Excitation of Skeletal Muscle Flashcards
Ligand-gated channels will close when acetylcholine detaches by ____.
(or we can wait for it to diffuse out of the cleft but this would take too long)
Acetylcholinesterase
Axon only touches in one spot, regardless of fiber length. This spot is called?
Motor end plate
This drug poisons the acetylcholinesterase (keeping the acetylcholine binded at the gates, leaving the muscle contracted). Giving a small dose helps get over the threshold by allowing sodium in for a little longer?
*High doses will cause the muscles to contract and never relax - diaphragm contracts = death by asphyxiation
(Sarin gas, VX, mustard gas)
Neostigmine
- Presynaptic =
* Postsynaptic = ? (in brain-dendrite)
- Axon terminus
- Muscle fiber
Neurotransmitter that is dumped onto something = Acetylcholine
- MEPP is an example
- Only significant at neuromuscular junction
Excitatory Post-Synaptic Potential
Small depolarization (about half a mV) this is caused by one acetylcholine vesicle. Helps you get closer to threshold. Need to dump a lot of vesicles at once, usually need to have thousands of acetylcholines to fuse in order to get over threshold (once over threshold voltage gated sodium channel opens and get big spike).
- One vesicle
- Small depolarization of the post-synaptic terminal
Miniature End Plate Potential (MEPP)
Works as a paralytic (lasts about a month). Works by preventing acetylcholine from being released from axon terminus.
(decreases end plate release of acetylcholine)
Botulinum (Botox)
T-tubule:
- Voltage gated calcium channel
- Calcium controlled calcium release channel on sarcoplasmic reticulum
DHP receptor
Ryanodine receptor
Protein that holds the calcium (locks it away) so it is not increasing the
calcium concentration. Makes it easier for us to pump it back into
sarcoplasmic reticulum and we will not have to worry about fluctuating calcium concentrations within the T-tubule
Calsequestrin
Autoimmune disease that attacks the acetylcholine receptors - get progressive weakness as day goes on because they are using up acetylcholine receptors.
Myasthenia Gravis
Proprioception: Want to know how much force our muscles are generating and whether or not we are contracting (getting longer or shorter)
*2 ways of knowing what our muscles are doing
Detects changes in muscle length (shortening or lengthening). Run parallel to muscle fibers.
Contraction = slack
Relaxation = tightening
Intrafusal fibers
Proprioception: Want to know how much force our muscles are generating and whether or not we are contracting (getting longer or shorter)
*2 ways of knowing what our muscles are doing
Measuring total force generated. Located on tendon and detects force placed on tendon. Little mechanical gate to detect how much this tendon has stretched, basically measuring how much force is on the tendon. Firing rate will change as force changes, tells brain. Every skeletal muscle will have this.
Just cares about total force from entire muscle.
Golgi tendon organ
Job is to pull in the slack or let go of the slack. (does not know anything about muscle fiber, just whether its getting shorter or longer). Takes job off brain so we can daydream and walk. Fibers sense they are getting larger (walking), not generating enough force, tells the interneurons in lumbar enlargement that control this (they recruit another motor unit) second to second motor recruitment.
Intrafusal fibers
Corticospinal Tract (major motor pathways)
White matter are?
Gray matter are?
- axons and myelin
- cell bodies and dendrites
Fine touch and kinesthesis?
Dorsal column medial lemniscus (DCML)
