20110106 Lecture 5 notes.txt

From Iusmphysiology

  • started here on 01/06/2011 at 8:20AM.


Contents

[edit] Learning Objectives

  1. Understand the division of the Autonomic Nervous System (ANS) into Sympathetic and Parasympathetic subsystems
  2. Understand the anatomic & physiologic differences between these two divisions
  3. Understand the functions controlled by the Autonomic Nervous System

[edit] The autonomic nervous system is responsible for maintaining the constant internal environment in our body

  • The ANS includes the parasympathetic and sympathetic nervous systems and the enteric nervous system
    • Enteric covered in GI lectures.
  • The autonomic system is responsible for controlling the unconscious activities of the body like secretion, heart rate, et cetera.

[edit] The autonomic nervous system overview

  • Parasympathetic and sympathetic produce opposite effects.
    • The excpetions are the sweat glands, blood vessls; only get sympathetic innervation.
  • The ANS focuses on regulating smooth muscle, heart rate, and glands.
    • BP, heart rate, pupil size, one more

[edit] The sympathetic and parasympathetics are two-neuron systems

[edit] Sympathetic division of the autonomic nervous system

  • AKA thoracolumbar division
  • The sympathetics are in the lateral horns of the spinal cord, between t1 and l3.
  • Presynaptic axons go to the sympathetic ganglion
  • The superior cervical ganglion innervates the head.
  • The middle cervical ganglion innervates the lung and heart.
  • The adrenal medulla and the sweat glands and errector pilli and blood vessels only receive sympathetic innervation.

[edit] Sympathetic neuron routes

  • Preganglionic sympathetic neurons reside in the lateral horns of the spinal cord (Tl -L3)
  • There are two types of sympathetic fibers:
    • B type which are myelinated
    • C type which are unmyelinated
  • The sympathetic nerves pass through the white ramus
    • White because it is mostly myelinated fibers.
  • Some will synapse in the ganglion, others will travel along the (caudally or coronally) along the chain.
    • Others will move out of the chain, even.
  • Those that synapse in the ganglion, then leave via grey rami to join the spinal nerves again to travel to the effector cells.
  • Those (presynaptics) that move through the ganglia without synapsing move on to paravertebral ganglion (around the aorta, very short distance away) to synapse
    • Paravertebral ganglia are around the aorta (celiac, mesenteric, etc.)
  • Most nerves synapse on many (around 200) ganglia, not just one.
  • Sympathetic post-synaptics generally follow blood vessels
  • "Visceral sensory afferents modulate preganglionic neuron activity and trigger feedback mechanisms in the hypothalamus, pons and medulla."

[edit] Adrenal Medulla

  • Fight or flight response
    • Starts in the lateral horn of T10 through L1
    • Moves along splanchnic nerves
      • Unmyelinated = C type fibers
    • Reaches adrenal medulla
    • Activates chromatin cells via neuronal region
      • Considered to be part of the sympathetic nervous system

[edit] Catecholamine exocytosis

  • Splanchnic nerves synapses on chromaffin cells
    • Splanchnic nerves release vesicles with acetylcholine
    • Chromaffin cells have ach receptors
  • When chromafinn cells bind the acetylcholine receptors, Na channels are opened such that Na rushes into the chromaffin cell.
  • Upon Na efflux, the voltage changes causing depolarization
  • Then voltage-gated Ca+ channels open because of initial depolarization
  • Dense core vesicles have catecholamines 
**Usually catecholamines in clear vesicles, but these ...?
  • Epinepherine and norepinepherine released into the blood by vesicle release 
Does epithelial cell of the blood vessel have to take it up and release it?

