GL1b - Basic Concepts of the Nervous System

Brain and Spinal Cord

2 components of the CNS

12 pairs

How many pairs of cranial nerves are there?

31 pairs

How many pairs of spinal nerves are there?

Sensory Division

This part of the PNS brings information towards the CNS for processing

Somatic Sensory

This receptor provides position, touch, pressure, pain, and temperature sensations

Visceral Sensory

This receptor monitors internal organs

Special Sensory

This receptor provides sensations of special senses

Motor Division

This part of the PNS carries commands towards peripheral tissues and systems

Somatic Nervous System

This motor system controls skeletal muscle contraction

Autonomic Nervous System

This motor system provides involuntary regulation to visceral organs

Neuroglia

This is the umbrella term for the non-excitable supporting cells that surround the neurons

Astrocytes

This is the most abundant neuroglia that signals to increase blood flow and NT uptake as well as control the ionic environment of the CNS

Microglial Cells

These are considered the phagocytes of the CNS

Ependymal Cells

These act as a semi-permeable barrier between the CSF in ventricles and surrounding tissue fluids

Oligodendrocytes

They provide myelination in the CNS

Satellite cell

These cells surround the neruon soma within the ganglia

Schwann cells

They provide myelination in the PNS

Neurons

These are the excitable nerve cells that transmit signals

Dendrite

This part of the neuron carries signal towards the soma

Axon

This part of the neuron carries signals away from the soma

Axon hillock

This connects the soma to the axon and is where AP is generated

Sensory neurons

These neurons carry afferent impulses to the CNS

Motor Neurons

These neuron carry efferent impulses to effector cells

Interneurons

These neurons convey impulses from the sensory to the motor neutrons

Nucleus

This is a collection of cell bodies in the CNS

Ganglia

This is a collection of cell bodies in the PNS

Multipolar

This structural classification of neurons has many dendrites and only 1 axon

CNS

Multipolar neurons are a major type of neuron in what part of the nervous system

Bipolar

This structural classification of neurons has one dendrite and one axon

Special sensory organs (Olfactory mucosa, Eyes, Ears)

Bipolar neurons are mainly found where?

Unipolar (Pseudounipolar)

This structural classification of neurons consists of a central and peripheral process which form the axon

PNS (All sensory neurons)

Pseudounipolar neurons are usually found in which part of the NS

Dorsal root ganglia of spinal cord and sensory ganglia of cranial nerves

Pseudounipolar neurons are usually found in which ganglia

Gray Matter

This gives the brain its grayish dull color

Nerve cell body, Dendrites, neurons, neuroglia, and synapses

5 components of gray matter

Myelination

The appearance of white matter is caused by what process?

1 > 2

QC: Usually found externally (1) White (2) Gray Matter

Cerebrum and cerebellum

2 regions of the brain that contains an extra external gray matter or cortex

Dorsal (Posterior)

Which of the 2 gray horns of the spinal cord is sensory in nature?

Ventral (Anterior)

Which of the 2 gray horns of the spinal cord is motor in nature?

Intermediolateral horn (Lateral Horn)

This is the protrusion between the dorsal and ventral gray horns found in the thoracolumbar segments that functions as the first-order neuron of the ANS

T1-L2

Between which spinal nerves can the lateral horn be found in?

Dura Mater

This is the thick, outermost meningeal layer rich in sensory fibers

Periosteal Dura mater

This layer of the dura mater is connected to the skull

Meningeal Layer

This layer of the dura mater is located more internally

Arachnoid mater

This is the fine, weblike avascular membrane found beneath the dura mater

Pia mater

This meningeal layer intimately envelops the brain and spinal cord and encloses the CSF

Epidural Space

This space separates the periosteal dura mater and the meningeal layer of the dura mater

Subdural space

This space separates the dura mater and the arachnoid mater

Subarachnoid space

This space separates the arachnoid mater and pia mater which contains the CSF, fibrous trabeculae, and main blood vessels

Dura mater of brain has 2 layers while spinal cord has 1

Main difference between the dura mater of the brain and spinal cord

Bony wall of vertebral canal

Since the dura mater of the spinal cord only has 1 layer, what does the epidural space separate the dura mater from?

