Chapter 12 – The Nervous System

50 Question-and-Answer style flashcards covering the key concepts, structures, and processes of Chapter 12: The Nervous System.

What are the three general functions of the nervous system?

Collecting information, processing/evaluating information, and initiating responses to information.

Which division of the nervous system consists of the brain and spinal cord?

The Central Nervous System (CNS).

What structures compose the Peripheral Nervous System (PNS)?

Nerves (bundles of axons) and ganglia (clusters of neuron cell bodies).

Name the two functional divisions of the nervous system.

Sensory (afferent) division and motor (efferent) division.

What kind of stimuli does the somatic sensory system detect?

Stimuli we consciously perceive (e.g., touch, vision, hearing).

What kind of stimuli does the visceral sensory system detect?

Stimuli not typically perceived consciously (e.g., signals from heart or kidneys).

Which motor system sends voluntary signals to skeletal muscles?

The somatic motor system.

Which motor system sends involuntary commands to cardiac muscle, smooth muscle, and glands?

The autonomic (visceral) motor system.

What are the two subdivisions of the autonomic nervous system?

Sympathetic division and parasympathetic division.

List the five general characteristics of neurons.

Excitability, conductivity, secretion, extreme longevity, and amitotic nature.

Which part of a neuron contains the nucleus and perikaryon?

The cell body (soma).

What are dendrites and what is their primary function?

Short, unmyelinated neuron processes that receive input and transfer it to the cell body.

What is the axon hillock?

The triangular region of the soma where the axon originates; serves as the initial segment.

What structures are housed within synaptic knobs?

Synaptic vesicles containing neurotransmitter.

What is anterograde axonal transport?

Movement of materials from the cell body toward the synaptic knobs.

What is retrograde axonal transport?

Movement of materials from the axon toward the cell body for recycling or breakdown.

How fast is fast axonal transport compared with slow axonal transport?

Fast: ~400 mm/day; Slow: 0.1–3 mm/day.

Name the four structural classifications of neurons.

Multipolar, bipolar, unipolar (pseudounipolar), and anaxonic neurons.

Which structural type of neuron is most common in the body?

Multipolar neurons.

Which structural neuron type is typical of most sensory neurons in the PNS?

Unipolar (pseudounipolar) neurons.

Which functional class of neurons conducts input from receptors to the CNS?

Sensory (afferent) neurons.

Which functional class of neurons conducts output from the CNS to effectors?

Motor (efferent) neurons.

Which neurons make up about 99 % of all neurons and are confined to the CNS?

Interneurons (association neurons).

Define a nerve.

A bundle of parallel axons located in the Peripheral Nervous System.

What are the three connective tissue wrappings of a nerve?

Epineurium, perineurium, and endoneurium.

How are cranial nerves distinguished from spinal nerves?

Cranial nerves extend from the brain; spinal nerves extend from the spinal cord.

What type of nerve carries both sensory and motor fibers?

A mixed nerve.

What is a synapse?

A junction where a neuron communicates with another neuron or an effector cell.

How does a chemical synapse differ from an electrical synapse?

Chemical synapses use neurotransmitters and have a synaptic delay; electrical synapses use gap junctions and transmit signals rapidly without delay.

Which CNS glial cells help form the blood–brain barrier?

Astrocytes.

Which glial cell lines brain ventricles and helps produce cerebrospinal fluid?

Ependymal cells.

Which small, wandering CNS glial cells are phagocytic?

Microglia.

Which CNS glial cell myelinates axons?

Oligodendrocytes.

Name the two types of glial cells found in the PNS.

Satellite cells and neurolemmocytes (Schwann cells).

What is myelination?

The process of wrapping an axon with layers of glial cell membrane to form a myelin sheath.

Which cell myelinates axons in the PNS?

Neurolemmocytes (Schwann cells).

How many axons can one oligodendrocyte myelinate in the CNS?

Parts of multiple axons (each about 1 mm long on many different axons).

What are nodes of Ranvier?

Gaps between myelin-wrapped segments of an axon where voltage-gated channels are concentrated.

State two conditions that make PNS axon regeneration possible.

An intact neuron cell body and the presence of sufficient neurilemma.

Give one reason CNS axon regeneration is very limited.

Oligodendrocytes release growth-inhibiting molecules (others include axonal crowding and scar tissue).

What type of membrane proteins move ions against their gradients using ATP?

Pumps (e.g., Na⁺/K⁺ pumps).

What is Ohm’s law as applied to neurons?

Current = Voltage ÷ Resistance; current increases with higher voltage and lower resistance.

What is the typical resting membrane potential (RMP) of a neuron?

Approximately –70 mV.

Which ion’s diffusion is most influential in establishing the RMP?

Potassium (K⁺).

Approximately what membrane potential represents threshold at the axon hillock?

About –55 mV.

What ion movement produces the depolarization phase of an action potential?

Influx of Na⁺ through voltage-gated sodium channels.

What is the absolute refractory period?

A brief period (~1 ms) after an action potential during which no stimulus can initiate another action potential.

What type of conduction occurs along myelinated axons?

Saltatory conduction.

Which neurotransmitter is broken down by acetylcholinesterase in the synaptic cleft?

Acetylcholine (ACh).

What neuronal circuit uses feedback to generate repetitive, cyclical activity (e.g., breathing)?

A reverberating circuit.