Autonomic Nervous System PDF

Presented by D/Suzan Moustafa Hazzaa Professor of medical physiology Menoufia university  Nervous system The human nervous system consists of the : 1- Central: Brain:(located in the cranial cavity. Spinal cord: (located in the vertebral cavity). Which...

Presented by D/Suzan Moustafa Hazzaa Professor of medical physiology Menoufia university  Nervous system The human nervous system consists of the : 1- Central: Brain:(located in the cranial cavity. Spinal cord: (located in the vertebral cavity). Which serve as the main control centers for all body activities.  Nervous system The human nervous system consists of the : 2- Peripheral: Composed of nerves derived from the brain and spinal cord Cranial nerves: (12 pairs). Spinal nerves: (31 pairs) (8 cervical, 12 thoracic, 5 lumber and 5 sacral). Which links between the CNS and body. Parts of the nervous system Central Nervous System (CNS) a) Brain: Cerebrum, cerebellum, brainstem. b)Spinal Cord: Pathway for information transmission between brain and body. Peripheral Nervous System (PNS) a) Somatic Nervous System: Voluntary control of skeletal muscles; sensory and motor nerves. b)Autonomic Nervous System (ANS): Involuntary control of organs and glands.  Difference between somatic and autonomic nervous system 6  The autonomic nervous system The autonomic nervous system is essential for maintaining homeostasis and responding to changes in the internal and external environment. It is formed of three divisions: a)Sympathetic Nervous System: “Fight or flight” response. b)Parasympathetic Nervous System: “Rest and digest” response. c)Enteric Nervous System: Controls gastrointestinal function. They work together to regulate vital involuntary functions, ensuring the body operates efficiently and adapts to varying conditions. Autonomic ganglia 11  Ganglia They are clusters of neuronal cell outside the CNS and are essentially a junction between autonomic nerves originating from the CNS (preganglionic neurons) and autonomic nerves innervating their target organs in the periphery (postganglionic neurons). The two main categories are: I. Sympathetic ganglia. II. Parasympathetic ganglia. According to their location the autonomic ganglia are: a) Lateral (paravertebral) ganglia. b) Collateral ganglia. c) Terminal ganglia.  1- Sympathetic chain (lateral=paravertebral ganglia) It is a series of ganglia located on either side of the vertebral column. It extends from the cervical to the sacral region. Function: it is responsible for synapse of preganglionic with postganglionic neurons of the sympathetic nervous system.  2- Collateral ganglia (prevertebral ganglia) They are located close to major abdominal arteries (e.g., celiac ganglion, superior mesenteric ganglion, inferior mesenteric ganglion). Function: Preganglionic fibers pass through collateral ganglia, synapse with postganglionic neurons that innervate abdominal and pelvic organs.  2- Terminal ganglia They are present on the wall of the effector organ, and it is specific for relay of preganglionic parasympathetic nervous system. Function: These ganglia serve as the site where; the short postganglionic fibers innervate the target tissues. Functions of autonomic ganglia 1- Relay station: at which the function of autonomic nervous system can be regulated. 2- Distributing center: each preganglionic nerve fiber relays with about 8-9 postganglionic neurons this is called divergence of signals. The autonomic nervous system 18 Autonomic nervous system o Sympathetic division: Prepares the body for stressful or emergency situations and is part of the fight-or-flight response. o Parasympathetic division: Functions in an opposite manner and is part of the rest-and- digest response.. Sympathetic nervous system 20  Origen: The sympathetic nervous system originates from the thoracolumbar region of the spinal cord (T1 to L2-L3). The preganglionic neurons arise in the spinal cord, synapse in the sympathetic chain or collateral ganglia The postganglionic neurons extend to various target organs. Functions The sympathetic nervous system prepares the body for stressful or emergency situations, often referred to as the "fight or flight" response. It increases alertness, metabolic rate, and physical activities by stimulating various physiological processes.  Effect of stimulation of sympathetic: 1. Heart: Increases heart rate and force of contraction. 2. Blood Vessels: Causes vasoconstriction in most blood vessels, increasing blood pressure. Redirects blood flow to skeletal muscles and decrease blood flow to the digestive system. 3. Lungs: Dilates bronchioles to increase airflow. 4. Metabolism: Stimulates glucose release from the liver for quick energy. 5. Adrenal Glands: Stimulates the release of adrenaline (epinephrine) and noradrenaline (norepinephrine). 6. Pupils: Dilates pupils to enhance vision. 7. Digestive System: Inhibits digestion and all digestive functions. The sympathetic division may be referred to as the “E division” (signifying exercise, emergency, and excitement). Sympathetic activation, controlled by the hypothalamus, Parasympathetic nervous system 24  Origen: (craniosacral) Cranial part involves the cranial nerves (oculomotor, facial, glossopharyngeal, and vagus nerves), which innervate head, thoracic, and upper abdominal organs. Sacral part involves pelvic splanchnic nerves, which innervate the lower abdominal and pelvic organs. Functions The parasympathetic nervous system promotes the "rest and digest" state, conserving energy and maintaining normal body functions during resting periods.  Effect of stimulation of parasympathetic: 1. Heart: Decreases heart rate and force of contraction. 2. Blood Vessels: causes vasodilation in certain areas in the body. 3. Lungs: Constricts bronchioles to decrease airflow. 4. Metabolism: Stimulates digestive activities and nutrient absorption. 5. Glands: Stimulates salivary, lacrimal (tear), and digestive glands. 6. Pupils: Constricts pupils to reduce light intake. 7. Digestive System: Stimulates digestion and peristalsis, promoting gastrointestinal activity. The parasympathetic division may be referred to as the “D division” (signifying digestion, defecation, and diuresis). Both divisions antagonize each other’s effects greatly to maintain homeostasis.  3-Enteric nervous system Functions It is a network of neurons and nerve networks in the digestive tract and is influenced by both the sympathetic and para-sympathetic divisions. Effect of stimulation of enteric nervous system 1. Gastrointestinal Motility: Regulates peristalsis and segmentation, controlling the movement of food through the digestive tract. 2. Secretion: Controls the secretion of digestive enzymes, acid, and other substances necessary for digestion. 3. Blood Flow: Regulates blood flow to the gut, ensuring adequate nutrient absorption and waste removal.  Interaction between divisions The sympathetic and parasympathetic nervous systems typically have a) opposite effects on target organs. For example: Heart Rate: Sympathetic stimulation increases heart rate, while parasympathetic stimulation decreases it. Digestive Activity: Sympathetic stimulation inhibits digestion, while parasympathetic stimulation promotes it. However, these divisions may also be b) independent, with only one of them innervating certain body structures. They also may c) work together, and each may control just one stage of a complicated series of actions.  Difference between sympathetic and parasympathetic nervous system 32 Thank you 35