Module 5: Section 3 Animal Responses

Question 1

What structures is the nervous system split into

Answer 1

The central nervous system
The peripheral nervous system

Question 2

What is the central nervous system made up of?

Answer 2

The brain and spinal cord

Question 3

What is the peripheral nervous system split into?

Answer 3

The somatic nervous system
The autonomic nervous system

Question 4

What is the function of the somatic nervous system?

Answer 4

The somatic nervous system controls conscious activities eg running and playing video games

Question 5

What is the function of the autonomic nervous system?

Answer 5

The autonomic nervous system controls unconscious activities eg digestion and heart rate

Question 6

What is the autonomic nervous system split into?

Answer 6

The sympathetic nervous system
The parasympathetic nervous system

Question 7

What is the function of the sympathetic nervous system?

Answer 7

It is the “fight or flight” system that gets the body ready for action. Sympathetic neurones release neurotransmitter noradrenaline.

Question 8

What is the function of the parasympathetic nervous system?

Answer 8

It is the “rest and digest” system that calms the body down. Parasympathetic neurones release the neurotransmitter acetylcholine.

Question 9

What are the five brain structures you have to know?

Answer 9

1) cerebrum
2) hypothalamus
3) medulla oblongata
4) cerebellum
5) pituitary gland

Question 10

What is the location and function of the cerebrum?

Answer 10

Cerebrum is the largest part of the brain and is divided into two halves called cerebral hemispheres. The cerebrum has a thin outer layer called the cerebral cortex, which is highly folded. The cerebrum is involved in vision, hearing, learning and thinking.

Question 11

What is the location and function of the hypothalamus?

Answer 11

The hypothalamus is found just beneath the middle part of the brain. It automatically maintains body temperature at a normal level. It also produces hormones to control the pituitary gland.

Question 12

What is the location and function of the medulla oblongata?

Answer 12

The medulla oblongata is at the base of the brain, at the top of the spinal cord. It automatically controls breathing rate and heart rate.

Question 13

What is the location and function of the cerebellum?

Answer 13

The cerebellum is underneath the cerebrum and it also has a folded cortex. It’s important for muscle coordination, posture and coordination of balance.

Question 14

What is the location and function of the pituitary gland?

Answer 14

The pituitary gland is found beneath and is controlled by the hypothalamus. It releases hormones and stimulates other glands eg the adrenal glands to release their hormones.

Question 15

What is a reflex action?

Answer 15

Where the body responds to a stimulus without making a conscious decision to respond.

Question 16

What is the pathway for a reflex action?

Answer 16

1) stimulus to receptors
2) receptors to CNS (via sensory neurone)
3) CNS to effectors (via relay and motor neurone)
4) effectors to response

Question 17

Why do you have a blinking reflex?

Answer 17

The body detects something that could damage your eye, so you quickly close your eyelid to protect the eye.

Question 18

What is the pathway of communication for the blinking reflex?

Answer 18

1) stimulus - something touches your eye
2) receptors - sensory nerve endings in the cornea detect the touch stimulus. A nerve impulse is seng along the sensory neurone to a relay neurone in the CNS.
3) CNS - the impulse is then passed from the relay to motor neurones
4) effectors - the motor neurone send impulses to the obicularis oculi muscles that move your eyelids.
5) response - these muscles contract causing eyelids to close quickly and prevent them from being damaged.

Question 19

Why do we have the knee-jerk reflex?

Answer 19

It works to quickly straighten your leg if the body detects your quadriceps is suddenly stretched. It helps to maintain posture and balance.

Question 20

What is the pathway of communication for the knee-jerk reflex?

Answer 20

1) stimulus- your quadricep muscle is stretched
2) receptors - stretch receptors in quadricep muscle detect that the muscle is being stretched and a nerve impulse is passed along the sensory neurone
3) CNS - the sensory neurone communicates directly with a motor neurone in the spinal cord (no relay neurone involved)
4) effectors - the motor neurone carries the nerve impulse ti the quadricep muscle
5) response - the quadriceps muscle contracts so the lower leg moves forward quickly.

Question 21

When does the fight or flight response happen?

