Autonomic Nervous System PDF

AUTONOMIC NERVOUS SYSTEM Dr.Ayesha Fatima Department of Anatomy CMHS,AGU. OBJECTIVES At the end of the session, students should be able to:  List the subdivisions of the nervous system  Define the autonomic nervous system.  Describe the structure of autonomic nervous system  E...

AUTONOMIC NERVOUS SYSTEM Dr.Ayesha Fatima Department of Anatomy CMHS,AGU. OBJECTIVES At the end of the session, students should be able to:  List the subdivisions of the nervous system  Define the autonomic nervous system.  Describe the structure of autonomic nervous system  Enumerate in brief the main effects of sympathetic & parasympathetic system Dr. Ayesha F  Nervous system Enables the body to react to continuous changes in its external & internal environment. Controls and integrates the various activities of the body.  Classification of Nervous system Central Nervous - Brain System(CNS) - Spinal Cord Nervous System - Cranial Nerves(12pairs) Peripheral Nervous -Spinal nerves(31 System(PNS) pairs) - Ganglia Dr. Ayesha F CADAVERIC IMAGE OF BRAIN,SPINAL CORD AND PERIPHERAL NERVES. Dr. Ayesha F  Parts of the brain - Midbrain Spinal cord - Pons - Medulla oblongata PARTS OF PARTS OF CEREBRUM(Cerebral BRAIN hemisphere) Dr. Ayesha F.  CRANIUM VERTEBRAL s located in the cranial cavity protected by cranium. COLUMN cord is located in the vertebral column. and spinal cord are surrounded by protective covering called Meninges(Duramater, Arachnoid mater, and and spinal cord are surrounded by CSF fluid located in the sub arachnoid space.  Cells in the nervous system Neuro glial cells(Supporting cells, Neurons (receive and eg: oligodendrocytes, transmit signals to astrocytes, microglia, different parts of body) ependymal cells, schwann cells, satellite cells) Dr. Ayesha F  Peripheral Nervous System Peripheral nerves can be sensory, motor or mixed. PNS includes 12 pairs of cranial nerves and 31 pairs of spinal nerves. Cranial nerves: Spinal nerve:  31 pairs of spinal nerves (8 cervical, 12 thoracic, 5  All the 12 pairs of cranial nerves arise from the lumbar,5 sacral, 1 coccygeal nerves). brain except the 11th cranial nerve which arises  All exit the vertebral column through intervertebral from the brain and spinal cord.  All cranial nerves exit the cranial cavity through foramina. foramina in the cranium. Dr. Ayesha F Structure of Spinal nerve Dr. Ayesha F  Classification of peripheral nervous system Central Nervous System(CNS)- Brain &Spinal Nervous cord Peripheral system Nervous PERIPHERAL System(PNS)- NERVOUS nervous SYSTEM structures outside CNS SENSORY MOTOR SOMATIC VISCERAL VISCERAL (0R) SOMATIC AUTONOMIC NERVOUS Voluntary Action SYSTEM On Skeletal Involuntary action on smooth Muscles muscles,glands,cardiac muscles. SYMPATHETIC PARASYMPATH NERVOUS ETIC NERVOUS SYSTEM SYSTEM Fight And Rest And Flight Digest Dr. Ayesha F  Autonomic Nervous System  The part of the PNS responsible for regulating involuntary body functions, such as heartbeat, blood flow, breathing, urination,digestion and reproductive function.  An autonomic nerve pathway involves two nerve cells(neurons). Preganglionic neuron with cell body located in the brain stem or spinal cord. Postganglionic neuron, with cell body located in an autonomic ganglion. Schematic diagram of ANS Dr. Ayesha F  CHARACTERISTICS SOMATIC NERVOUS SYSTEM AUTONOMIC NERVOUS SYSTEM 1. Sensory neuron(afferent pathway) Somatic senses & special senses Mainly located in blood vessel, visceral organ. 2. Effector Skeletal muscle Smooth muscles, cardiac muscles and glands 3. Control of motor neuron and effect Voluntary control, excitatory effect Involuntary control, excitatory or inhibitory effect 4. Motor Neuron (efferent pathway) and One motor axon from CNS to effector. First motor axon from CNS to autonomic neurotransmitter NT is Acetyl choline ganglion(preganglionic nerve) Second motor axon from autonomic ganglion to effector(postganglionic nerve) NT can be acetyl choline or norepinephrine Dr. Ayesha F Subdivision of Autonomic nervous system: ANS has two sub systems: SYMPATHETIC NERVOUS SYSTEM: Prepares body to function under stress(exercise, excitement, emergencies) Triggers Fight or flight response Prepares the body for intense muscle activity PARASYMPATHETIC NERVOUS SYSTEM Maintenance functions Triggers Rest-and-digest response Counter-balances sympathetic Both divisions operate in conjunction with one another (have antagonistic control over the function viscera) to Dr. Ayesha F Dr. Ayesha F  Sympathetic Nervous