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Animal responses

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What is skeletal muscle made up of?
large bundles of long cells called muscle fibres.
The autonomic nervous system
Controls unconscious activities e.g.heart rate
Stimulus
Any change in the internal or external environment
Receptors
Detect stimuli
Effectors
Bring about response to stimuli
The central nervous system
Made up of brain and spinal cord
The peripheral nervous system
Made up of neurones that connect the CNS to the rest of the body
The somatic nervous system
Controls conscious activities e.g. Running and playing video games
The sympathetic nervous system
'Fight or flight' response which gets the body ready for action and this releases the neurotransmitter noradrenaline.
The parasympathetic nervous system
The 'rest and digest' system which calms the body down and this releases the neurotransmitter acetylcholine.
Cerebrum
The largest part of the brain which is divided into two halves called cerebral hemispheres. It has a thin outer layer called the cerebral cortex, which is highly folded. It is involved in vision, hearing, learning and thinking.
Hypothalamus
Found just beneath the middle part of the brain. It automatically maintains body temperature at a normal level and produces hormones that control the pituitary gland.
Medulla oblongata
At the base of the brain and at the top of the spinal Cora and automatically controls breathing and heart rate.
Cerebellum
Underneath the cerebrum and has a folded cortex. It is important for muscle co ordination, posture and coordination of balance.
Pituitary gland
Found underneath and is controlled by the hypothalamus. It release hormones and stimulates other glands (adrenal glands) to release hormones.
Blinking reflex action
STIMULUS-something touching the eye
RECEPTORS- sensory nerve endings in the cornea detect the touch stimulus. A nerve impulse is sent along the sensory neurone to a relay neurone in the CNS.
CNS- the impulse is passed from the relay to the motor neurone
EFFECTORS- the motor neurones send impulses to the orbicularis oculus muscles that move the eyelids.
RESPONSE- the muscles contract causing the eyelids to close quickly and prevent them from being damaged.
Knee-jerk reflex
STIMULUS- quadriceps muscle is stretched.
RECEPTORS- stretch receptors in the quadriceps muscle detect that the muscle is being stretched. A nerve impulse is passed along the sensory neurone.
CNS- the sensory neurone communicated directly with a motor measuring in the spinal cord (no relay neurone involved)
EFFECTORS- motor Beatrice carries the nerve impulse to the quadriceps muscle.
RESPONSE- the quadriceps muscle contracts so the lower leg moves forward quickly.
The 'fight or flight' response
Nerve impulses from the sensory neurone arrive at the hypothalamus, activating the hormonal (endocrine) and sympathetic nervous system. The pituitary glad is stimulated to release ACTH, causing the cortex of the adrenal gland to release steroidal hormones which have a range of effects and help the body to respond to both short and long term stressors. The sympathetic nervous system is activated triggering the release of adrenaline from the medulla region of the adrenal gland. This produces a faster response than the hormones secretes by the cortex of the adrenal glands.
Effects of fight or flight response
-heart rate increases and heart contracts with more force causing blood to be lumped around the body faster.
-the muscles around the bronchioles relax causing the airways to widen so breathing is deeper
-intercostal muscles and diaphragm contract faster and with more strength increasing the rate and depth of breathing
-glycogen is converted to glucose via glycogenesis so more glucose is available for the muscles to respite
-muscles in the arteriolar supplying the skin and gut constrict and muscles in the arterioles supplying the heart lungs and skeletal muscles dilate son blood is diverted from the skin and gut to the heart, lungs and skeletal muscles. This increases blood flow to skeletal muscles making them ready for action
-erector pill muscles in the skin contract making hairs stand on end so the animal looks bigger
Baroreceptors
Pressure receptors in the aorta and carotid arteries. They're stimulated by high and low blood pressure
Chemoreceptors
Chemical receptors in the aorta, carotid arteries and medulla oblongata. They monitor oxygen level in the bloody and carbon dioxide and pH.