Answer 21

When an organism is threatened it responds by preparing the body for action.

Question 22

When your body is placed under stress what happens?

Answer 22

Nerve impulses from sensory neurones arrive at the hypothalamus, activating both the hormonal (endocrine system) and the sympathetic nervous system. The pituitary gland is stimulated to release a hormone called ACTH. This causes the cortex of the adrenal gland to release steroidal hormones, which have a range of effects on the body, helping to respond to stress both short and long-term.

Question 23

What happens during the fight or flight response?

Answer 23

The sympathetic nervous system is activated, triggering the release of adrenaline from the medulla region of the adrenal gland. The sympathetic nervous system and adrenaline produce a faster response than hormones secreted by the cortex of the adrenal gland.

Question 24

What are the effects of adrenaline?

Answer 24

1) heart rate increases- the heart contracts with more force causing blood to be pumped around the body faster.

2) the muscles around the bronchioles relax, so airways widen and breathing is deeper

3) the intercostal muscles and diaphragm also contract faster and with more strength , increasing rate and depth of breathing.

4) glycogen is converted in glucose by glycogenesis so more glucose available for cells to respire.

5) muscles in the arterioles supplying skin and gut constrict, and muscles in the arterioles supplying the heart, lungs and skeletal muscles dilate so blood is diverted from the skin and gut to longs and skeletal muscles. This increases blood flow to these areas making them ready for action.

6) erector pili muscles in the skin contract, this makes hairs stand on end so the animal looks bigger.

Question 25

How is heart rate controlled by the nervous system?

Answer 25

The SAN generates electrical impulses that cause the cardiac muscles to contract. The rate at which the SAN fires (ie heart rate) is unconsciously controlled by the cardiovascular centre in the medulla oblongata.

Question 26

Why do animals need to alter their heart rate?

Answer 26

Animals need to alter their heart rate to respond to internal stimuli, eg to prevent fainting due to low blood pressure or to make sure the heart rate is high enough to supply the body with enough oxygen.

Question 27

How are internal stimuli detected in blood /heart ?

Answer 27

1) there are pressure receptors called baroreceptors in the aorta and the carotid arteries. They’re stimulated by high and low blood pressure.

2) there are chemical receptors called chemoreceptors in the aorta, the carotid arteries and in the medulla oblongata. They monitor the oxygen level in the blood, and also carbon dioxide and pH (indicator of O2 levels)

Question 28

How does the body respond to high blood pressure?

Answer 28

Baroreceptors detect high blood pressure and send impulses along sensory neurones to the cardiovascular centre, which sends impulses along parasympathetic neurones. These secrete acetylcholine, which binds ti receptors on the SAN. This causes heart rate to slow down in order to reduce blood pressure back to normal.

Question 29

How does the body respond to low blood pressure?

Answer 29

Baroreceptors detect low blood pressure and send impulses along sensory neurones to the cardiovascular centre, which sends impulses along sympathetic neurones. These secrete noradrenaline, which binds to receptors on the SAN. This causes heart rate to speed up in order to increase blood pressure back to normal.

Question 30

How does the body respond to high O2 levels/low CO2 levels ?

Answer 30

This means pH is high. Chemoreceptors detect chemical changes in the blood and send impulses along sensory neurones ti the cardiovascular centre, which sends impulses along the parasympathetic neurones. These secrete acetylcholine, which binds ti receptors on the SAN. This causes heart rate to decrease in order to return oxygen, carbon dioxide and pH levels back to normal.

Question 31

How does the body respond to low blood O2/ high CO2 levels?

Answer 31

This is when there is low blood pH levels. Chemoreceptors detect chemical changes in the blood and send impulses along sensory neurones to the cardiovascular centre, which sends impulses along sympathetic neurones. These secrete noradrenaline, which binds to receptors on the SAN. This causes heart rate to increase in order to return oxygen, CO2 and pH levels to normal. Happens when you exercise.

Question 32

How does the hormonal system control heart rate?

Answer 32

When an organism is threatened, the adrenal gland secretes adrenaline. Adrenaline bonds to specific receptors in the heart causing the cardiac muscles to contract more frequently and with more force so heart rate increases and the heart pumps more blood.

