Ch. 9 Muscle and Muscle Tissue pt.2 Flashcards
Skeletal Muscle must be stimulated by a ____ ending in order contract. This is what phase?
Nerve
Phase 1
Skeletal muscle sends the stimulus to contract along the ____ as an electrical current (action potential). This is phase?
Sarcolemma
Phase 2
Describe the steps of phase one where motor neuron stimulates muscle fiber.
- Action potential arrives at the axon terminal at neruomuscular junction.
- ACh released and binde to receptors on sarolemma
- Ion permealbilty of sarcolemma changes
- Local change in membrane voltage (depolarization occurs
- Local depolarization end plate potienial) ignites AP in sarcolemma
Describe the steps of phase 2
- AP travels across the entire sarcolemme
- AP travels along t tubules
- SR releases Ca2+ and it binds to troponin, myosin binding sites (active sites) on actin exposed.
- Myosin heads bind to actin, contraction begins.
These stimulate muscle cells to contrat found in the brain and spinal cord.
motor neuron
these are long thread like extensions f neurons within the nerves to the muscle cell
motor axons
Axon ending terminal on a single muscle fiber.
neuromuscular junction
Small membranous sacs filled with neurotransmitter (acetylcholine (ACh))
synaptic vesicle
Folded region of sarcolemma under axon terminal which contain ACh receptors
motor end plate
Enzyme that breaks down ACh to prevent overstimulation of muscle fiber.
Acetylcholinestrase
Microscopic space separating axon terminal from muscle fiber.
Synaptic cleft.
All cells are polarized or nonpolarized?
polarized
The resting membrane potential is _____ in muscle fibers.
Negative
Depolarization of the sarcolemma becomes less ____. And it spreads like ripples on a pond less and less negative as each ripple gets larger.
Negative
Restoration of initial polarized state (negative outside, positive outside) (resting membrane potential)
Repolarization
Period where a cell cannot be stimulated again (usually during repolarization)
Refractory period
Principles governing muscle fiber contraction and wile muscle contraction of many fibers is basically the same.
Whole Muscle Contration
Force exerted on an object by muscle contraction.
Muscle Tension
Force exerted on a muscle by the weight of an object.
Load
Muscle does not change in length but tension builds to peak tension.
Isometric contraction
Muscle tension does not change but length does- 2 types are shortens or lengthens.
Isotonic contraction
Concentric and Eccentric
Muscles contract with varying ___ and for different periods of time.
Force
An action potential in the skeletal muscle cell is what triggers muscle cell contraction
Excitation Contraction (E-C) Coupling
What is pulling the actin toward the middle of the sarcomere?
myosin
When myosin sees ATP it does not have to pull on the actin and the ATP lets the myosin ____ from actin.
Release
If you run out of ATP entirely what happens.?
All the muscles die. A few seconds after death is when ATP runs out so where ever you are contracted is how you will say. Rigor mortise.
Axons of motor neurons extend from ___ to ___.
Spinal cord to the muscle
Branching axon terminals form what?
Neuromuscular Junction
One per muscle fiber
Graphic recording of contractile activity.
Myogram
Response of a motor unit to a single action potential.
muscle twitch
E-C coupling, beginning at contraction.
Latent period
From onset of contraction to peak tension.
Period of contraction
Calcium reentry into SR.
Period of relaxation
Adding twitch contractions from rapid stimulation of the muscle.
Wave summation
Rapid stimulation creates a sustained and quivering contraction.
Unfused (incomplete) tetanus
Stimulation is fast enough for all evidence of muscle relaxation to disappear.
Fused (complete) tetanus
To create smooth continuous contractions, number of motor units does not change.
Function
Contractions of whole muscles which can vary in terms of their strength and degree of contraction.
Graded muscle response
Multiple motor unit summation.
Recruitment
Stimulus where contraction is observable.
Threshold stimulation
All muscles motor units recruited.
Maximal Stimulus
Motor units recruited in order from smallest muscle fibers to largest muscle fibers.
Size principle
Relaxed muscles are slightly contracted keeping muscles ready to respond to stimuli, help to stabilized joints, and to maintains posture.
Muscle tone
Muscle shortens.
Concentric
Muscle lengthens.
Eccentric
The consumption of energy by all cells, including those of muscle tissue, to perform work. ATP provides energy for cross bridge movement, only 4-6 seconds worth of ATP in muscle fibers.
Muscle Metabolism
What are the 3 pathways to generate ATP for muscle metabolism?
- ADP and creatine phosphate
- Glycolysis
- Aerobic Respiration
This is coupled reaction of creatine phosphate and ADP with an energy source of CP and no oxygen required.
Direct phosphorylation
This is glycolysis and lactic acid formation with an energy source of glucose and no oxygen required.
Anaerobic pathway
This is aerobic cellular respiration. The energy required is glucose, pyuric acid, free fatty acids from adipose tissue, and amino acids from protein catabolism. Oxygen is required.
Aerobic pathway
Inability of muscles to contract while receiving stimulation.
Muscle Fatigue
Cramps, lack of ATP leads to a continuous contraction.
Contracture
Anaerobic muscle contraction create a backlog of oxygen demand that must be repaid.
Oxygen Debt
Force of muscle contractions affected by what 4 things.
- Number of muscle fibers stimulates
- Relative size of fibers
- Frequency of stimulation
- Degree of muscle stretch
These form the walls of all the body’s hollow organs (except the heart).
Smooth muscle
Smooth muscle has two layers that create a squeezing motion called what?
peristalsis
What are the two layers of smooth muscle called?
- Longitudinal- long axis of the organ
2. Circular- circumference of the organ
Smooth muscle has what instead of neuromuscular junctions.
Varicosities at the nerve endings.
Smooth muscle has what instead of sarcomeres?
Longer thick and thin filaments arranged diagonally that resist tension anchored by dens bodies.
