Human response to the natural environment

receptor

structure that receives a stimulus and converts it into an impulse

effector

gland or organ that brings about a response to stimuli received by the body

stimulus

detectable change in the internal or external environment

impulse

electrical signal created by receptor organs in response to stimuli

autonomic system

controls involuntary bodily functions, and is made up of the parasympathetic and sympathetic nervous systems

peripheral nervous system

consists of nerves that extend outside the central nervous system

meninges

protective membranes surrounding brain and spinal cord

cerebrospinal fluid

fluid around the brain and spinal cord to aid in protection

cranium

part of the skull that contains and protects the brain

grey matter

part of the brain and spinal cord consisting of cell bodies and dendrites

white matter

part of the brain and spinal cord consisting of myelinated axons

neuron

specialised nerve cells which transmit nerve impulses

dendrites

fibres that transmit impulses to a cell body in a neuron

nerve

bundle of neurons

synapse

gap between the axon of one neruon and the dendrite of another

neurotransmitter

chemicals which carry impulses across the synapse

Homeostasis

tendency of living organisms to maintain their internal environment constant with narrow limits irrespective to external environmental changes

Alzheimer’s disease

disease caused by nerve defects, characterised by memory loss and confusion

multiple sclerosis

disease caused by damage to myelin sheath of neurons, characterised by physical and mental disabilities

rods

receptor cells in the retina of eyes, which are sensitive to dim light and help to distinguish between black and white

cones

receptor cells in the retina of the eye, which are sensitive to bright light and distinguish between different colours

pupil

central opening within the the iris, which allows light to enter

pupillary mechanism

regulation of pupil size to control amount of light entering the eye

Accomodation

ability of lens of the eye to alter its shape for clear vision when viewing both near and distant objects

Reflex action

a quick, automatic reaction response to a stimulus

Reflex arc

the pathway along which an impulse is transmitted to bring about a response to a stimulus during a reaction