ET: Muscle

Question 1

What are the 5 levels of skeletal muscle?

Question 2

What is the I-band?

Answer 2

The part of the sarcomere where there is only actin (thin filaments)

contains the Z-line

Question 3

What is the a band?

Answer 3

The area where there is both thick and think filaments

Question 4

Wht is the H zone?

Answer 4

the area where there are ony thick (myosin) filament contains M line

Question 5

What are the M-line and Z- line?

Answer 5

M line is Middle of mysin filament

Z-line is where two Think/ actin filaments meet

Question 6

What are 2 accessory proteins on the thin filament and what are their roles?

Answer 6

troponin - Is regulated by Ca2+ - Exposes mysin binding site on think filament

tropomyosin- Interacts with myosin

Question 7

What is the t-tubule? what is its role?

Answer 7

an invagination in the I-band of the sarcomere. It allows action potentials to be carried deep into the muscle cell

Question 8

What is the sarcoplasmic reticulum?

Answer 8

The calcium storage site, it is near the T tubules to allow calcium into the sarcomeres.

Question 9

What are the 4 steps of the cross-bridge cycle?

Answer 9

1. Myosin binds to the actin binding site to form a cross bridge
2. The power stroke
3. Detachment
4. Energisation of the Myosin head

Question 10

What occurs in step one of the cross bridge formation

Answer 10

Myosin binds to the actin binding site to form across bridge in the presence of calcium

Question 11

What happens in step to the powerstroke?

Answer 11

ADP is released the Myosin head rotates to its low energy state and the sarcomere shortens

Question 12

What happens in step three detachment?

Answer 12

A new ATP molecules binds this allows the head of the myosin filament to detach.

Question 13

What happens in steps for energisation?

Answer 13

The Myosin head hydrolyses ATP and the head moves back to its high energy or cocked confirmation

Question 14

How does calcium affect the cross bridge cycle

Answer 14

Calcium binds with Troponin and this causes the tropomyosin to move to expose the myosin binding sites on the Actin

Question 15

Is the difference between isotonic and isometric contraction

Answer 15

Isotonic contraction involves shortening the muscle isometric does not involve shortening the muscle

Question 16

Where does calcium originate?

Answer 16

ECM or SR

Question 17

In terms of the length tension relationship what occurs when the sarcomere is <2.0um?

Answer 17

Active force is reduced because the ends of the filaments start to colide

Question 18

In terms of the length tension relationship what occurs when the sarcomere is >2.2um?

Answer 18

Passive force increases as elastic connective tissue is streched the active force decline as there is less overlap between the filaments.

Question 19

What is the maximal force range?

Answer 19

2.0-2.2 um

Question 20

What are the 5 steps required for contraction?

Answer 20

1. A nerve impulse travels down the motor neuron and triggers the release of Ca2+
2. Ca2+ triggers the release of ACh into the NMJ
3. ACh Defuses across the synaptic cleft and binds to its receptor on the motor end plate
4. ACh binding to ligand gated ion channels allows Na+ to enter the cell
5. If there is a large enough influx the VG- ion channels open and this causes and AP

Question 21

What can creatine phosphate do?

Answer 21

Act as a store of ATP ~15s

CP + ADP –> Creatine + ATP

Question 22

What are the benefits and disadvantages of anaerobic glycolysis

Answer 22

1. Good for short intense exercise
2. Dominant system for 10-30s
3. Build up of lactate = max 120s

Question 23

What are the benefits and disadvantages of aerobic metabolism

Answer 23

1. Efficient but comparatively slow
2. requires oxygen therefore good blood
3. supply max 300 W
4. important for postural muscles and endurance exercises

Question 24

What are type 1 muscle fibres

Answer 24

aerobic small Slow twitch muscles

Question 25

What are type 2 muscle fibres

Answer 25

Anaerobic large fast twitch fibres

Question 26

what are the two factors that regulate force?

Answer 26

1. Rate of summation of individual motor units
2. the number of motor units recruited

Question 27

What are the 6 main differences between skeletal and cardiac muscle

Answer 27

1. Skeletal muscle is up to 35 cm cardiac is 100um
2. Skeletal muscle is cylindrical in shape cardiac muscle is branched
3. Skeletal muscle is neurogenic (voluntary) cardiac muscle is myogenic (involuntary)
4. Skeletal muscle T tubules are at AI band intersection cardiac muscle T tubules are in the ventricles at the z-lines
5. Skeletal muscle has extensive SR cardiac muscle has rudimentary SR
6. Skeletal muscle is electrically isolated cardiac muscle is electrically coupled

Question 28

What are the steps involved in cardiac contraction?

Answer 28

1. Na+ enters rapidly causing RMP -90 –> +30
2. Ca2+ enters through DHPR on Sarcolemma
3. Ca2+ entering triggers RyRa which releases more Ca2+
4. Increase in Ca2+ –> Contraction

Question 29

What are the 4 ways that Ca2+ leves the Cytosol of cardiac tissue

Answer 29

1. SR Ca2+ ATPas
2. Sarcolemmal Na2+/Ca2+ exchanger
3. Sarcolemmal Ca2+ ATPas
4. Mitochondrial Ca2+ uniporter

Question 30

How is cardiac output calculated?

Answer 30

CO = SV x HR