BIOLOGY -MODULE 5 COMMUNICATION,HOMEOSTASIS AND ENERGY

Cell signalling

Cells communicate with each other by cell signalling to produce a response

Cell signalling in animals responses

Hormones (chemical response)

Neurones (electrical response)

Cell signalling in plants responses

Plant hormones (chemical hormones)

Why do multicellular cells communicate?

Organisms must respond to stimulus

1) Immune response

2) Maintain blood glucose Regulation

3) To complete a task

4) Tissue repair

5) Maintain body temperature

How do multicellular organisms communicate?

Hormonal and the nerve communication system

Examples of internal environments kept relatively constant:

Blood glucose concentration

Internal temperature

Water potential (oedema)

Blood PH

Principles of homeostasis

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Define Homeostasis

the ability to maintain a relatively constant internal conditions at a set point

Examples of internal conditions

Body temperature 37 degrees

Blood PH 7.35 - 7.45

Blood glucose concentration 70-100 mg/dl

Blood oxygen saturation 98%

Water potential of blood

Homeostasis Mechanism/Control

Stimulus

Receptor

Sensory Neuron

Relay neurone

Control centre

Motor neurone

Effector

Define Receptor

Cells that detects changes

Define Control centre

Interprets and decides the response

Define Effector

Muscles or glands that carry out the response

What is negative feedback?

Returning a change in a condition back to a set point

What is positive feedback?

Reinforce change, so the change deviates further from the set point.

Vasodilation of arterioles to lose heat

1) Smooth muscle of Arteriole Vasodilates, widens the lumen

2)More blood flows to the surface of the skin

3)More heat is lost from the skin surface via radiation, Convection reverses the body temperature back to a set point (Negative feedback)

Vasocontraction of arterioles to conserve heat

1) Smooth muscle of Arteriole Vasoconstricts, narrows the lumen

2)Less blood flows to the surface of the skin

3)Less heat is lost from the skin surface via radiation, Convection reverses the body temperature back to a set point (Negative feedback)