Muscle Physiology

Question 1

Skeletal Muscle:
- Appearance
- What part of nervous system
- Function

Answer 1

• Appearance: Long and striated due to presence of actin + myosin bands
• What part of nervous system: Somatic
• Function: Provide motor to body via sliding filament mechanism

Question 2

What is required for muscle contractoin?

Answer 2

ATP (energy) + calcium

Question 3

What/where is the skeletal neurotransmitter? What effect does it have on the muscles

Answer 3

Acetylcholine (Ach), at ends of motor neurons, ceases muscle activity

Question 4

What is the difference between origin and insertion of muscles?

Answer 4

1. Origin: less moveable end of muscle/tendon attached to bone
2. Insertion: more moveable end of muscle, usually attached to bone via tendons

• Skeletal muscles have both

Question 5

What are skeletal muscles attached to?

Answer 5

Skeletal system (bone) by tendons (connective tissue)

Question 6

Smooth muscle is AKA…

Answer 6

Visceral muscle

Question 7

Where is smooth muscle found?

Answer 7

In the walls of all hollow organs

Question 8

How are electrical impulses transmitted in smooth muscles? What are the neuro transmitters + their functions?

Answer 8

Through interstitial fluid as there are NO neuromuscular junctions
Neurotransmitter:
1. Acetylcholine (Ach): causes contractions
2. Norepinephrine: inhibits contractions

Question 9

When does muscle relaxation occur in smooth muscle?

Answer 9

When calcium is moved OUT

Question 10

What is the appearance of smooth muscle fibers?

Answer 10

Spindle shaped with a single nucleus

Question 11

What muscle(s) are involuntary?

Answer 11

1. Smooth muscle
2. Cardiac muscle

Question 12

What muscle(s) are voluntary?

Answer 12

1. Skeletal muscle

Question 13

What are the 3 types of muscles

Answer 13

1. Skeletal Muscle
2. Smooth/Visceral Muscle
3. Cardiac Muscle

Question 14

What is the function of the cardiac muscles

Answer 14

To pump blood in the circulatory system

Question 15

What is the appearance + location of cardiac muscles?

Answer 15

Branching and striated, located in wall of heart

Question 16

Define: Sarcomere

Answer 16

Contractile unit of muscle fiber

Question 17

Define: Myofibril

Answer 17

Muscle fiber

Question 18

Define: Sarcoplasmic reticulum

Answer 18

Endoplasmic reticulum that is needed for muscle contraction

Question 19

Define: Z-line

Answer 19

Protein bands where actin filaments attach in a striated muscle fiber and mark the boundaries of adjoining contractile units

Question 20

Define: Sarcolemma

Answer 20

Thin plasma cell membrane of a muscle cell

Question 21

What is the process of muscle contraction? (5 steps)

Answer 21

1. Action potentials (nerve impulses) trigger calcium release
   
   • Calicum is stored in the sarcoplasmic reticulum when the muscle is at rest
2. The calcium then binds to troponin on the thin filaments, which turns on actin and myosin interaction.
   
   • This results in contraction of the sarcomere. After the contraction, calcium is pumped back into the sarcoplasmic reticulum via Calcium ATPase
3. When the action potential reaches an axon terminal, acetylcholine is released from the vesicles,
   which opens transmembrane channels and allows sodium to diffuse in.
4. After the action potential, the latent period occurs when acetylcholinesterase breaks down the acetylcholine at the neuromuscular junction.
5. The sodium channels then close, and resting potential is restored by outflow of potassium.

Question 22

How is action potential created?

Answer 22

When sodium ions rush in, the action
potential is created in the muscle fiber

An influx of sodium ions, decreases the resting potential at the end plate

Question 23

What is the neuromuscular junction

Answer 23

The junction between the motor neuron terminal and the muscle fiber (a kind of synapse)