ch 14

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Author:
jmacedo
ID:
83554
Filename:
ch 14
Updated:
2011-05-03 22:31:02
Tags:
ANS
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Description:
autonomic nervous system
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  1. ANS
    motor division of the PNS
  2. effectors
    cardiac or smooth muscle or glands
  3. pathway
    a 2 neuron motor unit
  4. preganglionic neuron
    its cell body is in the brain or cord
  5. autonomic ganglion
    the site of synapse
  6. post ganglionic neuron
    its cell body and/or dendrites are in the ganglion

    effector
  7. all preganglionic neurons release
    ACH
  8. post ganglionic neurons release
    NE or ACH
  9. sympathetic division
    pre ganglionic neurons cell bodies are in the thoracic segments & the first 2 or 3 lumbar segments of spinal cord
  10. symp division: 2 ganglion types
    • paravertebral
    • prevertebral
  11. paravertebral
    sympathetic trunk
  12. prevertebral
    anterior and associated w/ large abdominal arteries

    ganglia are close to CNS and far from effectors
  13. symp division: preganglionic fiber
    synapses w/ many post ganglionic neurons & stimulate numerous visceral effectors
  14. Parasympathetic division
    craniosacral
  15. PNS
    1) preganglionic neurons cell bodies are in the cranial nerves and the sacral segments of the spinal cord
  16. PNS ganglion type
    terminal ganglia-
  17. terminal ganglia
    located at the end of the pathway, close to or within the effector

    ganglia are far from the CNS and close to effectors
  18. PNS preganglionic fiber
    synapses with 4 or 5 post ganglionic neurons and stimulate a single visceral effector
  19. ACH- acetylcholine
    • -released by all preganglionic neurons in both divisions
    • -released by all parasympathetic post-ganglionic neurons
    • - releasd by a few sympathetic post ganglionic neurons (sweat glands, blood vessels, some skeletal muscles, external genitalia)
    • - short lived, rapidly degrading
  20. Norepinephrine
    • released by most sympathetic post- ganglionic neurons
    • - has longer lasting more widespread effects- because its is broken down much more slowly
  21. Receptors
    • it is the receptor which determines the effect of the neurotransmitter on the effector.
    • same Neurotransmitter will have diff effects depending on the type of receptor
  22. choligergic receptors
    bind ACH, named for drugs that bind to them and mimic ACH's effect
  23. nicotinic
    found on all post-ganglionic neurons in both divisions and on hormone producing cells of the adrenal medulla
  24. ACH @ nicotinic receptors
    • always excitatory
    • opens ion channels
    • depolarizes the post-synaptic membrane
  25. muscarinic
    • found on all effector cells of parasympathetic target organs and a few sympathetic targets
    • eccrine sweat glands & some blood vessels in skeletal muscles
  26. effects of ACH @ muscarinic
    can be excitatory (smooth muscle of digestive tract) or inhibitory (heart) depending on the subclas of receptor located on the target organ
  27. adregergic receptors
    bind norepinephrine and are found on most sympathetic post-ganglionic neurons
  28. alpha
    effects are usually excitatory by causing increased permeability of membrane to Na+
  29. beta
    most have inhibitory effects by causing increased permeability to K+ out and Cl- in
  30. beta subtype exception
    • in the heart NE binding causes an increase in strength of contraction & heart rate
    • hence, use of beta blockers for high blood pressure
  31. overview of interaction between divisions
    • 1) dual innervation
    • 2) dynamic antagonism
    • 3) parasympathetic resting and digesting
    • 4) sympathetic flight or fight
    • 5) cooperative effects
  32. emergency effects
    increase heart rate, open airways, inhibit digestion & elimination
  33. afterwards
    heart rate & airway diameter return to normal, digestive processes, refuel & eliminate wastes
  34. arousal phase
    parasympathetic control: lubrication (glandular secretion) and erectors (blood vessel dilation in penis & clitoris)
  35. orgasm phase
    sympathetic control. sinal cort mediated reflexes that result in ejaculation of semen and contractions of vaginal & uterine walls
  36. sympathetic tone (vasomotor tone)
    • - keeps blood vessels in a constant state of partial constriction
    • - maintains adequate blood pressure
    • - also allows blood to be shunted away from viscera to skeletal muscle when muscles are vigorously contracting
  37. parasympathetic tone
    • -dominates in the heart and in the smooth muscle of the digestive and urinary tracts
    • - slows the heart (vagal tone) and sets the normal activity levels of digestive & urinary processes
    • (sympathetic can override in cases of stress)

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