Muscle function and Structure

Question 1

What are the 3 types of muscle?

Answer 1

Skeletal, Cardiac and Smooth

Question 2

Skeletal muscle connects to bone via what?

Answer 2

Tendons

Question 3

Describe the structure of a skeletal muscle cell

Answer 3

Long, cylindrical, multinucleated cells

Question 4

What is a muscle cell called?

Answer 4

Myofibril

Question 5

What is a group of myofibril surrounded by sarcolemma called?

Answer 5

Muscle fibre

Question 6

What is a fascicle made up of?

Answer 6

Muscle fibers

Question 7

Name the three connective tissues in muscle and what they surround

Answer 7

Endomysium - Muscle fibers

Perimysium - Fascicles

Epimysium - Muscle fibers
outer layer of muscle making up tendons

Question 8

What single motor neuron innervates each muscle?

Answer 8

Somatic Motor Neuron

Question 9

What is the role of T-tubules in the sarcolemma of a muscle fibre?

Answer 9

To quickly spread an AP through muscle fibre

Question 10

Myofibrils contain thick and thin filaments arranged into what?

Answer 10

Sarcomeres

Question 11

Thin filaments mostly composed of?

Answer 11

Actin

Question 12

Thick Filaments are mostly composed of?

Answer 12

Myosin

Question 13

Myosin contains two binding sites one for actin and ____?

Answer 13

ATP

Question 14

Thin filament is composed of actin, ____ and ____?

Answer 14

troponin, tropomyosin

Question 15

Actin contains the binding site for _____?

Answer 15

Myosin

Question 16

What does tropomyosin block?

Answer 16

Tropomyosin blocks the binding site for myosin

Question 17

What is tropomyosin held in place by?

Answer 17

Troponin

Question 18

A motor unit is a ____ + _____

Answer 18

motor neuron + all the muscle fibers it innervates

Question 19

What are the three phases of Muscle Contraction?

Answer 19

1. Neuromuscular Junction (AP travels along motor neuron and moves across synapse)
2. Excitation-Contraction Coupling (AP travels along sarcolemma, causing release of calcium)

3.Cross-Bridge Cycling (Myosin head binds with actin allowing for contraction)

Question 20

Explain the processes that occur at a neuromuscular junction

Answer 20

1. An action potential travels along a motor neuron to the axon terminal
2. The change in membrane potential causes voltage-gated calcium channels to open
3. Calcium enters the axon terminal
4. Calcium signals neurotransmitter (acetylcholine) filled vesicles to move towards the membrane
5. Vesicles merge with membrane and release neurotransmitter via exocytosis
6. Neurotransmitter diffuses across synaptic cleft
7. Neurotransmitter binds to ligand-gated sodium channels on muscle

Question 21

Explain the processes of Excitation-Contraction Coupling

Answer 21

1. Action potential arrives at the axon terminal and ACh (acetylcholine) is released
2. ACh binds to the ligand-gated sodium channels and sodium enters the muscle
3. Action potential runs along
   sarcolemma and t-tubules initiating the release of calcium
4. Calcium binds to troponin, moving tropomyosin and exposing the binding site on actin
5. Myosin binds to actin and pulls the thin filaments toward the thick filaments (CONTRACTION)
6. The action potential stops and calcium is transported out of the sarcoplasm
7. Troponin moves the tropomyosin back to blocking the binding sites on actin (RELAXATION)

Question 22

Explain the four stages of Cross-Bridge Cycling

Answer 22

1. Myosin heads break down ATP and become reorientated
2. Myosin heads bind to actin forming cross-bridges
3. Myosin heads rotate towards the centre of the sarcomere (power stroke)
4. ATP binds to myosin heads, causing myosin to detach from actin

Question 23

What are the four factors which contribute to muscle contractile force (many cross bridges being formed in sarcomere)

Answer 23

1. Number of Muscle Fibers recruited
2. Size of individual muscle fibers
3. Frequency of the stimulation
4. Stretch of the Sarcomere