Neuroanatomy

anatomical directions

longitudinal axis of the brain

two longitudinal axis:

• forebrain (more horizontal)

• brainstem (more vertical)

rostral = towards the nose (forebrain axis)

caudal = going down the spinal cord (forebrain/brainstem axis)

cranial = going upwards towards the brain (brainstem axis)

dorsal//ventral in the spinal cord v brain

relative terms:

• ascending

• descending

• bilateral

• ipsilateral

• contralateral

• decussates

anatomical planes

sagittal plane = midline

cronal plane v horizontal plane

cronal plane = divides front and the back

horizontal plane = divides anterior and posterior

grey matter

made up of 2neuronal cell bodies, dendrites and unmyelinated

2 main groups:

• a nucleus (ganglion in PNS) a definable group of cells e.g. thalamic, common in midbrain

• cortex - neuronal cell bodies organised into layers (lamina), usually found on surface of CNS e.g. cerebrum

2 main classes of neurons found in grey matter

1. local interneurons

• axons terminate in same structure as cell body

• involved in local computations

2. projections cells

• neurons that send axon to another region

• these are the origins of various tracts

nuclei v tracts

white matter

appears white due to myelin presence

• contains lots of nerve fibre (myelinated axons)

• composed of a bundle of axons (tracts)

decussation in the white matter

a crossing of nerve fibres from one side of the body or brain to the opposite side (contralateral) e.g. pyramidal decussation in lower medulla

commissures

tracts (nerve fibres) that cross the brain or spinal midline, connecting matching regions between the left and right sides

e.g corpus callosum, anterior commissure, posterior commissure

corpus callosum: thick band of 200-300 million nerve fibres located deep in the middle of the brain, acts as a bridge connecting the left and right cerebral hemispheres

distribution of white/grey matter in the brain and spinal cord