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Nervous System note- Brain notes for CTEVT HA 2nd year

Nervous System note- Brain notes for CTEVT HA 2nd year


Nervous System note- Brain notes for CTEVT HA 2nd year. If you are searching the notes of HA 2nd year notes related to brain this is for you. Happy learning and earning in the future. 

Brain:

The brain of an adult is 1.5 kg. It lies in the cranial cavity. 
The parts of the brain are:
  1. Cerebrum
  2. Midbrain
  3. Pons
  4. Medulla oBlongata
  5. Cerebellum
Midbrain, pons and medulla are combinedly known as the brain stem.  


Cerebrum:

It is a large part of the brain and lies in the anterior and middle cranial fossa. 
It consists of right and left separated by a longitudinal cerebral fissure. Interiorly hemispheres are connected by the corpus callosum.
The superficial part of the cerebrum is composed of nerve cell bodies or grey matter forming cerebral cortex and deeper layer consists of nerve fibres or white matter.
The cerebral cortex shows many infoldings called gyri and sulci. The exposed areas are called gyri and those are separated by sulci(fissure).
Four lobes of the cerebrum are: frontal, temporal, parietal and occipital. Central sulcus  divides frontal and parietal lobe, lateral sulcus divides frontal and temporal lobe and parieto-occipital sulcus separates parietal and occipital lobe. 

The function of the cerebrum: (CTEVT)
a. frontal lobe:
-initiates voluntary muscle contraction
- Responses related to personality, memory, emotions, reasoning, judgment, planning and verbal communication

b. parietal lobe:
- responds to somatosthetic stimuli (cutaneous and muscular sensations)
-understanding speech and formulating words to express thoughts and emotions.
-interpretation of texture and shape of objects.
c. temporal lobe:
-interpretation of auditory sensations
-stores visual and auditory experiences

d. parietal lobe:
-integration of moments in focusing the eye
-visual recognition of objects
-correlation of visual images with previous visual experiences and other stimuli 

Functional areas of the cerebrum:
The human brain is divided into more than 44 areas called Brodmann's areas. Three types of areas are present:

a. motor area:
-primary motor area: it initiates muscular contraction, the right side of brain control movement of the left side of the body.
- Broca's area: it controls movements for speech, it is dominant in the left hemisphere in right-handed person and vice-versa. 
HA 2nd year anatomy note
b.Sensory area:
  • -Somatosensory area: pain, temperature, touch, pressure, joint position and movement sense
  • -Auditory area: receives sound transmitted from the inner ear
  • -Olfactory area: a sense of smell
  • -Taste area: a sense of taste
  • -Visual area: visual sensation
c. Association area:
  • -premotor area: coordinate movement initiated in the primary motor cortex, ensuring the learned pattern
  • of movements can be repeated
  • -prefrontal area; perception and comprehension of the passage of time, management of emotions
  • -Wernicke’s area: perceives the spoken word 
  • -parieto-occipito-temporal area: interpretation of written language, ability to name objects
BASAL GANGLIA:
The basal nuclei (basal ganglia) are specialized paired groups of related neuron bodies located deep
within the white matter of the cerebrum.
They consist of the corpus striatum. The corpus striatum consists of the caudate nucleus and the
lentiform nucleus. The lentiform nucleus, in turn, consists of the putamen and the globus pallidus.
Function: It is involved in the initiation and fine control of complex movements and learned coordinated
activities. If control is inadequate the movements are jerky, clumsy and uncoordinated.
 
THALAMUS:
The thalamus is a large ovoid mass of grey matter.
It is a paired organ, with each portion located immediately below the corpus callosum on each side of
lateral ventricles.

Functions:
  • -The sensory input from skin, viscera and special sense organs is relayed to thalamus before redistribution to the cerebrum.
  • - It is involved in memory and emotional reactions.

HYPOTHALAMUS:
It is situated below the thalamus and just above the pituitary gland. It is linked to the pituitary gland.
 
Functions of the hypothalamus: 
  1. Control of hormonal secretions 
  2. Autonomic nervous system 
  3. Appetite and satiety 
  4. Thirst and water balance 
  5. Body temperature 
  6. Emotional reaction 
  7. Sexual behaviour
  8. Biological clock or circadian rhythm

MIDBRAIN:

It is situated around cerebral aqueduct between cerebrum above and pons below.
The midbrain also contains the corpora quadrigemina, the cerebral peduncles, the red nucleus, tectum, medial lemniscus and the substantia nigra.
 
Functions: The nuclei of midbrain act as a relay station for ascending and descending fibers.
Nuclei here act as the origin of cranial nerves.
 

PONS:

It is situated in front of the cerebellum between midbrain and medulla oblongata.
It consists of nerve fibers that form a bridge between two hemispheres.
The anterior portion of the pons is called ventral pons and the posterior portion is called dorsal pons.
Functions: The nuclei here act as a relay station and associated with the origin of cranial nerves.
The pneumotaxic and apneustic centers are located here which controls respiration.
 

MEDULLA OBLONGATA:

It is located between pons above and spinal cord below. It lies just within cranium above the foramen
magnum.
Anterior surface bears a pair of club-like ridges called pyramids. Lateral to the pyramid is olive.
Vital centers are located here.
Functions of medulla:
  1. It acts as decussation centre for most of the motor fibers descending from the cerebrum.
  2. Some of the sensory fibers also cross here.
  3. The cardiovascular centre controls the rate and force of cardiac contraction.
  4. The respiratory centre controls the rate and depth of respiration.
  5. The vasomotor centre controls the diameter of the blood vessels, especially the small arteries and arterioles which have a large proportion of smooth muscle fibers in their walls.
  6. Reflex centres. Reflex centers of cough, vomiting, sneezing and swallowing are located here..


CEREBELLUM:

The cerebellum is situated behind the pons and immediately below the posterior portion of the
cerebrum occupying the posterior cranial fossa.
It is the second-largest part of the brain. The cerebellum is separated by cerebrum by folds of dura mater
called tentorium cerebelli.
It consists of the following parts:

a) two large cerebellar hemispheres 
b) midline portion called the vermis 
c) two small flocculonodular lobes.
It is connected to the brain stem by superior, middle and inferior cerebellar peduncles.
 

Functions: -It is mainly concerned with the coordination of voluntary muscle movement.
 
  • It maintains posture, balance and equilibrium.
  • It receives sensory impulses from receptors in muscles, tendons, and joints (proprioceptors) and from special sense organs, such as the eyes and ears.
  • It communicates with other parts of CNS by tracts.

VENTRICLES OF BRAIN:
Within the brain, there are four irregular-shaped cavities, or ventricles, containing cerebrospinal fluid.
They are:
  • right and left lateral ventricles
  • third ventricle
  • fourth ventricle.
Each of the two lateral ventricles (right and left ventricles) is located in one of the hemispheres of
the cerebrum, inferior to the corpus callosum.
The third ventricle is located in between the thalami. Each lateral ventricle is connected to the third
ventricle by a narrow, oval opening called the interventricular foramen (foramen of Monro).
The fourth ventricle is located in the brain stem between the pons and cerebellum. The
mesencephalic aqueduct (cerebral aqueduct) passes through the midbrain to link the third and
fourth ventricles.

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