Nervous System Overview

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Questions and Answers

What is the primary function of dendrites in a neuron?

Receive impulses and transmit them to the soma (correct)

Produce neurotransmitters for signal transmission

Provide structural support for the neuron

Transmit impulses away from the soma

Which type of neuro-glial cell is responsible for forming the myelin sheath in the central nervous system?

Oligodendrocytes (correct)

Astrocytes

Ependymal cells

Microglia

Which of the following best describes unipolar neurons?

Neurons that function exclusively as motor neurons

Neurons with a single process that branches into two parts (correct)

Neurons with multiple processes extending from the cell body

Neurons that have two distinct processes, one axon and one dendrite

What is the main distinction between motor and sensory neurons?

Motor neurons transmit impulses from the central nervous system to muscles, while sensory neurons transmit impulses from sensory receptors to the central nervous system Signup and view all the answers

Which of the following describes a characteristic of amacrine cells?

They are considered sensory neurons in the retina Signup and view all the answers

What is the main role of the anterior ramus compared to the posterior ramus?

It is involved in the formation of plexuses. Signup and view all the answers

Which type of fibers originate from the sympathetic nervous system?

Pre-ganglionic fibers from thoraco-lumbar segments T1 to L2. Signup and view all the answers

What is the primary function of a synapse?

To facilitate contact between nerve cells and effector organs Signup and view all the answers

Which function is primarily associated with the parasympathetic nervous system?

Constrict the pupil. Signup and view all the answers

What distinguishes post-ganglionic fibers of the sympathetic nervous system?

They are located laterally to the vertebral column. Signup and view all the answers

Which structure is formed at the end of an axon in a synapse?

Axon terminal Signup and view all the answers

What are the two main types of synaptic connections?

Axo-dendritic and Axo-somatic Signup and view all the answers

Which of the following is a characteristic of the sympathetic nervous system?

It increases heart rate. Signup and view all the answers

Which part of the brain is primarily responsible for balance and equilibrium?

Cerebellum Signup and view all the answers

What is the origin of the pre-ganglionic fibers in the parasympathetic nervous system?

From the cranial nerves and sacral segments. Signup and view all the answers

What action does the sympathetic nervous system NOT perform?

Decrease heart rate. Signup and view all the answers

How many segments does the spinal cord have in total?

31 segments Signup and view all the answers

At which vertebral level does the spinal cord end in adults?

L1 Signup and view all the answers

Which aspect distinguishes the cranio-sacral division from the thoraco-lumbar division?

It is involved in cranial nerve functions. Signup and view all the answers

What is the outermost layer of the meninges surrounding the central nervous system?

Dura mater Signup and view all the answers

Which part of the nervous system is formed by the brain and spinal cord?

Central nervous system Signup and view all the answers

Which cranial nerve is responsible for vision?

Optic Signup and view all the answers

Where is cerebro-spinal fluid (CSF) primarily located?

In the brain ventricles Signup and view all the answers

Which of the following cranial nerves is not involved in eye movement?

Optic Signup and view all the answers

What is the function of the trigeminal nerve?

Face sensation Signup and view all the answers

How many pairs of cranial nerves are there in the human body?

12 pairs Signup and view all the answers

What type of root forms the dorsal sensory root of a spinal nerve?

Central processes of dorsal root ganglion Signup and view all the answers

Which area of the central nervous system does the 3rd ventricle reside in?

Diencephalon Signup and view all the answers

Which of the following statements about spinal nerves is correct?

Spinal nerves are formed by the fusion of dorsal and ventral roots Signup and view all the answers

Which type of neuron has only one process extending from its cell body?

Unipolar neuron Signup and view all the answers

What is the primary function of oligodendrocytes in the nervous system?

Form myelin sheath in the CNS Signup and view all the answers

In which part of the nervous system would you find satellite cells?

Peripheral nervous system Signup and view all the answers

The types of neurons classified by function include which of the following?

Motor, sensory, and mixed Signup and view all the answers

Which of the following is true regarding the processes of a neuron?

Dendrites are short and branching Signup and view all the answers

What distinguishes the axo-somatic synaptic connection from other types of synapses?

Connection occurs between the axon and the cell body of another neuron Signup and view all the answers

Which structure is NOT part of the central nervous system?

