Module 1: communication andhomeostasis

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is any change in the environment that causes a response.
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is a change in behaviour or physiology as a result of a chnage in the environment.
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is the maintenance of the internal environment in a constant state despite external chnages.
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Negative feedback
is a process that brings about a reversal of any change in conditions. It ensures that an optimum steady state can be maintainted, as the internal environment is returned to its original sset of conditions after any change. essential for homeostatis.
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Positive feedback
is a process that increases any chnage detected by the receptores. It tends to be harmful and does not lead to homeostasis.
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is an organism that relies on externaksurces of heat to regukate its body temperature.
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is anorganismthat can use internal sources of heat, such as heat generated from metabolism in the liver, to maintain its body temperature,
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membrane is one that has a potential difference across it. This is the resting potential.
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is the loss of polarisation across the membrane. It refers to the period when sodium ions are entering the cell making the inisde less negative with respect to the outside.
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Generator potential
is a small depolarisation caused by sodium ions entering the cell.
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Action potential
is achieved when the membrane is depolarised to a value of about -40mV. It is an all-or-nothing response. In the events leading upto an action potential, the membrane depolarises and reavhes a threshold level, then lots of sodium ions enter the axon.
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Resting potential
is the potential defferenceorvoltage across the neuron cell embrane while the neuron cell membrane while the neuron is at rest. It is about -60mVinside the cell compared with the outside.
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Volate-gated channels
are channels in the cell membranethat allow the passange of charged particles or ions. They havea mechanism called a gate which can open andd close the channel. In these channels the gates respond to chnages in the potnetial difference across the mem
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Threshold potential
is a potential difference caross the membrane of about -50mV. If the depolarisation of the membrane does not reavh the threshold potentialthen no action porntial is created. If the depolarisation reaches threshold potential and action potential occur
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Action potential
is a depolariastion of the cell membrane so that the inside is more positive than the outside, with a potential difference across the membrane of -40mV. This can be transmitted along the axon or dendron plasma membrane.
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Local currents
are the movements of ions along the neuron. Rhe 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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conduction means 'jumping conduction'. It refers to the way that the action potnetial appears to jumo form one node of Ranvier to the next.
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Neurotransmitter (transmitter substance)
is a chemical that diffuses across the cleft of the synapse to transmit a signal to the postsynaptic neuron.
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are those that use acetylcholine and their transmitter substance.
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Synaptic knob
is a swelling at the end of the presynaptic neuron.
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is anenzymein the synaptic cleft. It breaks sown the transmittersubstance acetylcholine.
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All or nothing
refers to the fact that a neuron either conducts an action potential or it does not.All action potentials arwthw same magnitude, +40mV.
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is a term that refers to the way that serveral small potential chnages can combine to produce one larger chnage in potential difference across the membrane.
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are molecules that are released by endocrine glands directly into the blood. They act as messengers, carrying a signal from theendocrine gland to specific target organ or tissue.
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Endocrine gland
is a gland that secretes hormones directly into the blood. Endocrine glands have no ducts.
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Exocrine gland
is a gland that secretes molecules into a duct that carries the moleules to where they are used.
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First messenger
is the hormone that transmits asignal around the body.
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Secondary messenger
is cAMP,ehich transmits a signal inside the cell
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Pancreatic duct
is a tube that collect all the secrestions form the exocrine cells in the pancreasand carries the fluid to the small intestine.
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islets of Langerhans
are small patchesof tissue in the pancreas that have an endocrine function. Alpha cells secrate glucagon and Beta cells secrete insuline.
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is the hormon, released from the pancreas, that causes blood glucose levels to go down.
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is the hormone that cuases blood glucose levels to rise.
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are liver cells. They are specialised to perform a range of metabolic functions.
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Diabetes mellitus
is a disease in which blood glucose concentrations cannot be controlled effectively.
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is the state in which the blood glucose concentration is too high(hyper=above, gly=glucose, aemia=blood).
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is the state in which the blood glucose concentration is too low(hypo-under)
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Genetically engineered
bacteria are those in which the DNA has been altered. In this case a gene coding for human insulin has been insertedinto DNA of bacteria.
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Stem cell
are unspecialised cells that have the potnetial to develop into any type of cell.
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Cell metabolism
is the result of all the chemical reactions taking place in the cytoplasm.
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muscle tissue can initiate its ownconcentration
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is a region of tissue in the right atrium wall tthat can generate an impulse andinitiate the concentartuon of chambers.
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Medulla oblongata
is found at the base of the brain. It is the reigon of the brain that coordinates the inconscience functionas of the bosy such as breathing rate and heart rate.
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Cardiovascular centre
is a specific regionof the medula oblongata that recieves sensory imputs about levels of physical activity, bloos carbon dioxide concentration and blood pressure. It sends nerve impuldes to the SAN in the heart to alter the frquencey of waves.
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is a change in behaviour or physiology as a result of a chnage in the environment.

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Negative feedback


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Positive feedback


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