Biology, Unit 2: Chapter 8

Front 1

Homeostasis

Back 1

The maintenance of a relatively stable internal environment in the face of changes in either the external or internal environment

Front 2

External environments

Back 2

the medium immediatley surrounding an organism

Front 3

Internal environments

Back 3

also called extracellular fluid; is the fluid that surronds cells in multicellular organisms

Front 4

Receptor

Back 4

a structure that detects (or recieves) a stimulus or signal

Front 5

Stimulus

Back 5

a condition or signal that causes a response

Front 6

Chemoreceptors

Back 6

These are stimulated by specific chemicals in the external and internal environment

Front 7

Mechanoreceptors

Back 7

These are stimulated by anything that changes shape of the receptor

Front 8

Photoreceptors

Back 8

These detect light. In some animals they can also detect colour and form images

Front 9

Thermoreceptors

Back 9

These detect external heat and cold through receptors near the surface and internal body temp. depper in the body by receptors in the major arteries and hypothalamus.

Front 10

Pain Receptors

Back 10

Free nerve endings in the skin

Front 11

Sensory Neurons

Back 11

These conduct messages from the receptors ot the central nervous system

Front 12

Inter Neurons

Back 12

These relay impulses form the sensory neurons ot the motor nerons. They are found in the CNS

Front 13

Motor Neurons

Back 13

These relay messages away from the CNS ot the effector organs, glands and muscles.

Front 14

Cell body
(of neuron)

Back 14

contains the nucleus and the cytoplasm of the cell. Messages recieved by the dendrites are sent to the cell body.

Front 15

Axon

Back 15

an elongated section of the cell body that conducts impulses away from the cell body and tansmits messages to other cells. Axons vary in length and branching.

Front 16

Dendrites

Back 16

Fine branching extensions of the neuron that conduct impulses toward the cell body and away from other cells

Front 17

Synapse

Back 17

The junction or gap between the end of one nueron and the start of the next. The axon releases neurotransmitters into the synapse

Front 18

Neurotransmitter

Back 18

Chemical released by the axon into the synapse, whihc diffuses across to the dendrites of the other neuron. Receptors on the dendrites combine with neurotransmitters and triger a nerve impulse in the next neuron

Front 19

Endocrine system

Back 19

Consists of ductless (endocrine) glands- specialised cells that secrete hormones directly into the blood stream

Front 20

Hormones

Back 20

Are specialised chemicals produced in minute amounts tht are involved in the regulation of many body processes. They circulate in the bloodstream but can only be detected by specific receptors on particular cells.

Hormone responses can be slow acting but its effects may be long lasting

Front 21

Hypothalamus Gland

Back 21

Is in the brain, it is the main control centre that regulates hormonal messages to the pituitary gland

Front 22

Pituitary Gland

Back 22

Is know as the "master gland" and in turn passes 'messages' via hormones to target tissues around the body

Front 23

Endothermic

Back 23

Able to regulate their own heat through metabolic activity

Front 24

Ectothermic

Back 24

Depend on heat from their external environment

Front 25

Homeothemric

Back 25

Any animal that is able to mintain a relatively constant internal temperature

Front 26

Poikilothermic

Back 26

Organisms whose body temperature changes with that of their surroundings

Front 27

Conduction

Back 27

is the transfer of heat energy from a hotter object to a cooler object with which it is in contact. If you get cold, to get warmer you may snuggle up to someone who is warm

Front 28

Convection

Back 28

is the transfer of heat by means of warmed air, or water, rising and being replaced by cooler air or water. Air and water movements help distribute heat energy and speed up loss of heat by conduction and evaporation

Front 29

Evaporation

Back 29

is the process by which water changes from liquid to vapour. For this to occur, heat is required. It is the heat of the object or body which enables evaporation to take place, resulting in a cooling effect.

Front 30

Radiation

Back 30

is the transfer of heat from a hot body or object to a cooler one by means of infra-red waves. As much as 25% of the heat lost by a person sitting in a room at 21 degress celcius may be caused by radiation

Front 31

Hibernate

Back 31

undergo a period of dormancy over long periods of cold conditions

Front 32

Diapause

Back 32

temporary suspension of bodily development and growth in response to adverse conditions; common in the development of embryos of kangaroos

Front 33

Aestivation

Back 33

dormancy in some animals during periods of drought

Front 34

Hypertonic

Back 34

is when there is a high concerntration of substances in the surrounding environments of an organism

Front 35

Hypotonic

Back 35

is when there is a low concerntration of substances in the surrounding environment of an organism

Front 36

Isotonic

Back 36

when the concertration in the organism and its surrounding environment is equal