Peripheral nerves Signup and view all the answers

At what vertebral level does the spinal cord typically end in infants?

L3 Signup and view all the answers

Which layer is considered the innermost layer of the meninges?

Pia Signup and view all the answers

Which part of the brainstem is involved in regulating heart rate and blood pressure?

Medulla oblongata Signup and view all the answers

How many total segments is the spinal cord composed of?

31 Signup and view all the answers

Which component is NOT included in the structure of the cerebrum?

Thalamus Signup and view all the answers

What is the primary function of the cerebellum?

Coordination and balance Signup and view all the answers

What characteristic does the anterior ramus have compared to the posterior ramus?

Attached to the sympathetic chain Signup and view all the answers

Which of the following statements correctly describes the origin of pre-ganglionic fibers in the sympathetic nervous system?

They originate from spinal cord segments T1 to L2. Signup and view all the answers

What is one of the primary effects of the sympathetic nervous system?

Elevated respiratory rate Signup and view all the answers

What role does the parasympathetic nervous system play in the body?

It relaxes the sphincters. Signup and view all the answers

How do post-ganglionic fibers differ in the sympathetic and parasympathetic nervous systems?

Sympathetic post-ganglionic fibers are longer and derived from the sympathetic chain. Signup and view all the answers

Which of the following best describes the autonomic nervous system's sympathetic division?

It is thoraco-lumbar in origin. Signup and view all the answers

What is a notable function of the cranio-sacral part of the parasympathetic nervous system?

Promotes urination. Signup and view all the answers

In terms of segmentation, which spinal segments are associated with the origin of sympathetic pre-ganglionic fibers?

T1 to L2 Signup and view all the answers

What is the primary function of the olfactory nerve?

Smell Signup and view all the answers

Which cranial nerve is associated with eye movement and originates from the midbrain?

Trochlear Signup and view all the answers

Which ventricle is located in the diencephalon?

3rd ventricle Signup and view all the answers

Which of the following cranial nerves is responsible for hearing and balance?

Vestibulocochlear nerve Signup and view all the answers

How many pairs of spinal nerves are there in total?

31 Signup and view all the answers

What forms the ventral motor root of a spinal nerve?

Axons of lateral horn cells and anterior horn cells Signup and view all the answers

Which of the following cranial nerves does not arise from the brainstem?

Olfactory nerve Signup and view all the answers

Which root contains the central processes of the dorsal root ganglion?

Dorsal sensory root Signup and view all the answers

What structural feature distinguishes an axon from dendrites in a neuron?

An axon is typically long and single, while dendrites are short and branching. Signup and view all the answers

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

Astrocytes act as supporting cells that provide structural support and help maintain the blood-brain barrier. Signup and view all the answers

How do unipolar neurons differ from bipolar neurons in terms of structure?

Unipolar neurons have a single process that splits into two branches, while bipolar neurons have two distinct processes: one dendrite and one axon. Signup and view all the answers

Identify one type of neuro-glial cell in the peripheral nervous system and its function.

Schwann cells are responsible for forming the myelin sheath in the peripheral nervous system. Signup and view all the answers

Define the difference between a nucleus and a ganglion in the nervous system.

A nucleus is a collection of nerve cells located within the central nervous system, while a ganglion is a collection of nerve cells located outside the central nervous system. Signup and view all the answers

What forms the dorsal sensory root of a spinal nerve?

The dorsal sensory root is formed by the central processes of the dorsal root ganglion. Signup and view all the answers

Which cranial nerve is responsible for eye movement besides the oculomotor nerve?

The trochlear and abducent nerves are also responsible for eye movement. Signup and view all the answers

Identify the location of the third ventricle.

The third ventricle is located in the diencephalon. Signup and view all the answers

What is the total number of pairs of spinal nerves in the human body?

There are 31 pairs of spinal nerves. Signup and view all the answers

What is the main difference in the attachment of the anterior ramus compared to the posterior ramus?

The anterior ramus is attached to the sympathetic chain, while the posterior ramus is not. Signup and view all the answers

What is the function of the facial nerve?

The facial nerve is responsible for controlling the muscles of facial expression. Signup and view all the answers

Where do most cranial nerves emerge from?

