Anatomy Nervous system 6.pdf

Presented by Dr. MOHAMMED ANWAR  The nervous system is a complex network of nerve cells that enables all parts of the body to function.  It includes: 1) Brain 2) Spinal cord 3) Several billion nerve fibers  The nervous system is well protected. The brain is pr...

Presented by Dr. MOHAMMED ANWAR  The nervous system is a complex network of nerve cells that enables all parts of the body to function.  It includes: 1) Brain 2) Spinal cord 3) Several billion nerve fibers  The nervous system is well protected. The brain is protected by the skull. The spinal cord is protected by the spinal canal in the vertebral column.  The nervous system is divided into two anatomic parts : ◦ Central nervous system ◦ Peripheral nervous system 1) Maintain homeostasis with electrical signals. 2) Provide for sensation. 3) Provide for higher mental functions and emotions. 4) Activate muscles and glands. Neurons are the cells considered to be the basic units of the nervous tissue the main part of a neuron is the cell body.The cell body contains the nucleus and most of the major organelles. The neuron have one axon—a fiber that emerges from the cell body and projects to target cells. Many axons are wrapped by an insulating substance called Myelin. The other processes of the neuron are Dendrites , which receive information from other neurons at specialized areas of contact called synapses. A ganglion is a group of neuron cell bodies connected together provide relay points and intermediary connections between different neurological structures in the body, such as the peripheral and central nervous systems.  Includes the brain and spinal cord ,They receive impulses, process the information, and respond with the appropriate action. Gray and white matter of the central nervous system The Gray matter of the brain and spinal cord consists of unmyelinated nerve fibers (cannot be regenerated if damaged) in the cortex or surface layer. The white matter makes up the internal structure, and consists of myelinated nerve fibers.  Protective coverings The entire CNS is contained within a protective framework : 1. The thick, bony structures of the skull and spinal canal withstand injury very well. 2. The Meninges:  outer layer (Dura mater) is a tough, fibrous layer that forms a sac to contain the CNS and Inner two layers (Arachnoid and Pia mater) contain the blood vessels.  Cerebral spinal fluid (CSF) ◦ Produced in a chamber inside the brain called the third ventricle. Approximately 125 to 150 mL of CSF in the brain at one time , primarily acts as a shock absorber.   The brain controls the body, and is also the center of consciousness and is divided into three major areas 1) Cerebrum 2) Cerebellum 3) Brain stem  The Cerebrum Controls a wide variety of activities, including most voluntary motor function and conscious thought, contains about 75% of the brain’s total volume divided into two hemispheres with four lobes in each hemisphere. The surface or cortex is arranged in bulging folds, each one called a Gyrus ,and furrows, each one called a Sulcus.  Parts of the cerebrum Each hemisphere is divided into 4 lobes that correspond to the overlying bones of the skull: 1. The frontal lobe specializes in motor activity, personality, and speech. 2. The parietal lobe specializes in language, temperature, pressure and touch. 3. The temporal lobe contains centers for hearing, smell, and language input. 4. The occipital lobe specializes in vision. The Cerebellum Is the second largest part of the brain. It contains nerve fibers that connect it to every part of the central nervous system. It coordinates voluntary and involuntary patterns of movements. It also adjusts muscles to automatically maintain posture.  The Brain stem Controls most functions necessary for life as breathing, swallowing, coughing, sneezing, vomiting, heartbeat, and blood pressure. It is the best-protected part of the CNS  At each segment of the spinal cord, left and right pairs of sensory and motor nerves branch out and connect to the peripheral nervous system. Impulses travel to the brain and back to the muscles or organ. Consists of : 1) 31 pairs of spinal nerves conduct impulses from the skin and other organs to the spinal cord, conduct motor impulses from the spinal cord to the muscles. 2) 12 pairs of cranial nerves , transmit information directly to or from the brain , perform special functions in the head and face, including sight, smell, taste, hearing, and facial expressions. Types of peripheral nerves 1) Sensory nerves  Carry only one type of information from the body to the brain via the spinal cord 2) Motor nerves  One for each muscle.  Carry information from the CNS to the muscles.  Connecting nerves ◦ Found only in the brain and spinal cord. ◦ Connect the sensory and motor nerves with short fibers. ◦ Allow the exchange of simple messages.  The autonomic nervous system is a part of the peripheral nervous system. It controls the involuntary body functions such as sweating, gland secretions, blood pressure, and the heart. It is divided into the sympathetic and parasympathetic The sympathetic nervous system is responsible for the ‘flight , fright or fight’ responses… increased alertness, metabolic rate, respiration, blood pressure, heart rate, and sweating. The parasympathetic nervous system counteracts the responses of the sympathetic system , restoring homeostasis.