BIO 201 Anatomy & Physiology Lecture Schedule

Last Modified: October 19, 2000 (J. Crimando).

BIO201 Anatomy & Physiology
Lecture Outline 9: Autonomic Nervous System

I.Autonomic Nervous System:
    A. Compare Autonomic and Somatic Nervous Systems
       1. Afferents (inputs)
          a. somatic - general somatic & special senses, proprioceptors, conscious perception
          b. autonomic - general visceral senses, mostly not conscious perceptions
       2. Efferents (outputs)
          a. somatic efferents
             i. skeletal muscle targets
             ii. voluntary movements
             iii. always excitatory signals used
             iv. only acetylcholine (Ach) used
          b. autonomic efferents
             i. cardiac, smooth muscle & glandular targets
             ii. involuntary responses
             iii. excitatory or inhibitory signals used
             iv. Ach or norepinephrine (NE)
       3. Neuronal Pathways
          a. somatic pathways
             i. one efferent neuron used
             ii. cell body resides in CNS
             iii. axon extends directly to target organ
          b. autonomic pathways
             i. two efferent neurons used
             ii. 1st neuron cell body in CNS is myelinated, axon extends to ganglion ("preganglionic")
             iii. ganglion outside CNS where 1st signals 2nd neuron
             iv. 2nd neuron cell body in ganglion unmyelinated, axon extends to target organ ("postganglionic")

    B. Compare Sympathetic and Parasympathetic Pathways
       1. General distinctions
          a. sympathetic system
             i. "flight or fight" response
             i. increase heart rate/BP, skeletal muscle vasodilation, glucose released from liver, inhibits digestion
          b. parasympathetic system
             i. "rest & relaxation" response
             i. SLUD: Salivation, Lacrimation, Urination & Defecation; slows heart, activates digestion
       2. Preganglionic neurons
          a. sympathetic system
             i. "thoracolumbar" division
             ii. cell bodies in 12 thoracic & 1st few lumbar lateral grey horns
             iii. all release Ach
          b. parasympathetic system
             i. "craniosacral" division
             ii. cell bodies in brainstem (cranial nerves III, VII, IX, X) and 2-4 sacral lateral grey horns
             iii. all release Ach
       3. Autonomic ganglia
          a. sympathetic ganglia
             i. vertebral chain & collateral ganglia
             ii. located close to CNS
             iii. much divergence, many postganglionic synapses
          b. parasympathetic ganglia
             i. terminal ganglia
             ii. located close to target organ
             iii. little divergence, generally localized effects
       4. Postganglionic neurons
          a. sympathetic
             i. most release NE onto target organ (very few use Ach)
          b. parasympathetic system
             i. all release Ach onto target organ

    C. Autonomic Neurotransmitter Receptors
       1. Acetycoline (cholinergic) receptors
          a. nicotinic receptors (nAchR)
             i. on all symp., parasymp, postganglionic neurons and skeletal muscle
             ii. nicotine binds and mimics Ach
             iii. nAchR are always excitatory effects (cause depolarization)
             iv. on adrenals - excitatory; promotes NE secretion
             v. on skeletal muscle - excitatory; causes contraction
          b. muscarinic receptors (mAchR)
             i. on all parasymp. target organs
             ii. muscarine binds and mimics Ach
             iii. mAchR are excitatory OR inhibitory (depending on target tissue)
             iv. on cardiac muscle - inhibitory; slows heart rate
             v. on bronchiole smooth muscle - excitatory; causes constriction
             vi. on arteriole smooth muscle in skeletal muscles - inhibitory; causes vasodilation
       2. Norepinphrine (adrenergic) receptors
          a. Alpha-adrenergic receptors
             i. a-receptors are always exitatory
             ii. on mucosal, skin, cerebral arterioles - excitatory; causes local vasoconstriction
             iii. pseudoephedrine (nasal decongestants) bind to a-receptors
          b. Beta-adrenergic receptors (two major types B1 and B2)
             i. B-receptors are excitatory OR inhibitory (depending on target tissue)
             ii. on cardiac muscle - excitatory; B1-receptors increase heart rate & force
             iii. on coronary artery smooth muscle - inhibitory; B1-receptors cause coronary vasodilation
             iv. "beta-blocker" drugs block B1-receptors on heart (reduce blood pressure & heart rate)
             v. on systemic vein smooth muscle - excitatory; B2-receptors cause venous vasoconstriction
             vi. on bronchiole smooth muscle - inhibitory; B2-receptors cause bronchiole dilation
             vii. asthma inhalants activate B2-receptors, cause bronchiole dilation

This is only a general outline.
There may be material that has been discussed in lecture that is not included in this outline
and there may be material on this outline that has not been discussed in lecture.
Any material discussed in lecture or listed in this outline is "fair game" for the test.