The Motor System Flashcards
What is the target tissue in the somatic motor pathway?
Always skeletal muscle
What type of signal is produced during somatic motor pathway?
Always excitatory
What receptors are at the synapse of the somatic motor pathway?
Nicotinic ACg receptors
What are the four ways neural reflexes can be classified?
- Efferent division
- Integrating region within the central nervous system
- Time at which the reflex develops
- The number of neurons in the reflex pathway
What are monosynaptic reflexes?
When there is a single synapse between the afferent and efferent neurons
What are polysynaptic reflexes?
When there are two or more synapses between the afferent and efferent neurons
What is a motor unit?
Single motor neuron and all the fibres it innervates
What are alpha motor neurons?
Somatic motor neurons that innervate skeletal muscle contractile fibres
What are proprioceptors?
Sensory receptors within the muscle
What type of reflex is the skeletal muscle reflex?
A monosynaptic reflex
What are the three types of proprioceptors?
- Joint receptors
- Golgi tendon organs
- Muscle spindles
What does the golgi tendon organ do?
It links the muscle and the tendon and responds to muscle tension
What does the muscle spindles do?
Respond to muscle stretch
What are muscle spindles embedded in?
Extrafusal muscle fibres
What do muscle spindles contain?
Intrafusal muscle fibres
What are the non-contractile regions of muscle spindles wrapped in?
Sensory nerve endings which respond to stretch
What are the contractile ends of muscle spindles wrapped in?
Innervated by gamma motor neurons
What does tonically active mean?
Always on
What is the stretch reflex?
When muscle spindle stretch the muscle spindle afferents fire more frequently resulting in reflex contraction
What is alpha gamma coactivation?
When extrafusal fibres shorten gamma motor neurons fire to shorten intrafusal fibres
What is the flexion and crossed extensor reflex and what type is it?
A polysynaptic reflex that removes a limb from a painful stimulus
What is crossed extensor reflex?
Compensatory change in other limb to retain posture
Do reflexes require input from teh cerebral cortex?
No
What is the role of the cerebellum?
To fine tune movements
What are the three phases of voluntary movement?
- Planning
- Initiation
- Exeution
What integrates stretch and flexion reflexes?
Spinal cord
What integrates postural and hand eye reflexes?
Brain stem
What integrates voluntary movement?
- Cerebral cortex
- Cerebellum
- Basal ganglia
What are corticospinal tracts?
Nerves that run from motor cortex to the spinal cord and control voluntary movement
Where do corticospinal tracts usually cross over?
At the pyramids of the medulla
