The Human Brain

Question 1

Human CNS structure is…

Answer 1

Tubular

During development the structure expands and there is differential growth at rostral(top) and caudal(bottom) ends

Question 2

What happens days after fertilisation 
Days:
19 
20
22
26

Answer 2

19- flat cells with neural plate
20- neural groove
22- neural crest
26 - tube formed as 2 sides touch and fuse

Question 3

Neural tube defects
Cause
Defects caused by caudal and rostral failure to close

Answer 3

Caused by lack of folic acid
Rostral end fails - anencephaly
Caudal end fails - spina bifida

Question 4

Primary brain vesicles

Define vesicles
Name 4 primary divisions

Answer 4

Vesicles - fluid-filled swelling at rostral end of the neural tube

Prosencephalon
Mesencephalon = midbrain
Rhombencephalon = hindbrain (m and m)
Spinal cord

(Early vesicles grow and expand differentially)

Question 5

Secondary brain vesicles

Answer 5

Flexicons and outpocketings continue
Structures:(top to bottom)
Telencephalon 
Optic vesicle
Diencephalon
Metencephalon- pons and cerebellum
Myelencephalon - medulla oblongata 
Spinal cord

Telencephalon + diencephalon = forebrain
M and m = rhombencephalon split in 2 (pontine flexure is the bend between the 2)

Question 6

Spinal cord transverse section shows..
Protection?
Type of nerve roots that extend from spinal cord?

Answer 6

Transverse section shows: white and grey matter(process/ neuronal cell bodies) around a central canal

Protection - encased in bony vertebrae

Nerve roots:
Dorsal roots - Carry sensory input
- swelling = dorsal root ganglion
Ventral roots - Carries motor commands out
- no swelling
(Neuronal cell bodies in ganglion)

Question 7

Spinal cord interneuron are important when?

Where do they connect between?

Answer 7

Important for reflexes– can be ipsilateral or contra lateral = allows reflexes on both sides (coordination)
Between sensory and motor neurons

Question 8

Spinal cord columns
Facts about pathways?
What is decussation and where does it happen?

Answer 8

Pathways run up and down? Bilateral ascending and descending pathways
Pathways have multiple connections and many cross over

Decussation - cross over like Roman numeral X
Happens in the medulla for motor cortex

Question 9

Meninges of spinal cord
Define
3 types

Answer 9

Cord is protected by layers of membrane

1) pia mater - closest to spinal cord
2) arachnoid
3) dura mater - furthest form spinal cord (fibrous protective sheath)
- -continuous with those of the brain–

Question 10

Meninges of the brain
What happens to pia mater, Arachmoid and dura mater?

Dura sinus?

Answer 10

Pia stays
Arachnoid stays 
Dura splits into 2:
1) endosteal layer (periosteal)
2) meningeal layer
'Dura sinus' - large vein like structures

Question 11

Cerebrospinal fluid flows where?
What are aperture?

Use of CSF?

Sampling CSF?

Disorders of CSF?

Answer 11

Flows in central canal, brain ventricles and subarachnoid space
Aperture - holes that allow fluid formed on inside to get to subarachnoid space

CSF floats and cushions CNS
If you lose CSF = can reduce blood flow

Sampling - lumbar puncture
Needle inserted between 3rd and 4th lumbar vertebrae (no spinal cord here)

Disorders - hydrocephalus
Internal = increase in intra cranial pressure- causes cell death due to reduce in blood flow
External = pressure externally

Question 12

Blood- brain Barrier?

Answer 12

Separates circulating blood from brain extra cellular fluid

Physiological barrier:

• capillary endothelial cells
• tight junctions connect endothelial cells
• astrocytes

Question 13

Coronal plane
Transverse plane
Midsaggital

Answer 13

Coronal plane - frontal plane
Transverse plane - horizontal
Midsaggital - saggital and parasagittal (cut corpus callosum)

Question 14

4 divisions of brain

Answer 14

Brain stem
Cerebellum
Diencephalon
Cerebrum

Question 15

What 3 parts make up the Brain stem?

Key facts about brain stem?

Answer 15

Medulla oblongata
Pons
Mesencephalon

Fibre tracts and ‘housekeeping’ nuclei
Ascending and descending tracts
Decussation

Reticular formation occurs in brain stem

Question 16

Medulla oblongata major features?

Answer 16

Fibre tracts
Nuclei - CVS, respiration
Olives - cerebellum
Nerve roots

Large lesions? = death due to no respiratory rhythm

Question 17

The pons major feature?

