20110106 Lecture 5 notes.txt

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Revision as of 00:35, 18 January 2011 by 24.15.60.132 (Talk)
  • started here on 01/06/2011 at 8:20AM.


Contents

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

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 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

The sympathetic and parasympathetics are two-neuron systems

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.

Sympathetic neuron routes

  • Preganglionic sympathetic neurons reside in the lateral horns of the spinal cord (Tl -L3)
  • There are two types of symp fibers:
    • B type are myelinated
    • C type or 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

Adrenal Medulla

  • Fight of 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

Catecholamine exocytosis

  • Splanchnic synapses on chromatin cells
    • Releases vesicles with ach
  • Chromatin has ach receptors
    • Opens Na+ channels
    • Cuases depolarization
  • 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 have to take it up and release it?

Parasympathetic nervous division

  • AKA craniosacral
  • 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

The brainstem nuclei associated with cranial nerves Ill,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 ... 
CN X originates from the nucleusambiguus, as well as the dorsal motor nucleus of the vagus and travels to terminal ganglia in the viscera ofthe thorax and abdomen

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. 
What is used to signal at the sympathetic ganglia?

Autonomic postganglionic axons do notform 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

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

Ganglionic sympathetic neurons expressnicotinic acetylcholine receptor-channels

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

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 went 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.

alpha-1 and m1-muscarinic receptors

  • Thes modulate cation channel activity in smooht muscle cells. 
**They do this by modulating Gq11?

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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