Most cranial nerves emerge from the brainstem. Signup and view all the answers

Identify the two locations where pre-ganglionic fibers originate in the autonomic nervous system.

Pre-ganglionic fibers originate from the spinal cord segments T1 to L2 in the sympathetic system and from cranial nerves and sacral segments in the parasympathetic system. Signup and view all the answers

Which type of axons do the ventral motor roots contain?

The ventral motor roots contain axons of anterior horn cells (to skeletal muscles) and lateral horn cells (to smooth muscles). Signup and view all the answers

How do post-ganglionic fibers differ between the sympathetic and parasympathetic nervous systems?

Post-ganglionic fibers from the sympathetic system emerge from the sympathetic chain, while those from the parasympathetic system arise from ganglia near the target organs. Signup and view all the answers

What are the primary functions associated with the sympathetic nervous system?

The sympathetic nervous system increases heart rate and respiratory rate, dilates the pupils, and decreases intestinal movement. Signup and view all the answers

What is one function of the vestibulocochlear nerve?

The vestibulocochlear nerve is responsible for hearing and balance. Signup and view all the answers

Describe the role of the cranio-sacral part of the parasympathetic nervous system.

The cranio-sacral part decreases heart rate, constricts the pupils, and increases intestinal movement. Signup and view all the answers

What is the significance of the anterior ramus being larger than the posterior ramus?

The larger size of the anterior ramus allows it to participate in the formation of plexuses and innervate more structures. Signup and view all the answers

In which segments of the spinal cord are sympathetic pre-ganglionic fibers located?

Sympathetic pre-ganglionic fibers are located in the lateral horn cells of spinal cord segments T1 to L2. Signup and view all the answers

What effect do post-ganglionic fibers of the sympathetic nervous system have on the body?

They prepare the body for stressful situations by increasing physiological activities such as heart rate and respiration. Signup and view all the answers

What are the three main parts of the brain and their primary functions?

The three main parts are the cerebrum (higher cognitive functions), cerebellum (balance and coordination), and brain stem (regulation of fundamental life functions). Signup and view all the answers

Describe the segmentation of the spinal cord and the number of segments in each region.

The spinal cord has 31 segments: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. Signup and view all the answers

What are the three layers of meninges that surround the central nervous system?

The three layers are the pia mater (innermost), arachnoid mater (middle), and dura mater (outermost). Signup and view all the answers

Explain the embryological classification of the nervous system.

The nervous system is classified into three parts: forebrain, midbrain, and hindbrain, with the hindbrain consisting of the pons, medulla, and cerebellum. Signup and view all the answers

What is the primary role of the synaptic cleft in neuronal communication?

The synaptic cleft facilitates the transmission of neurotransmitters between the pre-synaptic and post-synaptic elements, enabling signals to cross neurons. Signup and view all the answers

Identify the locations where the spinal cord ends in newborns and adults.

In newborns, the spinal cord ends at the level of L3, while in adults, it typically ends at L1. Signup and view all the answers

What structures make up the diencephalon, and what are their functions?

The diencephalon is made up of the thalamus (sensory relay center) and hypothalamus (regulates homeostasis and endocrine functions). Signup and view all the answers

What is the significance of synaptic types like axo-dendritic and axo-somatic connections?

Axo-dendritic connections occur between an axon and a dendrite, while axo-somatic connections occur between an axon and a neuron’s cell body, influencing synaptic strength and signaling. Signup and view all the answers

What are the primary functions of neuroglial cells in the nervous system?

They provide support, protection, and insulation for neurons, as well as participate in the maintenance of homeostasis. Signup and view all the answers

Explain the key differences between unipolar, bipolar, and multipolar neurons.

Unipolar neurons have one process, bipolar have two, and multipolar neurons have multiple processes extending from the cell body. Signup and view all the answers

Describe the roles of astrocytes and microglia in the central nervous system.

Astrocytes support and maintain the blood-brain barrier, while microglia are phagocytic cells that respond to injury and infection. Signup and view all the answers

What distinguishes the processes of an axon from those of dendrites?

An axon is long and singular, transmitting impulses away from the soma, whereas dendrites are short and branching, transmitting impulses to the soma. Signup and view all the answers

How do the structures of oligodendrocytes and Schwann cells differ regarding myelin formation?

