Flashcards in Muscle Physiology Deck (55):
List some functions of muscles.
• Blood and lymph circulation
• Generation of body heat
What are 4 specific properties of muscles?
Which type of muscle is present in 40% of the body?
Which type of muscle is present in 10% of the body?
Smooth and cardiac muscles
Describe skeletal muscle.
Striated, voluntary, found in trunk, extremities, head and neck, fast contraction, peripheral nuclei
Describe smooth muscle.
No striations, involuntary, found in viscera and blood vessels, slow contraction, central nucleus
Describe cardiac muscles.
Striated, involuntary, fast contraction, central nuclei
What is the result of contraction of skeletal muscles?
Movement of the body
Sheath of connective tissue surrounding the muscle
A small bundle or cluster of muscle fibers (cells)
Connective tissue extensions from the epimysium that surround each fascicle
Connective tissue extensions from the
perimysium that surround the muscle fibers
and are attached to the sarcolemma
Thin cell membrane enclosing skeletal muscle fiber
Elongated, the contractile unit. Pull transmitted by endomysium, perimysium and epimysium to tendon or
aponeurosis that is attached to bone
What are the 2 types of muscle fibers?
1. Red fibers, type 1 or slow twitch
2. White fibers, type 2 or fast twitch
Which type of muscle fatigues easily, and is larger in diameter?
What is each myofibril composed of?
Repeating sarcomeres in a linear sequence
What is the basic contractile unit of striated muscle fibers?
Where are sarcomeres found?
Between Z lines or Z disks
What do sarcomeres contain?
Protein myofilaments actin and myosin
What are responsible for actual muscle contraction?
Actin (thin) and myosin (thick)
T/F: Actin and myosin filaments partially interdigitate.
Light band, Isotropic to polarized light
Dark band, Anisotropic to polarized light
What are the ends of actin filaments attached to?
Z disk or Z line (forms periphery of sarcomere)
Light zone in the center made of thick filaments
Found inside the H Zone, forms middle of sarcomere, made of thick filaments and accessory proteins
Why is the sarcoplasmic reticulum important for muscle contraction?
Regulates calcium storage, release and re-uptake
What is an organelle in the muscle fiber present in large numbers and provides energy?
Where are T-tubules arranged?
Transverse to myofibril as invaginations of the sarcolemma
T/F: T-tubules allow the PM of the muscle fiber to carry the depolarization of the action potential to the interior of the fiber.
T/F: Membrane potential exists across the membrane of virtually all cells.
What are membrane potentials generated by?
Ionic differences between ICF and ECF
What do muscle and nerve cells generate at their membranes?
Rapidly changing electrochemical impulses
What do impulses transmit?
Signals along the nerve or muscle membranes
What type of muscle cells are controlled by a motor neuron?
What are the different effects of membrane potential on diffusion of ions?
Net diffusion rate, nerst potential, pressure difference
What is Nerst potential?
The diffusion potential level across a membrane that exactly opposes the net diffusion of a particular ion through the membrane
T/F: If a higher pressure is applied in one side of the membrane, more molecules will diffuse to the other side.
Give an example of pressure difference.
Which ion is present in larger amounts in the cytosol?
What is the resting membrane potential of nerve fibers when not transmitting nerve signals?
What are factors that determine the resting potential?
1. Diffusion of potassium thru nerve cell membrane
2. Diffusion of sodium thru nerve cell membrane
3. Contribution of Na-K pump
In the "leak channels", which way do sodium and potassium want to go?
More potassium going out than sodium going in
What is the most important contributor for resting potential?
How are nerve signals transmitted by?
What are action potentials?
Rapid changes in the membrane potential that spread rapidly along the nerve fiber membrane
What does each action potential begin with?
Sudden change from the normal resting negative membrane potential, to a positive potential
What is the resting stage?
• Is the resting membrane potential
• Moment before AP begins
• Membrane is said to be “polarized” b/c of the negative MP
A threshold for the initiation of the action potential is achieved, the membrane suddenly becomes permeable to sodium ions, Membrane Potential rising in the positive direction is called DEPOLARIZATION
How does sodium influx occur during depolarization state?
Voltage-gated sodium channels
After the membrane becomes highly permeable to Na+, Na channels begin to close. Voltage-gated K channels open to a greater degree than normal. Rapid diffusion of K+ out of the cell. Re-establishment of normal negative resting potential is repolarization.
Where does the action potential travel?
In all directions away from the stimulus until the membrane has become depolarized.
T/F: A new action potential cannot occur in an excitable fiber as long as the membrane is still depolarized from the preceding AP.