Session 1 - Lecture 1: Introduction

Question 1

Name the main components of the CNS and PNS.

Answer 1

CNS = Cerebral hemispheres, brainstem, cerebellum and spinal cord.
PNS = dorsal and ventral roots, spinal nerves and peripheral nerves.

Question 2

What category does the cauda equina fall into in terms of CNS/PNS and why?

Answer 2

PNS as they contain ventral and dorsal roots even though they are found within the vertebral canal.

Question 3

Describe the basics of grey matter.

Answer 3

Composed of cell bodies and dendrites, highly vascular. Also contain axons allowing it to communicate with white matter. PNS equivalent = ganglion.

Question 4

Describe the basics of white matter.

Answer 4

Composed of axons with their supporting cells, the colour is due to the presence of fatty myelin. PNS equivalent = peripheral nerve.

Question 5

Describe the basics of the spinal cord.

Answer 5

31 segments each supplying a given dermatome and myotome on each side.
Central core of grey matter and outer shell of white matter.
Each segment connects with a spinal (mixed) nerve through dorsal (sensory) and ventral (motor) roots.

Question 6

Why does the cauda equina form?

Answer 6

The vertebral column grows quicker than the spinal cord. The top end of these nerves stay attached to the spinal cord while the lower end of the nerves exit the spinal column at its proper level.

Question 7

Describe the different sections of white matter within the spinal cord and give examples of each.

Answer 7

Funiculus = a segment of white matter containing multiple distinct tracts, impulses travel in multiple directions e.g. dorsal, ventral and lateral funiculus. 
Tract = anatomically and functionally defined white matter pathway connecting two distinct regions of grey matter, impulses travel in one direction e.g. ventral corticospinal tract.
Fasiculus = subdivision of tract supplying a specific region of the body e.g. fasiculus gracilis and fasiculus cuneatus.

Question 8

Describe the structure of grey matter within the spinal cord.

Answer 8

Grey matter is organised into cell columns which are named Rexed’s laminae (I-X). Motor neurones supplying a given muscle arise from multiple segments and form a distinct population of neurones in the CNS (a nucleus).
Note: motor neurones for skeletal muscle reside in the ventral horn.

Question 9

In terms of the CNS, what is a nucleus?

Answer 9

Found within the grey matter, a collection of functionally related cell bodies.

Question 10

In terms of the CNS, what is a cortex?

Answer 10

Found within the grey matter, a folded sheet of cell bodies found on the surface of a brain structure, typically 1-5mm thick).

Question 11

In terms of the CNS, what is fibre?

Answer 11

Found within the white matter, the term relates to an axon in association with its supporting cells.

Question 12

Name the three main types of fibres found within the CNS white matter and describe their general function.

Answer 12

Association/U fibres = connect cortical regions within the same hemispheres.
Commissural fibres = connect the left and right hemispheres or cord halves.
Projection fibres = connect the cerebral hemispheres with the cord/brainstem and vice versa.

Question 13

Describe the general functions of the midbrain/mesencephalon.

Answer 13

Eye movements and reflex responses to sound and vision.

Question 14

Describe the general functions of the pons.

Answer 14

Involved in feeding and sleep.

Question 15

Describe the general functions of the medulla.

Answer 15

Cardiovascular and respiratory centres, contain a major motor pathway (medullary pyramids).

Question 16

Where is the central sulcus found and what is its significance?

Answer 16

Sitting roughly in the middle of the coronal plane, key landmark separating frontal and parietal lobes.

Question 17

What is contained within the precentral gyrus?

Answer 17

Contains the primary motor cortex.

Question 18

What is contained within the postcentral gyrus?

Answer 18

Contains the primary sensory cortex.

Question 19

What is the significance of the lateral/Sylvian fissure?

Answer 19

Separates the temporal lobe from the frontal/parietal lobes.

Question 20

What is the significance of the parietal-occipital sulcus?

Answer 20

Separates the parietal lobe from the occipital lobe.

Question 21

What is the significance of the calcarine sulcus?

Answer 21

The primary visual cortex surrounds this.

Question 22

Describe the key features of the inferior brain.

Answer 22

Optic chasm = site where fibres of 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.
Parahippocampal gyrus = key cortical region for memory encoding.

Question 23

Describe the key features of the midline brain.

Answer 23

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 hippocampus.
Tectum = dorsal part of the midbrain involved in involuntary responses to auditory and visual stimuli.
Cerebellar tonsil = part of cerebellum that can herniate and compress medulla.

Question 24

What do the brain ventricles develop from and what is their function?

Answer 24

The brain itself is hollow, the cavities that form as a result are known as the brain ventricles. They contain choroid plexus which makes a total of 600-700ml of CSF per day.

Question 25

Where does the CSF circulate?

Answer 25

Through the ventricular system and the subarachnoid space before being reabsorbed at the arachnoid granulations and some other sites.
Lateral ventricles –> interventricular foramen –> third ventricles –> aqueduct of midbrain –> fourth ventricle –> central canal –> subarachnoid space.

Question 26

Name the three apertures by which the CSF leaves the fourth ventricles to go to the subarachnoid space?

Answer 26

Foramen of Luschka, foramen of Magendie (both lateral apertures) and the median aperture of Magendie.