chapter12

Vocabulary practice flashcards covering key structural components, classifications, action potentials, neuroglia, and clinical pathologies of the nervous system from Chapter 12.

Neurons

The basic functional units of the nervous system that send and receive stimuli or nerve impulses.

Neuroglia

Supporting cells in the nervous system that protect, support, and maintain neurons.

Central Nervous System (CNS)

The anatomical division of the nervous system consisting of the brain and spinal cord.

Peripheral Nervous System (PNS)

The anatomical division of the nervous system consisting of cranial nerves attached to the brain and spinal nerves attached to the spinal cord.

Afferent division

The functional division of the PNS that brings sensory impulses from receptors to the CNS.

Efferent division

The functional division of the PNS that carries motor commands from the CNS to peripheral effectors.

Somatic Nervous System (SNS)

A component of the efferent PNS division that controls voluntary skeletal muscle contractions.

Autonomic Nervous System (ANS)

A component of the efferent PNS division (also called the visceral motor system) that regulates cardiac muscle, smooth muscle, glands, and adipose tissue.

Sympathetic division

A division of the ANS that increases metabolic rate and mobilizes the body during fight-or-flight responses.

Parasympathetic division

A division of the ANS that decreases metabolic rate and promotes rest-and-relaxation activities.

Perikaryon

The cytoplasm surrounding the nucleus within the neuron cell body (soma).

Dendrites

Highly branched cellular processes that extend from the neuron cell body to receive incoming signals from other neurons.

Nissl bodies

Dense clusters of Rough Endoplasmic Reticulum (RER) and free ribosomes in neurons that give neural tissue its gray color.

Axon hillock

The thickened, cone-shaped region of the neuron cell body that connects the soma to the initial segment of the axon.

Telodendria

Fine terminal extension branches at the distal end of an axon that lead to synaptic knobs.

Synapse

The specialized site where a neuron communicates with another cell, comprising a presynaptic cell and a postsynaptic cell.

Axoplasmic Transport

The active movement of materials, such as neurotransmitters, along neurotubules between the cell body and synaptic knob.

Anaxonic neuron

A small neuron where axons cannot be distinguished from dendrites; located primarily in the brain and special sense organs.

Bipolar neuron

A neuron with two distinct processes—one dendrite and one axon—separated by a cell body located in the middle; involved in special sense organs.

Unipolar neuron

A neuron in which the dendrite and axon are continuous with the cell body lying off to one side; carries sensory information over long distances.

Multipolar neuron

A neuron featuring multiple dendrites attached to the cell body and a single long axon; the most common structural type in the CNS and motor pathways.

Exteroceptors

Sensory receptors that collect information about the external environment, including touch, temperature, sight, smell, and hearing.

Proprioceptors

Sensory receptors that monitor the position and movement of skeletal muscles and joints.

Interoceptors

Sensory receptors that monitor internal organ systems (digestive, respiratory, cardiovascular, urinary, reproductive) and provide sensations of deep pressure, pain, and taste.

Interneurons

Neurons located primarily within the brain and spinal cord that analyze sensory input and coordinate motor output; involved in higher functions like memory and learning.

Satellite cells

PNS neuroglia (also called amphicytes) that surround neuron cell bodies in ganglia to regulate local $\text{O}_2$, $\text{CO}_2$, nutrient, and neurotransmitter levels.

Schwann cells

PNS neuroglia (also called neurilemmal cells) that form myelin sheaths around peripheral axons and assist in axon repair after injury.

Oligodendrocytes

CNS neuroglia with slender processes that wrap around axons to form myelin, creating white matter.

Astrocytes

The largest and most abundant CNS neuroglia; responsible for maintaining the blood-brain barrier, structural support, neural repair, directing neuron development, and regulating interstitial fluid ions.

Microglia

The smallest and least numerous CNS neuroglia; phagocytic cells that engulf cellular debris, waste products, and pathogens.

Ependymal cells

Cuboidal to columnar epithelial neuroglial cells that line the central canal of the spinal cord and brain ventricles, assisting in circulating cerebrospinal fluid (CSF).

Nodes of Ranvier

Unmyelinated gaps along an axon located between adjacent internodes covered by myelin.

Wallerian Degeneration

The process of axon and myelin repair in peripheral nerves following injury, mediated by Schwann cells and macrophages.

Resting potential

The transmembrane potential of an undisturbed cell, typically $-70\text{ mV}$ in neurons.

Depolarization

A shift in transmembrane potential toward a less negative or positive charge, caused by the influx of sodium ions ($\text{Na}^+$) into the cytosol.

Hyperpolarization

An increase in the membrane potential negativity beyond resting level (e.g., to $-90\text{ mV}$), caused by potassium ions ($\text{K}^+$) leaving the cell.

Absolute refractory period

The period during an action potential when the cell membrane cannot respond to any further stimulation, regardless of strength.

Relative refractory period

The period following an action potential during which a second action potential can occur only if initiated by a larger-than-normal stimulus.

Saltatory propagation

The rapid transmission of an action potential along a myelinated axon, jumping from node to node.

Cholinergic synapse

Any synapse that synthesizes and releases the neurotransmitter Acetylcholine (ACh).

Acetylcholinesterase (AChE)

An enzyme located in the synaptic cleft that breaks down Acetylcholine (ACh) into acetate and choline to terminate synaptic signaling.

Presynaptic facilitation

A synaptic interaction (e.g., involving Serotonin) that opens calcium channels in the presynaptic terminal, increasing neurotransmitter release.

Presynaptic inhibition

A synaptic interaction (e.g., involving GABA) that inactivates calcium channels in the presynaptic terminal, reducing neurotransmitter release.

Temporal summation

The integration of multiple repeated stimuli applied in rapid succession at a single synapse to reach threshold potential.

Spatial summation

The integration of simultaneous stimuli applied at different physical locations across the postsynaptic membrane to reach threshold potential.

Botulinum toxin

A bacterial toxin from food poisoning that blocks Acetylcholine (ACh) release at neuromuscular junctions, causing paralysis.

Tetrodotoxin (TTX)

A potent neurotoxin found in puffer fish that selectively blocks voltage-gated sodium channels and paralyzes respiratory muscles.

Tay-Sachs disease

A genetic disorder marked by abnormal lysosomal enzyme activity in CNS neurons, leading to ganglioside accumulation, neuronal deterioration, blindness, and death before age 4.

Parkinson's disease

A progressive neurodegenerative disorder caused by deficient dopamine production in the brain, resulting in characteristic hand tremors.

Alzheimer's disease

A degenerative brain disease associated with deficient Acetylcholine (ACh) production and the accumulation of amyloid protein plaques (alpha and beta forms).