Oligodendrocytes form myelin sheaths in the central nervous system and can myelinate multiple axons, while Schwann cells do so in the peripheral nervous system and typically myelinate only one axon. Signup and view all the answers

What structures are part of the central nervous system?

The central nervous system consists of the brain and spinal cord. Signup and view all the answers

Describe the spinal cord's length and segment composition.

The spinal cord is approximately 45 cm long in males and has 31 segments: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. Signup and view all the answers

Where does the spinal cord begin and end in adults?

The spinal cord begins at the level of the medulla oblongata and typically ends at the level of L1. Signup and view all the answers

What components make up the meninges surrounding the central nervous system?

The meninges consist of three layers: Pia mater, Arachnoid mater, and Dura mater. Signup and view all the answers

Identify the parts of the brain formed embryologically.

Embryologically, the brain is divided into the forebrain, midbrain, and hindbrain. Signup and view all the answers

What are the functions of the cerebellum?

The cerebellum is responsible for coordinating movement and maintaining balance and equilibrium. Signup and view all the answers

What is the difference between axo-dendritic and axo-somatic synaptic connections?

Axo-dendritic connections occur between the axon of one neuron and the dendrite of another, while axo-somatic connections occur between the axon and the cell body of a neuron. Signup and view all the answers

Which areas of the brain are included in the diencephalon?

The diencephalon includes the thalamus and hypothalamus. Signup and view all the answers

What is the primary distinction between the posterior ramus and the anterior ramus in relation to plexus formation?

The posterior ramus does not participate in plexus formation, while the anterior ramus is involved in forming plexuses. Signup and view all the answers

Describe the origin and function of post-ganglionic fibers in the sympathetic nervous system.

Post-ganglionic fibers originate from the sympathetic chain and are responsible for controlling various involuntary functions such as increasing heart rate. Signup and view all the answers

In what spinal cord segments do the pre-ganglionic fibers of the sympathetic nervous system originate?

Pre-ganglionic fibers originate from the lateral horns of spinal cord segments T1 to L2. Signup and view all the answers

What are the main effects of the parasympathetic nervous system on heart rate and intestinal movement?

The parasympathetic nervous system decreases heart rate and increases intestinal movement. Signup and view all the answers

How do the origins of pre-ganglionic fibers differ between the sympathetic and parasympathetic nervous systems?

Sympathetic pre-ganglionic fibers originate from T1 to L2, while parasympathetic fibers originate from cranial nerves and sacral segments S2, S3, and S4. Signup and view all the answers

What role does the sympathetic nervous system play in pupil dilation and sphincter control?

The sympathetic nervous system dilates the pupil and contracts the sphincters. Signup and view all the answers

Identify the two parts of the autonomic nervous system and their general functions.

The autonomic nervous system consists of the sympathetic and parasympathetic divisions, with the sympathetic preparing the body for action and the parasympathetic promoting rest and recovery. Signup and view all the answers

What specific areas do the post-ganglionic fibers of the parasympathetic nervous system target?

Parasympathetic post-ganglionic fibers target ganglia located near or in the organs they innervate. Signup and view all the answers

What are the three main categories of cranial nerves based on their functions?

Cranial nerves can be categorized as sensory, motor, and mixed nerves. Signup and view all the answers

Identify the origin and function of the facial cranial nerve.

The facial nerve originates from the pons and is responsible for controlling face muscles. Signup and view all the answers

Describe the structure that forms the trunk of a spinal nerve.

The trunk of a spinal nerve is formed by the unification of the dorsal sensory root and the ventral motor root. Signup and view all the answers

What distinguishes the origin of the olfactory and optic nerves from the other cranial nerves?

The olfactory nerve originates from the nose, while the optic nerve originates from the retina; both arise directly from the brain rather than the brainstem. Signup and view all the answers

What is the total number of spinal nerve pairs, and how are they distributed among the cervical, thoracic, lumbar, sacral, and coccygeal regions?

There are 31 pairs of spinal nerves distributed as 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. Signup and view all the answers

Explain the main role of the trigeminal cranial nerve.

The trigeminal nerve primarily serves facial sensation. Signup and view all the answers

In terms of location, where is cerebro-spinal fluid primarily found within the brain?

