Neuron Day 2

Voltage Gated Channels

Located in axon membrane

Ligand Gated Channels

Located in synapses

Mechanically Gated

Located in sensory receptors

Goldman Equation

Describes Vm

Vm

Membrane voltage; determines when voltage sensitive ion channels open and close

Numbers in Voltage Gated Na+ Channel

Alpha helical transmembrane segments

Roman numerals in voltage gated Na+ channel

Homologous domains

polypeptide chain of amino acid

Change in voltage causes conformational change in

A type currents

Inactivate fast

Mechanically gated channel example

Hair cell in inner ear

nAChR

ligand gated channel

triggers response in muscle cell

acetylcholine

nAChR opens upon binding of

Absolute refractory period

Complete insenstitivity to another stimulus

Once closed, channels can reopen to a second stimulus

Relative refractory period

Stronger than threshold stimulus can initiate another AP

A alpha nerve fibers

Carry info related to proprioception

Proprioception

Muscle sense

A beta nerve fibers

Carry info related to touch

A delta nerve fibers

Carry info related to pain/temperature

C nerve fibers

Carry info related to pain, temperature, and itch

Cable Theory

Flow of currents within axon described by

Cable Theory definition

Neuron is treated as electrically passive, perfectly cylindrical transmission cable

Capacitance

Stored electric charge

Electrostatic forces through phospholipid bilyer

Capacitance of neuronal fiber due to

Cytosol’s resistance to movement of electric charge

Resistance of neuronal fiber due to

Length constant

Characteristic lengths on which voltage across membrane decays

Applied voltage decreases to 37% of original size

Acetylcholine

Neurotransmitter between nerves and muscle

In brain —> memory, attention, learning

In heart —> parasympathetic

GABA

Inhibitor of neurotransmission

Opens Cl channels on postsynaptic membrane

Glycine

Inhibitor of neurotransmission

Can increase Cl- influx

Glutamate

Involved with learnign and memory

Generally excitatory

Norepinephrine/Epinephrine

Dual roles as hormones/neurotransmitters

Involved in attention/mental focus

Dopamine

Behavior/cognition, voluntary movement, motivation/reward, lactation, sleep, mood, attention, learning

Parkinson’s

Degeneration of dopamine releasing neurons in substantia nigra

Progressive loss of muscle control

Serotonin

Derived from tryptophan

Regulates intestinal movements

Involved in mood, appetite, sleep

Neuropeptides

Indirect neurotransmitters

Endorphins

Released during pleasurable experiences

Reduce perception of pain

PNS

Enkephalins

Subset of endorphins

Modulate pain response

CNS

Substance P

Released by spinal cord

Increase perception of pain

CO

Regulates release of hormones from hypothalamus

NO

Learning, muscle movement

Relaxes smooth muscle in blood vessel walls; causes dilation

EPSP

Change in membrane potential that moves neuron closer to threshold

IPSP

Change in membrane potential that moves neuron father from threshold

Temporal Summation

Temporal of more than one EPSP produced by successive firing of a single presynaptic neuron over a short period of time

Spatial Summation

Summation of EPSPs produced by firing of different presynaptic neurons