Peripheral Nervous System Overview

Questions and Answers

What does PNS stand for?

Primary Nerve System

Peripheral Nervous System (correct)

Prolonged Nervous System

Pulling Nerve System

What are the components of the PNS?

Nerves, ganglia, enteric plexuses, and sensory receptors.

What are ganglia?

Small masses of nervous tissue, primarily consisting of neuron cell bodies, located outside of the brain and spinal cord.

What are enteric plexuses?

Extensive networks of neurons located in the walls of the gastrointestinal tract. Signup and view all the answers

What does SNS consist of?

(1) Sensory neurons that convey information to the CNS from somatic receptors and (2) motor neurons that conduct impulses from the CNS to skeletal muscles. Signup and view all the answers

What does ANS consist of?

(1) Sensory neurons that convey information to the CNS from autonomic sensory receptors and (2) motor neurons that conduct nerve impulses to smooth muscle, cardiac muscle, and glands. Signup and view all the answers

What are the two divisions of the motor part of the ANS?

Sympathetic division and parasympathetic division. Signup and view all the answers

Neurons undergo mitotic division.

False Signup and view all the answers

What is the difference between neuroglia and neurons?

Neuroglia are smaller cells that support, nourish, and protect neurons and continue to divide throughout life, while neurons do not. Signup and view all the answers

What does the neuron cell body contain?

A nucleus surrounded by cytoplasm with typical cellular organelles. Signup and view all the answers

What are Nissl bodies?

Areas in neuronal cell bodies that contain free ribosomes and rough endoplasmic reticulum. Signup and view all the answers

What is the function of newly synthesized proteins produced by Nissl bodies?

To replace cellular components, aid in neuron growth, and regenerate damaged axons. Signup and view all the answers

What does the cytoskeleton include?

Neurofibrils and microtubules. Signup and view all the answers

What is lipofuscin?

A pigment that occurs as yellowish-brown granules in the cytoplasm, a product of neuronal lysosomes. Signup and view all the answers

What is the general term for any neuronal process that emerges from the cell body?

Nerve fiber. Signup and view all the answers

What is the axon hillock?

The cone-shaped elevation at which the axon joins the cell body. Signup and view all the answers

What is the initial segment of the axon?

The part of the axon closest to the axon hillock. Signup and view all the answers

What is the trigger zone?

The junction of the axon hillock and the initial segment where nerve impulses arise. Signup and view all the answers

What does the axon contain?

Mitochondria, microtubules, and neurofibrils. Signup and view all the answers

What does the dendrite cytoplasm contain?

Nissl bodies, mitochondria, and other organelles. Signup and view all the answers

What is axoplasm?

Cytoplasm of an axon. Signup and view all the answers

What is the axolemma?

The membrane that surrounds the axoplasm. Signup and view all the answers

What are axon collaterals?

Side branches along the length of an axon. Signup and view all the answers

What are synaptic end bulbs?

Tips of some axon terminals that swell into bulb-shaped structures. Signup and view all the answers

What are varicosities?

Axon terminals that exhibit a string of swollen bumps. Signup and view all the answers

What stores neurotransmitters?

Synaptic vesicles contained by both bulbs and varicosities. Signup and view all the answers

What is slow axonal transport?

It conveys axoplasm in one direction only, from the cell body toward the axon terminals. Signup and view all the answers

What is fast axonal transport?

A mechanism capable of moving materials a distance of 200-400 mm per day. Signup and view all the answers

What is anterograde transport?

Fast axonal transport in a forward direction, moving organelles from the cell body to axon terminals. Signup and view all the answers

What is retrograde transport?

Fast axonal transport in backward direction, moving materials from the axon terminals to the cell body. Signup and view all the answers

What are multipolar neurons?

Neurons that usually have several dendrites and one axon. Signup and view all the answers

What are bipolar neurons?

Neurons that have one main dendrite and one axon. Signup and view all the answers

What are unipolar neurons?

Neurons with dendrites and one axon fused to form a continuous process. Signup and view all the answers

Where is the trigger zone for nerve impulses in a unipolar neuron?

At the junction of the dendrites and axon. Signup and view all the answers

What are Purkinje cells?

Neurons located in the cerebellum. Signup and view all the answers

What are pyramidal cells?

Neurons found in the cerebral cortex with pyramid-shaped cell bodies. Signup and view all the answers

What are the functional classifications of neurons?

<ol> <li>Sensory neurons (afferent), 2. Motor neurons (efferent), 3. Interneurons.</li> </ol> Signup and view all the answers

What are gliomas?

Brain tumors derived from glia. Signup and view all the answers

What neuroglia are found in the CNS?

Astrocytes, oligodendrocytes, microglia, and ependymal cells. Signup and view all the answers

What neuroglia are found in the PNS?

Schwann cells and satellite cells. Signup and view all the answers

What are the functions of astrocytes?

Support neurons, maintain blood-brain barrier, and regulate the environment for nerve impulses. Signup and view all the answers

What are protoplasmic astrocytes?

Astrocytes with many short branching processes found in gray matter. Signup and view all the answers

What are fibrous astrocytes?

Astrocytes with long unbranched processes predominantly located in white matter. Signup and view all the answers

What do the processes of astrocytes contact?

