anat3022 lectures 1-11

Structural organisation of NS

central nervous and peripheral nervous system

Functional organisation of NS

somatic and autonomic systems (becomes sympathetic and parasympathetic systems)

Cellular organisation of NS

neurones and glial cells

Glia

Non-neuronal cells that provide support and protection for neurons in the nervous system

Astrocytes

A type of glial cell that provides trophic, metabolic and structural support and nourishment to neurone. Part of BBB.

Oligodendrocytes

A type of glial cell that produces myelin, which insulates and protects neurones. Dysfunction indicated in MS

Microglia

The immune cells of the central nervous system that remove cellular debris and bacteria via phagocytosis and release of cytokines/chemokines. Indicated in Alzheimer’s

neurocranium

comprised of cranial vault and cranial base. brain is held via anterior, middle, and posterior cranial fossa (ditches)

hole in cranial base

foramen magnum

1

medulla oblongata

2

pons

3

mesencephalon

4

diencephalon

5

cerebellum

6

telencephalon

gastrulation

formation of 3 germ layers: ectoderm, mesoderm, endoderm

1

prosencephalon

2

mesencephalon

3

rhombencephalon

1

telencephalon

2

diencephalon

3

mesencephalon

4

metencephalon

5

myelencephalon

metencephalon is comprised of

pons and cerebellum

prosencephalon is comprised of

telencephalon and diencephalon

brainstem is comprised of

medulla oblongata, pons, midbrain

medulla oblongata function

The lower part of the brainstem that controls breathing and blood pressure.

pons function

The part of the brainstem that works with the cerebellum to coordinate movement.

mesencephalon/midbrain structures and functions

peduncles, tegmentum, tectum. sensory and motor functions.

diencephalon/interbrain structures and functions

pituitary, thalamus and hypothalamus. involved in hormone secretion and autonomic regulation (homeostasis)

cerebellum functions

motor learning, coordination, balance

telencephalon structures and functions

cerebrum; executive functions, memory, perception

brainstem structures and functions

medulla oblongata, pons, mesencephalon.

control of head/neck via cranial nerves, consciousness via reticular formation, supraspinal reflexes

multipolar neurone

one of most abundant

‘classic neurone’

projecting neurones

motor and pyramidal neurones

unipolar neurone

exocrine glands and smooth muscle

bipolar neurone

senses, smell, sight

pseudo-unipolar neurone

sensory neurones, e.g. dorsal root ganglia

eminence

prominent protrusion

folia

cerebellar gyri

blue plane

coronal/frontal

green plane

horizontal/axial/transverse

red plane

sagittal/longitudinal

peduncle

prominent stalk attaching part to brain, interconnecting regions

meninges

membranous connective tissue

dura mater, leptomeninges (arachnoid and pia mater)

meninges inside longitudinal fissure

falx cerebri

meninges between base cerebrum and cerebellum

tentorium cerebelli

gyri/sulci of frontal lobe

3 horizontal: superior, middle, inferior

1 vertical: precentral

gyri/sulci of temporal lobe

superior, middle, inferior

transverse temporal (Heschl gyrus) (auditory cortex), found inside lateral sulcus

commissural fibres of corpus callosum

connects frontal, occipital, parietal lobes (300m axons)

commissural fibres of anterior commissure

connects temporal lobes (5m axons)

association fibres

connect intra-hemispherically

short arctuate fibres

connect neighbouring gyri

long arctuate fibres

connect distant gyri

superior longitudinal fascicle

connects ipsilateral occipital and frontal lobes

inferior occipitotemporal fascicle

connects occipital and temporal lobes

cingulum and uncinate fascicle

connect limbic cortices of frontal and temporal lobes

arcuate fasciculus

connects Broca’s and Wernicke’s areas

projection fibres

efferent and afferent fibres connecting cerebral cortex with deep cerebral nuclei (e.g. basal ganglia), brainstem, and spinal cord

all projection fibres pass through corona radiata

meninges

Membranous connective tissue covering the brain

3 layers of meninges

dura mater

arachnoid mater

pia mater

dura mater

Thickest layer with 2 sub-layers: periosteal layer and meningeal layer. dura septa prevents brain displacement.

arachnoid mater

Middle layer with many blood vessels and contains the subarachnoid space filled with CSF.

pia mater

Innermost and thinnest layer that directly contacts the brain.

how CSF from the brain is returned

drains into sinuses of dural septa, which are large veins formed by meningeal layers, such as the superior sagittal sinus, inferior sagittal sinus, and sinus rectus/straight sinus.

From sinuses, CSF is drained into the jugular vein and re-enters the bloodstream

superior sagittal sinus

on top of falx cerebri

inferior sagittal sinus

ventral to falx cerebri

sinus rectus (straight)

in middle of tentorium cerebelli

dura septa

where layers of dura mater split. prevents brain from moving around

1

anterior horn of lateral ventricle

2

posterior horn of lateral ventricle

3

inferior horn of lateral ventricle

4

3rd ventricle

5

intraventricular foramen

6

cerebral aqueduct / aqueduct of sylvius

7

interthalamic adhesion

8

4th ventricle

9

intraventricular foramen of Monro / lateral aperture

10

foramen of Luschka / lateral aperture

11

foramen of Magendie / median aperture

12

central canal

CSF production

mainly from the choroid plexus, located in the ventricles

choroid ependymal cells

tight junctions with choroid epithelial cells, BBB, control CSF composition via tight junctions and active ion transport

CSF circulation

CSF produced in the lateral ventricles, travels through the intraventricular foramen, joins the 3rd ventricle, goes down the aqueduct of Silvius, and enters the 4th ventricle

CSF release

CSF exits the 4th ventricle via two apertures, the median aperture (foramen of Magendie) and the lateral aperture (foramen of Luschka), goes into the subarachnoid space

CSF filtration

CSF circulates around the brain and is filtered at the arachnoid granulations before entering the superior sinuses and returning to the bloodstream via the jugular vein

purpose of CSF

physical support to brain (cushion)

buoyancy (reduces net weight from 1.4kg to \~25g)

waste excretion

nourishment and communication (chemical messenger distribution through CSF)

perivascular drainage pathways

how ISF leaves the brain

flows from intramural perivascular drainage system to cervical lymph nodes

glymphatic system

glial-dependent

astrocytes allow exchange of CSF and ISF from brain parenchyma and drainage directly into vessels via aquaporin-4 channels on feet of astrocytes

CSF circulation

acts as sink for waste, exogenous solutes/compounds

meningeal lymphatic routes

specific for meninges

important for immune surveillance

4 lymphatic drainage pathways of brain

perivascular drainage pathways, glymphatic system, CSF circulation, meningeal lymphatic routes

main arterial blood supply to brain

vertebral and carotid artery

vertebral artery

supplies posterior circulation

branches into PICA, posterior spinal artery, AICA, and fuses into the basilar artery

basilar artery

branches into superior cerebellar artery and posterior cerebral artery, supplying various brain regions

internal carotid artery

supplies anterior circulation (80% of blood flow). Branches into ophthalmic artery, then anterior cerebral artery, supplying the frontal and parietal lobes.

deep veins

great cerebral vein receives from internal cerebral veins and basal veins, draining into the sinus rectus and returning to the jugular vein

superficial veins

superior cerebral veins drain into the superior sagittal sinus, and the middle cerebral vein drains into the superior sagittal sinus and pernicular sinus

ischaemic stroke

caused by artery blockage from clot or plaque, leading to reduced blood flow to a brain region

middle cerebral artery occlusion (MCAO)

most common stroke type. affects the M1 (primary motor cortex), leading to hemiplegia, aphasia, and neglect