Practical 4 - nervous system

What is the CNS?

Central nervous system

What is the PNS?

Peripheral nervous system

What does the CNS consist of?

Brain and spinal cord

What does the PNS consist of?

Spinal nerves and cranial nerves (12 pairs)

What is the cerebrum made up of?

Frontal lobes
Parietal lobes
Temporal lobes
Occipital lobes

What is a cerebral hemisphere?

A side of the cerebrum

What is a gyrus?

A ridge in the cerebrum

What is a sulcus?

A groove in the cerebrum

What is the function of the corpus callosum?

It conveys messages between cerebral hemispheres

What is the function of the cerebellum?

Fine control of movement, balance and coordination

What is the brainstem made up of?

Midbrain, pons and medulla oblongata

What is the function of the brainstem?

It contains centres vital for life

Which cranial nerves arise from the brainstem?

III to XII

What is CSF?

Cerebrospinal fluid

What is the function of CSF?

It circulates through the CNS to remove metabolic waste from the interstitial fluids of nervous tissues and return them to the bloodstream

Where does CSF circulate?

In the ventricles

Where is CSF produced?

In specialized ependymal cells by the choroid plexus

What is the function of the choroid plexus?

To produce CSF

What are ventricles?

Open spaces where CSF circulates and where it is produced by choroid plexi

What does CSF do after circulating through the ventricles?

It emerges through arachnoid granulations into the subarachnoid space

What is the name of the first two ventricles?

Lateral ventricles

Where are the lateral ventricles?

Deep within the cerebrum

How are the lateral ventricles connected to the 3rd ventricle?

By the interventricular foramen

What is another name for the interventricular foramen?

Foramen of Monro

How are the 3rd and 4th ventricles connected?

By the cerebral aqueduct that passes through the midbrain

What does the cerebral aqueduct pass through?

The midbrain

What is another name for the cerebral aqueduct?

Aqueduct of Sylvius

What is the 4th ventricle?

The space between the cerebellum and the pons/upper medulla

What is the outer surface of the CNS covered by?

Meninges

What are the meninges from superficial to deep?

Dura mater
Arachnoid mater
Pia mater

Describe dura mater:

Thick fibrous layer and strong protective sheath over the entire brain and spinal cord
Anchored to the inner surface of the cranium and vertebral cavity
2 layers in the brain (endosteal and meningeal)
1 layer in the spinal cord

What is the dura mater?

A thick fibrous layer and strong protective sheath over the entire brain and spinal cord

What is the dura mater anchored to?

The inner surface of the cranium and vertebral cavity

How many layers of dura mater are there in the cranium?

2

How many layers of dura mater are there in the spinal cord?

1

What is the difference between dura mater in the cranium and in the spinal cord?

Consists of 2 layers in the brain and only one in the spinal cord

What are the names of the dura mater layers in the brain?

Endosteal and meningeal layers

Describe arachnoid mater:

Membrane of thin fibrous tissue that forms a loose sac around the CNS between the dura and pia mater
In the spinal cord it is held to the dura by CSF (in life)

What is the arachnoid mater?

A membrane of thin fibrous tissue that forms a loose sac around the CNS between the dura and pia mater

How is arachnoid held to the dura in the spinal cord in life?

By CSF

Describe pia mater:

Directly adjacent to the CNS
Thin fibrous membrane that follows the convolutions of gyri/sulci in the cerebral cortex and fits into other grooves and indentations

What is pia mater directly adjacent to?

The CNS

What are the spaces in the cranium?

Extra/epidural space
Subdural space
Subarachnoid space

What are the spaces in the spinal cord?

Extra/epidural space
Subdural space
Subarachnoid space

Describe the epidural space in the cranium:

Potential space as the dura is adhered to the skull

Describe the subdural space in the cranium:

Potential space between the dura and arachnoid that contains nothing

Describe the subarachnoid space in the cranium:

Space between the arachnoid and pia that contains CSF

What kind of space is the epidural space in the cranium?

Potential space

What kind of space is the subdural space in the cranium?

Potential space

What kind of space is the subarachnoid space in the cranium?

Anatomical space

What does the subdural space in the cranium contain?

