Lecture 17 - Skeletal Muscle

Question 1

How do we generate the force to produce movement?

Answer 1

Skeletal muscle

Question 2

What are the properties of muscle tissue?

Answer 2

Excitability, conducts electrical impulses, contractibility, extensibility, elasticity

Question 3

What is excitability?

Answer 3

The property of muscle being sensitive or responsive to chemical, electrical, or mechanical stimuli

Question 4

What is contractibility?

Answer 4

The ability of muscle to contract and develop tension or internal force against resistance when stimulated

Question 5

What is extensibility?

Answer 5

The ability of muscle to be stretched back to its original length following contraction

Question 6

What is elasticity?

Answer 6

The ability of muscle to return to it’s original length following stretching

Question 7

What are agonist muscles?

Answer 7

Muscles that cause joint motion through a specified plane of motion when contracting concentrically

Question 8

What are agonist muscles also known as?

Answer 8

Primary/prime movers

Question 9

What are antagonist muscles?

Answer 9

Muscles located on the opposite side of a joint from an agonist that contract concentrically to perform the opposite joint motion of agonist muscles

Question 10

What are agonist muscles also known as?

Answer 10

Contralateral muscles

Question 11

What are synergist muscles?

Answer 11

Muscles that assist in action of agonists that assist in refined movement and reduce undesired motions

Question 12

What are synergist muscles also known as?

Answer 12

Guiding muscles

Question 13

What is the epimysium?

Answer 13

Connective tissue surrounding the entire muscle

Question 14

What is the perimysium?

Answer 14

Connective tissue surrounding the bundles of muscle fibers (fascicles)

Question 15

What is the endomysium?

Answer 15

Connective tissue surrounding individual muscle fibers

Question 16

What is the sarcolemma?

Answer 16

The muscle cell membrane

Question 17

What are myofibrils?

Answer 17

Threadlike strands within muscle fibers made up of actin and myosin

Question 18

What is actin?

Answer 18

Thin filament made up of troponin and tropomyosin

Question 19

What is myosin?

Answer 19

Thick filament

Question 20

What is a sarcomere?

Answer 20

The smallest contractile unit of skeletal muscle

Question 21

What is a motor unit?

Answer 21

A single motor neuron and muscle fibers it innervates

Question 22

Why does the CNS alternate the motor units it recruits?

Answer 22

To reduce fatigue and distribute work load

Question 23

What are the types of muscle contractions?

Answer 23

Isometric and isotonic

Question 24

What is an isometric contraction?

Answer 24

A contraction where the muscle exerts force without changing length

Question 25

What is an isotonic contraction?

Answer 25

A contraction where the muscle exerts force by changing length

Question 26

What are the types of isotonic contraction?

Answer 26

Concentric and eccentric

Question 27

What is a concentric contraction?

Answer 27

A contraction where the muscle shortens during force production

Question 28

What is an eccentric contraction?

Answer 28

A contraction where the muscle length increases during force production

Question 29

How does neural excitation move to muscle force?

Answer 29

Muscle activation dynamics (excitation contraction coupling) and muscle contraction dynamics

Question 30

What is force output dependent on?

Answer 30

Muscle length, velocity, and activation of the muscle unit

Question 31

Who is A.V. Hill?

Answer 31

Physiologist who studies the chemical and mechanical properties of muscle

Question 32

What did A.V Hill conclude in his first experiment?

Answer 32

Multiple motor units combine to produce a usable force that can be increased by the nervous system by recruiting more motor units or increasing the frequency of action potentials

Question 33

What did A.V. Hill observe about muscle mechanics in his first experiment?

Answer 33

That contraction begins with the twitch of a muscle fiber

Question 34

What is a twitch?

Answer 34

A force produced by an isometric muscle response to an action potential in one or more motor units

Question 35

What is the summation of twitches?

Answer 35

When the muscle is not allowed to relax between action potentials to the point of tetanus?

Question 36

When does tetanus occur in humans?

Answer 36

50-60 Hz

Question 37

What was A.V. Hill’s second experiment?

Answer 37

Force Length

Question 38

How did A.V. Hill observe force length?

Answer 38

By measuring passive and active force

Question 39

What did A.V. Hill observe about active length tension in his second experiment?

Answer 39

Active length tension relationships are directly related to sarcomere length

Question 40

What happens when a sarcomere is too long?

Answer 40

It is unable to crossbridge

Question 41

What happens when a sarcomere is too short?

Answer 41

It is unable to contract further because thin filaments hit each other

Question 42

What did A.V. Hill observe about passive length tension in his second experiment?

Answer 42

Passive length tension is like a spring (non linear) due to connective tissue

Question 43

What did A.V. Hill observe about muscles during unloading vs loading in his second experiment.

Answer 43

Hyesteresis, different length tension properties apply when loading and unloading tissue

Question 44

Can active and passive tension be combined to produce force?

Answer 44

Yes

Question 45

What was A.V Hill’s third experiment?

Answer 45

Force velocity relationship