DIENCEPHALON

This part of brain connects the cerebrum to the midbrain. It consist of several structures around the third ventricle; which includes thalamus, hypothalamus. Pineal gland and optic chiasma are also present.

1. THALAMUS:- The thalamus consist of two masses of grey matter and white matter within the cerebral hemisphere below the corpus callosum; one on each side of third ventricle. sensory impulses from the skin and viscera, related to pain, touch, temp etc reaches the thalamus for recognition; only basic recognition occurs at thalamus, as for refined perception, other parts of brain are also required. It is also involved in the processing of some emotions and complex reflexes. It relays and redistributes the nerve impulses to most parts of brain and cerebral cortex.

1. HYPOTHALAMUS:- it is a small structure of about 7g. it consist of no. of nuclei; it is situated below and in front of the thalamus. The hypothalamus is linked to the posterior lobe of the pituitary gland by the nerve fibers; and to the anterior lobe by the network of blood vessels. Through these connections, it controls the output of the hormones of both the lobes. Functions of hypothalamus include control of:- ANS, body temp, sleeping and walking cycle, sexual behaviour etc.

 BRAIN STEM

the brain stem consist of 4 parts:-

• MIDBRAIN:- the midbrain is area of brain which lies around the cerebral aqueduct; between the cerebrum above and the pons below. It consist of nuclei and cerebral tracts. The nuclei acts as relay stations for ascending and descending nerve fibers. It plays important role in auditory and visual reflexes.
• PONS:- it is situated in front of cerebellum, below the midbrain and above medulla oblongata. It mainly consist of nerve fibers that forms a bridge between the two hemispheres of the cerebellum and the fibers passing between the higher levels of brain and spinal cord. The nuclei act as relay stations and some are involved in cranial nerves. It also facilitates the control of respiration along with medulla oblongata.
• MEDULLA OBLONGATA:- It is the interior part of the brain stem, which extends from the pons above and is continuous with the spinal cord below. It is about 2.5cm long and lies above the foramen magnum. Its outer portion is white matter, which passes between the brain and spinal cord; and the central portion contains the grey matter.

The vital centers which consist of group of cell bodies are associated with the autonomic reflexes. These centers are: cardiovascular center, respiratory center, reflex center of vomiting, coughing, sneezing etc. Features of medulla includes:-

1. cardiovascular center(CVC)- This area controls rate and force of contraction, blood pressure, diameter of the blood vessels etc. the area receives impulses from baroreceptors, chemoreceptors etc.
2. respiratory center- this area controls the rate and depth of respiration. It works in coordination with the pnuemotaxic and apnuestic centers of pons.
3. reflex centers-  presence of irritants within the digestive and respiratory tract stimulate the reflex centers. these centers than respond in form of vomiting, coughing sneezing etc.

• Reticular Formation:-  It is a collection of neurons in the core of brain stem. It has a vast number of synaptic links with other parts of brain and therefor constantly receives information and transmit to ascending and descending tracts. Its functions include:- coordination of skeletal system, control of ANS, it selectively permit the passage of impulses to and from cerebral cortex.

CEREBELLUM

It is situated behind the pons and below the posterior portion of cerebrum. It has two hemispheres which are separated by narrow strip known as vermis. The grey matter forms the surface of cerebellum and white matter lies deeply.

Cerebellum is associated with the voluntary muscle movement, body posture and balance. The cerebral activity is not under voluntary control. sensory input is received from muscles, joints, eyes and ears. The proprioceptor input is derived from the muscles which indicate their position, eyes and semicircular canal provide info about position of head in space. Cerebellum than integrates this info to regulate the skeletal muscle activity.  It also facilitates learning and language processing. Damage to cerebellum results in uncoordinated muscle movement which leads to inability  to carry out smooth, steady and precise movements.

