Pathophysiology II Autonomic Nervous System PDF

Pathophysiology II Autonomic Nervous System  Nervous System Central Nervous Peripheral Nervous System System Brain Spinal Somatic Autonomic Nervous Nervous C...

Pathophysiology II Autonomic Nervous System  Nervous System Central Nervous Peripheral Nervous System System Brain Spinal Somatic Autonomic Nervous Nervous Cord System System Sympathet ic Parasympath etic  Autonomic Nervous System  The ANS functions at the subconscious level and is involved in regulating, adjusting and coordinating vital visceral functions such as blood pressure and flow.  The ANS has two divisions: the sympathetic and parasympathetic systems. They are generally viewed as having opposite and antagonistic actions.  The sympathetic system functions in maintaining vital functions and responding when there is a critical threat to the integrity of the individual the (fight-or-flight) response.  The parasympathetic nervous system is concerned with conservation of energy and maintenance of organ function during periods of minimal activity.  The outflow of both divisions of the ANS consists of a two– neuron pathway:  Sympathetic nervous system -The sympathetic nerve fibers originate in the spinal cord between cord segments T1 & L2, and pass first into the sympathetic chain, then to the tissues and organs that are stimulated by the sympathetic nerves. - It is divided into 4 divisions: 1 Cervical division 2 Cardiopulmonary division. 3 Splanchnic division (greater splanchnic & lesser splanchnic nerves) 4 Somatic division. Parasympathetic nervous system The parasympathetic fibers leave the central nervous system through cranial nerves III, VII, IX & X. Additional parasympathetic fibers leave to thespinal 4th sacral lowermost nervespart & of the& spinal cord through occasionally thenerves. 1st sacral 2nd 4th  Sympathetic Parasympat receptors hetic receptors eye Radial Circular muscles: α 1 muscle: M3 Ciliary Ciliary muscle: β 2 muscle: M3 Lacrimal glands α1 M3 Salivary glands M3 M3 Heart 1 cardiac muscle: β 1 1 Atria: M2 2 SAN & AVN: β 1 2 SAN & AVN: M2 3 coronary vessels: β 3 Coronary: M3 2 Lung 1- Bronchi: β 2 1 Bronchi: M3 3- blood vessels: α 12Secretory cells: M3 3- Blood vessels: M3 GIT 1 Smooth muscles β 2 1- smooth 2 sphincters α 1 muscles M3 2- spincters M2 3- secretory  Sympathetic Parasympat Nervous hetic System Nervous System Adrenal Nn _ medulla Ureters & Wall Smooth Wall Smooth muscles β 2 and muscles M3 and urinary the sphincters α 1 the sphincters M2 bladder Blood vessels the skin BVs α 1 Skin blood vessels ---- GIT & internal organs GIT & internal organs BV α 1 BV M3 the skeletal blood vessels ---- the skeletal blood vessels β 2  Sympathetic Parasympat Nervous hetic System Nervous System eye Pupil dilation Pupil constriction (mydriasis) (miosis). Accomodation to Accomodation to far vision near vision Lacrimal glands Decrease secretion Increase secretion Salivary glands Thick secretion Watery secretion Heart 1- Increase heart rate 1- Decrease heart rate and and all cardiac all cardiac properties. 2- VD properties 2- VC of coronary of coronary vessels vessels. Lung 1 Bronchodilation 1 Bronchoconstriction 2Decrease 2Increase secretion 3- VC secretion 3- of vessels. VD of vessels. GIT 1- Relaxation of 1 Contraction of  Sympathetic Parasympat Nervous hetic System Nervous System Adrenal Increase _ epinephrine medulla secretion. Ureters & Relaxation of the Contraction of the wall and constriction wall and dilation of urinary of the sphincters the sphincters bladder Blood vessels VC of the skin VD of blood vessels. BVs and VD of the skeletal blood vessels.  Horner′s Cause: Syndrome injury of the cervical division of cervical sympathetic nerve fibers. It produces symptoms that appear on the same side which include: 1 Ptosis → dropping of upper eyelid due to paralysis of superior tarsal muscle. 2 Miosis→Pupilloconstriction due to paralysis of dilator pupillae muscle. 3 Anhydrosis → no sweat secretion. 4 Enophthalmos → due to paralysis of Muller′s muscle. 