Question 33

Method to test how exercise affects heart rate?

Answer 33

1) measure heart rate at rest and record in a table. Do this by counting number of beats in 15 seconds and multiply by 4 to get beats per minute.

2) do some gentle exercise, such as stepping on and pff a step for 5 mins. Immediately after, measure heart rate again.

3) return to a resting position. Measure your heart rate every minute until it returns to a starting rate. Record how long it takes to return to normal.

Question 34

How do heart rate monitors work?

Answer 34

Electronic heart rate monitors usually consist of a chest strap and a wrist monitor. The chest strap contains electrodes which detect the electrical activity of the heart as it beats. The data is picked up by the electrodes and then transmitted wirelessly to the wrist monitor, which displays the data as a heart rate in beats per minute.

This is an advantage compared to manually taking your pulse as you can measure heart rate while exercising and keep a continual record of how it changes. It is also more accurate.

Question 35

When do you use student’s t-test?

Answer 35

Student t test is a statistical test used to find out whether there is significant difference in the means of two data sets. Critical value helps you decide how likely the results were due to chance.

Question 36

What are the steps to carry out a student t test?

Answer 36

1) first, you need to identify the null hypothesis. This is always that the two data sets will have the same mean

2) calculate the mean for both sets of data.

3) use the mean ti calculate the standard deviation for both data sets.

4) plug in means and standard deviations into student t test formula.

5) calculate degrees of freedom by doing (n1 + n2) - 2

6) look in table of critical values for the degrees of freedom. If the critical value in the table is less than the p value calculated, you reject the null hypothesis.

Question 37

What are skeletal muscle made up of?

Answer 37

They are made of large bundles of long cells called muscle fibres

Question 38

What is the structure of a muscle fibre?

Answer 38

1) the cell membrane of the muscle fibre is called the sarcolemma. Bits of the sarcolemma fold inwards across the muscle fibre and stick to the sacroplasm (a muscle cells cytoplasm). These foods are called transverse (T) folds and help spread electrical impulses throughout the sarcoplasm so they reach all areas of the muscle fibre.

2) a network of inner membranes called sacroplasmic retirculum runs through the sarcoplasm. The sarcoplasmic reticulum stirred and releases calcium ions needed for muscle contraction.

3) muscle fibres have lots of mitochondria to provide ATP for muscle contraction.

4) they are multinucleate (many nuclei) ans have lots of long cylindrical organelles called myofibrils. Myofibrils are made of proteins specialised for contraction

Question 39

What is the structure of myofibrils?

Answer 39

Myofibrils contain bundles of thick and thin myofilaments that move past each for muscle contraction. The thick myofilaments is the protein myosin. The thin microfilaments are the protein actin.

When looking under an electron microscope, you can see alternating dark and light bands. Dark bands are thick myosin filaments and overlapping thin actin filaments. These are called A-bands. Light bands contain thin actin filaments only. These are called I bands.

A myofibrils is made of many shirt units called sarcomeres.

Question 40

What is the structure of a sarcomere?

Answer 40

The ends of each sarcomere are marked with a Z-line. In the middle of each sarcomere is an M-line. The M line is in the middle of the myosin filaments. Across the M-line is the H-zone which only contains myosin filaments (no overlapping bits).

Draw it out

Question 41

What is the sliding filament model?

Answer 41

Muscle contraction is explained by the sliding filament model. Thus is where actin and myosin filaments Slide Over one another ti make sarcomeres contract. The myofilaments themselves don’t contract. The simultaneous contraction of lots of sarcomeres means myofibrils and muscle fibres contract. Sarcomeres return to their original length as the muscle relaxes.

A-band stays the same length. I-band gets shorter. H-zone gets shorter. Z-lines get closer together.

Question 42

What is the structure of a myosin filament?

Answer 42

Myosin filaments have globular heads that are hinged, so they can move back and forth. Each myosin heads has a binding site for actin and a binding site for ATP.

Question 43

What is the structure of actin filaments?

