OVER VIEW OF CENTRAL NERVOUS SYSTEM (CNS) Dr.Mohammed Sharique Ahmed Quadri Assistant prof. Physiology Al Maarefa College

Central Nervous System CNS consists of brain and spinal cord –100 billion neurons in brain Enables you to: –Subconsciously regulate your internal environment by neural means –Experience emotions –Voluntarily control your movements –Be consciously aware of your own body and your surroundings –Engage in other higher cognitive processes such as thought and memory

Brain Anatomy Brain components Forebrain a) Cerebrum i) Cerebral cortex ii) Basal nuclei b) Diencephalon i) Thalamus ii) Hypothalamus Brain stem - Mid brain - Pons - Medulla Cerebellum

CEREBRUM Cerebrum constitutes 80% of total brain weight. Outer layer, i.e. cerebral cortex of cerebrum is highly convoluted. It has gyri [ridges] and sulci [depression]. 5

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Basal Nuclei Basal Nuclei are present deep in the cerebrum. Functions: - Co-ordination of movements - Muscle tone regulation 7

Diencephalon Diencephalon is present in the interior of cerebrum. It has 2 components: - Thalamus - Hypothalamus  Thalamus All sensory information passes. Crude awareness of sensation.  Hypothalamus Regulates body temperature, has thirst and food intake center. 8

Brain Stem Brain Stem [mid brain, Pons, Medulla]. Brain Stem is continuous below with spinal cord.  Functions: Majority of cranial nerves originate from brain stem. Control Center for cardiovascular, respiratory system. Regulation of postural reflexes. Role in sleep – wake cycle. 9

Cerebellum Cerebellum is attached at the back portion of brain stem.  Functions: Balance of body. Muscle tone. Co-ordination and planning of skilled movements e.g. dance. 10

CEREBRUM Cerebrum is the largest portion human brain. It is divided into TWO halves, Right and Left cerebral hemispheres. They are connected by CORPUS CALLOSUM which consists of about 300 million axons connecting two cerebral hemispheres. Cerebral cortex– It is the outer shell of Gray matter covering the inner white matter. 11

Chapter 5 The Central Nervous System Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

CEREBRUM (cont)  Q—What is the GRAY Matter ? A– It is the Cerebral cortex, which consists of cell bodies and their dendrites, as well as connective tissue glial cells.  Q– What is the WHITE Matter ? A– It is the myelinated nerve fibers (Axons). Its white appearance is due to Myelin sheath (lipid layer). 13

CEREBRAL CORTEX NOTE – Gray matter of cerebral cortex is like computers of CNS. White matter is like wires that connect the computers to each other. 15

CEREBRAL HEMISPHERE Each cerebral hemisphere is divided into FOUR LOBES. 1) Frontal lobe 2) Parietal lobe 3) Temporal lobe 4) Occipital lobe 16

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LOBES OF BRAIN Central Sulcus separates the Frontal and Parietal lobe.  Frontal Lobe It is located at the front and at the top. It has MOTOR CORTEX area in the PRE - CENTRAL GYRUS- which controls the motor activity. Motor speech area. Elaboration of Thought. 18

LOBES OF BRAIN  Parietal lobe It is located posterior to the central sulcus. It has sensory cortex at post central gyrus.  Temporal Lobe Located laterally [on the sides of head]. It has auditory cortex. 19

LOBES OF BRAIN  Occipital Lobe Located posteriorly [back of head]. It has visual cortex ( center). 20

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Primary Motor Cortex Primary Motor Cortex is located in the pre- central gyrus in the frontal lobe. Motor Cortex controls the moments of opposite side of the body. Motor tracts originating from the right motor cortex cross to the opposite side at medulla and then go down to spinal cord to terminate on efferent motor neuron. 22

Primary Motor Cortex In motor cortex, presentation is not equal but some parts e.g. fingers, thumbs, muscles of speech [lips, tongue have more presentation due to fine degree of motor work]. Trunk, arms, lower limbs have less presentation than their size as they do not perform complex movements. 23

Primary Motor Cortex  Applied clinical aspect Damage to the right motor cortex will produce paralysis [loss of power] on the left side of the body. Damage to the left motor cortex will produce paralysis on the right side of the body. 25

Somato Sensory Cortex Somato Sensory Cortex is present in the post central gyrus in the parietal lobe. All body parts are not represented equally, but some areas have more representation due to their degree of fine work and have more receptors e.g. fingers [hand], face, tongue. 26

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Somato Sensory Cortex Right side sensory cortex gets sensory input [information] from left side of the body. Left side sensory cortex gets sensory input from the right side of the body.  Why? Because sensory pathways carrying the information cross to the opposite side of the body before they terminate in the sensory cortex. 28

Somato Sensory Cortex  Applied clinical Aspect Damage to the sensory cortex in the left hemisphere [left side] produces sensory deficit on the right side of the body. Damage to the sensory cortex in right hemisphere produces sensory deficit on the left side of the body. 29

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References Human physiology by Lauralee Sherwood, seventh edition Text book physiology by Guyton &Hall,11 th edition Text book of physiology by Linda.s contanzo,third edition 31