Lecture Chapter 12

Comprehensive vocabulary flashcards covering anatomical divisions, glial cell classifications, action potential dynamics, synapse physiology, neural circuits, and nervous system pathologies from Chapter 12.

Central Nervous System (CNS)

The branch of the nervous system consisting of the brain and spinal cord, which processes information and sends out commands.

Peripheral Nervous System (PNS)

The branch of the nervous system consisting of cranial and spinal nerves, enteric plexuses in the small intestine, and sensory receptors in the skin that relays signals between the CNS and the rest of the body.

Sensory Function

The nervous system function that detects internal and external changes through sensory receptors.

Integrative Function

The nervous system function that analyzes incoming sensory information, processes it, stores some aspects, and makes decisions regarding appropriate behaviors.

Motor Function

The nervous system function that responds to stimuli via effectors.

Ionotropic Receptors

Neurotransmitter receptors that contain both a neurotransmitter binding site and an ion channel (ligand-gated); capable of generating EPSPs due to $Ca^{2+}$ or $Na^+$ influx, or IPSPs due to $Cl^-$ influx.

Metabotropic Receptors

Neurotransmitter receptors that contain a neurotransmitter binding site coupled to a separate ion channel via a G protein (GPCR); generates IPSPs linked to $K^+$ channels.

Leak Channels

Gated channels that randomly open and close; found in nearly all cells and distributed throughout dendrites, cell bodies, and axons of all neuron types.

Ligand-Gated Channels

Gated channels that open in response to a chemical (ligand) stimulus; located in the dendrites of some sensory neurons (such as pain receptors) and in the dendrites and cell bodies of interneurons and motor neurons.

Mechanically Gated Channels

Gated channels that open in response to mechanical stimuli (such as touch, pressure, vibration, or tissue stretching); found in dendrites of sensory touch receptors, pressure receptors, and some pain receptors.

Voltage-Gated Channels

Gated channels that open in response to a voltage stimulus (change in membrane potential); located along the axons of all types of neurons.

Sodium-Potassium Pump

An active transport mechanism that establishes and restores resting membrane potential (keeping the inside negative relative to the outside); creates the electrochemical gradient required for voltage-gated channels to fire electrical impulses.

Action Potential (AP)

A sequence of rapidly occurring events that decreases, reverses, and restores membrane potential to its resting state, enabling short- and long-distance communication between excitable cells.

Depolarization

The phase of an action potential during which the inside of the cell becomes increasingly electropositive toward the sodium electrochemical equilibrium of $+61\,\text{mV}$, featuring activated sodium channels and deactivated potassium channels.

Repolarization

The phase of an action potential that restores resting membrane potential, characterized by inactivated sodium channels and activated potassium channels.

Hyperpolarization

A state in which the membrane potential becomes more negative than resting potential, with potassium channels remaining activated while sodium channels move back toward an activatable resting state.

Dendrites

Neuron processes that receive stimuli via ligand-gated or mechanically gated channels; produce generator/receptor potentials in sensory neurons and EPSPs/IPSPs in interneurons and motor neurons.

Cell Body

The soma of a neuron that receives stimuli and produces EPSPs and IPSPs through the activation of ligand-gated ion channels.

The junction of the axon hillock

trigger zone and initial segment of the axon that integrates EPSPs and IPSPs to initiate a nerve impulse if threshold depolarization is reached.

Axon

A neuronal extension that propagates nerve impulses in a self-regenerating manner from the initial segment to axon terminals without a decrease in impulse amplitude.

Axon Terminals and Synaptic End Bulbs

Distal structures of an axon where depolarization-induced $Ca^{2+}$ inflow triggers exocytosis of neurotransmitters from synaptic vesicles.

Neuroglia

Supporting cells of the nervous system that are not electrically excitable, make up about half of its total volume, can multiply and divide, and comprise six total types (four in the CNS and two in the PNS).

Astrocytes

Star-shaped CNS neuroglia with numerous processes that contact blood capillaries, neurons, and pia mater; they support the blood-brain barrier (BBB), regulate chemical environments, guide embryonic neuron growth, and influence synapse formation.

Oligodendrocytes

CNS neuroglia with fewer processes than astrocytes that produce and wrap myelin sheaths around several axons simultaneously, resembles astrocytes but smaller and fewer processes

Microglial Cells

Small CNS glial cells with slender processes that act as phagocytes to remove cellular debris, microbes, and damaged nervous tissue.

Ependymal Cells

A single layer of ciliated cuboidal or columnar CNS cells lining brain ventricles and the spinal central canal; they produce, monitor, and assist in circulating cerebrospinal fluid (CSF) and contribute to the blood-cerebrospinal barrier (BCB).

