Exercise and Feedback Mechanisms (7.8-7.9, 7.11–7.16)

Question 1

Describe the process of heart contraction due to its myogenic nature?

Answer 1

1. The Sinoatrial node (SAN) sends out of wave of electrical activity to the atrial walls.
2. The left and right atria contract at the same time.
3. The waves of electrical activity are then transferred from the SAN to the atrioventricular node (AVN).
4. The AVN passes on the electrical activity to the Bundles of His after a slight delay.
5. The Bundles of His are responsible for conducting the waves of electrical activity to the muscle fibres in the ventricle walls called the purkyne fibres.
6. The purkyne fibres carry the waves of electrical activity into the muscular walls of the left and right ventricle causing them to contract simultaneously bottom up.

Question 2

Where is the SAN?

Answer 2

Wall of right atrium

Question 3

What prevents the electrical activity from being passed directly from the atria to the ventricles?

Answer 3

A band of non conducting collagen tissue.

Question 4

What is tachycardia?

Answer 4

Heart beating too fast as the heart isn’t pumping blood efficiently.

Question 5

What is bradycardia?

Answer 5

Heartbeat is too slow.

Question 6

What is an ectopic heartbeat?

Answer 6

An ‘extra’ heartbeat, caused by an earlier contraction of the atria. Also can be caused by early contraction of the ventricles.

Question 7

What is fibrillation?

Answer 7

Really irregular heartbeat.

Question 8

Where are the ventilation centres?

Answer 8

The medulla oblongata

Question 9

What are the two ventilation centres?

Answer 9

The inspiratory and expiratory centres.

Question 10

How does the medulla oblongata control the rate of breathing?

Answer 10

1. The inspiratory centre in the medulla oblongata sends impulses to the intercostal and diaphragm muscles to make them contract. And to the expiratory centre which inhibit action.
2. This increases the volume of the lungs, which lowers the pressure in the lungs.
3. Air enters the lungs due to the pressure difference between the lungs and air outside.
4. As the lungs inflate, stretch receptors in the lungs are stimulated. Sending nerve impulses back to the medulla oblongata. Inhibiting action of the inspiratory centre.
5. The expiratory centre then sends nerve impulses to the diaphragm and intercostal muscles to relax. This causes the lungs to deflate. As the lungs deflate the stretch receptors become inactive. The inspiratory centre is no longer inhibited and the cycle starts again.

Question 11

How does a change in pH increase breathing rate?

Answer 11

1. During exercise, the level of CO2 increases. This decreases the pH in the blood.
2. There are chemoreceptors in the medulla oblongata, aortic bodies and carotid bodies that are sensitive to changes in blood ph.
3. If the chemoreceptors detect a decrease in blood pH they send nerve impulses to the intercostal muscles and diaphragm. Increasing the rate and depth of breathing.
4. This causes gaseous exchange to speed up.

Question 12

What is ventilation?

Answer 12

Volume of air breathed in or out in a period of time.

Question 13

Why does ventilation increase during exercise?

Answer 13

Because breathing rate and depth increase.

Question 14

What does the sympathetic nervous system do?

Answer 14

Gets the body ready for action. Its the fight or flight system. Increases the heart rate during exercise.

Question 15

What does the parasympathetic nervous system do?

Answer 15

Calms the body down. Rest and digest system, helps to decrease the heart rate after exercise.

Question 16

How does the the heart respond to high blood pressure?

Answer 16

Baroreceptors detect high blood pressure.

Impulses are sent to the cardiovascular control centre, which sends impulses along parasympathetic neurones. These secrete acetylcholine which binds to receptors on the SAN.

The SAN fires impulses less frequently to slow heart rate and reduce blood pressure back to normal.

Question 17

How does the heart respond when the body detects low blood pressure?

Answer 17

Baroreceptors detect low blood pressure.

Impulses are sent to the cardiovascular control centre, which sends impulses along sympathetic neurones. These secrete noradrenaline, which binds to receptors on the SAN.

The SAN fires impulses more frequently to increase heart rate and increase blood pressure back to normal.

Question 18

How does the heart respond to high blood O2, low CO2 or high pH levels?

Answer 18

Chemoreceptors detect chemical changes in the blood

Impulses are sent to the cardiovascular control centre, which sends impulses along parasympathetic neurones. These secrete acetylcholine, which binds to receptors on the SAN.

