neuronal transmission Flashcards
define the structure of a neurone.
dendrites - recipient of information from other neurones
soma - involved in controlling processing in the cell and integrates information
axon - carries information from the soma to the terminal boutons
terminal boutons - communication point with other neurone
what is the function of the neural membrane?
- separates the extracellular env from the intracellular env
what do protein structures do?
detect substances outside the cell, allow access of certain substances into the cell.
what figure indicates the RMP?
-65 to -75mV (inside the cell, more negatively charged).
what causes there to be a membrane potential?
the movement of particles across a membrane due to diffusion and and electrostatic pressure.
define diffusion.
- molecules move from an area of high concentration to an area of low concentration.
salt spilts into which particles?
Na+ and Cl-
describe how the equilibrium potential is reached?
- P+ ions move across membrane by diffusion force, as P+ ions move there is an increase in electrical potential across the membrane (more +ve on one side, more -ve on the other).
- eventually a point is reached when the diffusion force = electrostatic force (EP)
which particles are mostly located outside the neurone? and which ones are mostly inside?
sodium (Na+) are mostly outside and want to get in, whereas potassium (K+) is mostly inside so wants to get out.
describe the RMP steps.
- high conc of Na+ outside neurone, high conc of K+ inside neurone
- at rest, more K+ channels open than Na+ channels.
- Na+ move into neurone and K+ out due to diffusion.
- as more K+ than Na+ can diffuse, the membrane comes to rest near the K+ EP.
what is the equation for the EP
Eion = 61 x log (ion)o / (ion)ii
define the sodium-potassium pump.
maintains the ionic cone gradients across the membrane and therefore RMP.
define ATP.
ATPA is broken down to release energy which forces ions to move against their conc gradients, pump uses energy to move sodium to restore balance between Na+ and K.
define key aspects to the action potential.
- nerve impulse
- allows communication within the neurone, along the axon
- generated at the axon hillock
- generated either by summation of converging inputs from the dendrites or by electrical stimulation.
what happens during conductance?
- following a small stimulation theres a small degree of depolarisation that decays along the length of a neurone, known as decremental conductance.
describe voltage-gated channels.
- open when the membrane becomes depolarised
- different degrees of depolarisation open the channels
- look at properties using voltage clamp experiments
- postive membrane potentials result in inactivation of Na+ channels.
how are voltage clamp experiments carried out?
- inject a current into the axon to create a steady membrane potential
- record the membrane current: product of what ions are moving across the membrane.
state the types of membrane currents.
transient inward current followed by a slow outward potential. sodium current (fast) - movement of ions into the neurone through Na+ channels. potassium current (slow) - movement of the ions out of the neurone through K+ channels.
outline the 8 steps to the AP.
- at RMP, majority of channels are closed
- small depolarisation opens a few Na+ channels, Na+ begins to move into the neurone, leading to depolarisation.
- if stimulation is large enough (threshold) the majority of Na+ channels open and Na+ moves into cell.
- as neurone continues to depolarise, some K+ channels are opened, allowing K+ to leave the neurone.
- at postive potenitals Na+ become deactivated. remaining K+ channels open, K+ continues to leave (inside now positive)
- membrane potential decreases and becomes negative (repolarisation).
- K+ channels begin to close and Na+ channels return t their closed normal state. The MP drops below the RMP (hyperpolarisation).
- final K+ channels close, MP returns to the RMP.
