5.1 Communication and homeostasis

Question 1

Why do multicellular organisms need communication systems?

Answer 1

So they can survive.

To detect and respond to changes in the external and internal environment.

To make sure different organs are coordinated to keep them working effectively.

Question 2

How do cells communicate with each other?
How does this process work?

Answer 2

By cell signalling.

Can occur between adjacent and distant cells.

Question 3

What is homeostasis?

Answer 3

The maintenance of a constant internal environment.

Question 4

What is it important for homeostasis to maintain?

Answer 4

Temperature

Question 5

What is negative feedback?

Answer 5

The mechanism that restores levels back to normal.

Question 6

How does negative feedback work in steps?

Answer 6

There’s a shift from normal levels to levels being too high/ low.

The receptors detect this change.

Communication via the nervous or hormonal system.

The effectors then respond.

Level is brought back to normal.

Question 7

What is positive feedback?

Answer 7

Where change is amplified and takes the level further away from normal.

Question 8

What mechanism are involved in homeostasis?

Answer 8

-only negative.

Question 9

What are ectotherms?

Answer 9

animals that can’t controlled there body temperature internally so have to change there behaviour.

Question 10

What is an example of a ectotherm?

Answer 10

A lizard as they bask in the sun and find shade (change behaviour)

Question 11

What is ectotherms metabolic rate like and why?

Answer 11

variable as they can’t keep internal temperature constant.

Question 12

What are endotherms?

Answer 12

Animals that control there body temperature internally by homeostasis -as well as- altering behaviour.

Question 13

What is an example of an endotherm?

Answer 13

Elephant. Has homeostasis mechanisms but also rolls in mud too cool off.

Question 14

Where do mammals maintain body temperature?

Answer 14

In the hypothalamus.

Question 15

What are thermoreceptors and where are they found?

Answer 15

temperature receptors
found in hypothalamus and skin (peripheral temp receptors)

Question 16

What happens when there’s a rise in body temperature in mammals?

Answer 16

1. Thermorecptors detect body temp is too high and send impulse to hypothalamus then to effectors.
2. Effectors respond by:
   - vascodilation, sweating, hairs lie flat, no shivering m, no adrenaline released
3. Body temps fall back to normal

Question 17

What happens when there is a fall in body temperature in mammals?

Answer 17

1. Thermoreceptors detect fall in body temp and an impulse is sent to hypothalamus then effectors.
2. Effectors respond by:
   - Vascoconstriction, no sweating, shivering, hairs stand up, adrenaline released.
3. Body temps rise and fall back to normal.

Question 18

How does sweat cool us down?

Answer 18

As it evaporates it takes heat from the body and the skin is cooled.

Question 19

Why does lying hairs flat reduce body temp and how do they change direction?

Answer 19

Less air is trapped so skin is less insulated and heat can be lost more easily.

Change due to erector pili muscles relaxing to lie flat and contracting to stand up.

Question 20

How does vascodilation decrease body temp?

Answer 20

Arterioles dilate (get wider) so more blood can flow in capillaries in the dermis.
Blood is flowing closer to the skin so more heat can be lost from the skin by radiation and temp is lowered

Question 21

How does vascoconstriction cause an increase in body temp?

Answer 21

Arterioles near skin contract so less blood flows through the dermis and so less heat is lost and temps increase.