Neuronal communication Flashcards
what are neurones
nerve cells that play an important role in coordinating communication within the nervous system
what is the structure of neurones
.all have a cell body with nucleus and organelles like mito and cyto
.extensions called dendrites which conducts impulses towards cell body
.axons conduct impulses away from cell body
what are the types of neurones
sensory, motor and relay
what does the motor neurone do
transmits electrical impulses from CNS to muscles
what does the sensory neurone do
transmits impulses from receptors to the CNS
what does the relay neurone do
in the CNS, it transmits impulses from sensory to motor neurone
what are the charges of a neurone in rest
outside of membrane is positive
inside of membrane is negative
.this allows neurones to carry electrical impulses called action potentials
what does the myelin sheath do
.insulates axons and dendrons
.produced by Schwann cells
.increases the speed of electrical potential being carried(saltatory conduction)
.action potential jumps between gaps in the myelin sheath called nodes of Ranvier
why are nerve cells polarised during rest
.due to the imbalance between sodium and potassium ion
.resting potential = -70mV
how is the resting potential generated and maintained
.by the sodium-potassium pump
.moves sodium ions out of neurone creating a electrochemical gradient due to membrane not being permeable to sodium ions
.S/P pump also pumps P into the neurone but is diffuses out due to P ion channels
.resulting with the outside being positive due to imbalance of positively charged ions
what happens when the neurone is stimulated
.neurone cell membrane becomes depolarised
1.excitation of neurone cell triggered by stimulus and causes sodium ion channels to open making it more permeable to sodium ions so they diffuse into the neurone down the electrochemical gradient
.inside less negative
2.once reaching -55mV, more S channels open eventually giving a potential diif of +30mV = end of depolarisation
3.repolarisation is achieved due to S channels closing and P channels opening
.p ions diffuse out of neurone down the conc gradient and eventually restoring the resting potential
4.p channels close slowly causing hyperpolarisation so SP pump is used to restore the potential difference to -70mV (resting)
what is the refractory period
short period of time where neurone membrane cannot be excited again due to sodium channels recovering
what are synapse
.junctions between two neurones
what happens when action potential reaches a synapse
.presynaptic membrane depolarises causing the calcium ion channels to open allowing C ions to enter the neurone
.neurone then causes the fusion of synaptic vesicles filled with neurotransmitters like acetylcholine to fuse with the presynaptic cleft
.neurotransmitter diffuse across the cleft and bind to the receptors on the postsynaptic membrane
.therefore stimulating the opening of cation channels enabling S ion to enter the neurone
.post-synaptic membrane depolarises so triggering another action potential
how does the previous cycle controlled
with digestive enzymes in the synaptic cleft which break down neurotransmitters to prevent overstimulating of the post synaptic membrane
