpi radialis reflex
radial nerve
what does the extensor thrust reflex measure
normal tone
how do you do the extensor thrust reflex?
sudden, mild/consistent pressure against pads; should fell resistance
what is the afferent nerve for the extensor thrust reflex
median/ulnar (tibial on hindlimb)
what is the efferent nerve for the extensor thrust reflex
all nerves innervating extensors
what does the withdrawal relfex of the hindlimb test?
L4-S2 nerves and cord segments
how is the patellar reflex different in the horse
horse has 3 tendons of quadriceps femoris; medial intermediate and lateral
how do you do the cranial tibial reflex?
not reliable; tap cranial tibial m. belly (pointed hammer); and should see flexion of tarsal joints/hock
what is the afferent and efferent nerve of the cranial tibial reflex
peroneal nerve.
how do you do the gastrocnemius reflex
tapping common calcaneon tendon while holding pes; cand do in horse if recumbant (dont hold pes in horse)
what do you see in the perineal reflex of the horse
see contraction of the external sphincter and tail clamps down
what is the afferent nerve of the perineal relfex
pudendal nerver (perineal nerve branch)
what is the efferent nerve of the perineal reflex
pudendal nerve (caudal rectal nerve branch; S1-S3)
What nerve is responsible for the tail clamp
caudal nn. and caudal spinal cord (CD1-5)
what is the bulbourethral reflex
stroke bulb of penis; relfexive contracteion of sphincter
what nerve is responsible for the bulbourethral reflex
pudendal nerve
bladder and rectal tone
not a reflex; but can assess via palpation externally or per rectum
what is the afferent nerve for the panniculus reflex
any nerve from T3 to L3; they then synapse on interneurons
interneurons of panniculus reflex ascend to
C6-T3 (C8-T1)
efferent neurons of panniculus reflex
lateral thoracic nerve
response of panniculus reflex
contraction of cutaneous trunci
is the panniculus reflex reliable?
not always
once panniculus reflex is established, how do you localize futher
caudal to lesion of spinal cord- panniculus reflex wont work; cranial to lesion of spinal cord, panniculus rreflex will work; usually within 3 cord segments of panniculus cut off
what trunk reflexes are only done in the horse
upper cervical and lower cervical
upper cervical reflex
tap skin in C1-C3 vertebral area; motor response- ear flicks forward; efferent nerve is CN III
lower cervical reflex
tap skin just cranial to shoulder (over brachiocephalicus m.); afferent and efferent is C3-C6
