Brain And Its Parts2

Parts of the brain

Write short note on Circulation of cerebrospinal fluid. Write briefly on Neurologlial cells. Describe the structure and functions of nervous tissue Write a short note on the blood supply of spinal cord. Name the parts of brain. Describe briefly about the internal capsule. Draw the diagram of brain and name the parts Explain the structure and functions of cerebellum Name the parts of brain Name the parts of the brain. Describe briefly the external and internal features of each part. Add a note on the blood supply of brain.

The parts of the brain are:
The cerebrum
Thalamus
Internal capsule
Basal nuclei
Hypothalamus
Midbrain
Pons varolii
Cerebellum
Medulla oblongata

Coverings of the brain
Duramater
Arachnoid mater
piamater

Cerebrum has the following lobes:-
frontal
parietal
temporal
occipital

The ridges in the cerebrum are called the gyri (gyrus)
The grooves are called the sulci (sulcus)
The ridge in front of the central sulcus is called the precentral gyrus
The one behind the central sulcus is called the post-central gyrus

Interior of the cerebrum
Cerebral cortex is composed of nerve cell bodies on the surface – grey matter
Inside the cerebrum are the nerve fibres (tracts) which connect the various lobes – white matter
The afferent and efferent fibres linking the different parts of the brain and spinal cord are:- Arcuate fibres – interconnecting fibres between the different lobes of the same hemispheres Commisural fibres – connecting one hemisphere to the other e.g. corpus callosum Projection fibres – which connect the cerebral cortex to grey matter of lower parts of the brain and the spinal cord e.g. the internal capsule

Functions and functional areas of cerebrum
Precentral (motor) area – initiates the contraction of the voluntary muscles
Premotor area – manual dexterity
Lower part of premotor area – speech (motor) ( Broca’s area )
Frontal area or pole – behaviour , character , intellectual trait
Postcentral area (sensory) – pain , temperature , pressure , touch , knowledge of muscular movements and the position of joints
Parietal area – knowledge of objects (e.g.touch and recognise)
Sensory speech area – situated in the lower part of the parietal lobe and part of the temporal lobe – perception o f speech

Thalamus
The thalamus consists of two masses of nerve cells and fibres situated withing he cerebral hemispheres just below the corpus callosum one on each side of the third ventricle
This region contains a cluster of nuclei
Most of the sensory inputs are conducted to the cerebral cortex through the thalamus
Axons carrying auditory, visual and other sensory informations synapse with specific nuclei of this region
This region may also influence mood and general body movements due to strong emotions such as fear or anger

Thalamus and infarcts

Thalamic Haemorrhage

Hypothalamus
Hypothalamus – The master control of the autonomic nervous system, parasympathetic and sympathetic. This system stimulates and controls structures such as the heart, most glands and smooth muscles. In effect, this system allows your systems to excite and relax, as needed. This system integrates the autonomic and endocrine functions with behavior.
Hippocampus – This area of the brain, apart from its other functions, is primarily responsible for short term memory.

Hypothalamus
This region contains small nuclei and nerve tracts
The nuclei called mammillary bodies are involved in olfactory reflexes and emotional response to odours
The funnel shaped infundibulu from the hypothalamus connects to the posterior pituitary or neurohypophysis
This region controls the secretions of pituitary gland
The hypothalamus receives inputs from several sensory systems such as tongue,nose and external genitalia.
It is associatedwith emotional and mood relationships
It provides a relaxed feeling

A section of the cerebrum showing some connecting nerve fibres

Basal Ganglia
This area of grey matter lies deep within the cerebral hemispheres
Consist of the caudate nucleus , putamen and globus pallidus .
They are functionally important for controlling voluntary movements and establishing postures .
It influences skeletal muscle tone
When they are altered - say in disorders like Huntington disease or Wilson disease - the person has unwanted movements, such as involuntary jerking movements of an arm or leg or spasmodic movement of facial muscles.

The caudate nucleus and putamen along with the interposed anterior limb of the internal capsule are collectively known as the corpus striatum (i.e. striated body) because of their appearance.
Similarly, the shape of the putamen and globus pallidus resembles a lens, and they are collectively called the lenticular nucleus .

Internal Capsule
Consists of projection fibres – fibres connecting the cerebral cortex with the lower parts of the brain and the spinal cord
Lies deep within the brain
Between the basal ganglia and the thalamus
All the impulses passing to and from the cerebral cortex are carried by the fibres in the internal capsule
The motor fibres within the internal capsule form the pyramidal tracts (otherwise called the corticospinal tracts) The pyramidal fibres cross to the other side at the level of the medulla oblongata (called decussation )

A section of the cerebrum showing some connecting nerve fibres

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The midbrain
Situated around the cerebral aqueduct between the cerebrum and pons varolii
Consists of nerve cells and nerve fibres connecting the cerebrum with lower parts of the brain and with the spinal cord
The nerve cells serve as relay stations for the ascending and descending fibres
The roof of this region contains four nuclei
The nuclei form mounds
They are collectively called corpora quadrigemina
It is formed of two superior colliculi and two inferior
The superior colliculi are involved in visual reflexes
They control eye and head movements
They aid in visual tracking of moving objects
The inferior colliculi are involved in hearing

Hippocampus – This area of the brain, apart from its other functions, is primarily responsible for short term memory.

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Brain And Its Parts2

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