Autonomic Nervous System PDF

Autonomic Nervous System Presented by: Dr. Yasmine Gamal Sabry Lecturer in the physiology department, faculty of medicine, Ain Shams university 1. Compare the difference between somatic and autonomic nervous system 2. Define the autonomic ganglia and mention its types...

Autonomic Nervous System Presented by: Dr. Yasmine Gamal Sabry Lecturer in the physiology department, faculty of medicine, Ain Shams university 1. Compare the difference between somatic and autonomic nervous system 2. Define the autonomic ganglia and mention its types and function 3. Differentiate between the divisions of the autonomic nervous system and the functions of each 4. Describe the difference between the cholinergic and adrenergic systems and the drugs affecting them 2  Nervous System Central Peripheral Brain Sensory Motor Spinal cord Somatic Autonomic 3 ❖ Both somatic and autonomic perform their functions through reflex action through reflex arc which is composed of: Receptor: receives stimulus Afferent (sensory) nerve: transmits impulses to CNS. Center: in the CNS Efferent (motor) nerve: transmits impulses out of CNS Effector organ: where response is initiated 4 ❖ The Reflex Arc Visceral reflex 5  The Somatic Nervous System It is concerned with control the VOLUNTARY actions as skeletal muscle contraction. 6 The Somatic Nervous System Role: Initiation (always excitatory), operating system Efferent neuron: One efferent neuron Neurotransmitter: Acetylcholine only. Autonomic ganglia: Absent Origin: Anterior horn cells (AHCs) of spinal cord Center: Cortex 7  The Autonomic Nervous System The autonomic nervous system is a part of the nervous system concerned with regulation and control of INVOLUNTARY processes in the body. Cardiac Muscles It controls Smooth Muscles Exocrine Glands 8  Sympathetic The Autonomic Nervous System Parasympathetic Role: Regulation (excitatory or Inhibitory) Efferent neuron: 2 efferent neuron (pre & post ganglionic) Neurotransmitter: Acetylcholine or norepinephrine. Autonomic ganglia: Present Origin: Lateral horn cells (LHCs) of spinal cord Center: Cerebral cortex, hypothalamus, brain stem, spinal cord 9  Autonomic Somatic Types 2 sympathetic & parasympathetic One type Efferent 2 efferent neuron One efferent neuron (pre & post ganglionic) Organ - Smooth, cardiac muscles and exocrine Skeletal muscles only gland Role Regulation (excitatory or Inhibitory) Initiation (always excitatory), operating system Neurotransmitters Acetylcholine o norepinephrine Acetylcholine only. Autonomic ganglia Present Absent Site Lateral horn cells (LHCs) of spinal cord Anterior horn cells (AHCs) of spinal cord Center Cerebral cortex, hypothalamus, brain Cerebral cortex stem, spinal cord 10 11 ❖ Autonomic Ganglia It is a collection of nerve cells outside the CNS. It act as: Site of relay, Distributing center and Site of action of drugs. 12  There are 4 types of autonomic ganglia Lateral Collateral Terminal Adrenal gland Terminal Ganglia Collateral Ganglia 13  1- Lateral ganglia = para-vertebral 2-Collateral ganglia = sympathetic chain - Form the - Sites of relay - Present in the - Sites of relay sympathetic of pre- abdomen, near of pre- chain on both ganglionic the big ganglionic sides of the sympathetic branches of fibers, mainly vertebral fibers only. the aorta. sympathetic. column. 14  3- Terminal ganglia 4- Adrenal glands - It is a modified sympathetic ganglion. - Sites of relay of - Present near pre-ganglionic - The nerve cells inside the adrenal or on the wall of para- medulla loose their axons and become effector organs. sympathetic changed into secretory cells. fibers only. - It secretes (nor-adrenaline & adrenaline) in blood to augment and prolong the sympathetic effects on body organs. 15 16  Divisions of the Autonomic Nervous System The ANS is composed of two anatomically and functionally distinct divisions: The Sympathetic System The Parasympathetic System. 17  Divisions of the Autonomic Nervous System Two important features of these divisions: -Tonic activity: continuous mild activity all the time. -Dual innervations : Both innervate most of the organs except: 5S (Skin, Sweat glands, Spleen, Skeletal muscle blood vessels and Supra- renal gland (adrenal gland)) , are supplied by sympathetic ONLY. The effects of the sympathetic & parasympathetic systems on the same organ usually antagonistic (opposite to each other) expect in salivary glands and genital organ. 