Neuroanatomy (L1)

The nervous system

Central nervous system (CNS):

- Brain (encased in skull).

- Spinal cord (encased in vertebral column).

Peripheral nervous system (PNS):

- All other nerves.

- Motor pathways send information to muscles or tissue from CNS.

- Sensory pathways bring information from sensory surfaces into CNS.

The brain

1. Cerebrum

2. Cerebellum

3. Brain stem

Split into two hemispheres: left and right.

- Left controls right side of the body.

- Right controls left side of the body (contralateral = opposite side).

- Ipsilateral: same side of the brain controls a function.

The brain receives a constant flow of blood (approx. 20% flow from the heart) in order to maintain oxygen levels.

- If deprived = unconsciousness.

- A stroke is a bleed or blockage in the brain → results in brain cells dying due to lack of oxygen.

Anatomical directions

- Dorsal/superior (top of brain).

- Caudal/posterior (back of brain).

- Ventral/inferior (bottom of brain).

- Rostral/anterior (front of brain).

- Medial: towards the middle

- Lateral: towards the side

Slicing sections

- Frontal (coronal): parallel to forehead (cutting down).

- Sagittal: arrow (cutting sideways).

- Horizontal: parallel to the ground.

Grey and white matter

Grey matter:

- Cell bodies and dendrites.

- E.g. cortex, basal ganglia, thalamus.

White matter:

- Myelinated axons.

- E.g. corpus callosum (a pathway that connects left and right side of hemisphere → commissure).

Corpus callosum

- "Hard body".

- Largest fibre bundle that connects the two hemispheres.

Protection of the nervous system

Meninges: 3 layers of tissues that protect the CNS.

- Outer layer: dura mater (hard mother) → thick and rough.

- Middle layer: arachnoid membrane (spider-like).

- Inner layer: pia mater (tender mother) → covers the brain.

- Meningitis is an inflammation of the meninges resulting from viral or bacterial infection.

Cerebrospinal fluid (CSF):

- A clear liquid that fills the subarachnoid space.

- Functions as a shock absorber.

The ventricular system

- Ventricles: hollow cavities filled with CSF.

- Lateral ventricles (x2): membrane called choroid plexus produces CSF by filtering blood.

- Third ventricle

- Cerebral aqueduct

- Fourth ventricle

- Function of CSF and ventricles: exchange of materials between blood vessels and brain tissue → nutrients supplied and waste removed.

Blood-brain barrier

A semipermeable barrier between the blood and the brain produced by the cells in the walls of the brain's capillaries.

- Small molecules (oxygen, carbon dixoide) and lipid-soluble substances can pass through.

- Large molecules (e.g. glucose) must be actively transported through walls.

- Purpose is to provide protection from damaging chemicals and maintain a stable environment.

- Can make it difficult for certain medicines to get in the brain (e.g. chemotherapy drugs).

Cerebral cortex

- Outer surface of the cerebrum.

- 3mm thick

- Folded to allow for bigger surface area (more neurons).

- Sulci: clefts/cracks/groves.

- Fissures: major grooves.

- Gyri: folds/bulges.

Cerebral cortex: lobes

Frontal

Parietal

Occipital

Temporal

Major sulci and gyri

- Central sulcus: divides frontal and parietal lobes.

- Precentral gyrus:

- Postcentral gyrus:

- Sylvian/lateral fissure: divides temporal lobe from frontal and parietal lobes.

Frontal lobe

- Anterior area of cortex.

- Rostral to parietal.

- Dorsal to temporal.

- Divided from parietal by central sulcus.

- Functions: motor and cognition.

Parietal lobe

- Caudal to frontal.

- Dorsal to temporal.

- Function: somatosensory → directing movement (e.g. when interacting with objects in the environment).

Occipital lobe

- Caudal to parietal and temporal.

- Function: visual processing.

Temporal lobe

- Rostral to occipital.

- Ventral to parietal and frontal.

- function: hearing, vision, cognition and emotion.

Primary areas

Areas of the cortex involved in sensory functions and in the direct control of motor movements.

- Primary somatosensory cortex: recieves input from somatosensory system (e.g. touch and body position).

- Primary visual cortex: receives input from visual system

- Primary auditory cortex: receives input from auditory system

- Primary motor cortex: controls muscles

Primary association areas

Sensory association areas:

- Receive and analyse info from primary regions.