The Cerebrum

• Is the largest part of the brain
• Controls all conscious thoughts and intellectual functions
• Processes somatic sensory and motor information
• Gray matter:
• in cerebral cortex and basal nuclei
• White matter:
• deep to cortex
• around basal nuclei

Structures of the Cerebrum

• Gyri of neural cortex: increase surface area (number of cortical neurons)
• Longitudinal fissure: separates cerebral hemispheres
• Lobes: divisions of hemispheres
• Central sulcus divides: anterior frontal lobe from posterior parietal lobe
• Lateral sulcus divides: frontal lobe from temporal lobe
• Parieto-occipital sulcus divides: parietal lobe from occipital lobe

3 Functional Principles of the Cerebrum

• Each cerebral hemisphere receives sensory information from, and sends motor commands to, the opposite side of body
• The 2 hemispheres have different functions although their structures are alike
• Correspondence between a specific function and a specific region of cerebral cortex is not precise

Lobes of the Cerebrum

Slide 7.29b

Figure 7.15a

The White Matter of the Cerebrum

The Cerebral Hemispheres

PLAY

3 Types of Axons in the Cerebrum

• Association fibers
• Connections within 1 hemisphere
• Commissural fibers
• Bands of fibers connecting 2 hemispheres
• Projection fibers
• Link cerebral cortex with diencephalon, brain stem, cerebellum, and spinal cord

What is The Internal Capsule?

• The internal capsule is an area of white matter in the brain that separates the caudate nucleus and the thalamus from the lenticular nucleus.
• The internal capsule contains both ascending and descending axons.
• It consists of axonal fibres that run between the cerebral cortex and the pyramids of the medulla

4. b. What are the named parts of the Internal Capsule?

• Anterior limb
• Posterior limb
• Genu
• Retrolentiform
• sublentiform

Parts of the Internal capsule

5. Explain, in detail, the fibre tracts found in each part of the Internal Capsule.

• The posterior limb of the internal capsule contains corticospinal fibers and sensory fibers from the body.
• The genu contains corticobulbar fibers, which run between the cortex and the brainstem.
• The anterior limb of the internal capsule contains:
• 1) frontopontine (corticofugal) fibers project from frontal cortex to pons;
• 2) thalamocortico fibers connect the medial and anterior nuclei of the thalamus to the frontal lobes.

Fibre Tracts

• The retrolenticular part contains fibers from the optic system, coming from the lateral geniculate nucleus of the thalamus. More posteriorly, this becomes the optic radiation. Some fibers from the medial geniculate nucleus (which carry auditory information) also pass in the retrolenticular internal capsule, but most are in the sublenticular part

Fibre tracts

What is the arterial supply of the Internal Capsule? (course of arteries)�

• The internal capsule is supplied by the anterior and middle cerebral arteries via their medial and lateral straite branches, respectively, and from the branches of the internal carotid, especially the anterior choroidal.
• The dorsal part of the posterior limb and genu is supplied by the lateral straite arteries from the middle cerebral.
• The ventral part is supplied by the anterior choroidal and small unnamed branches from the internal carotid.

• Internal capsule is supplied by the middle cerebral which is a branch of the internal carotid.
• Striate arteries come off middle cerebral and enter through the anterior perforated substance in the base of the brain.

Blood supply of the Internal Capsule

What would happen if this area were damaged?

• The anterior cerebral arteries supply blood to the medial cortex, including the medial aspects of the motor and sensory strips.
• Due to the upside-down representation of the homunculus in both of these area, a blockage in an anterior cerebral artery could cause paralysis or sensory deficits which affect the opposite side of the body from the hips on down.

• For example, a patient who has suffered such a blockage might have a paralyzed leg or be incontinent of bowel and/or bladder.
• Since the parts of the motor and sensory strips connected to the arm receive some blood from the anterior cerebral artery, the arm may also be somewhat affected by this kind of blockage.

​

• Finally, apraxia of gait may also occur if an anterior cerebral artery fails to supply an adequate amount of blood to the medial part of the motor strip.
• The anterior cerebral arteries also supply blood to the anterior aspects of the frontal lobes.
• As these areas are involved in higher level cognition such as reasoning and judgment, a condition called cerebral dementia may result from anterior cerebral artery blockages.
• Confused language, or a language indicative of cognitive impairment, may also occur.

• the middle cerebral arteries supply blood to the cortical areas involved in speech, language and swallowing. The left middle cerebral artery provides Broca's area, Wernicke's area, Heschl's gyrus, and the angular gyrus with blood.
• Also, the "head" and "neck" areas of the motor and sensory strips in both hemispheres receive their blood supply from the middle cerebral arteries.
• Damage to these cortical areas on either side of the brain can impair motor speech and swallowing functions.�

Basal Nuclei

• Are masses of gray matter embedded in white matter of cerebrum
• Direct subconscious activities
• Are involved with:
• the subconscious control of skeletal muscle tone
• the coordination of learned movement patterns (walking, lifting)

• Caudate nucleus:
• Lentiform nucleus:
• globus pallidus
• putamen

Ventricles

• Lateral ventricles
• Deep w/in cerebrum
• Third ventricle
• Connected by interventricular foramen (Monro)
• Fourth ventricle
• Connected by cerebral aqueduct (Sylvius)
• Connects to subarachnoid space to return to bloodstream

Ventricles of the Brain

Animation: Brain Dissections (see tutorial)