lecture 16- somatic motor system and skeletal muscle Flashcards
primary motor cortex
contains cell bodies of upper motor neurons
innervation of lower motor neurons in the primary motor cortex
- axons project down though brainstem and spinal cord to innervate lower motor
neurons - lower motor neurons are part of peripheral nervous system; project to and
innervate skeletal muscle
upper motor neurons are part of the
CNS
peripheral pathway consists of —-
1 lower motor neuron
lower motor neurons innervate —–
skeletal muscles
where does the 1 lower motor neuron originate from
- in the brain?
- in the spinal cord
in the brain= cranial nerve nuclei
in the spinal cord= cell bodies in ventral horn
where do axon collaterals branch out?
at their distal end
(near the muscle targets)
- each collateral will synapse with 1 muscle fiber
what does the neuromuscular junction consist of?
- axon terminals
- motor end plates on the muscle membrane
- Schwann cell sheaths
what do Schwann cells do in terms of the NMJ?
secrete chemical signals for the formation and maintenance of the NMJ
what is the motor end plate?
a specialized region of the muscle membrane that contains high concentrations of nicotinic ACh receptors
*membrane surface has many invaginations to increase SA
what is Acetylcholine (ACh) metabolized by?
acetylcholinesterase (AChE)
how does a nicotinic ACh receptor work?
skeletal muscle nAChR are diff from the ones in the autonomic nervous system
-when the channel opens, K+ flows out and Na+ and Ca2+ flows in
-depolarizing end plate potential
-excitatory
neuromuscular transmission is ALWAYS
excitable
muscle equivalent:
muscle cell
muscle fiber
muscle equivalent:
cell membrane
sarcolemma
muscle equivalent:
cytoplasm
sarcoplasm
