Parts of the Brain Dr Ajith Sominanda Department of Anatomy.
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Transcript of Parts of the Brain Dr Ajith Sominanda Department of Anatomy.
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