Homeostasis 1

The [blank_start]regulation[blank_end] of the internal conditions of a [blank_start]cell or organism[blank_end] to maintain [blank_start]optimum[blank_end] conditions for [blank_start]function[blank_end], in response to internal or external [blank_start]changes[blank_end].

Controlled internal conditions include: - [blank_start]thermoregulation[blank_end] - [blank_start]osmoregulation[blank_end] - [blank_start]blood glucose concentration[blank_end]

Receptors: cells that [blank_start]detect changes[blank_end] may be in the [blank_start]nervous system[blank_end] or [blank_start]hormonal control centres[blank_end]

Coordination centres: areas that [blank_start]receive and process information[blank_end] from receptors includes the [blank_start]brain[blank_end], [blank_start]spinal chord[blank_end] and [blank_start]pancreas[blank_end]

Effectors: [blank_start]muscles or glands[blank_end] that bring about response respond to received stimulus restore conditions to optimum through [blank_start]chemical or physical[blank_end] changes

The nervous system carries impulses between [blank_start]1-120[blank_end] metres per second

Stimulus | Receptor | ([blank_start]sensory neurones[blank_end]) Coordinator ( [blank_start]Central Nervous System[blank_end] ) | ([blank_start]motor neurones[blank_end]) Effector ( [blank_start]muscles[blank_end] may contract [blank_start]glands[blank_end] may secrete chemicals )

The [blank_start]receptor[blank_end] sends an impulse along a [blank_start]sensory neurone[blank_end], carrying information about a change in the environment to the coordinator ([blank_start]CNS[blank_end]). Once all incoming information has been processed, the coordinator sends an impulse along the [blank_start]motor neurones[blank_end], which stimulate the [blank_start]effectors[blank_end] needed in a particular circumstance.

Experiments to measure reaction times: - [blank_start]ruler drop test[blank_end] ( reaction to visual stimulus ) - hand squeeze around circle ( [blank_start]reaction to physical stimulus[blank_end] )