5 VD → due to loss of the sympathetic VC effect. The  The Parasympathetic The parasympathetic nervous system consists of the cranial & N.S sacral outflow. A- The cranial parasympathetic outflow: Includes 3, 7, 9, 10 cranial nerves. I- The oculomotor (3rd cranial) nerve: It supplies the following structures in the eye causing: Miosis → due to contraction of the pupilloconstrictor muscle. Increase the power of the eye lens → which is important for accommodation of the eye to II- The facial (7th cranial) nerve: It supplies: Submandibular & sublingual salivary glands. Anterior ⅔ of the tongue. Mucosa of soft palate & the nasopharynx. Lacrimal glands. It produces the following effects: VD of blood vessels & increase secretion from these glands which is large in amount and diluted (true secretion). III- The glossopharyngeal (9thcranial) nerve: It supplies: Parotid gland. Posterior ⅓ of the tongue. To produced → VD of blood vessels & increase IV- The vagus (10th cranial) nerve: - They constitute the main fibers of the parasympathetic in the body. - They supply the following organs in the chest & abdomen: a- The heart: Decrease all properties of the cardiac muscle → decrease heart rate. VC of the coronaries. b- The lungs: Bronchoconstriction. Mucus secretion from the bronchial glands. VD of pulmonary vessels. c- Gastrointestinal tract (GIT): Contraction of the walls of esophagus, stomach, small intestine & proximal part of large intestine, and relaxation of their corresponding sphincters, with increase secretion of these parts of GIT (nerve of B- The sacral parasympathetic outflow (sacral autonomic nerve): It is called sacral part because it arises from 2nd, 3rd & 4th sacral segments. The postganglionic fibers supply the following organs: 1 Urinary bladder: It induces micturition due to contraction of the detrusor muscle & relaxation of the internal urethral sphincter. 2 Rectum & distal part of the descending colon: It induces defecation due to contraction of the wall of the rectum & distal part of the descending colon and relaxation of internal anal sphincter. 3 The erectile tissues (penis in males & clitoris in females):  Autonomic receptors I- Cholinergic receptors:  These receptors are cell membrane receptors that respond to Ach.  They are two types according to their response to particular drugs: 1 Nicotinic receptors. 2 Muscarinic receptors.  Sites of nicotinic receptors: 1- Autonomic ganglia. 2- Motor end plate. 3- Cells of adrenal medulla. 4- CNS.  Sites of Muscarinic receptors: 1- Effector organs receiving parasympathetic postganglionic fibers. 2- Effector organs receiving sympathetic postganglionic cholinergic fibers as sweat glands and skeletal muscle blood vessels. - The drug atropine is an antimuscarinic or muscarinic cholinergic- blocking drug that prevents the action of acetylcholine at receptor sites.  II- Adrenergic -receptors: These receptors present in the membranes of effector organs. - These receptors are stimulated by different catecholamines as: Epinephrine. Norepinephrine Dopamine  Types: α1 receptors → in vascular smooth muscles → pupillary radial muscles ß → ß1 in cardiac muscle. → gut & bladder sphincters. recepto → ß2 in bronchial muscles, gut muscles α2 rs receptors → present in presynaptic membrane. & bladder Smooth muscles. α1 and → are excitatory. ß1 α2 → are inhibitory. Fate of catecholamines: 1 Between 50% and 80% of the norepinephrine that is released during an action potential is removed from the synaptic area by an active reuptake process. 2 The remainder of the released catecholamines diffuse into the surrounding tissue fluids or are degraded by two special enzymes: a.Catechol-O-methyltransferase, which is diffusely present in all tissues. b.Monoamine oxidase (MAO), which is found in the nerve endings themselves.  Chemical transmission in the ANS Chemical transmitter is a substance that is universally distributed in nervous system parallel to its receptors and enzymes needed for its synthesis and destruction.  Site of release of chemical transmitter: 1 The chemical transmitter at all preganglionic neurons (sympathetic & parasympathetic) is acetyl choline. 2 The chemical transmitter at both the preganglionic & postganglionic parasympathetic endings is acetyl choline. 3 The chemical transmitter at the postganglionic sympathetic nerve ending is mainly noradrenaline & to a less extent