Nervous System Overview

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Questions and Answers

Which part of the neuron acts as the main receptive input region?

Dendrites (correct)

Axon hillock

Myelin sheath

Axon

What is the primary function of the myelin sheath?

To connect neurons to muscle fibers

To generate nerve impulses

To maintain the structural integrity of the neuron

To protect and insulate axons (correct)

In which direction does anterograde movement occur in an axon?

Away from the axon terminal

In both directions equally

Toward the cell body

Toward the axon terminal (correct)

What unique property do neurons possess concerning their ability to replicate?

They are amitotic Signup and view all the answers

Which structure is responsible for transmitting nerve impulses away from the neuron cell body?

Axon Signup and view all the answers

What role do the Nodes of Ranvier play in neuron function?

Create gaps in the myelin sheath for saltatory conduction Signup and view all the answers

What is the primary characteristic of neuroglia cells?

They occupy space between neurons Signup and view all the answers

What is the axon hillock?

The cone-shaped area where the axon originates Signup and view all the answers

What initiates an action potential in a neuron?

Influx of Na+ ions Signup and view all the answers

What is the primary characteristic of unipolar neurons?

Have a single short process Signup and view all the answers

What happens during the process of depolarization?

Both B and C Signup and view all the answers

Which type of synapse is characterized by the direct electrical coupling of two neurons?

Electrical synapse Signup and view all the answers

Which functional type of neuron transmits impulses from sensory receptors towards the CNS?

Sensory (afferent) neurons Signup and view all the answers

What distinguishes gray matter from white matter in the nervous system?

White matter contains mainly myelinated axons Signup and view all the answers

How is the resting potential of a neuron primarily maintained?

Differences in ion concentrations across the membrane Signup and view all the answers

Which type of synapse involves the release of neurotransmitters?

Chemical synapse Signup and view all the answers

What type of neurons are almost all interneurons in the CNS classified as?

Multipolar neurons Signup and view all the answers

Which ion's equilibrium potential primarily determines the resting potential of a neuron?

K+ ions Signup and view all the answers

What is the primary function of the cerebral cortex?

Receiving sensory information and initiating motor activity Signup and view all the answers

Which type of cell in the cerebral cortex is characterized by a triangular shape and large nucleus?

Pyramidal cell Signup and view all the answers

Which layer of the cerebellar cortex contains the highly branched granule cells?

Granule cell layer Signup and view all the answers

The dorsal root of the spinal cord is primarily associated with which type of fiber?

Sensory fibers Signup and view all the answers

Astrocytes are primarily responsible for which of the following functions?

Blood-brain barrier maintenance Signup and view all the answers

What is the role of Purkinje cells in the cerebellar cortex?

Transmitting inhibitory signals Signup and view all the answers

In the context of neuroglial cells, what function do Schwann cells serve?

Production of myelin in the PNS Signup and view all the answers

Which division of the autonomic nervous system is associated with the thoracolumbar region?

Sympathetic division Signup and view all the answers

Study Notes

Nervous System

Contains two major divisions: the central and peripheral nervous systems
The central nervous system (CNS) consists of the brain and spinal cord
The peripheral nervous system (PNS) is composed of nerves emerging from the CNS and ganglia
Neuroglia are supporting cells that occupy space between neurons

Neurons

The structural units of the nervous system
Highly specialized cells that conduct messages as nerve impulses
Have three key characteristics: extreme longevity, amitotic nature, and exceptionally high metabolic rates
Consists of a cell body with one or more cell processes enclosed by neurolemma
Nissl bodies are rough endoplasmic reticulum in the perikaryon

Nerve Cell Processes

Dendrites are the main receptive input regions, providing a surface area for receiving signals from other neurons
Dendrites convey incoming messages toward the cell body
The axon is the conducting region of the neuron, generating nerve impulses and transmitting them away from the cell body

Axon Structure

The axon hillock is the cone-shaped area of the cell body where the axon arises
Axon terminals (synaptic knobs, boutons) are the knob-like distal endings of the terminal branches of axons

Axonal Transport

Anterograde movement refers to movement toward the axon terminal
Retrograde movement refers to movement away from the axon terminal

Myelin Sheath

A whitish, fatty, segmented covering that protects and electrically insulates fibers
Increases the speed of nerve impulse transmission
Primarily associated with axons (dendrites are usually unmyelinated)

