Neuroanatomy 1 (Dr Wicklein)

Question 1

What are the different components of the nervous system (NS) ?

Answer 1

The Central Nervous System (CNS) : brain and spinal chord

The Peripheral Nervous System (PNS) : spinal nerves, cranial nerves, somatic NS and autonomic/visceral NS

Question 2

What does the autonomic NS comprise ?

Answer 2

The sympathetic NS, the parasympathetic NS and the enteric NS.

Question 3

What is the diameter of a large neuron cell body ?

Answer 3

70-100μ

Question 4

How big is the average synaptic cleft ?

Answer 4

20-40nm

Question 5

How heavy is the average human brain ?

What about the surface area and its height/length/width ?

Answer 5

Weight: 1.5 kg
Surface area: 1200 cm2
Width: 14 cm
Height: 16.7 cm
Length: 9.3 cm

Question 6

How many neurons are there is the human brain ?

How many connections and synapses ?

Answer 6

100 billions neurons
7000 synapses each
7E14 synapses in total

Question 7

What is he brains metabolic consumption ?

Answer 7

20% of the resting metabolic rate.

Question 8

What is the diameter of a synaptic vesicle ?

Answer 8

About 40nm.

Question 9

What are the main terms of direction used in neuroanatomy ?

Answer 9

Rostral/ caudal = head/tail
Superior/inferior = up/down
Dorsal/ventral = back/front
Medial/lateral = middle/side
Proximal/distal = close/far
Ipsilateral/contralateral = same side/opposite side

Question 10

What is neuropil ?

Answer 10

Any area in the NS composed of mostly unmyelinated axons, dendrites and glial cell processes that forms a synaptically dense region containing a relatively low number of cell bodies.

Question 11

What is grey matter ?

Answer 11

Gray matter is a neuropil area and mainly composed of neuronal cell bodies, unmyelinated dendrites and glia cells.

Question 12

What is white matter ?

Answer 12

White matter mainly contains the myelinated nerve fibers.

Question 13

What are the 2 ways in which neurons can be grouped ?

Answer 13

A cluster = a nucleus

A sheet, layer/lamina = an area

Question 14

How are most neurons arranged in the midbrain and hindbrain ?

Answer 14

In a cluster.

Question 15

How are most neurons arranged in the cerebral and cerebellar cortex ?

Answer 15

In laminae.

Question 16

What do bundles of nerve fibers form ?

Answer 16

Tracts, fasciculus, faniculus or lemniscus.

Question 17

What is the difference between a commissioner and a decussation ?

Answer 17

In both cases, tracts cross over the midline of the brain. Commissures are when the crossing is symmetrical, decussations are when the crossing is asymmetrical.

Question 18

What is the chiasm of chiasma ?

Answer 18

The crossing of the optic nerve.

Question 19

What is the largest commissar in the brain ?

Answer 19

The corpus callosum: it joins the 2 cerebral hemispheres.

Question 20

What are the different types of brain sections ?

Answer 20

Mid-sagittal (between left and right)
Coronal (from up to down)
Horizontal/transverse (from back to front)

Question 21

What parts of the NS are enclosed in bone ?

Why ?

Answer 21

The CNS is enclosed in bone (skull and spine) to protect it from physical trauma. It contains foramina to allow to allow nerves in and out.

Question 22

What are the 3 meninges covering the NS ?

Answer 22

Dura mater, arachnoid and pia mater

Question 23

What are the structures of the 3 meninges ?

Answer 23

• Dura mater: tough, thick fibrous layer inside the bones
• Arachnoid: fine, delicate sheet, connected to the Pia matter by thin, web like elastic strands
• Pia mater: thin membrane clinging to surface of brain,
  spinal cord, into sulci, around blood vessels into CNS
• Between the arachnoid and the pia mater is the subarachnoid space

Question 24

What does the subarachnoid space contain ?

Answer 24

Cerebrospinal fluid (CSF).

Question 25

Are the meninges sensitive to pain ?

Why ?

Answer 25

All three meninges have large blood supply and are innervated. They are thus very sensitive to pain, in contrast to the brain itself which has virtually no pain receptors.

Question 26

What is the role of the CSF ?

Answer 26

• Shock absorption
• Reduces brain weight, from 1500g real weight to 50g effective weight on the bone
• Helps to keep extracellular milieu constant (buffer)
• Movement removes potentially toxic substances
• Produced by choroid plexuses (network of small arteries) which line the inner surface of the ventricles
• Moves from lateral ventricle –> third –> fourth –> subarachnoid space reabsorbed into blood stream by large veins inside the skull
• Circumventricular organs sit in ventricles, sense level of e.g. CO2 in bloodstream and have no blood-brain barrier

Question 27

What is the role of the blood-brain barrier (BBB) ?

Answer 27

• Prevents certain molecules to pass from the blood into the extracellular fluid
of the brain or spinal cord
• Traffic of molecules into the extracellular fluid (ECF) of the brain and spinal
cord is tightly regulated
• ECF composition is important for neuronal excitability
• Toxins and infectious particles (bacteria and viruses) are kept out (but Rabies)
• Molecules that are not transported must pass through the plasma membrane (must thus be lipophilic)
• Important consequences for drug delivery
• Formed by specialized endothelial cells of the brain capillaries, in addition specific cellular transport mechanisms in/out and pumps out of the ECF