segmental motor circuits Flashcards
1
Q
classes of movement
A
- reflex (stereotyped)
- voluntary (motor cortex)
- cyclical (programmed)
2
Q
motor unit
A
- basic lowest level
- alpha motor neuron
- in ventral horn
- sends axon out into periphery
- connects to skeletal muscle fibers
- decides whether muscle will contract or not
3
Q
lower motor neurons
A
ventral horn of gray matter of spinal cord
4
Q
3 types of input to a LMN
A
- from local interneurons (neighboring neurons)
- from sensory afferents (pain, temp)
- from higher centers (descending tracts)
5
Q
reflexes can be classified as
A
- monosynaptic (stretch)
- disynaptic (inverse stretch)
- polysynaptic (withdrawal/flexion)
6
Q
monosynaptic (stretch) reflex
A
- afferent and motor neurons
- MOST IMPORTANT
- ex: muscle spindle
7
Q
muscle spindle
A
- intrafusal muscle fibers
- annulospiral fibers that
- sensory fibers go to dorsal root and synapse with motor neuron
8
Q
stretch reflex circuit (spindle)
A
- muscles spindle senses stretch
- spindle activated
- signal to DRG
- signal goes to alpha motor neuron to synapse
- signal to same muscle
- contraction
9
Q
stretch reflex (AKA: myotatic, deep tendon)
A
10
Q
another one
A
11
Q
knee jerk reflex
A
- tendon of quads is hit (stretched)
- causes alpha motor neuron to fire
- quad contracts
- leg kicks
12
Q
why is the reflex so important?
A
- reflexes help muscles contract
- keeps the horse from collapsing
13
Q
stretch reflex functions
A
- holds muscle length constant
- maintenance of erect posture
- responsible for muscle tone
14
Q
what is muscle tone?
A
basal level of contraction of muscle
- only when you are wake
15
Q
gamma motor system
A
- A-gamma motor neurons come out of ventral horn
- smaller motor neurons that go to the spindle
- these can stretch the muscles spindle