Nervous System: Neurophysiology

These flashcards cover key terms and concepts from the Anatomy & Physiology lecture focused on the nervous system and neurophysiology.

Ion Channels

Transmembrane proteins that allow specific ions to move into or out of the cell.

Leak Channels

Ion channels that are always open, allowing current to pass through.

Gated Channels

Ion channels that require a specific stimulus to open.

Chemically Gated Channels

Ion channels that open when a ligand binds to the receptor.

Voltage-Gated Channels

Ion channels that open in response to changes in membrane potential.

Mechanically Gated Channels

Ion channels that open in response to mechanical stimuli.

Resting Membrane Potential (RMP)

The potential difference in a resting neuron, typically -70mV.

Electrochemical Gradient

The combined effect of concentration gradient and electrical gradient on ion movement.

Equilibrium Potential for K+

The voltage at which the concentration and electrical gradients for K+ are balanced, typically -90mV.

Equilibrium Potential for Na+

The voltage at which the concentration and electrical gradients for Na+ are balanced, typically +61mV.

Graded Potentials

Local changes in membrane potential that vary in magnitude and decay rapidly.

Action Potentials (APs)

Rapid, all-or-nothing changes in membrane potential that propagate down the axon.

Absolute Refractory Period

The phase during which a neuron cannot fire another action potential.

Relative Refractory Period

The phase when a stronger stimulus is required to fire another action potential.

Depolarization

A decrease in membrane potential toward zero, making the inside of the cell more positive.

Hyperpolarization

An increase in membrane potential, making the inside of the cell more negative.

Threshold Potential

The critical level of depolarization needed to initiate an action potential, around -55mV.

Voltage-Gated Na+ Channel

Ion channel that opens to allow Na+ influx and is responsible for the rising phase of the action potential.

Voltage-Gated K+ Channel

Ion channel that opens to allow K+ efflux and is responsible for the repolarization phase of the action potential.

Contiguous Propagation

The slow propagation of action potentials in unmyelinated axons.

Saltatory Propagation

The rapid propagation of action potentials in myelinated axons, jumping from node to node.

Chemical Synapse

Type of synapse where neurotransmitters are released to transmit signals between neurons.

Postsynaptic Potential

Graded potential in the postsynaptic cell resulting from the opening of ion channels.

Excitatory Postsynaptic Potential (EPSP)

Depolarizing postsynaptic potential that makes a neuron more likely to fire.

Inhibitory Postsynaptic Potential (IPSP)

Hyperpolarizing postsynaptic potential that makes a neuron less likely to fire.

Neurotransmitter Removal

The process by which neurotransmitters are cleared from the synaptic cleft.

Temporal Summation

Summation of EPSPs occurring rapidly in time from the same presynaptic neuron.

Spatial Summation

Summation of EPSPs from multiple presynaptic neurons at the same time.

G-Protein Coupled Receptors (GPCRs)

Receptors that, when activated by neurotransmitters, stimulate intracellular changes via G-proteins.

Ion Channel-Linked Receptors

Receptors that open ion channels upon neurotransmitter binding, causing rapid changes in membrane potential.

Second Messenger Pathways

Intracellular signaling pathways initiated by GPCRs that lead to cell changes.

cAMP

One of the most common second messengers involved in intracellular signaling.

Concentration Gradient

The difference in concentration of ions across the membrane.

Action Potential Phases

The three phases of an action potential: depolarization, repolarization, and hyperpolarization.

Na+/K+ Pumps

Transport proteins that maintain the concentration gradients of Na+ and K+ across the membrane.

Membrane Potential

The voltage difference across the plasma membrane due to the distribution of ions.

Dendrites

The part of a neuron that receives signals and conducts them toward the cell body.

Axon Hillock

The region of the neuron where action potentials are initiated.

Synaptic Cleft

The space between the presynaptic and postsynaptic neurons.

Presynaptic Neuron

The neuron that releases neurotransmitters into the synaptic cleft.

Postsynaptic Neuron

The neuron that receives neurotransmitters at the synapse.

Neurotransmitter

Chemical messengers that transmit signals across a synapse.

Electrical Synapse

Type of synapse where direct ionic flow occurs between neurons via gap junctions.

Graded Potentials Decay

The phenomenon where graded potentials decrease in magnitude as they spread over distance.

Strong Stimulus

A stimulus that is capable of causing an action potential during the relative refractory period.

Motor Constant

A term used to describe the relationship between motor neurons and muscle fibers.

Membrane Polarization

The state of the cell membrane having an electric charge due to ion distribution.

Concentration Gradient of Na+ and K+

ICF: 140mM K+ 15mM Na+

ECF: 5mM K+ 140 mM Na+

Resting Membrane Potential

There are 25 K+ leak channels for every 1 Na+ leak channel

Graded Potentials

Changes in membrane potential that are local and vary in magnitude.

Ligand Gated ion channels

Ion channels that open or close in response to the binding of a specific ligand, allowing ions to flow across the membrane and changing the membrane potential.

3 different States of the channel;

1.) closed

2.) open (activated)

3.) Inactivated State

Label the AP

1.) Resting Sate

1.a) Threshold

2.) Depolarization; Na+ v-gates open, Na+ influx

3.) Na+ channels are deactivated

4.) Repolarization; K+ v-gates open, K+ efflux

5.) Na+ channels reset; enter a closed state

6.) Hyperpolarization; K+ channels remain open

7.) Resting potential returns to membrane potential

Bonus:

1.) Threshold Potential

2.) Refractory Period

2.a) Absolute Refractory

2.b) Relative Refractory

Absolute Refractory

The period during which a second action potential cannot be initiated, regardless of the strength of the stimulus, due to the inactivation of sodium channels.

Relative Refractory

The period following an absolute refractory period during which a second action potential can be initiated, but only by a stronger-than-normal stimulus, as some sodium channels have reset.

Chemical Synapse

1.) AP arrives to the Presynaptic terminal

2.) AP triggers Ca+ channels to open

3.) Ca+ causes synaptic vesicles to release neurotransmitters through exocytosis

4.) Neurotransmitters diffuse along the synaptic cleft and bind to receptors on the post-synaptic neuron

5.) Binding leads to ion channel opening, resulting in depolarization or hyperpolarization of the post-synaptic membrane.

6.) The process concludes with neurotransmitter removal from the synaptic cleft

Neurotransmitter for EPSP

Glutamate

Neurotransmitter for IPSP

GABA

Removal of Neurotransmitter from Synapse

1. Diffusion and Absorption: Neurotransmitters diffuse away from cleft and returned to presynaptic neuron

2. Degradation: degraded by enzymatic reactions in the cleft

3. Reuptake: transported back into the presynaptic neuron for reuse