Topography of the brain

Question 1

Describe the development of the brain (neurulation)

Answer 1

Neuroectoderm cells receive inductive signals from notochord
Cells thicken to form neural plate
Lateral neural plate margins fold inwards to form neural tube

Question 2

Which cells (cell types) arise from the differentiation of neural crest cells?

At what age does this occur?

Answer 2

1. Neurons and glia of the sensory and autonomic nervous systems
2. Cells of the adrenal gland
3. Epidermis
4. Skeletal/ connective tissue of the head

Embryonic day 24

Question 3

What is the function of the mantle layer, ependymal layer and lumen of the neural tube?

Answer 3

Mantle layer becomes the brain parenchyma
Ependymal lines the ventricles
Lumen becomes the ventricles and central canal

Question 4

Describe 2 neural tube defects

Answer 4

Anencephaly: Failure of anterior neuropore to close. 1/1000. FATAL

Spina bifida: failure of posterior neural tube to close. 1-2/1000. Leads to open vertebral canal

Question 5

Whats the difference between spina bifida occulta and spina bifida cystica?

Answer 5

SBO- hidden, vertebral arch defect only

SBC- e.g. meningocele= meninges projects out

Question 6

Expansion of the cranial end of the neural tube forms the the main brain regions. What are these?

Answer 6

Prosencephalon= forebrain
Mesencephalon= midbrain
Rhombencephalon= hindbrain

Primary vesicles on LHS

Question 7

Which secondary vesicles arise from the prosencephalon (forebrain)?

Answer 7

Telencephalon= cerebral hemispheres
Optic vesicles= eyes
Diencephalon= thalamus/hypothalamus

Question 8

Which secondary vesicles arise from the Rhombencephalon (hindbrain)?

Answer 8

Metencephalon= Pons/cerebellum
Myelencephalon= Medulla

Question 9

Which secondary vesicles arise from the Mesencephalon (Midbrain)?

Answer 9

None

Question 10

At which embryonic day do the secondary vesicles arise?

Answer 10

36

Question 11

What is the difference between gray and white matter?

Answer 11

Gray matter (peripheral)- mainly neuronal cell bodies (e.g. cerebral cortex, brain nuclei)

White matter- mainly myelinated axons

Question 12

What is the telencephalon and how is it arranged?

Answer 12

Comprises the cerebral hemispheres/cerebral cortex, components of the limbic system and the basal ganglia

Divided into lobes: 
frontal- primary motor cortex
parietal- somatosensory cortex
temporal- auditory and olfactory cortex
occipital- primary visual cortex

Question 13

What is the cerebral cortex?

Answer 13

Outer layer of the cerebral hemispheres
Folded to form gyri and sulci

Precentral gyrus (motor), central sulcus (divides frontal and parietal lobes), postcentral gyrus (sensory), lateral sulcus (divides temporal from parietal lobe)

Question 14

What is the corpus callosum?

Answer 14

White matter tract linking cerebral hemispheres.

3 parts:
Genu- contains axons from pre-frontal complex
Body- contains motor axons
Splenium- contains sensory axons

Question 15

Briefly state the deep brain structures

Answer 15

Brain nuclei and white matter tract deep to cerebral hemispheres
Interconnected to form important neural pathways including:

Limbic system- involved with emotion and memory
Basal ganglia- involved in the control of posture and voluntary movement

Question 16

Explain the limbic system

Answer 16

Spans the telencephalon and diencephalon

Components include: cingulate cortec, fornix, hypothalamus, mammillary bodies, amygdala, hippocampus

The fornix is a semi-circular white matter tract connecting the hippocampus with the mammillary bodies

Question 17

What is continuous with the hippocampus?

Answer 17

Dente gyrus

Question 18

Describe the basal ganglia

Answer 18

Series of interconnected nuclei at base of forebrain

It includes

1. Lentiform nucleus (lens shaped)- sits lateral to caudate nucleus
2. Caudate nucleus (C-shaped)- sits in wall of lateral venricle

Question 19

Describe the capsules

Answer 19

There two

Internal capsule forms major white matter tract (its internal to leniform nucleus)

External capsule external to leniform nucleus

Question 20

Describe the diencephalon

Answer 20

Comprises the thalamus and hypothalamus (+corpus callosum and fornix)

Question 21

Describe the thalamus

Answer 21

Paired structure
Relays sensory information to the cortex
Involved with voluntary movement, personality and consciousness

Interthalamic adhesions connect the thalamus

Question 22

Describe the hypothalamus

Answer 22

Inferior to the thalamus, between the optic chiasm and mammilary bodies
Involved in homeostasis- coordinates ANS and endocrine processes, thermoreg, feeding, drinking, circadian rhythms and recieves inputs from limbic system

Question 23

What is contained within the brainstem?

Answer 23

Cranial nerve nuclei within all three regions
Vital respiratory and cardiovascular centres
Vomiting centre
Nuclei involved with motor control, sleep
White matter tracts

Question 24

In the midbrain describe the function of the cerebral peduncles, superior colliculus and inferior colliculus.

Answer 24

Cerebral peduncles- white matter tracts connecting pons with diencephalon

Superior colliculus- vision (eye movements)
Inferior colliculus- auditory (relay nuclei)

Question 25

In the midbrain, describe the role of the red nucleus and substantial nigra

Answer 25

Red nucleus- motor coordination- relay between cortex and cerebellum Substantial nigra- dopaminergic neurons, part of basal ganglia

Question 26

What are the features of the Pons (Rhombencephalon) and what does it do?

Answer 26

Relays information to the cerebellum 90% of axons descending through midbrain synapse in pons Transverse fibres forming cerebellar peduncles - Middle cerebellar peduncle is a white matter tract linking the brainstem to cerebellum Contains reticular formation -Nuclei concerned with sleep, motor control

Question 27

What are the features of the medulla oblongata and what does it do?

Answer 27

Pyramid- corticospina tract- main voluntary motor pathway Olive- formed by olivary nuclei Motor relay to cerebellum Cuneate tubercle and gracile tubercle - nuclei form part of ascending tract Contains nuclei that are important in controlling respiration and the CVS

Question 28

What does the Cerebellum look like and what does it do?

Answer 28

``` Posterior to brainstem Outer gray matter with underlying white matter 2 cerebellar hemispheres Three lobes Contains nuclei ``` Main functions in motor control: Control of posture Coordinating and planning limb movements Control of eye movements

Question 29

State the anatomical features of the cerebellum

Answer 29

``` Arbor vitae (tree of life) Cerebellar cortex ``` Anterior lobe Flocculonodular lobe Posterior lobe Two hemispheres - left and rights Vermis in middle Connected to brainstem by cerebellar peduncles