Intro

Question 1

What are the basic components of the CNS

Answer 1

Cerebral hemispheres, brainstem, cerebellum, spinal cord. Not neccessarily within bone, e.g. cords equina

Question 2

What are the basic components of the pNs

Answer 2

Dorsal and ventral roots,spinal elves, peripheral nerves

Question 3

What is grey matter?

Answer 3

Composed of cell bodies, dendrites, and axon terminals. It is highly vascular which reflects its role in synaptic processing.
Grey matter contains axons to communicate with white matter.

Question 4

What is the grey matter in the CNS, and what is the pNS equivalent

Answer 4

The grey matter in the CNS is:
Cerebral cortex, nuclei, horns of the cord
The PNS equivalent of grey matter is a “ganglion” (collection of cell bodies), but beware the term basal ganglia, as they are in the CNS

Question 5

What is white matter

Answer 5

Composed of axons with their supporting cells (a fibre). White matter is white due to the presence of myelin. The pNs equivalent of white matter is a peripheral nerve

Question 6

Describe the segments of the cord and the nerve they are connected to

Answer 6

• The cord is composed of around 31 segments, each supplying a given dermatome and myotome on each side
• The cord has a central core of grey matter and an outer shell of white matter
• Each segment connects with a spinal (mixed) nerve through dorsal (sensory) and ventral (motor) roots
• Knowledge of dermatomal and myotomal supply allows localisation of lesions to a given cord segment(s)
Clinicalkey

Question 7

What is a funiculus

Answer 7

Funiculus (pl. funiculi): a segment of white matter containing multiple distinct tracts. Impulses travel in multiple directions - both afferent and efferent fibres

Question 8

What is a tract?

Answer 8

Tract: an anatomically and functionally defined white matter pathway connecting two distinct regions of grey matter. Impulses travel in one direction. Each tract has one function, e.g. sensory. They are within the funiculi.

Question 9

What is a fasiculus?

Answer 9

Fasciculus (pl. fasciculi): a subdivision of a tract supplying a distinct region of the body. Not all tracts have fasiculi.
There are 2 fasiculi in the dorsal colum - gracile and cuniate

Question 10

Describe the grey matte of teh cord

Answer 10

• Just as white matter is organised into tracts etc. grey matter in the cord is organised into cell columns
• The motor neurones supplying a given muscle arise from multiple segments and form a distinct population of neurones in the CNS – a nucleus

Question 11

What is a nucleus

Answer 11

A collectuion of bilaterally symmetrical functionally related cell bodies. Relay info up an down - cortical processing

Question 12

What is the cortex

Answer 12

A folded sheet of cel bodies found on the surface of the brain. Typically 1-5mm thick

Question 13

What is a fibre

Answer 13

A term related to an axon in association with its supporting cells. Used synonymously. There are association fibres, commissural fibres, projection fibres

Question 14

What is an association fibre

Answer 14

Connect cortical regions within the same hemishphere. Association fibres which connect 2 neighbouring gyri are called U fibres

Question 15

What are commissural fibres

Answer 15

Connect the let and right hemispheres or cord halves. E.g. ventral white commissure in cord, corpus callosum in brain

Question 16

What are projection fibres

Answer 16

Connect the cerebral hemispheres with the cord/brain stem and vice versa

Question 17

What are the general roles of the midbrain

Answer 17

Midbrain (mesencephalon)
• Eye movements and reflex responses
to sound and vision

Question 18

What are the general roles of the pons

Answer 18

Feeding and sleep

Question 19

What are the general roles of the medulla

Answer 19

• Cardiovascular and respiratory centres
• Contains a major motor pathway
(medullary pyramids

Question 20

What are the key gyri and Sulci

Answer 20

Central sulcus: Sitting in the coronal plane. Key landmark separating frontal and parietal lobes
Precentral gyrus: Contains primary motor cortex
Postcentral gyrus: Contains primary sensory cortex
Lateral/Sylvian fissure: Separates temporal from frontal/parietal lobes
Parieto-occipital sulcus: Separates parietal from occipital lobe
Calcarine sulcus: Primary visual cortex surrounds this

Question 21

What are the key features of the inferior aspect of the brain

Answer 21

Optic chiasm: A site where fibres in the visual system cross over
Uncus: Part of the temporal lobe that can herniate, compressing the midbrain. Important olfactory role Medullary pyramids: Location of descending motor fibres (each has around 1 million axons!) Parahippocampal gyrus: Key cortical region for memory encoding

Question 22

What are the key features of he midline of the brain

Answer 22

Corpus callosum: Fibres connecting the two cerebral hemispheres
Thalamus: Sensory relay station projecting to sensory cortex Cingulate gyrus: Cortical area important for emotion and memory
Hypothalamus: Essential centre for homeostasis
Fornix: Major output pathway from the hippocampus Tectum: Dorsal part of the midbrain involved in involuntary responses to auditory and visual stimuli
Cerebellar tonsil: Part of the cerebellum that can herniate and compress the medulla

Question 23

What are the ventricles

Answer 23

• Having developed from a hollow tube, the brain is itself hollow
• These cavities are known as the brain ventricles
• The ventricles each contain choroid plexus, which
makes a total of 600-700ml of CSF per day

Question 24

What are the functions of csf

Answer 24

• CSF has both metabolic and mechanical functions
o Contains glucose and may be even hormones
o Shock absorbs the brain and renders it effectively weightless
• CSF circulates through the ventricular system and subarachnoid space before being reabsorbed at the arachnoid granulations (and some other sites)
o Arachnoid granulations resemble little cauliflowers, projecting into the superior sagittal sinus. Here CSF crosses the wall of the granulation and enters venous blood

Question 25

Describe the lateral ventricles

Answer 25

A pair of lateral ventricles. The lateral ventricles sit deep within cerebral hemisheres - they have seperate parts sitting in different lobes of the brain:
• temporal horn sits in temporal lobe
• Frontal hon sit in frontal lobe
• Occipital horn in Occipital lobe
lateral ventricles are the largest ventricles, contains the most choroid plexus so make the most csf . Csf passes through the intraventricular foramen. This connects the 2 lateral ventricles together. Csf goes through here before it enters the 3rd ventricle

Question 26

Decribe the 3rd ventricles

Answer 26

3rd ventricle - thalamus within its walls. Thalamus squashes the 3rd ventricle flat. Also hypothalamic nuclei + struectes related to pineal gland. 3rd ventricle has its own choroid plexus so csf added. Then it drains into cerebral aqueduct (in the midbrain), then into 4th ventricle.

Question 27

Describe teh 4th ventricle

Answer 27

Cerebral aqueduct @ midbrain. 4th ventricle sits bellow the cerebellum. • The fourth ventricle sits beneath the cerebellum, and CSF can drain from it via the lateral (of
Luschka) and median (of Magendie) apertures
o These apertures are direct holes in the brain, permitting CSF to drain from the ventricular system into the subarachnoid space. There is negligible drainage via the
spinal cord central canal
• Once in the subarachnoid space, CSF percolates around the superficial surfaces of the brain
and spinal cord before being reabsorbed in the granulations. 4th ventricle is continuous with central canal f spinal cord, bu central canal is so narrow - there isnt a significant amount of csf that passes though it.

Question 28

Decsribe booking of he ventricular system

Answer 28

Blockage of the ventricular system
• Blockage of a part of the ventricular system will lead to upstream dilatation and potential damage to structures surrounding the dilated ventricles
• The cerebral aqueduct is a common site for such occlusions, maybe due to congenital stenosis or tumour
o Blockage of the aqueduct would cause dilatation of the lateral and third ventricles but with a normal fourth ventricle (downstream)