Answer 43

Actin filaments have binding sites for myosin heads called actin-myosin binding sites. Two other proteins called tropomyosin and troponin are found between actin filaments. These proteins are attached to each other (troponin holds tropomyosin in place) and they help myofilaments move past each other.

Question 44

What do binding sites look like in resting muscles?

Answer 44

In a resting muscle, the actin-myosin binding site is blocked by tropomyosin. This means myofilaments can’t slide past each other because the myosin heads can’t bind to the actin filaments

Question 45

What are the four stages of muscle contraction

Answer 45

1) arrival of an action potential
2) movement of the actin filament
3) breaking of the cross bridge
4) return to resting state

Question 46

What happens at the muscle when an action potential arrives?

Answer 46

When an action potential from a motor neurone stimulates a muscle cell, it depolarises the sarcolemma. Depolarisation spreads down the T-tubules to the sacriplasmic reticulum. This causes the sarcoplasmic reticulum to release stored calcium ions into the sarcoplasm.

Calcium ions bind to troponin, causing it to change shape. This pulls the attached tropomyosin out of the actin-myosin binding site on the actin filament. This exposes the binding site so myosin heads can now bind to it. A bond forms when a myosin head binds to an actin filament. This is called an actin-myosin cross bridge.

Question 47

What happens during the movement of the actin filament?

Answer 47

Calcium ions also activate the enzyme ATPase, which breaks down ATP (into ADP + Pi) to provide energy needed for muscle contraction. The energy released from ATP moves the myosin head to the side, which pulls the actin filament along like a rowing action.

Question 48

What happens during the breaking of the cross bridge?

Answer 48

ATP also provides the energy to break the actin-myosin cross bridge, so the myosin head detached from the actin filament after it’s moved. The myosin head then returns to its starting position, and reattaches to a different binding site further along the actin filament. A new actin-myosin cross bridge forms and the cycle repeats.

Many actin-myosin cross bridges form and break rapidly pulling actin filaments along, which shortens the sarcomere, causing the muscle to contract. The cycle continues as long as calcium ions are present and bound to troponin.

Question 49

How does the muscle return to resting state?

Answer 49

When the muscle stops being stimulated, calcium ions leave their binding site on the troponin molecules and are moved by active transport back into the sarcoplamsic reticulum (this needs ATP too). The troponin molecules return to their original shape, pulling the attached tropomyosin molecules with them, this means the tropomyosin molecules block the actin-myosin binding sites again.

Muscles aren’t contracted because no myosin heads are attached to actin filaments so there are no actin-myosin cross bridges). The actin filaments slide back to their relaxed position, which lengthens the sarcomere.

Question 50

What are the three ways ATP is generated for muscles?

Answer 50

1) Aerobic respiration
2) anaerobic respiration
3) ATP-creatine phosphate (ATP-CP) system

Question 51

How does aerobic respiration generate ATP?

Answer 51

Most ATP is generated via oxidative phosphorylation in the cell’s mitochondria. Aerobic respiration only works when there’s oxygen so it’s good for long periods of low-intensity exercise, eg a long walk.

Question 52

How does anaerobic respiration produce ATP?

Answer 52

ATP is made rapidly by glycolysis. The end product of glycolysis is pyruvate, which is converted into lactate by lactate fermentation. Lactate can quickly build up in the muscles and cause muscle fatigue. Anaerobic respiration is good for short periods of hard exercise eg a 400m sprint

Question 53

How does the ATP-CP system generate ATP?

Answer 53

ATP is made by phosphorylating ADP, and the phosphate group is taken from CP. the equation is
ADP + CP -> ATP + C

CP is stored inside cells and the ATP-CP system generates ATP very quickly. CP runs out after a few seconds so it’s used during short bursts of vigorous exercise eg a tennis serve. The ATP-CP system is anaerobic and it’s alactic

Question 54

What are three types of muscle in the body?

Answer 54

1) skeletal muscle
2) involuntary muscle
3) cardiac muscle

Question 55

What is the structure and function of skeletal muscle?

Answer 55

Skeletal muscle contraction is controlled consciously. it’s made up of many muscle fibres. These muscle fibres are multinucleate and can be many centimetres long.

