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Figure 14.17b

Figure 14.17b. Table 14.5. Figure 14.18. Concept 14.4 Reflexes and SNS Reflex Arcs. Reflexes. somatic reflexes involve contraction of skeletal muscles autonomic reflexes not consciously perceived responses of smooth muscle, cardiac muscle, and glands reflex arc

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Figure 14.17b

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  1. Figure 14.17b

  2. Table 14.5

  3. Figure 14.18

  4. Concept 14.4Reflexesand SNS Reflex Arcs

  5. Reflexes • somatic reflexes involve contraction of skeletal muscles • autonomic reflexes • not consciously perceived • responses of smooth muscle, cardiac muscle, and glands • reflex arc • pathway followed by nerve impulses that produce reflex • may be monosynaptic or polysynaptic

  6. Reflexes • fast involuntary, unplanned sequence of actions that occurs in response to a particular stimulus • some present from birth • some are learned or acquired • cranial reflex • integration occurs in brain • spinal reflex • integration occurs in spinal cord • SNS reflexes are always excitatory

  7. SNS Reflex Arc Components • sensory receptor • dendrite or associated sensory structure • sensory neuron • axon and axon terminals • integrating center • interneuron(s) that relay impulses • motor neuron • impulse triggered by integrating center • effector • body part that responds to impulse

  8. Stretch Reflexes • Triggered by tapping on tendons attached to muscles at elbow, wrist, knee, and ankle joints • Monosynaptic • muscle spindles detect slight stretch • muscle spindle generates impulse(s) to sensory neuron to posterior root of spinal nerve • sensory neuron synapses with motor neuron in gray matter of spinal cord • strong enough impulse triggers AP of motor neuron • ACh at NMJ triggers contraction of skeletal muscle

  9. Figure 14.20

  10. Stretch Reflexes • Monosynaptic reflexes are called ipsilateral reflexes • propagate into and out of the same side of spinal cord • reflex helps prevent injury by preventing overstretching of muscles • reciprocal innervation • polysynaptic reflex arc to antagonistic muscles operates at the same time • three neurons and two synapses

  11. Flexor Reflexes • Triggered by painful AKA withdrawal reflex • Polysynaptic or intersegmental reflex arc • pain-sensitive sensory neuron stimulated • impulse propagates into spinal cord • sensory neuron activated interneuron and signal sent to several segments • several motor neurons activated and motor impulse propagates toward several NMJs • ACh released into synaptic cleft causes flexor muscles to contract withdrawing body part from painful stimulus

  12. Figure 14.21

  13. Flexor Reflexes • reciprocal innervation occurs as in stretch reflex

  14. Concept 14.5ANS Reflexes

  15. ANS versus SNS SNS • produces voluntary movements • in response to consciouslyperceived sensory input ANS • produces involuntary movements in • cardiac muscle • smooth muscle • glands • in response to unconscious sensory input

  16. ANS Reflex Arcs • regulates activity of smooth, cardiac muscle, and many glands • continual flow of nerve impulses from autonomic sensory neurons in visceral organs and blood vessels propagates into integrating centers of CNS • impulses in autonomic motor neurons propagate to various effector tissues • can excite or inhibit activities of effector tissues • ANS activity is regulated by hypothalamus and brain stem of CNS

  17. ANS Divisions sympathetic division parasympathetic division • most organs have dual innervation by both sympathetic and parasympathetic divisions • transmit opposing nerve impulses enteric division • enteric plexuses • network of neurons that extend throughout GI tract walls • contain • sensory neurons • interneurons • motor neurons

  18. Figure 14.22a

  19. Figure 14.22b

  20. Table 14.6

  21. Concept 14.6Anatomy of the ANS

  22. Components of ANS • Preganglionic Neurons • Autonomic Ganglia • Postganglionic Neurons • Effectors

  23. Preganglionic Neurons • cell body in CNS • sympathetic division • in gray matter segments T1-T12, L1 and L2 • parasympathetic division • in nuclei of four cranial nerves in brain stem • in gray matter segments S2-S4 • small-diameter myelinated fiber • extends to an autonomic ganglion • synapses with postganglionic neuron

