Topic 6 Skeletal muscle cells...

Question 1

To generate tension, skeletal muscle cells must be stimulated by a nerve signal from what?

Answer 1

Motor neuron

Question 2

A nerve cell that stimulates muscles to contract

Answer 2

Motor neuron

Question 3

Neurological control…
The axon connects with the muscle
when it reaches the muscle, it branches out into a number of ?

Answer 3

axon terminals

Question 4

Neurological control…

Each axon terminal forms a junction called________ with the sarcolemma of a number of different muscle cells

Answer 4

neuromuscular junction

Question 5

Neurological control…

Do the axon terminal and the sarcolemma touch?

Answer 5

No

Question 6

Neurological control…

Gap b/w the axon terminal and the sarcolemma is called?

Answer 6

Synaptic cleft

Question 7

Neurological control…

What stimulates the sarcolemma and the muscle to continue the nerve signal

Answer 7

Neurotransmitter (Acetylcholine (ACh))

which crosses the synaptic clef

Question 8

Sliding Filament Mechanism

Answer 8

1- Nerve signal reaches the muscle via the synaptic clef
2- Signal then continues via the muscle fibres and spreads out across the sarcolemma
3- Signal then travels down the Transverse Tubules and stimulates the release of Calcium by the Sarcoplasmic Reticulum
4- Calcium allows the Myosin (thick filaments) to connect to the Actin (thin filaments)
5- Myosin pulls (‘slides) the actin/thin filaments together
6- it disengages and starts the cycle again
7- this ‘ratcheting’ of filaments uses ATP
8- with repetition, it shortens the sarcomere > the myofibril > the muscle fibre > the muscle

Question 9

What happens when the APs stop within the ‘sliding filament mechanism’?

Answer 9

1- when Action potentials stop, the sarcoplasmic reticulum pumps calcium back inside (this uses ATP)
2- without sufficient calcium > thick filaments (myosin) can’t continue to ratchet the thin filaments (actin)
3- tension generation stops

Question 10

Motor Unit

Answer 10

Motor neuron and all the skeletal muscle fibres it innervates

• Each muscle fibre is controlled by one motor unit

Question 11

Production of ATP in the Muscle Fibres…
Skeletal muscle fibres need to vary the levels at which they consume ATP
Muscle fibres strore enough ATP to last for 3 seconds
Beyond this, there are 3 ‘energy pathways’ through which ATP can be generated - Name them…

Answer 11

1) Creatine Phosphate
2) Anaerobic glycolysis
3) Aerobic cellular respiration

Question 12

It is a molecule that stores high amounts of energy in its chemical bond;
This system provides energy for 3-15 seconds of maximal contraction

Answer 12

Creatine phosphate

Question 13

Aka for Creatine Phosphate

Answer 13

Phosphatecreatine, ATP-PCr
Anaerobic Alactic (no oxygen - no lactic acid)

Question 14

This type of energy pathway is capable of supplying energy for 30-40 seconds;
Glycose is used to make ATP (when muscle activity continues and PCr is depleted);
Produces lactic acid without oxygen

Answer 14

Anaerobic Glycolysis

Question 15

It is a by-product of anaerobic glycolysis;

Has a 1/2 life of 15-25 minutes and is cleared in a matter of hours

Answer 15

Lactic acid

Question 16

This energy pathway is active when you are able to get oxygen in to the cells;
Oxygen is delivered by myoglobin;
Through the presence of oxygen, pyruvic acid enters the mitochondria and in a series of reactions > produces ATP;
Carbohydrates, Fats and proteins can be used in this system
In activities that last longer than 10 minutes, most (90%) of ATP generated comes from this system

Answer 16

Aerobic Cellular Respiration