Some muscle fibres contract very quickly-they’re used for speed and strength but fatigue easily. Some muscles fibres contract slowly and fatigue slowly- they’re used for endurance and posture.

Question 56

How does skeletal muscle look under a microscope?

Answer 56

There are cross striations (alternating dark and lighter pink stripes -A band and I bands). Many nuclei in each muscle fibre is stained blue.

Question 57

What is the structure and function of involuntary (smooth) muscle?

Answer 57

Involuntary muscle contraction is controlled unconsciously. Involuntary muscle is also called smooth muscle as it doesn’t have the striped appearance of voluntary muscle. It’s found in the walls of hollow internal organs eg the gut and blood vessels. Gut smooth muscles contract to move food along (peristalsis) and your blood smooth muscles contract to reduce flow of blood.

Each muscle fibre is uninucleate. The muscle fibres are spindle shaped with pointed ends,man’s are only about 0.2mm long
Muscle fibres contract slowly and don’t fatigue.

Question 58

What is the structure and function of cardiac muscle?

Answer 58

Cardiac muscle contracts on its own (it’s Myogenic). It’s found in the walls of your heart and it’s function is to pump blood around the body. It’s made of muscle fibres connected by intercalated discs, which have low electrical resistance so nerve impulses can pass easily between cells.

The muscle fibres are branched to allow nerve impulses to spread quickly through the whole muscle. Each cardiac muscle fibre is uninucleate. The muscle fibres are shakes like cyclindere and they’re about 0.1mm long. You can see some cross striations under a microscope but the pattern isn’t as strong as skeletal muscle. The muscle fibres contact rhythmically and don’t fatigue.

Question 59

What is a neuromuscular junction?

Answer 59

A neuromuscular junction is a synapse between a motor neurone and a muscle cell. They work in the same way as synapses between neurones. Neuromuscular junctions use the neurotransmitter ACh, which binds to receptors called nicotinic cholinergic receptors. ACHe stored in clefts on the post-synaptic membrane is used to break down ACh after use.

Question 60

What is the effect of chemicals on muscle contraction?

Answer 60

Sometimes a chemical eg a drug may block the release of the neurotransmitter or affect the way it binds to the receptors on the post synaptic membrane. This may prevent the action potential from being passed on to the muscle, so the muscle won’t contract.

Question 61

Example of a chemical that affects muscle contraction?

Answer 61

Pancuronium bromide is a non-depolarising, neuromuscular blocking drug. It completes against ACh for the nicotinic cholinergic receptors, binding to them so that the action of ACh is blocked and the muscle cell does not depolarise. It is used during surgery because it relaxes the muscles

The action of Pancuronium bromide can be reversed by inhibiting the action of ACHe, so that the concentration of ACh increases. This means it can out-compete the drug for available nicotinic cholinergic receptors.

Question 62

How can chemicals at neuromuscular junctions be fatal?

Answer 62

Chemicals that affect the action of neurotransmitters at neuromuscular junctions can be fatal if they affect the muscles involved in breathing eg the diaphragm and intercostal muscles. If they can’t contract, ventilation can’t take place and the organism can’t respire aerobically.

Question 63

What procedure detects electrical signals in muscles?

Answer 63

Electromyography. The reading generates an electromyogram.

Question 64

Procedure steps for electronyography?

Answer 64

1) attach two electrodes to place on the muscle that you want to record from. A third electrode goes on an inactive point eg the wrist to act as a control.

2) switch off any other electrical equipment that you don’t need as this generates noise, that interferes with the electrical signal from the muscle.

3) connect the electrodes to an amplifier and a computer.

4) keep the muscle relaxed. You should see a straight line on the electromyogram.

5) then contract the muscle by bending your arm. You should see spikes in the graph as motor units are activated to contract the muscle.

6) if you lift a weight, the amplitude (height) of the trace on the graph will increase, there are more electrical signals because more motor units are required to lift the weight.

7) if you continue to hold the weight, your muscle will begin to fatigue. This means that the muscle can no longer contract as forcefully as it could previously. On the electrogram you will see the amplitude of the trace increase further. This is because your brain is trying to activate more motor units to generate the force needed to hold the weight up.