Lecture XVI

• I. The ANS

  • part of the peripheral nervous system
  • motor signals only
  • involuntary
  • excitatory or inhibitory
• Added Note:

  • the ANS can do many things
  • excitatory increases activity
  • inhibitory decreases activity
• I. The ANS. A. Two Divisions

  • sympathethic: activates overall metabolism, inhibits digestion and production
  • parasympathetic: inhibits overall metabolism, excites digestion and production
• Added Note:

  • sympathetic division increases heart rate, blood flow, and respiration
  • sympathetic is the fight or flight
  • parasympathetic is the rest and digest
• I. The ANS. A. Two Divisions. 1. Dual Innervation

  • target organ (effector) gets signals from both division
  • exception: blood vessels and sweat glands are under only sympathetic control
• I. The ANS. A. Two Divisions. 1. Dual Innervation. a. Plexuses

  • areas in core of body where neurons from both division weave together
• Added Note:

  • parasympathetic is more internal
  • organ listens to neurotransmitter with the bigger amount
• I. The ANS. A. Two Divisions. 2. Antagonistic Effects

  • target (effector) cells have opposing responses
• Added Note:

  • one says one thing, the other says another thing
• I. The ANS. A. Two Divisions. 3. Two Types of Neurons. a. Preganglionic

  • always starts in the CNS
• I. The ANS. A. Two Divisions. 3. Two Types of Neurons. a. Preganglionic.

  i. Sympathetic: lateral gray horns of T1 - L2

  ii. Parasympathetic: brainstem and sacral spinal cord
• I. The ANS. A. Two Divisions. 3. Two Types of Neurons. a. Preganglionic. i. Sympathetic. ii. Parasympathetic

  • both are myelinated by schwann cells
  • use acetylcholine as neurotransmitter
  • nAChR: nicotinic ACh receptors is used at ganglion
• Added Note:

  • sympathetic is shorter
  • parasympathetic is longer
• I. The ANS. A. Two Divisions. 3. Two Types of Neurons. b. Ganglionic Neurons

  • start in ganglia (PNS)
  • always respond to ACh, get excited due to receptor
  • always respond with action potential
  • always unmyelinated
• I. The ANS. A. Two Divisions. 3. Two Types of Neurons. b. Ganglionic Neurons. i. Sympathetic

  • long axon that will release norepinephrine
  • special organ: adrenal medullae
  • releases E and NE into blood
  • creates rapid, organismal response
  • contains varicosities to release more NE
• I. The ANS. A. Two Divisions. 3. Two Types of Neurons. b. Ganglionic Neurons. ii. Parasympathetic

  • short postganglionic axons
  • release ACh
• I. The ANS. A. Two Divisions. 4. Sympathetic Division. a. Thoracolumbar

  • cell bodies of preganglionic neurons are in T1 - L2
  • ventral root -> ventral ramus -> white ramus (rami communicantes)
  • if we need to innervate the back and sides
  • synapse need (at ganglion) -> gray ramus -> then two one of the following
  • go to the side and limbs through the ventral ramus or the back through the dorsal ramus