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PET3322 Exam 3 Study GuideAUTONOMIC NERVOUS SYSTEMConsists of motor neurons that innervate smooth and cardiac muscle and glands- Operate via subconscious control- Have viscera as most of their effectorsDiffers from SNS in the following 3 areas:- Effectorso SNS – effectors are skeletal muscleso ANS – effectors are cardiac muscle, smooth muscle, and glands- Efferent pathwayso Axons of the ANS are a two-neuron chain The preganglionic (first) neuron has a lightly myelinated axon The ganglionic (second) neuron extends to an effector organo Two divisions of ANS: sympathetic and parasympathetic Most body parts have dual innervation- Target organ responseo The nerve impulses from one division stimulates an organ, impulses from the other division decrease activityInteractions of the Autonomic Divisions- Most visceral organs are innervated by fibers from both divisionso Results in dynamic antagonisms that precisely control visceral activity- Sympathetic fibers:o Increase heart and respiratory rateso Inhibit digestion and elimination- Parasympathetic fibers:o Decrease heart and respiratory rateso Allow for digestion and eliminationNeurotransmitters and Receptors- ACh and NE are the two major neurotransmitters of the ANS- ACh o Released by all preganglionic axons and all parasympathetic postganglionic axonso Cholinergic fibers: ACh-releasing fiberso Inhibit heart, stimulate abdominal muscle- ACh Receptorso On all effector cells; stimulated by postganglionic cholinergic fiberso ACh binding: Can be either inhibitory or excitatory Depends on receptor type of the target organ- Catecholamines: stimulate heart, inhibit abdominal muscle- SNSo Adrenergic fibers: sympathetic postgan. axons that release NEo NT effects can be excit./inhib. depending upon the receptor type- Adrenergic receptorso Two types: alpha and betao Each type has two or three subclasseso Effects of NE binding to: Alpha receptors is generally stimulatory- α1: + blood vessels Beta receptors is generally inhibitory- β2: - GI tract, + pancreas- β3: + adipose tissueIntroduction to ANS- Sympathetic Outflowo From spinal cord segments T1 to L2o Preganglionic fibers synapse in the chain (paravertebral)gangliao Fibers from T5 to L2 form splanchnic nerves (abdomen) andsynapse with collateral gangliao Postganglionic fibers innervate the numerous organs of thebodySympathetic Trunks and Pathways - The paravertebral ganglia form part of the sympathetic trunk or chain- Typically there are 23 ganglia: 3 cervical, 11 thoracic, 4 lumbar, 4 sacral, and 1 coccygealAdrenal Medulla (below)- Fibers of the thoracic splanchnic nerve pass directly tothe adrenal medulla- A “misplaced” sympathetic gangliono Upon stimulation, medullary cells secrete NEand EPI into the blood- Source of catecholamineRole of the Sympathetic Division- “fight or flight”- Involves E activities: exercise, excitement, emergency,and embarrassment- Regulates many functions not subject toparasympathetic influenceo Activity of adrenal medullao Sweat glandso Kidneyso Blood vessels (vasoconstriction and vasodilation)- Metabolic effectso Not reversed by parasympathetic division Increases metabolic rate of body cells Raises blood glucose levels Mobilizes fat as an energy sourceRole of Parasympathetic Division- Most of the parasympathetic ganglia are located very close to the target organs- Involves the D activities: digestion, defecation, and diuresis- Illustrated by a person relaxing after a mealo Blood pressure, heart rate, respiratory rates decreaseo Gastrointestinal tract activity increaseso Skin is warm; pupils constrictedPhysiology of ANS- The balance of autonomic sympathetic-para. tone is regulated by feedback loops between the spinal cord and brainstem, with input from the limbic system and oversight by hypothalamusTHE ENDOCRINE SYSTEMHormones: chemical substances secreted by cells intothe blood; regulate the metabolic function of othercellsCirculating hormones Chemistry of Hormones- Two main classeso Amino acid-based hormones Amines, thyroxine,peptides, and proteinso Steroids (produced by gonads andadrenal cortex) Synthesized from cholesterol Gonadal and adrenocortical hormonesBlood capillaryEndocrine cellCirculating hormoneHormone receptorDistant target cellsMechanisms of Hormone Action- Two mechanisms, depending on their chemical nature1. Water-soluble hormones (all amino-acid-based hormones except thyroid hormone) – Slide 9 Cannot enter the target cells Receptors on cell membrane Coupled by G proteins to intracellular second messengers that mediate the target cell’s response2. Lipid-soluble hormones (steroid and thyroid hormones) – slide 11 Receptor in nucleus Act on intracellular receptors that directly activate genes- Hormone receptoro Is a protein molecule to which a particular molecule binds stronglyo Responds to several different hormones- Target Cell Specificityo Hormones circulate to all tissues but only activate target cells Target cells must have specific receptors to which the hormone bindso Examples of hormone activity: ACTH receptors are only found on certain cells of the adrenal cortex Thyroxin receptors are found on nearly all cells of the body- Target Cell Activationo Depends on three factors: Blood levels of the hormone Relative number of receptors on the target cell The affinity of those receptors for the hormone- Interaction of Hormones at Target Cellso Two types of hormone interactions Synergism – more than one hormone produces the same effects on a target cell- Both EPI and glucagon = ^ blood glucose Antagonism – one or more hormones opposes the action of another hormone- Insulin (decreases blood glucose) VS. glucagon (increases blood glucose)Control of Hormone Release- Blood levels of hormone: o Are controlled by negative feedback systemso Vary only within a narrow desirable rangeo The output shuts off the original stimulus- Humoral Stimulio Changing blood levels of ions and nutrients directly stimulates secretion of hormones Ex: Ca2+ in the blood- Declining blood Ca2+ concentration stimulates the parathyroid glands to secrete PTH (parathyroid hormone)- PTH causes Ca2+ concentrations to rise and the stimulus is removed- Neural Stimuluso A NT stimulates the gland to secrete it hormone- Hormonal Stimulio Hormones stimulate other endocrine organs to release their hormones Hypothalamic hormones stimulate the release of most anterior pituitary


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FSU PET 3322 - Exam 3 Study Guide

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