BIOSC-116 Lecture Notes - Lecture 2: Nicotinic Acetylcholine Receptor, Myofibril, Endoplasmic Reticulum

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azureprairie-dog22

26 Aug 2020

School

Diablo Valley College

Department

Biological Science

Course

BIOSC-116

Professor

Khan

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Document Summary

Action potential gets to axonal terminal causes ca++ to enter the axonal terminal. All the while, the ca++ pump is causing ca++ to be taken back into the terminal cisternae of the sarcoplasmic reticulum. This contraction will continue as long as ca++ and atp are present (i. e. action potentials are coming down the sarcolemma) Once ca++ is removed from the cytoplasm, the troponin-tropomyosin blockade is reestablished and myosin can"t bind to actin so the contraction stops. This is called the sliding filament theory of contraction because the thin filaments slide, they do not change length (i. e. they don"t shorten) But the sarcomeres shorten as the distance between successive z lines decreases, causing the myofibril to shorten and the whole cell to shorten. Moment to moment changes in force production depends on the number of muscle cells activated and the frequency of stimulation. With an increased frequency of stimulation, there is more calcium released into the cytoplasm.

Related Questions

Describe the process of skeletal muscle contraction by assembling the following 10 events in the proper order. Your answer must be written in complete sentences- do not just list the letters or the events- write it out. Begin your description with an action potential traveling down a motor neuron and end with the muscle in it's relaxed state.

A) T and T system undergoes a conformational change, exposing the myosin binding sites on actin

B) myosin heads/cross bridges bind to actin and flex, shortening the sacromere

C) the motor neuron triggers an action potential at the neuromuscular junction

D) calcium ions bind to the T and T system

E) actin filaments are pulled toward the center of the sacromere, shortening the muscle fiber

F) muscle fiber is stimulated at the neuromuscular junction

G) myosin head/cross-bridges bind to actin

H) APs travel down the T-tubules to the sarcoplasmic reticulum

I) in response to an AP, calcium ions are released into the cytosol/space around the myofibrils

J) calcium ions actively transported into the sarcoplasmic reticulum

K) myosin head continues to attach, flex, release, extend, and reattach as long as calcium ions are present

lilacporcupine860

1.If the supply of ATP to a shortening muscle is completelydepleted, what will happen to the cross-bridge cycle? What is thename if the phenomenon that results from complet ATP depletion?

2.Order the following 10 events that summarize musclecontraction. Remember that a muscle contraction begins with thetransmission of a nerve impulse to a muscle fiber

a. the power stroke

b. Opening of ryanodine Ca2+ channels in the sarcoplasmicreticulum

c. Binding of mysosin cross-bridges to actin

d. release of acetylcholine into the neuromuscular junction

e. confromational change in tropomyosin troponin complex

f. binding of ca2+ to troponin

g. binding of atp to myosin cross-brisges

h. depolarization of the muscle fiber

i. hydrolysis of atp bound to myosin cross-bridges

j. action potential propagation along the transverse tubules

pearpig306

12.

Explain what happens to microfilaments within cells treated with cytochalasin D and why existing actin polymers eventually depolymerize. Fill in the blanks in the explanation below using words from the selections below.

Cytochalsin D _______ of monomers at ______ of existing filaments. When the concentration of G-actin in the cytosol is _______ the critical concentration, the loss of monomers at __________ of existing filaments eventually results in their shortening.

** Selections: prevents addition; equal to; plus ends; facilitates loss; above; below; both minus and plus ends; minus ends

18.

What effect does VX, a typical but potent acetylcholinesterase inhibitor, have on muscle function? Fill in the blanks in the explanation below. A word bank of choices follows.

Because the removal of acetylcholine is inhibited, the muscle membrane at the nueromuscular junction will remain _____ for an abnormally long period, causing the muscles to remain in a ______ state. The prolonged ______ in turn would be propagated via the T tubule system to ________ . The result would be prolonged release of calcium, resulting in sarcomere _______ via the effects of calcium on ________.

***Selections: polarized; depolarized; polarization; depolarization; shortening; relaxing; contracted; the sarcoplasmic reticulum; the troponin system; myosin; Z lines

BIOSC-116 Lecture Notes - Lecture 2: Nicotinic Acetylcholine Receptor, Myofibril, Endoplasmic Reticulum

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