Week 1 - Introduction to Brain Structure and Function

Dorsal

Superior

Caudal

Posterior

Rostral

Anterior

Ventral

Inferior

How can infection spread from scalp to cranial cavity?

Emissary veins

What is the brain contained by?

Three meninges

What are the 3 meninges of the nervous system?

Dura mater

Arachnoid mater

Pia mater

What are the reflections/folds of the dura mater?

Falx cerebri

Tentorium cerebelli

Falx cerebelli

What are tentorial tumours?

Rare tumours formed in the tentorium cerebelli

They can be infratentorial and supratentorial

What is meningeal haematoma?

Blood clot that forms between layers of meninges

There are 3 types: subarachnoid, subdural and epidural

What is the role of falx cerebri?

Separates hemispheres

What is the role of tentorium cerebelli?

Separates occipital lobe from cerebellum

What is the role of falx cerebelli?

Separates cerebellar hemispheres

What does the arachnoid mater contain?

Blood vessels

Cerebral spinal fluid

Granulations to drain CSF back into the venous system

What does the pia mater follow?

The contour of the brain

What is cortical sulci?

Surface landmarks on the brain

Grooves or indentations between cortical gyri

What is the precentral sulcus?

Creates anterior border of the motor cortex

What is the central sulcus?

Separates frontal and parietal lobes

What is the lateral sulcus?

Separates the parietal and temporal lobes

What is the parieto-occipital sulcus?

Separates parietal and occipital lobes

What is the marginal sulcus?

Separates the precuneus from the paracentral lobule

What is the cingulate sulcus?

Separates limbic and frontal lobes

A cortical sulci

What is the calcarine sulcus?

Separates the occipital lobe into superior and inferior halves

What is cortical gyri?

Raised, ridged parts of the cortex

What is the precentral gyrus?

Primary motor cortex

What is postcentral gyrus?

Primary somatosensory cortex

Where is the central sulcus located?

Between the precentral gyrus and the postcentral gyrus

What are the cortical lobes?

Frontal lobe

Parietal lobe

Temporal lobe

Occipital lobe

What separates the frontal lobe from the central lobe?

Central sulcus

What is the role of the frontal lobe?

Personality

Attention

Motivation

Planning movement

What is the role of the parietal lobe?

Integrating sensory information

Language processing

What is the role of the temporal lobe?

Memory

Sensory processing

Language comprehension

What is the role of the occipital lobe?

Vision

What is the rhombencephalon?

Hindbrain

What is hindbrain made up of?

Metencephalon and myelencephalon

What does the metencephalon become?

Pons and cerebellum

What does the myelencephalon become?

Medulla oblongata

What is the mesencephalon?

Midbrain

What does the mesencephalon become?

Tectum (colliculi)

Tegmentum

Cerebral peduncles

What is the prosencephalon?

Forebrain

What is the forebrain separated into?

Diencephalon

Telencephalon

What does the diencephalon become?

Thalamus

Hypothalamus

What does the telencephalon become?

Basal ganglia and cortex

Building the brain diagram

What is the role of the cerebellum?

Balance

Coordination

Synchorization of muscles

What is the brain stem made up of?

Midbrain

Pons

Medulla oblongata

What is the role of the midbrain?

Motor control via cerebral peduncles (motor tracts)

Vision and hearing tectum

Consciousness via reticular formation

Also contains the substantia nigra and red nucleus

What is the role of the cerebral peduncles?

Controls motor processes

Motor tracts

What is the role of the substantia nigra?

Produces dopamine

What is the role of red nucleus?

Coordinates movement

What is the role of the tectum?

Vision and hearing

What is the role of the reticular formation?

Consciousness

What is the role of the pons?

Relays information to the cerebellum

Some direct connections with cortex

What is the role of the medulla oblongata?

Respiration

Heart rate

Vomiting

Sneezing

What is the role of the thalamus?

Major relay station for sensory information from body

What is the role of the hippocampus?

Memory and spatial navigation

What is the role of hypothalamus?

Hormone synthesis

Temperature

Hunger

Thirst

Sleep

What is the role of ventricles?