Cerebro-spinal fluid is primarily found in the brain ventricles, specifically the lateral, third, and fourth ventricles. Signup and view all the answers

What components contribute to the formation of the dorsal sensory root in spinal nerves?

The dorsal sensory root is formed by the central processes of dorsal root ganglion neurons. Signup and view all the answers

Study Notes

Branches of the Trunk

The trunk is divided into two branches: Posterior Ramus and Anterior Ramus.
The Posterior Ramus is small, runs backward, and does not participate in plexus formation.
The Anterior Ramus is large, runs forward, and participates in the formation of plexuses.
Only the Anterior Ramus is attached to the sympathetic chain.

Nervous system

The nervous system is divided into two main parts: the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).
The CNS consists of the brain and spinal cord.
The PNS consists of the cranial nerves and spinal nerves.

Autonomic Nervous System

The autonomic nervous system controls involuntary functions such as heart rate, digestion, and breathing.
It is divided into two branches: the sympathetic and parasympathetic nervous systems.
The sympathetic nervous system is responsible for the "fight or flight" response.
The parasympathetic nervous system is responsible for the "rest and digest" response.

Nerve Cell (Neuron)

The neuron is the basic unit of the nervous system.
It consists of a cell body (soma), dendrites, and an axon.
The cell body contains the nucleus.
Dendrites are short, branching processes that transmit impulses to the soma.
The axon is a long, single process that transmits impulses away from the soma.

Types of Neurons

Neurons can be classified by size, function, and the number of processes.
By size: large (Golgi type I) and small (Golgi type II).
By function: motor, sensory, and mixed.
By number of processes: unipolar, bipolar, and multipolar.

Neuroglial Cells

Neuroglial cells support and protect neurons.
They are found in both the CNS and PNS.
In the CNS, they include astrocytes, oligodendrocytes, microglia, and ependymal cells.
In the PNS, they include satellite cells and Schwann cells.

Synapse

A synapse is a junction between two neurons or between a neuron and an effector organ (muscle or gland).
It consists of a presynaptic element, a synaptic cleft, and a postsynaptic element.
The presynaptic element is the end of the axon containing vesicles.
Types of synapses include axo-dendritic, axo-somatic, axo-axonic, and neuromuscular.

Brain

The brain is the control center of the nervous system.
It is anatomically divided into the cerebrum, cerebellum, and brain stem.
The cerebrum is the largest part of the brain and is responsible for higher-order functions such as thought, language, and memory.
It consists of two cerebral hemispheres.
The diencephalon is within the cerebrum and is composed of the thalamus and hypothalamus.
The cerebellum is responsible for balance and coordination.
The brain stem connects the brain to the spinal cord and controls vital functions such as breathing and heart rate.
The brain stem is composed of midbrain, pons, and medulla.

Embryological Development of the Brain

The brain develops from three primary vesicles: the forebrain, midbrain, and hindbrain.
The forebrain gives rise to the cerebrum and diencephalon.
The hindbrain gives rise to the pons, medulla, and cerebellum.

Spinal Cord

The spinal cord is a long, cylindrical structure that extends from the brain stem to the lumbar region of the vertebral column.
It is responsible for transmitting signals between the brain and the rest of the body.
It is about 45 cm long in males and 42 cm long in females.
It begins as a continuation of the medulla oblongata.
It ends at the level of L3 in newborns and L1 in adults.
It is divided into 31 segments: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.

Meninges

The CNS is surrounded by three layers of protective membranes called meninges.
These are the pia mater, arachnoid mater, and dura mater.
The pia mater is the innermost layer and is closely adhered to the surface of the brain and spinal cord.
The arachnoid mater is the middle layer and is a delicate membrane that is separated from the pia mater by the subarachnoid space, which contains cerebrospinal fluid.
The dura mater is the outermost layer and is a thick, tough membrane that forms a protective covering around the brain and spinal cord.

Cerebrospinal Fluid (CSF)

CSF is a clear, colorless fluid that circulates in the brain ventricles and the subarachnoid space.
It is produced by the ependymal cells in the ventricles.
It provides cushioning and protection for the brain and spinal cord.
It also helps to remove waste products from the CNS.
There are four ventricles in the brain: two lateral ventricles in each cerebral hemisphere, the third ventricle in the diencephalon, and the fourth ventricle in the hindbrain.

