Unit 1, Module 1 Glossary Flashcards
Stimulus
Any change in the environment that causes a response
Cell Signalling
The process by which cells communicate with each other. This is a process in which one cell will release a chemical that is detected by another cell. The second cell will respond to the signal by the first cell.
Response
A change in behaviour or physiology as a result of a change in the environment.
Homeostasis
The maintenance of the internal environment in a constant state despite external changes.
Negative Feedback
A process in which any change un a parameter brings about the reversal of that change so the parameter is kept fairly constant.
Positive Feedback
A process in which any change in a parameter brings about an increase in that change.
Oxytocin
A hormone released by posterior pituitary gland to facilitate birth and breast feeding.
Ectotherm
An organism that relies on external sources of heat to regulate its body temperature
Endotherm
An organism that can use internal sources of heat, such as heat generated from metabolism in the liver, to maintain its body temperature.
Polarised
A membrane that has a potential difference across it. This is the resting potential
Depolarisation
The loss of polarisation across the membrane. It refers to the period when sodium ions are entering the cell making the inside less negative with respect to the outside.
Generator potential
A small depolarisation caused by sodium ions entering the cell.
Action potential
A brief reversal of the resting potential across the cell surface membrane of a neurones all action potential have a value of +40mV
Resting potential
The potential difference. Or voltage across the neurone cell membrane while the neurone is at rest.
Voltage-gated channels
Channels in plasma membranes that allow the passage of ions, they respond to changes in potential difference across a membrane and as a result open or close.
Threshold potential
A potential difference (usually -50mV) across the membranes if the Depolarisation of the membrane does not reach the threshold potential then no action potential is created. If the depolarisation reaches the threshold potential then more sodium ion channels open and an action potential is created.
Hyper polarised
The condition of a membrane that is mor highly polarised than the usual resting state,my resting potential is lower than usual.
Polarised
Membrane with a potential difference across it.
Depolarisation
The loss of polarisation across a membrane - when a membrane loses its resting potential
Refractory period
The short period of time after firing during which it is more difficult to stimulate a neurone.
Local currents
The movements of ions along the neurone. The flow of ions is caused un an increase in concentration at one point, which causes diffusion away from the region of high concentration.
Saltatory
Refers to the way. That the action potential appears to jump form one more of Ranvier to the next.
Neurotransmitter
A chemical that diffuses across the cleft of the sun apse to transmit a signal to the postsynaptic neurone.
Cholinergic synapses
Those that use acetylcholine as their transmitter substance.
Synaptic knob
A swelling at the end of the presynaptic neurone.
Acetylcholinesterase
An enzyme in the synaptic cleft. It breaks down the transmitter substance acetylcholine.
All or nothing
Refers to the fact that a neurone either conducts an. Action potential or does not. All action potential are of the same magnitude +40mV.
Summation
A term that refers to the way that several small potential changes can combine to produce one larger change in potential difference across the membrane.
Hormones
Molecules that are released by endocrine glands directly into the blood. They act as messengers, carrying a signal from the endocrine gland to a specific target organ or tissue.
Endocrine gland
A gland that secretes hormones directly into the blood. Endocrine glands have no ducts.
Exocrine gland
A gland that secretes molecules into a duct that carries the molecules to where they are used.
Target cells
Those that possess a specific receptor in their plasma membrane. The shape of the shape is complementary to the shape of the hormone molecule, many similar cells together form a tissue.
Adenyl cyclase
An enzyme associated with the reception for many hormones, including adrenaline. It is found on the inside of the cell surface membrane.
First messenger
A hormone that acts as a message in the blood.
Second messenger
A chemical inside the cell released in response to a hormone binding to the cell surface membrane, e.g. cAMP.
Pancreas
A small organ in the abdomen that secretes digestive fluids and hormones.
Pancreatic duct
A duct leading from the pancreas to carry digestive juices to the small intestine.
Islets of Langerhans
Small patches of tissue in the pancreas that have an endocrine function.
Alpha cells
Cells in the islets of Langerhans hat release glucagon in response to low blood glucose levels.
Beta cells
Cells in the islets of Langerhans that release insulin in response to high blood glucose levels.
Insulin
The hormone, released from the pancreas, that cause blood glucose levels to go down.
Glucagon
The hormone that cause blood glucose levels to rise.
Hepatocytes
Liver cells. They are specialised to perform metabolic functions.
Diabetes mellitus
A disease in which blood glucose concentrations cannot be controlled effectively.
Hyperglycaemia
The state in which the blood glucose concentration is too high.
Hypoglycaemia
The state in which blood glucose concentration is too low.
Genetically engineered
Bacteria whose DNA has been altered. In this case a gene coding for human insulin has been inserted into the DNA of the bacteria.
Stem cells
Unspecialised cells that have the potential to develop into any type of cell.
Cell metabolism
The result of all the chemical reactions taking place in the cytoplasm
Myogenic
Theses muscle tissues can initiate its own contractions
Pacemaker
The region of tissue in the right atrium wall that can generate an impulse and initiates the contraction of the chambers
Medulla oblongata
It is found at the base of the brain. It is the region of the brain that coordinates the unconscious functions of the body such as the breathing rate and heart rate.
Cardiovascular centre
A specific region of the medulla oblongata that receives sensory inputs about levels of physical activity, blood carbon dioxide concentration and blood pressure. It sends nerve impulses to the SAN in the heart to alter the frequency of excitation waves.
