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transmission of nerve impulse btwn CNS and PNS - Coggle Diagram
transmission of nerve impulse btwn CNS and PNS
Na+ ions are higher outside vs inside cell
K+ and negatively charged proteins inside cell
more positive outside, more negative inside: uneven distribution of positive and negative ions-diff in charge across membrane(polarised)
known as resting membrane potential
-70mV
maintained by sodium potassium pump-pump out 3 Na+, pump in 2 K+
concentration gradient created
action potential
reversal of resting membrane potential due to movement of ions in response to a stimulus, all or nothing manner
magnitude of action potential is always the same for the same cell type, stronger stimuli produce greater FREQUENCY of action potential
conduction is unidirectional
Depolarisation: stimulus arrives: a few Na+ channels open, some Na+ diffuse INTO cell, membrane potential brought to -50mV, more channels open
influx of Na+ neutralise -ve charge in cell, outside becomes less +ve
resting membrane potential reversed, inside +ve, outside -ve
at peak of action potential, Na+ channels close and K+ channels open, K+ start to leave cell
Repolarisation: K+ neutralise negative charge outside cell, inside become less +ve, outside less -ve
restores action potential, inside is -ve and outside is +ve
Hyperpolarisation:K+ continues to move out of channel briefly
K+ channels close at -80mV, resting potential restored and ready to respond to another stimulus
if local potential is large enough, membrane potential reaches threshold value causing further depolarisation(+20mV)
action potential
spreads
: action potential produced at one location can
stimulate production of action potential at an adjacent area
of the same plasma membrane
myelinated axon(spreads faster): saltatory conduction
gaps in myelin sheath called nodes of ranvier,
action potentials only occur at nodes of Ranvier
action potential
jumps from node to node
myelin sheaths
insulate axon, prevent generation
of action potential
myelination
increases speed and efficiency
of action potential generation along the axon
unmyelinated axon:continuous conduction
synapse: transmission of action potential from one cell to another
electrical synapse
chemical synapse
chemical synapse trnasmission
action potential in the presynaptic neuron will trigger Ca+ channel to open so Ca+ diffuse into presynaptic terminal
cause synaptic vesicles to bind to presynaptic membrane
release neurotransmitters to synaptic cleft
neurotransmitters bind to its receptors located on the postsynaptic membrane
triggers an action potential in the postsynaptic cell. Neurotransmitters degraded and reabsorbed by presynaptic neuron
reflex is an involuntary automatic response to a stimuli applied in the periphery and transmitted to CNS
-rapid, predictable, involuntary
occurs in spinal cord or brain stem
allows person to react faster than if conscious thought is involved
receptor detect painful stimulus
sensory neuron conduct action potential to spinal cord
sensory neuron synapse with interneuron that synapse with motor neuron
excitation of motor neuron leads to contraction of flexor muscle or withdrawal of limb from painful stimulus