Transcript Motor Area of the Cerebral Cortex

‫بسم هللا الرحمن الرحیم‬
Each Cerebral hemisphere is made
from:
 Cortex, a superficial gray mater
 Centrum Semiovale, a deep massive
neuronal processes, (white mater)
 Deep basal nuclei
 Lateral ventricle
Ventricular System
Lateral Ventricles
Third Ventricle
LV
LV
3rd
Cerebral Aqueduct
Fourth Ventricle
Central Canal
4th
Lateral Ventricle
Body
Horn
Anterior Horn
Frontal Lobe
Posterior Horn
Occipital Lobe
Parietal Lobe
Inferior Horn
Temporal Lobe
Four Ventricles
CSF filled chambers
Communicating with central canal of spinal cord
Lined by ependymal cells
Basal Nuclei
- The term basal nuclei (basal ganglia) is applied to a collection of masses of gray
matter situated within each cerebral hemisphere.
They are the:
1. corpus striatum
2. the amygdaloid nucleus
3. the claustrum
The corpus striatum is situated lateral to the thalamus. It is almost completely
divided by a band of nerve fibers, the internal capsule, into the caudate nucleus and
the lentiform nucleus
The caudate nucleus, a large C-shaped mass of gray matter that is closely related
to the lateral ventricle, Iies lateral to the thalamus
Brain white mater
1. Commissural fibers:
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Corpus callosum
Fornix
Anterior commisure
Posterior commisure
habenularc ommissure
2. Association fibers:
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Long association
Short association fasciculus
Superior long association fasciculus
Inferior long association fascculus
Uncinate (frontotemporal) fasciculus
3. Projection fibers
– Ascending
– Descending
Red: projection fibres
Green: commissural fibres
Blue: association fibres
Forceps major & minor &
tapetum
The anterior commissure is a small bundle of nerve fibers that crosses the
midline in the lamina terminalis
When traced laterally a smaller or anterior bundle curves forward on each
side toward the anterior perforated substance and the olfactory tract.
A larger bundle curves posteriorly on each side and grooves the inferior
surface of the lentiform nucleus to reach the temporal lobes'
Anterior commissure
The posterior commissure is a bundle of nerve fibers that crosses the midline
immediately above the opening of the cerebral aqueduct into the third
ventricle
It is related to the inferior part of the stalk of the pineal gland
Various collections of nerve cells are situated along its length. The
destinationsand functional significance of many of the nerve fibers are not
known
However the fibers from the pretectal nuclei involved in the pupillary light
reflex are believed to cross in this commissure on their way to the
parasympathetic part of the oculomotor nuclei.
The fornix is composed of myelinated nerve fibers and constitutes the efferent system
of the hippocampus that passes to the mammillary bodies of the hypothalamus
The nerve fibers first form the alveus,which is a thin layer of white matter covering the
ventricular surface of the hippocampus and then converge to form the fimbria.
The fimbriae of the two sides increase in thickness and, on reaching the posterior end
of the hippocampus, arch forward above the thalamus and below the corpus callosum
to form the posterior columns of the fornix.
The two columns then come together in the midline to form the body of the fornix
The commissure of the fornix consists of transverse fibers that cross the midline from
one column to another just before the formation of the body of the fornix
The function of the commissure of the fornix is to connect the hippocampal formations
of the two sides.
Diencephalon
Figure 9-10: The diencephalon
The habenular commissure is a small bundle of nerve fibers that crosses the midline in the
superior part of the root of the pineal stalk
The commissure is associated with the habenular nuclei, which are situated on either
side of the midline in this region
The habenular nuclei receive many afferents from the amygdaloid nuclei and the
hippocampus
These afferent fibers pass to the habenular nuclei in the stria medullaris thalami
Some of the fibers cross the midline to reach the contralateral nucleus through the habenular
commissure
The function of the habenular nuclei and its connections in humans is unknown
Association fibers
Commissural fibers
Projection
Function of cerebral cortex
• Cerebral Cortex is:
– the outer layer of the cerebrum that
consists of gray matter which deals with
conscious motor action, sensation,
memory, communication, reasoning,
emotions, intelligence.
