MSS Week 2

Question 1

What are the five functions of skeletal muscle?

Please Capture Marshall Mathers not MGK

Answer 1

1) Movement
2) Maintaining the body’s posture
3) Maintaining body temperature
4) Protection and support of soft tissue
5) Creates values at the openings of the body

Question 2

Explain the neural events that control skeletal muscle contraction?

Neuromuscular junction
Motor end plate

Answer 2

Neuromuscular junction: site where there is communication between the motor neuron and muscle fibre

Motor end plate: postsynaptic membrane of the neuromuscular junction, to facilitate communication

Question 3

Describe the process of excitation-contraction coupling

Answer 3

Definition: The simulation of the motor neuron leads to a contraction of the muscle

1) Acetylcholine is released from the axon terminal and binds to receptors at the motor end plate
2) Entry of sodium through channels initiates an action potential that travels down the T-tubule
3) Dihydropyridine (DHP) receptors on the T-tubule activate Ryanodine receptors (RYR) on the sarcoplasmic reticulum to release calcium

Question 4

Describe the process of cross bridge cycling

Answer 4

4) Calcium binds to troponin, calcium-troponin complex occurs, tropomyosin is pulled away from the actin sites for the myosin head to bind, cross bridge cycling occurs between myosin and actin, a muscle contraction will occur from this process
5) The myosin head uses the hydrolysis of ATP to be cocked ADP and Pi will leave the myosin for it to perform the power stroke, which pulls the actin filaments toward the M line (center of sarcomere)
6) Once the action potential ends, the ATP detaches the myosin head from the actin filaments, calcium is returned to the sarcoplasmic reticulum through the enzyme (SERCA), tropomyosin will block the actin binding sites, troponin-tropomyosin complex occurs

Question 5

What are the two enzymes that are involved in Skeletal Relaxation?

Answer 5

Acetylcholinesterase: degrades and recycle Ach

SERCA: returns calcium into the sarcoplasmic reticulum

Question 6

Name the two types of Smooth muscle and describe them

Answer 6

Multi-unit smooth muscle:
All behave independently (each cell contracts and relaxes on it’s own)
Has few gap junctions ( no need to electrically couple the cells through a gap junction)
Example: vascular smooth muscle

Single unit smooth muscle: 
Behave as one unit 
Large amount of gap junctions 
All the smooth muscle cells will depolarize
Example: GI Tract

Question 7

Describe the process of smooth muscle contraction in six steps

Answer 7

1. Calcium ions enter the cystol through calcium channels
2. Calcium binds and activates calmodulin
3. Activates the myosin light chain kinase enzymes by phosphorylating it
4. Use the hydrolysis of ATP, becomes activated with phosphate added
5. Cross bridge is formed
6. Ends when the phosphate is removed

Question 8

What is the function for each part of the skeletal muscle fibre?

a) Sarcolemma
b) Transverse (T) Tubule system
c) Triad

Answer 8

a) causes depolarization to communicate
b) transmits the depolarization from the the surface to the center of the fibre
c) translates the action potential from the plasma mmbrane to the sarcoplasmic reticulum

Question 9

Describe the structure of Myosin

Answer 9

Two heads and long tail

Question 10

Name the function of each

1) Titin
2) Dystrophin
3) Nebulin

Answer 10

1) anchors and stabilizes myosin
2) protects the myofiber from disruption during the contraction
3) anchors and stabilizes actin

Question 11

What is the function for each part of the skeletal muscle fibre?

a) Sarcolemma
b) Transverse (T) Tubule system
c) Triad

Answer 11

a) causes depolarization to communicate
b) transmits the depolarization from the the surface to the center of the fibre
c) translates the action potential from the plasma mmbrane to the sarcoplasmic reticulum

Question 12

Describe the structure of Myosin

Answer 12

Two heads and long tail

Question 13

Name the three proteins of Troponin and what does each one bind to?

I Take Care

Answer 13

Troponin I (binds to actin) 
Troponin T (binds to tropomyosin) 
Troponin C (binds to Calcium)

Question 14

Explain the mechanism of Rigor Mortis

Answer 14

Lack of ATP, which leads to cross-bridge cycling without detachment

Question 15

What are the three things that happens in the sarcomere during muscle contraction

Answer 15

A) H zones and I bands get shorter
B) The zones of overlap increase
C) Width of A band stays constant

Question 16

Describe the function of the following

a) Z - Line
b) M - Line
c) I - Band
d) A - Band
e) H - Zone

Answer 16

a) Z - line: anchor for thin filaments and boundary between sarcomeres
b) M - Line: Center of the sarcomere, anchoring the thick filaments
c) I band: Thin filaments
d) A band: Thick Filaments
e) H-Zone: area at the center of sacromere where the thick and thin filaments do not overlap