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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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Positive feedback
o Process that increases the change detected by the receptors.
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,…

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Orientate body away from
the sun to expose a smaller
surface area to the sun.
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…

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o The movement of the sodium ions causes a change in the potential
difference so the inside of the cell is less negative. This is called
o A generator potential is caused when one or two sodium ion channels
open and if more open and enough sodium ions enter…

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ATP is used to pump three sodium ions out of the cell for every two potassium
ions pumped in.
The cell membrane is polarised because there is a potential difference across it.

d. Describe and explain how an action potential is generated

When some of the sodium ion channels open…

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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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h. Compare and contrast the structure and function of myelinated and
non-myelinated neurones

Myelinated neurones Non-myelinated neurones
Fast speed of conduction- Slow speed of conduction-
100-200ms-1. 0.5-10ms-1.
Has nodes of Ranvier. Does not have nodes of Ranvier.
Has a myelin sheath with each Does not have a myelin sheath but…

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8. Sodium ion channels open.
9. Sodium ions diffuse into the postsynaptic neurone.
10. A generator potential is created.
11. If there are enough generator potentials then it will reach the threshold
potential creating a new action potential in the postsynaptic neurone.

k. Outline the roles of synapses in the…

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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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Glucocorticoids control the metabolism of carbohydrates and
proteins in the liver.

d. Describe the histology of the pancreas and outline its role as an endocrine
and exocrine gland

Exocrine function

o Secretes enzymes.

o Manufactures and secretes digestive enzymes.

o The tubules join up to make the pancreatic duct.



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