System Also called THORACOLUMBAR system Cell bodies of preganglionic neurons are in lateral horn of gray matter of spinal cord from T1-L2 (L3) Cell bodies of postganglionic neurons occur in two locations: Paravertebral and prevertebral ganglia. Paravertebral ganglia: either side of the vertebral column form sympathetic trunks(chains) Prevertebral ganglia: located in plexus that surround the origins of main branches of abdominal aorta. Preganglionic fibers are short and myelinated. Post-ganglionic fibers are long and non-myelinated. Dr. Ayesha F ganglia of sympathetic nervous system Dr. Ayesha F  Sympathetic Nervous System(continued) Course of preganglionic fibres: they take one of the three courses 1. Remain at same level: Synapse with postganglionic neuron of paravertebral ganglia. 2. Ascend or descend within sympathetic trunk, ascend synapse with a paravertebral postganglionic Splanchnic nerve neuron, 3. No synapse: pass through paravertebral No remain ganglion without synapse,form splanchnic synpase nerve. synapse in prevertebral ganglion Postganglionic axons follow arteries to descend reach the Abdomino pelvic organs Dr. Ayesha F  Adrenal gland is an exception Preganglionic sympathetic fibres do not synapse in prevertebral ganglia and terminate directly in the cells of adrenal medulla. These cells acts as modified postganglionic neurons and release the NT(epinephrine/nor epinephrine) directly into the blood vessels. widespread sympathetic response.(adrenaline “surge” in emergency) Dr. Ayesha F Sympathetic nervous system(Continue) Via spinal nerves and periarterial plexuses,post synaptic sympathetic fibres reach almost all parts of the body including sweat glands,arector pili muscle and viscera except avascular tissue like nails and cartilage. Examples of sympathetic effect:  when nervous, you sweat;  when afraid, hair stands on end;  when excited blood pressure rises (vasoconstriction): these are sympathetic only  dry mouth,  Dilated pupils,  increased heart & respiratory rates to increase O2 to skeletal muscles,  liver to release glucose Dr. Ayesha F  PARASYMPATHETIC NERVOUS SYSTEM Also called CRANIOSACRAL system Location of preganglionic neurons: Cranial site: cranial nerve nuclei of brainstem, exit CNS within CN III(occulolotor n.),CN VII(Facial n.),CN IX (glossopharyngeal n.) and CN X(Vagus n.) Sacral site: gray matter of spinal cord from (S2-S4) exit through anterior roots of spinal nerves and form pelvic splanchnic nerves. Dr. Ayesha F Parasympathetic System (continued) Location of postganglionic neurons: Cranial site: 4 parasympathetic ganglia (Ciliary ganglion, Pterygopalatine ganglion, Submandibular ganglion and Otic ganglion) Other parts of body: individually in (or)on the wall of target organ. Preganglionic fibres are long and myelinated. Post ganglionic fibres are short and non myelinated. Dr. Ayesha F Parasympathetic System distribution and function Localized distribution. Cranial outflow III {Oculomotor} - pupils constrict VII {Facial} - tears, nasal mucus, saliva IX {Glossopharyngeal} – parotid salivary gland X (Vagus) – visceral organs of thorax & abdomen: Stimulates digestive glands Increases motility of smooth muscle of digestive tract Decreases heart rate Causes bronchial constriction Sacral outflow (S2-4): form pelvic splanchnic nerves Supply 2nd half of large intestine Contracts the bladder,relaxes sphincter urination Supply all the pelvic (genitourinary) organscauses erection  AUTONOMIC PLEXUSES A network of sympathetic and parasympathetic axons. Cardiac plexus- heart. Cardiac plexus Pulmonary plexus- the bronchial tree. Celiac plexus- largest. Supplies the stomach, spleen, pancreas, liver, gallbladder, and adrenal medullae. Superior mesenteric plexus- small intestine and proximal colon. Inferior mesenteric plexus- distal colon and rectum. Hypogastric plexus- urinary bladder and genital organs. Renal plexus- kidneys and ureters. Dr. Ayesha F Central control of the Amygdala: main limbic region for emotions Autonomic NS -Stimulates sympathetic activity, especially previously learned fear- related behavior -Can be voluntary when decide to recall frightful experience - cerebral cortex acts through amygdala -Some people can regulate some autonomic activities by gaining extraordinary control over their emotions Hypothalamus: main integration center Reticular formation: most direct influence over autonomic function 25 Dr. Ayesha F Structural differences between Sympathetic and Parasympathetic Systems Dr. Ayesha F Dr. Ayesha F