Cranial Nerves

There are 12 pairs of cranial nerves that arise from the brain stem, except for the olfactory and optic nerves.
They control sensory, motor, and autonomic functions in the head and neck.

Spinal Nerves

There are 31 pairs of spinal nerves that arise from the spinal cord.
Each spinal nerve arises from two roots: a dorsal sensory root and a ventral motor root.
The dorsal sensory root carries sensory information from the body to the spinal cord.
The ventral motor root carries motor commands from the spinal cord to the muscles.
The two roots unite to form the trunk of the spinal nerve.

Branches

Trunk is divided into posterior and anterior rami
Posterior ramus: small, runs backward, does not contribute to plexus formation
Anterior ramus: large, runs forward, contributes to plexus formation

Nervous System

Nervous system is formed of the Central Nervous System (CNS)
CNS includes the brain and spinal cord

Autonomic Nervous System

The autonomic nervous system controls involuntary actions like heart rate, digestion, and breathing.
It has two branches: sympathetic and parasympathetic

Sympathetic System

Sympathetic nervous system is also called the thoracolumbar system
Preganglionic fibers originate from lateral horn cells (LHCs) of spinal cord segments T1 to L2

Parasympathetic System

Parasympathetic nervous system is also called the craniosacral system
Preganglionic fibers originate from cranial nerves (10, 9, 7, and 3) and sacral segments S2, S3, and S4

Neuron

Neuron is the basic functional unit of nervous system.

Neuron Structure

Contains a cell body (soma) and processes
Processes are of two types: dendrites and axons

Dendrites

Short, branching, transmit impulses to the soma

Axons

Long, single, transmit impulses from the soma

Neuron Classification

By size: large (Golgi type I) and small (Golgi type II)
By function: motor, sensory, and mixed
By number of processes: unipolar, bipolar, and multipolar

Unipolar Neurons

Have one process that bifurcates into a peripheral branch and a central branch
True unipolar neurons are found in the amacrine cells of the retina.
Pseudo unipolar neurons are found in the dorsal root ganglion.

Bipolar Neurons

Have two processes: one dendrite and one axon.
Found in the olfactory nerve cells and cochlear and vestibular nerve cells.

Multipolar Neurons

Have multiple processes: one axon and multiple dendrites.
Examples include: anterior horn cells of the spinal cord and the motor neurons.

Neuroglial Cells

These are supporting cells found in the nervous system
They are responsible for structural support, insulation, and nutrient supply to neurons.

CNS Neuroglial cells

Astrocytes: supporting cells
Oligodendrocytes: form myelin sheath
Microglia: phagocytic cells
Ependymal: produce cerebrospinal fluid (CSF)

PNS Neuroglial Cells

Satellite cells: Supporting cells
Schwann cells: form myelin sheath

Synapse

Synapse is the point of contact between neurons, or between neurons and other cells (e.g., muscle or gland cells).
It enables communication and transmission of impulses.

Synapse Structure:

Presynaptic element: the end of an axon contains vesicles that store neurotransmitters
Synaptic cleft: a narrow space between the presynaptic and postsynaptic elements
Postsynaptic element: the receiving cell (e.g., another neuron, muscle cell)

Types Of Synapses

Axo-dendritic: between axon and dendrite
Axo-somatic: between axon and cell body
Axo-axonic: between axon and another axon
Neuro-muscular: between neuron and muscle fiber

### Classification of Nervous System

The nervous system is classified into two parts: Central Nervous System (CNS) and Peripheral Nervous System (PNS)

Central Nervous System (CNS)

Consists of the brain and the spinal cord
The brain is anatomically subdivided into the cerebrum, cerebellum, and brainstem
Embryologically, it is formed of the forebrain, midbrain, and hindbrain

Cerebrum

The cerebrum consists of two hemispheres and the diencephalon
The diencephalon is made up of the thalamus and hypothalamus.