Answer 17

Bridges side of cerebellum
Connects to cerebellum via peduncles
Respiratory centres
Fibre tracts

Question 18

The cerebellum
structure?
Roles?
Cerebellular ataxia?

Answer 18

Folia
Layers - molecular layer, purkinje cell layer, granule layer, white matter
Deep nuclei
White matter = arbar vitae
roles– muscle tone, coordination, motor error correcting, learning
Cerebellular ataxia– loss of cerebellar neurons = jerky imprecise movements

Question 19

Mesencephalon or midbrain

Answer 19

Cerebral peduncles

Tectum- superior and inferior colliculi
- visual(superior) and auditory(inferior) reflexes

Substantia nigra - the black substance
(Associated with Parkinson’s due to role in the regulation of movement)

Nucleus ruber - red nucleus

Question 20

Diencephalon
Part of what part of brain?
What does it link?
Contains?

Answer 20

Part of forebrain
Links midbrain and cerebrum
Contains: thalamus, hypothalamus and pineal

Thalamus– processing and relay centre- all special senses, except smell -synasthesia– motor role, arousal, higher functions

Hypothalamus– eating, drinking, sexual behaviour, stress

Pineal – endocrine organ, melatonin and serotonin

Question 21

The cerebrum
How many hemispheres?
What are the bumps and grooves called? (And what are they for)

Identify the 6 lobes

Answer 21

2 hemispheres
Gyri and fissure(to increase SA)

Frontal, parietal, occipital, temporal (on surface)
Central(insula), limbic

Question 22

Cerebral cortex
What is the outer cortex surrounding?

Name the 3 structures within the cerebral cortex

Answer 22

White matter and deep nuclei
2 lateral ventricles
Wall = much thicker for an adult
Lots of structures and groupings of neurons e.g.striatum

1.Caudate nucleus, 2.putamen, 3.global pallidus
1+2= aka corpus striatum
2+3 = aka lentiform nucleus

Question 23

Cortical structures
How thick?
Layers of what?
How many layers of cells below white matter? Name them

Answer 23

V thin- 3-mm of cells
Layers of neocortex(not all areas of cortex in same in structure)

Generally 6 layer of cells below white matter:

1. Molecular layer
2. External granular layer
3. External pyramidal layer
4. Internal granular layer
5. Internal pyramidal layer
6. Fusiform layer

Question 24

How was mapping done?

Brodmann’s area
Phineas gage
Brocas aphasia
Wernickes aphasia

Modern mapping

Answer 24

Mapping by lesion(pathologist approach) and direct stimulation (anatomical approach)

B area- cytoarchitecture (allowed people to predict what could happen if damage occurred in certain areas)
Phineas gage - damaged frontal lobe= personality change
Brocas - inability to produce speech sound, left frontal lobe damage, expressive aphasia, impaired speech
Wernickes- posterior temporal lobe damage, language comprehension ruined, receptive aphasia= fluent but inappropriate wording

PET scanners, MRI, regional blood flow
Reading =visual cortex lights up(wernickes and Broca’s area)
Association cortex - most cortical area (receives input from many source+ modalities)
– so brain can compile and understand info

Question 25

Lateralisation
Left hemisphere?
Right hemisphere?

Why differences in function?

Answer 25

Left - speech, calculation, analysis
Right- spatial, conceptual, artistic

Due to?
Differential gene expression, gender diff, nature vs. Nurture

Question 26

Basal ganglia
What is it?
Where?
Function

4 structures in it?

Answer 26

Type of nuclei
Deep within hemispheres
Movement regulation so problem = huntingtons or Parkinson’s
1) striatum –caudate and putamen
2) globus pallidus
3) subthalamic nucleus
4) substantia nigra(mesencephalon) – linked due to function not anatomically

Question 27

Limbic system
Function?
4 structures?

Answer 27

Memory and emotions

1) limbic lobe (6th lobe)
2) hippocampus and amygdala
3) thalamus and hypothalamus
4) reticular formation

Hippocampus associates in limbic system due to roles in:
Memory, emotions and motivation

Question 28

Cerebral fibre tracts
What are they?
3 types of fibres?

Answer 28

Pathways and projections
Association fibres - link areas within a hemisphere
Commissural fibres - connect between hemispheres (fewer in males)
Projection fibres - link to non-cortical areas (leave the cerebral hemispheres)