Homeostasis

Question 1

Define homeostasis.

Answer 1

The condition of a relatively stable internal environment, maintained within narrow limits.

Question 2

What are 8 conditions needing controlling?

Answer 2

1. Carbon dioxide
2. Oxygen
3. Wastes
4. Temperature
5. Salts
6. Water
7. pH
8. Glucose

Question 3

Why do carbon dioxide levels need to be maintained within limits?

Answer 3

When dissolved in water it forms carbonic acid, lowering pH and affecting enzyme activity.

Question 4

Why do oxygen levels need to be maintained within limits?

Answer 4

To supply energy for cellular functioning.

Question 5

Why do nitrogenous waste levels need to be maintained within limits?

Answer 5

High concentrations inhibit the reactions that form them and raise pH.

Question 6

Why do temperature levels need to be maintained within limits?

Answer 6

Affects enzyme activity and metabolism.

Question 7

Why do salt levels need to be maintained within limits?

Answer 7

Sodium from sodium chloride is important in regulating fluid levels as well as nerve transmission and muscle contraction.

Question 8

Why do water levels need to be maintained within limits?

Answer 8

It maintains the concentration of cell contents at the correct level for cellular reactions.

Question 9

What are the 6 stages of a steady state system?

Answer 9

1. Stimulus
2. Receptor
3. Modulator
4. Effector
5. Response
6. Feedback

Question 10

Define stimulus.

Answer 10

Change in the internal environment.

Question 11

Define receptor.

Answer 11

Detects change.

Question 12

Define modulator.

Answer 12

Is the control centre, processes information from receptors, compares information from optimum and sends messages to the effector.

Question 13

Define effector.

Answer 13

Carries out the response.

Question 14

Define response.

Answer 14

Counteracts the stimulus.

Question 15

Define feedback.

Answer 15

The original stimulus changed.

Question 16

What are the 2 types of feedback loops?

Answer 16

1. Positive feedback loop.
2. Negative feedback loop.

Question 17

What is a negative feedback loop?

Answer 17

An increase in one thing leads to a decrease in another.

Question 18

What is a positive feedback loop?

Answer 18

An increase in one thing leads to an increase in another.

Question 19

What are 4 ways to decrease heat loss?

Answer 19

1. Vasoconstriction.
2. Reduction in sweating.
3. Conscious behaviour - Putting on a jumper.
4. Reduction in surface area - Curl up into a ball.

Question 20

What are 3 ways to increase heat production?

Answer 20

1. Shivering.
2. Increase in voluntary activity.
3. Increased metabolic activity.

Question 21

What are 4 ways to increase heat loss?

Answer 21

1. Vasodilation
2. Sweating.
3. Conscious behaviour - Remove clothing.
4. Increase surface area - spreading out.

Question 22

What are 2 ways to decrease heat production?

Answer 22

1. Decrease in voluntary activity.
2. Decreased metabolic rate.

Question 23

Write an SRMERF for when there is an increase in temperature. Include 4 effectors and 4 receptors.

Answer 23

S - Increase the temperature in blood.
R - Thermoreceptos in the hypothalamus.
M - Hypothalamus.
E - Sweat glands, blood vessels, skeletal muscles, thyroid.
R - increased sweat production, vasodilation, seeking shade/increased surface area, decreased thyroxine secretion decreases metabolic rate.
F - Decrease temperature in blood.

Question 24

Write an SRMERF for when there is a decrease in temperature. Include 3 effectors and 3 receptors.

Answer 24

S - Decrease temperature in blood.
R - Thermoreceptos in the hypothalamus.
M - Hypothalamus.
E - Blood vessels, skeletal muscles, Thyroid.
R - Vasoconstriction, shivering/reduce surface area/seeking warmth, increased secretion of thyroxine increases metabolic rate.
F - Increase the temperature of the blood.

Question 25

What does a small increase in temperature cause?

Answer 25

Can cause an increase in enzyme activity. This increases metabolic rate.

Question 26

What does a significant increase in temperature cause?

Answer 26

It can cause enzymes to denature, leading to critically low metabolism. Cells can die. A person can experience heat stress and exhaustion. Cell membranes become too fluid, causing unwanted substances to enter and wanted substances to exit.

Question 27

How is ammonia formed?

Answer 27

When organisms break down proteins and nucleic acids.

Question 28

What can an increase in nitrogenous wastes cause?

Answer 28

An increase in the conetration of nitrogenous wastes the more toxic they become. An increase of ammonia in the blood can increase the pH. Enzymes only function within a certain pH tolerance range.

Question 29

What happens if cellular pH is outside the optimal range?

Answer 29

Enzyme activity can decrease.

Question 30

What happens if cellular pH is outside the tolerance range?

Answer 30

Enzymes can denature resulting in low metabolism.

Question 31

What can increase in water content cause?

Answer 31

This can lead to a decrease in collision rates of reactants involved in biochemical pathways, slowing metabolism. This will lead to a hypotonic solution. Water will move into cells to reach an equilibrium. If too much water enters cells they will swell and burst.

Question 32

What can a decrease in water content cause?

Answer 32

This can lead to a hypertonic solution. Causes water to move out of cells by osmosis. Causes dehydration and cells can shrink.

Question 33

What can cause an increase in salts?

Answer 33

An increase in salt concentrations outside of cells may result in water being transported out of cells by osmosis.