Chapter 8 - Homeostasis Of Blood Sugar And Gas Concentrations

Question 1

What is the waste product of cellular respiration?

Answer 1

Carbon dioxide

Question 2

What are the muscles that control the movement of the lungs?

Answer 2

The diaphragm and intercostal muscles

Question 3

What nerves stimulate the movement of the diaphragm and intercostal muscles?

Answer 3

Diaphragm - phrenic nerve

Intercostal muscles - intercostal nerves

Question 4

What happens if the nerves responsible to breathing are injured?

Answer 4

The result is complete paralysis of the muscles that ventilate the lungs. Death inevitably follows unless some sort of artificial respiration is rapidly applied.

Question 5

Where is the respiratory centre in the brain?

Answer 5

The medulla oblongata

Question 6

What are the two regions of the respiratory centre that work together?

Answer 6

• one that controls expiration (breathing out)
• one that controls inspiration (breathing in)
  To coordinate breathing, messages need to pass back and fourth between neurons in these two regions.

Question 7

What does carbon dioxide become when it dissolves in water?

Answer 7

Carbonic acid (H2CO3), which can be further broken down into hydrogen ions (H+) And bicarbonate ions (HCO3-)

Question 8

What are the groups of chermoreceptors that are sensitive to the concentration of oxygen in the blood? (And where are they found?)

Answer 8

Aortic and carotid bodies and are found in the walls of the aorta and carotid arteries.

Question 9

What happens if there is a large decrease in oxygen levels within the blood?

Answer 9

Chemoreceptors are stimulated and nerve impulses are transmitted to the respiratory centre. These never impulses stimulate the transmission of messages to the diaphragm and intercostal muscles and so the breathing rate increases.

Question 10

What happens if there is an increase of carbon dioxide and hydrogen in the blood?

Answer 10

Chemoreceptors transmit nerve impulses to the respiratory centre, resulting in an increase in breathing rate.

Question 11

Where are the chemoreceptors most sensitive to change found and what are they responsible for?

Answer 11

In the medulla oblongata and are responsible for 70-80% of the increase in breathing rate as a result from the increase of carbon dioxide in the blood. However, this response takes several minutes.

Question 12

As hydrogen concentration of the blood increases, what decreases?

Answer 12

The pH of the blood.

Question 13

Draw a diagram illustrating what happens during the increase of carbon dioxide in the blood.

Answer 13

• decrease in breathing rate
• Increase in concentration of Co2
• decrease in pH
• chemoreceptors in medulla oblongata
• chemoreceptors in aortic and carotid bodies
• Respiratory centre
• increased breathing rate
• decrease in concentration of Co2
• negative feedback

Question 14

What is hyperventilation?

Answer 14

Rapid deep breathing caused by physical stress such as severe pain or emotional stress such as extreme anxiety.

Question 15

What happens during heavy exercise?

Answer 15

The volume of air going into and out of the lungs each minute may increase ten, to twenty fold.

Question 16

What is the difference between heart rate and stroke volume?

Answer 16

Heart rate is the number of times the heart beats per minute, while stroke volume is the volume of blood forced from the heart with each contraction. A combination of both factors determines the cardiac output.

Question 17

What is cardiac output and what is the formula?

Answer 17

Cardiac output is the amount of blood leaving the heart every minute. 
Cardiac output (mL/min) = heart rate (beats/min) x stroke volume (mL)

Question 18

What blood pressure and what does it depend on?

Answer 18

Blood pressure is the force in which the blood presses on the walls of the blood vessels.
It depends on the cardiac output - as cardiac output increases, blood pressure increases.
It depends on the diameter of blood vessels - constriction of blood vessels increases pressure and dilation decreases blood pressure.

Question 19

What are the bundles of specialised cells controlling the hearts activity?

Answer 19

The sinoatrial node (SA node)

The Atrioventricular node (AV node).

Question 20

What is the SA node responsible for?

Answer 20

The SA node is often described as the ‘pacemaker’ as it is responsible for the rhythmical contractions of the heart. It initiates each heartbeat with an impulse that spreads out over both atria, causing them to contract and eventually reaches the AV node.

Question 21

Where is the SA node situated?

Answer 21

It is located in the wall of the right atrium just below the opening of the superior vena cava

Question 22

Where is the AV node situated?

Answer 22

In between the two atria near the atrioventricular valves.

Question 23

What is the AV node responsible for?

Answer 23

Conducts fibres that pass through the septum that seperate the left and the right ventricles of the heart. These fibres then divide into branches, one branch going down each side of the septum. These branches divide into a network of fine fibres.

Question 24

What is the sequence of a heart beat?

Answer 24

1. The SA node sends our nerve impulses that spread throughout the atria.
2. The stimulus reaches the AV node. At about this time contractions of the muscle of the atrium begin.
3. Stimulation of the AV node causes it to send out it’s own impulses. These travel down the fibres in the septum between the ventricles.
4. The impulses then spread through the muscles of the ventricles atrial contraction is now complete and ventricular contraction begins.

Question 25

What controls the SA and AV nodes?

