Autonomic Nervous system Consists of Motor Neurons that o Innervate supply of nerves smooth and cardiac muscle and glands o Make adjustments to ensure optimal support for body o Subconscious control o Have viscera as most of their effectors Different than SNS because o Has effectors away from brain For SNS skeletal muscles For ANS cardiac muscle Heart smooth muscle and glands o Efferent pathways 2 Neuron Motor Chain so needs 2 neurons to connect to the organ 1 Preganglionic neuron has a lightly myleniated axon 2 Post Ganglionic neuron extends to an effector organ with a soma for the response o Target organ responses o ANS 1 snyapse 2 Neurons 1 Ganglia Sympathetic and Parasympathetic DIVISIONS Interactions o These 2 divisions counterbalance each other o Most of the body organs have dual ANS intervention which is receiving impulses from both division s neurons usually one stimulates and the other decreases activity o Both divisions fibers innervate most visceral organs o This results in Dynamic antagonisms that precisely control visceral activity o Sympathetic fibers INCREASE heart rate and respiratory rates and inhibit digestion and elimination o Parasympathetic DECREASE heart rate and respiratory rates allowing digestion and elimination ANS Neurotransmitter and Receptor o ACh and NE are the 2 major neurotransmitters of the ANS o ACh is released by all preganglionic axons and all parasympathetic postganglionic axons o Cholinergic fibers ACh releasing fibers ACh Receptors o All ACh receptors on ALL ORGAN EFFECTOR cells are stimulated by postganglionic cholinergic fibers o ACh binding depends on the receptor type of the target organ and can either be inhibitory or excitatory Thoracic Inhibits Abdomen Excites o In Parasympathetic CRANIOSACRAL Vague Nerve aka X its soma extends from medulla oblongata most pre ganglionic parasympathetic neurons extend from here and the rest extend from sacral part of craniosacral division o Sympathetic T1 L2 THORALUMBAR The adrenal gland part of kidneys is ONLY innervated by sympathetic no post ganglionic neuron collateral ganglia farther away from vertebrae sympathetic ganglia that is unpaired and located between the chain and the organ sympathetic chain ganglia paired parallel to one another these pairs can be seen on the below diagram from T1 to L2 T5 L2 splanchnic nerves synapse with collateral ganglia SNS Neurotransmitters and Receptors o Adrenergic fibers sympathetic postganglionic axons that release NE vessels The receptors are of two types alpha or beta Alpha NE binds to stimulatory 2 subclasses blood Beta NE binds to inhibitory 3 subclasses GI tract pancreas adipose tissue o Neutransmitters can be excitatory or inhibitory depending upon the receptor type Sympathetic outflow o From spinal cord T1 L2 o Preganglionic fibers synapse in the chain paravertebral ganglia chain o Fibers from T5 L2 form splanchnic nerves abdomen and synapse with collateral ganglia o Postganglionic fibers innervate the numerous organs of the body o The paravertebral ganglia form part of the sympathetic trunk or o About 23 ganglia 3 cervical 11 thoracic 4 lumbar 4 sacral and 1 coccygeal Adrenal Medulla o Fibers of thoracic splanchnic nerve pass directly to the adrenal medulla o A misplaced sympathetic ganglion o Part of the ANS and ENS Endocrine o Upon stimulation medullary cells secrete Catecholamines NE and EPI into the blood and can only be secreted by Postganglionic Sympathetic NE Norpinephrine EPI Epinephrine Sympathetic Division s Roles and Unique Roles o Fight or flight o Involves E activities exercise excitement and embarrassment STRESS o Regulates many functions not subject to parasympathetic influence Examples adrenal medulla sweat glands kidneys and Metabolic effects of SNS most blood vessels o Promotes metabolic effects that are NOT REVERSED by the parasympathetic division Increase metabolic rate of body cells Raise blood glucose levels Mobilize Fat as an energy source PNS Roles meal o D activities digestion defection and diureses relaxing after a o Lowers blood pressure heart rate and respiratory rate o GI tract activity is high o Warm skin pupils contstricy NAP TIME ANS Physiology PNS Responses SUDD Salivation Urination Digestion Defecation all INCREASED The balance of the ANS sympathetic and Parasympathetic tone is regulated by feedback loops between the spinal and the brainstem with input from the limbic system and oversight by hypothalamus An important thing to remember about Parasympathetic neurons is that the Vagus nerve innervates the atrium of the heart and the gastrointestinal system Endocrine System response occur slowly but last longer than those of the nervous system works with the nervous system to regulate body activity Hypothalamus Role belongs to the nervous system but secrets hormones that control the endocrine system Adrena Medulla Part of the nervous and the endocrine system that is housed by the adrenal cortex which secretes many types of hormones Pancreas has endocrine and exocrine cells endocrine cells secrete glucagon and insulin talked more about later Hormones chemical substances secreted by cells into the blood o Regulate the metabolic function of other cells 2 main classes 1 Amino acid based hormones Catecholamines amines thyroxine peptides insulin and proteins Receptors OUTSIDE the cell 2 Steroids synthesized from cholesterol Prouduced in Gondal and adrenocortical adrenal cortex Receptors inside the cell 1st nucleus and 2nd DNA Mechanism of Hormones Action o Hormone action on target cells 1 After membrane permeability of membrane potential by opening or closing ion channels 2 Stimulate synthesis of proteins 3 Activate deactivate enzyme systems 4 5 Stimulate mitosis Induce secretary activity 2 mechanisms depending on their chemical nature 1 Water Soluble all amino acid based hormones except thyroid hormone Cannot enter target cells Act on plasma membrane Couple by G Proteins to intracellular second messangers 2 Lipid Soluble Steroid and thyroid hormones Acts on intracellular receptor that directly activate gene activity and mRNA sends out a message to produce protein to tell muscle to get bigger Hormone Receptor o Is a protein molecule to which a particular molecule binds strongly and responds to several different hormones o So a hormone binds to a protein receptor Response o Hormones circulate to all tissues but only activate cells referred as o Target cells have specific receptors to which the hormones binds Target cells Target
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