BIOSCI 107 ET: Neurons

Absolute refractory period

time during which another action potential is impossible.

Acetylcholine

neurotransmitter

Acetylcholine esterase

Enzyme that breaks down ACh in synaptic cleft.

Action potential

nerve impulse

Axon hillock

Where APs are generated

Axon terminal

Where chemical signals are released

Axon collateral

a branch of an axon

Two kinds of synapses

chemical and electrical

chemical synapse

synapse where a neurotransmitter is released from the axon terminal into the synaptic cleft

electrical synapse

Ions (and AP) spread from neuron to neuron through gap junctions

depolarisation

When the resting potential gets more positive

Ionic mechanism of depolarisation

The opening of sodium channels

hyperpolarisation

A decrease in the membrane potential due to exflux of K+

end-plate potential

initial depolarization of motor end plate

equilibrium potential

The membrane potential at which chemical and electrical forces are balanced for a single ion.

Nernst equation

Calculates equilibrium potential for specific ions.

EPSPs

Excitatory postsynaptic potentials

IPSPs

inhibitory postsynaptic potentials

excitatory synapses

synapse at which a neurotransmitter causes the receiving cell to fire

excitotoxicity

the property by which neurons die when overstimulated, as with large amounts of glutamate which overactivate NMDA leading to a large influx of Ca2+ ions

GABA

Inhibitory small molecule neurotransmitter

Glutamate

Primary excitatory neurotransmitter in the brain

Examples of small molecule neurotransmitters (3)

Amino acids, Acetylcholine, Amines

Examples of neuropeptides (4)

Enkephalin, Substance P, Kisspeptin, Neuropeptide Y

Goldman equation

Calculates the value of the RMP.

Inactivation gate of Na+ channel

Innactivates the gate within mileseconds of it opening

Inhibitory synapses

Synapses that make it less likely that a new AP will be generated on the postsynaptic neuron.

Ionotropic glutamine receptors

AMPA, Kainate, NMDA

typical ratio of K+ to Na+ leak channels

40/1

techniques to determine RPM

microelectrode, patch clamp technique

passive transmission

proceeds AP generation

Na/K ATPase

3 Na+ out, 2 K+ in. Maintains RMP

Neuromuscular junction

point of contact between a motor neuron and a skeletal muscle cell

Nodes of ranvier

gaps in the myelin sheath

AP conduction in myelinated axons

Saltatory

AP conduction in unmyelinated axons

Difference between myelinated and unmyelinated axons

speed, efficiency, diameter

What is receptor potential?

A type of graded potential which is the initial response to a stimulus.

Where does receptor potential occur?

In the dendrites or cell body.

What causes receptor potential?

A change in voltage across the receptor membrane proportional to the stimulus strength.

What types of ion channels are involved in receptor potential?

Ligand or mechanically gated ion channels.

temporal summation

The summation of many postsynaptic potentials from the same location very close together in time

spacial summation

The summation of many postsynaptic potentials that generate in different locations at the same time.

relative refractory period

AP could be generated by a strong stimulus

Stages of AP

depolarisation, repolarisation, hyperpolarisation

Typical [K+] intracellular and extracellular

100mM, 5mM

Typical [Na+] intracellular and extracellular

15mM, 150mM