Parts of the BrainDr Ajith Sominanda

Department of Anatomy

Nervous System

Environmental stimuli

Information Processing Effects

Nervous system and BrainFew facts from your A/Levels or high school biology

• Nervous system consists of nerve tissues: neurons and glia

• Brain and spinal cord belongs to CNS• In CNS, macroscopically white and gray

matter are identifiable• These white and gray matter are arranged into

different areas of the brain and spinal cord

• In a Fresh brain or Spinal cord.,– White is due to myelinated (protein +l ipid); nerve fibers or

Axons– Gay is due to cells; neurons & gliaBut in imaging techniques gray and white may look different

Nervous system and BrainFew facts from your A/Levels or high school biology

Nervous system and BrainFew facts from your A/Levels or high school biology

Brain in the cranial cavity

• video

Terms in Neuroanatomy encountered in your A/Ls

CerebrumCerebellumBrain Stem (mid brain, pons, medulla)Meningies (Dura mater, arachnoid

mater & pia mater)VentriclesCSF

Nervous SystemCNS (Brain & Spinal cord)PNS (Cranial nerves, Spinal nerves, peripheral ganglia)

Nerve tissueNeuronGlial cell Neurits (Axons & Dendrits)SynapseNerve fiber, ganglia & peripheral nerve

Gray matter & White matterDevelopment

Neuroectoderm, neural tube, neural crest cells

DEVELOPMENT OF THE BRAIN

Is the key to understand its structure

Neural Tube

Neural crests

Development - Major points

• Nervous system develops from an area of ectoderm called neuroectoderm or neural plate of the embryo

• Neuroectoderm give rise to neural tube and the peripheral nerves develop from neural crests

Forebrain

Midbrain

Hindbrain

Naming different areas of the developing neural tube

neural tube bends and grow

Embryo Swollen & Folded neural tube

Cervical flexure

Pontine flexure

Cephalic flexure

Areas of developing neural tube

Areas of developing neural tube and their future components

Forebrain

Midbrain

Hindbrain

Thus, brain is the modified cephalic (front) part of neural tube by growth (swelling) and folding

Main parts of the adult brainRevision

1. ForebrainI. Cerebral hemispheres or cerebrumII. Diencephalon

Thalamus, Epithalamus, Hypothalamus & Subthalamus

2. Midbrain

3. HindbrainI. Pons and CerebellumII. Medulla

FOREBRAINCEREBRUM OR CEREBRAL HEMISPHERES

ForebrainCerebrum or Cerebral hemispheres• Represent the largest part of the brain • Has extensively convoluted cerebral cortex• Has internal white matter fiber bundles• Has internal masses of gray matter • Also contains cavities; lateral ventricles• Two hemispheres are connected by a bundle

of white matter called corpus callosum

ForebrainCerebrum or Cerebral hemispheres

Cerebral Cortex (gray matter)

• Contains cells (neurons & glia)• Extensive folding forms sulci and gyri• Large sulci / fissures divides cerebral

hemispheres into different lobes

• Sulci- Lateral, Central, parieto-occipital• Frontal lobe, Parietal lobe, Occipital lobe & Temporal lobe

Topography of cerebral hemispheres Supero-lateral surface of the brain

Main Sulci and Gyri

Draw

• Cingulate gyrus, cuneus, lingular gyrus• Cingulate sulcus, calcarine sulcus

Topography of cerebral hemispheres medial surface of the brain

Insular lobe

Functional localization

Cerebral White matter

1. Consists of Axons that connect different parts of the nervous system

2. These axons are arranged in bundles which can be displayed by dissection

Cerebral White matter

Three types of axon bundles (fasciculi) are present in cerebral white matter:

A. Association fibersConfined to a hemisphere and connects cortical areas within the hemisphere

B. Transverse or Commissural fibers• Connects 2 hemispheres• Axons runs in corpus callosum and anterior commissure,

C. Projection fibersConnect cerebral cortex with subcortical structures, brain stem and spinal cord

Cerebral White matter

Cerebral White matter

Cerebral White matter

Corpus Callosum (Transverse or Commissural fibers)

Cerebral White matter

Cerebral White matter

Corpus Callosum

Corona radiata & Internal capsule(Contains projection fibers)

Cerebral White matter

Cerebral White matter

More details during the practical sessions

Other internal structures of cerebral hemispheres

• Diencephalic structures (Thalamus, hypothalamus, epi thalamus and sub thalamus)

Other internal structures of cerebral hemispheres

• Telencephalic gray matter– Corpus striatum (telencephalic gray matter associated with lateral

ventricles)• Striatum (caudate nucleus, nucleus accumbens & putamen)• Pallidium (globus pallidus)

Other internal structures of cerebral hemispheres

Histology of cerebral cortex

• Cerebral gray and white matter is (histologically) arranged in layers

• Three Histologically different areas can be identified:1. Paleocortex (olfactory system)2. Archicortex (hipocampal formation) 3. Neocortex (rest of cerebral cortex) -

3 layers

6 layers

Neocortical Histology

Histology of cerebral cortex

There are two types of neurons :1. Principal neurons

a. Typical principal cells are pyramidal cells

b. Atypical principal cells are fusifom cells

2. Inter neurons

Histology of cerebral cortex

Principal neurons connect with other neurons in CNS in 3 ways

I. Projection neurons/fibers (subcortical areas such as thalamus, corpus striatum, brain stem & spinal cord)

II. Association neurons/fibers (connects cortical neurons in same hemisphere)

III. Comissural neurons/fibers (connects cortical neurons in opposite hemisphere )

Histology of cerebral cortex