Download Chapter 8 Homeostasis of blood sugar, gas concentrations and

Year 12 Human Biology
Unit 4 – Homeostasis
Week 6 2016 - Solutions
Chapter 8 Homeostasis of blood sugar, gas concentrations and blood pressure
Review Questions:
1.
What is livers role in regulating BGL?
Liver converts glucose to glycogen or the reverse process of glycogen to glucose. R will either
take up glucose from the blood or release it into the blood.
2.
Distinguish between glycogenesis, glycogenolysis & gluconeogenesis
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3.
a.
Glycogenesis = where glucose is converted to glycogen.
Glycogenolysis = the conversion of glycogen to glucose.
Gluconeogenesis = the production of new sugar molecules from fats and amino acids.
Gland associated with the hormones insulin and glucagon?
The islets of Langerhans of the pancreas.
b.
How insulin & glucagon regulate BGL
When the glucose levels rise the beta cells in the islets of Langerhans secrete insulin which
lowers the blood glucose by three ways – allowing entry of glucose into the cells, glycogenesis
where the glucose is converted to glycogen and lipogenesis where the excess glucose is stored
as fat in the adipose tissue.
The opposite happens when the blood glucose is too low. The alpha cells in the islets secrete
glucagon which enables the liver to convert glycogen to glucose and gluconeogenesis, which is
where the liver produces new sugar molecules from fats and amino acids.
c.
How insulin & glucagon levels are determined
Insulin & glucagon deterine the level of glucose in the blood. Chemoreceptors detect the change
and a negative feedback loop is initiated.
4.
Influence of hormones on adrenal glands on blood sugar concentrations
The adrenals secrete glucocorticoids, which ensure enough energy is provided to the cells by
stimulating the conversion on glycogen to glucose. They also increase the rate at which amino
acids are removed from cells and transported to the liver for construction.
The adrenals (medulla) secrete adrenaline and noradrenaline. These hormones prepare the
body either for exercise or the fight-or-flight response ensuring the body has enough glucose
for this. It counteracts the effects of insulin.
5.
Why does BGL rise after a meal?
Glucose concentration rises as the glucose is broken down and absorbed into the bloodstream.
Apply Your Knowledge
1.
Athletes and ADH concentration
Stimulus = rising BGL
Receptors = chemoreceptors in the beta cells of the islets of Langerhans
Modulator = beta cells secrete insulin
Effector = liver & muscles
Response = liver and muscles take up glucose
Feedback = BGL drops
2.
Body systems & role in regulation of BGL
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Nervous = brain stimulated to eat food
Digestive = breaks down food and absorbs into bloodstream especially glucose
Endocrine = produces and secretes hormones insulin and glucagon, cortisol and adrenaline,
and ACTH.
Circulatory = Transports food and hormones around the body.
Muscular = Cells use glucose to release energy, stores glucose as glycogen.
Excretory = Kidneys reabsorb filtered glucose to maintain levels and liver deaminates proteins
to produce glucose when levels are low, also converts lactic acid into glucose.