Nervous System Lecture 1 PDF

The Nervous System It is the maestro for all body functions, being responsible for sensations, mental activity, control of muscles, body viscera and glands. It is mainly composed of brain, spinal cord, peripheral nerves and sensory receptors. It is involved...

The Nervous System It is the maestro for all body functions, being responsible for sensations, mental activity, control of muscles, body viscera and glands. It is mainly composed of brain, spinal cord, peripheral nerves and sensory receptors. It is involved in almost all body functions. Gamal Abdelhady  Functions of the Nervous System 1. Sensory input: both at conscious (e.g. pain) and subconscious (e.g. blood pressure) levels. This is carried out through sensory receptors. 2. Integration of sensory input to initiate response. 3. Control of muscles activity, viscera and gland’s secretion in response to the integration process Gamal Abdelhady  Parts and Organization of the Nervous system Central nervous system (CNS): which consists of brain and spinal cord. Peripheral nervous system (PNS): consists of cranial nerves (from the brain) and spinal nerves (from the spinal cord). Cells of the nervous system are called neurons Gamal Abdelhady  Divisions of the Nervous System The Central Nervous System (CNS) includes the brain and spinal cord enclosed in bony cases (Skull and Vertebral Column).  Divisions of the Nervous System The Peripheral Nervous System (PNS) is all the nervous tissue outside of the brain and spinal cord. Gamal Abdelhady  Divisions of the Nervous System The output of the PNS is divided into two systems: The somatic nervous system (SNS) controls skeletal muscle (Muscles under voluntary control). The autonomic nervous system (ANS) regulates involuntary smooth and cardiac muscle, as well as glands. The sympathetic division includes “fight or flight” responses. The parasympathetic division includes “rest and digest” responses. Gamal Abdelhady  CENTRAL Brain and NERVOUS spinal SYSTEM cord Afferent Efferent Division Division PERIPHERAL NERVOUS SYSTEM Somatic Autonomic nervous nervous system system Parasympathetic Sympathetic division division Smooth muscle Somatic Visceral Skeletal Cardiac muscle muscle sensory sensory receptors receptors Glands Gamal Abdelhady  Cellular Components of Nervous System Neuron: is the functional unit of nervous system and has the ability to generate and transmit impulses. Consists of: Cell body (soma): contains the nucleus (perikaryon) and other cellular organelles Processes: 1. Can be myelinated (if surrounded by myelin sheath) or unmyelinated. 2. Dendrites (to receive input) and an axon (to convey the impulse Supporting cells (neuroglia): as the name denotes, they support and “serve” the neurons, but they do not have the ability to generate or conduct impulses. Gamal Abdelhady  Serves and supports the neurons (structurally) Blood brain barrier Myelination in the CNS In the PNS we have Schwan cells Protection of the NS Cerebrospinal fluid (CSF) secretion Gamal Abdelhady  Organization of the CNS The cell bodies of the neurons gather through the CNS and form a rather dark layer of cell bodies called Grey Matter. The axons of the same cells form the White Matter of the Nervous System In the brain, grey matter is towards the outside and white matter to the inside and opposite in the spinal cord Gamal Abdelhady Gamal Abdelhady Gamal Abdelhady Overview of the Nervous System Gamal Abdelhady  Brain Occupies the upper most part of the nervous system Is the part enclosed in the cranial cavity of the skull. It consists of the cerebrum, brainstem, cerebellum Gamal Abdelhady  Brain The cerebrum is the main part of the brain. It is divided into right and left hemispheres by the longitudinal fissure. It has many folds (gyri) and grooves (sulci). Gamal Abdelhady Brain Anatomy Gamal Abdelhady  Brain Each hemisphere is divided into Anatomical lobes: frontal, parietal, temporal and occipital. The outer surface of the cerebrum is the cerebral cortex formed of grey matter while the inner surface is called medulla formed of white matter Functionally the brain is divided into motor areas and sensory areas Gamal Abdelhady  Parietal Frontal lobe lobe Occipital Temporal lobe lobe Gamal Abdelhady  Brain Stem The brain stem consists of: medulla oblongata, pons and midbrain. It connects the spinal cord and cerebellum to the rest of the brain. 10 of the 12 cranial nerves originate from the brain stem. Damage to small area of the brain stem can cause death. Gamal Abdelhady Diencephalon Mid Brain Pons Medulla Oblongata Gamal Abdelhady  Cerebellum The Cerebellum (little brain): Is attached to the posterior of the brain stem. Its function is to control planning, learning and practicing complex movements. It also controls balance and eye movements. Gamal Abdelhady Gamal Abdelhady  Meninges of the Brain and Spinal Cord The brain and the spinal cord are surrounded by connective tissue membranes called meninges. From outward to inwards they are: dura matter, arachnoid, and pia matter. Gamal Abdelhady  Meninges of the Brain and Spinal Cord Dura Mater - a tough, fibrous outer most layer Arachnoid - Middle Layer - contains blood vessels. Pia Mater - loose tissue that covers the brain Gamal Abdelhady Gamal Abdelhady Brain Meninges Gamal Abdelhady Meninges of the Brain and Spinal Cord Gamal Abdelhady Gamal Abdelhady Gamal Abdelhady Gamal Abdelhady  