PSIO 121 5th Edition Lecture 10 Outline of Last Lecture Nervous System Outline of Current Lecture Autonomic Nervous System Sympathetic Division I ANS System II ANS Functions Current Lecture OBJECTIVES 1 Describe the main difference that exists between the somatic and autonomic nervous systems 2 Differentiate between the parasympathetic and sympathetic nervous system in terms of anatomy and function 3 Describe the neurotransmitters used and the effects of the sympathetic nervous system Why do we need the ANS The ANS operates without conscious control operated via reflex arcs is controlled by centers in the hypothalamus and brain stem AUTONOMIC SYSTEM SOMATIC SYSTEM EFFECTORS Cardiac muscle smooth muscle and glands Skeletal Muscle CONTROL Involuntary Voluntary OUTPUT 2 efferent neurons exit CNS 1 efferent neuron exits CNS Somatic Nervous System the lower motor efferent neuron that stimulates the skeletal muscle exits the spinal cord CNS at the anterior horn Autonomic Nervous System one efferent neuron exits the spinal cord at the lateral horn and synapses with another efferent neuron in a ganglion cell bodies in the PNS The First efferent neuron is called preganglionic neuron and the second is the postganglionic neuron Sub Divisions of the ANS 1 2 Sympathetic Division fight of flight prepares body for stress Parasympathetic Division rest and digest promotes digestion and storage of nutrients Sympathetic Nervous System Thoracolumbar preganglionic neurons being in the T1 and L2 regions of spinal cord Most ganglia are located near the spinal cord Location of SNS Ganglia 1 Sympathetic trunk chain paired ganglia near spinal cord postganglionic neuron innervates visceral organs in thoracic cavity 2 Prevertebral Ganglia collateral anterior to vertebral bodies postganglionic neurons innervate abdominopelvic organs 3 Adrenal Medulla acts as a modified sympathetic ganglion postganglionic neurons are short and release norepinephrine 20 and epinephrine 80 into the blood stream NE and epinephrine are called catecholamines Sympathetic Trunk 3 cervical 11 thoracic 4 lumbar 4 sacral Prevertebral Ganglia celiac superior mesenteric inferior mesenteric Adrenal Medulla Special case Neurotransmitters of the SNS preganglionic neurons release ACh binds to nicotinic cholinergic receptors on postganglionic cell body Postganglionic neurons release norepinephrine NE binds to adrenergic receptors on effector cell Sweat Glands special Case Preganglionic neurons release ACh Posterior neurons release ACh instead of NE at the effector tissue ACh binds to muscarinic cholinergic receptors at sweat gland Adrenal Medulla special case preganglionic neurons release ACh Chromaffin cells act as postganglionic neurons and the adrenal medulla acts as a modifiedganglion Chromaffin cells release Epinephrine and Norepinephrine into the blood Catecholamines Epinephrine and NE NE is a neurotransmitter when it is released from sympathetic nerve endings directly at target tissues short lived effects NE is a hormone when it is released from the adrenal gland into the blood stream longer lasting effects Epinephrine is a hormone because it is released from the adrenal gland into the blood Adrenergic Receptors bind epinephrine adrenaline and norepinephrine noradrenaline at effector tissues 1 Alpha adrenergic receptors found in smooth muscle of arterioles bladder result in constriction when activated 2 Beta Adrenergic receptors found in heart bronchioles liver cause an increase in metabolism General Function of SNS Fight or Flight Goal to increase mental alertness increase energy availability glucose and bodys ability to handle a stressor Specific Responses to SNS Mobilize fuels Redistribution of blood flow Decrease urinary output and digestive functions Increase heart rate and blood pressure Increase activity of sweat glands Increase diameter of briochioles Dialation of pupils
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