Blood capillaries, neurons, and the pia mater. Signup and view all the answers

What is the role of oligodendrocytes?

To form and maintain the myelin sheath around CNS axons. Signup and view all the answers

What do microglial cells function as?

Phagocytes. Signup and view all the answers

Where are ependymal cells located?

They line the ventricles of the brain and central canal of the spinal cord. Signup and view all the answers

What do ependymal cells produce?

Cerebrospinal fluid. Signup and view all the answers

What are Schwann cells responsible for?

Encircling PNS axons and forming the myelin sheath. Signup and view all the answers

What does each Schwann cell myelinate?

A single axon. Signup and view all the answers

What are satellite cells?

Flat cells that surround the cell bodies of neurons in PNS ganglia. Signup and view all the answers

What two types of neuroglia produce myelin sheaths?

Schwann cells in the PNS and oligodendrocytes in the CNS. Signup and view all the answers

What is neurolemma?

The outer peripheral, nucleated cytoplasmic layer of the Schwann cell. Signup and view all the answers

How does the neurolemma aid regeneration when an axon is injured?

By forming a regeneration tube that guides and stimulates regrowth of the axon. Signup and view all the answers

What are nodes of Ranvier?

Gaps in the myelin sheath that appear at intervals along the axon. Signup and view all the answers

What is a tract?

A bundle of axons located in the CNS. Signup and view all the answers

What is white matter composed of?

Primarily myelinated axons. Signup and view all the answers

What does grey matter contain?

Neuronal cell bodies, dendrites, unmyelinated axons, axon terminals, and neuroglia. Signup and view all the answers

Study Notes

Peripheral Nervous System (PNS)

PNS includes all nervous tissue outside the central nervous system (CNS).
It is categorized into three divisions: Somatic Nervous System (SNS), Autonomic Nervous System (ANS), and Enteric Nervous System (ENS).

Components of the PNS

Major components are nerves, ganglia, enteric plexuses, and sensory receptors.

Ganglia

Small clusters of neuron cell bodies situated outside the brain and spinal cord.

Enteric Plexuses

Networks of neurons located within the gastrointestinal tract, aiding in digestive regulation.

Somatic Nervous System (SNS)

Composed of sensory neurons that transmit information from somatic receptors to the CNS and motor neurons that direct voluntary movement to skeletal muscles.

Autonomic Nervous System (ANS)

Contains sensory neurons that relay information from autonomic sensory receptors; motor neurons control involuntary actions in smooth muscle, cardiac muscle, and glands.

Sensory Neurons of the ENS

Monitor chemical changes and stretching in the GI tract, regulating contractions and secretions for digestion.

Neuroglia vs. Neurons

Neuroglia are smaller but significantly outnumber neurons, providing support and protection. Unlike neurons, they can divide throughout life.

Neuron Structure

Neuron cell bodies house a nucleus, cytoplasm, and organelles like lysosomes and mitochondria.
Nissl bodies are clusters of ribosomes and rough endoplasmic reticulum in the cell bodies, involved in protein synthesis.

Neuron Processes

Axon hillock is where the axon joins the cell body, serving as a critical site for impulse generation.
Axons can have collaterals, which are side branches, and they terminate in synaptic end bulbs or varicosities that store neurotransmitters.

Axonal Transport

Slow axonal transport moves materials from the cell body towards axon terminals at a rate of 1-5 mm/day.
Fast axonal transport can move materials at speeds of 200-400 mm/day and occurs in both anterograde (cell body to axon terminal) and retrograde (axon terminal to cell body) directions.

Neuron Types

Multipolar neurons possess multiple dendrites and an axon, mostly found in the CNS.
Bipolar neurons have one axon and one main dendrite, located in sensory structures such as the retina.
Unipolar neurons have fused dendrites and an axon; their trigger zone is where dendrites meet the axon.

Glial Cells

Gliomas are tumors originating from glial cells.
CNS glial cells include astrocytes, oligodendrocytes, microglia, and ependymal cells.
PNS glial cells consist of Schwann and satellite cells.

Astrocytes

Largest glial cells with star-like shapes, they create a blood-brain barrier to protect neurons and maintain the chemical environment.

Oligodendrocytes

Form and maintain the myelin sheath around CNS axons; crucial for insulating and speeding up neural impulses.

Microglial Cells

Act as immune defense in the CNS, removing debris and responding to injury.

Ependymal Cells

Line the brain's ventricles and the central canal of the spinal cord, involved in cerebrospinal fluid production and circulation.

Schwann Cells

Form myelin sheaths around PNS axons and facilitate regeneration after nerve injury.

Nodes of Ranvier

Gaps in the myelin sheath crucial for the rapid conduction of nerve impulses.

CNS vs. PNS Structure

White matter is primarily composed of myelinated axons, while gray matter consists of neuronal cell bodies and unmyelinated axons, giving it a grayish appearance due to the presence of Nissl bodies.

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Description

Explore the key components and functions of the Peripheral Nervous System (PNS). This quiz covers the divisions of the PNS, including the Somatic, Autonomic, and Enteric Nervous Systems, as well as the roles of various components like ganglia and sensory receptors.