Unit 4 - Communication and Homeostasis Key Words

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  • Created by: Sofalof
  • Created on: 08-05-15 19:22
Stimulus
Any change in the environment that causes a response
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Response
A change in behaviour or physiology as a a result of a change in the environment
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Homeostasis
The maintainance of the internal environment in a constant state despite external changes
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Negative feedback
A process that brings about a reversal of any change in conditions
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Positive feedback
A process by which any change detected by receptors is increased
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Ectotherm
An organism that relies on external sources of heat to regulate its body temperature
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Endotherm
An organism that can use internal sources of heat, such as heat generated from metabolism in the liver, to maintain its body temperature
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Generator potential
A small depolarisation caused by sodium ions entering the cell
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Action potential
Achieved when the membrane is depolarised to a value of about +40mV. It is an all-or-nothing response
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Resting potential
The potential difference/voltage across a neurone cell membrane while it's at rest
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Voltage-gated ion channels
Channels in the cell membrane that allow the passage of charged particles or ions. They have a mechanism called a gate which can open and close the channel. In these channels the gates respond to changes in potential difference across the membrane
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Threshold potential
A potential difference across the membrane of about -50mV. If the depolarisation of the membrane does not reach the threshold potential then no action potential is created
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Polarised membrane
One that has a potential difference across it
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Depolarisation
The loss of polarisation across the membrane
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Local currents
The movement of ions along the neurone. The flow of ions is caused by an increase in concentration at one point, which causes diffusion away from the region of higher concentration
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Saltatory conduction
Jumping conduction. The way that the action potential appears to jump from one node of Ranvier to the next
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Neurotransmitter
A chemical that diffuses across the cleft of the synapse to transmit a signal to the postsynaptic neurone
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Cholinergic synapses
Those that use acytlcholine as their transmitter substance
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Synaptic knob
A swelling at the end of the presynaptic neurone
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Acetylcholinesterase
An enzyme in the synaptic cleft. It breaks down the transmitter substance acytlcholine
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All-or-nothing
The fact that a neurone either conducts an action potential or it does not
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Summation
The way that several small potential changes can contribute to produce one larger change in potential difference across the membrane
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Hormones
Molecules that are released by endocrine glands directly into the blood. They act as messengers
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Endocrine gland
A gland that secretes hormones directly into the blood. They have no ducts
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Exocrine gland
A gland that secretes molecules into a duct that carries the molecules to where they are used
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Target cells
Cells that possess a specific receptor on their plasma membrane
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Adenyl cyclase
An enzyme associated with the receptor for many hormones. It is focused on the inside of the plasma memberane
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First messenger
The hormone that transmits a signal around the body
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Second messenger
cAMP, which transmits a signal inside the cell
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Pancreatic duct
A tube that collects all the secretions from the exocrine cells in the pancreas and carries the fluid to the small intestine
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Islets of Langerhans
Small patches of tissue in the pancreas that have an endocrine function
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Alpha cells
Secrete glugagon
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Beta cells
Secrete insulin
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Insulin
A hormone released by the pancreas that causes blood glucose levels to go down
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Glugagon
A hormone released by the pancreas that causes blood glucose levels to rise
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Diabetes mellitus
A disease in which blood glucose concentrations cannot be controlled effectively
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Hyperglycaemia
The state in which blood glucose concentration is too high
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Hypoglycaemia
The state in which the blood glucose concentration is too low
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Stem cells
Unspecialised cells that have the potential to develop into any type of cell
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Genetically engineered bacteria
Those in which the DNA has been altered
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Cell metabolism
The result of all the chemical reactions taking place in the cytoplasm
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Myogenic muscle tissue
Can initiate its own contractions
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Pacemaker
A region of tissue in the right atrium wall that can generate an impulse and initiates the contraction of the chambers
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Medulla oblongata
The region of the brain that coordinates the unconcious functions of the body such as breathing rate and heart rate
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Cardiovascular centre
A specific region of the medulla oblongata that receives sensory inputs and sends nerve impulses to the SAN to alter the heart rate
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Other cards in this set

Card 2

Front

A change in behaviour or physiology as a a result of a change in the environment

Back

Response

Card 3

Front

The maintainance of the internal environment in a constant state despite external changes

Back

Preview of the back of card 3

Card 4

Front

A process that brings about a reversal of any change in conditions

Back

Preview of the back of card 4

Card 5

Front

A process by which any change detected by receptors is increased

Back

Preview of the back of card 5
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