[edit] Parasympathetic nervous division

  • The parasympathetic division is also known as the craniosacral division.
  • Parasympathetic nerves come from S2-S4 and the brain.
  • Oculomoter = CN3
    • Invervates the eye
  • Sympathetic ganglia are very close to the spinal cord
    • B type fibers are very short (presynaptic) 
Are presynaptic fibers of sympathetic system always of type B?
  • Parasympathetic presynaptic fibers are very long and post-synaptic fibers are short.
  • There are only 4 parasympathetic ganglia
    • Pterogopalatine
    • Submandibular
    • Otic
    • Ciliary
    • These provide much of the innervation to glands of the head

[edit] The brainstem nuclei associated with cranial nerves III, VII, IX, and X host parasympathetic preganglionic neurons

  • CN3 comes from the Edinger-Westphal nucleus and travels to the ciliar ganglion
  • CN7 comes from the superior salivatory nucleus and travels to the pterygopalatine and submandibular ganglia
  • CN9 comes from the inferior salivatory nucleus and travels to the otic ganglia
  • CN10 comes from the nucleus ambiguus and the dorsal motor nucleus of the vagus; it supplies the terminal ganglia in the viscera of the thorax and abdomen

[edit] Autonomic nervous system chemistry

  • Parasympathetic presynaptic are long and release ach.
  • In parasympathetic ganglia, the nicotinic receptor is expressed.
  • Parasympathetic effector cells generally express muscarinic g-protein receptor.
  • Sympathetics are in the lateral horn and have short pre-synatpic fibers
  • Sympathetic effector cells generally express adrenergic receptors.
    • There are alpha and beta adrenergic receptors.
    • Epinepherine can bind at adrenergic receptors, mostly beta versions
      • Heart, etc.
  • At the ganglia in sympathetic arcs, ach is usually released to be bound by ganglionic cells on nicotinic receptors.

[edit] Autonomic postganglionic axons do not form true synapses

  • Vesicles are released to provide NT for smooth muscle stimulation.
  • Two types of smooth muscle:
    • Multiunit
      • Ex: smooth muscle of the eye
    • Singleunit
      • Blood vessels
      • Connected wtih gap jxns
      • NT from post-ganglionic nerve affects one cell and AP is passed from smooth muscle to smooth muscle by gap jxns

[edit] Autonomic Functions

  • Pupil:
    • Para constricts, sympathetic dilates
  • Sweat glands
    • Para no action, symp secretion
  • Blood vessels
    • Para no action, symp constrict or dilate (alpha-1-R, beta-R
  • Muscle
    • Para no action, symp constrict
  • Heart rate
    • Para decreases, symp increases
  • Bronchioles
    • Para constricts, symp dilates
  • GI
    • See slide

[edit] Ganglionic sympathetic neurons express nicotinic acetylcholine receptor-channels

  • was laughing too hard about "practicing" to catch anything. 
This and the remaining slides were unclear.

[edit] Metabotropic receptors on the target cells

  • Metabotropic receptors are usually g-protein receptors.
    • They differ by what the g-protein activates.
    • This is how we have different reactions for different tissues. 
*He started to go over each of these three figures and highlighted pretty much all the text at the bottom
*Then he got worried about time and moved on w/o talking about the last of the three.

[edit] alpha-1 and m1-muscarinic receptors

  • Alpha-1 and m1-muscarinic receptors modulate cation channel activity in smooth muscle cells. 
**They do this by modulating Gq11?

[edit] References

  • Baron W.F., Boulpaep E.L. Medical physiology, Elsevier Saunders, Second Updated Edition, 2009
  • Koeppen B.M., Stanton B.A. Berne and Levy Physiology, 6th Updated edition, Elseiver-Mosby, 2010
  • Guyton A.C., Hall J.E. Textbook of medical physiology, Elsevier­Saunders, 11th Ed., 2006
  • Purves D., Augustine G.J., Fitzpatrick D., Hall W.C., LaMantia A-S., McNamara J.O., Williams S.M. Neuroscience, Sinauer Associates, Inc., 3rd Ed., 2004
  • Netter F.H. Atlas of human anatomy. Elsevier Health Sciences, 2006


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