S1) Topography of the Nervous System

Question 1

What are the four basic components of the central nervous system?

Answer 1

• Cerebral hemispheres
• Brainstem
• Cerebellum
• Spinal cord

Question 2

What are the four basic components of the peripheral nervous system?

Answer 2

• Dorsal and ventral roots
• Spinal nerves
• Peripheral nerves
• Ganglia

Question 3

Distinguish between the composition of grey matter and white matter

Answer 3

• Grey matter is composed of cell bodies and dendrites (highly vascular)
• White matter is composed of axons (+ supporting cells)

Question 4

Why does grey matter contain axon terminals?

Answer 4

Grey matter contains axons to allow communication with white matter

Question 5

Why is white matter white?

Answer 5

White matter is white due to the presence of fatty myelin

Question 6

In the peripheral nervous system, identify the equivalent structures of the following:

• Grey matter
• White matter

Answer 6

• The PNS equivalent of grey matter is a ganglion
• The PNS equivalent of white matter is a peripheral nerve

Question 7

How many segments does the spinal cord consist of?

Answer 7

The spinal cord is composed of 31 segments

Question 8

Describe the structure of a spinal cord segment

Answer 8

• Central core of grey matter
• Outer shell of white matter

Each segment connects with a mixed spinal nerve through dorsal sensory roots and ventral motor roots

Question 9

Identify three components of white matter

Answer 9

• Funiculus
• Tract
• Fasciculus

Question 10

What is a funiculus?

Answer 10

• A funiculus is a segment of white matter containing multiple distinct tracts
• Impulses travel in multiple directions

Question 11

What is a tract?

Answer 11

• A tract is an anatomically and functionally defined white matter pathway connecting two distinct regions of grey matter
• Impulses travel in one direction

Question 12

What is a fasciculus?

Answer 12

A fasciculus is a subdivision of a tract supplying a distinct region of the body

Question 13

Identify the three different regions of grey matter

Answer 13

Question 14

What is a nucleus?

Answer 14

A nucleus is a collection of functionally related cell bodies (grey matter)

Question 15

What is a cortex?

Answer 15

A cortex is a folded sheet of cell bodies found on the surface of a brain structure (grey matter)

Question 16

What is a fibre?

Answer 16

A fibre is an axon in association with its supporting cells e.g. oligodendrocytes (synonymous with axon)

Question 17

What are the three types of fibres found in the nervous system?

Answer 17

• Association fibres
• Commissural fibres
• Projection fibres

Question 18

What do association fibres do?

Answer 18

Association fibres connect cortical regions within the same hemisphere

Question 19

What do commisural fibres do?

Answer 19

Commissural fibres connect left and right hemispheres or cord halves

Question 20

What do projection fibres do?

Answer 20

Projection fibres connect the cerebral hemispheres with the cord/brainstem and vice versa

Question 21

What are the three components of the brainstem?

Answer 21

Question 22

What is the function of the midbrain (mesencephalon)?

Answer 22

The midbrain regulates eye movements and reflex responses to sound and vision

Question 23

Which processes are regulated by the pons?

Answer 23

• Feeding
• Sleep

Question 24

Which key centres are found in the medulla?

Answer 24

• Cardiovascular and respiratory centres
• Major motor pathway (medullary pyramids)

Question 25

Where is the central sulcus found?

Answer 25

**Central sulcus** is a key landmark separating the frontal and parietal lobes (coronal plane)

Question 26

Which cortices are found in the following locations: - Precentral gyrus - Postcentral gyrus

Answer 26

- **Precentral gyrus:** contains primary motor cortex - **Postcentral gyrus:** contains primary sensory cortex

Question 27

Where is the lateral fissure found?

Answer 27

The **lateral fissure** is a key landmark separating the temporal lobe from the frontal/parietal lobes

Question 28

Where is the parieto-occipital sulcus found?

Answer 28

**Parieto-occipital sulcus** is a key landmark separating the parietal lobe from the occipital lobe

Question 29

Where is the calcarine sulcus found?

Answer 29

The **calcarine sulcus** is a key landmark surrounded by the primary visual cortex

Question 30

What is the optic chiasm?

Answer 30

The **optic chiasm** is a site where fibres in the visual system cross over

Question 31

What is the uncus?

Answer 31

- The **uncus** is a part of the temporal lobe that can herniate, compressing the midbrain - It has an important olfactory role

Question 32

What are the medullary pyramids?

Answer 32

The **medullary pyramids** are a location of descending motor fibres

Question 33

What is the parahippocampal gyrus?

Answer 33

The **parahippocampal gyrus** is a key cortical region for memory encoding

Question 34

What is the corpus callosum?

Answer 34

The **corpus callosum** consists of fibres connecting the two cerebral hemispheres

Question 35

What is the thalamus?

Answer 35

The **thalamus** is a sensory relay station projecting to the sensory cortex

Question 36

What is the cingulate gyrus?

Answer 36

The **cingulate gyrus** is a cortical area important for emotion and memory

Question 37

What is the hypothalamus?

Answer 37

The **hypothalamus** is an essential centre for homeostasis

Question 38

What is the fornix?

Answer 38

The **fornix** is a major output pathway from the hippocampus

Question 39

What is the tectum?

Answer 39

The **tectum** is the dorsal part of the midbrain involved in involuntary responses to auditory and visual stimuli

Question 40

What is the cerebellar tonsil?

Answer 40

The **cerebellar tonsil** is a part of the cerebellum that can herniate and compress the medulla

Question 41

Having developed from a hollow tube, the brain is itself hollow. What are the cavities in the brain called?

Answer 41

The cavities in the brain are called **ventricles**

Question 42

Describe the layout of the ventricular system

Answer 42

Question 43

What is found inside the brain ventricles?

Answer 43

The ventricles each contain **choroid plexus**, which makes a total of 600-700ml of **cerebrospinal fluid** per day

Question 44

What types of functions does CSF have?

Answer 44

CSF has both **metabolic** and **mechanical** functions

Question 45

Describe the circulation of cerebrospinal fluid

Answer 45

CSF circulates through the **ventricular system** and **subarachnoid space** before being reabsorbed at the **arachnoid granulations** in the superior sagittal sinus (and some other sites)