Ch 13 - 15Anatomy/Physiology

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Ch 13 - 15Anatomy/Physiology
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Ch 13 - 15
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  1. What is the PNS?
    • - all neural structures outside the brain and spinal cord
    • - includes sensory receptors, peripheral nerves, associated ganglia, and motor endings
    • - provides links to and from the external environment
  2. Sensory Receptors
    • - Structures specialized to respond to stimuli
    • - three ways to classify
    • - by stimulus
    • - by location
    • - by structural complexity
  3. Receptor Classification By Stimulus Type
    • 1. Mechanoreceptors - respond to touch, pressure, vibration, stretch, and itch
    • 2. thermoreceptors - sensitive to changes in temperature
    • 3. Photoreceptors - respond to light energy (e.g. retina)
    • 4. Chemoreceptors - respond to chemical (e.g. smell, taste, changes in blood chemistry)
    • 5. Norciceptors - sensitive to pain-causing stimuli
  4. Receptor Classification by Location
    • 1. Exteroceptors
    • - respond to stimuli arising outside the body
    • - found near the body surface
    • - sensitive to touch, pressure, pain, and temperature
    • - include the special sense organs
    • 2. Interoceptors
    • - respond to stimuli arising within the body
    • - found in internal viscera and blood vessels
    • - sensitive to chemical changes, stretch, and temperature changes
    • 3. Proprioceptors
    • - respond to degree of stretch of the organs they occupy
    • - found in skeletal muscles, tendons, joints, ligaments, and connective tissue
    • coverings of bone and muscles
    • - constantly “advise” the brain of one’s movements
  5. Receptor Classification by Structural Complexity
    • - receptors are structurally classified as either simple or complex
    • - most receptors are simple and include encapsulated and unencapsulated varieties
    • - complex receptors are special sense organs
  6. Simple Receptors
    • 1. Encapsulated
    • - free dendritic nerve endings with knob-like swellings
    • - respond chiefly to temperature and pain
    • - merkel (tactile) discs
    • - hair follicle receptors
    • 2. Unencapsulated - enclosed within connective tissue
    • - meissner’s corpuscles
    • - abundant in hairless skin
    • - detect light pressure and discriminative touch
    • - pacinian corpuscles
    • - located deep in skin
    • - deteck deep pressure and high frequency vibration
    • - muscle spindles
    • - located within skeletal muscle and detect stretching
  7. What is Sensation?
    the awareness of changes in the internal and external environment
  8. What is Perception?
    the conscious interpretation of those stimuli
  9. what is a nerve?
    a cordlike organ of the PNS consisting of peripheral axons enclosed by connective tissue
  10. Endoneurium
    loose connective tissue that surrounds axons
  11. Peroneurium
    coarse connective tissue that bundles fibers into faciscles
  12. Epineurium
    touch fibrous sheath around a nerve
  13. Classification of Nerves
    • - sensory and motor divisions
    • - sensory (afferent) - carry impulses to the CNS
    • - motor (efferent) - carry impulses from CNS
    • - mixed - sensory and motor fibers carry impulses to and from CNS; most common type of nerve
  14. What are the four types of mixed nerves?
    • - somatic afferent and somatic efferent
    • - visceral afferent and visceral efferent
  15. What are mixed nerves?
    carry somatic and autonomic (visceral) impulses
  16. Where do peripheral nerves originate?
    From the brain (cranial nerves) and spinal cord (spinal nerves)
  17. Facts about cranial nerves
    • - twelve pairs of cranial nerves arise from the brain
    • - they have sensory, motor, or both sensory and motor functions
    • - each nerve is identified by a number (1 - 12) and a name
    • - first two originate from the forebrain
    • - last ten originate from the brain stem
    • - generally, cranial nerves innervate the head and neck
  18. Cranial Nerve 1
    • Olfactory Nerve
    • - arises from the olfactory epithelium
    • - carries smell to the primary olfactory cortex
    • - afferent only nerve
  19. Cranial Nerve 2
    • Optic Nerve
    • - arises from the retina of the eye
    • - carries visual information to the primary visual cortex
    • - afferent only nerve
  20. Cranial Nerve 3
    • Ocularmotor Nerve
    • - serves the muscles that moves the eye
    • - functions include directing the eyeball, raising the eyelid, controlling lens shape, and constricting the iris.
