CEREBROSPINAL FLUID (CSF) AND BRAINSTEM -blogwriterjony

Definition : 

The cerebrospinal fluid (CSF) is a clear modified tissue fluid present in the ventricular system of the brain and in the subarachnoid space around the brain and spinal cord.

Composition of CSF :

1. Water.

2. Mineral salts.

3. Glucose.

4. Plasma proteins: small amount of albumin and globulin

5. Creatinine. 

6. Urea

7. A few leukocytes

Amount of CSF : About 150 ml.

Normal pressure of CSF : 60 to 100 mm of CSF (or water)

Formation of CSF :

The CSF is formed by the choroid plexuses of ventricle (lateral,3rd and 4th) of the brain, 

Circulation of CSF :

Lateral ventricle- interventricular foramen(of monro)

3rd ventricle-1. Central canal of spinal cord.

      2. Aqueduct of mid brain.

4 th ventricle - 1. Median and lateral apertures

2. Subarachnoid space around brain and spinal cord.

Function of CSF :

1. It supports and protects the brain and spinal cord.

2. It maintains a uniform pressure around these delicate structures. 

3. It acts as a cushion and shock absorber between the brain and the cranial bones. 

4. It keeps the brain and spinal cord moist and there may be interchange of substances between CSF and nerve cells, such as nutrients and waste products. 

BRAIN STEM :

 Definition :

The brain stem is the part of the brain that connects the spinal cord to the cerebrum and relays messages between the parts of the nervous system. 

Parts :

The brain stem consists of the midbrain, pons and medulla oblongata. 

Function :

The brain strm has three main functions :

1. It produces the rigid autonomic behavious necessary for survival, such as increasing the heart  rate and stimulating the adrenal medulla to produce adrenaline. 

2. It provides pathways for nerve fibres between higher and lower neural centres. 

3. It serves as the origin of 10 of the 12 pairs of cranial nerves. 

Midbrain :

1. The midbrain is the area of the brain situated around the cerebral aqueduct Between the cerebrum above and the pons below. 

2. It consists of nuclei and nerve fibres, which connect the cerebrum with lower parts of the brain and with the spinal cord. 

3. The midbrain is the reflex centre for cranial nerves three and four and mediates pupillary reflexes and eye movements. 

Pons :

1. The pons of the middle part of the brain stem, connecting the midbrain with the medulla oblongata. 

2. The pons is mainly composed of nerve fibres that from a bridge between the two hemispheres of the cerebrum,  and deep projection fibres passing Between higher brain centres and the spinal cord. 

3. There are nuclei within the pons which act as relay stations. Several cranial nerves issue from pons nuclei, including the trigeminal, the abducens and facial nerves. Other pons nuclei from the pneumotaxic and apnoustic centres, that are respiratory centres they act in conjunction with the respiratory centres in the medulla oblongata. 

Medulla oblongata :

1. The medulla oblongata is the lowest part of the brain  stem that joins the spinal cord at the level of the foramen magnum, an opening in the occipital portion of the skul.. 

2. The cranial nerves associated with medulla oblongata are : hypoglossal glossopharyngeal, vagus and portions of accessory nerves. 

3. The vital centres, consisting of groups of cells associated with autonomic reflex activity, lie in the deeper structure of the medulla are : - cardiovascular centre 

                   - Reflex centres of vomiting, coughing, sneezing and swallowing. 

CEREBELLUM:

1. The cerebellum is the second largest region of the brain. It lies behind the pons and medulla occupying the posterior cranial fossa. 

2. It has two hemispheres, separated by a narrow median strip called the vermis.

Functons : The cerebellum is concerned with the coordination of voluntary muscular movement, posture and balance.