BIOL 2160 Exam 3 Study Questions (Advanced Review)

Practice vocabulary flashcards covering neurobiology, synaptic transmission, glial functions, metabolism, and endocrine regulation based on BIOL 2160 Exam 3 review questions.

Temporal Summation

The additive effect that occurs when postsynaptic potentials arrive close together in time from repeated EPSPs at the same synapse in rapid succession, overlapping before returning to baseline.

Chloride ($Cl^-$) Permeability

An increase in membrane conductance to chloride that allows $Cl^-$ entry, causing the membrane to hyperpolarize or resist depolarization and producing inhibitory effects.

All-or-None Property

The principle stating that once threshold is reached, action potentials are all the same size; stronger stimulus intensity is encoded by firing frequency rather than amplitude.

Presynaptic $Ca^{2+}$ Channels

Voltage-gated channels whose blocking prevents calcium influx, dramatically reducing synaptic vesicle fusion and neurotransmitter release via exocytosis.

Neuronal Cell Membrane Resistance

The high electrical resistance to ion flow provided by the lipid bilayer, which is a poor conductor of ions compared to aqueous intracellular and extracellular compartments.

Saltatory Conduction

The rapid propagation of action potentials from node to node along a myelinated axon, the disruption of which causes slower and less reliable conduction in multiple sclerosis.

Absolute Refractory Period

The period during which a second action potential cannot be generated because voltage-gated $Na^+$ channels are either already open or inactivated and unable to reopen until repolarization.

NMDA Receptor

A receptor directly associated with the initiation of long-term potentiation (LTP) by allowing $Ca^{2+}$ entry when activated under appropriate conditions.

Nicotinic Acetylcholine Receptor

A ligand-gated channel whose activation permits cation movement favoring depolarization, typically producing an excitatory postsynaptic potential (EPSP).

Depolarization Toward Threshold

A membrane potential change from $-70\,mV$ to $-55\,mV$, wherein the membrane becomes less negative and approaches threshold.

Oligodendrocyte

A type of glial cell that produces myelin in the central nervous system (CNS) and is responsible for CNS myelin repair if regeneration occurs.

Schwann Cell

A type of glial cell that performs myelin production in the peripheral nervous system (PNS).

Nodes of Ranvier

Axonal gaps that concentrate high densities of voltage-gated $Na^+$ channels to regenerate the signal and accelerate impulse conduction.

Excitatory Postsynaptic Potential (EPSP)

A graded depolarization that brings the postsynaptic membrane potential closer to threshold, increasing the probability of action potential generation.

Action Potential Repolarization

The falling phase of an action potential driven by the inactivation of voltage-gated $Na^+$ channels and the opening of voltage-gated $K^+$ channels, which reverses membrane polarity.

Electrical Synapse

A junction formed by gap junctions that connects cells electrically, permitting bidirectional ionic current flow directly between cells with minimal synaptic delay.

Glucagon

A hormone secreted by pancreatic alpha cells that stimulates glycogenolysis and other glucose-raising pathways to prevent hypoglycemia during fasting.

GLUT-4

A glucose transporter whose increased insertion into cell membranes facilitates greater cellular glucose uptake, thereby lowering blood glucose concentrations.

Postabsorptive State

The metabolic state after nutrient absorption ends, during which fat burning increases as tissues rely on fat stores to conserve glucose.

Pancreatic Alpha Cells

Endocrine cells in the pancreas responsible for secreting glucagon to raise blood glucose.

Muscarinic Acetylcholine Receptor

A G-protein-coupled receptor that produces postsynaptic potentials primarily through intracellular signaling cascades.

Myelin

An insulating axonal sheath lacking ion channels that prevents current leakage across the membrane, resulting in higher membrane resistance and faster conduction.

Microglia

Resident immune cells of the nervous tissue functionally similar to immune cells, participating in defense and debris removal.

Extracellular $K^+$ Elevation

An increase in external potassium that diminishes the concentration gradient, resulting in less $K^+$ leaving the cell and causing initial depolarization.

Membrane Conductance

A measure of how readily ions traverse the cell membrane, which increases as ion channels open.

Atropine

A muscarinic receptor antagonist that directly interferes with cholinergic signaling at muscarinic receptors.

Wernicke’s Area

A region of the central nervous system critical for language comprehension.

Curare

A substance that produces paralysis by blocking nicotinic receptors at the skeletal neuromuscular junction.

Relative Refractory Period

A period following an action potential during which voltage-gated $K^+$ permeability remains elevated, keeping the membrane hyperpolarized and requiring a stronger stimulus to trigger another action potential.

Long-Term Potentiation (LTP)

A form of synaptic plasticity resulting from repeated stimulation that increases the number of AMPA receptors and enhances synaptic strength.

Special Sense

A classification of sensory modalities comprising specialized senses such as vision.

Potassium Equilibrium Potential ($E_K$)

The electrical potential toward which the resting membrane potential shifts when additional leak $K^+$ channels open, driving the cell more negative.

Chemical Synapse Unidirectionality

The one-way transmission across chemical synapses resulting from neurotransmitter release machinery being presynaptic and receptors being postsynaptic.

Hyperosmolar State

A severe complication in untreated diabetes resulting from excessive fluid excretion caused by increased glucose osmotic activity in the kidneys.

Type 2 Diabetes Risk Factors

Metabolic factors strongly associated with disease likelihood, most notably high BMI and insulin resistance.

Inactivation of $Na^+$ Channels

The state entered by voltage-gated sodium channels at the peak of an action potential that persists during the falling phase and prevents channel reopening until repolarization occurs.

Cytosolic $Ca^{2+}$ Clearance

The active removal of calcium following synaptic transmission via uptake into the endoplasmic reticulum and active transport across the cell membrane.

Interneurons

Neurons that integrate and process information within the CNS, connecting sensory and motor pathways.

Insulin

A hormone that lowers blood glucose levels by promoting glucose uptake into tissues and stimulating glucose storage.