Transcript Parts of the Brain - University of Peradeniya

Parts of the Brain
Dr Ajith Sominanda
Department of Anatomy
Nervous System
Environmental
stimuli
Information
Processing
Effects
Nervous system and Brain
Few 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
Nervous system and Brain
Few facts from your A/Levels or high school biology
• 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 & glia
But in imaging techniques gray and white may look different
Nervous system and Brain
Few facts from your A/Levels or high school biology
Brain in the cranial cavity
• video
Terms in Neuroanatomy encountered in
your A/Ls
Nervous System
CNS (Brain & Spinal cord)
PNS (Cranial nerves, Spinal nerves,
peripheral ganglia)
Nerve tissue
Neuron
Glial cell
Neurits (Axons & Dendrits)
Synapse
Nerve fiber, ganglia & peripheral
nerve
Gray matter & White matter
Development
Neuroectoderm, neural tube,
neural crest cells
Cerebrum
Cerebellum
Brain Stem (mid brain, pons, medulla)
Meningies (Dura mater, arachnoid
mater & pia mater)
Ventricles
CSF
Is the key to understand its structure
Neural crests
Neural Tube
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
Naming different areas of the developing
neural tube
Forebrain
Midbrain
Hindbrain
neural tube bends and grow
Pontine flexure
Cephalic flexure
Embryo
Cervical flexure
Swollen & Folded neural tube
Areas of developing neural tube
Areas of developing neural tube and
their future components
Hindbrain
Midbrain
Forebrain
Thus, brain is the modified cephalic
(front) part of neural tube by growth
(swelling) and folding
Main parts of the adult brain
Revision
1. Forebrain
I. Cerebral hemispheres or cerebrum
II. Diencephalon
Thalamus, Epithalamus,
Hypothalamus & Subthalamus
2. Midbrain
3. Hindbrain
I. Pons and Cerebellum
II. Medulla
Forebrain
Cerebrum or Cerebral hemispheres
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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
Forebrain
Cerebrum 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
Topography of cerebral hemispheres
Supero-lateral surface of the brain
• Sulci- Lateral, Central, parieto-occipital
• Frontal lobe, Parietal lobe, Occipital lobe & Temporal
lobe
Main Sulci and Gyri
Draw
Topography of cerebral hemispheres
medial surface of the brain
• Cingulate gyrus, cuneus, lingular gyrus
• Cingulate sulcus, calcarine sulcus
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 fibers
Confined to a hemisphere and connects cortical areas within the
hemisphere
B.
Transverse or Commissural fibers
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Connects 2 hemispheres
Axons runs in corpus callosum and anterior commissure,
C. Projection fibers
Connect cerebral cortex with subcortical structures, brain stem and spinal
cord
Cerebral White matter
Cerebral White matter
Cerebral White matter
Cerebral White matter
Corpus Callosum
(Transverse or Commissural fibers)
Cerebral White matter
Corpus Callosum
Cerebral White matter
Corona radiata & Internal capsule
(Contains projection fibers)
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)
3 layers
2. Archicortex (hipocampal formation)
3. Neocortex (rest of cerebral cortex) - 6 layers
Histology of cerebral cortex
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 )