Homeostasis

Question 1

How do you define homeostasis?

Answer 1

All variables must operate within a narrow range of values

Question 2

Is homeostasis of one variable independent of other variables?

Answer 2

No, balance is needed between different variables

Question 3

What are the two degrees of control of variables?

Answer 3

Tight and loose controls

Question 4

What is tight control of variables?

Answer 4

At any given time a variable will be close to a predicted value, and very rarely fluctuates

Question 5

What is an example of tight control of a variable?

Answer 5

Concentration of oxygen in blood; constant even when a person exercises

Question 6

What is looser control of variables?

Answer 6

Variable may fluctuate in response to diurnal rhythms; will average over the day to the normal value; mechanisms return variable to normal levels over a longer period of time

Question 7

What is an example of looser control of a variable?

Answer 7

Blood glucose; peaks after meal, falls during fasting

Question 8

What is the definition of a set point?

Answer 8

Point where we expect a variable to be at

Question 9

What is an example of a set point?

Answer 9

Body temperature at 37 Celsius

Question 10

How is a set point reset?

Answer 10

Temporarily stabilises at a different value; has a functional reason to change (is not a problem)

Question 11

What is an example of a set point being reset?

Answer 11

When fighting an infection, stabilises to higher body temperature. When exercising, muscles are more efficient at higher temperature which is caused by contraction/aerobic respiration

Question 12

Why are changes typically transient?

Answer 12

Mechanisms immediately start being triggered when a variable falls out of normal range

Question 13

What does the gain of a variable measure?

Answer 13

The precision by which a control system can prevent deviation from homeostasis

Question 14

What is the equation for the gain of a variable?

Answer 14

Amount of correction needed/ amount of abnormality after correction

Question 15

What does a larger gain signify?

Answer 15

More sensitive regulation/ more accurate

Question 16

What is negative feedback?

Answer 16

Signals “fine tune” the body’s response to a stimulus so that homeostasis can be achieved under the new conditions

Question 17

Where does negative feedback occur?

Answer 17

On all levels (cellular, tissue, organ, system)

Question 18

How does end-point inhibition/ competitive inhibition work as negative feedback?

Answer 18

Concentrations of final product block metabolism of initial enzyme/ concentrations of final product compete with initial enzyme

Question 19

What are reflex responses?

Answer 19

Requires knowledge from an integrating centre and a circuitry that connects receptor and effector; most are negative feedback

Question 20

What is an example of a reflex response?

Answer 20

Blood pressure regulation

Question 21

What are local responses?

Answer 21

Allow individual parts of body to self-regulate

Question 22

What is an example of a local response?

Answer 22

Vasodilation of vessels near contracting muscles during exercise, but not facial muscles

Question 23

What are the types of communication?

Answer 23

Hormonal, neuronal, local

Question 24

What types of communication are reflex responses?

Answer 24

Can be a combo of neuro and hormonal

Question 25

What do local responses do?

Answer 25

Release chemical for receptor; can be paracrine or autocrine