Week 9

Question 1

What are the 4 types of primary tissue in the body?

Answer 1

1) connective
2) epithelial
3) muscle
4) nervous

Question 2

What are the 3 types of muscle tissue?

Answer 2

1) Skeletal
2) Smooth
3) Cardiac

Question 3

What does the muscle do when it contracts (one word)?

Answer 3

It shortens

Question 4

What two proteins are needed for muscle contraction?

Answer 4

Actin and myosin

Question 5

What are some functions of the muscular system?

Answer 5

1) movement
2) maintain posture
3) protect internal organs
4) generate heat

Question 6

Each skeletal muscle has 3 layers of connective tissue. What are they and where are they in relation to each other?

Answer 6

1) epimysium - outer
2) perimysium - inside the epimysium
3) endomysium - inside the permiysium

Question 7

What is the job of the epimysium connective layer?

Answer 7

It covers the whole muscle. It separates muscle from other muscle and organs.

Question 8

What is the job of perimysium connective tissue?

Answer 8

It separates muscle into fascicles.
Fascicle = bundle of muscle fibres.

Question 9

What is the job of endomysium? What does it contain?

Answer 9

It surrounds individual muscle fibres (= muscle cells, same thing as muscle fibres).
It contains ECF (extracellular fluid) and nutrients to support muscle fibres.

Question 10

Are skeletal muscle fibres / cells multi-nucleated or uni-nucleated?

Answer 10

Multi-nucleated

Question 11

What does multi-nucleated mean?

Answer 11

Has several nuclei

Question 12

Why are muscle fibres / cells multi-nucleated?

Answer 12

It permits large amounts of protein to be produced

Question 13

*Study diagram on slide 8

Answer 13

Did you?

Question 14

What does the pre-fix “sarca” mean?

Answer 14

Flesh

Question 15

What is the sarcolemma?

Answer 15

Plasma membrane of skeletal muscle fibres

Question 16

What is the sarcoplasm?

Answer 16

Cytoplasm of skeletal muscle fibres

Question 17

What is the sarcoplasmic reticulum (SR)?

Answer 17

Smooth endoplasmic reticulum of the skeletal muscle fibres

Question 18

What is the sarcomere and what is its job?

Answer 18

It is the functional unit of muscle fibres, and it is the part that contracts / shortens

Question 19

What is a neuromuscular junction? (NMJ).

Answer 19

It is the connection between a neuron (axon terminal) and muscle fibre.

Question 20

Every skeletal muscle is innervated by a motor neuron at the NMJ. Excitation signals (AP) from the neuron are the only way to functionally activate the fibre to contract. Is this true?

Answer 20

Yes.

Question 21

What happens at the NMJ, which is the site for the transmission of action potential from nerve to the muscle? (6 steps)

Answer 21

1. Actions potential (AP) arrives at the axon terminal.
2. Calcium channels open and calcium enters the axon terminal.
3. Acetylcholine (ACH) is released into the synapse (=space between two cells).
4. Acetylcholine binds to ligand-gated receptors on muscle fibres.
5. Ligand gates open and sodium rushes into the muscle fibre.
6. Action potential is generated along the sarcolemma (= plasma membrane) of the muscle fibre.

Question 22

What happens after the action potential has reached the muscle and makes it contract? (5 steps)

Answer 22

1. AP is carried along the t-tubules of the sarcolemma.
2. Calcium released from the sarcoplasmic reticulum into the sarcoplasm.
3. Calcium binds to actin at the troponin site.
4. Troponin moves tropomyosin out of the way.
5. Myosin and actin connect, creating a cross-bridge, which triggers a contraction.

Question 23

What happens as a muscle relaxes after contraction? (3 steps)

Answer 23

1. AP stops
2. Calcium goes back into the sarcoplasmic reticulum
3. Actin and myosin can’t attach because tropomyosin is in the way.