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Communication, Homeostasis & Energy

Communication & Homeostasis
Outline the need for communication systems within multicellular organisms, with reference to the need to respond to
changes in the internal and external environment and to co-ordinate the activities of different organs.
Organisms need to respond to external stimuli, e.g. temperature, oxygen concentration…

Page 2

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Communication, Homeostasis & Energy

Hot- reduce rate of metabolism so less heat is generated from exergonic reactions
e.g. respiration.
Cold- increased rate of metabolism so more heat is generated. Respiration
generates more heat which is transferred to the blood.
Skeletal muscles
Hot- not spontaneous contractions
Cold- spontaneous contractions generates heat…

Page 3

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Communication, Homeostasis & Energy

Describe and explain how an action potential is transmitted in a myelinated neurone, with reference to the roles of
voltage-gated sodium ion and potassium ion channels.
The myelin sheath is an insulating layer of fatty material which Na and K ions cannot pass through. Between
the…

Page 4

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Communication, Homeostasis & Energy

Outline the role of neurotransmitters in the transmission of action potentials.
A neurotransmitter is a chemical that diffuses across the cleft of the synapse to transmit a signal to the
postsynaptic neurone. They cause the generation of a new action potential in the postsynaptic neurone. In…

Page 5

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Communication, Homeostasis & Energy


Describe, with the aid of diagrams and photographs, the histology of the pancreas, and outline its role as an endocrine
and exocrine gland.
The cells surrounding exocrine gland of the pancreas secretes digestive enzymes into the pancreatic duct,
which then goes onto the small intestine. This…

Page 6

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Communication, Homeostasis & Energy

Discuss the use of insulin produced by genetically modified bacteria, and the potential use of stem cells, to treat diabetes
mellitus.
GM bacteria:
· Exact copy of human insulin.
o Faster acting.
o More effective.
· Less chance of developing tolerance.
· Less chance of rejection.…

Page 7

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Communication, Homeostasis & Energy

Excretion
Define the term excretion.
Excretion: The removal of metabolic wastes from the body
Explain the importance of removing metabolic wastes, including carbon dioxide and nitrogenous waste, from the body.
Carbon dioxide must be removed as, when it dissolves in water is produces hydrogencarbonate ions. These…

Page 8

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Communication, Homeostasis & Energy

Describe and explain the production of urine, with reference to the processes of ultrafiltration and selective
reabsorbtion.
Kidney
Ultrafiltration:-
· Blood flows into the glomerulus via the afferent arteriole which is at a higher pressure than the
blood that leaves through the efferent arteriole due to…

Page 9

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Communication, Homeostasis & Energy

Outline the problems that arise from kidney failure and discuss the use of renal dialysis and transplants for the
treatment of kidney failure.
Problems:
· Unable to remove excess water & waste products from the body
o E.g. urea & excess salts
· Inability to regulate…

Page 10

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Communication, Homeostasis & Energy

Photosynthesis
Define the terms autotroph and heterotroph.
Autotroph-organisms that use light or chemical energy and inorganic molecules to synthesise complex
organic molecules.
Heterotroph- organisms that ingest and digest complex organic molecules releasing the chemical potential
energy stored in them.
State that light energy is used during…

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