Denticulate ligament

This structure passes through the arachnoid and attaches to the dura mater of the spinal cord

L1-L2

What level does the spinal cord terminate at?

L3-L4

What level are lumbar punctures usually done at?

S2

What level does the arachnoid mater, dura mater, and subarachnoid space end?

Coccyx

What level does the pia mater end?

Filum terminalis

This is the structure formed by the pia mater as it extends downwards that pierces the arachnoid and dural sacs to attach to the coccyx

Neurolemma

This is the outermost layer of the schwann cell that acts as a covering for the axon

Fascicles

These are formed when groups of axons bundle together into groups

vasa nervorum

This is the umbrella term for the blood vessels supplying the nerve

Endoneurium

This connective tissue encloses a singular axon

Perineurium

This connective tissue encloses a singular fascicle

Epineurium

This connective tissue encloses a bunch of fascicles

8

How many pairs of cervical spinal nerves are there?

12

How many pairs of thoracic spinal nerves are there?

5

How many pairs of lumbar spinal nerves are there?

5

How many pairs of sacral spinal nerves are there?

1

How many pairs of coccygeal spinal nerves are there?

False

T/F: There is an equal number of spinal nerves and vertebrae

7

Despite having 8 pairs of cervical spinal nerves, how many cervical vertebrae are there?

4

Despite having 1 pair of coccygeal spinal nerves, how many coccygeal vertebrae are there?

Superiorly

For most of the spinal nerves, they bear the same letter-numerical designation as the vertebrae found where?

Inferiorly

For cervical spinal nerves, they bear the same letter-numerical designation as the vertebrae found where?

C4-C5

Between which vertebrae would C5 exit at?

T7-T8

Between which vertebrae would T7 exit at?

False

T/F: Most spinal nerves are either purely sensory/motor while some are mixed

1 > 2

QC: Size (1) Anterior Ramus (2) Posterior Ramus

Anterolateral muscles, skin, and body wall and Upper and Lower limbs

What region of the body does the anterior ramus supply?

Back skin and muscles

What region of the body does the posterior ramus supply?

Dermatomes

These are strips of skin supplied by sensory branches of a single spinal nerve

Uniform and Horizontal

Describe the dermatome pattern of the trunk region

Overlapping and less straighforward

Describe the dermatome pattern of the limbs

Brachial Plexus

Supply to the upper limbs is attributed to which portion of spinal nerves?

Lumbar nerves

Supply to the anterior lower limbs is attributed to which portion of spinal nerves?

Sacral Nerves

Supply to the posterior lower limbs is attributed to which portion of spinal nerves?

C1

Which is the only spinal nerve that is purely motor in nature?

C6

This spinal nerve is solely responsible for innervating the thumb

T4

This spinal nerve is solely responsible for innervating the nipple

T7

This spinal nerve is solely responsible for innervating the epigastric area

T10

This spinal nerve is solely responsible for innervating the umbilicus

T2-T12

These are the only spinal nerves not involved in any plexus

T

T/F: The presence of plexuses is responsible for muscles having innervations from multiple nerve roots

SCM

The cervical plexus can be found under what structure?

Posterior Triangle

The cervical plexus extends to which triangle of the neck

Skin of neck, back of head, and most of superior shoulder

The cervical plexus supplies sensory innervation to what areas?

Strap Muscles

The cervical plexus supplies motor innervation to what muscles

Phrenic nerve

This is the most important part of the cervical plexus as it is responsible for innervating the muscles of respiration

C5 and C6

Which part of the brachial plexus forms the upper trunk

C7

Which part of the brachial plexus forms the middle trunk