Coordination, Response & Homeostasis (Cambridge (CIE) IGCSE Co-ordinated Sciences (Double Award): Biology): Flashcards
Exam code: 0654 & 0973
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Central nervous system (CNS)
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Central nervous system (CNS)
The brain and spinal cord, which coordinate the body's responses.
What are the two main parts of the mammalian nervous system?
The central nervous system (CNS): the brain and spinal cord.
The peripheral nervous system (PNS): the nerves connecting the CNS to the rest of the body.
The central nervous system is made up of the brain and the cord.
spinal
What is the role of the nervous system?
It detects stimuli and coordinates rapid responses, using electrical impulses carried by neurones.
carry electrical impulses around the body.
Neurones
Name the three types of neurone and what each does.
Sensory neurones carry impulses from receptors to the CNS.
Relay (connector) neurones carry impulses within the CNS.
Motor neurones carry impulses from the CNS to effectors.
neurones carry impulses from receptors to the central nervous system.
Sensory
Motor neurones carry impulses from the CNS to (muscles or glands).
effectors
Relay neurone
A neurone that connects a sensory neurone to a motor neurone; found within the central nervous system.
Where in the body are relay neurones found?
Within the central nervous system (the brain and spinal cord).
Reflex action
A rapid, automatic response to a stimulus that does not involve conscious thought.
Describe the pathway of a reflex arc.
Stimulus → receptor
→ sensory neurone
→ relay neurone (in the CNS)
→ motor neurone
→ effector → response
A reflex action is rapid and , not involving conscious thought.
automatic
Why are reflex actions important?
They protect the body from harm by producing a fast, automatic response (e.g. pulling your hand away from a hot object).
In a reflex arc, the detects the stimulus.
receptor
Sense organ
A group of receptor cells that respond to a specific stimulus, such as light, sound, touch, chemicals or temperature.
Receptor
A cell that detects a stimulus (a change in the environment).
Give examples of sense organs and the stimuli they detect.
Eyes — detect light.
Ears — detect sound and balance.
Skin — detects touch, pressure and temperature.
Tongue and nose — detect chemicals (taste and smell).
are the sense organs that contain light receptors.
Eyes
Receptor cells detect (changes in the environment).
stimuli
Hormone
A chemical messenger produced by a gland and carried in the blood to target organs.
Name some hormones and the glands that make them.
Pancreas — insulin and glucagon.
Adrenal glands — adrenaline.
Testes — testosterone.
Ovaries — oestrogen.
are chemical messengers carried in the blood to target organs.
Hormones
What are the effects of adrenaline?
Increases heart rate and breathing rate.
Increases blood glucose concentration.
Prepares the body for 'fight or flight'.
What does the hormone glucagon do (Extended)?
It is made by the pancreas.
It raises blood glucose by making the liver convert glycogen into glucose.
Compare nervous and hormonal responses.
Nervous responses are fast and short-lived, using electrical impulses.
Hormonal responses are slower and longer-lasting, using chemicals carried in the blood.
Homeostasis
The maintenance of a constant internal environment (within set limits) in the body.
Give examples of conditions controlled by homeostasis.
Body temperature, blood glucose concentration and water content.
Explain the principle of negative feedback (Extended).
If a level rises above the set point, a response brings it back down.
If a level falls below the set point, a response brings it back up.
How is a high blood glucose level brought back to normal (Extended)?
The pancreas releases insulin.
Insulin makes the liver convert glucose into glycogen for storage, lowering blood glucose.
How is a low blood glucose level brought back to normal (Extended)?
The pancreas releases glucagon.
Glucagon makes the liver convert glycogen back into glucose, raising blood glucose.
is the maintenance of a constant internal environment.
Homeostasis
The hormone lowers blood glucose by converting glucose into glycogen.
insulin
How does the body cool down when it is too hot (Extended)?
Sweating: sweat evaporates from the skin, taking heat from the body.
Vasodilation: blood vessels near the skin widen, so more blood flows near the surface and loses heat.
Hairs lie flat.
How does the body warm up when it is too cold (Extended)?
Shivering: muscles contract, releasing heat from respiration.
Vasoconstriction: blood vessels near the skin narrow, so less blood flows near the surface and less heat is lost.
Hairs stand up to trap an insulating layer of air.
When too hot, sweat from the skin, removing heat from the body.
evaporates
widens the blood vessels near the skin so more heat is lost.
Vasodilation
Which part of the body monitors and controls body temperature?
The brain (specifically the hypothalamus).
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