The SAN fires impulses less frequently to decrease heart rate and return O2, CO2 and pH levels back to normal.

Question 19

How does the heart respond to low blood O2, high CO2 or low pH levels?

Answer 19

Chemoreceptors detect chemical changes in the blood.

Impulses are sent to the cardiovascular control centre, which sends impulses along sympathetic neurones. These secrete noradrenaline, which binds to receptors on the SAN.

SAN fires impulses more frequently to increase heart rate and return O2, CO2 and pH levels back to normal.

Question 20

What is the equation for cardiac output?

Answer 20

Cardiac output (cm3 min-1) = heart rate (beats per min) x stroke volume (cm3)

Question 21

Tidal volume?

Answer 21

The volume of air in each breath

Question 22

Breathing rate?

Answer 22

How many breathes is taken

Question 23

respiratory minute ventilation?

Answer 23

respiratory minute ventilation = tidal volume x breathing rate

Question 24

What is homeostasis?

Answer 24

Maintenance of a stable internal environment. Keeping control systems between narrow limits.

Question 25

What is negative feedback?

Answer 25

Mechanism that restores the change to its normal level.

Question 26

What is positive feedback mechanism?

Answer 26

Effectors respond to further increase the level away from the normal level.

Question 27

What are 3 mechanisms to reduce body temperature?

Answer 27

1. Sweating- More sweat is secreted from sweat glands when it evaporates it takes heat from the body.
2. Hairs lie flat- mammals have a layer of hair that insulates and so when they lie flat heat can be lost more easily.
3. Vasodilation- Arterioles near the surface of the membrane dilate. More blood flows through the capillaries so more heat is lost by radiation.

Question 28

What are 5 mechanisms to increase body temperature?

Answer 28

1. Shivering- when its cold, muscles contract in spasms. This makes the body shiver and more heat is produced from increases cell respiration.
2. Much less sweat- less sweat means less heat loss.
3. Hairs stand up- erector pili muscles contract which makes the hairs stand up and trap more air.
4. Vasoconstriction- Arterioles near the surface of the skin constrict so less blood flows through the capillaries in the surface layers of the dermis.
5. Hormones- the body releases adrenaline and thyroxine. These increase metabolism and so more heat is produced.

Question 29

What maintains the temperature in the body?

Answer 29

Hypothalamus

Question 30

How does the body regulate temperatures back to normal?

Answer 30

Thermoreceptors detect temperatures are too…high or low

Hypothalamus sends signals to effectors

eg hairs lie flat or hairs stick up

More heat is produced and conserved in the body or more heat is lost and less heat is preserved in the body.

Question 31

How do steriod hormones work inside cells?

Answer 31

1. Normal body temperature, the thyroid hormone receptor binds to DNA at the start of a gene.
2. Decreases the transcription of a gene coding for a protein that increases metabolic rate.
3. At cold temperatures thyroxine is released which binds to the thyroid hormone receptor causing it to act as an activators.
4. Transcription rate increases, producing more protein. The protein increases the metabolic rate, causing an increase in body temperature.

Question 32

How do peptide hormones work from the cell membrane?

Answer 32

1. They bind to receptors in the cell membrane, which activate messenger molecules in the cytoplasm of the cell.
2. These messenger molecules activate enzymes called protein kinases, which triggers a cascade inside the cell.
3. During the cascade, transcription factors can be activated, these then affect the transcription of genes in the cell nucleus.

Question 33

What is keyhole surgery?

Answer 33

Way of doing surgery without making a large incision.

They insert a tiny video camera and specialised medical instruments.

Question 34

What are some of the advantages of key hole surgery?

Answer 34

Lose less blood and less scarring

Minimally invasive so recover quicker.

Less pain.

Question 35

What are the disadvantages of exercising too much?

Answer 35

Wear and tear on joints and suppression of the immune system.

Question 36

What are the disadvantages of exercising too little?

Answer 36

Increased risk of obesity, CVD and diabetes.

Question 37

Give the argument against using performance enhancing drugs

Answer 37

1. Illegal
2. Unfair
3. Health risks
4. May not be fully informed of risks

Question 38

Give the arguments for performance enhancing drugs

Answer 38

1. Own decision
2. Drugs help overcome inequalities of drug free sport eg facilities equipment and coaches
3. Only be able to compete at higher level if using performance enhancing drugs.