List of key words for communication and homeostasis (Unit 1 Module 1 OCR)

List of key  words for communication and homeostasis (Unit 1 Module 1 OCR)

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  • Created on: 08-05-11 20:48
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Unit 1 Module 1 Key Words
STIMULUS: Any change in the environment that causes a response
RESPONSE: Change in behaviour or physiology due to environment
NEURONAL SYSTEM: Interconnected network of neurones that signal to
each other across synapse junctions
HORMONAL SYSTEM: Where the blood transports chemical signals
HOMEOSTASIS: Maintenance of the internal environment in a constant
state , despite external changes
NEGATIVE FEEDBACK: A process that brings about a reversal of a change
in conditions. Essential for homeostasis
POSITIVE FEEDBACK: A process that increases any change detected by
receptors, leads away from homeostasis
EFFECTOR CELLS: React to a signal from receptor cells to reverse a
change in conditions
ECTOTHERMS: Cold-blooded. An organism that relies on external
sources of heat (usually the sun) to regulate its body temperature
ENDOTHERMS: Warm-blooded. An organism that can maintain its body
temperature independent of external temperature. They use internal
sources of heat (respiration)
PRECAPILLARY SPHINCTERS: Regulate blood flow to capillaries by
opening and closing
HYPOTHALMUS: Monitors temperature of blood and sends signals to
reverse changes
SENSORY RECEPTORS: Specialised cells that detect changes in
POLARISED MEMBRANE: One that has a potential difference across it ­
resting potential
DEPOLARISATION: Loss of polarisation across membrane when sodium
ions are entering the cell
GENERATOR POTENTIAL: Small depolarisation caused by sodium ions
entering the cell, may lead to an action potential
ACTION POTENTIAL: Achieved when the membrane is depolarised to
+40mV. This is the signal that travels through the CNS.
MYELIN SHEATH: Fatty sheath that insulates neurones from the
electrical activity in nearby cells. Made up of individual Schwann cells.

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AXON: The long part of a motor neurone that carries the action potential
to the effector
DENDRON: The long part of a sensory neurone that carries the action
potential from the receptor to the CNS and motor neurones
RESTING POTENTIAL: The p.d across the neurone cell membrane when it
is at rest. About -60mV.
VOLTAGE GATED CHANNELS: Channels in the cell membrane that allow
the passage of ions/charged particles. They respond (open/close) to
changes in the p.d across the cell membrane

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EPSP: Excitatory postsynaptic potential, the potential difference
created at the postsynaptic membrane, can generate a new action
SYNAPTIC CLEFT: The gap between two neurones (between the
presynaptic knob and the postsynaptic membrane)
ACETYLCHOLINESTERASE: Enzyme in the synaptic cleft that breaks
down the neurotransmitter acetylcholine molecules, to stop more than
one action potential forming at the post synaptic membrane
SUMMATION: Several small potential changes combine to produce one
larger change
ENDOCRINE GLAND: Gland that secretes hormones directly into the
EXOCRINE GLAND: Secrete molecules through…read more


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