Physiology: Autonomic nervous system

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Physiology: Autonomic nervous system
2013-10-16 21:56:30
Lecture 10

L: 10 Autonomic nervous system
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  1. Differences between autonomic and somatic nervous system
    • Somatic
    • One Neuron connects directly to effector
    • Connects only to muscles
    • Only excitatory effects
    • One transmitter
    • Autonomic
    • Two neurons connect to effector
    • Can be a muscle or a gland
    • Can release directly into blood stream (e.g. adrenal medulla)
    • Both inhibitory and excitatory effects (e.g. heart rate)
    • Two neurotransmitters
  2. Overview of ANS - Two Neuron Transmission
    From central nervous system on the preganglionic fiber, to the autonomic ganglion. The preganglionic neurotransmitter is released, and receptors recieve it and sends another AP down the postganglionic fiber; then the varicosity sends out multiple messages, through the postganglionic neurotransmitter to the effector organ
  3. "Fight or flight"
    • Sympathetic system:
    • Pupil dilation
    • Bronchodilation
    • Increased HR and BP
    • Vasoconstriction: GI, skin, brain, periphery
    • Vasodilation: Heart, skeletal muscle, lungs
    • Goosebumps
    • Sweating
  4. Rest and Digest
    • Parasympathetic:
    • Digestion: enzymes, peristalsis
    • Bronchoconstriction
    • Vasodilation in periphery
    • Urination and defecation
    • Salivation
    • Contraction of pupil and lens
    • Resting HR and BP
    • Sexual Arousal
  5. Muscarinic (acetycholine receptors)
    • Inhibitory and excitatory, depending on receptor subtype (M1-5)
    • Target tissue (e.g. Bronchoconstriction (M3), decreased Heart rate (M2)
  6. Nicotinic (Acetylcholine receptors)
    • Excitatory, Fast
    • Postganglionic (sympathetic + parasympathetic)
  7. Norepinephrine receptors
    • Alpha: excitatory (except gut); target effectors
    • Beta 1: inhibitory; target effectors
    • Beta 2: Inhibitory; target effectors
  8. Sympathetic Nervous System
    Spinal cord, to the sympathetic preganglionic fiber.  One goes to the sympathetic postganglionic fiber, which goes to alpha receptors, and beta 1 receptors target organs. Or it can go to the adrenal medulla, which then goes into the blood alpha, beta 1 or beta 2 receptors in the target organs...
  9. Effects of parasympathetic versus sympathetic
    • Parasympathetic:
    • Exocrine gland secretions
    • GI smooth muscle contractions
    • Heart rate
    • Sympathetic: (Muscarinic)
    • Sweating
    • Dilate skeletal muscle blood vessels
    • Sympathetic: (alpha and beta)
    • Splenic contraction
    • Force of cardiac muscle contractions
    • Contraction of GI smooth muscle
    • Constrict peripheral bloodvessels
    • Dilate bronchial airways
  10. Control of autonomic function
    Control of the autonomic nervous system is complex and is accomplished by multiple centers in the brain
  11. Enteric Nervous System
    • Generally functions independently of the sympathetic and parasympathetic but can be influenced by them
    • Contains many neurotransmitters such as 5-HT, substance VIP. Explains why many drugs prescribed for neurological issues have GI side effects
    • Has greater number of neurons than spinal cord.
    • Functions: motility, secretions, fluid regulation, GI blood flow
  12. Organization of Enteric System
    • Serosa: Double membrane lining closed cavities
    • Longitudinal Muscle: Smooth muscle
    • Mycenteric Plexus: Neural controls motility and peristalsis
    • Circular muscle: Smooth muscle
    • Submucosal Plexus: Neural; control ion and water transport
    • Submucosal
    • Mucosal
    • Lumen
  13. The brain in your gut
    The gut's brain, known as the enteric nervous system, is located in sheaths of tissue lining the esophagus, stomach, small intestine and colon
  14. Submucosal plexus
    Layer contains sensory cells that communicate with the myenteric plexus and motor fibers that stimulate the secretion of fluids into the lumen
  15. Myenteric plexus
    Layer contains the neurons responsible for regulating the enzyme output of adjacent organs
  16. Lumen
    No nerves actually enter this area, where digestion occurs.  The brains in the head and gut have to monitor conditions in the lumen across the lining of the bowel.
  17. Messentery
    Attaches the bowel to the body wall and contains major arteries, veins, lymphatic and external nerves.
  18. PNS and SNS control of ENS
    • The PNS generally is stimulatory, increases secretions, motility, and blood flow (rest and digest)
    • The SNS is inhibitory to the ENS reducing secretions and decreasing motility and blood flow.