Module 5.3 - Animal responses

Question 1

What are the three types of muscle?

Answer 1

Skeletal, cardiac and smooth.

Question 2

Describe skeletal muscle?

Answer 2

> Cylindrical bundles of muscle fibres.
Multinucleate cells
Obvious striations

Question 3

Describe cardiac muscle?

Answer 3

> Striated and branched.
Has intercalated discs (discs that connect the cells to help it work as a single functional organ).
Gap junctions (tunnels between cells)
Myogenic, meaning contractions are produced spontaneously, without requiring stimulation from nerve cells.

Question 4

Describe smooth muscle?

Answer 4

> Cells have a tapered/spindle shape (not in fibres).
Two layers: inner layer arranged in a circular fashion to allow segmentation. Outer layer is longitudinal, producing waves of movement.

Question 5

What is the plasma membrane of a muscle fibre called?

Answer 5

Sarcolemma

Question 6

What is the cytoplasm of a muscle fibre called?

Answer 6

Sarcoplasm.

Question 7

What are myofibrils?

Answer 7

Any of the elongated contractile threads found in striated muscle cells.

Question 8

What is a sarcomere?

Answer 8

The basic unit of striated muscle tissue: the repeating unit between two Z lines/discs.

Question 9

What are gap functions and what are they for?

Answer 9

Small tunnels that connect cells, facilitating the passing of molecules, ions and electrical impulses between cells.

Question 10

Name the thick and thin filaments in muscle fibres?

Answer 10

Thin = actin
Thick = myosin.

Question 11

What is the neuromuscular junction?

Answer 11

Point of contact between a motor neuron and a muscle cell.

Question 12

What does a motor unit refer to?

Answer 12

All of the muscle fibres innervated by a single motor neuron.

Question 13

What is the sarcoplasmic reticulum?

Answer 13

Muscle cell’s endoplasmic reticulum, used to store calcium ions.

Question 14

Describe the location of the Z discs, M line, I band and A band?

Answer 14

Z discs - between sarcomeres.
M line - Middle of sarcomere.
I band - From end of myosin on one sarcomere, to the end of myosin on the next one.
A band - spans the length of the myosin within one sarcomere.

Question 15

Describe what the peripheral system splits into?

Answer 15

Peripheral system -> Somatic nervous system

->Autonomic nervous system -> Sympathetic or parasympathetic.

Question 16

What does the somatic nervous system control?

Answer 16

Controls conscious activities.

Question 17

What does the autonomic nervous system control?

Answer 17

Controls unconscious activities (e.g. digestion).

Question 18

What is the sympathetic nervous system’s function?

Answer 18

Gets the body ready for action, it’s the ‘fight or flight’ system. Sympathetic neurons release the neurotransmitter noradrenaline

Question 19

What is the parasympathetic nervous system’s function?

Answer 19

Calms the body down. It’s the ‘rest and digest’ system. Parasympathetic neurons release the neurotransmitter actylcholine.

Question 20

What does the peripheral nervous system consist of?

Answer 20

Made up of the neurons that connect the CNS to the rest of the body.

Question 21

Where is the hypothalamus in the brain and what is its function?

Answer 21

> The hypothalamus is found just beneath the middle part of the brain.
Its function is to automatically maintain body temp. at the normal level. It produces hormones that control the pituitary gland.

Question 22

Where is the pituitary gland in the brain and what is its function?

Answer 22

> Found beneath the hypothalamus.
Controlled by the hypothalamus. It releases hormones and stimulates other glands (e.g. adrenal glands to release their hormones).

Question 23

Where is the medulla oblongata in the brain and what is its function?

Answer 23

> At the base of the brain, at the top of the spinal cord.

>Automatically controls breathing and heart rate.

Question 24

Where is the cerebellum in the brain and what is its function?

Answer 24

> Underneath the cerebrum and also has a folded cortex.

>Important for muscle coordination, posture and coordination of balance.

Question 25

Where is the cerebrum in the brain and what is its function?

Answer 25

> The cerebrum is the largest part of the brain and is divided into the two halves called cerebral hemispheres.
Involved in vision, hearing, learning and thinking.

