Chapter 11 - Summary Human Anatomy & Physiology PDF

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Chapter 11 1. The Autonomic Nervous System (homeostasis; involuntary) a. Sympathetic Division i. Fight or flight 1. Activated during exercise, excitement, and emergencies b. Parasympathetic Division i. Rest and digest 1. Concerned with maintenance and conserving c. Dual innervation in the autonomic nervous system i. Both divisions of the ANS innervate most effector organs ii. Primary function 1. Regulate organs to maintain homeostasis iii. Parasympathetic and sympathetic activities tend to oppose each other d. Anatomy of the automatic nervous system DIAGRAM i. Two neurons from CNS to effector organs 1. Preganglionic neuron 2. Postganglionic neuron ii. Autonomic ganglia 1. Communication from preganglionic to postganglionic neuron 2. Intrinsic neurons iii. Effector organs 1. Cardiac muscle 2. Smooth muscle 3. Glands e. Anatomy of SNS DIAGRAM i. Preganglionic neurons originate in thoracolumbar spinal cord ii. General anatomy 1. Short preganglionic neurons to sympathetic chain 2. Long postganglionic neurons from chain to effector organs 3. Ganglia linked together in sympathetic chain iii. Exception to general anatomy 1. Collateral ganglia – outside chain 2. Adrenal medulla 3. Adrenal Gland a. Sympathetic preganglion synapse in adrenal medulla where chromaffin cells are (no axon) i. Release NT into blood stream iv. Sympathetic pathways to and from sympathetic chain 1. Preganglionic a. Exits via ventral root of spinal cord and enters spinal nerve b. Axons leave spinal nerve as white ramus and enter sympathetic ganglia c. Communicate in ganglia with postganglionic neurons 2. Postganglionic a. Leave ganglia as gray ramus and re-enter spinal nerve i. Enter via dorsal root

1. White ramus is off ramp ii. Exit via ventral root 1. Gray ramus is on ramp b. Travel to effector organ in spinal nerve f. Physiology of the SNS i. Fight or flight ii. Effect diffuse and long lasting iii. Specific effects 1. Innervation of all arteries and veins 2. Inhibition of digestion 3. Increased heart rate 4. Decreased saliva, tears, etc 5. Dilation of the eyes, lifts the eyelid 6. Increased mental alertness g. Anatomy of the PSNS i. Preganglionic neurons originate in brainstem or sacral spinal cord ii. Anatomy 1. Long preganglionic neurons to ganglia near effector organ 2. Preganglionic neuron communicates with postganglionic neuron in ganglia 3. Short post ganglionic neurons from ganglia to effector organs h. Physiology of the PSNS i. Rest and digest ii. Pupil constriction, lens bulding – close focus iii. Stimulate secretion of the large glands of the head- saliva, tears, mucous iv. Cardiac plexus- slows the heart rate v. Pulmonary plexus- slows respiratory rate vi. Esophageal plexus- aids in swallowing vii. PSNS drives food digestion viii. Sacral outflow 1. Regulated bladder, ureters, rectum, and reproductive organs ix. PS Nerves 1. Cranial Nerves a. X = vagus nerve b. III = oculomotor c. VII = facial nerve d. IX = glossopharyngeal nerve 2. Spinal Nerve a. Pelvic nerves distinct from somatic spinal nerves x. Mixed Composition of Autonomic Nerves 1. Efferent fibers a. ANS 2. Afferent Fibers a. Transmit information from visceral receptors to CNS b. Important in maintaining homeostasis i. Autonomic neuroeffector junctions

i. Autonomic Neurotransmitters and Receptors 1. Types of adrenergic receptors 2. Divisions and neurotransmitters a. Preganglionic neurons i. Acetylcholine b. PS postganglionic neurons i. Acetylcholine c. Sympathetic postganglionic i. Norepinephrine

