session 9 Flashcards
smooth muscle
digestive/organs, aren’t relevant to movement
cardiac muscle
heart, not relevant to movement
skeletal (striate)
muscles are our primary focus, voluntary responses to the environment
muscles
innervated by only a single axon, to avoid conflicting motor messages
The Neuromuscular Junction
synapses between motor neurons and muscle fibers, mostly use acetylcholine (ACh, causes a singular contraction in a muscle)
Fast Twitch fibers
facilitate quick bursts of movement, and fatigue very quickly (sprinting)
anaerobic- build up a debt to pay back later
Slow Twitch Fibers
Facilitate less vigorous activity and don’t really fatigue (walking)
aerobic-pay as you go
Proprioceptors
sense stretch in muscles sends a message to spinal cord to counteract the stretch and maintain balance
Reflex arc
the tendon struck by the hammer is a proprioceptor, which is what triggers it
motor cortex
Primary motor cortex (frontal lobe), complicated motor tasks such as driving or typing, less important for simpler actions like smiling or coughing
central pattern generators
mechanisms in the spinal cord that produce patters of output, sneezing, smiling, “wet dog shake”, natural smiles
“ballistic movements”
meaning once they’re started they can’t be stopped, like a wet dog shake
The Basal Ganglia
3 structures (globus, pallidus, putamen, caudate nucleus), can tell the thalamus to stop, inhibiting the motor movement
Prefrontal cortex
anticipates likely outcome of actions, when distracted makes silly motor mistakes without realizing it
thalamus
always generating motor output, the 3 structures of the basial ganglia form a complex inhibition system fueled by dopamine
voluntary movements
basal ganglia, slower and more deliberate
elicited movements
spinal cord and reflexes, faster and less controlled
corticospinal tracts
starts in the cortex and goes to the spine, the pathway through your brain (getting refined) going down to your body
Cerebellum
movements involving timing, coordination, adjustment from trial to trial, people with damage to the cerebellum struggle with the finger-to-nose test
Parkinson’s Disease
muscle rigidity, difficulty initiation movements, can move well enough once started but need a pattern or a “path” to guide them
causes: degeneration of substantia nigra, loss of dopamine needed to run basal ganglia
Parkinson’s Disease treatments
L-Dopa is a precursor to dopamine that crossed the blood-brain barrier (dopamine itself won’t cross)
helps for a time, but tolerance develops and side effects are challenging
Parkinson’s Prevention
stimulant drugs are thought to both prevent Parkinson’s onset and slow its progression
Huntington’s Disease
A dominant gene on chromosome 4 produces a mutant form of a protein called “huntingtin”
the build-up of this protein ultimately destroys the structures of the basal ganglia
severs movement disorders emerge, ultimately fatal, no cure