Cerebellum

Responsible for equilibrium and muscle coordination

Brainstem

The brainstem is composed of the midbrain, pons, and medulla oblongata

Spinal Cord

The spinal cord is about 45 cm long in males and 42 cm long in females.
Begins as a continuation of the medulla oblongata
Ends at the level of L3 in newborns and L1 in adults
Has 31 segments: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal

Meninges

The CNS is protected by three layers of meninges:
- Pia mater: innermost layer
- Arachnoid mater: middle layer
- Dura mater: outermost layer

Cerebrospinal Fluid (CSF)

CSF circulates within the brain ventricles:
- Lateral ventricles: located within the cerebral hemispheres
- Third ventricle: located within the diencephalon
- Fourth ventricle: located within the hindbrain

Peripheral Nervous System (PNS)

Consists of the cranial nerves and spinal nerves
The PNS transmits information between the CNS and the rest of the body allowing for the body to respond to its environment
PNS is made up of two parts: the somatic nervous system and the autonomic nervous system

Cranial Nerves

12 pairs of nerves:
- Olfactory nerve (I): responsible for smell and originates from the nasal cavity
- Optic Nerve (II): responsible for vision and originates from the retina
- Oculomotor nerve (III): responsible for eye movement and originates from the midbrain
- Trochlear nerve (IV): responsible for eye movement and originates from the midbrain
- Trigeminal nerve (V): responsible for sensation on the face and originates from the pons
- Abducens nerve (VI): responsible for eye movement and originates from the pons
- Facial nerve (VII): responsible for facial muscles, taste, and salivary gland function and originates from the pons.
- Vestibulocochlear nerve (VIII): responsible for hearing and balance and originates from the pons
- Glossopharyngeal nerve (IX): responsible for taste, swallowing, and salivary gland function and originates from the medulla oblongata
- Vagus nerve (X): responsible for regulation of the heart, lungs, and digestive system and originates from the medulla oblongata
- Accessory nerve (XI): responsible for neck and shoulder muscles and originates from the medulla oblongata
- Hypoglossal nerve (XII): responsible for tongue movement and originates from the medulla oblongata

Spinal Nerves

31 pairs of spinal nerves:
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal

Formation of Spinal Nerves

Each spinal nerve is formed by the union of two roots:
- Dorsal (sensory) root: formed of central processes of dorsal root ganglion, carry sensory information to the CNS
- Ventral (motor) root: formed of axons of anterior horn cells (AHCs) and lateral horn cells (LHCs)
  - Axons of AHCs: innervate skeletal muscles
  - Axons of LHCs innervate smooth muscles

### Branches of the Trunk

The posterior ramus is small, runs backward, and does not participate in plexus formation.
The anterior ramus is large, runs forward, and participates in the formation of plexuses.
The posterior ramus is not attached to the sympathetic chain.
The anterior ramus is attached to the sympathetic chain.

### The Nervous System

The nervous system can be divided into the autonomic and somatic nervous systems.
The autonomic nervous system is further divided into the sympathetic and parasympathetic systems.

Autonomic Nervous System

The sympathetic nervous system is also known as the thoraco-lumbar system.
The sympathetic nervous system's pre-ganglionic fibers originate from the lateral horn cells (LHCs) of spinal cord segments T1 to L2.
The sympathetic nervous system's post-ganglionic fibers originate from the sympathetic chain, located lateral to the vertebral column.
The parasympathetic nervous system is also known as the cranio-sacral system.
The parasympathetic nervous system's pre-ganglionic fibers originate from cranial nerves 3, 7, 9, and 10, as well as spinal cord segments S2, S3, and S4.
The parasympathetic nervous system's post-ganglionic fibers originate from parasympathetic ganglia located close to the organs.
The sympathetic nervous system dilates the pupil, contracts sphincters, increases heart rate, increases respiratory rate, and decreases intestinal movement.
The parasympathetic nervous system constricts the pupil, relaxes sphincters, decreases heart rate, decreases respiratory rate, and increases intestinal movement.

### Structure of a Neuron

The cell body (soma) contains the nucleus.
Dendrites are short, branching, and transmit impulses towards the cell body.
Axons are long, single, and transmit impulses away from the cell body.

Types of Neurons Based on Size and Function

According to size: Neurons can be classified as large (Golgi type I) or small (Golgi type II).
According to function: Neurons can be classified as motor, sensory, or mixed.