Multiple choice questions(MCQs)

1. The brain is divided in how many parts?
A. 3 B. 4
C. 5 D. 2

2. What is the function of diencephalon?
A. connects cerebrum and midbrain B. connects cerebrum and cerebellum
C. connect cerebellum and pons D. connect pons and midbrain

3. what is the function of midbrain?
A. visual reflex B. smell reflex
C. auditory reflex D. both A and c

4. Where is the cerebellum located?
A. above the pons B. behind the pons
C. in front of pons D. behind midbrain

5. Match the following-
a. thalamus 1. Located in the interior part of brain stem
b. hypothalamus 2. Lies below midbrain
c. pons 3. Linked with the lobes of pituitary gland
d. medulla oblongata 4. Involved in complex reflexes

6. Which of the following is a feature of medulla oblongata?
A. cardiovascular center B. respiratory centers
C. reflex centers D. all of the above

7. Which part of brain works along with pons for the control of respiration?
A. midbrain B. thalamus
C. medulla oblongata D. hypothalamus

8. Which of the following statement is true?
A. brain is located in the cranial cavity
B. medulla is the superior part of brain stem
c. cerebellum is involved in involuntary control
D. reticular formation is a collection of nerves in the core of brainstem

9. Sensory impulses from skin reaches which part of brain first?
A. thalamus B. hypothalamus
C. pons D. cerebellum

10. Which of the following is a part of diencephalon?
A. pons B. medulla oblongata
C. midbrain D. none of the above

ANSWERS:-

1. 4
2. connects cerebrum and midbrain
3. Both A and C
4. behind the pons
5. a – 4 b – 3 c – 2 d – 1
6. all of the above
7. medulla oblongata
8. brain is located in the cranial cavity
9. thalamus
10. none of the above

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REFERENCE:

1. Ross and Wilson-Anatomy and physiology in health and illness; 12th edition; page no.-:158-160 .
2. Gerard J. Tortora -Principles of anatomy and physiology; edition twelfth ; page no.-:503-513 .

The post Parts of BRAIN: Diencephalon, Brain Stem and Cerebellum and MCQs For NEET, GPAT, Pharmacist, Staff Nurse Exam appeared first on Gpatindia: Pharmacy Jobs, Admissions, Scholarships, Conference,Grants, Exam Alerts.

The brain is a large organ which lies in the cranial cavity. The average weight of brain is 1.4 kg. It is divided in 4 parts: cerebrum, brain stem, diencephalon and cerebellum.

CEREBRUM

Cerebrum is the largest part of the brain. It lies in the anterior and middle cranial fossae. Cerebrum is divided by a deep cleft known as  longitudinal cerebral fissure into right and left cerebral hemispheres.  Each of the hemisphere contains one lateral ventricle. Deep inside the brain, these hemispheres are connected by a white matter mass known as corpus callosum. Falx cerebri is formed by the dura mater ; separates two hemispheres and  which leads to the  corpus callosum.

The superficial part of cerebrum is composed of cell bodies and is known as cerebral cortex. Deep layers consist of nerve fibers and white matter. The cerebral cortex contains various infoldings and furrows. The found areas of the folds are known as gyri(convolutions). These gyri are separated by sulcus(fissures). The gyri increases the surface area of the cerebrum.

Each hemisphere of cerebrum is divided in different lobes. These lobes are named according to the bone where they lie; like: frontal, parietal, occipital and temporal. the boundries of these lobes are made by the fissures and are named as:- central, lateral and parieto-occipital sulcus.

CEREBRAL TRACTS:- Within the cerebrum, the lobes are connected by the mass of nerve fibers known as cerebral tracts. These tracts makes the white matter of the brain. The afferent and efferent fibers (tracts) which links the different part of brain are:-

• association tracts:- numerous in number, connects different parts of cerebral hemispheres
• Commissural tracts:- connects the corresponding areas of the two cerebral hemispheres.
• Projection tracts:- connects the cerebral cortex with the grey matter of lower parts of the brain and with spinal cord. for eg- internal capsule.

The internal capsule is an important projection tract which lies within the brain between the basal ganglia and the thalamus. The fibers that form the internal capsule carries many nerve impulses to and from the cerebral cortex. Motor fibers within the capsule form the pyramidal tracts which crosses the medulla oblongata and are main pathway for skeletal muscles.

BASAL GANGLIA:- these are the group of cell bodies that lie within the brain and are the pat of extrapyramidal tract . These are the relay stations having connection to many parts of the brain. Their main functions include: initiation and control of complex movements and coordinated activities.

