Organisation of the Central Nervous System

Question 1

Terminology

Answer 1

Brain:
Dorsal- superior of the brain
Ventral- inferior
Spinal cord:
Dorsal- posterior
ventral- anterior

Rostral- towards the frontal lobe
chordal- towards the spinal cord

Question 2

Describe the structure of the spinal cord

Answer 2

31 segments and each one corresponds to a vertebra.
30 vertebra and 31 nerves.
spinal cord shorter than the vertebral column.
-spinal nerves all come out from just below the vertebra of the same number.
cervical- 7
thoracic- 12
lumbar -5

there is an extra nerve above C1/

Question 3

To obtain CSF, where should it be done?

Answer 3

L3 and L4
or
L4 and L5

Question 4

What is the difference between the dorsal horns and the ventral horns?

Answer 4

The dorsal horns are SENSORY - the impulses come towards the CNS
The ventral horns are MOTOR - the impulses go away from the CNS

Question 5

what does the brainstem consist of and what are the roles of the brainstem

Answer 5

Midbrain
Pons
Medulla oblongata
medulla merges with the top of the spinal cord as it goes through the hole in the base of the skull.
-Lots of ascending and descending pathways.
Ascending: takes sensory information up to the brain
descending: comes down from the motor cortical areas down the brain stem and stimulate neurons in the spinal cord which then produce movement.
there are yellow things called cranial nerves- we have 12 of which 10 is in the brainstem. These provide sensory and motor innervation for the head region.
pons- bridge connected to the cerebellum

Question 6

What are the two parts of the diencephalon and what does it do?

Answer 6

contains thalamus and hypothalamus.
Thalamus one on each side and in the middle is the 3rd ventricle.

Thalamus - relay station for information going between the cerebral cortex and other areas of the CNS
Hypothalamus - important in coordinating homeostasis (hypothalamo-hypophysial axis)

Question 7

what does the cerebral hemisphere consist of and what is its role

Answer 7

-Deep inside the cerebral cortex you find lots of nuclei.
-One of the main nuclei is the basal ganglion
-Basal ganglia: group of nuclei which
Regulates voluntary movement

Question 8

What structure connects the right and left hemispheres?

Answer 8

Corpus Callosum

Question 9

3 layer of meninges and where does CSF circulate

Answer 9

Dura mater: has 2 layers
Arachnoid mater
Pia mater.

Between the arachnoid and the pia mater you have the sub-arachnoid space where CSF can circulate.

Question 10

What is the role of the cerebellum?

Answer 10

Fine tuning motor function

Question 11

What makes the pons recognisable?

Answer 11

It bulges anteriorly

Question 12

How did the brain initially develop and what do the three parts of this initial brain differentiate into?

Answer 12

It initially developed as the forebrain, midbrain and hindbrain.
The forebrain became the cerebral cortex and diencephalon
The midbrain remained as the midbrain
The hindbrain became the pons, medulla and cerebellum

Question 13

What are the two types of cortical areas?

Answer 13

Primary Cortical Area

Association Cortex

Question 14

how does the primary motor cortex work

Answer 14

The cells of this cortex send axons down through the descending pathways to stimulate motor neurons in the spinal cord- the spinal motor neurons then stimulate the muscle via the PNS.

Question 15

Describe the arrangement of the primary motor cortex and the primary somatosensory cortex.

Answer 15

They both have somatotopic arrangement - like a little man standing upside down.
Area at the bottom controls the movement of the head, middle is movement of the arms and top is movement of the legs

Question 16

where is the primary somatosensory cortex located and what is its function

Answer 16

-adjacent to the primary motor cortex receives general sensory information coming from the body

Question 17

what is the primary auditory cortex and primary visual cortex responsible for

Answer 17

Primary auditory cortex: first to receive information from the ears
Primary visual cortex; first to receive information from the retina

Question 18

What is the function of the association cortex?

Answer 18

The association cortex is involved in higher functions e.g. learning, perception, thinking so the rest of the areas that are NOT primary cortex

Question 19

What is the role of Wernicke’s Area and Broca’s Area?

Answer 19

Wernicke’s Area - understanding language

Broca’s Area – speech

Question 20

Describe the ventricular system of the brain.

Answer 20

There are two large C shaped ventricles called lateral ventricles. There is one lateral ventricle for each cerebral hemisphere.
The lateral ventricles narrow and form the 3rd ventricle, which is in the diencephalon
The 3rd ventricle narrows to form the cerebral aqueduct, which passes down through the midbrain and becomes a tent-shaped structure called the 4th ventricle.
The 4th ventricle is behind the pons and medulla and in front of the cerebellum.
The 4th ventricle then narrows to form the central canal, which runs down the spinal cord.

Question 21

Where is cerebrospinal fluid produced?

Answer 21

By the choroid plexus, which is a special type of ependymal cell found in the ventricles.

Question 22

Where does CSF leave the ventricles and enter the subarachnoid space?

Answer 22

CSF leaves the ventricles in the 4th ventricle, which has small holes in it so it can exit and spread across the brain.
CSF circulates in the sub-arachnoid space between the meninges.

Question 23

How is CSF reabsorbed into the venous system?

Answer 23

CSF is reabsorbed into the venous system by arachnoid villi.

Question 24

what are arachnoid villi?

Answer 24

there are venous sinuses over the surface of the brain. There are some out-pockets of the arachnoid membrane which pushes through the walls of the venous sinus and allows reabsorption of CSF- these are arachnoid Villi

Question 25

What causes hydrocephalus

Answer 25

blockage causing a build up of CSF in the brain

Question 26

what is the spinal cord and describe the arrangement.

Answer 26

Column of neural tissue which is segmental.

• each segment has a pair of spinal nerves attached to it
• core consists of grey matter which has cell bodies, there is wrapping of white matter containing axons
• grey matter is divided into sensory and motor areas

Question 27

What are the hole in the vertebral column that spinal nerves pass through called and what do they have coming out from them?

Answer 27

Intervertebral Foramina.

they have spinal nerves coming out from them

Question 28

What is the significant difference between the length of the spinal cord and the vertebral column?

Answer 28

The spinal cord is much shorter than the vertebral column

The spinal cord ends around L1/L2

Question 29

What is the name of the area inside the vertebral canal beneath the point at which the spinal cord ends?

Answer 29

Lumbar Cistern

Question 30

What is the name of the structure found in this area?

Answer 30

Cauda Equina

Question 31

Where is the grey matter and white matter around the body

Answer 31

Spinal cord: grey is in the middle, white at periphery.
Brain stem and diencephalon: similar to spinal cord, but grey is more scattered in different structures/nuclei rather than one core.
Hemisphere and in the cerebellum: deeper white structures with grey structures e.g. basal ganglia.
and grey cortex added on the surface.