4.5.1 homeostasis

Question 1

Define the term homeostasis

Answer 1

The regulation of the internal conditions of a cell or organisation to maintain optimum conditions for function in response to internal and external changes

Question 2

Name the four conditions which are kept at constant for chemical reactions to occur within the body

Answer 2

Water content
Mineral ion content (salts)
Temperature
Glucose concentration

Question 3

How does water get in and out of the body?

Answer 3

In -
Consuming drinks / foods

Out-
Through skin as sweat and urinating
Kidneys control amount of water excreted in urine
Water loss from lungs when breathing out

Question 4

What is the normal human body temperature

Answer 4

37 °C

Question 5

What happens if body temperature rises too high?

Answer 5

Enzymes become so denatured until they no longer work, disrupting the body’s metabolism

Question 6

What happens if body temperature decreases too much

Answer 6

The Metabolic process slows down too much the enzymes no longer work

Question 7

What are nerves

Answer 7

They transmit information to and from the brain/ spinal cord (the central nervous system), through fast moving electrical impulses (signals). They contain special cells called neurons.

Question 8

What are hormones

Answer 8

They are chemicals made by certain glands which carry information between organs.

Question 9

Define the term ‘secretion’ and how does this relate to hormones.

Answer 9

Secretion - the release of hormones.
Hormones are secreted into and carried around the body in the bloodstream.

Question 10

How are conditions controlled within the body (hint, five stages to negative feedback)

Answer 10

The change is detected
Corrective mechanisms are activated
Conditions return to set point
Corrective mechanisms switch off
Conditions in the body change back to original conditions
This is then repeated again if a change is detected

Question 11

What is the role of the hypothalamus

Answer 11

It monitors body temperature

Question 12

What detects changes in temperature and how does it detect this?

Answer 12

A change in temperature is detected by the thermoregulatory centre in the hypothalamus. This centre detects the change by using receptors in the brain, also receiving feedback from skin reception

Question 13

What is vasoconstriction

Answer 13

This happens when body temperatures are too low, sweating stops and shivering begins.

Question 14

What is vasodilation

Answer 14

Happens when temperatures in the body are too high, sweat produces- energy is transferred to surroundings via skin, resulting in a cooling effect.

Question 15

Summarise a reflex arc

Answer 15

In a reflex arc the electrical impulses bypass the conscious area of your brain. From the receptors in the sense organs, the nerve impulses travel along the sensory neurone to the relay organ and then along the motor neurone where it arrives at the effector organ to initiate a response.

Question 16

What are endorphins

Answer 16

A chemical that make you feel happy and a lot are released when you take some drugs.

Question 17

Give an example (7 steps long) of a reflex arc

Answer 17

1- when you touch a hot object the receptor I’m your skin is stimulated
2- an electrical impulse travels from the receptor and along the sensory neurone to the spinal cord.
3. When an impulse from the sensory neurone arrives at the synapse with the relay neurone a chemical is released
4. The chemical diffusés across the synapse, reaches the relay neurone and sets off a new chemical signal.
5. The chemical diffusés across the gap between relay / motor neurones and triggers an electrical signal to move along the motor neurone
6. The electrical signal travels along relay neurone to motor, when it reaches the synapse in between, where another chemical is released.
7. When impulse reaches the effector organ, it is stimulated to respond