C2.2 Neural signalling Flashcards
The nervous system consists of
nerve cells called neurone, which help with internal communication by transmitting nerve impulses (electrical impulses)
An impulse is..
a momentary reversal in electrical potential difference in the membrane – a change in the position of charged ions between the inside and outside of the membrane of the nerve fibres
Neuron structure (3)
Cell body (cytoplasm and nucleus), Dendrites (short branches), Axon (elongated nerve fibre)
A nerve impulse is a result of…
a change in concentration of sodium (Na+) and potassium (K+) ions along the cell membrane
Sodium-potassium pumps in the membrane…
transport Na+ out and K+ into the membrane (active transport, unequal amount (3 Na+, 2 K+), imbalance of concentration gradients)
Nerve impulses as action potentials (2 stages)
Membrane potential is reversed by Na+ rushing into cell. 1. Action potential is generated when membrane becomes positive. 2. Repolarisation: charge returns to normal when K+ moves out
Variation in the speed of nerve impulses
In humans 1m per second (due to small diameter), larger animal and diameter = faster due to less resistance
Myelination of axon fibres
A lipid-rich substance surrounding the nerve that increases transmission of action potential
A synapse + three types
a junction between two cells in a nervous system, 1. synapses between neurons, 2. synapses between neurons and muscle fibres, 3. synapses between neurons and glands
Crossing the synaptic cleft
Neurotransmitters are released from the presynaptic cleft and impulse is carried by neurotransmitters
Generation of an excitatory postsynaptic potential
postsynaptic membrane contains specialised receptors (protein channels embedded in cell membrane) –> chemical gated receptors allow Na+ to rush into the neutron after neurotransmitter binds to binding site on neuroreceptor
One of the most common neurotransmitters
Acetylcholine
