block 5 lecture 11 spinal reflexes Flashcards
what are the three main types of movement?
reflex, rhythmic and voluntary
what does the dorsal side of the spinal cord receive input from?
the senses
how do the sensory nerves enter the spinal cord?
dorsal roots
where does the spinal cord get bigger?
cervical and lumbar enlargements
where is the cervical enlargement?
C3-T1
where is the lumber enlargement?
L1-S1
how are the motor neurons in the grey matter of the spinal cord organised?
somatotopically - in relation to the body
what controls the axial parts of the body?
medial neurons
what do lateral neurons control?
distal parts of the body
what are alpha neurons part of?
final common pathway
where do upper motor neurons remain?
the central nervous system
what do lower motor neurons do?
send axons directly to muscles
what are the head muscles controlled by?
motor neurons in the brain stem
where are the muscles of the body motor neurons?
spinal cord
where are alpha neurons found in the spinal cord?
ventral horn
where do the alpha motor axons go?
the axons pass through the ventral root and through spinal nerve and terminate at neuromuscular juntsion
why are the ALPHA motor neurons?
thickest neurons meaning very rapid conduction
what is the main neurotransmitter in muscle control?
acetylecholine
what does acetylecholine do?
initiate muscle contraction
what does myelination allow?
saltatory conduction
where is sensory input gathered from?
cerebral cortex, spinal interneurons, muscle spindle and skin
what is the most common motor neuron disease?
ALS - amyotropic lateral sclerosis
what happens in ALS?
progressive degeneration of the alpha motor neurons
what are the symptoms of ALS?
muscle weakness, atrophy, difficulty breathing and swallowing and affect on cognitive function
in ALS why are the eyes the last to be effected?
highly vasculated and highly innervated
what is a possible cause of ALS?
too much glutamate in the brain
what blocks glutamatergic neurotransmission?
riluzole
does the sensory neurons always synapse with the interneurons in the reflex arc pathway?
may synapse directly with motor neuron
where are muscle spindle in relation to normal muscle?
located parallel to muscle fibers
what are normal muscle fibers called?
extrafusal muscle fibers
what are the spindle muscle fibers called?
intrafusal
how does the neuron carry information to the spinal cord?
1a afferent neuron wraps around the muscle spindle and goes into the dorsal root of the spinal cord
what neuron innervate intrafusal muscle fibers?
gamma motor neurons
what can muscle spindle detect?
changes on the muscle
what is the stretch reflex?
myotactic reflex,
what is the patella tendon tap?
this is a stretch reflex
what happens when the tendon is tapped?
the quadriceps are stretched, 1a muscle spindle is activated, impulses travel to the spinal cord and activate motor neurons which release acetylecholine and contract the quads
what is the stretch reflex reciprocal inhibition?
while stretch reflex is occurring, collateral branch send information to inhibitory interneruon to inhibit antagonistic muscle
what does the mono synaptic stretch reflex control?
contracts agonist muscle
what dose the reciprocal inhibition control?
inhibits antagonistic muscle
in the inverse stretch reflex pathway what is the sensory organ?
golgi tendon
where is the golgi tendon?
between tendon and muscle fibers, runs in series with the extrafusal fibers
what happens in the inverse stretch reflex pathway?
it send out 1b afferent which synapses with interneruon in the spinal cord which inhibits the alpha motor neuron to stop muscle contracting
what is the golgi tendon innervated by?
1b
what is the threshold of the golgi tendon like?
very high - you need alot of contraction to activate
what is the golgi tendon made up of?
collagen fibers
how are the 1b activated?
force acts on the collagen fibers in the tendons to increase tension causing compression of the fibrils which activates dendrites of the 1b afferent
what happens in the flexor withdrawl reflex?
nociceptors are activated, impulses are sent along afferent neurons………….