Control of heart rate in response to high blood pressure
Baroreceptors detect it and send impulses along sensory beauties to cardiovascular centre which sends impulses along parasympathetic neurone which secrete acetylcholine which binds to receptors on the SAN causing heart rate to slow down to reduce blood pressure back to normal
Control of heart rate in response to low blood pressure
Baroreceptors detect and send impulses along sensory beau tones to the cardiovascular centre which sends impulses along sympathetic neurones. This causes he heart rate to speed up in order to increase blood pressure back to normal.
Control of heart rate in response to high oxygen, low carbon dioxide and high blood pH
Chemoreceptors detect change and sends impulses along sensory neurone to cardiovascular centre which send impulses along parasympathetic neurones. They secrete acetylcholine which binds to receptors in the SAN causing heart rate to decrease to return oxygen carbon dioxide and pH levels back to normal
Control of heart rate in response to low patten high carbon dioxide and low blood pH
Chemoreceptors detect change and sends impulses along sympathetic neurones. They secrete noradrenaline which bind to receptors on the SAN to increase heart rate so oxygen levels return to normal.
Measuring the effect of different factors on heart rate
Measure heart rate at rest and record in a table: count beats in 15 seconds then multiply by 4 to get beats per minute.
Do the activity that will test the factors eg running if measuring effect of exercise.
Return to resting position and measure heart rate every minute until it returns to normal. Record how long this takes.
How to carry out the student t-test
1. Identify the null hypothesis: 'no significant difference'
2. Calculate the mean and standard deviation for each data set.
3. Use the formula
4. Calculate the degrees of freedom by (n1-n2)-2
5. Look up the value for t in the table of critical values. If the value obtained is greater than the critical value at a P value of 5% or less, then you can be 95% confident that the difference is significant and not due to chance.
6. The null hypothesis is then rejected
How muscular movement is coordinated
The CNS sends signals along neurones to the skeletal muscles.
What are the long, cylindrical organelles that muscle fibres contain?
Microfibrils, which are made of proteins that are highly specialised for contraction.
What is skeletal muscle made up of?
Large bundles of long cells called muscle fibres.
What is the structure and function of the cell membrane of muscle fibres?
The cell membrane of the muscle fibres, called the sarcolemma, fold inwards across the muscle fibre and stick into the sarcoplasm. These folds are called transverse (T) tubules and help to spread electrical impulses throughout the sarcoplasm so they reach all parts of the muscle fibre.
What does the sarcoplasmic reticulum do?
It is a network of internal membranes that runs through the sarcoplasm and stores and releases calcium ions that are needed for muscle contraction.
Why do muscle fibres contain lots of mitochondria?
To provide the ATP needed for muscle contraction.
Muscle fibres are multinucleate. What does this mean?
They contain many nuclei
What do myofibrils contain bundles of?
Thick and thin myofilaments that move past each other to make the muscle contract.
What protein are the thin myofilaments made up of?
actin
What protein are the thick myofilaments made up of?
Myosin
What are A bands?
Dark bands that contain the thick myosin filaments and some overlapping thin actin filaments.
What are I-bands?
Light bands containing thin actin filaments only.
What are the short units that make up myofibrils?
Sarcomeres
What are the ends of each sarcomere marked with?
A Z-line
What's the M-line
The middle of each sacomere and is the middle of the myosin filament.
What is the H-zone
It is around the M-line and only contains myosin filaments.
Sliding filament theory
1. Myosin and actin slide over each other to make the sarcomeres contract.
2. The simultaneous contraction of lots of sarcomeres causes the myofibrils and muscle fibres to contract
3. Sarcomeres return to original length as muscle relaxes.
What enables the myosin filaments to move back and fourth?
The hinged, globular heads
Binding sites on myosin
Has one for actin and one for ATP
Binding sites for actin filaments
Has one for myosin heads, called actin-myosin binding sites
What are the other proteins between actin filaments and what is their function?
