Muscles Flashcards
what are tendons
lengths of strong connective tissue that connect muscles to bones
what are ligaments
lengths of strong connective tissue but they connect bones to other bones
what is the movement of muscles
contracting or pulling, they cannot push
what is antagonistic muscle action
A muscle pulls in one direction at a joint and the other muscle pulls in the opposite direction
how can you raise the lower arm
extensor / flexor
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
how can you lower the lower arm
extensor / flexor
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)
what do skeletal muscle make up
the muscles in the body that are attached to the skeleton
what is skeletal muscle made up of
muscle fibres
structure of muscle fibre
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
what is the following names for a muscle fibre
cell surface membrane
cytoplasm
endoplasmic reticulum
Sarcolemma
sarcoplasm
sarcoplasmic reticulum
details of sarcolemma
T-tubules that run close to the sarcoplasmic reticulum and help spread electrical impulses throughout muscle fibre
details of sarcoplasm
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
what do the membranes of the sarcoplasmic reticulum contain and why is this needed
protein pumps that transport calcium ions into the lumen of the SR
Calcium ions are needed for the contraction of muscle
where are myofibrils located and what are they made up of
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
what does the rapid contraction - relaxation of fast twitch muscle fibres mean
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
what do fast twitch muscle fibres rely on
anaerobic respiration for ATP supply
why are fast twitch muscle fibres suited to short bursts of high intensity activity
as they fatigue quickly due to the lactate produced from anaerobic respiration
fast twitch muscle fibres have fewer capillaries what does this mean
This means they have quite a slow supply of oxygen and glucose for aerobic respiration
is there high or low amounts of myoglobin present in fast twitch muscle fibres and and what does this cause
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
what is myoglobin
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
describe contraction of slow twitch muscles and what are they best suited to
Slow twitch muscle fibres contract more slowly and are suited to sustained activities like walking
what do slow twitch muscles rely on
aerobic respiration for ATP
why do slow twitch muscles fatigue less quickly
due to less lactate production, making them ideal for endurance
what are found in high amounts in slow twitch muscle fibres and why
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
what type of molecules are found are in thick filaments within a myofibril and what is the structure of these molecules
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
what molecule is found in thin filaments within a myofibril and what is the structure of them
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
explain the sliding filament theory of muscle contraction
- 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
- Myosin head moves forward to form an actomyosin bridge.
- ADP + Pi released, myosin head moves forwards - shortening the sarcolemma.
- Free ATP binds, myosin head changes shape - moving back to original position.
- ATPase in myosin head breaks ATP back into ADP + Pi to restore the original state.
- Repeated stimulation causes continued contraction. If stimulation is stopped,
ATP released is used to actively transport calcium ions back into sarcoplasmic reticulum.
what happens once muscle stimulation has stopped
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
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
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;
two ethical reasons why the use of drugs such as EPO should be banned from sports
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