Nothing

Why is the epidural space in the cranium and potential space?

Because it is adhered to the skull

What does the subarachnoid space in the cranium contain?

CSF

What is the subdural space between?

Dura and arachnoid

What is the subarachnoid space between?

Arachnoid and pia

Describe the epidural space in the spinal cord:

Anatomical space between dura and ligamentum flavum
Contains lymphatics, spinal nerve roots, loose connective tissue, fatty tissue, small arteries and networks of venous plexi
Needle inserted here to reduce inflammation/pain from nerve root compressionn

Describe the subdural space in the spinal cord:

Potential space between dura and arachnoid
Becomes an anatomical space in death

Describe the subarachnoid space in the spinal cord:

Anatomical space containing CSF between the arachnoid and pia
Insert needle here to examine CSF

What kind of space is the epidural space in the spinal cord?

Anatomical space

What kind of space is the subdural space in the spinal cord?

Potential space

What kind of space is the subarachnoid space in the spinal cord?

Anatomical space

What is the epidural space in the spinal cord between?

Dura and ligamentum flavum

What does the epidural space in the spinal cord contain?

Lymphatics
Spinal nerve roots
Loose connective tissue
Fatty tissue
Small arteries
Network of venous plexi

Why would you insert a needle into the epidural space in the spinal cord?

To reduce inflammation and pain from nerve root compression

What is the difference between the subdural space in life and in death?

It is a potential space in life and an anatomical space in death

What does the subarachnoid space contain?

CSF

Why would you insert a needle into the subarachnoid space in the spinal cord?

To examine CSF

What space would you insert a needle into to examine CSF?

Subarachnoid space in the spinal cord

What space would you insert a needle into to reduce inflammation and pain from nerve root compression?

Epidural space in the spinal cord

What is the difference between the epidural space in the cranium and in the spinal cord?

It is a potential space in the cranium and an anatomical space in the spinal cord

Why is the epidural space a potential space in the cranium but an anatomical space in the spinal cord?

In the cranium the dura is adhered to the skull so there can be no space but in the spinal cord there is no bone to adhere to

Where does the spinal cord start?

At the foramen magnum, after the medulla oblongata

What does the spinal cord pass through?

The vertebral canal

What is the spinal cord a continuation of?

The medulla oblongata/brainstem

Where does the spinal cord end in adults?

L1/L2

What forms because the vertebral column continues to grow after L1/L2?

The cauda equina

What is the cauda equina?

A set of hanging fibres outside the spinal cord

Why does the cauda equina form?

Because the spinal cord ends at L1/L2 but the vertebral column keeps growing

What kind of joints are intervertebral discs?

Secondary cartilaginous (symphysis)

Describe the structure of intervertebral discs:

Nucleus pulposus in the centre, surrounded by the annulus fibrosus

What is more central, nucleus pulposus or annulus fibrosus?

Nucleus pulposus

What do erector spinae muscles lie posterior to?

Transverse processes

What do erector spinae muscles extend?

The spinal column

What do spinal nerves exit via?

Intervertebral foramina

What passes through intervertebral foramina?

Spinal nerves

What is the nervous system divided into?

Autonomic and somatic

What is the ANS?

Autonomic nervous system

What is the SNS?

Somatic nervous system

What is the ANS made up of?

Motor/visceral efferents (sympathetic and parasympathetic)
Sensory/visceral afferents

What is the SNS made up of?

Motor/somatic efferents
Sensory/somatic afferents

What is the difference between sympathetic and parasympathetic neurone pathways?

The sympathetic pathway has a much longer postganglionic fibre

What is a myotome?

A group of muscles innervated by a single spinal nerve root

What is a dermatome?

A strip of skin innervated by a single spinal nerve root

What is the name for a strip of skin innervated by a single spinal nerve root?

Dermatome

What is the name for a group of muscles innervated by a single spinal nerve root?

Myotome

What is the dermatome for the nipples?

T4

What is the dermatome for the umbilicus?

T10

What is the dermatome for the thumb?

C6

What is the dermatome for the front of the knee?

L3

What is the dermatome for referred diaphragmatic pain?

C3/C4