Answer 25

Nerve impulses from the medulla oblongata.

Question 26

What is the region of the medulla oblongata concerned with the heart?

Answer 26

The cardiac centre or cardiovascular regulating centre

Question 27

What parts of the autonomic division are activated during rest and exercise?

Answer 27

At rest, the parasympathetic activity is dominant. During exercise, the activity of the sympathetic system is dominant.

Question 28

What muscles require the most blood supply during exercise and how is this achieved?

Answer 28

• the Skeletal muscles activated require the most blood during exercise.
  To ensure this, internal muscles such as the muscles of the alimentary canal constrict and the blood vessels in muscles dilate.

Question 29

What is the anticipatory response that occurs before a person starts exercising?

Answer 29

The anticipatory response brought about by the autonomic nervous system is the release of adrenaline. Heart rate and stroke volume increase and there is an increase in the blood flow to skeletal muscles.

Question 30

Explain the behavioural effects of your body when a race is about to begin (eg anticipation, heart rate, blood pressure etc).

Answer 30

• mental stress will cause your blood glucose levels to rise and your heart rate and blood pressure will increase.
• once in the race, breathing rate and depth will increase, cardiac output will rise further and glucose will continue to rise. There will be an increase in blood supply to working muscles and a decreasing supply to internal organs.

Question 31

What is the form of sugar in the blood?

Answer 31

Glucose

Question 32

What is glucose important for?

Answer 32

It is a source of energy for all cell activities.

Question 33

What is the formula for cellular respiration?

Answer 33

Glucose + oxygen = carbon dioxide + water + energy

Question 34

What is glucose stored as?

Answer 34

Glucose is stored as glycogen, a molecule made of long chains of glucose molecules.

Question 35

What are the main organs that store glucose?

Answer 35

The liver and muscle cells.

Question 36

What glands secret hormones that affect the level of glucose in the blood?

Answer 36

The pancreas and adrenal glands

Question 37

What is a glucometer?

Answer 37

A blood glucose meter used to measure the level of glucose in the blood.

Question 38

What does majority of the liver’s blood supply come through?

Answer 38

The hepatic portal vein, which brings blood directly from the stomach, spleen, pancreas and small and large intestines.
The liver has the first chance to absorb nutrients from digested food.

Question 39

What are the four main roles of the liver in the regulation of glucose in the blood?

Answer 39

• glucose may be removed from the blood by the liver to provide energy for liver functioning.
• it may be removed by the liver and/or muscles and converted into glycogen for storage.
• it may continue to circulate in the blood, available for body cells to absorb and use as a source of energy.
• glucose in excess of that required to maintain both normal blood sugar levels and tissue glycogen level in converted into fat for long term storage.

Aka

• used by liver cells as energy source
• converted into glycogen and stored in the liver
• used by cells as an energy source
• stored in muscles as glycogen
• converted to fat for storage

Question 40

How much glycogen can the body store?

Answer 40

About 500g of glycogen ; about 100g is stored in the liver and the remainder in skeletal muscles cells.

Question 41

What are the differences between glycogenesis and glycogenolysis?

Answer 41

Glycogenesis

• stimulated by insulin
• converts glucose into glycogen

Glycogenolysis

• stimulated by glucagon
• converts glycogen into glucose

Question 42

What happens if the level of glucose in the blood drops to consumption?

Answer 42

The glycogen in the liver and muscle cells can be broken down into glucose

Question 43

What are the clusters of hormone secreting cells in the pancreas called?

Answer 43

Islets of langerhans

Question 44

What are the two types of islets of langerhans?

Answer 44

Alpha cells (secrete glucagon)
Beta cells (secrete insulin)

Question 45

How does insulin cause a decrease in blood sugar levels? (Hint 4 main ways)

Answer 45

1. Enables entry of glucose into cells
2. Promotes glycogenesis
3. Stimulates the conversion of glucose into fat in adipose tissue (fat storage tissue).
4. Promotes protein synthesis

Question 46

How does glucagon cause an increase in blood sugar levels? (Hint two main ways)

Answer 46

• it converts liver glycogen into glucose (glycogenolysis)

- it promotes glucogenogenesis

Question 47

What are the hormones secreted from the adrenal glands that are associated with regulation of blood sugar?

Answer 47

Glucocorticoids, the best known of which is cortisol.

Question 48

What are the main roles of glucocorticoids?

Answer 48

They regulate carbohydrate metabolism by making sure enough energy is provided to the cells. In doing this they stimulate glycogenolysis and increase the rate at which amino acids are removed from cells and transported to the liver.

Question 49

What is the role of the adrenal cortex?

Answer 49

It produces glucocorticoids (cortisol) in which

1. Stimulates conversion of glycogen into glucose in the liver.
2. Stimulates protein breakdown in muscles and conversion of amino acids into glucose in the liver.

Question 50

What is the role of the adrenal medulla?

Answer 50

It produces adrenaline and noradrenaline in which

1. Stimulates breakdown of glycogen in liver and release of glucose into blood.

Question 51

What is the normal level of glucose in the blood?

Answer 51

between 4 and 6 millimoles per litre.