Blood Supply of the Brain The blood supply of the brain receives 20% of the cardiac out put. The requires high blood supply to perform its normal function. The brain depends on blood glucose for its energy supply as brain cells cannot store high energy molecules. Gamal Abdelhady  Blood Supply of the Brain The brain is supplied by 2 arterial systems: 1. A Carotid system for the anterior half of the brain 2. A Vertebro-Basilar system to the posterior half of the brain Gamal Abdelhady Gamal Abdelhady Ventricular System Gamal Abdelhady Gamal Abdelhady  Peripheral Nervous System Nerves are either motor nerves or sensory nerves. Efferent or motor nerves innervate muscles and glands. Afferent or sensory nerves send sensory information and nerve impulses from sensory receptors in the skin, muscles, and joints to the brain. Gamal Abdelhady  Cranial Nerves The Cranial nerves are 12 pairs of nerves, mostly from the head and neck, that attach directly to the brain. Bypass the spinal cord. Part of the autonomic nervous system. Gamal Abdelhady  Cranial Nerves Cranial Nerves – 12 pairs of cranial nerves which are either sensory or motor nerves. 10 of these nerves originate at the brain stem. Cranial Nerve 1: Olfactory – smell Cranial Nerve 2: Optic – vision Cranial Nerve 3,4&6: Oculomotor, trochlear, and abducent – motor nerves controlling movement of the eyes. Gamal Abdelhady  Cranial Nerves Cranial Nerve 5: Trigeminal – sensation of the head, face, and movements of the jaw Cranial Nerve 7: Facial – taste, facial movements, and secretions of tears and saliva Cranial Nerve 8: Vestibulocochlear – hearing and equilibrium Cranial Nerve 9: Glossopharyngeal – taste, sensation and movement in the pharynx, and secretion of salivaGamal Abdelhady  Cranial Nerves Cranial Nerve 10: Vagus – controls taste, and movements in the pharynx and larynx Cranial Nerve 11: Spinal accessory – movements of the pharynx, larynx, head, and shoulders Cranial Nerve 12: Hypoglossal – movement of the tongue Gamal Abdelhady  Spinal Cord Is the major link between the brain and the PNS (spinal nerves). It participate in the integration of incoming information and production of response through reflex mechanisms. It starts at the end of the brain stem and ends at L1-2 (lumber vertebra). 31 pairs of spinal nerves originates from the spinal cord. Gamal Abdelhady Gamal Abdelhady  Peripheral Nervous System Spinal Nerves – there are 31 pairs of spinal nerves branching off the spinal cord. 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal Gamal Abdelhady  Spinal Cord It is covered by meninges. It is divided into right and left halves. Centrally located grey matter takes a butterfly shape while the periphery is made up of white matter. Each half is organized into columns that is made up of ascending or descending tracts. Gamal Abdelhady Cross Section at the Spinal Cord Relation ship between the sensory and motor neurons in the spinal cord. Gamal Abdelhady  Ganglia Ganglia: Ganglia related to the cranial nerves: They host the cell bodies of the sensory neurons of the cranial nerves and they lie within the skull. Spinal (dorsal root) ganglia: Contains the cell bodies of the sensory neurons receiving information from the body to the CNS (spinal cord). Autonomic ganglia: are either: Sympathetic : paravertebral or prevertebral Parasympathetic: close to the target organ Gamal Abdelhady Gamal Abdelhady  Autonomic Nervous System (ANS) The autonomic or involuntary nervous system is that portion of the nervous system which regulates the activity of cardiac muscle, smooth muscle, and the glands. The ANS has two parts: Sympathetic Parasympathetic Gamal Abdelhady  Autonomic Nervous System Controls the involuntary function of the internal body organs. Controlled by higher centers in the brain Is divided into sympathetic and parasympathetic nervous systems Gamal Abdelhady  Autonomic Nervous System Each system of the two consists of two sets of neurons and ganglia at which the two neurons synapse. The cell body of the first neuron is found in the CNS while the cell body of the second is located in peripheral ganglia. The first neuron is called preganglionic neuron The second is called postganglionic neuron Gamal Abdelhady Gamal Abdelhady  Autonomic Nervous System (ANS) Sympathetic Prepares the body for emergency situations (“fight, fright or flight” response to stress) Fear, emergency, physical exertion, and embarrassment are responded to by this system This system shifts energy and blood toward the skeletal muscles, cardiac muscles, and respiration Gamal Abdelhady  Autonomic Nervous System (ANS) Parasympathetic Energy conservation system Restores body energy during rest Responses toward digestion, elimination of waste, and decreases heart rate Gamal Abdelhady Segmental Spinal nerve Gamal Abdelhady Gamal Abdelhady  Segmental Spinal nerve During a somatic reflex, nerve signals travel along the following pathway: Somatic receptors in the skin, muscles and tendons Afferent nerve fibers carry signals from the somatic receptors to the posterior horn of the spinal cord or to the brainstem Gamal Abdelhady  Segmental Spinal nerve An integrating center, the point at which the neurons that compose the gray matter of the spinal cord or brainstem synapse Efferent nerve fibers carry motor nerve signals to muscles Effector muscle innervated by the efferent nerve fiber carries out the response. Gamal Abdelhady