5.1.1 -Communication and homeostasis Flashcards
Define homeostasis
maintenance of a constant internal environment despite internal or external changes
Why do multicellular organisms need
communication systems?
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To respond when their internal &
external environment changes.
To coordinate organ function.
What is cell signalling?
Communication between cells: electrical signals carried by
neurons or chemical signals as hormones.
● Long-distance endocrine signalling.
● Paracrine signalling between adjacent cells occurs
directly or aided by extracellular fluid.
● In autocrine signalling, cell releases signals to stimulate
its own receptors & triggers a response within itself.
What is homeostasis?
Internal environment is maintained within
set limits around an optimum.
Define negative and positive feedback.
Negative feedback: self-regulatory mechanisms
return internal environment to optimum when
there is a fluctuation.
Positive feedback: a fluctuation triggers
changes that results in an even greater deviation
from the normal level.
What are receptors and effectors?
Receptors: specialised cells located in
sense organs that detect a specific
stimulus.
Effectors: usually muscles or glands which
enable a physical response to a stimulus.
What is an ectotherm?
Organism that cannot increase its respiration rate
to increase the internal production of heat.
Relies on external sources to regulate its body
temperature. Responds to temperature changes
behaviourally e.g. may orient body to minimise/
maximise sun exposure.
Why is it important for the body to regulate PH?
Body’s PH=7.35
Any changes to that means that proteins will lose their shape (denatured). SO reactions in the blood/cells won’t be catalysed
Importance of regulating blood water potential
ψ surrounding cell is ↑= cell bursts
ψ surrounding cell is ↓= cell crenation(shrinks)
Outline the importance of blood glucose levels
glucose is needed by cells for energy.
↑ conc. levels= the ψ of tissue fluid/blood ↓. Damages cells as crenation occurs,making us feel dehydrated.
↓ conc, levels = the ψ of tissue fluid/blood ↑. Cells don’t have access to the energy they require.
Compare negative and positive feedback
Negative feedback is the body’s mechanism for reversing a change so that it returns back to the optimum. WHEREAS positive feedback ampifies the change away from the optimum
Outlin ethe mechanism for negative feedback
Receptors=Detect the change & send it to coordinator
Coordinators= Decide what to do and send this signal to effectors
Effectors(muscles/glands)= bring about change that returns internal conditions to optimum
