Thermoregulation

Why do multicellular organisms need communication systems? [2]

• To respond when their internal and external environment changes

• To coordinate function

What is cell signalling?

Communication between cells, electrical signals carried by neurones or chemical signals as hormones

What are the three types of cell signalling?

• Endocrine

• Paracrine

• Autocrine

What is endocrine signalling used for?

Long distance

What is Paracrine signalling used for?

Signalling between adjacent cells occurs directly or aided by extracellular fluid

What is autocrine signalling?

Cell releases signals to stimulate its own receptors and triggers a response within itself

What is homestasis?

Internal environment is maintained within set limits around an optimum

Define negative and positive feedback

Negative feedback: Self regulatory mechanisms that reverse a change in internal environments

Positive feedback: A change in internal environment is furthered by actions in the body

What are receptors and effectors?

Receptors: specialised cells located in sense organs that detect a specific stimulus

Effectors: Usually muscles or glands which enable a physical response to a stimulus

What is an ectotherm?

An organism that relies on external sources to regulate its body temperature

What is an endotherm?

Organism that can regulate their own body temperature via internal physiological or behavioural responses.

Outline behavioural methods endotherms use to regulate their body temperature

• Baking in the sun

• Pressing against warm surfaces

• Digging burrows

• Hibernation

• Panting

How does the autonomic nervous system enable endotherms to Thermoregulate? [4]

• Via negative feedback

• Peripheral thermoreceptors detect changes in skin temperature

• Thermoreceptors in hypothalamus detect changes in blood temperature

• Hypothalamus sends impulses to effectors in skin and muscles

Explain the role of the skin in Thermoregulation [3]

• Vasodilation/Constrction of arterioles supplying skin capillaries controls heat loss to skin surface

• Hair erector muscles contract and follicles protrude to trap air for insulation

• Evaporation of swear cools skin surface

Give an example of positive feedback

• Blood clotting/Childbirth

Give an example of negative feedback

The control of blood glucose concentration