Chapter 08: Homeostasis Of Blood Sugar & Gas Concentrations

Question 1

• What is glycogen?
• What are the 2 organs that secrete hormones involved in regulation of blood sugar?
• What is the role of the liver in regulating blood sugar concentration?
• Why is the liver known to have the 1st chance of absorbing nutrients from digested food?
• The hepatic portal vein carries glucose to liver where what 6 things occur?
• Distinguish between glycogenesis, glycogenolysis and gluconeogenesis.

Answer 1

-A substance made up of glucose molecules stored in muscle and liver cells.
-The pancreas and adrenal glands
-Converts glucose to glycogen for storage decreasing blood glucose level or release glycogen to glucose raising blood sugar.
-Liver’s blood supply comes from hepatic portal vein, which brings blood directly from stomach, spleen, pancreas and intestines.
1. Used by liver cells as an energy source.
2. Used by cells as an energy source.
3. Converted into glycogen for storage in the liver.
4. Converted into glycogen for storage in the muscles.
5. Converted to fat for storage.
6. Continues in blood to maintain blood-glucose level.
-Glucose molecules are chemically combined to form glycogen.
Breakdown of glycogen to glucose. Formation of glucose from fats or amino acids.

Question 2

• In what 4 ways does insulin decrease blood sugar levels?
• In what 2 ways does glucagon increase the blood sugar level?
• What’s the function of cortisol in relation to blood glucose levels?
• How are the levels of insulin and glucagon in the blood determined?

Answer 2

• Enables entry of glucose into cells, accelerates conversion of glucose into glycogen, stimulates conversion of glucose to fat stored in adipose tissue and Increases protein synthesis.
• Stimulates conversion of glycogen to glucose and fats and amino acids to glucose (gluconeogenesis).
• Increases glucose metabolism, converting glycogen to glucose in liver and amino acids to glucose (gluconeogenesis).
• Negative feedback systems. When blood sugar decreases alpha cells secrete glucagon, blood glucose levels rises, beta cells secrete insulin.

Question 3

-How does adrenaline and noradrenaline affect blood glucose levels?
-What is the normal range of glucose into the blood?
-The diaphragm and intercostals are stimulated by impulses from what spinal nerves?
-What is the respiratory centre?
-What are the 2 centres within the respiratory centre?
-What are the aortic and carotid bodies?
-Why does blood glucose rise after a meal?
Describe the following effects of concentration on breathing rate:
-O2
-Hydrogen ions (pH)
-CO2

Answer 3

-They prepare the body for increased physical activity by rising blood glucose levels, stimulating glycogen breakdown to glucose in the liver and the releasing into the blood.
-Around 5 millimoles per litre.
-Phrenic nerves and intercostal nerves respectively.
-Part of the brain, in medulla oblongata, that regulates breathing rate.
-Inspiratory and expiratory centres.
-Peripheral chemoreceptors located on aorta and carotid arteries that are sensitive to changes in oxygen concentration of blood plasma.
-Digestion breaks down carbs into glucose which are absorbed into the blood capillaries of the villi of the S.I.
-Decreased O2 increases BR (has to fall very low to cause an effect)
-Increased hydrogen ions decreases pH increasing B.R
(O2 + H2O -> carbonic acid -> hydrogen ions + bicarbonate ions).
-Increased CO2 increases increasing B.R.

Question 4

• What’s the function of voluntary control of breathing?
• Why is it dangerous to hyperventilate before swimming under water?
• Describe how the autonomic nervous system influences cardiac output at rest and exercise.
• Explain why we can’t voluntarily stop breathing undefinetly.

Answer 4

• Speech and a protective device enabling prevention of irritating gases and water from entering lungs.
• Removing lots of CO2 from blood prevents urge to breath as CO2 is low and O2 become so low and loses consciousness.
• ANS is split up into the SD and PD. Cardiac output is the balance between the Impulses from the sympathetic division which speeds up the H.R and impulses from the parasympathetic division which slow it down. At rest, parasympathetic devision dominate while during exercise sympathetic division dominate.
• Build up of CO2 in plasma will cause a reflex action, stimulating inspiratory centre to stimulate the inspiratory muscles.