5.1.1 - Communication and Homeostasis

Question 1

What is homeostasis?

Answer 1

The maintenance of a constant internal environment via physiological control systems

Question 2

Why do animals and plants need communication systems?

Answer 2

So any response to an internal or external change in environment is coordinated including the activities of different organs

Question 3

What must a good communication system be able to do?

Answer 3

• Cover the whole body
• Enable cell to cell communication
• Be specific and rapid
• Give short term or long term responses

Question 4

Which 2 communication systems work by cell signalling?

Answer 4

Neuronal system and hormonal system

Question 5

What are the differences between the neuronal system and the hormonal system?

Answer 5

• Neuronal system uses nerve impulses and hormonal system uses hormones
• Neuronal system is electrical whereas hormonal system is chemical
• Neuronal system is transmitted via neurones and hormonal system is transmitted via the bloodstream
• Neuronal system is very rapid whereas the hormonal system is slow
• Neuronal system travels to specific glands or muscles in the body and the hormonal system travels all over the body but only cells in target tissues or organs respond
• Neuronal system has a localised effect whereas hormonal system has a widespread effect
• Neuronal system effect is short term and temporary whereas hormonal system effect is short term and temporary or long term and permanent

Question 6

What is a receptor?

Answer 6

A specialised cell to detect a stimulus

Question 7

What is an effector?

Answer 7

Usually a gland or a muscle to respond to a stimulus

Question 8

What is negative feedback?

Answer 8

Where a change from the set level will cause the body or cell to correct that change to bring it back to the normal value

Question 9

What are examples of negative feedback loops?

Answer 9

• Blood glucose concentration
• Body temperature

Question 10

What is positive feedback?

Answer 10

Where a change from the set level causes the change to increase further from the set level

Question 11

What are examples of positive feedback loops?

Answer 11

• Production of breast milk
• Contractions of uterine muscles during labour
• Generation of an action potential

Question 12

Why is thermoregulation needed?

Answer 12

• If body temperature drops too low there would be insufficient kinetic energy for enzyme controlled reactions
• If body temperature is too high enzymes would denature

Question 13

What are physiological responses?

Answer 13

Automatic changes in the body

Question 14

What are 3 examples of physiological responses for thermoregulation?

Answer 14

• Sweating
• Panting
• Shivering

Question 15

What are behavioural reponses?

Answer 15

Usually involve the whole organism

Question 16

What are 2 examples of behavioural responses for thermoregulation?

Answer 16

• Moving into the sun
• Moving into the shade

Question 17

What are ectotherms?

Answer 17

They have a body temperature which tends to fluctuate with the external environment and they cannot regulate their internal temperature so they rely on external sources to keep warm or cool.

Question 18

What behavioural responses do ectotherms carry out to maintain a suitable body temperature?

Answer 18

• Basking in the sun or moving into the shade
• Change body orientation to the sun

Question 19

What physiological responses do ectotherms carry out to maintain a suitable body temperature?

Answer 19

• Alter body shape to increase or decrease surface area
• Change breathing rate

Question 20

What are endotherms?

Answer 20

They maintain a core body temperature within very strict limits, largely independent of the external environment, through both physiological and behavioural responses

Question 21

How is internal temperature monitored and controlled by endotherms?

Answer 21

By the hypothalamus in the brain through a negative feedback system

Question 22

How is external temperature detected by endotherms?

Answer 22

By peripheral temperature receptors in the skin

Question 23

What happens once a change in temperature has been detected?

Answer 23

The hypothalamus sends nerve impulses to effectors in the skin and muscles to bring about responses to lower or raise body temperature

Question 24

What are the physiological changes to reduce body temperature?

Answer 24

• Sweat glands secrete more sweat which evaporates and cools body by transferring heat energy to surroundings
• Arteriole vasodilation causes more blood to flow in skin capillaries so more heat is transferred through radiation
• Hair lies flat providing little insulation

Question 25

What are the physiological changes to increase body temperature?

Answer 25

• Sweat glands secrete less sweat so less heat is transferred from blood to surroundings
• Arteriole vasoconstriction causes less blood to flow in skin capillaries so less heat is transferred through radiation
• Hair is raised to trap an insulating layer of hair
• Shivering which increases the rate of respiration so more heat energy is released