Introduction To Block 1 And Homeostasis

Question 1

What is the Greek meaning behind the word homeostasis?

Answer 1

‘Homeo’ = sameness

‘Stasis’ = standing still

Question 2

Define homeostasis.

Answer 2

Maintenance of a stable equilibrium especially through physiological processes

Question 3

What is body homeostasis?

Answer 3

The maintenance of the internal environment within narrow limits through interplay of regulatory processes despite changes inside + outside the body

Question 4

What types of factors interact to maintain homeostasis?

Answer 4

Chemical

Neural

Question 5

What can happen if one or more body component contributing to homeostatic maintenance stops working?

Answer 5

Homeostatic imbalance which can cause disease

Question 6

What organs are involved in homeostasis?

Answer 6

Hypothalamus
Pituitary gland
Heart
Lung
Liver
Kidney 
Pancreas 
Muscle

Question 7

What is a feedback system?

Answer 7

Cycle of events in which the status of a body condition is continually monitored, evaluated, changed + re-monitored

Question 8

What is negative feedback?

Answer 8

Output reduces the original stimulus

Question 9

What is positive feedback?

Answer 9

Output enhances the original stimulus

Question 10

What type of feedback is the most common?

Answer 10

Negative

Question 11

What are the 3 components of a feedback system? What does each do?

Answer 11

1. Receptor: monitors changes in controlled condition + sends info to control centre
2. Control centre: receives + evaluates input + generates output commands when needed
3. Effector: receives output from control centre + produces a response that changes the controlled condition

Question 12

What are some key examples of body homeostasis relevant for block 1?

Answer 12

Body temperature
Blood [glucose]
Fluid + electrolyte balance

Question 13

Describe the steps of a homeostatic response.

Answer 13

1. Stimulus disrupts homeostasis by increasing or decreasing a controlled condition
2. Condition monitored by receptors that send input (nerve impulses/ chemical signals)
3. Control centre receives input + provides an output (nerve impulses/chemical signals)
4. Effector brings about a change or response that alters the controlled condition
5. Return to homeostasis when response brings the controlled condition back to normal

Question 14

Describe the control of body temperature.

Answer 14

1. Stimulus interrupts homeostasis by decreasing body temperature
2. Thermoreceptors in skin + hypothalamus send nerve impulses
3. Hypothalamus + anterior pituitary send nerve impulse + TSH
4. Effectors:
   - Vasoconstriction
   - Adrenal medulla releases hormones that increase cellular metabolism
   - Skeletal muscles contract in repetitive cycle (shivering)
   - Thyroid gland release thyroid hormone increasing metabolic rate
5. Increased body temperature + return to homeostasis

Question 15

What is the reaction of alpha cells of the pancreas when there is hypoglycaemia?

Answer 15

1. Glucagon released to act on liver to break down glycogen into glucose + form glucose from lactic acid + certain AAs
2. Glucose released by liver cells raising blood glucose to normal
3. If blood glucose continues to rise, hyperglycaemia inhibits release of glucagon

Question 16

What is the reaction of beta cells of the pancreas when there is hyperglycaemia?

Answer 16

1. Insulin released to act on body cells to promote facilitated diffusion of glucose into cells, speed synthesis of glycogen from glucose + increase uptake of AAs + increase protein synthesis
2. Blood glucose falls
3. If glucose continues to fall, hypoglycaemia inhibits release of insulin

Question 17

Describe the process of homeostatic control of fluid and electrolyte balance.

Answer 17

1. Stimulus disrupts homeostasis by increasing blood [H2O]
2. Osmoreceptors in hypothalamus send nerve impulses
3. Hypothalamus + posterior pituitary release ADH
4. Cells in DCT + CD become more permeable to H2O increasing reabsorption
5. Increase in blood [H2O] + return to homeostasis

Question 18

What are some key examples of body homeostasis relevant to block 2?

Answer 18

BP
Acid base balance
Erythropoiesis