NERVOUS SYSTEM

(CENTRAL NERVOUS SYSTEM)

(THE BRAIN)

THE BRAIN:

• An enlarged, convoluted and highly developed rostral portion of the CNS.
• In young adults, it averages about 1, 400 grams in weight, which is 2% of the total body weight.

SUBDIVISIONS OF THE BRAIN:

1. CEREBRUM
2. DIENCEPHALON
3. BRAINSTEM
4. CEREBELLUM

I. CEREBRUM: - Makes up the largest portion of the brain

      CEREBRAL HEMISPHERES - 2 mirror-image halves of the cerebrum.

      CORPUS CALLOSUM - connects the 2 cerebral hemispheres.

        LOBES OF THE BRAIN: seen on the lateral surface of the hemisphere.

       1. FRONTAL LOBE - largest of the lobes of the brain

           The Primary Motor Cortex - responsible for contralateral voluntary motor activity

           Motor Association Area (Premotor Cortex) and Prefrontal Cortex

• Integrate movement information with other sensory inputs to generate perception (interpretation) of stimuli.

       2.  TEMPORAL LOBE - lies inferior to the Lateral Fissure of Sylvius

            Primary Auditory Cortex and Auditory Association Area

• Receive and process signals from the auditory nerve and integrates them with other sensory inputs.
• Other portions of the temporal lobe are involved in olfaction (smell) and in mediating short-term memory storage and recall.

      3. PARIETAL LOBE - extends from behind the central sulcus to the parieto - occipital sulcus and laterally to the level of the lateral fissure.

          Somatosensory Cortex - receives input from the major sense organs

          Sensory Association Areas - integrates sensory information with other association areas of the cortex to form meaningful perceptions.

          Somatosensory Homunculus - topographical representation of the body on the surface of the cortex.

      4. OCCIPITAL LOBE - the pyramid-shaped posterior lobe situated behind the parieto-occipital

          sulcus.

• Area of the cerebral cortex responsible for vision.

          Primary Visual Cortex - receives input directly from the optic nerve

          Visual Association Area - further processes visual information and integrates it with other sensory        inputs.

• Language and Mathematical Area
• Most often located in the (L) Hemisphere
• Serves as a general interpretive center, enabling a person to understand visual and auditory information and in turn to generate written and spoken responses.
• CORPUS CALLOSUM - a dense number of nerve fibers that serves as a pathway and connection between the 2 cerebral hemispheres
• This connection allows the brain to integrate sensory and motor information from both sides of the body and to coordinate whole - body movement and function.

PROSENCEPHALON:aka Endbrain - primitive term for the CEREBRAL HEMISPHERES

Differentiates into: TELENCEPHALON and DIENCEPHALON

II. DIENCEPHALON:

         2 MAJOR AREAS:

1. THALAMUS - receives sensory input as it travels from the spinal cord, and integrates sensory information before sending it to the cortex.
2. HYPOTHALAMUS - controls a variety of endocrine functions (body Temperature, thirst, food intake, etc.) mainly through directing the release of hormones.

          Important parts of the hypothalamus to be remembered:

          a. Supraoptic and Paraventricular Nuclei

          b. Preoptic Area and Anterior Hypothalamic Area

          c. Ventromedial Nuleus

          d. Lateral Hypothalamic Area

          OTHER AREAS:

1. SUBTHALAMUS -
2. EPITHALAMUS -

III. BRAINSTEM -

PARTS:

              1. MIDBRAIN/ MESENCEPHALON - bridges the lower brainstem with the diencephalon above.

• Primary function is controlling eye movements, and it also exerts control over the auditory and visual motor reflexes.

              2. PONS - Primary function is to act as relay station for transferring information between the cerebral cortex and the cerebellum.

• Along with the centers in the medulla, the pons also coordinates and controls breathing.

              3. MEDULLA OBLONGATA - the portion of the brainstem that has a primary control over involuntary functions such as breathing, BP, and swallowing.

• It is also where fibers from the corticospinal tract, which originate in the motor cortex, cross over to the opposite side of the spinal cord to innervate muscles on the opposite side of the body.

IV. CEREBELLUM - means, "little brain," which is only partly accurate.

• Contains more neurons than the rest of the brain combined.
• It receives input from the somatic receptors, receptors for equilibrium and balance, and motor neurons from the cortex.
• Processes sensory information and coordinates the execution of movement in the body.

• In effect it contributes in the generation of accurate limb movements, correct ongoing movements, and modifies the strength of some reflexes.
• It is also involved with classical Pavlovian conditioning.

To my students: This is only a general outline. There is much that will be discussed and presented in lecture that is not included in this outline. All material discussed in lecture is test-material whether or not it is included in this outline. Mr. D.K. Mangusan Jr., PTRP

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