Communication and Homeostasis Flashcards Preview

Biology F214 > Communication and Homeostasis > Flashcards

Flashcards in Communication and Homeostasis Deck (47):
1

Stimulus

Any change in the environment that causes a response.

2

Response

Change in behaviour or physiology as a result of a change in the environment.

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Homeostasis

Maintenance of the internal environment in a constant state despite external changes.

4

Negative feedback

Process that brings about the reversal of any change in conditions. It ensures that an optimum steady state can be maintained, as the internal environment is returned to its original set of conditions after any change. Essential for homeostasis.

5

Positive feedback

Process that increases any change detected by receptors. Tends to be harmful (except in pregnancy and dilation of cervix) and does not lead to homeostasis.

6

Ectotherm

Organism that relies on external sources of heat to regulate its body temperature.

7

Endotherm

Organism that can use internal sources of heat, such as heat generated from metabolism in the liver, to maintain its body temperature.

8

Polarised membrane

One that has a potential difference across it.

9

Depolarisation

Loss of polarisation across the membrane. Refers to the period when sodium ions are entering the cell, making the inside less negative with respect to the outside.

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Generator potential

Small depolarisation caused by sodium ions entering the cell.

11

Action potential

Achieved when the membrane is depolarised to a value of around +40mv. It is an all or nothing response.

12

Resting potential

Potential difference or voltage across the neurone cell membrane while the neurone is at rest. At -60mv inside the cell compared with the outside.

13

Voltage-gated channels

Channels in the cell membrane that allow the passage of charged particles and ions. They respond to changes in the potential difference across the membrane.

14

Threshold potential

Potential difference across the membrane is -50mv. If depolarisation reaches threshold potential, an action potential is created.

15

Action potential

Depolarisation of cell membrane so that inside is more positive than outside. Potential difference is +40mv. Action potential can be transmitted along the axon or dendron plasma membrane.

16

Local currents

Movements of ions along the neurone. Flow of ions is caused by an increase in concentration at one point, which causes diffusion away from the region of higher concentration.

17

Saltatory conduction

Way that the action potential appears to jump from one node of Ranvier to the next.

18

Neurotransmitter (substance)

Chemical that diffuses across the cleft of the synapse to transmit a signal to the postsynaptic neurone.

19

Cholinergic synapses

Those that use acetylcholine as their transmitter substance.

20

Synaptic knob

Swelling at the end of the presynaptic neurone.

21

Acetylcholinesterase

Enzyme in the synaptic cleft that breaks down acetylcholine.

22

All or nothing

Refers to the fact that a neurone either conducts an action potential or it does not. All action potentials are of the same magnitude of +40mv.

23

Summation

Several small potential changes can combine to produce one larger change in potential difference across the membrane.

24

Hormone

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/tissue.

25

Endocrine gland

Gland that secretes hormones directly into the blood. Have no ducts.

26

Exocrine gland

Gland that secretes molecules into a duct that carries the molecules to where they are used.

27

Target cells

Those that possess a specific receptor on their plasma membrane. Shape of receptor is complementary to shape of hormone molecule.

28

Adenyl cyclase

Enzyme associated with the receptor for many molecules, including adrenaline. It is found on the inside of the cell surface membrane.

29

The first messenger

Hormone that transmits a signal around the body.

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The second messenger

Cyclic AMP, which transmits a signal inside the cell.

31

Pancreatic duct

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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What do alpha cells secrete?

Hormone Glucagon

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What do beta cells secrete?

Hormone Insulin.

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Insulin

Hormone that causes blood glucose levels to go down.

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Glucagon

Hormone that causes blood glucose levels to rise.

37

Hepatocytes

Liver cells. They are specialised to perform a range of metabolic functions.

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Diabetes mellitus

Disease in which blood glucose concentrations cannot be controlled effectively.

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Hyperglycaemia

State in which the blood glucose concentration is too high.

40

Hypoglycaemia

State in which the blood glucose concentration is too low.

41

Genetically engineered bacteria

Bacteria whose DNA have been altered. E.g. A gene coding for human insulin has been inserted into DNA of bacteria.

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Stem cells

Unspecialised cells that have the potential to develop into any type of cell.

43

Cell metabolism

Result of all the chemical reactions taking place in the cytoplasm.

44

Myogenic

Muscle tissue that can initiate its own contractions.

45

Pacemaker

Region of tissue in the wall of right atrium that can generate an impulse and initiates the contraction of the chambers.

46

Medulla oblongata

Found in base of brain. Region of the brain that coordinates the unconscious functions of the body such as breathing rate and heart rate.

47

Cardiovascular centre

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.