Slides in this set

Slide 1

Preview of page 1

Kiran Rehman…read more

Slide 2

Preview of page 2

a) Communication systems needed to respond to
internal and external environments to coordinate
activity of organisms.
· Nervous and hormonal systems coordinate
activity of organisms e.g. info transfer via cell
· Communication with receptors and effectors
allow organism to;
· Monitor internal and external environments
· Regulate substance levels in organism
· Respond adaptively to changes; change activity
of an organism in response to a stimulus
· Coordinate cell activity…read more

Slide 3

Preview of page 3

C) State that neuronal and hormonal
systems are examples of cell signalling
· Neuronal- give rapid but cause short term effects within
the cell such as the Symphatecic nerve stimulating sweat
secretion. (animals)
· Hormonal- slower than neuronal but give long lasting
effects such as growth. (plants and animals)…read more

Slide 4

Preview of page 4

b) State that cell need to communicate with each
other by a process called cell signalling
· Cell signalling is needed to coordinate cell activity
-Signal molecules such as hormones are secreted by glands
-signal molecule shapes are complementary to their receptors so they fit like a lock fits a key
-Signal molecules dock their receptors and bind causing a reaction to occur…read more

Slide 5

Preview of page 5

d) Define the terms negative feedback, positive
feedback and homeostasis
· Negative feedback= change in a system that sets in
motion a series of events that counteract the change and
restores to the original state; set point needed (e.g.
temp. regulation)
· Positive feedback= change in a system that sets in
motion series of events that results in further change
away from the original state (e.g. carbon dioxide
· Homeostasis= stable internal environment within an
organism providing constant conditions for cells…read more

Slide 6

Preview of page 6

e) Explain the principles of homeostasis in
terms of receptors, effectors and negative
· Negative feedback maintains homeostasis by body sensing a
change and activating mechanisms to reverse that change
· Negative feedback requires receptors and effectors with good
communication between them
· Receptors monitors factors being controlled .e.g. temperature
of the blood passing through the hypothalamus. If the value is
not suitable for the factor, the receptor communicates with
the effecter
· Effecter causes an action which brings the factor back to the
normal value
· Negative feedback is not instant as short delay from change
in factor, receptor and effecter taking action causes an
oscillation value rather than a definite…read more

Slide 7

Preview of page 7
Preview of page 7

Slide 8

Preview of page 8
Preview of page 8

Slide 9

Preview of page 9
Preview of page 9

Slide 10

Preview of page 10
Preview of page 10


No comments have yet been made

Similar Biology resources:

See all Biology resources »