18 19  Sympathetic versus Parasympathetic 20  Sympathetic Parasympathetic Catabolic system dominant in Anabolic system dominant in emergency stressful situation quiet relaxed situations sleeping (fight or flight) & eating. Distribution: Distribution: Cranio- → Generalized → Localized Origin: Origin: Thoraco-lumbar →Thoraco-lumbar → Cranio-sacral Sacral 21  Sympathetic Parasympathetic - Ganglia: - Ganglia: Lateral/ Collateral Terminal - Pre-ganglionic fiber: - Pre-ganglionic fiber: Short Long -Post-ganglionic fiber: -Post-ganglionic fiber: Long Short - Neurotransmitter: - Neurotransmitter: a) Autonomic ganglia: a) Autonomic ganglia: Acetylcholine Acetylcholine b) Post ganglionic fiber: b) Post ganglionic fiber : Norepinephrine Acetylcholine 22  Sympathetic Parasympathetic Sympathetic tone: Para-sympathetic tone: For the smooth muscles of Vagal tone on the heart: leading arterioles: leading to partial to decrease in the intrinsic high continuous degree of rhythm of the heart from 120 to vasoconstriction → help in 70−90 during rest → preserve maintenance of blood pressure. energy of the heart. Maintain glucose level GIT secretions 23  Sympathetic nervous system Effects on different body organs 1- Eye Pupil: Dilatation Eye adapted to: Far vision Widening of the eye Ciliary muscles relaxation, and lens becomes thinner 24 2- Salivary glands Secretion: Viscous secretion Blood vessels: Vasoconstriction 3- Skin Sweat glands: Secretion Hair: Erection Blood vessels: Vasoconstriction Note that: - Sympathetic causes VC of all blood vessels EXCEPT skeletal muscles Bl.vs (exercise) - Vasoconstriction leads to increased blood pressure 25 4- heart Increase: Heart Rate, Contractility, Cardiac Output 5- lungs Airways: Bronchodilatation Secretions: Decreased Blood vessels: Vasoconstriction 26 6- GIT Decrease: Motility ( Relaxation of the wall and contraction of the sphincters Secretions: Decreased 7- Liver and gall bladder Increase: Glycogenolysis, & Lipolysis Relaxation: Gall bladder wall Contraction: Gall bladder sphincter 27 8- Spleen - Contraction of the smooth muscle in splenic capsule –> Squeezes the stored blood into the circulation 9- Adrenal medulla Stimulates secretion of Epinephrine and norepinephrine → Augments and prolongs sympathetic action 28 10- Urinary bladder - Relaxation of the wall , & Contraction of the internal urethral sphincter → retention of urine 11- Rectum - Relaxation of the wall , & Contraction of the internal anal sphincter → retention of feces 29  Parasympathetic nervous system Effects on different body organs 1- Eye Pupil: Constriction Eye adapted to: Near vision Lacrimal glands: Tears secretion 30 2- Salivary glands Secretion: Watery secretion 3- Blood vessels Vasodilatation of all blood vessels → Decrease the blood pressure 31 4- heart Decrease: Heart Rate, Contractility, Cardiac Output # REMEMBER → Vagal Tone 5- lungs Airways: Bronchoconstriction Secretions: Increased Blood vessels: Vasodilatation 32 6- GIT Increase: Motility ( Contraction of the wall and relaxation of the sphincters) Secretions: Increased → Increase GIT motility and secretion (help digestion) 7- gall bladder Contraction: Gall bladder wall Relaxation: Bladder sphincter → Secretion of bile 33  8- Urinary bladder - Contraction of the wall , & Relaxation of the internal urethral sphincter → Urination 9- Rectum - Contraction of the wall , & Relaxation of the internal anal sphincter → Defecation 34 Organ Sympathetic Parasympathetic Eye Pupil dilatation Pupil constriction Far vision Near vision Widening of the eye Tears secretion Salivary glands Viscous secretion Watery secretion Skin Sweat secretion Not supplied Hair erection Blood vessels Vasoconstriction except skeletal Vasodilatation muscles bl. Vs. Blood pressure Increase Decrease Heart Increase heart rate, contractility Decrease heart rate, & cardiac output contractility & cardiac output Lungs Bronchodilatation Bronchoconstriction Decrease secretions Increase secretions 35 Organ Sympathetic Parasympathetic GIT Decrease motility & secretions Increase motility & secretions Liver ↑ Glycogenolysis and lipolysis Increase bile secretion Gall bladder Relaxation of the wall and Contraction of the wall and contraction of the sphincter relaxation of the sphincter Rectum Relaxation of the wall and Contraction of the wall and contraction of the sphincter relaxation of the sphincter Urinary bladder Relaxation of the wall and Contraction of the wall and contraction of the sphincter relaxation of the sphincter Spleen Squeeze stored blood into Not supplied circulation Adrenal medulla Secretion of adrenalin and nor- Not supplied adrenalin to augment and prolong sympathetic action 36 37  Transmission in the Autonomic Nervous System ❖Transmission of a nerve impulse, at the site of junctions, is chemically mediated i.e. by Neurotransmitters; as there is no direct contact between the neuronal membranes. - Chemical transmission in the ANS is needed at two sites: 1. The synaptic junction between pre and postganglionic neuron. 2. Between the postganglionic neurons and effector organs. - The principal transmitter agents involved are: acetylcholine (ACh) and nor-epinephrine (NE). 38  Cholinergic system It is the part of the nervous system that uses Acetyl choline as a neurotransmitter Cholinergic neurons: All pre-ganglionic neurons, whether sympathetic or para-sympathetic Pre-ganglionic neuron supplying adrenal medulla. All parasympathetic post-ganglionic neurons. Sympathetic post-ganglionic neurons to sweat glands & skeletal muscles blood vessels. Neuromuscular junction (Somatic). 39  Adrenergic system Adrenergic neurons: Most sympathetic post-ganglionic neurons release nor-epinephrine (NE). Adrenalin can be released only from adrenal medulla, as the enzyme needed to convert the nor-adrenalin into adrenalin only found in adrenal medulla. Adrenal medulla secretes mainly E (80%) & little amount NE (20%). 40 41