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a. Adrenal Medulla i. Catecholamines 1. 80% epinephrine 2. 20% norepinephrine 3. little dopamine 2. Types of Cholinergic Receptors a. Nicotinic i. Open channels for cations (sodium and potassium) ii. Result = depolarization b. Muscarinic i. G protein coupled ii. Effect depends on target cell 3. Location of Cholinergic Receptors a. Autonomic post ganglionic i. Nicotinic cholinergic b. Effector organ for parasympathetic i. Muscarinic cholinergic

c. Skeletal muscle i. Nicotinic cholinergic 4. Types of Adrenergic Receptors (most receptors on effector organs of SNS) a. Two main classes: alpha and beta b. Each has a sub class c. All are coupled to G proteins i. Alpha 1 (constriction) and 2 ii. Beta 1 (increase heart rate), 2 (dilation), and 3 5. Properties of Alpha Adrenergic Receptors a. Located in effector organs of sympathetic nervous system b. Most common c. Usually excitatory d. Affinity greater for norepinephrine than epinephrine 6. Properties of Beta Adrenergic Receptors a. All activate cAMP b. Affinities for norepinephrine and epinephrine vary 7. Beta 2 a. Located in cardiac muscle and the kidneys b. Usually excitatory c. Equal affinity for norepinephrine and epinephrine d. Located in some blood vessels and smooth muscle e. Usually inhibitory f. Greater affinity for epinephrine than norepinephrine 8. Beta 3 a. Located in adipose tissue b. Usually excitatory c. Equal affinity for norepinephrine and epinephrine 9. Tropicamide a. Anti muscarinic drug b. Dilation of pupil by targeting circular muscle (blocking) c. Phenylephrine i. Adrenergic agonist that causes vasoconstriction in nose and radial muscle contraction so dilation ii. Autonomic Neuroeffector Junctions 1. Synapses between efferent and effector organs in the autonomic nervous system 2. Between postganglionic neuron and effector organ 3. Neurotransmitter stored in axon swellings a. Varicositites b. Released in response to action potential in post ganglionic neurons iii. Events at Neuroeffector Junction 1. Action potential arrives at varicosity 2. Voltage gated calcium channels open 3. Calcium triggers exocytosis of neurotransmitter

4. Neurotransmitter binds with receptors on effector organ 5. Response in effector organ 6. Neurotransmitter degraded, diffuses away, reuptake k. Regulation of autonomic function i. Dual innervation of organs ii. Balance between parasympathetic and sympathetic activity 1. Para- rest 2. Sym- excitation iii. Increase in parasympathetic activity coupled with decreases in sympathetic activity and vice versa iv. Tonic Activity at Rest 1. Both branches active 2. Para dominates 3. Cerebral Cortex 4. Limbic Lobe 5. Hypothalamus a. Overall integration of ANS (boss) 6. Reticular Formation of brain stem a. Regulation of pupil size, respiration, heart, blood pressure, swallowing 7. Spinal Cord a. Urination, defecation, ejection, and ejaculation reflexes 2. The Somatic Nervous System a. Anatomy of the SNS i. Somatic Nervous System 1. One neuron between CNS and effector organ a. Motor neuron 2. Effector organ = skeletal muscle 3. Voluntary control ii. Anatomy 1. Motor neurons 2. Originate in ventral horn 3. Innervate skeletal muscle 4. Neurotransmitter = acetylcholine 5. Receptors in skeletal muscle = nicotinic cholinergic iii. Motor unit 1. Motor neuron and the muscle fibers it innervates b. The neuromuscular junction i. Synapse between a motor neuron and a muscle fiber ii. Anatomy 1. Terminal bouton = axon terminal 2. Moto end plate = specialized muscle membrane at junction 3. All motor neurons release acetylcholine 4. Receptors on skeletal muscle cells are nicotinic cholinergic receptors 5. All synapses are excitatory 6. Acetyl cholinesterase degrades acetylcholine in synaptic cleft