Schwann Cells

PNS neuroglia that encircle individual PNS axons to form myelin sheaths (in a 1 axon per cell ratio) and assist in axon regeneration.

Satellite Cells

Flat PNS glial cells surrounding cell bodies in ganglia; provide structural support and regulate material exchange between neuronal cell bodies and interstitial fluid.

Excitatory Postsynaptic Potential (EPSP)

A depolarizing postsynaptic potential that brings the membrane potential closer to threshold.

Inhibitory Postsynaptic Potential (IPSP)

A hyperpolarizing postsynaptic potential that moves the membrane potential further from threshold.

Neurotransmitter

A chemical messenger molecule released by neurons to transmit signals across synapses to other neurons, muscle cells, or gland cells.

Electrical Synapse

A junction where gap junctions directly connect adjacent cells, allowing the transfer of ions and molecules to synchronize electrical activity across a group of cells.

Chemical Synapse

A junction providing one-way transmission of information from a presynaptic neuron to a postsynaptic neuron or effector cell using neurotransmitters.

Simple Circuit

A neural circuit organization in which one presynaptic neuron synapses directly with a single postsynaptic neuron ($1\text{ pre} \rightarrow 1\text{ post}$).

Diverging Circuit

A neural circuit organization in which one presynaptic neuron synapses with multiple postsynaptic neurons ($1\text{ pre} \rightarrow \text{multiple post}$).

Converging Circuit

A neural circuit organization in which several presynaptic neurons synapse with a single postsynaptic neuron ($\text{several pre} \rightarrow 1\text{ post}$).

Reverberating Circuit

A neural circuit organization in which branches from downstream neurons loop back to synapse with earlier neurons in the sequence.

Parallel After-Discharge Circuit

A neural circuit organization in which one presynaptic neuron stimulates a group of parallel postsynaptic neurons that synapse onto a single common output.

Multiple Sclerosis (MS) & Guillain-Bare Syndrome

Progressive destruction of myelin sheath (MS-CNS; GBS-PNS)

Epilepsy

A disorder characterized by short, recurrent attacks of motor, sensory, or psychological malfunction initiated by abnormal, synchronous electrical discharges from the brain.

Excitotoxicity

Destruction of neurons resulting from prolonged activation due to excessive glutamate accumulation and oxygen deprivation within CNS interstitial fluid.

Depression

A disorder linked to an imbalance of neurotransmitters (serotonin, norepinephrine, and dopamine), influenced by factors such as heredity, stress, hormones, chronic illness, and low self-esteem.

Rabies

A viral infection that causes inflammation of the brain and meninges, resulting in death within $2\text{--}10$ days after the appearance of symptoms.

Neuroblastoma

A form of cancer originating in nerve cells near the adrenal glands that primarily affects children under $5$ years of age ($< 5\,\text{years old}$).

Sensory (Afferent) Neurons

Neurons classified by function that convey nerve impulses and sensory information inward toward the Central Nervous System.

Motor (Efferent) Neurons

Neurons classified by function that convey action potentials away from the Central Nervous System to effectors.

Interneurons (Association Neurons)

Neurons located within the CNS that process incoming sensory information and elicit an appropriate motor response.

White Matter

Nervous tissue located deep within brain structures primarily consisting of myelinated axons.

Gray Matter

Superficial nervous tissue composed of neuronal cell bodies, axon terminals, unmyelinated axons, and neuroglia.

Structural Classification of Neurons

The categorization of nerve cells based on the number of processes extending from the soma, consisting of multipolar, bipolar, and pseudounipolar types.

Multipolar Neurons

A structural classification of nerve cells characterized by having several dendrites and a single axon extending from the soma.

Bipolar Neurons

A structural classification of nerve cells characterized by having two distinct extensions: one main dendrite and one axon extending from the soma.

Pseudounipolar Neurons

A structural classification of nerve cells characterized by a single fused process extending from the soma that branches into two functional pathways.

Diffusion (Neurotransmitter Inactivation)

A mechanism of neurotransmitter removal where chemical messenger molecules passively move away from the synaptic cleft into the extracellular fluid.

Enzymatic Degradation

A mechanism of neurotransmitter termination where specific catalytic proteins break down chemical messengers in the synaptic cleft, such as AChE, COMT, and monoamine oxidase.

Uptake into Cells

A mechanism of neurotransmitter termination in which released messenger molecules are actively transported back into the presynaptic neuron or neighboring neuroglia.

What are the different branches of the nervous system?

Central Nervous System (CNS), Peripheral Nervous System (PNS)

Synapse

is the junction between neurons or between a neuron and an effector