Muscles

Question 1

what are tendons

Answer 1

lengths of strong connective tissue that connect muscles to bones

Question 2

what are ligaments

Answer 2

lengths of strong connective tissue but they connect bones to other bones

Question 3

what is the movement of muscles

Answer 3

contracting or pulling, they cannot push

Question 4

what is antagonistic muscle action

Answer 4

A muscle pulls in one direction at a joint and the other muscle pulls in the opposite direction

Question 5

how can you raise the lower arm

extensor / flexor

Answer 5

The bicep contracts and the tricep relaxes

As the bone can’t be stretched the arm flexes around the joint

A muscle that bends a joint during contraction is known as a flexor (the bicep in this case)

This brings the tricep into its full length so that it can contract again

Question 6

how can you lower the lower arm

extensor / flexor

Answer 6

The tricep contracts and bicep relaxes

As the bone can’t be stretched the arm flexes around the joint

A muscle that straightens a joint during contraction is known as an extensor (the tricep in this case)

Question 7

what do skeletal muscle make up

Answer 7

the muscles in the body that are attached to the skeleton

Question 8

what is skeletal muscle made up of

Answer 8

muscle fibres

Question 9

structure of muscle fibre

Answer 9

contains an organised arrangement of contractile proteins in the cytoplasm

surrounded by a cell surface membrane

contains many nuclei (multi-nucleated) – this is why muscle fibres are not usually referred to as cells

Question 10

what is the following names for a muscle fibre
cell surface membrane
cytoplasm
endoplasmic reticulum

Answer 10

Sarcolemma
sarcoplasm
sarcoplasmic reticulum

Question 11

details of sarcolemma

Answer 11

T-tubules that run close to the sarcoplasmic reticulum and help spread electrical impulses throughout muscle fibre

Question 12

details of sarcoplasm

Answer 12

contains mitochondria and myofibrils

The mitochondria carry out aerobic respiration to generate the ATP required for muscle contraction

Myofibrils are bundles of actin and myosin filaments, which slide past each other during muscle contraction

Question 13

what do the membranes of the sarcoplasmic reticulum contain and why is this needed

Answer 13

protein pumps that transport calcium ions into the lumen of the SR

Calcium ions are needed for the contraction of muscle

Question 14

where are myofibrils located and what are they made up of

Answer 14

located in the sarcoplasm
Each myofibril is made up of two types of protein filament:
Thick filaments made of myosin
Thin filaments made of actin

Question 15

what does the rapid contraction - relaxation of fast twitch muscle fibres mean

Answer 15

The myosin heads bind and unbind from the actin-binding sites faster than slow twitch muscle fibres so they need large amounts of calcium ions present to stimulate contraction

Question 16

what do fast twitch muscle fibres rely on

Answer 16

anaerobic respiration for ATP supply

Question 17

why are fast twitch muscle fibres suited to short bursts of high intensity activity

Answer 17

as they fatigue quickly due to the lactate produced from anaerobic respiration

Question 18

fast twitch muscle fibres have fewer capillaries what does this mean

Answer 18

This means they have quite a slow supply of oxygen and glucose for aerobic respiration

Question 19

is there high or low amounts of myoglobin present in fast twitch muscle fibres and and what does this cause

Answer 19

Low amounts of myoglobin are present in fast twitch muscle fibres

Due to this fast twitch muscle fibres appear paler in colour than slow muscle fibres

Question 20

what is myoglobin

Answer 20

Myoglobin is a red pigment molecule that is similar to haemoglobin

Myoglobin functions as a store of oxygen in muscles and increases the rate of oxygen absorption from the capillaries

Question 21

describe contraction of slow twitch muscles and what are they best suited to

Answer 21

Slow twitch muscle fibres contract more slowly and are suited to sustained activities like walking

Question 22

what do slow twitch muscles rely on

Answer 22

aerobic respiration for ATP

Question 23

why do slow twitch muscles fatigue less quickly

Answer 23

due to less lactate production, making them ideal for endurance

Question 24

what are found in high amounts in slow twitch muscle fibres and why

Answer 24

High amounts of myoglobin, haemoglobin and mitochondria are present in slow twitch muscle fibres

This increases the rate of oxygen supply, oxygen absorption and aerobic respiration

Question 25

what type of molecules are found are in thick filaments within a myofibril and what is the structure of these molecules

Answer 25

myosin molecules

These are fibrous protein molecules with a globular head

The fibrous part of the myosin molecule anchors the molecule into the thick filament

In the thick filament, many myosin molecules lie next to each other with their globular heads all pointing away from the M line

Question 26

what molecule is found in thin filaments within a myofibril and what is the structure of them

Answer 26

actin molecules

These are globular protein molecules

Many actin molecules link together to form a chain

Two actin chains twist together to form one thin filament

A fibrous protein known as tropomyosin is twisted
around the two actin chains

Another protein known as troponin is attached to the actin chains at regular intervals

Question 27

explain the sliding filament theory of muscle contraction

Answer 27

1. Calcium ions released from sarcoplasmic reticulum upon nervous stimulation.
   Bind to troponin molecule - changing its shape.

Troponin protein changes position on the actin (thin) filaments
Myosin binding sites are exposed on the actin molecules

2. Myosin head moves forward to form an actomyosin bridge.
3. ADP + Pi released, myosin head moves forwards - shortening the sarcolemma.
4. Free ATP binds, myosin head changes shape - moving back to original position.
5. ATPase in myosin head breaks ATP back into ADP + Pi to restore the original state.
6. Repeated stimulation causes continued contraction. If stimulation is stopped,
   ATP released is used to actively transport calcium ions back into sarcoplasmic reticulum.

Question 28

what happens once muscle stimulation has stopped

Answer 28

calcium ions leave their binding sites on troponin molecules

They are actively transported back to SR

Without calcium ions bound to them, the troponin molecules return to their original shape

This pulls the tropomyosin molecules in a position that blocks the actin-myosin binding sites

Since no cross bridges can form between actin and myosin, no muscle contraction can occur

The sarcomere will lengthen again as actin filaments slide back to their relaxed position

Question 29

why may EPO have less of an effect on sprinter than long distance runner

sprinter has more fast twitch fibres
EPO stimulates formation of red blood cells

Answer 29

RBC will {carry/supply oxygen};
idea that low number of mitochondria present in fast twitch;
so additional oxygen may have limited additional effect / eg;
poor {blood supply / capillary network} in fast twitch muscle so little additional {oxygen / RBC / eq} received / eq;
(in fast twitch) respiration is (primarily) anaerobic / eq;
short {time duration of race/distance travelled} means minimal additional blood supplied to muscles in timeframe;

Question 30

two ethical reasons why the use of drugs such as EPO should be banned from sports

Answer 30

idea of not being fair;
idea of being a poor role model for youngsters;
health risk to athletes / eq;
cost to {NHS / medical services / eq} of health implications