neuronal communication Flashcards
structual components of neurones
.cell body- contains nucleus, mito, and ER
.axon- the single long fibre that carries impulses away from the cell body to other neurones/effectors
dendrons- short branches from the cell body that split into shorter dendrites that receive impulses from other neurones and transmit them towards the cell body
function of schwann cells
.forms myelin sheath
.remove debris via phagocytosis
.aid regeneration
function of myelin sheath
surrounds parts of axon acting as an insulator preventing the passage of ions into/out of those parts
.causing impulses to jump between the gaps called nodes of Ranvier = increased speed
function of sensory neurone
.carries impulses from sensory receptors to CNS
.
function of relay neurone
carries impulses within the CNS between the sensory and motor neurones
function of the motor neurone
carries impulses from CNS to effectors
typical pathway of an impulse
.receptor, sensory, relay, motor, effector
genetration of an action potential
.membrane is polarised at -70mV
STIMULUS
.stimulus causes voltage-gated Na+ channels to open
.more sodium ions flow into axon making the inside less negative
DEPOLARISATION
.when threshold potential of -55mV is reached, more sodium ion channels open causing more sodium ions to enter
REPOLARISATION
.at +30mV the sodium ion channels close and potassium ion channels open
.causing potassium ions to flow out of the axon and so the membrane starts to repolarise
HYPERPOLARISATION
.the excess of K+ leaves the axon causing the potential to be below the resting potential
.ion pumps and channels work together to restore the membrane back to resting potential
how is the generation of the action potential an example of a positive feedback
the Na+ entering the axon depolarises it and so opening more Na+ channels
all-or-nothing principle
.if the threshold is hit then there will always be a action potential with it being the same size
.stronger stimulus = more frequent AP
roles of refractory period
.ensuring that there is only one AP at a time
.limiting frequency of AP transmitted
.ensures one way directional travel of AP
factors affecting speed of transmission of an action potential
.myelination
.axon diameter = larger = less resistance to ion flow = faster
.temp = higher = faster diffusion of ions
.above 40 = denature
function of synapses
.junction between neurones where information is transferred from one to another/effector
structures of the synape
synaptic knob- at the end of the presynaptic neurone that contain organelles needed for neurotransmitter production e.g. mito
.synaptic vesicles- store neurotransmitters
synaptic cleft- gaps between the pre and postsynaptic membrane
neurotransmitter receptors- bind to neurotransmitters
excitatory/inhibitory synapes
.excitatory causes depolarisation and may cause a AP
e.g. acetylcholine in the CNS
inhibitory causes hyperpolarisation and prevents AP
e.g. acetylcholine in cardiac synapses
spatial summation
.multiple presynaptic neurones converge on a single postsynaptic neurone
.combined input of neurotransmitters triggers the postsynapse
temporal summation
.repeated firing of neurotransmitters from one presynaptic neurone to a postsynaptic neurone
synaptic transmission
.AP arrives at the presynaptic knob
.causes voltage-gated Ca2+ channels to open
.calcium ions flow into presynaptic knob
.causing the synaptic vesicles to fuse with the presynaptic membrane
.neurotranmitters are released into the synaptic cleft via exocytosis and diffuse across to the postsynaptic membrane
.at the postsynaptic membrane the neurotransmitters bind to the neurotransmitter receptors causing them to change shape
.this opens sodium ion channels in the postsynaptic membrane leading to the depolarisation of the membrane
cholinergic synapse transmission
.ACh is the transmitter
.after ACh binds to postsynaptic it is broken down by acetylcholinesterase into choline and acetate
.they are reabsorbed into the presynaptic knob via AT
.they are recycled to synthesise more ACh
