Communication And Homeostasis

Question 1

What is a stimulus?

Answer 1

An environmental change

Question 2

What is a response?

Answer 2

The way in which the organism changes its behaviour or physiology

Question 3

Give an example of a slow environmental change?

Answer 3

Arctic fox- thicker white coat in winter

Thinner grey brown coat in summer

Question 4

Example of quick environmental change?

Answer 4

Appearance of a predator

Question 5

What is the environment of our cells?

Answer 5

Tissue fluid

Question 6

What happens when cells undergo metabolic activities?

Answer 6

They use up substrate and create new products- that may be unwanted or toxic

Question 7

Give an example of a waste product and it’s affect on the body?

Answer 7

Carbon dioxide

If it builds up in the tissue fluid, it’ll alter the ph of the tissue fluid and disrupt action of enzymes.

Question 8

What is the response of the reduced ph of the blood?

Answer 8

Greater breathing activity to expel the carbon dioxide

Question 9

Factors of a good communication system?

Answer 9

Cover whole body
Enable cell signalling 
Enable specific communication 
Enable rapid communication 
Enable both short and long term responses

Question 10

What are the two major systems of communication that work by cell signalling?

Answer 10

Neuronal system

Hormonal system

Question 11

Features of neuronal system?

Answer 11

Interconnected network of neurones that signal across synapses.
Can conduct a signal quickly and enable rapid responses

Question 12

Features of hormonal system?

Answer 12

Uses blood to transport signals
Transported through the body but only recognised by specific target cells.
Enables longer term responses

Question 13

Definition of homeostasis?

Answer 13

Maintaining a constant internal environment despite changes in external and internal factors.

Question 14

Definition of effector?

Answer 14

A cell, tissue or organ that brings about a response.

Eg- liver or muscle cells

Question 15

Aspects maintained by homeostasis?

Answer 15

Body temperature 
Blood glucose concentration 
Blood salt concentration
Blood water potential 
Blood pressure
Carbon dioxide concentration

Question 16

Order of response pathway

Answer 16

Stimulus 
Receptor 
Communication pathway 
Effector 
Response

Question 17

Definition of sensory receptors?

Answer 17

Cells/ sensory nerve endings that respond to a stimulus in the internal or external environment of an organism and can create action potentials.

Question 18

What is the input?

Answer 18

Message or signal sent from the receptor to the coordination centre.

Question 19

What is the output?

Answer 19

Message sent from coordination centre to the effector

Question 20

Definition of negative feedback?

Answer 20

The mechanism that reverses a change, bringing the system back to optimum.

Question 21

Flow diagram of negative feedback:

Answer 21

Optimum condition 
Change away from optimum 
Receptor detects change 
Communication system informs effector 
Effector reacts to reverse change 
Return to optimum

Question 22

Example of negative feedback?

Answer 22

Internal temperature increases above optimum

Question 23

What part of the brain detects temperature change?

Answer 23

Thermoregulatory centre in hypothalamus

Question 24

Definition of positive feedback?

Answer 24

The mechanism that increases a change taking the system further away from optimum.

Question 25

Example of positive feedback?

Answer 25

The release of oxytocin during contractions to increase dilation of the cervix further.

Question 26

Definition of endotherm?

Answer 26

An organism that uses heat from metabolic reactions to maintain body temperature

Question 27

Definition of ectotherms?

Answer 27

An organism that relies on external sources of heat to maintain body temperature.

Question 28

How ectotherms try to absorb more heat?

Answer 28

Move into sunny area Lie on warm surface Expose larger surface area to sun

Question 29

How do ectotherms cool down?

Answer 29

Move out of sun Move underground Reduce surface area exposed to sun

Question 30

How to snakes absorb heat?

Answer 30

Basks in sun- absorbs heat directly from sun

Question 31

How do locusts absorb heat?

Answer 31

Sit side on to the sun exposing a large surface area.

Question 32

How do locusts absorb less heat?

Answer 32

Cline to top of plant to avoid soil surface as it is hot and radiates heat.

Question 33

How do locusts cool down?

Answer 33

Increases breathing rate and depth of breathing to evaporate water from the tracheal system

Question 34

How does a lizard control temperature?

Answer 34

Hides in a burrow during hottest and coldest times. Underground burrows tend to have a stable temperature

Question 35

How does a horned lizard control its temperature?

Answer 35

Can expand its rib-cage to expose the surface area exposed to the sun so more heat can be absorbed

Question 36

Advantages of ectotherms?

Answer 36

Less food is used in respiration- more can be converted to growth They need to find food is smaller and they can survive longer without food.

Question 37

Disadvantages of ectotherms?

Answer 37

Less active in cool temperatures | At risk from predators when it's cold and cannot take advantage of food.

Question 38

What is the hypothalamus?

Answer 38

Part of the brain that coordinates homeostatic responses

Question 39

What are exergonic reactions?

Answer 39

Reactions that release energy in the form of heat

Question 40

Responses when too hot?

Answer 40

``` Sweat glands secrete Hairs lie flat Vasodilation of arterioles and pre capillary sphincters. Panting Less respiration takes place Fewer skeletal muscle contractions ```

Question 41

How does sweating cool you down?

Answer 41

Sweat glands secrete fluid onto skins surface. As the fluid evaporates it uses heat from the blood as the latent heat of vaporisation.

Question 42

What is excretion?

Answer 42

The removal of metabolic waste from the body

Question 43

What is metabolic waste?

Answer 43

A substance that is produced in excess by the metabolic processes in the cells; may become toxic

Question 44

Why can't metabolic waste products be allowed to build up?

Answer 44

So they do not inhibit enzyme activity or become toxic

Question 45

What are the main excretory products?

Answer 45

CO2 from respiration Nitrogen-containing compounds such as urea Other compounds such as bile pigments found in faeces

Question 46

What is egestion?

Answer 46

The elimination of faeces from the body

Question 47

What are the excretory organs?

Answer 47

Lungs Liver Kidneys Skin

Question 48

Functions of the liver? (7)

Answer 48

Control of blood glucose levels, amino acid levels, Lipid levels Synthesis of bile, plasma proteins, cholesterol Synthesis of red blood cells in the fetus Storage of vitamins A,D,B12, iron, glycogen Detoxification of alcohol and drugs Breakdown of hormones Destruction of red blood cells

Question 49

External structures of the kidney?

Answer 49

Cortex Medulla Pelvis

Question 50

Describe the nephrons?

Answer 50

Tiny tubules in the bulk of each kidney Starts in the cortex as a cup-shaped structure- bowmans capsule Forms a loop down into the medulla Joins a collecting duct