Saltatory Conduction

The myelin sheath facilitates conduction along the axon
Nodes of Ranvier are short gaps created by the myelin sheath along the axon
Saltatory conduction, facilitated by the nodes of Ranvier, is faster than conduction in unmyelinated axons

Nerve Impulse Generation

The ability of neurons to receive, conduct, and transmit signals relies on the opening and closing of specific ion channel proteins in their membranes
During the resting potential, the concentration of Na+ ions is only 1/10th that of extracellular fluids, while the internal K+ ion concentration is about 10x greater than outside the cell, resulting in a potential difference of about -90mV (inside negative relative to the outside)

Depolarization and Action Potential

Depolarization involves a sudden influx of extracellular Na+ ions that lowers the membrane potential (making the inside less negative)
This is followed by an outflow of K+ ions that restores the resting potential
These changes create an Action Potential

Synapse

The specialized region of contact where neurotransmitters are released from an axon to stimulate another cell
Junction that mediates information transfer from one neuron to the next, or from a neuron to an effector cell

Synapse Types

Can be excitatory or inhibitory, depending on whether the transmitter depolarizes or hyperpolarizes the presynaptic membrane
Types of synapses include axodendritic, axosomatic, axoaxonic, dendrodendritic, and dendrosomatic synapses
Synapses can be classified as electrical or chemical

Neuron Classification By Structure

Unipolar (Pseudounipolar): Single short process, found in ganglia
Bipolar: Two processes (an axon and a dendrite), rare, found in some special sense organs (olfactory epithelium, retina)
Multipolar: Three or more processes, most common, found in neurons of the cerebrum and cerebellum

Neuron Classification By Function

Sensory (Afferent): Transmit impulses from sensory receptors toward the CNS, almost all are unipolar
Motor (Efferent): Carry impulses away from the CNS to effector organs (muscles, glands), multipolar
Interneurons: Lie between motor and sensory neurons, shuttle signals through CNS pathways (integration), almost all are multipolar

Neuron Distribution

Gray matter: Contains cell bodies of neurons, dendrites, and terminations of axons arriving at the region
White matter: Primarily composed of myelinated axons

Cerebral Cortex

Has gray matter in the outer zone of the brain hemispheres
Receives and analyzes sensory information from the body and initiates voluntary motor activity
Involved in learning and memory
Cells are arranged in six major layers

Cerebral Cortex Cell Types

Pyramidal cell: Somatic shape is roughly triangular with a large vesicle-containing nucleus and abundant Nissl bodies
Stellate or granule cell: Relatively small with numerous dendrites and a single short axon
Horizontal cells: Primarily confined to one layer of the cortex, fusiform with radiating dendrites and short axons radiating in opposite directions

Cerebellar Cortex

Receives information from the eyes, ears, and stretch receptors of the muscles
Plays a crucial role in coordination, maintenance of balance, and posture

Cerebellar Cortex Layers

Molecular layer: Contains few small neurons and many unmyelinated nerve fibers
Middle layer: Consists of a single layer of large Purkinje cells
Granule cell layer: Contains closely packed small cells with short dendrites and a single axon

Spinal Cord

Receives motor commands from the brain and relays them to muscles and other effectors via spinal nerves
Sensory fibers enter the cord through the dorsal root
Motor fibers leave through the ventral root
Spinal nerves are formed by the joining of dorsal and ventral roots

Spinal Cord Structure

Gray matter is H-shaped and contains nerve cell bodies and their dendrites
White matter surrounds gray matter and consists of dorsal, lateral, and ventral columns

Neuroglial Cells

Astrocytes: Support structure, repair processes, form the blood-brain barrier, regulate metabolic exchange
Oligodendrocytes: Produce myelin, provide electrical insulation
Schwann cells: Produce myelin, provide electrical insulation
Ependymal cells: Line cavities of the CNS
Microglia: Macrophagic activity

Organization of the Nervous System

Autonomic Nervous System (ANS): Thoracolumbar division is associated with the sympathetic division of the ANS

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Description

Explore the fundamental structures and functions of the nervous system in this quiz. Learn about the divisions of the nervous system, the role of neurons, and how nerve cell processes facilitate communication. Test your knowledge of neuroglia and neuronal characteristics.