Physiology Lecture 5

Question 1

general movement of AP to muscle cell

Answer 1

L5S4
-Presynaptic nerve cell synapses with a muscle cell
-ACh is released and binds with receptors on motor end plate of muscle cell
-AP propogates down t-tubule
-Binds to a receptor in the tubule that induces the release of calcium from the sarcoplasmic reticulum
-Calcium seeks binding sites on thin filaments
Crossbridges can now bind to the thin filaments

Question 2

What reabsorbs calcium so crossbridges can relax?

Answer 2

Sarcoplasmic reticulum

Question 3

What is a motor unit?

Answer 3

Single alpha motor neuron and all the muscle fibers it innervates

They fire all at once

Question 4

Is each muscle fiber within a motor unit the same fiber type?

Answer 4

Yes

Question 5

Recruiting more motor units results in what?

Answer 5

Greater number of crossbridges

Question 6

Motor units are generally recruited in order from _____ to ______.

Answer 6

Smallest to largest

This minimizes the amount of fatigue

Question 7

Fatigue can be caused by a decrease in production of what?

Answer 7

ATP

Question 8

Difference between muscle tension and load?

Answer 8

Muscle tension is the force exerted on an object

Load is the force exerted on the muscle by the object

Question 9

When muscle tension is greater we see what type of contraction?

Answer 9

Isotonic concentric

Question 10

When the load is greater than the muscle tension we see what type of contraction?

Answer 10

Isotonic eccentric

Question 11

What does the force velocity curve show?

Answer 11

As force needed increases, velocity goes down.

Question 12

When velocity is 0 we have what type of contraction?

Answer 12

Isometric

Question 13

Having a negative velocity is what?

Answer 13

Eccentric

Question 14

What is a tetanic contraction?

Answer 14

Muscle is unable to relax and stays maximally contracted

Question 15

What is summation?

Answer 15

increase in muscle tension from successive action potentials occurring during the phase of mechanical activity

Question 16

When do we have the most force production?

Answer 16

When out muscles are halfway because this is when the maximum amount of crossbringing is occuring.

Question 17

What is active insufficiency?

Example

Answer 17

When a multi joint muscle reaches a length so short it can no longer generate effective force.

Making a fist with the wrist extended is stronger than with the wrist flexed.

Question 18

What is passive insufficiency?

Example

Answer 18

Occurs when a multi joint muscle is passively elongated such that it cannot allow full ROM at both joints simultaneously

difficult to reach the toes with the knee extended as compared to that with the knee flexed

Question 19

What is muscle strength influenced by?

Answer 19

• Number of MU/fibers recruited
• Frequency of fiber stimlation
• Initial length of fiber at rest

Question 20

What is muscle pennation?

Answer 20

Describes the orientation of muscle fibers relatively to the load axis of the muscle

Question 21

With pennation, do we get more or less fibers in the same amount of area?

Answer 21

More

Question 22

The greater the angle of pennation, the more ________ in the same area which results in ___________.

Answer 22

muscle (crossbridges)

more force production

Question 23

Why would we want smaller pennation angles in some instances?

Answer 23

Smaller angle of pennation means more velocity but less force

Question 24

Muscle that generate force have _______ cells while muscles that generate velocity have _______ cells.

Answer 24

shorter, longer