Gross Organisation and Anatomy of Nervous System

Question 1

What are the gross structural features of the nervous system?

Answer 1

Brain
Spinal Cord
Nerves
- Cranial (12 Pairs)
- Spinal (31 Pairs)
Cavities
Blood vessels
Membranes encasing soft tissues
Bones
- Cranium/Skull
- Vertebral column

Question 2

How can you classify the nervous system?

Answer 2

Central nervous system

• Covered in meninges
• Complex
• Adaptable
• (Brain + Spinal Cord)

Peripheral nervous system

• Covered in endoneurium, perineurium and epineurium
• Less sophisticated in functional capacity
• Dependant on CNS

Question 3

Why is it important to distinguish between CNS and PNS?

Answer 3

Because diseases can affect the different systems, so it is important to know the origin of the disease.

Question 4

Name some diseases of the CNS

Answer 4

Raised intracranial pressure
Multiple Sclerosis
Affective disorders
Alzheimer's
Parkinson's

Question 5

Name some characteristics of the CNS in relation to disease and damage.

Answer 5

No capacity to regenerate (currently)
Plasticity allows for some limited re-organisation
Susceptibility to advancing age

Question 6

Name some diseases of the PNS and a characteristic of the PNS related to disease.

Answer 6

Nerve compression syndromes
Demyelinating polyneuropathies

Capacity to regenerate after injury

Question 7

What is the clinical importance of tumours of the nervous system?

Answer 7

All PNS tumours are benign

Tumours of neurones in CNS are not malignant
Malignant tumours are a feature of Glia only.

Question 8

What are the different cell types of the nervous system?

Answer 8

Neurones (10%

Neuroglia (or glia) (90%)

Question 9

What is the basic structure of a neurone?

Answer 9

Some have dendrites that connect to the
Cell body which has an
Axon coming off of it which ends in an
Axon terminal

Question 10

Describe gross structure of the brain.

Answer 10

Cerebral hemispheres (large tubey stuff)
Thalamic masses
Brainstem
- Midbrain (top part)
- Pons (bulb part/mid part)
- Medulla (bottom part)
Cerebellum (wrinkly part at the back)
Cavities - ventricles
- Lateral (first two, big spaces in centre / C-shaped)
- 3rd ventricle (in-between the lateral, bit lower)
- 4th ventricle (space behind brainstem, in front of 
  cerebellum)

Question 11

What is the significance of having two halves to a brain?

Answer 11

There is lateralisation of function with respect to some modalities

Some modalities are represented bilaterally with one side more dominant
- Speech, handedness, attention

The implications are that strokes can have different outcomes depending on the side of the brain it affects

Question 12

What are the lobes of the cerebral cortex?

Answer 12

Many lobes
4 major lobes: (from front to back)

Frontal lobe
Parietal (superior to temporal)
Temporal (inferior to parietal)
Occipital

Question 13

What is the gross structure of the spinal cord?

Answer 13

It is a continuation of the medulla
Cylindrical (approx.) in shape
Somewhat flattened from front to back
Gross shape changes from rostral to caudal
Shows two enlargements at cervical and lumbar levels
Ends in taper - The Conus Medullaris
- Filum terminale and Denticulate Ligaments
It has a central cavity throughout its length

Question 14

Describe the appearance of the adult brain.

Answer 14

Shows mostly the cerebral cortex:
Highly convoluted
Convolutions consist of:
- Grooves or depressions known as Sulci
- Major sulci are known as Fissures
-Ridges or elevations known as Gyri

Large Sulci are invariable between individuals and are used as important landmarks in brain mapping for surgery

Can also see cerebellum at back
and some brainstem

Question 15

What divides the cerebral cortex into two?

Answer 15

Longitudinal fissures + Flax cerebri (Dura mater)

Hemispheres are normally interconnected by the corpus callosum and Commissures (anterior and posterior)

Question 16

What is meant by the vesicles of the brain?

Answer 16

Segments of the brain more easily seen from medial aspect.
They are visible from embryonic stages
Initially three are seen
- 3 Primary vesicles
2 additional others appear later
- 5 secondary vesicles

Question 17

Name the vesicles of the brain.

Answer 17

Forebrain
- Telencephalon (cerebrum)
- Diencephalon (centre of brain with the big space)
- containing the epithalamus, thalamus, hypothalamus,
and ventral thalamus and the third ventricle.
Midbrain
- Mesencephalon
Hindbrain
- Pons
- Medulla

Question 18

What are the meninges of the brain?

Answer 18

They are membranous envelopes that completely cover the brain
They consist of three connective tissue layers:
- Dura mater (2 layers)
- Periosteal layer of dura mater
- Meningeal layer of dura mater
- Arachnoid mater
- Pia mater

They are continuous with the spinal cord
(dura mater is a single layer in the spinal chord)

Question 19

What are the functions of the meninges of the brain?

Answer 19

They support and mechanically stabilise contents of the cranium

They act as “seatbelts” of the cranium

They organise (or divide) the cranial cavity into anatomical compartments

Question 20

What are the anatomical spaces associated with the meninges?

Answer 20

(inner layer of cranium)
Extradural space
(dura mater)
Subdural space
(arachnoid mater)
Sub-arachnoid space
(pia mater)

Question 21

What is the importance of the sub-arachnoid space?

Answer 21

Blood vessels are found within the subarachnoid space
- Arterial - site for intercranial bleeds

It is filled with cerebrospinal fluid (CSF)

Question 22

What are some functions of CSF?

Answer 22

Bathes the brain
Cushions the brain against mechanical agitation
It is a reservoir for metabolic substrate for the brain
It dissolves and carries away products of metabolism from the brain

Question 23

What is the significance of the brain and it’s blood supply?

Answer 23

The brain makes up 2% of body weight but receives 15% of cardiac output

Vasculature is intricate and substantial (400 miles)

Vasculature has ability to auto-regulate perfusion of the brain tissue

There is a blood brain barrier between the blood supply and the cells of the brain