Muscles 2 Flashcards
brain regions involved in voluntary movement
primary motor cortex (premotor cortex, basal ganglia, thalamus, midbrain, cerebellum)
corticospinal tract
descending tract (ventral and interior lateral white matter)
upper motor neuron
brain to spinal cord
alpha (lower) motor neuron
spinal cord to muscle
motor unit
a single motor neuron and all the muscle fibres it innervates
neuromuscular junction
area where motor neuron makes synaptic contact with the muscle fibre
All muscle fibers respond….
simultaneously
ALS
amyotrophic lateral sclerosis; upper and lower motor neurones degenerate leading to weakness from disuse (of muscles)
three components of neuromuscular junction
- presynaptic motor neuron filled with synaptic vesicles
- synaptic cleft
- post synaptic membrane of skeletal muscle fibre
motor end plate
region of sarcolemma at the neuromuscular junction
Theres usually ____________ that cover the neuromuscular junction
schwann cells
junctional folds
increase surface area to fit in as many nicotinic ACh receptors as possible
motor neuron vesicles contain…
acetylcholine
muscle sarcolemma contains…
nicotinic acetylcholine receptors
nicotinic acetylcholine receptors are….
monovalent cation channels
opening of Each receptors require…
two ACh molecules
Na+ entry through nACh receptors….
generates an excitatory end-plate potential and initiates an action potential
Once AP’s stop firing in the alpha motor neuron, acetylcholine in the synaptic cleft must be,,,,
removed and diffuse away or be broken down
What does ACh break down into?
acetate and choline
what breaks down ACh?
acetylcholinesterase
what makes acetylcholine?
choline (recycled) and acetyl CoA
where is acetyl CoA produced?
from mitochondria
choline acetyltransferase
produce acetyl CoA in mitochondria
myasthenia gravis
disorder of neuromuscular transmission; body produces antibodies that bind to ACh receptors; causes degeneration of postjunctional folds
sarcoplasmic reticulum
specialized calcium storage organelles organized within t-tubules
t-tubules
how sarcolemma penetrates into muscle fibre
excitation-contraction coupling
process by which electrical excitation of surface membrane triggers an increase of [Ca2+] in muscle
rise in [Ca2+] intracellularly
triggers contraction in all muscle types
How can Ca2+ enter the sarcoplasm?
- from extracellular space via voltage gated channels
- released from storage reservoir of sarcoplasmic reticulum
T-tubulespenetrate the muscle fibre and surround myofibrils at which points in each sarcomere?
at the A and I band junctions
cisternae
specialized end regions of sarcoplasmic reticulum
triad
t-tubules with two cisternae
