brain and its parts2

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Name the parts of brainName the parts of the brain. Describe briefly the external and

internal features of each part. Add a note on the blood supply of brain.

Explain the structure and functions of cerebellum

Draw the diagram of brain and name the parts

Name the parts of brain. Describe briefly about the internal capsule.

Write a short note on the blood supply of spinal cord.

Describe the structure and functions of nervous tissue

Write briefly on Neurologlial cells.

Write short note on Circulation of cerebrospinal fluid.

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The parts of the brain are:

• The cerebrum • Thalamus• Internal capsule• Basal nuclei• Hypothalamus• Midbrain• Pons varolii• Cerebellum • Medulla oblongata

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Coverings of the brain

• Duramater

• Arachnoid mater

• piamater

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Cerebrum has the following lobes:-

• frontal• parietal• temporal • occipital

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• 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

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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 hemispheresCommisural fibres – connecting one hemisphere to the other e.g. corpus callosumProjection fibres – which connect the cerebral cortex to grey matter of lower parts of the brain and the spinal cord e.g. the internal capsule

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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 of speech

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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

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Thalamus and infarcts

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Thalamic Haemorrhage

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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.

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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

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A section of the

cerebrum showing

some connecting nerve fibres

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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.

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• 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.

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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)

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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

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

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Go to Brain Stem

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