Neuro 6 - Organisation of the CNS

Question 1

How many paris of nerves emerge from the CNS?

Answer 1

31 pairs
Equal number of nuerves for each vertebra except extra nerve above C1 so 8 cervical nerves, 7 verterbrae
C1 is above C1 so C8 above T1 and under C7
T1 under T1
Thoracic - 12
Lumbar - 5

Question 2

How is the spinal cord protected, where does it lie?

Answer 2

Protected by vertebrae
Lies in vertebral canal
Series of holes alongside vertebrae –> intervertebral foramina –> where nerves come out

Question 3

What is the structure called cauda equina?

Answer 3

cauda is a “tail”

It is when the spinal cord is shorter than the vertebral column so the nerves emerge from it and form a nerve tail

Question 4

Where can CSF fluid be sampled?

Answer 4

L3/L4

or L4/L5

Question 5

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

Answer 5

Lumbar cistern ("tank")
Where you find the cauda equina

Question 6

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

Answer 6

Dorsal -> sensory (has dorsal ganglion) - in from dorsal route
Ventral -> motor - out from ventral route

Question 7

What is the difference between the white and grey matter?

Answer 7

White matter -> myelinated fibres - go up and down
Grey matter -> neuronal cell bodies, glial cells, unmyelinated fibres
Myelin is WHITE

Question 8

What are the functions of the spinal cord?

Answer 8

• connects PNS and ANS to the brain
• carries sensory signal to the brain
• carries motor signals to the muscles
• coordinates reflexes - information processed at the spinal cord level

Question 9

What structure connects the right and left hemispheres?

Answer 9

Corpus callosum

Question 10

What lies beneath the corpus callosum?

Answer 10

Diaencephalon ie. thalamus + hypothalamus

Question 11

What are the two parts of the diencephalon and what is their function?

Answer 11

Thalamus - relay station for information going between the cerebral cortex and other areas of the CNS. Somatic and special senses, emotional, consciousness
Hypothalamus - integration hub - important in coordinating homeostasis (hypothalamo-hypophysial axis)
Thalamus is above hypothalamus
–> know everything that is going on in body, however, to make sense of it needs cortex

Question 12

What are the two classifications of the brain?

Answer 12

—>Based on embryonic development:
It initially developed as the forebrain, midbrain and hindbrain.
The forebrain became the cerebral cortex and diencephalon
The midbrain remained as the midbrain (part in between diencephalon and pons)
The hindbrain became the pons, medulla and cerebellum

—>Other classification:
Brainstem -> Midbrain + pons + medulla
Cerebrum -> hemispheres + diencephalon
Cerebellum

Question 13

What composes the brainstem?

Answer 13

Midbrain
Pons
Medulla

All sensory and motor fibres that connect the cerebrum, cerebellum and spinal cord run through it
Continuation of spinal cord (medulla still has its structure but enlarged)

Question 14

What makes the pons recognisable?

Answer 14

It bulges anteriorly

Question 15

What is the function of the brainstem?

Answer 15

Control of many vital functions such as breathing, HR, BP, swallowing, balance, etc.
Defensive reflexes, sleep-wake cycles, alertness, consciousness

NOTE
Lesion of the brainstem can lead to locked-in syndrome
Midbrain includes substantia nigra which degenerates in Parkinson’s

Question 16

What composes the cerebral hemispheres?

Answer 16

Cortex + basal ganglia
It is on right and left lateral sides of diencephalon.
Looks like a funny structure

Question 17

What composes the basal ganglia?

Answer 17

Caudate 
Putamen
Globus pallidus
Subthalamic nucleus 
Substantia nigra 

Caudate + putamen = corpus striatum (because of ‘stripy’ connection)
Globus Pallidus + putamen = Lentiform nucleus

Question 18

What is the function of the basal ganglia?

Answer 18

Control of movement - “fine tuning” - facilitating voluntary movement, inhibiting unwanted or inappropriate movements

Question 19

What are the two types of cortex?

Answer 19

Primary Cortical Area (primary cortex) - main part
Association Cortex - where info of primary cortex is made sense of
Usually like primary motor cortex then motor association area

Question 20

What is gyri and sucli?

Answer 20

How the cortex is organised
Gyri - top of the invagination
Sulci - invagination

Question 21

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

Answer 21

They both have somatotopic arrangement - like a little man standing upside down

Question 22

What is the function of the association cortex?

Answer 22

The association cortex is involved in higher functions e.g. learning, perception, thinking

Question 23

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

Answer 23

Wenicke’s Area - understanding language

Broca’s Area – speech

Question 24

How many layers does the cortex have?

Answer 24

Usually 6

Question 25

What is the limbic system? what one structure is important?

Answer 25

Hippocampus - cortex rolled up on itself - memory, learning, alzheimer's Consists of amygdala, olfactory bulbs.. Function - motivation, instinctive behaviour, emotion, memory

Question 26

What is the role of the cerebellum?

Answer 26

Coordinates complex somatic motor patterns Adjust output of other somatic motor centers in brain and spinal cord --> fine tuning motor function

Question 27

What are the three types of fibres in the brain?

Answer 27

- Commisural (corpus callosum) - crosses - Association fibers - in between cortical areas, within hemisphere - Projection fibers - from the cortex down to spinal cord Corona radiata is a structure seen pf fibers that spread out of cortex from the base and form a sort of fan

Question 28

How many bones compose the cranium?

Answer 28

6 bones - frontal, sphenoid, temporal, parietal, occipital, ethmoid Holes for vessels Foramen magnum for spinal cord Lots of fossa like sella turcica

Question 29

What are the layers of the meninges?

Answer 29

Dura mater (periostal + meningeal) Arachnoid mater Pia mater between the brain and the bone = meninges Between arachnoid and pia CSF can circulate in sub arachnoid space

Question 30

Describe the ventricular system of the brain.

Answer 30

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 (looks like bird head). 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 31

Where is cerebrospinal fluid produced?

Answer 31

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

Question 32

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

Answer 32

CSF leaves the ventricles in the 4th ventricle, which has small holes in it

Question 33

How is CSF reabsorbed into the venous system?

Answer 33

CSF is reabsorbed into the venous system by arachnoid villi = membrane invagination of the arachnoid mater

Question 34

What separates the temporal lobe from the other lobes?

Answer 34

Lateral Sulcus

Question 35

What is the role of CSF?

Answer 35

Metabolic function - remove waste Cushioning Nutrition Immune cells Composition similar to plasma but much lower protein, lower glucose, lower Ca2+, higher Cl-

Question 36

Define hydrocephalus and explain treatment

Answer 36

= increase in CSF volume ``` Communicating hydrocephalus (all 4 ventricles affected) is caused by block in CSF absorption: Meningitis Head injury Congenital Sub-arachnoid haemorrhage ``` Non communicating hydrocephalus (not all affected) is caused by block in ventricular system: Aqueduct stenosis Ventricular tumour

Question 37

Compare the clinical presentation of epidural (extradural) and subdural haemorrhage

Answer 37

Epidural haemorrhage: Arterial bleeding Symptoms of headache, drowsiness, vomiting or seizure arise promptly after injury Subdural haemorrhage: Venous bleeding Symptoms delayed by days or weeks