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36 Cards in this Set

  • Front
  • Back
Homeostasis
The maintenance of a relatively stable internal environment in the face of changes in either the external or internal environment
External environments
the medium immediatley surrounding an organism
Internal environments
also called extracellular fluid; is the fluid that surronds cells in multicellular organisms
Receptor
a structure that detects (or recieves) a stimulus or signal
Stimulus
a condition or signal that causes a response
Chemoreceptors
These are stimulated by specific chemicals in the external and internal environment
Mechanoreceptors
These are stimulated by anything that changes shape of the receptor
Photoreceptors
These detect light. In some animals they can also detect colour and form images
Thermoreceptors
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.
Pain Receptors
Free nerve endings in the skin
Sensory Neurons
These conduct messages from the receptors ot the central nervous system
Inter Neurons
These relay impulses form the sensory neurons ot the motor nerons. They are found in the CNS
Motor Neurons
These relay messages away from the CNS ot the effector organs, glands and muscles.
Cell body
(of neuron)
contains the nucleus and the cytoplasm of the cell. Messages recieved by the dendrites are sent to the cell body.
Axon
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.
Dendrites
Fine branching extensions of the neuron that conduct impulses toward the cell body and away from other cells
Synapse
The junction or gap between the end of one nueron and the start of the next. The axon releases neurotransmitters into the synapse
Neurotransmitter
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
Endocrine system
Consists of ductless (endocrine) glands- specialised cells that secrete hormones directly into the blood stream
Hormones
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
Hypothalamus Gland
Is in the brain, it is the main control centre that regulates hormonal messages to the pituitary gland
Pituitary Gland
Is know as the "master gland" and in turn passes 'messages' via hormones to target tissues around the body
Endothermic
Able to regulate their own heat through metabolic activity
Ectothermic
Depend on heat from their external environment
Homeothemric
Any animal that is able to mintain a relatively constant internal temperature
Poikilothermic
Organisms whose body temperature changes with that of their surroundings
Conduction
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
Convection
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
Evaporation
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.
Radiation
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
Hibernate
undergo a period of dormancy over long periods of cold conditions
Diapause
temporary suspension of bodily development and growth in response to adverse conditions; common in the development of embryos of kangaroos
Aestivation
dormancy in some animals during periods of drought
Hypertonic
is when there is a high concerntration of substances in the surrounding environments of an organism
Hypotonic
is when there is a low concerntration of substances in the surrounding environment of an organism
Isotonic
when the concertration in the organism and its surrounding environment is equal