exam two (ch. 13) Flashcards
motor neurons located in the ventral horn of spinal cord and sends axons through the ventral root
lower motor neurons
what motor neurons directly trigger muscles to contract
alpha motor neurons
alpha motor neurons in charge of proprioception
gamma motor neurons
know steps of excitation contraction coupling and sliding filament model
a single action potential leads to a muscle twitch and the summation of them leads to
contraction
greatest frequency of action potentials =
smoothest contraction
there are two types of white muscle fibers
fast fatigable and fatigue resistant
white muscle fibers are found in fast motor units such as
fight or flight responses
red muscle fibers contain many ______ and contract and fatigue _____
mitochondria; slowly
motor neurons in the ventral horn controlling flexors lie ___ to those controlling extensors
dorsal
motor neurons in the ventral horn controlling axial muscles lie ____ to those controlling distal muscles
medial
what are three inputs to alpha motor neurons
- upper motor neurons
- proprioceptive input from muscle spindles
- spinal interneurons (excitatory or inhibitory)
what controls the motor neuron in the spinal cord (proprioceptive control)
sensory (proprioceptive) feedback from muscle spindles and stretch receptors in muscle fiber
the sensory proprioceptive signal is carried by __ ______sensory axon
a alpha (large and myelinated)
the stretch reflex is a ____ feedback loop
monosynaptic
the discharge rate of A alpha Ia sensory axon depends on ____ of the stretched muscle
length
the ___ motor neuron is needed to maintain the myotatic stretch reflex
gamma
the gamma motor neuron changes set point of the stretch reflex and keeps tension on ___ ____
intrafusal fibers
the ___ ____ ___ is located at the junction of muscle and tendon; monitors muscle tension
golgi tendon organ
the activation of Ib (alpha a) sensory axon by the golgi tendon organ excites an _____ interneuon which in turn inhibits what?
inhibitory; alpha motor neuron (reducing force of contraction)
the proprioceptive axons in joint tissues respond to what kind of movement
angle, direction, velocity
contraction of one muscle accompanied by relaxation of antagonist muscle is called
reciprocal inhibition
myotatic reflec in arm: contraction of biceps muscle is ____ and relaxation of triceps is ____ because of an ___ ____
monosynaptic, polysynaptic , inhibitory interneuron
flexor withdraw reflex
Step on tack
2. Activate Aδ (pain) axon
3. Pain axon activates
excitatory interneurons
in adjacent segments of
spinal cord
4. Interneurons activate
alpha motor neurons
innervating flexor
muscles (not shown –
extensor muscles on that
side would need to relax)
when you have the flexor withdrawl reflex you dont fall over because of the ___ ____ ___
crossed extensor reflex
the crossed extensor reflex involves both inhibitory and excitatory interneurons; one of which _____
crosses
spinal motor programs for walking require __ ___ ____
central pattern generator
know proccess of rhytmic activity in spinal interneuron
walking without thinking requires continuous excitatory input from ___ ___ and input from both excitatory and inhibitory motor neurons
motor cortex
primary efferent neurons enter via the vertebral colummn via the ____ root
dorsal
four types of primary afferent neurons
A alpha, A beta, A delta, C
