Homeostasis

Question 1

define homeostasis

Answer 1

the maintenance of a relatively stable internal environment in the body, maintained within narrow limits, despite changes in the external environment.

Question 2

explain the role of the endocrine and nervous system in the maintenance of homeostasis

Answer 2

the actions of both nerves and hormones involve chemical substances; hormones are chemicals themselves transported in the bloodstream, while nerves use neurotransmitter chemicals to facilitate electrical signaling. Nerves tend to bring out a response very rapidly, while hormonal responses take much longer to show effect but tend to last longer. The initiation of homeostatic responses results from an external or internal stimulus, which is detected by a specific type of receptor.

Question 3

osmoregulation definition

Answer 3

the homeostatic regulation of osmolarity in the body via the alteration of water and solute balance.

Question 4

ADH definition

Answer 4

antidiuretic hormone: a molecule secreted by the posterior pituitary gland in response to high solute concentrations in the blood. ADH increases the amount of water absorbed by the distal convoluted tubule and collecting duct and hence the amount of water conserved by the body

Question 5

recall the three things that happen when blood water levels are low

Answer 5

• more ADH is released from the posterior pituitary gland
• ADH stimulates the production of aquaporins in the collecting ducts of the kidneys, making them more permeable to water.
• more water is reabsorbed into the bloodstream and less water is lost in urine

Question 6

recall the three things that happen when blood water levels are high

Answer 6

• less ADH is released from the posterior pituitary
• less aquaporins are produced in the collecting ducts of the kidneys, making them less permeable to water
• less water is reabsorbed into the bloodstream and more water is lost in urine

Question 7

define negative feedback

Answer 7

a stimulus-response process in which the response counters the stimulus, to maintain homeostasis.

Question 8

fill in the blank

Answer 8

Question 9

define glucose

Answer 9

a six-carbon carbohydrate that comes from food that is used to power cellular respiration and is the main source of energy in the body

Question 10

define glycogen

Answer 10

a polysaccharide of glucose that stores energy and serves as the main storage of glucose in the body

Question 11

define glucose transporter

Answer 11

a group of membrane proteins that transport glucose across the plasma membrane

Question 12

define blood glucose

Answer 12

a measure of the amount of glucose present in the blood. Normal homeostatic mechanisms keep blood glucose levels between 4.0-7.8 mmol/L.

Question 13

what organ, cells and hormones/proteins are involved in the regulation of blood glucose?

Answer 13

the pancrease (the α and β cells of the islets of langerhans) produces insulin and glucagon. These hormones act to regulate blood glucose levels through a negative feedback system.

Question 14

what happens between α and β cells when blood glucose is low

Answer 14

• the α cells of the pancrease increase their production of glucagon. This stimulates the conversion of glycogen (stored in the liver) to glucose that is released into the bloodstream.
• β cells decrease production of insulin so the uptake of glucose from the blood is increased

Question 15

what processes happen when blood glucose is high

Answer 15

• glucose must be shifted from the blood into the liver and the muscles where it is stored as glycogen
• the β cells of the pancreas detect the increase and initiate a response in which insulin production is increased and glucagon is decreased.
• the increase in insulin circulating in the bloodstream acts on the body cells, facilitating the uptake of glucose from the blood into body cells.

Question 16

fill in the blank

Answer 16

Question 17

fill in the blank

Answer 17

Question 18

define alpha cells

Answer 18

cells that occupt the islets of langerhans and secrete glucagon

Question 19

define beta cells

Answer 19

cells that occupt the islets of langerhans and secrete insulin

Question 20

define insulin

Answer 20

a hormone secreted by beta cells of the pancreas where blood glucose levels are elevated

Question 21

define glucagon

Answer 21

a hormone secreted by alpha cells of the pancreas when blood glucose levels are low

Question 22

define type 1 diabetes

Answer 22

an autoimmune disease in which beta cells of the pancreas are destroyed, resulting in an inability to regulate blood glucose levels. Individuals are unable to take up glucose from the bloodstream, resulting in blood glucose levels being higher than normal.

Question 23

define type 2 diabetes

Answer 23

a disease in which the body becomes resistant to the effects of insulin, and/or doesnt produce enough insulin to maintain normal blood sugar levels. Insulin is produced, but the cells are said to be insulin resistant - resulting in higher levels of glucose

Question 24

autoimmune disease definition

Answer 24

a disease in which individuals immune system initiates an immune response against their own cells

Question 25

define hypoglycaemia

Answer 25

the state of having blood glucose levels below the normal range (<4.0mmol/L)

Question 26

define hypothyroidism

Answer 26

overactivity of the thyroid gland, resulting in increased production and secretion of thyroid hormones.

Question 27

define homeothermy

Answer 27

the maintenance of body temperature within narrow limits by physiological mechanisms, despite changing external temperatures

Question 28

recall the 4 mechanisms for homeothermy

Answer 28

1. Physiological adaptation
2. Behaviour adaptation
3. Structural adaptation
4. Structural and physiological adaptation

Question 29

define physiological adaptation

Answer 29

the functions of organs of the body that can facilitate hypothermy when body temperature is too low or high.

Question 30

define behavioural adaptation

Answer 30

to do with how organisms interact or response to their physical environment

Question 31

define structural adaptation

Answer 31

to do with the physical construction of an organism or part of it that helps regulate body temperature and thus maintain homeostasis.

Question 32

define structural and physiological adaptation

Answer 32

adaptations for temperature regulation that are a combination of structure and physiology.