How do cells pass messages on?

Two ways cells pass on messages?

1. between neurons (synaptics transmission, chemical)

2. within the neuron (action potential, electrical)

What is synaptic transmission?

concerns the nervouse system and how messages are passed between individual nerves

what are neurotransmitters?

chemicals that are released from a synaptic vesicle into the synapse by neurons

how do neurotransmitters work?

affect the transfer of an impulse to another nerve or muscle.

then once finished it is broken down by an enzyme, turning them off.

parts of these NTs are taken back up into the terminal buttons of neurons through the process of reuptake where they are recombined in vesicles and ready to be released again.

what is the lock and key model?

NT molecules have specific shapes (key)

Receptor molecules have binding sites (lock)

when NT binds to receptor, ions enter (door opens)

4 types of neurotransmitter

• adrenaline - fight or flight

• dopamine - pleasure

• serotonin - mood

• GABA - calming

What can synaptic connections either be?

excitatory or inhibitory, difference lies in the action of neurotransmitter at postsynaptic receptor

excitatory NTs?

increase charge in postsynaptic neuron (e.g. adrenaline)

inhibitory NTs?

reduce the charge in the postsynaptic neuron (e.g. GABA)

What is the process of synaptic transmission? (x7 steps)

1. nerve impulse (action potential) travels down an axon

2. action potential reaches synaptic terminal

3. this triggers the release of NTs into the synapse

4. the NT travels across the synapse via a concentration gradient (high to low)

5. the NT binds with receptors on the dendrite of the adjacent neuron via lock and key

6. if the NT is excitatory, an action potential is more likely to fire, if inhibitory, action potential is less likely to fire

7. the NT disconnects from the dendrite of the postsynaptic neuron and is taken up by the presynaptic neuron

what is action potential?

an electrical impulse used by neurons and muscle cells to transmit information and signals throughout the body

how does action potential work? (x4 steps)

1. Resting potential of a neuron is -70mV

2. when NTs bind to dendrites of a neuron this causes some channels in the neuron cell body to open and charged ions to enter. If NT is excitatory, positively charged ions enter the postsynaptic neuron, if NT is inhibitory, negatively charged ions enter the postsynaptic neuron

3. If the cumulative charge in the cell body reaches -55mV, the threshold for an action potential has been reached and an action potential fires.

4. This causes an electrical signal to be sent along the entire length of the neuron.

How is action potential affected if the neuron has a myelin sheath?

electrical signal is sent more quickly because it effectively jumps along the axon via each node of ranvier