Homeostasis of blood sugar and gas concentration

Question 1

What is the use of glucose?

Answer 1

Glucose is the source of energy for cells’ activities.

Energy is released from glucose molecules by cellular respiration.

Question 2

When is carbohydrates broken down into glucose?

Answer 2

digestion

Question 3

Where is glucose absorbed into the. blood?

Answer 3

Through walls of small intestine

Question 4

BGL after meal

Answer 4

After a meal, blood glucose concentration can rise sharply.
Homeostatic mechanisms then begin to operate to reduce the blood glucose concentration and maintain it at the normal level
Any excess glucose in the blood must be removed and stored ready for use in cellular activities between meals.

Question 5

Main organs involved in blood sugar regulation :

Answer 5

Pancreas
Liver
Adrenal glands

Question 6

what is Glycogenesis?

Answer 6

Formation of glycogen from other carbohydrates, esp

glucose

Question 7

What is Glycogenolysis?

Answer 7

Breakdown of glycogen into glucose

Question 8

What is Gluconeogenesis?

Answer 8

Conversion of fats or proteins into glucose

Question 9

What is Lipogenesis?

Answer 9

Conversion of glucose to fat or the synthesis of fatty acids from glucose

Question 10

What is the role of liver in BGL

Answer 10

Converts:
glucose into glycogen for storage

glycogen to glucose for release into the blood.

Question 11

Most of the liver’s blood supply comes through the:

Answer 11

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

Question 12

What happens to glucose in the liver?:

Answer 12

• Used by liver cells as an energy source.
• Converted into glycogen for storage (glycogenesis).
• Continue to circulate in the blood, available for body cells to absorb and use as a source of energy.
• Converted into fat for long-term storage (lipogenesis)

Question 13

Explain glycogenesis

Answer 13

Glucose molecules are chemically combined to form glycogen.

Stimulated by the pancreatic hormone insulin.

Glycogen are stored in the liver and muscle cells.

Question 14

Explain glycogenolysis

Answer 14

Occurs when the level of glucose in the blood drops below normal
Glycogen stored in the liver and muscle cells can be broken down into glucose.
Stimulated by another pancreatic hormone, glucagon

Question 15

What is the role of pancrease

Answer 15

The cells in the islets of Langerhans are of two types:
Alpha cells secrete glucagon
Beta cells secrete insulin

Question 16

What is the role of insulin?

Answer 16

Decreases in blood sugar levels in two main ways:
promotes transport of glucose from the blood into the cells
stimulates the conversion of glucose into glycogen

Also stimulates the conversion of glucose into fat in adipose tissue & increase in protein synthesis in some cells.

Question 17

What is the role of glucagon?

Answer 17

Causes an increase in blood sugar levels.
Stimulates:
Glycogenolysis – the conversion of glycogen into glucose in the liver.
Gluconeogenesis - the conversion of fats and amino acids into glucose in the liver.

Question 18

What is the role of adrenal glands?

Answer 18

Each gland is composed of two distinct parts:
outer part is called the cortex
inner part is the medulla

Question 19

What stimulates adrenal cortex and what it releases?

Answer 19

Stimulated by adrenocorticotropic hormone (ACTH) from anterior pituitary.
Secrete glucocorticoids (including cortisol):

Question 20

The effect of cortisol released by adrenal cortex:

Answer 20

Stimulate the conversion of glycogen into glucose
Stimulate amino acids removal from cells (mainly muscle cells) & conversion of amino acids into glucose in the liver
Promote the mobilization of fatty acids from adipose tissue. Lipolysis of storedlipidsin the adipose tissue to release free fatty acids
muscle cells shift from glucose to fatty acids for much of their metabolic energy.

Question 21

What does the adrenal medulla synthesis?

Answer 21

Synthesizes adrenaline and noradrenaline

Question 22

How does adrenaline and noradrenaline effect the blood glucose level ?

Answer 22

Stimulates breakdown of glycogen into glucose in the liver

Stimulates the production of lactic acid from glycogen in muscle cells. Lactic acid can then be used by the liver to manufacture glucose.

Question 23

What is the function of circulatory system ?

Answer 23

carries oxygen from the lungs  the cells where it is used

takes away the carbon dioxide produced by cells  the lungs for excretion

Question 24

Groups of cells that are sensitive to changes in the concentration of oxygen, carbon dioxide, & H+ in the blood plasma:

Answer 24

Central chemoreceptors in the medulla oblongata
Peripheral chemoreceptors:
Aortic bodies
Carotid bodies

Question 25

What is the modulator of the circulatory system ?

Answer 25

the respiratory centre located in the medulla oblongata

Question 26

What is the effector of the circulatory system ?

