Introduction to the Nervous System

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Questions and Answers

What is the term used for the space between the presynaptic neurone and the postsynaptic neurone?

Neurotransmitter gap

Synaptic cleft (correct)

Synaptic junction

Synaptic terminal

Which structure stores neurotransmitters in the presynaptic neurone?

Receptor sites

Synaptic knobs (correct)

Dendrites

Axon terminal

What occurs in response to an action potential at the synapse?

Neurotransmitters are synthesized

Neurotransmitters bind to presynaptic receptors

Neurotransmitters are released by exocytosis (correct)

Neurotransmitters diffuse into the nucleus

How many neurones are typically involved in autonomic nervous system efferent impulses to reach the effector tissue?

Two Signup and view all the answers

What is primarily stimulated by somatic nerves?

Skeletal muscles Signup and view all the answers

What are the two main divisions of the nervous system?

Central nervous system and peripheral nervous system Signup and view all the answers

Which type of nerves are responsible for transmitting impulses to the central nervous system?

Afferent nerves Signup and view all the answers

Which part of the nervous system controls voluntary movements of skeletal muscles?

Somatic nervous system Signup and view all the answers

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

Supporting and protecting neurons Signup and view all the answers

What is the role of the autonomic nervous system?

Managing involuntary processes in the body Signup and view all the answers

How do neurons obtain energy for their functions?

Only from glucose Signup and view all the answers

What forms the grey matter of the nervous system?

Cell bodies of neurons Signup and view all the answers

Which component of the peripheral nervous system is responsible for involuntary actions like heartbeat?

Autonomic nervous system Signup and view all the answers

What are groups of cell bodies called in the peripheral nervous system?

Ganglia Signup and view all the answers

Which structure is responsible for carrying impulses away from the cell body?

Axons Signup and view all the answers

What is the outermost layer of the Schwann cell plasma membrane called?

Neurilemma Signup and view all the answers

What type of neurons are faster at transmitting nerve impulses?

Myelinated neurons Signup and view all the answers

What primarily determines the transmission speed of nerve impulses in unmyelinated fibers?

The absence of myelin sheath Signup and view all the answers

How many axons are embedded within a Schwann cell in unmyelinated neurons?

Several Signup and view all the answers

What role do dendrites play in motor neurons?

They form part of synapses Signup and view all the answers

What is the relationship between two neurons during the transmission of a nerve impulse?

There is no physical contact Signup and view all the answers

Study Notes

Nervous System Introduction

The nervous system detects and responds to internal and external changes in the body.
Coordinates and controls vital bodily functions alongside the endocrine system to maintain homeostasis.

Nervous System Divisions

Consists of the central nervous system (CNS) and the peripheral nervous system (PNS).
The CNS encompasses the brain and spinal cord.
The PNS includes all nerves outside the brain and spinal cord.
PNS is composed of paired cranial and spinal nerves.

Peripheral Nervous System Functions

Sensory (afferent) nerves transmit impulses to the CNS.
Motor (efferent) nerves transmit impulses from the CNS.
Mixed nerves (spinal nerves) include both sensory and motor components.

Peripheral Nervous System Divisions

Sensory division transmits sensory information from the body to the CNS.
Motor division transmits motor commands from the CNS to the body.
Somatic nervous system controls voluntary movements of skeletal muscles.
Autonomic nervous system regulates involuntary processes such as heart rate, digestion, and glandular activity.

Autonomic Nervous System Divisions

Sympathetic nervous system prepares the body for "fight-or-flight" responses.
Parasympathetic nervous system promotes "rest-and-digest" functions.

Cells and Tissues of the Nervous System

Nervous tissue consists of neurons and neuroglia.
Neurons (nerve cells) generate and transmit nerve impulses.
Neuroglia is connective tissue supporting neurons, composed of various glial cells.
Glial cells are significantly more numerous than neurons, outnumbering them by tenfold.

Neuron Structure

Each neuron comprises a cell body and its processes, including an axon and multiple dendrites.
Bundles of axons are known as nerves.
Neurons cannot divide and require continuous oxygen and glucose supply for survival.

Neuron Components

Cell bodies form the grey matter of the nervous system, located at the brain's periphery and the spinal cord's center.
Groups of cell bodies are termed nuclei in the CNS and ganglia in the PNS.
Axons and dendrites form the white matter of the nervous system.
Axons are found deep within the brain and in groups called tracts at the spinal cord's periphery.
They are referred to as nerves or nerve fibers outside of the brain and spinal cord.

Axon Structure

Each neuron has only one axon, originating at the axon hillock, a tapered region of the cell body.
Axons carry impulses away from the cell body and are usually longer than dendrites, sometimes reaching 100 cm in length.
The axon membrane is called the axolemma, enclosing the cytoplasm extending from the cell body.

Myelinated Neurons

Large axons and those in peripheral nerves are enveloped by a myelin sheath.
This sheath comprises Schwann cells arranged along the axon's length.
Each Schwann cell wraps around the axon, creating concentric layers of its plasma membrane.
Between the plasma membrane layers is myelin, a fatty substance.
The outermost layer of Schwann cell plasma membrane is the neurilemma.
There are tiny areas of exposed axolemma between adjacent Schwann cells called nodes of Ranvier, aiding in the rapid transmission of nerve impulses in myelinated neurons.

Unmyelinated Neurons

Multiple axons are embedded within a single Schwann cell.
Schwann cells are closely associated, and there is no exposed axolemma.
Nerve impulse transmission is significantly slower in unmyelinated fibers.

Dendrite Structure

Dendrites are numerous, short processes that receive and carry incoming impulses towards the cell body.
They share the same structure as axons but are typically shorter and branching.
In motor neurons, dendrites are involved in synapses.
In sensory neurons, they form sensory receptors responsible for responding to specific stimuli.

Synapse and Neurotransmitters

Multiple neurons are involved in transmitting a nerve impulse from its origin to its destination, whether sensory or motor.
Physical contact between neurons is absent.
The synapse is the point where the nerve impulse transfers from the presynaptic neuron to the postsynaptic neuron.

Synaptic Junction

The axon of the presynaptic neuron branches at its free end, terminating in small swellings called synaptic knobs or terminal boutons.
These boutons are in close proximity to the dendrites and cell body of the postsynaptic neuron.
The space between them is the synaptic cleft.
Synaptic knobs contain spherical membrane-bound synaptic vesicles, which store neurotransmitters, chemical substances released into the synaptic cleft.

Neurotransmitter Function

Neurotransmitters are synthesized by nerve cell bodies, transported actively along axons, and stored in synaptic vesicles.
They are released by exocytosis in response to the action potential and diffuse across the synaptic cleft.
They act on specific receptor sites on the postsynaptic membrane.
Somatic nerves carry impulses directly to synapses at skeletal muscles, the neuromuscular junctions, stimulating contraction.
In the autonomic nervous system, efferent impulses travel along two neurons (preganglionic and postganglionic) and across two synapses to the effector tissue, including cardiac muscle, smooth muscle, and glands, in both the sympathetic and parasympathetic divisions.

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Description

Explore the basics of the nervous system, including its functions and divisions. Learn about the central and peripheral nervous systems, and how they work together to maintain bodily functions. This quiz will test your understanding of the sensory and motor divisions, as well as the roles of various nerves.