Tropomyosin and troponin are attached to each other and help myofilaments move past each other
What happens to binding sites in resting muscle?
The actin myosin bind no sites are blocked by tropomyosin which is held in place by troponin. This means myofilaments can't slide past eachother as the myosin heads can't bind to the binding site.
What is muscle contraction triggered by?
An action potential
What happens when an action potential from a motor neurone stimulates a muscle cell?
It depolarises the sacrolema, this depolarisation spreads down the T-tubules to the sacroplasmic reticulum which then releases calcium ions into the sacroplasm
What happens when there's an influx of calcium ions in the sacroplasm
They bind to troponin, causing it to change shape and pull tropomyosin out of the actin myosin binding site on the actin filament, the myosin head can then bind.
What is the bond called that is formed when the myosin head binds to the actin filament?
An actin-myosin cross bridge
How does ATP move the myosin head?
Calcium ions activate ATPase which breaks down ATP to release energy. As the head moves, the actin filament is pulled along.
How does the actin-myosin cross bridge break?
ATP provides the energy and so the myosin head detaches form the actin filament after it has moved.
The myosin head then reattaches to a different binding site further along and a new cross bridge is formed, so the cycle is repeated. (ATTACH, MOVE, DETACH, REATTACH)
How does the sarcomeres shorten?
Many cross bride break and form rapidly pulling the actin filaments along which shortens the sarcomeres causing a contraction.
What happens when the muscle stops being stimulated
The calcium ions leave their binding sites on the troponin molecules and are moved by active transport back into the sarcoplasmic reticulum.
The troponin molecules return to their original shape, pulling the attached tropomyosin molecules with them, blocking the binding sites again.
Muscles don't contract as myosin heads don't bind to actin filaments.
The actin filaments return to their re,axed position, which lengthens to sarcomere.
How does aerobic respiration generate ATP?
And when is it useful?
Oxidative phosphorylation which occurs across the inner mitochondrial membrane.
Good for long period of low intensity exercise.
How does anaerobic respiration generate ATP? And how is it useful?
Made rapidly by glycolysis.
But...Pyruvate is then converted to lactate in lactate fermentation and this can build up quickly and cause muscle fatigue.
It's good for shirt periods of hard exercise.
What is the ATP-Creatine Phosphate system and how is this used to generate ATP and when is it used?
The phosphate group added to ATP by phosphorylation is taken for Creatine phosphate (CP).
This is stored inside cells and the system generates ATP very quickly.
Cap runs out after a few seconds so it's used during shirt outbursts of vigorous exercise.
This system is anaerobic and alactic (doesn't form lactate)
What are neuromuscular junctions?
Synapses between motor neurones and muscle cells.
What are the receptors that acetylcholine (ACh) bind to?
Nicotinic cholinergic receptors
What happens when ACh is released
Depolarisation is triggered in the post synaptic cell, causing muscle cells to contract is threshold is reached.
What is used to break down ACh?
Acetylcholinesterase (AChE) which is stored in chefs on the post synaptic membrane
What can happen if a chemical (drug) blocks the release of the neurotransmitter or affects the way it binds to receptors on the postsynaotic membrane?
The action potential can be prevented from passing onto the muscle and so I won't contract. This can be fatal if it affects muscles such as the diaphragm and kinder costal muscles involved in ventilation, as the organism will not be able to respire aerobically.
Structure of skeletal muscle (voluntary muscle)
Made up of many multinucleate muscle fibres which can be up to many centimetres long. Regular cross-striatum can be seen under a microscope.
Function of skeletal muscle
-Controlled consciously.
-Some muscle fibres contract very quickly and are used for speed and strength, but fatigue quickly.
-Some fibres contract and fatigue slowly and are used for endurance and posture.
Structure of involuntary/smooth muscle
-doesn't have the striped appearance of skeletal muscle.