Functions of Cerebral lobes
• Frontal Lobe ----- controls conscious muscle action,
planning for movements, motor memory, voluntary
eye movements.
• Parietal Lobe ----- Controls conscious interpretation of
sensation from muscles, tongue and cutaneous areas.
• Temporal Lobe --- conscious interpretation of auditory
and olfactory sensations. Memory of sounds and smells.
• Occipital Lobe ------- the most posterior lobe of the
cerebrum which deals with conscious seeing, eye focus
and integrating visual memory with other sensations.
Insula (Island of Reil) (‘fifth lobe’)
 Covered by parietal and temporal lobes, not
visible from the outside within the lateral
fissure
 It is a component of a functional lobe which is
called limbic lobe
 Limbic lobe is related to emotional and
autonomic response to external stimuli
Cerebral cortex
• Sensory Area of the Cerebral Cortex –
– Located in areas posterior to the central sulcus.
Receives and interprets conscious sensory impulses.
The postcentral gyrus of the parietal lobe is a key
ridge of gray matter that allows a person to judge the
source of sensory stimuli.
• Motor Area of the Cerebral Cortex --– Located in areas anterior to the central sulcus. Plans
and initiates impulses for conscious motor
movements. The precentral gyrus of the frontal lobe is
an another key ridge of gray matter that allows a
person to operate specific areas of the body.
• Association Area of Cerebral cortex
Cytoarchitecture of cerebral cortex
Cytoarchitecture of cerebral
cortex
Cytoarchitecture of cerebral
cortex
Cytoarchitecture of cerebral
cortex
Cytostructure of cerebral
cortex
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•
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1 – Molecular layer
2 – External granular layer
3 – External pyramidal layer
4 - Internal granular layer
5 – Internal pyramidal layer
6 – Multiform layer
Cytoarichitecture of cerebral cortex based on
Brodmann divisioions
Brodmann area Location
Function
17
Banks of cal.sul Primary visual c
18, 19
3,1,2
Medial aspect
Secondary
of occipital lobe visual cortex
Postcentral gyr. primary somato.
4
Precentral gyr.
6
Sup&middle f.g. Premotore cort.
44,45
Inf. front. gyirus Speech
41,42
Sup. tem .gyr.
Primary motor
Auditory cortex
Function of Brain Structures Continued
• Sensory Area of the Cerebral Cortex
– Located in areas posterior to the central sulcus.
Receives and interprets conscious sensory impulses.
The postcentral gyrus of the parietal lobe is a key
ridge of gray matter that allows a person to judge the
source of sensory stimuli.
• Motor Area of the Cerebral Cortex
– Located in areas anterior to the central sulcus. Plans
and initiates impulses for conscious motor
movements. The precentral gyrus of the frontal lobe is
a another key ridge of gray matter that allows a
person to operate specific areas of the body.
Brain Structure Functions Continued
• Association Areas ----- Regions of the cerebral
cortex that analyze, recognize and act on
sensory input and communicate with the motor
areas. Examples include the visual and
auditory association areas.
Primary Motor Cortex
Somatic Sensory Cortex
Important areas in frontal cortex
• Supplamentary cortex = medial surface of area 6
(area 24 in cingulate gyrus)
• Prefrontal cortex = predominanatly area 9, 45 & 46
•
• Premotor area = area 6 (which is in front of area 4)
The localisation of language functions in the human brain
Speech
• Speech area normally in left cerebral cortex
– Wernicke’s area: Sensory speech
– Broca’s area: Motor speech
• Aphasia: Absent or defective speech or
language comprehension
– 1) Broca’s aphasia (expressive aphasia,
motor aphasia)
– 2) Wernicke’s aphasia (no comprehension &
failure to convey meaning
How to speak in response to seeing a word or hearing it.
Figure 9-23: Cerebral processing of spoken and visual language
Spinal tap
Brain Herniation Syndromes
Herniation occurs when mass effect is severe enough to push intracranial
structures from one compartment into another. The 3 most clinically
important herniation syndromes are caused by heriation through the tentorial
notch (transtentorial), centrally and downward (central), and under the falx
cerebri (subfalcine)