Homeostasis

Question 1

What is homeostasis?

Answer 1

A dynamic, self-regulatory process by which a biological system maintains internal stability while adjusting to environmental changes

Question 2

What are examples of internal conditions that are homeostatically regulated, and what diseases are caused by disruption of their homeostasis? (7)

Answer 2

Body temp - hypothermia
Body weight - obesity/anorexia
Blood glucose levels - diabetes
Blood gases - hypoxia
Ion concentrations - anaemia, hyponatremia
Blood pressure - hypertension
Blood pH - acidaemia

Question 3

What are the 5 common misconceptions of the homeostatic control system and why are they wrong?

Answer 3

• Set point is a fixed value, wrong as it’s a RANGE of values
  -Set point is permanent, wrong as the set point changes as a result of a change in the system
  -Homeostatic mechanisms act like an ON/OFF switch, wrong as they are always active
  -The change in the physiological variable is the response of the effector, wrong as the change in the physiological variable is the CONSEQUENCE of the effector’s responses
• All negative feedback systems are homeostatic, wrong as can get non-homeostatic negative feedback loops

Question 4

What 2 control systems is homeostasis controlled by and how?

Answer 4

• Neuronal control systems - brain neurons activate effectors directly (relatively fast and short-lasting)
  -Hormonal control systems - hormones released into the bloodstream and act at distinct sites all over the body (relatively slow and long lasting)

Question 5

What are the 2 hormones involved in blood glucose regulation, where are they produced exactly, and what do they do?

Answer 5

• Insulin = produced in the BETA cells of the pancreas in response to rising levels of blood glucose. Insulin secretion stimulates uptake of glucose from the blood and storage of glucose in the form of glycogen in the liver to decrease blood glucose levels.
• Glucagon = produced in the ALPHA cells of the pancreas in response to low levels of blood glucose. Glucagon secretion stimulates the breakdown of glycogen into glucose + breakdown of other stores such as fat into glucose to increase blood glucose concentrations.

Question 6

What is diabetes mellitus, and what are the 2 types caused by?

Answer 6

Persistent high blood glucose concentrations
Type 1 = Failure of the pancreas to produce enough insulin
Type 2 = Decreased sensitivity of body/liver cells to insulin

Question 7

What is the classic approach to scientific understanding of disease? (3 steps)

Answer 7

• Understand the normal physiological control systems that are involved
• Understand how they are disturbed with disease
  -Develop treatments + interventions which allow the recovery of normal homeostasis as far as possible