- each muscle fibres has one nucleus and are spindle shaped with pointed ends and are only about 0.22mm long.
Function of involuntary muscle
-controlled unconsciously
-found in the walls of the hollow internal organs eg. The gut and blood vessels.
- gut smooth muscle contracts to move food along (peristalsis)
- blood vessel smooth muscle contracts to reduce the flow of the blood.
- the muscle fibres contract slowly and don't fatigue.
Structure of cardiac muscle.
- made of muscle connected by intercalated discs, which have low electrical resistance, so nerve impulses can pass easily between cells.
-The muscle cells are branched to allow nerve impulses to spread quickly through the whole muscle
-each muscle fibres has one nucleus, are shaped like cylinders and are about 0.1mm long
-contracts on its own--it's myogenic
-can see some cross sections but not as strong as on voluntary muscle.
-muscle fibres contract rhythmically and don't fatigue.
How are electrical signals used to monitor muscle fatigue: ELECTROMYOGRAPHY
1) attach two electrodes to the places on the muscle which you want to record from. A third electrode goes in an inactive point to act as a control.
2) switch off any electrical equipment that will interfere with the electrical signal from the muscle.
3) connect the electrodes to an amplifier and computer
4) keep the muscle relaxed- this should form a straight line on the electromyogram.
5) contract the muscle and spikes should be shown on the graph as the motor units are activated to contract the muscle.
6) undergo activity to increase amplitude of the trace on the graph
7) if the activity is continued the muscle fatigued and the amplitude of the race will increase further as the brain is trying to activate more motor units to generate the force needed.
Structure of skeletal muscle (voluntary muscle)
Made up of many multinucleate muscle fibres which can be up to many centimetres long. Regular cross-striatum can be seen under a microscope.
Function of skeletal muscle
-Controlled consciously.
-Some muscle fibres contract very quickly and are used for speed and strength, but fatigue quickly.
-Some fibres contract and fatigue slowly and are used for endurance and posture.
Structure of involuntary/smooth muscle
-doesn't have the striped appearance of skeletal muscle.
- each muscle fibres has one nucleus and are spindle shaped with pointed ends and are only about 0.22mm long.
Function of involuntary muscle
-controlled unconsciously
-found in the walls of the hollow internal organs eg. The gut and blood vessels.
- gut smooth muscle contracts to move food along (peristalsis)
- blood vessel smooth muscle contracts to reduce the flow of the blood.
- the muscle fibres contract slowly and don't fatigue.
Structure of cardiac muscle.
- made of muscle connected by intercalated discs, which have low electrical resistance, so nerve impulses can pass easily between cells.
-The muscle cells are branched to allow nerve impulses to spread quickly through the whole muscle
-each muscle fibres has one nucleus, are shaped like cylinders and are about 0.1mm long
-contracts on its own--it's myogenic
-can see some cross sections but not as strong as on voluntary muscle.
-muscle fibres contract rhythmically and don't fatigue.
How are electrical signals used to monitor muscle fatigue: ELECTROMYOGRAPHY
1) attach two electrodes to the places on the muscle which you want to record from. A third electrode goes in an inactive point to act as a control.
2) switch off any electrical equipment that will interfere with the electrical signal from the muscle.
3) connect the electrodes to an amplifier and computer
4) keep the muscle relaxed- this should form a straight line on the electromyogram.
5) contract the muscle and spikes should be shown on the graph as the motor units are activated to contract the muscle.
6) undergo activity to increase amplitude of the trace on the graph
7) if the activity is continued the muscle fatigued and the amplitude of the race will increase further as the brain is trying to activate more motor units to generate the force needed.
How the hormonal system controls heart rate
When an organism is threatened the adrenal glands release adrenaline which binds to specific receptors in the heart causing the cardiac muscle to contract more frequently and with more force so heart rate increases and the blood pumps more blood.
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