Functions of cerebral cortex:- the three main types of activities associated with cerebral cortex include

1. higher order functions: mental activities involved in memory, sense of responsibility, thinking reasoning etc.
2. sensory perceptions: includes perception of pain, temp, touch, sight , hearing etc.
3. initiation and control of skeletal muscle contraction and voluntary movement.

Functional areas of cerebral cortex:- the main functional areas of cerebral cortex are involved exclusively only in on function each. The areas of cortex which lies anterior to the central sulcus are involved in motor functions; an those lying posterior to the central sulcus are associated with sensory functions.

• Motor areas of cerebral cortex are as follows:- 

1. Primary motor area:– it lies in the frontal lobe anterior to the central sulcus. they control the skeletal muscle activity.

2. Motor speech (broca’s) area:– it lies in the frontal sulcus, above the lateral sulcus. It controls muscle movements for speech.

• Sensory areas of cerebral cortex are as follows:-

1. Somatosensory area:– it lies behind the central sulcus. These areas receives sensations of pain, touch, awareness of muscular movement and position of joints.

2. Auditory area:– lies below the lateral sulcus within the temporal lobe. This area receives and interpret the signals transmitted from the inner ear by cochlea, vestibule and semicircular canals.

3. Olfactory area:- lies within the temporal lobe. it receives impulses from the nose.

4. Taste area:– lies above the lateral sulcus in the deep layers of the somatosensory area. Here impulses are received from the taste buds.

5. Visual area:– lies behind the parieto-occipital sulcus and includes greater part of occipital lobe.

• Association areas are connected to each other and other areas of cerebral cortex by the cerebral tracts. these are as follows:–

1.  Premotor area:– lies in the frontal lobe. the neurons here facilitates movement initiated by the primary motor area.

2. Prefrontal areas:– these extends from the premotor area to include the remaining part of frontal lobe. They control intellectual functions.

3. Sensory speech areas:- this is situated in the temporal lobe . Here the spoken word is perceived, and comprehension and intelligence are based.

4. Parieto-occipitotemporal area:– lies behind the somatosensory area and includes most of parietal lobe. Its functions are: spatial awareness, interpreting written language and the ability to name objects.

Multiple choice questions(MCQs)

1. Which is the largest part of the brain?
A. medulla oblongata B. cerebrum
C. cerebellum D. thalamus

2. What divides the cerebrum into right and left cerebral hemispheres?
A. gyri B. central sulcus
C. longitudinal fissure D. none of the above

3. What is the function of gyri?
A. increases the surface area of cerebrum
B. decreases the surface area of cerebrum
C. increases the surface area of cerebellum
D. decreases the surface area of cerebellum

4. Match the following-
A. association tracts 1. Lies above lateral sulcus
B. commissural tracts 2. Lies within temporal lobe
C. olfactory area 3. Connects different parts of cerebral hemisphere
D. taste area 4. Connects corresponding area of cerebral hemisphere

5. What is the work of commissural tract?
A. connects different parts of cerebral hemisphere
B. connects different areas of 2 cerebral hemisphere
C. connects cerebral cortex with grey matter of other parts of brain
D. connects cerebral cortex with white matter of other parts of brain

6. What is the function of cerebral cortex?
A. sense of responsibility B. hearing
C. movements of skeletal muscles D. all of the above

7. Where is the taste area situated?
A. above the lateral sulcus B. below the lateral sulcus
C. behind lateral sulcus D. in front of lateral sulcus

8. Which of the following statement is NOT true?
A. cerebrum is largest part of brain
B. Falx cerebri is formed by pia matter
C. the superficial part of cerebrum is formed by cell bodies
D. each hemisphere contain one lateral ventricle

9. What is the function of associated areas?
A. connects each other B. connects to the areas of cortex
C. movements of muscle D. both A and B

10. Which area of cerebral cortex facilitates intellectual functions?
A. premotor areas B. somatosensory area
C. parieto-occipitotemporal area D. none of the above

ANSWERS:-

1. cerebrum
2. longitudinal fissure
3. increases the surface area
4. a – 3 b – 4 c – 2 d – 1
5. connects different areas of 2 cerebral hemispheres
6. all of the above
7. above the lateral sulcus
8. falx cerebri is formed by pia matter
9. both A and B
10. none of the above

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REFERENCE:

1. Ross and Wilson-Anatomy and physiology in health and illness; 12th edition; page no.-:

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