Neural Tissue - Part 2 (Chapter 12) Vocabulary Flashcards

Vocabulary flashcards covering key neural tissue concepts from the lecture notes.

Excitable cells

Nerve and muscle cells that generate and transmit electrical signals in response to stimulation.

Resting membrane potential

The resting electrical potential across a neuron's membrane, typically negative inside (about -70 mV for neurons) and maintained by the Na+/K+ pump and membrane permeability.

Na+/K+ pump

Active transporter that moves 3 Na+ out and 2 K+ in, helping maintain the resting potential and ion gradients.

Leak channels

Ion channels that are open at rest; more K+ leak channels than Na+ leak channels, contributing to resting membrane potential.

Ligand-gated ion channel

Ion channel that opens in response to binding of a chemical ligand (neurotransmitter).

Voltage-gated ion channels

Ion channels that open or close in response to changes in membrane potential; essential for action potentials.

Mechanically-gated ion channels

Ion channels opened by mechanical deformation (stretch or pressure).

Membrane polarization

State where the outside of the membrane is positive and the inside is negative.

Depolarization

Membrane potential becomes less negative (more positive).

Repolarization

Return of the membrane potential to the resting value after depolarization.

Hyperpolarization

Membrane potential becomes more negative than the resting value.

Graded potentials

Local, variable-strength changes in membrane potential that decay with distance; can be excitatory or inhibitory.

EPSP (excitatory postsynaptic potential)

Depolarizing postsynaptic potential that brings the membrane potential closer to threshold.

IPSP (inhibitory postsynaptic potential)

Hyperpolarizing postsynaptic potential that moves the membrane potential further from threshold.

Temporal summation

Addition of postsynaptic potentials that occur in rapid succession at a single synapse.

Spatial summation

Addition of postsynaptic potentials arriving at different locations on the neuron at the same time.

Axon hillock

Region where the axon begins; integrates inputs and often initiates action potentials at threshold.

Action potential

All-or-none electrical impulse that travels along the axon; initiated when threshold is reached at the axon hillock.

Saltatory conduction

Fast propagation of action potentials along myelinated axons by jumping between nodes of Ranvier.

Node of Ranvier

Gaps in the myelin sheath rich in voltage-gated channels where action potentials are regenerated.

Continuous propagation

Propagation of action potentials along unmyelinated axons via sequential depolarization of adjacent segments.

Refractory period

Time after an action potential during which another cannot (absolute) or is harder (relative) to elicit an action potential.

Absolute refractory period

Phase during which no new action potential can be generated.

Relative refractory period

Phase during which a higher-than-normal depolarization is needed to trigger another action potential.

Electrical synapse

Synapse where presynaptic and postsynaptic cells are connected by gap junctions for fast transmission.

Gap junction

Protein channels forming direct cytoplasmic connections between cells.

Chemical synapse

Synapse where neurotransmitters cross the synaptic cleft to affect the postsynaptic cell.

Synaptic vesicle

Membrane-bound vesicles in the presynaptic terminal containing neurotransmitters.

Synaptic cleft

The gap between presynaptic and postsynaptic membranes across which neurotransmitters diffuse.

Ca2+ channels

Voltage-gated calcium channels in the presynaptic terminal; calcium entry triggers vesicle exocytosis.

Neurotransmitter

Chemical released by a neuron that affects the membrane potential of another neuron; effects can be excitatory or inhibitory depending on the receptor.

Neuromodulator

Chemical released by a neuron that modulates the sensitivity of another neuron to neurotransmitters; effects are generally widespread.

Acetylcholine (ACh)

Neurotransmitter; typically excitatory at skeletal muscle and inhibitory in cardiac muscle.

Acetylcholinesterase (AChE)

Enzyme that degrades acetylcholine in the synaptic cleft to terminate the signal.

Epinephrine (adrenaline)

Neurotransmitter; involved in brain and sympathetic nervous system; usually excitatory.

Norepinephrine (noradrenaline)

Neurotransmitter; involved in brain and sympathetic nervous system; usually excitatory.

Dopamine

Neurotransmitter with excitatory or inhibitory effects depending on receptor type; D1 relates to reward/motivation/movement; D2 relates to sleep/mood regulation; cocaine can exaggerate dopamine signaling by affecting its release.

Serotonin (5-HT)

Neurotransmitter involved in attention and emotion; widespread; about 95% is in the digestive system; SSRIs increase serotonin in the synapse; low levels linked to depression; also stimulates gastric motility.

GABA (gamma-aminobutyric acid)

Most common inhibitory neurotransmitter in the brain; increases Cl- influx, hyperpolarizing the postsynaptic neuron; alcohol enhances GABA receptor effects.

Nitric oxide (NO)

Dissolved gaseous neurotransmitter produced by axon terminals; causes vasodilation and smooth muscle relaxation; involved in penile erection.

Endorphins

Endogenous opioids; neuromodulators that reduce pain by inhibiting Substance P release and modulating Ca2+ and K+ channels.

Substance P

Neurotransmitter involved in the transmission of pain signals.

Receptor determines effect

The effect of a neurotransmitter depends on the postsynaptic receptor type rather than the neurotransmitter alone.

Reuptake

Reabsorption of neurotransmitter into the presynaptic neuron to terminate the signal.

Diffusion

Passage of neurotransmitter away from the synaptic cleft as a means of signal termination.

Post-synaptic potential

Local changes in membrane potential in the postsynaptic neuron due to neurotransmitter binding (EPSPs and IPSPs are examples).

Myelin sheath

Insulating layer around many axons that increases the speed of electrical conduction.