Chapter 11: Functional Organization of the Nervous System

Comprehensive vocabulary flashcards covering the functional organization of the nervous system, including cell types, glial cell functions, action potential phases, and neuronal circuits.

Homeostasis

The function of the nervous system to regulate and coordinate activities to maintain balance.

Sensory (afferent) neuron

A functional class of neurons that relay action potentials to the central nervous system (CNS).

Association neuron (interneuron)

Neurons located in between the afferent and efferent neurons within the central nervous system.

Motor (efferent) neuron

A functional class of neurons that relay action potentials from the central nervous system to the effector.

Multipolar neuron

A neuron with more than 2 projections (1 axon and multiple dendrites) directly off of the cell body.

Pseudo-unipolar neuron

A neuron that has only 1 projection (an axon) directly off of the cell body.

Nissl bodies

Rough endoplasmic reticulum (ER) found within the neuron cell body or soma.

Nucleus

A collection of neuron cell bodies located within the central nervous system (CNS).

Ganglion

A collection of neuron cell bodies located within the peripheral nervous system (PNS).

Dendritic spines

Extensions on dendrites that receive information and conduct currents toward the cell body.

Trigger zone

The specific area of a neuron where an action potential is generated.

Tract

A collection of axons located within the central nervous system (CNS).

Peripheral nerve

A collection of axons located within the peripheral nervous system (PNS).

Astrocytes

Star-shaped glial cells that regulate extracellular brain fluid and produce chemicals to form the blood-brain barrier (BBB).

Ependymal cells

Glial cells that line brain ventricles and the spinal cord central canal, using cilia to circulate cerebrospinal fluid (CSF).

Choroid plexus

Structures found within certain regions of the brain ventricles and brainstem that produce cerebrospinal fluid (CSF).

Microglia

Specialized CNS macrophages that respond to inflammation and phagocytize necrotic tissue and microorganisms.

Satellite cells

Glial cells in the PNS that surround neuron cell bodies in ganglia to providing support, nutrients, and protection from heavy-metal poisons.

Oligodendrocytes

CNS glial cells that form insulating myelin sheaths around portions of several axons to increase conduction velocity.

Schwann cells

PNS glial cells that wrap around a portion of only one axon to form a myelin sheath.

Saltatory conduction

The process where an action potential is conducted from one node of Ranvier to the next in myelinated axons.

Gray matter

Nervous tissue consisting of unmyelinated axons, cell bodies, and dendrites.

White matter

Nervous tissue consisting of myelinated axons.

Depolarization

The phase where voltage-gated $Na^+$ ion channels open, causing an influx of $Na^+$ and making the neuron more positive.

Repolarization

The phase where voltage-gated $Na^+$ channels close and voltage-gated $K^+$ channels open, causing an efflux of $K^+$ ions.

Na+/K+ pump

A mechanism that resets resting membrane potential by moving $3 \text{ Na}^+$ ions out of the cell and $2 \text{ K}^+$ ions into the cell.

Absolute refractory period

A period of complete insensitivity to another stimulus during which a second action potential cannot be produced regardless of stimulus size.

Type A nerve fibers

Large-diameter, myelinated fibers that conduct at $15$ to $120 \text{ m/s}$.

Type C nerve fibers

Small-diameter, unmyelinated fibers that conduct at $2 \text{ m/s}$ or less.

Connexons

Protein tubes in cell membranes that allow graded current to flow between cells in electrical synapses.

Acetylcholinesterase

An enzyme that splits acetylcholine into Choline and Acetic acid to prevent repeated binding to receptors.

Monoamine oxidase (MAO)

An enzyme that breaks down norepinephrine molecules in the synaptic cleft/terminal.

Neuromodulators

Chemical messengers that influence the likelihood of an action potential being produced in the postsynaptic cell.

Presynaptic inhibition

A reduction in the amount of neurotransmitter released from the presynaptic terminal, such as endorphins inhibiting pain.

EPSP (Excitatory postsynaptic potential)

A stimulatory response where depolarization occurs, potentially reaching threshold for an action potential.

Spatial summation

When graded potentials produced at different dendrites summate at the trigger zone to reach threshold.

Temporal summation

When two action potentials arrive in close succession at the presynaptic membrane, allowing their graded potentials to summate.

Reverberating circuit

A neuronal circuit where outputs cause reciprocal activation, essential for rhythmic activities like breathing.