Lab 4 Reflexes Flashcards
why body has reflexes
protect tendons from rupturing and muscles from overstretching
why are reflexes tested
part of larger neurological examination, tests functional integrity of nerves
name of grooves
sulcus
name of elevated folds
gyrus
fMRI and PET scan
shows anatomy and metabolic activity of brain - used to study pre and post central gyrus
precentral gyrus
- alternate name
- main function
motor cortex, houses cell bodies of UMN, sends motor commands to effectors
postcentral gyrus
- alternate name
- main function
somatosensory cortex, processes sensory information
what determines amount of area in pre/postcentral gryus given for each body part
density of receptors is proportional to amount of area in the brain dedicated to the body part
relation of pre and postcentral gyrus in terms of location mapped to each body part
they are mirrors of each other
decussation
crossing over of sensory and motor neurons in the spinal tract / medulla oblongata to the opposite side
tract vs nerve
tract = axon bundle in CNS nerve = axon bundle in PNS
ascending vs descending tract
ascending = sensory neurons descending = motor neurons
ascending tract naming scheme
- explain anterior spinothalamic and posterior spincerebellar
- name based on start to end
- anterior spinothalamic = spine –> thalamsu
- posterior spincerebellar = spine to cerbellum
name of pain receptors
nociceptors
role of thalamus
relay center for all sensory information except smell - amplifies signals coming in
2 types of descending tracts and their alternate names
- pyramidal = corticospinal
- extra pyramidal = reticular, does not go through pyramids
- pyramids are structure in medulla oblongata
why is coordinated movement so hard?
- involves a lot of parts of the brain which send a mix of excitatory and inhibitory signals to different skeletal muscles
- involves reciprocal loops that are underdeveloped in infants
LMN vs UMN damage
- LMN damage = flaccidity, muscular atrophy
- UMN damage = exaggerated reflex since UMN usually inhibits LMN
dorsal root
- house sensory neurons coming in
ventral root
- houses motor neurons going out
reflex arch series of events
sensory stretch receptors –> stimulate sensory neurons –> spine/brain where it may connect to interneurons –> motor neuron –> effector tissue
monosynaptic reflex
1 synapse only between sensory and motor neuron - no interneuron
2 types of reflex based on type of muscle
- autonomic = smooth muscle, glands
- somatic = skeletal muscle under voluntary control
2 types of reflex based on synapse location
- cerebral = in brain
- spinal = in spine
Plantar reflex stimulation
- stimulate nociceptors by pressing from lateral (outside) of foot to big toeo
plantar reflex responses
- positive babinski = dorisflexion and plantar extension, seen in babies.
- dorsiextension and plantar flexion seen in healthy adults
what does plantar reflex test
tests corticospinal tract that houses UMN
plantar reflex response in health adult, adult with spinal damage, otherwise healthy baby
- healthy adult = toes curl in
- adult with spinal damage = toes curl out
- healthy baby = toes curl out because UMN are not as myelinated yet
series of events for plantar reflex
- nociceptors in foot –> sensory neuron –> S1 and synapse with LMN –> foot
- UMN usually prevents sensory information from traveling to L4/L5 which stimulates the toes to extend
pupillary light reflex - cerebral or spinal?
cerebral
what is the effect of the pupillary light reflex
both pupils contract
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why does the pupillary light reflex cause constriction in both eyes
light –> information sent to pretectal area of the brain –> interneuron goes to BOTH Edinger westphal nuclei –> motor command sent to ciliary ganglion –> pupil constriction
hypo vs hyper reflexive
hypo = very little reflex hyper = exaggerated reflex
how to increase reflexivity
jendrassik maneuever - patient locks fingers together and bears down
5 components of reflex arch
sensory receptors, sensory neuron, interneuron, motor neuron, and effector
ankle reflex - stimulation, nerve, and expected effect
- hit large tendon in the back of ankle, food should drop, medial popliteal nerve
patellar reflex - stimulation, nerve, and expected effect
- hit patellar tendon, leg should kick out, test femoral nerve
tricep reflex - stimulation, nerve, and expected effect
- hit tricep tendon in the back of elbow, arm should jerk, test radial nerve
bicep reflex - stimulation, nerve, and expected effect
- cover tendon with thumb and hit, arm should jerk and rotate in (or maybe just the fingers), test musculocutaneous nerve
