Exam 3 review Flashcards
What are the muscles 4 major functional properties?
Contractility, Excitability, Extensibility, Elasticity
What does it mean for a muscle to have “contractility”?
The ability of muscle cells to forcefully shorten
What does it mean for a muscle to have “excitability”?
The ability to respond to a stimulus, which may be delivered from a motor neuron or a hormone
What does it mean for a muscle to have “Extensibility”?
the ability of a muscle to be stretched
What does it mean for a muscle to have “elasticity”?
The ability to return to normal length after a stretch
Where is the EPIMYSIUM in the muscle cell?
dense irregular connective tissue which covers the entire muscle
Where and what is the PERIMYSIUM on a muscle cell?
connective tissue that groups muscle fibers into bundles or fascicles
Where and what is ENDOMYSIUM in muscle cell?
connective tissue that surrounds a muscle cell
* key element that separates single muscle fibers from one another.
How do muscles grow bigger?
Hypertrophy - increase in diameter more proteins in cell (myofibrils sarcomeres and nuclei from satellite cells)
*Connective tissue and sarcoplasmic hypertrophy
What is Titan?
Protein that gives muscles ability to stretch and recoil
Z disk to M line
What are the 3 proteins that make up actin?
Globular
Actin
Troponin
Where is Ca2+ stored in muscle fiber?
Sarcoplasmic reticulum
What are 3 important properties of myosin heads?
- Bind to actin
- Can bend and straighten during contraction
- Heads are ATPase which break down ATP
Neurotransmitters can bind to what and cause what?
Ligand gated ion channels and inhibit or excite an action potential
From muscle to myofilament, describe the components large to small
Muscle -> Fascicles ->Muscle fiber/cell -> myofibrils -> myofilaments
Myofibril is numerous sarcomeres
What are the 4 phases of contraction and relaxation?
- *Excitation** - Nerve action potentials lead to muscle action potentials (presynaptic terminal to post)
- *Excitation-contraction coupling** - Action potentials in sarcolemma (release of Ca2+ that binds to troponin) that lead to activation of myofilaments
- *Contraction -** Myosin attaches to action and power stroke (contraction)
- *Relaxation -** Muscle fiber relaxes and returns to original length
What is a synapse?
A point where a nerve fiber meets its target cell (could be another neuron or effector such as a gland or skeletal muscle)
What are the 2 major gated ion channels in skeletal muscles?
Ligand and voltage gated channels
When does depolarization start?
When threshold is met, then Na2+ gated channels open (more postive)
When does repolarization start?
Between 30-40mv, in this range voltage gated Ca2+ close and K+ open (more negative)
What does acetylcholinesterase do?
Its an enzyme attached to post synaptic membrane, removes ACH from synaptic cleft by breaking it down into acetic acid and choline
(Choline goes back into presynaptic terminal with Ca2+ to be recycled and acetic acid diffuses away)
What is spastic paralysis?
Aka - Tetanus / lockjaw
A state of continual contraction
when something binds with acetylcholinesterase and prevents it from degrading ACH
What is flaccid paralysis?
Botox
- State in which muscles cannot contract
- Blocks release of ACH
What parts of the sarcomere move and get smaller during a muscle contraction?
Z disks move inward, I bands and H zone get smaller
What are 3 ATP dependent events required for muscle relaxation?
- Na+/K+ pump actively moves ions to restore RMP
- Detach myosin heads from action
- Return Ca2+ to sarcoplasmic reticulum
What are the 3 phases of myogram?
Lag
Contraction
Relaxation
What is the lag or latent phase of a muscle twitch?
The time between the activation of a motor neuron until the muscle contraction occurs
1-2msec
What is the contraction phase of a muscle twitch?
Cross bridges form, sarcomeres shorten and muscle contracts
20msec
What is the Relaxation phase of a muscle twitch?
Myosin releases from action and the tension decreases. Ca2+ is transported back into sarcoplasmic reticulum
This phase is the longest
What are 2 major types of muscle contraction?
ISOTONIC
ISOMETRIC