Neuron Structure and Function

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Questions and Answers

What is the primary function of the myelin sheath in the nervous system?

To transmit chemical signals between neurons
To receive impulses from other neurons
To speed up nerve impulse conduction (correct)
To provide structural support to neurons

Which statement accurately describes gray matter?

It contains only efferent neurons responsible for motor function.
It primarily consists of myelinated axons and is responsible for long-distance signal transmission.
It is composed mainly of neuron cell bodies and unmyelinated fibers, involved in information processing. (correct)
It provides insulation to nerve fibers and supports them structurally.

What role do interneurons play in the nervous system?

They conduct impulses away from the central nervous system to muscles.
They transmit impulses from sensory organs to the central nervous system.
They connect sensory and motor neurons within the central nervous system. (correct)
They provide nutrients to myelinated axons in the peripheral nervous system.

The reflex arc is characterized by which of the following components?

Sensory receptor, sensory neuron, interneuron, motor neuron, and effector (C) Signup and view all the answers

Depolarization in a neuron primarily leads to what physiological event?

The influx of positive ions leading to an action potential (D) Signup and view all the answers

What is the primary role of the sympathetic nervous system?

Prepares the body for fight-or-flight responses. (C) Signup and view all the answers

Which function is primarily associated with cerebrospinal fluid (CSF)?

Cushions the brain and spinal cord. (B) Signup and view all the answers

What is the main function of astrocytes in the nervous system?

Provide structural and metabolic support to neurons. (C) Signup and view all the answers

In what way does myelin affect nerve impulse conduction?

It facilitates the jumping of action potentials between nodes. (B) Signup and view all the answers

Which part of the brain is responsible for coordinating muscle movements and balance?

Cerebellum (B) Signup and view all the answers

What are cranial nerves primarily responsible for?

Transmitting sensory and motor information between the brain and head/neck. (A) Signup and view all the answers

What best describes a dermatome?

An area of skin supplied by a single spinal nerve root. (D) Signup and view all the answers

Multiple sclerosis primarily affects which structure in the nervous system?

Myelin sheaths of axons. (A) Signup and view all the answers

What is the primary role of astrocytes in the central nervous system?

Provide structural support and anchor neurons to blood vessels (D) Signup and view all the answers

During the process of depolarization, which ion primarily enters the neuron?

Sodium (Na+) (B) Signup and view all the answers

Which of the following accurately describes the function of the cerebellum?

Coordinates muscle movements and maintains balance (D) Signup and view all the answers

What differentiates white matter from gray matter in the CNS?

White matter consists of myelinated axons while gray matter consists of unmyelinated fibers and cell bodies (C) Signup and view all the answers

What is the sequence of events in a simple reflex arc, such as the patellar reflex?

Stimulus, sensory neuron, motor neuron, effector (C) Signup and view all the answers

Which component is NOT part of a synapse?

Membrane of the effector organ (A) Signup and view all the answers

In the context of the autonomic nervous system, which statement is true regarding the sympathetic and parasympathetic divisions?

The sympathetic division typically enhances body functions, while the parasympathetic inhibits them. (B) Signup and view all the answers

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Study Notes

Neuron Structure

A neuron is a specialized nerve cell with three main parts:
- Cell body: Contains the nucleus and other organelles
- Dendrites: Branching extensions that receive signals from other neurons
- Axon: A single, long extension that transmits signals away from the cell body

Neuron Types

Sensory neurons (afferent neurons): Carry signals from sensory receptors to the CNS
Motor neurons (efferent neurons): Carry signals from the CNS to muscles and glands
Interneurons: Connect sensory and motor neurons within the CNS, allowing for complex processing of information

Glial Cells

Astrocytes: Provide structural support, maintain the blood-brain barrier, and regulate nutrient and ion concentrations
Microglia: Act as immune cells, engulfing debris and pathogens
Oligodendrocytes: Form myelin sheaths around axons in the CNS, improving signal transmission speed

White Matter vs. Gray Matter

White matter: Composed of myelinated axons, responsible for fast signal transmission over long distances
Gray matter: Consists mainly of neuron cell bodies, dendrites, synapses, and unmyelinated axons, involved in processing information

Simple Reflex Arc

A stimulus triggers sensory receptors, sending an impulse along a sensory neuron to the spinal cord.
The impulse synapses with an interneuron within the spinal cord.
Interneuron relays the signal to a motor neuron, triggering a response in an effector (muscle or gland).

Nerve Impulse Mechanism (Action Potential)

Resting state: Neuron membrane is polarized, with more positive charges outside and more negative charges inside.
Depolarization: A stimulus causes sodium ion channels to open, allowing sodium ions to rush into the neuron, making the inside more positive.
Repolarization: Potassium ion channels open, allowing potassium ions to flow out, restoring the negative charge inside the neuron.

Synapse

A junction between two neurons where nerve impulses are transmitted.
Components:
- Presynaptic neuron: Contains synaptic vesicles filled with neurotransmitters
- Synaptic cleft: The space between the neurons
- Postsynaptic neuron: Contains receptors that bind to neurotransmitters

Cerebellum Function

Coordinates muscle movements, contributing to smooth and precise motor control
Maintains balance and posture
Plays a role in learning and memory of motor skills

Autonomic Nervous System Divisions

Sympathetic nervous system: Prepares the body for "fight-or-flight" responses, increasing heart rate, blood pressure, and respiration
Parasympathetic nervous system: Promotes "rest-and-digest" functions, slowing heart rate, lowering blood pressure, and stimulating digestion