Series of inter-connected, fluid filled cavities that cushion the brain and bathe it in cerebral spinal fluid

-Lateral ventricles

-Third ventricle

-Cerebral aqueduct

-Fourth ventricle

What is the role of the caudate nucleus and putamen (basal ganglia)?

Planning movement

Cognition

Emotion

Diagram to show the ventricular system

What are ventricles filled with?

Cerebral spinal fluid

How is CSF produced?

Produced in choroid plexus

Approx 150mL of CSF is exchanged 3 times each day

We produce approx 500mL of CSF every day

What is the role of CSF?

Colour-less liquid that baths the brain

Assists in circulating substances

Provides cushioning

Absorbs shock

What is the choroid plexus?

A group of cells that line ventricles

Produces CSF and then induces CSF circulation

Medium of exchange between the extra cellular fluid and the bloodstream

What is the role of the inter-ventricular foramen?

Connection between lateral ventricle and the third ventricle

Allows CSF circulation

How does CSF circulate?

Lateral ventricles →

Interventricular foramen →

Third ventricle →

Cerebral aqueduct →

Fourth ventricle →

Subarachnoid space (around the brain and spinal cord) and central canal (in the spinal cord).

CSF then gets reabsorbed into the bloodstream via the arachnoid villi in the dural sinuses, completing the cycle.

What is hydrocephalus?

Accumulation of CSF

Causes enlarged ventricles

Which vertebral levels is safe for CSF sampling in adults?

L3-L4

L4-L5

Which vertebral levels is safe for CSF sampling in infants?

At or below L4-L5

How does CSF enter the cisterns and subarachnoid space?

Via a series of apertures

Occurs before being circulated upwards

How is CSF reabsorbed?

Arachnoid granulations

What is the arterial supply of the brain?

The internal carotid arteries (anterior circulation)

The vertebral arteries (posterior circulation)

What are the terminal branches of the internal carotid artery?

Anterior cerebral arteries

Middle cerebral arteries

What do the vertebral arteries form?

Merges to form the basilar artery

What does the basilar artery give rise to?

Branches:

Anterior inferior cerebral arteries

Pontine arteries

Superior cerebral arteries

Terminates with posterior cerebral arteries

How does the brain have dual blood supply?

Two pairs of vessels: internal carotid arteries and vertebral arteries

What is the circle of Willis?

Major anastomosis for the brain

Connects posterior and anterior circulation using anterior communicating artery and posterior communicating artery

Diagram to show arterial territories

Diagram to show subcortical blood supply

What do the vertebral arteries specifically supply?

Posterior aspect of the brain

What do the posterior inferior cerebellar arteries supply?

Posterior cerebellum

What does the basilar artery supply?

Brainstem

What do the inferior anterior cerebellar arteries supply?

Anterior cerebellum

What do the superior cerebellar arteries supply?

Cerebellum

What do the posterior cerebral arteries supply?

Medial occipital

Inferior temporal lobe

Hippocampus

What do the carotid arteries supply?

Anterior aspect of the brain

What do the carotid arteries divide into?

Anterior cerebral arteries

Middle cerebral arteries

Lenticulostriate arteries

What do the anterior cerebral arteries supply?

Medial frontal and superior parietal lobe

Corpus callosum

What do the middle cerebral arteries supply?

Lateral temporal and parietal lobes

Posterior frontal lobe

What are lenticulostriate arteries?

Subcortical structures

Diagram to show surface venous drainage of the brain

Diagram to show medial venous drainage of the brain

Which sinuses do surface venous drainage?

Superior sagittal sinus

Confluence of sinuses

Transverse sinuses

Sigmoid sinus

Which sinuses and veins do medial venous drainage?

Inferior sagittal sinus

Straight sinus

Internal cerebral veins

What is the role of the blood brain barrier?

An interface that ensures the circulatory system is kept separate from CSF

Which cell junction forms the blood brain barrier?

Tight junctions

How do tight junctions form in the blood brain barrier?

Blood vessels are composed of a layer of endothelial cells

When two cells touch their membranes together create a barrier

This barrier only allows passage of selected material between the blood and the brain

Which molecules are allowed through the blood brain barrier?

Small molecules (oxygen, carbon dioxide, glucose or select amino acids)

Which cells are responsible for maintaining the BBB?

Pericytes and astrocytes

What surrounds endothelial cells?

Basement membrane