(a)the need for communication systems in multicellular organisms

To include the need for animals and plants to respond to changes in the internal and external environment and to coordinate the activities of different organs.

homeostasis

• is critically important for organisms as it ensures the maintenance of optimal conditions for enzyme action and cell function despite external changes

examples of physiological factors that are controlled by homeostasis in mammals:

• Core body temperature

• Metabolic waste (eg. carbon dioxide and urea)

• Blood pH

• Concentration of glucose in the blood

• Water potential of the blood

• Concentration of respiratory gases (carbon dioxide and oxygen) in the blood

two communication systems in mammals that allows information to be transferred between different parts of the body:

• the nervous system

• the endocrine system

the nervous system

• consists of:

  • The central nervous system (CNS) – the brain and the spinal cord

  • The peripheral nervous system (PNS) – all nerves in the body

• It allows us to make sense of our surroundings and respond to them and coordinate and regulate body functions

nerves

• Information is sent through the nervous system as nerve impulses (electrical signals)

• is a bundle of neurones (nerve cells)

• Neurones coordinate the activities of sensory receptors (eg. those in the eye), decision-making centres in the central nervous system, and effectors such as muscles and glands

hormones

• is a chemical substance produced by an endocrine gland and carried by the blood

• chemicals which transmit information from one part of the organism to another and bring about a change

• They alter the activity of one or more specific target organs

• Hormones are used to control functions that do not need instant responses.

the endocrine system consists of: unflinshed

• the pituitary gland (master gland)

  • situated at the base of the brain

• thyroid gland

  • based around neck

  • produces thyroxine

• Pancreas

  • produces insulin to regulate blood glucose levels

  • produces digestive enzymes such as pancreatic amylase lipase

• Adrenal glands

  • produces adrenaline

• testes (males)

  • produces testosterone (male sex hormone)

• ovaries (females)

  • produces oestrogen