Answer 26

Effectors: Diaphragm muscles that cause air to move in and out of the lungs separates the thorax from the abdomen Intercostal muscles muscles between the ribs

Question 27

What are stimulation in the respiratory system ?

Answer 27

Require stimulation from nerve impulses to initiate contraction Diaphragm is stimulated by impulses from the phrenic nerve Intercostal muscles are stimulated by impulses from the intercostal nerves

Question 28

What type of nerves of the phrenic and intercostal nerves?

Answer 28

These spinal nerves have their origin in the spinal cord at the level of the neck and thorax If these nerves are injured = complete paralysis of the muscles that ventilate the lungs Death inevitably follows unless some form of artificial respiration is rapidly applied

Question 29

How does the oxygen concentration affects the respiratory system?

Answer 29

If the concentration of oxygen falls below normal while other factors are held constant, the breathing depth & rate increases. However, within the normal range of blood oxygen concentration, the effect on breathing rate is only slight. The concentration has to fall to very low levels before it has a major stimulatory effect.

Question 30

How does the carbon dioxide concentration affects the respiratory system?

Answer 30

Major factor in the regulation of breathing rate Small increase in the concentration of CO2 is enough to cause a marked increase in the depth & rate of breathing

Question 31

How does the hydrogen concentration affects the respiratory system?

Answer 31

Concentration of CO2 in the blood plasma affects the concentration of H+ ions. H+ concentration of the blood increases, the pH decreases, causing an increase in the breathing depth & rate

Question 32

Explain the voluntary control of breathing ?

Answer 32

Humans are able to voluntarily control their rate and depth of breathing & can stop breathing for a limited period Voluntary control : connections from the cerebral cortex to descending tracts in the spinal cord. Bypasses the respiratory centre in the medulla oblongata Protective device: enables us to prevent irritating gases and water from entering the lungs Build-up of CO2 in the plasma > eventually forced to take a breath

Question 33

Explain hyperventilation

Answer 33

Rapid, deep breathing can provide more O2 than required and remove more CO2 than necessary Can occur voluntarily or stimulated by physical stress or emotional stress Usually corrects itself because of reduction in CO2 concentration

Question 34

Why is hyperventilating dangerous?

Answer 34

Hyperventilating before swimming under water - dangerous! Does allow a person to stay under water longer, but this is not because of extra O2 in the blood – it is due to the loss of CO2 Individual loses consciousness from lack of O2 to the brain before feeling the urge to breathe

Question 35

What does exercise affects the breathing rate and depth ?

Answer 35

Increases both the rate of breathing and the depth of breathing Contracting muscle cells require large amounts of O2 and produce large amounts of CO2  Increased demand for gas exchange

Question 36

What is Heart rate?

Answer 36

number of times the heart beats per minute

Question 37

What is Stroke volume ?

Answer 37

volume of blood forced from the heart with each contraction

Question 38

What is Blood pressure ?

Answer 38

the force with which the blood presses on the walls of the blood vessels.

Question 39

What is cardiac output?

Answer 39

– as cardiac output increases, blood pressure increases | - cardiac output - heart rate x stroke volume

Question 40

What is diameter of blood vessels ?

Answer 40

constriction of blood vessels increases pressure and dilation decreases blood pressure.

Question 41

What is the function of sinoatrial node ?

Answer 41

Sinoatrial node (SAN) described as the ‘pacemaker’ responsible for the rhythmical contractions of the heart Can stimulate heartbeat on its own but its activity is influenced by the autonomic nervous system

Question 42

Describe the process of heart beats

Answer 42

When the heart beats, the following occur: The SAN sends out nerve impulses that spread through the atria. The stimulus reaches the Atrioventricular Node (AVN). At about this time, contraction of the muscle of the atrium begins. Stimulation of the AVN causes it to send out its own impulses. These travel down the fibres in the septum between the ventricles. The impulses then spread through the muscles of the ventricles. Atrial contraction is now complete and ventricular contraction begins.

Question 43

Changes to blood flow during exercise

Answer 43

Large increase in blood flow is required by contracting muscles to ensure an adequate supply of O2 and nutrients to remove CO2 and heat produced To ensure that blood supply to the muscles is increased: blood vessels in internal organs such as the alimentary canal constrict. dilation of blood vessels in the muscles.

Question 44

The effect behavior of exercising

Answer 44

When a person is about to begin exercising, there is an anticipatory response brought about by the autonomic nervous system & by release of the hormone adrenaline Blood glucose rises due to mental stress Heart rate and stroke volume increase

Question 45

When we exercise:

Answer 45

breathing rate and depth will increase cardiac output will rise further blood glucose will continue to be at a high level Increase in blood supply to skeletal muscles