Biology Topic 8 Key Words

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nerve impulses

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conducted by the cells in the nervous system

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neurone

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single cell

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nerve

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group of neurons

more complex structure containing axons and lots of neurons

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cell body

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contains the nucleus and cell organelles within the cytoplasm

part of a neuron

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dendrites

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branched projections of a neuron that recieve the impulses and conducts them towards the cell body

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axon

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long single cell that transmits the impulse away from the cell body towards the terminal branches

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motor neurons

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conducts impulases from the central nervous system to the muscles and glands to allow movement

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sensory neurones

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carry impulses from the sensory cells to the central nervous system

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relay neurones

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found within the central nervous system

large number of connections with other nerve cells

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myelin sheath

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fatty insulating layer that neurones are covered in

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schwann cells

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makes up the myelin sheath

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photoreceptors

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light hits the receptors to stimulate nerve impulses to be passed along te optic nerve to the CNS

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Atropine

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used in the middle ages by women to make their pupils dilate

inhibits parasympathetic stimulation of the iros so the circular muscles of the iris relax

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acetylcholine

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used to dialte pupils for an eye examination

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reflex arcs

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simple nerve pathways

from sensory to relay to motor neurones

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refelxes

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rapid, involuntary responses to stimuli

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radial muscles

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controlled by sympathetic reflex

relax when pupils constrict and contract when pupils dilate

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circular muscles

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controlled by parasympathetic reflex

contracts when pupils constrict and relaxes when pupils dilate

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resting potential

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the axon is more negative than the outside

electrical gradient exactly balances the chemical gradient

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depolarisation

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the reversing of potential difference

inside of axon positive and outside negative

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repolarisation

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return to a resting potential of -70mv

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action potential

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large change in the voltage across the membrane

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positive feedback

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a change that encourages further change of the same sort

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hyperpolarisation

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potential difference more negative that the normal resting potential -80mv

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refractory period

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new action potential cannot be generated in same section of membrane for 5 miliseconds

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nodes of ranvier

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gaps in the myelin sheath where depolarisation takes place

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synapse

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where two neurones meet

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synaptic cleft

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gap between two neurones

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presynaptic membrane

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membrane of neurone that the impluse is coming from

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postsynaptic membrane

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membrane of neurone that is recieving the impulse across the synaptic cleft

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synaptic vesicles

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carry the neurotransmitters within the pre-synpatic neurone

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summation

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each impluse adds to the effect of others

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spatial summation

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impulses come from different synapses

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temporal summation

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several impulses arrive at synapse having travelled along a single neurone

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excitatory synapses

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make post-synaptic membrane more permeable to sodium ions

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inhibitory synapses

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make it less likely that an action potential shall result in the post-synaptic cell

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Plant growth substances

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chemicals used to coordinate plant growth

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auxins

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plant growth chemical that are found in the meristem cells that allow curving of the plant towards the light

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sense organs

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group of receptor cells

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chemoreceptors

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stimulated by chemicals and are involved in taste, smell and regulation of chemical concentrations in the body`

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mechanoreceptors

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stimulated by forces that stretch, compress or move the sensor and are involved in balance, touch and hearing

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photoreceptors

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stimulated by light and are involve in sight

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thermoreceptors

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stimulated by heat or cold and are involved in temperature control

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rods

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only allow black and white vision however can operate is bright or dim light

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cones

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allow colour vision in bright light

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ganglion neurones

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connects the optic nerve to the bipolar neurone cells

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bipolar neurone cells

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passes the impulse onto the cone and rod cells

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Rhodopsin

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purple pigment that allows vision in low light

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non-specific cation channels

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sodium ion channels that allow sodium ions to move in and out of rod cells

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glutamate

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neurotransmitter released from the rod cell

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dark adaptation

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reforming of rhodopsin

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phtochromes

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absorbs red and far-red light

can be used to work out how long the day is

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Pr

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absorbs red light and accumulates in night

shows how long the night is

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Pfr

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absorbs far-red light and accumulates in the day

shows how long day is

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photoperiod

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relative length of day and night - determines time of flowering

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Greening

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the changes a plants goes through when it reaches the sunlight

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grey matter

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what the outside layer of the brain is known as

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cortex

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accounts for two-thirds of the brains mass

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cerebral hemispheres

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the cortex id divided into the left and right cerebral hemispheres

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each hemispheres consists of which lobes?

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frontal lobe

parietal lobe

occipital lobe

temporal lobe

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white matter

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where two cerebral hemispheres meet made up of nerve axons

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thalamus

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responsible for routing all incoming sensory information to the correct part of the brain

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hypothalamus

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thermoregulatory centre

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hippocampus

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involved in laying down long-term memory

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basal ganglia

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collection of neurones deep within each hemisphere

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medulla oblongata

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regulates body processes that we don't control such as heart rate, blood pressure

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CT scans (computerised axial tomography)

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detect brain diseases and look at structures of the brain

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MRI scans (magnetic resonance imaging)

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uses magnetic field and radio waves to dianose tumours, strokes, brain injuries

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fMRI scans (functional magnetic resonance imaging)

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provides information about the brain in action - study human activities such as memory

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critical windows

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periods of time during postnatal development when the nervous system must obtain specific experiences to develop properly

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animal models

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knowledge on critical periods comes from the study of animals

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monocular deprivation

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depriving an organism of any light stimulus in one eye

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carpentered world hypothesis

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those who live in a world dominated by straight lines see different than those who live in a 'circular culture'

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habituation

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type of learning - allows animals to ignore unimportant stimuli

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animal welfare

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humans should treat animals well so far as possible

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ultilitarianism

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belief that the right course of action benefits the many

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dopamine

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neurotransmitter secreted by neurones

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artificial selection

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selects alleles for characteristic that are agriculturally valuable

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genetically modified plants

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genetic engineers introduce new genes with many alleles for desired characteristics into the plants DNA

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micropropagation

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multiplys a single cell to form a mass of plant cells which then differentiates to form plantlets