I. Somatic Nervous System Vs. Autonomic Nervous System
A. Somatic NS – voluntary, skeletal muscle
-one neuron from brain/spinal cord releases Acetylcholine (ACh) on
skeletal muscle (nicotinic receptors)
B. Autonomic NS – involuntary; glands, heart, smooth muscle
-two chain neuron
II. Autonomic Nervous System (ANS) = Parasympathetic Nervous System (PNS) and Sympathetic Nervous System (SNS)
III. Functional Goals of SNS and PNS
A. SNS
-fight/flight
– mental alertness ——– stimulates reticular activating system
– metabolic rate
– digestive / urinary systems
-activates energy reserves – adipose, liver, muscle
– respiratory rate and dilation of bronchioles
-BP and HR
-activates sweat glands
-feeling of euphoria / temporary insensitivity to pain
– muscle tone, tremble with fear
-dilate pupils – distant vision
B. PNS
– metabolic rate
– HR and BP
– digestive activity (peristalsis and secretions) / salivary secretions
– blood flow to GI tract
– urination / defecation
-constrict pupils — focus on nearby objects
-constriction of respiratory passages
-sexual arousal – erection of penis and clitoris
-create energy reserves (glycogen and lipids)
IV. Neurotransmitters and Receptors
A. Acetylcholine (ACh) – cholinergic fibers
-somatic fibers
-all preganglionic fibers
-postganglionic fibers of PNS
–Receptors that bind ACh
1. Nicotinic receptors
-SNS and PNS ganglia
-skeletal muscle (somatic NS)
-always excitatory
2. Muscarinic receptors
-all PNS organs served
-inhibitory and excitatory
****ACh is deactivated by AchE (cholinesterase)
B. Norepinephrine (NE) – adrenergic fibers
-sympathetic postgang. Fibers
–Receptors that bind NE
1. Alpha receptors
–alpha-1 (excitatory)
ex. vessels of digestive viscera
–alpha-2 (inhibitory)
ex. Secretory glands of digestive system
2. Beta receptors
–beta-1 (excitatory)
ex. Increase HR and force of contraction
–beta-2 (inhibitory)
ex. Smooth muscle in airways, dilate
****NE is deactivated by Monoamine Oxidase (MAO)
