The Autonomic Nervous System Somatic vs Autonomic Nervous System o Somatic Nervous System Exam 3 Motor neurons innervate skeletal muscles aka effectors are skeletal muscles One synapse Conscious and unconscious movement o Autonomic Nervous System Motor neurons innervate smooth muscle cardiac muscle and glands effectors of the ANS Sensory neurons no overlap in function for ANS or SNS pain receptors can stimulate either somatic or autonomic reflexes Unconscious regulation subconscious control target tissues stimulated or inhibited Two synapses Has viscera as most of their effectors Efferent Pathways o Axons are a two neuron chain Preganglionic first neuron has a lightly myelinated axon Post ganglionic second neuron extends to an effector organ ANS Anatomy o Sympathetic Division and Parasympathetic Division Supply same organs but differ in features These 2 divisions counterbalance each other Most of the body organs have dual ANS intervention which is receiving impulses from both divisions neurons usually one stimulates and the other decreases activity Interaction between divisions Both division fibers innervate most visceral organs This results in dynamic antagonisms that precisely control visceral activity Sympathetic fibers increase heart and respiratory rates inhibiting digestion and elimination Parasympathetic fibers decreases heart and respiratory rates allowing digestion and elimination discard of wastes o Sympathetic Thoracolumbar Division Preganglionic cell bodies in lateral horns of spinal cord T1 L2 thoracolumbar Sympathetic Outflow Preganglionic fibers synapse in the chain ganglia Fibers from T5 L2 form splanchnic nerves abdomen and synapse with collateral ganglia Postganglionic fibers innervate the numerous organs of the body or chain The paravertebral ganglia form part of the sympathetic trunk About 23 ganglia 3 cervical 11 thoracic 4 lumbar 4 sacral 1 coccygeal Adrenal Medulla adrenal medulla Fibers of the thoracic splanchnic nerve pass directly to the A misplaced sympathetic ganglion Upon stimulation medullary cells secrete catecholamines NE and EPI into the blood and can only be secreted by postganglionic sympathetic Part of the ANS and ENS Endocrine o Parasympathetic Craniosacral Division Preganglionic cell bodies in nuclei of brainstem or lateral parts of spinal cord gray matter from S2 S4 Preganglionic axons from sacral region pass through pelvic splanchnic nerve to terminal ganglia Terminal ganglia located near organ innervated or embedded in wall of organ o Enteric Nervous System Nerve plexus within wall of the digestive tract ANS Neurotransmitters and Receptors o ACh and NE 2 major NTs of the ANS o Preganglionic axons release ACh stimulate post ganglionic sympathetic neurons o Parasympathetic Postganglionic axons release ACh o Cholinergic fibers release Ach 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 inhibitory Abdomen Thoracic inhibitory Abdomen excitatory o Parasympathetic Craniosacral Vagus Nerve X it s 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 Thoralumbar Adrenal gland part of kidneys is only innervated by sympathetic there is no post ganglionic neuron Collateral ganglia further away from the vertebrae sympathetic ganglia that is unpaired and located between the chain and the organ sympathetic chain ganglia paired parallel to one another T5 L2 splanchnic nerves synapse with collateral ganglia SNS Neurotransmitters o Adrenergic fibers sympathetic postganglionic axons that release NE Alpha NE binds to stimulatory 2 subclasses blood vessels Beta NE binds to inhibitory 3 subclasses GI tract pancreas adipose tissue Ex catecholamines on the heart are stimulatory pumping effect increases catecholamines on than abdominal organ are inhibitory o NT effects can be inhibitory or excitatory depending on receptor type o Preganglionic sympathetic releases ACh o ACh has a stimulatory effect on the soma of sympathetic postganglionic o Postganglionic sympathetic secrete catecholamines Epinephrine EP and Norepinephrine NE Sympathetic Division s Roles o Fights or flight o E activities exercise excitement embarrassment stress o Regulates many functions not subject to parasympathetic influence Ex adrenal medulla sweat glands kidneys most blood vessels Metabolic Effects of SNS o Promotes metabolic effects that are not reversed by the parasympathetic division Increased metabolic rate of body cells Raise blood glucose levels Mobilize fat as an energy source PNS Roles o D activities digestion defecation and diuresis relaxing after a meal o Lowers BP HR and respiratory rate o GI tract activity is high o Warm skin pupils constrict nap time ANS Physiology PNS Responses o SUDD Salivation Urination Digestion Defecation all increased The balance of the ANS Sympathetic and Parasympathetic tone is regulated by feedback loops between the spine and the brainstem with input fro the limbic system and oversight by the hypothalamus Parasympathetic neurons the Vagus nerve innervates the atrium of the heart and the gastrointestinal system The Endocrine System The Endocrine System An Overview o Responses occur slowly but last longer than those of the nervous system works with the nervous system to regulate body activity o Hypothalamus belongs of the nervous system but secretes hormones that control the endocrine system o Adrenal Medulla part of the nervous and endocrine system that is housed by the adrenal cortex which secretes many type of hormones o Pancreas endocrine and exocrine cells Hormones o Chemical substances secreted by cells into the blood o Regulate the metabolic function of other cells o Two main classes Amino acid based hormones Catecholamines amines thyroxine peptides insulin and proteins Receptors outside of the cell Steroids Synthesized from cholesterol Gonadal and adrenocortical hormones Produced in adrenal cortex Receptors insice the cell 1st nucleus and 2nd DNA Classification of Hormones based on chemical structure o Water soluble hormones all amino acid based hormones except thyroid hormone o Lipid soluble hormones steroid and thyroid hormones Mechanisms of Hormones o Hormone action on target cells 1 alter plasma membrane permeability of membrane potential by
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