muscles exam 3

Question 1

What are the three types of muscle?

Answer 1

Skeletal Muscle, Smooth Muscle, Cardiac Muscle

Question 2

What is the sarcolemma?

Answer 2

Muscle cell membrane

Question 3

What is the function of the sarcoplasmic reticulum (SR)?

Answer 3

Stores calcium in the muscle cell

Question 4

What is the role of T-Tubules?

Answer 4

Carry action potential from sarcolemma into the muscle cell

Question 5

Define a motor unit.

Answer 5

A motor nerve and all the muscle fibers it innervates

Question 6

What initiates muscle contraction at the neuromuscular junction?

Answer 6

Release of ACh (acetylcholine) into the synaptic cleft

Question 7

Fill in the blank: The sliding filament theory involves the interaction of _______ and _______.

Answer 7

actin, myosin

Question 8

What are the two main types of myofilaments?

Answer 8

Thin (actin) and thick (myosin)

Question 9

What is a sarcomere?

Answer 9

The ‘contractile unit’ of muscle, defined from Z-line to Z-line

Question 10

What is the primary characteristic of Type I muscle fibers?

Answer 10

Slow oxidative, high in myoglobin, mitochondria, and capillaries

Question 11

What is the primary characteristic of Type IIa muscle fibers?

Answer 11

Fast oxidative-glycolytic, intermediate in speed and efficiency

Question 12

What is the primary characteristic of Type IIx muscle fibers?

Answer 12

Fast glycolytic, very strong but inefficient

Question 13

True or False: Muscle fiber type can change.

Answer 13

True

Question 14

What is the difference between concentric and eccentric muscle actions?

Answer 14

Concentric is shortening; eccentric is lengthening

Question 15

What influences force development in muscles?

Answer 15

*Size of muscle (hypertrophy) *Number of motor units *Optimal muscle length *Angle of joint *Speed of action

Question 16

What is the power stroke in muscle contraction?

Answer 16

The process where myosin pulls actin inward

Question 17

What is the significance of calcium in muscle contraction?

Answer 17

Calcium binds to troponin, causing tropomyosin to uncover active binding sites

Question 18

What is the role of ATP in muscle contraction?

Answer 18

Necessary for myosin cycling and muscle relaxation

Question 19

What does the term ‘excitation-contraction coupling’ refer to?

Answer 19

How the nervous system communicates with the muscle to contract

Question 20

What is the sliding filament model of contraction?

Answer 20

A model explaining how actin and myosin filaments slide past each other to cause muscle contraction

Question 21

What is the role of troponin in muscle contraction?

Answer 21

Binds calcium and changes shape to uncover binding sites on actin

Question 22

Fill in the blank: Myosin ATP-ase is critical for muscle fiber speed differences as it splits a _______ off of ATP for energy.

Answer 22

phosphate

Question 23

What factors are considered in determining athletic performance?

Answer 23

*Training effectiveness *Sport intelligence *Body type/body fat *Desire/competitiveness

Question 24

First 3 steps of muscle contraction

Answer 24

An action potential causes ACh to be released into the synaptic cleft

ACh binds to receptors in the motor end plate initiating an action potential along the sarcolemma and T-tubule membranes

Calcium is released from SR into the sarcoplasm

Question 25

Steps 4-6 of muscle contraction

Answer 25

Calcium ions bind to troponin causing tropomyosin to uncover active binding sites Myosin heads then bind to actin and form crossbridges (Crossbridge cycling – details next!) In the presence of ATP, myosin cycles through attachment, pivot, detach and return -ATP is also necessary for relaxation of the muscle fibe

Question 26

4 steps of cross-bridge cycling

Answer 26

The four steps to cross-bridge cycling (5 pts) Step 1: Crossbridge Formation Ca++ binds to troponin – this ‘pulls’ the tropomyosin strand off of actin’s “active binding sites” Myosin binds to actin at ‘active binding site’ Ca++ and Energy (ATP) are required Step 2: the Power Stroke myosin head pivots towards the center of the sarcomere This creates movement as filaments slide past each other (actin ‘slides in’, powered by myosin’s movement’) Step 3: Crossbridge Detachment Myosin head detaches from actin (Requires energy (ATP) (note on rigor mortis)) Step 4: Re-Activation of Myosin Head Myosin head is re-energized from its new ATP molecule and ‘starts again Note: Muscle contraction/cross-bridge cycle continues as long as there is Ca++ present