  24. Figure 14.23

  25. Figure 14.24

  26. Ganglia • Sympathetic ganglia • sympathetic trunk ganglia • vertical row on either side of vertebral column • prevertebral ganglia • celiac ganglion • superior mesenteric ganglion • inferior mesenteric ganglion • Parasympathetic ganglia • terminal ganglia • located close to or actually within wall of visceral organ • longer than most axons of sympathetic preganglionic neurons

  27. Figure 14.25

  28. Autonomic Plexuses • many lie along major arteries • may contain sympathetic ganglia and axons of autonomic sensory neurons • often named after associated artery • thoracic plexuses • cardiac plexus • pulmonary plexus • abdominal and pelvic plexuses • celiac plexus • superior and inferior mesenteric plexus • hypogastric plexus • renal plexus

  29. Figure 14.25

  30. Postganglionic Neurons • Sympathetic neurons connect with postganglionic neurons by • synapse with first ganglion it reaches • may ascent or descent to higher or lower ganglion before synapsing with postganglionic neurons • without synapsing it may continue through sympathetic trunk ganglion • end at prevertebral ganglion • synapse with postganglionic neurons there

  31. Figure 14.26

  32. Postganglionic Neurons Sympathetic effectors • some preganglionic sympathetic axons directly innervate adrenal medullae • each has many axon collaterals • single sympathetic preganglionic fiber may synapse with 20 or more postganglionic neurons • example of divergence • explains why responses affect almost entire body simultaneously Parasympathetic effectors • preganglionic neurons pass to terminal ganglia near or within a visceral effector • can be localized to single effector

  33. Concept 14.7ANS Signal Transmission

  34. ANS Signal Transmission Classification based on neurotransmitter released • Cholinergenic neurons • release acetylcholine • Adrenergenic neurons • release norepinephrine

  35. Cholinergenic neurons • release acetylcholine • preganglionic • both sympathetic and parasympathetic • sympathetic postganglionic that innervate most sweat glands • all parasympathetic postganglionic neurons

  36. Adrenergenic neurons • release norepinephrine • most sympathetic postganglionic neurons • receptors • bind both neurotransmitter norepinephrine and hormone epinephrine • four classifications • alpha 1, alpha 2, beta 1, and beta 2 • alpha 1 and beta 1 are generally excitatory receptors • alpha 2 and beta 2 are generally inhibitory receptors

  37. Figure 14.27a

  38. Figure 14.27b

  39. Figure 14.27c

  40. Table 14.7

  41. Concept 14.8Sympathetic and Parasympathetic Responses

  42. Sympathetic • dominates during extreme physical or emotional stress • favors activities that can support high production of ATP and high physical activity • fight or flight response • pupil dilation • increased heart function • dilation of airways • reduced blood flow to viscera • increased blood flow to heart, skeletal muscles, liver and adipose tissue • increased glycogen and fatty acid breakdown • release of glucose from liver • inhibition of processes not essential for emergency response

  43. Parasympathetic • enhances rest and digest activities • favors activities that can support body functions that conserve and restore energy during times of rest and recovery • SLUDD • salivation • lacrimation • urination • digestion • defecation • three decreases • heart rate • diameter of airways • diameter of pupils

  44. Table 14.9 pt 1

  45. Table 14.9 pt 2

  46. Table 14.8

  47. Concept 14.9ANS Reflex Arcs

  48. Autonomic Reflexes Components: • Receptor • Sensory neuron • Integrating center • Motor Neuron • Effector

  49. Hypothalamus • control and integration center of ANS • receives sensory input regarding • visceral function • olfaction • gustation • blood, temperature, osmolarity, and substance concentration • emotions from limbic system • output via reticular formation to • brain stem • spinal cord • posterior and lateral control sympathetic activities • anterior and medial control parasympathetic activities

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