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F214-Communication, Homeostasis and Energy

Module 1-Communication and Homeostasis

4.1.1 Communication

a. Outline the need for communication systems within multicellular organisms

External environmental changes
o Changes in the external environment can cause stress.
o It may change slowly so there will be a gradual response.
o It may be a quick…

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o It destabilises the system meaning that it tends to be harmful.
o This is when the internal environment is kept constant even though there
are external changes.
o It can include conditions such as body temperature, blood glucose
concentration, blood pressure and carbon dioxide concentration.

e. Explain the…

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Move higher up a plant to
get away from the hot
ground e.g. locusts.
Endotherms Secrete more sweat onto Move into shade.
skin so the water in the Hide in burrow.
sweat evaporates using Orientate body away from
latent heat from the the sun to expose a smaller
blood. surface…

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o A generator potential is caused when one or two sodium ion channels
open and if more open and enough sodium ions enter the cell and action
potential will be initiated.

b. Describe the structure and function of sensory and motor neurones

Sensory neurones
o Carry the action potential from…

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c. Describe and explain how the resting potential is established and maintained

When the neurone is not transmitting an action potential it is said to be at rest.
The neurone is not actively transporting ions across its cell surface membrane.
It is about -60mV inside the cell compared to the…

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1. The membrane is at its resting potential and is polarised.
2. Sodium ion channels open and some sodium ions diffuse into the cell. The
membrane depolarises as it becomes less negative the outside and reaches the
threshold of -50mV. Voltage-gated sodium ion channels open and sodium ions
flood in…

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In the peripheral nervous system In the Central Nervous System and
carrying impulses from sensory in the nerves controlling the organs
receptors to the Central Nervous with no conscious control.
System or from the Central Action potential moves in a wave.
Nervous System to the effector. Carry signals over a…

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Allow several presynaptic neurones to converge into one postsynaptic neurone
to allow signals from different parts of the nervous system to create the same
Allow one presynaptic membrane to diverge into several postsynaptic neurones
to allow one signal to be passed to several parts of the body.
Ensure that…

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Adrenaline is the first messenger.

When the adrenaline binds it makes the Adenyl Cyclase active.

The Adenyl Cyclase converts ATP to Cyclic AMP.

Cyclic AMP is the second messenger and it activates enzyme action in the cell.

c. Describe the function of the adrenal glands

Adrenal glands

o They lie…

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Exocrine function

o Secretes enzymes.

o Manufactures and secretes digestive enzymes.

o The tubules join up to make the pancreatic duct.

o Enzymes are released in a fluid. The enzymes in the fluid are: Amylase,
Trypsinogen and Lipase.

o Also contained in the fluid is sodium hydrogencarbonate.

Endocrine function






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