iii. Activities 1. Activation of motor neuron depends on summation of EPSPs/IPSPs 2. Action potential in motor neuron triggers release of acetylcholine at neuromuscular junction 3. End plate potential occurs at motor end plate iv. Communication 1. Action potneital arrives at axon terminal 2. Voltage gated calcium channels open 3. Calcium enters cell triggering release of ACh 4. ACh diffuses across cleft and binds to nicotinic receptors on motor end plate 5. ACh triggers opening of channels for small cations sodium and potassium 6. Net movement of positive charge in  depolarization a. End plate potential b. EPP> ESPS 7. EPP causes action potential in muscle cells 8. Action potential spreads through muscle causing contraction v. Physiology of the NMJ 1. Places of interruption in synaptic events reveal the normal physiology 2. Spastic vs. flaccid paralysis 3. Lambert-Eaton syndrome a. Body attacks voltage gated calcium channels b. Two groups i. Smokers 1. Underlying lung cancer a. Gives way of diagnosing early 4. Myasthenia gravis a. Rag doll illness b. Muscle weakness i. More effort  weaker muscle c. Immune system destroys receptors d. Autoimmune disease attacking acetylcholine receptors 5. Toxins a. Neuronal Sodium Channel i. Tetrodotoxin 1. Poisonous a. Ingest 2. Toxin a. Ingest 3. Found in eggs and liver of puffer fish 4. Targets voltage gated sodium channels; blocks nerve conduction and contraction ii. Saxitoxin b. Calcium Channel i. Conotoxin

c. Muscle Sodium Channel i. Tetrodotoxin ii. Saxitoxin 1. Dinoflaggellate Karenia brevis or Pyrodinium bahamense 2. Red tides a. Blocks breathing in manatees 3. Neurotoxins a. Neuronal sodium channel and muscle b. Same effects as tetrodotoxin iii. Conotoxin 1. Cone snail 2. Calcium channel blocker 3. Blend of lots of toxins d. AChR Channel i. Acetylcholine (+) ii. Nicotine (+) iii. Tubocurarine 1. Used on arrowx/blow darts 2. Acetylcholine receptor antagonist; blocks receptors 3. reversible iv. Bungarotoxin 1. Taiwanese banded krait; bungarus multicinctus 2. Acetylcholine antagonist 3. Irreversible a. Flaccid paralysis/ suffocation i. Inhibit contraction b. Labels acetylcholine receptors in tissue i. Live and fixed ii. Combined with red fluor e. Potassium Channel i. Dendrotoxin f. ACh Release i. Tetanus toxin 1. Caused by the tetanus bacterium clostridium tetani 2. Spastic paralysis 3. Retrograde tranaport to brain where there is inhibition of skeletal muscle activity a. Disinhibition b. Breaks the brake 4. gangliosides at the presynaptic inhibitory motor nerve endings is taken up into the axon by endocytosis. The effect of the toxin is to block the release of

inhibitory neurotransmitters glycine and gammaaminobutyric acid (GABA) across the synaptic cleft, which is required to check the nervous impulse. If nervous impulses cannot be checked by normal inhibitory mechanisms, the generalized muscular spasms characteristic of tetanus are produced. The toxin appears to act by selective cleavage of a protein component of synaptic vesicles, synaptobrevin II, and this prevents the release of neurotransmitters by the cells. ii. Botulinum toxin 1. Muscle relaxed to get rid of wrinkles 2. Protein produced by clostridium botulium a. Bacteria toxin; eat and create waste product 3. Considered by some to be most acutely toxic substance known 4. Neurotoxin a. Can cause botulism b. Flaccid paralysis c. Prevents exocytosis i. Blocks vesicle fusion/NT release g. Acetylcholinesterase i. Physostigmine ii. DFP h. Agrin i. Has a receptor (MuSK) ii. Causes phosphorylation and signaling cascade iii. All acetylcholine receptors get rectuired and aggregate so that receptors directly opposed from NMJ iv. Agrin is not NT v. ACh release  action potential...