20110106 Lecture 5 notes.txt

From Iusmphysiology

Current revision as of 01:34, 18 January 2011

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

[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

• stopped here on 01/06/2011 at 9AM