Question 26

What is the simple structure of the cerebrum?

Answer 26

The cerebrum has a thin outer layer called the cerebral cortex, which is highly folded.

Question 27

Why in a reflex does the body respond to a stimulus without making a conscious decision?

Answer 27

The pathway of communication doesn’t involve the conscious parts of the brain.

Question 28

Describe the blinking reflex when someone touches your eye?

Answer 28

> Sensory nerve endings in the cornea are stimulated by touch.
A nerve impulse is sent along the sensory neuron to a relay neuron in the CNS.
The impulse is then passed from the relay neuron to motor neurons.
The motor neurons send impulses to the effectors - the orbicularis oculi muscles that move your eyelids. These muscles contract causing your eyelids to close quickly and prevent your eye from being damaged.

Question 29

How does your body prevent you from falling over after landing a jump and describe how it works?

Answer 29

The knee-jerk reflex works to quickly straighten your leg if the body detects your quadriceps are suddenly stretched helping to maintain posture and balance
>Stretch receptors in the quadriceps muscle detect that the muscle is being stretched.
>A nerve impulse is passed along a sensory neuron, which communicates directly with a motor neuron in the spinal cord (no relay neuron involved).
>The motor neuron carries the nerve impulse to the effector (the quadriceps muscle) causing it to contract so the lower leg moves forward quickly.

Question 30

What does the ‘fight or flight’ response activate?

Answer 30

Nerve impulses from the sensory neurons arrive at the hypothalamus activating both the hormonal and sympathetic nervous system :
>The pituitary gland is stimulated to release a hormone called ACTH, causing the cortex of the adrenal gland to release steroidal hormones.
>The sympathetic nervous system is activated, triggering the release of adrenaline from the medulla region .

Question 31

What are the effects of adrenaline on the body?

Answer 31

> Heart rate increases.
Muscles around the bronchioles relax - breathing is deeper.
Glycogen is converted into glucose - more glucose available for muscles to respire.
Muscles in the arterioles supplying the 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 the the vital organs.
Erector pili muscles in the skin contract - making hairs stand up on end so the animal looks bigger.

Question 32

Describe how heart rate is controlled by the nervous system?

Answer 32

> The SAN generates electrical impulses that causes the cardiac muscles to contract. The rate is unconsciously controlled by the medulla in the brain. Electrical impulses from receptors are sent to the medulla along sensory neurons and the medulla processes the info and sends impulses to the SAN along sensory neurons.
Animals need to alter their heart rate to respond to internal stimuli which are detected by pressure or chemical receptors.

Question 33

Give some examples of pressure/chemical receptors that detect changes in heart rate?

Answer 33

> Pressure receptors called baroreceptors in the aorta and the vena cava, stimulated by high and low blood pressure.
Chemical receptors called chemoreceptors in the aorta, the carotid artery and in the medulla. They monitor the oxygen / CO2/pH level in the blood.

Question 34

What response will high blood pressure cause?

Answer 34

> Baroreceptors detect high blood pressure.
Impulses are sent to the medulla.
This sends impulses along the vagus nerve.
This secretes acetylcholine, which binds to receptors on the SAN.
The effector is the cardiac muscles and causes the heart rate to slow down and reduce blood pressure back to normal.

Question 35

What hormone is secreted from the accelerator nerve when there is low blood pressure?

Answer 35

Noradrenaline.

Question 36

What response will low blood O2/high CO2/low pH levels cause?

Answer 36

> Chemoreceptors detect chemical changes in the blood.
Impulses are sent to the medulla.
This sends impulses along the accelerator nerve.
This secretes noradrenaline, which binds to receptors on the SAN.
The effector is cardicac muscle and causes the heart rate to increase and return O2/CO2 and pH levels back to normal.

Question 37

How does the hormonal system help to control heart rate?

Answer 37

Releases adrenaline (when the ‘fight or flight’ response is activated). Adrenaline binds to specific receptors in the heart. This causes the cardiac muscle to contract more frequently and with more force, so heart rate increases and the heart pumps more blood.