### Types of Neurons Based on Number of Processes

Unipolar neurons: True unipolar neurons are found in the retina, while pseudo-unipolar neurons are found in the dorsal root ganglion.
Bipolar neurons: Examples include olfactory nerve cells and cochlear and vestibular nerve cells.
Multipolar neurons: Examples include anterior horn cells of the spinal cord.

### Neuroglial Cells

Astrocytes: Supporting cells in the central nervous system.
Oligodendrocytes: Form the myelin sheath in the central nervous system.
Microglia: Phagocytic cells in the central nervous system.
Ependymal cells: Produce cerebrospinal fluid in the central nervous system.
Satellite cells: Supporting cells in the peripheral nervous system.
Schwann cells: Form the myelin sheath in the peripheral nervous system.

### Important Terms

Nucleus: A collection of nerve cells within the central nervous system.
Ganglion: A collection of nerve cells outside the central nervous system.
Synapse: The junction between a nerve cell and another neuron, muscle, or gland.
Pre-synaptic element: The end of the axon containing vesicles.
Synaptic cleft: The space between the pre-synaptic and post-synaptic elements.
Post-synaptic element: The part of the neuron or effector cell receiving the signal.
Types of synapses: Axo-dendritic, axo-somatic, axo-axonic, and neuromuscular.

### Classification of the Nervous System

The nervous system is divided into the central and peripheral nervous systems.

### The Central Nervous System

The central nervous system is comprised of the brain and spinal cord.

### The Brain

Anatomically: The brain consists of the cerebrum, cerebellum, and brainstem.
Cerebrum: Composed of two cerebral hemispheres and the diencephalon.
Diencephalon: Composed of the thalamus and hypothalamus.
Cerebellum: Responsible for equilibrium and balance.
Brainstem: Composed of the midbrain, pons, and medulla.
Embryologically: The brain develops from the forebrain, midbrain, and hindbrain.
Forebrain: Forms the cerebrum.
Midbrain: Forms the midbrain.
Hindbrain: Forms the pons, medulla, and cerebellum.

### Spinal Cord

The spinal cord is a long, tubular structure that extends from the medulla oblongata to the first lumbar vertebra (L1) in adults.
The length of the spinal cord is approximately 45 cm in males and 42 cm in females.
The spinal cord is composed of 31 segments: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.

### Meninges

The central nervous system is surrounded by three layers of connective tissue called meninges.
Pia mater: The innermost layer.
Arachnoid mater: The middle layer.
Dura mater: The outermost layer.

### Cerebrospinal Fluid

Cerebrospinal fluid (CSF) is found in the ventricles of the brain.
Lateral ventricles: Located within the cerebral hemispheres.
Third ventricle: Located within the diencephalon.
Fourth ventricle: Located within the hindbrain.

### Peripheral Nervous System

The peripheral nervous system is composed of the cranial nerves and spinal nerves.

### Cranial Nerves

There are 12 pairs of cranial nerves.
Name:
- Olfactory
- Optic
- Occulomotor
- Trochlear
- Trigeminal
- Abducens
- Facial
- Vestibulocochlear
- Glossopharyngeal
- Vagus
- Accessory
- Hypoglossal
Origin:
- Nose
- Retina
- Midbrain
- Midbrain
- Pons
- Pons
- Pons
- Medulla
- Medulla
- Medulla
- Medulla
- Medulla
Function:
- Smell
- Vision
- Eye movement
- Eye movement
- Face sensation
- Eye movement
- Face muscles
- Hearing and balance
- Tongue and pharynx
- Viscera, larynx
- Larynx
- Tongue muscles
Exception: The olfactory nerve originates from the nose and the optic nerve originates from the eye.

### Spinal Nerves

There are 31 pairs of spinal nerves.
Spinal nerves are formed by the union of dorsal and ventral roots.
Dorsal root: Composed of the central processes of the dorsal root ganglion.
Ventral root: Composed of axons from the anterior horn cells (AHCs), which innervate skeletal muscles, and axons from the lateral horn cells (LHCs) which innervate smooth muscles.

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Description

Test your knowledge on the branches of the nervous system including the divisions of the Central and Peripheral Nervous Systems. This quiz also covers the Autonomic Nervous System and its functions. Understand the roles of the sympathetic and parasympathetic systems in regulating bodily functions.