Question 38

Describe the steps of the t-test for analysing the effect of excercise on heart rate?

Answer 38

> Need 2 sets of data - one group of people (e.g. 8) receiving 6 months of endurance training and another group that didn’t.

1) Measure the resting heart rates of both groups.
2) Identify the null hypothesis (that there is no significant difference between the 2 sets of data).
3) Calculate the mean and standard deviation for each data set.
4) Use the formula above to calculate t
5) Calculate the degrees of freedom by doing (n1 + n2) - 2
6) Look up the values of t in a table of critical values. If the value obtained from the t-test is greater than the critical value at a probability of 5% or less. Then you can be 95% confident that the difference is significant and not due to chance, you can reject the null hypothesis.

Question 39

Describe the sliding filament theory?

Answer 39

> Myosin and actin filaments slide over one another to make the sarcomeres contract- the myofilaments themselves don’t contract.
The simultaneous contraction of lots of sarcomeres means the myofibrils and muscle fibres contract.
Sarcomeres return to their original length and the muscle relaxes.

Question 40

Describe what is happening in a resting (unstimulated) cell in terms of the myofilaments?

Answer 40

The actin-myosin binding site is blocked by tropomyosin, which is held in place by troponin.
>Myofilaments can’t slide past each other because the myosin heads can’t bind to the actin-myosin binding site on the actin filaments.

Question 41

Describe the different structures of actin and myosin filaments?

Answer 41

> Myosin filaments have globular heads that are hinge, so they can move back and forth. Each myosin head has a binding site for actin and a binding site for ATP.
Actin filaments have binding sites for myosin heads, called actin-myosin binding sites.
2 other proteins called tropomyosin and troponin are found between actin filaments. These proteins are attached to each other and they help myofilaments move past each other.

Question 42

What happens when an action potential from a motor neurone stimulates a muscle cell?

Answer 42

1) It depolarises the sarcolemma and the depolarisation spreads out down the T-tubules to the sarcoplasmic reticulum which releases stored Ca2+ into the sarcoplasm.
2) Calcium ions bind to troponin causing it to change shape pulling the attached tropomyosin out of the actin-myosin binding site on the actin filament.
3) This exposes the binding site, which allows the myosin head to bind. This is called an actin-myosin cross bridge.
4) Ca2+ activate the enzyme ATPase which breaks down ATP to provide the energy needed for muscle contraction.
5) The energy released from ATP moves the myosin head which pulls the actin filament along in a kind of rowing action.
6) ATP also provides the energy to break the actin-myosin cross bridge, so the myosin head detaches from the actin filament after it’s moved.
7) The myosin head then reattaches to a different binding site further along the actin filament and a new actin-myosin cross bridge is formed and the cycle is repeated.
8) Many cross bridges form and break very rapidly, pulling the actin filament along - shortening the sarcomere causing the muscle to contract.
9) This cycle will continue as long as Ca2+ ions are present and bound to troponin.

Question 43

What happens when excitation stops in the muscle cell?

Answer 43

1) Ca2+ leave their binding sites on the troponin molecules and are moved by active transport back into the sarcoplasmic reticulum.
2) 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.
3) Muscles aren’t contracted because no myosin heads are attached to actin filaments (no actin-myosin cross bridges).
4) The actin filaments slide back to their relaxed position, which lengthens the sarcomere.

Question 44

How is most ATP generated?

Answer 44

Aerobic respiration - Oxidative phosphorylation in the cell’s mitochondria.
>Only works when there is oxygen available so it’s good for long periods of low-intensity exercise.

Question 45

Describe how ATP is produced via anaerobic respiration?

Answer 45

> ATP is made rapidly by glycolysis
The end-product of glycolysis is pyruvate, which is converted to 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.

Question 46

Describe the ATP-Creatine Phosphate System?

Answer 46

> ATP is made by phosphorylating ADP - adding a phosphate group taken from creatine phosphate (CP)
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.
The ATP-CP system is anaerobic (doesn’t need oxygen) and it’s alactic (doesn’t form any lactate).