    • - motor only
  21. Cranial Nerve 4
    • Trochlear Nerve
    • - primarly motor nerve that directs the eyeball
  22. Cranial Nerve 5
    • Trigemial
    • - largest cranial nerve
    • - primary sensory nerve of the face with some motor function
    • - three division: ophthalmic (V1), maxillary (V2), and mandibular (V3)
    • - conveys sensory impulses from various areas of the face (V1 & V2) and supplies motor fibers (V3) for mastation
  23. Cranial Nerve 6
    • Abducens
    • - primary motor nerve innervating the lateral rectus mucles
  24. Cranial Nerve 7
    • - main motor nerve of the face
    • - mixed nerve with five branches: temporal, zygomatic, buccal, mandibular, and cervical
    • - motor functions include
    • facial expression, and the transmittal of autonomic impulses to lacrimal and salivary glands
    • - sensory functions is taste from the anterior two-thirds of the tongue
  25. Cranial Nerve 8
    • Vestibulocochlear
    • - fibers arise from the hearing and equilibrium apparatus of the inner ear
    • - two divisions - cochlear (hearing) and vestibular (balance)
    • - mixed nerve with very little motor functions
  26. Cranial Nerve 9
    • Glossopharyngeal
    • - nerve 9 is a mixed nerve with motor and sensory functions
    • - motor - innervates part of the tongue and pharynx
    • - sensory - fibers conduct taste and general sensory impulses from the tongue and
    • Pharynx
  27. Cranial Nerve 10
    • Vagus
    • - the only cranial nerve that extends beyond the head and neck
    • - the vagus is a mixed nerve
    • - most motor fibers are parasympathetic fibers to the heart, longs, and visceral organs
    • - its sensory function is in taste
  28. Cranial Nerve 11
    • Accessory
    • - travels with the vagus to innervate muscles of the neck, larynx, and pharynx
    • - motor only nerve
  29. Cranial Nerve 12
    • Hypoglossal
    • - innervates both extrinsic and intrinsic muscles of the tongue, which contribute to
    • swallowing and speech
    • - motor only nerve
  30. Spinal Nerves
    • - thirty-one pairs of mixed nerves arise from the spinal cord and supply all parts of the
    • body except the head
    • - they are named according to their point of issue
    • - 8 cervical (C1 - C8)
    • - 12 thoracic (T1 - T12)
    • - 5 lumbar (L1 - L5)
    • - sacral (S1 - S5)
    • - 1 cockerel (Cnot)
  31. Spinal Nerves: Rami
    • - the short spinal nerves (about an inch) branch into two major rami
    • - dorsal ramus
    • - short and extends dorsally
    • - carries both sensory and motor
    • - serves body tissue posterior to spinal cord
    • - ventral ramus
    • - large and extends ventrally
    • - carries both sensory and motor
    • - serves the body tissue anterior to spinal cord
  32. Nerves Plexuses
    • - all ventral rami except T2 - T12 form interlacing nerve networks called plexuses
    • - T1 - T12 form intercostal nerves
    • - plexuses are found in the cervical, brachial, lumbar, and sacral regions
    • - each resulting branch of a plexus contains fibers from several spinal nerves
    • - fibers travel to the periphery via several different routes
    • - each muscles receives a nerve supply from more than one spinal nerve
    • - damage to one spinal segment cannot completely paralyze a muscle
  33. Cervical Plexus
    • - the cervical plexus is formed by ventral rami of C1 - C4
    • - most branches are Cutaneous nerves of the neck, ear, back of head, and shoulders
    • - deep to sternocleidomstoid muscle
    • - the most important nerve of this plexus is the phrenic nerve
  34. Brachial Plexus
    • - formed by C5 - C8 and T1 (C4 and T2 may also contribute to this plexus)
    • - located near the meeting of the shoulder and neck
    • - it gives rise to the nerves that innervate the upper limb
    • - easily damaged by either an inferior jerking force to the arm or a bow to the
    • shoulder that forces the humerus inferiorly
    • - nerves = axillary, musculocutatneous, radial, median, and ulnar
  35. Lumbar Plexus
    • - arises from L1 - L4 and innervates the thigh, abdominal wall, and psoas muscle
    • - anterior to the pelvis
    • - the major nerves are the femoral and the obturator
  36. Sacral Plexus
    • - Arises from L4 - S4 and serves the buttock, lower limb, pelvic structures, and the
    • Perineum
    • - lies posterior to the pelvis
    • - the major nerve is the sciatic, the longest and thickest nerve of the body
    • - the sciatic is actually composed of two nerves: the tibial and the common fibular (peroneal) nerves
  37. Dermatomes
    • - a dermatome is the area of skin innervated by the cutaneous branches of a single
    • spinal nerve
    • - all spinal nerves except C1 participate in dermatomes
    • - illustrated in a striped map of sensory innervation
  38. Regeneration of Nerve Fibers
    • - damage to nerve tissue is serious because mature neurons are amitotic
    • - if the soma of a damaged nerve remains intact, damage can be repaired
    • - regeneration involves coordinated activity among
    • - macrophages - remove debris
    • - Schwann cells - form regeneration tube and secrete growth factors
    • - axons - regenerate damaged part
  39. The ANS consists of motor neurons that...
    • - innervate smooth muscle and cardiac muscle and glands
    • - make adjustments to ensure optimal support for body activities
    • - operate via subconscious control
    • - control centers are the brain stem and hypothalamus
  40. Efferent Pathways
    • - Axons of the ANS are a two-neuron chain
    • - the presynaptic (first) neuron has a lightly myelinated axon
    • - the postsynaptic (second) neuron extends to an effector organ
    • - the cell body is within ganglion (outside CNS)
  41. What are the ANS divisions? What do they do?
    • - ANS Divisions: sympathetic and parasympathetic
    • - the sympathetic mobilizes the body during extreme situations
    • - the parasympathetic performs maintenance activities and conserves body energy
    • - the two divisions counterbalance each other
  42. Structure of Parasympathetic System
    • - long presynaptic neuron
    • - short postsynaptic neuron, very near target tissue
    • - neurons emerge from brain stem and sacral region of the spinal cord
    • - neurons may run within cranial nerves, but never run within spinal nerves
  43. Oculomotor Nerve causes...
    • - causes pupils to constrict and lenses to bulges
    • - modifies vision to focus on near objects
  44. Facial Nerves stimulates...
    • - stimulates glands of the face
    • - nasal, lacrimal, salivary
  45. Glossopharyngeal Nerves stimulates...
    - stimulates the large parotid salivary gland
  46. Vagus Nerve
    • - accounts for about 90% of parasympathetic activity
    • - innervates the abdominal cavity
    • - stomach, liver, kidneys, gallbladder, esophagus, pancreas, small intestine, and
    • proximal half of the large intestine
  47. Splanchnic Nerve
    • - splanchnic nerves run deep to serve organs
    • - innervate distal large intestine, urinary bladder and reproductive organs
  48. Functions of Parasympathetic Divisions
    • - concerned with keeping the body energy use low
    • - involves the D activities - digestion, defecation, and diuresis
    • - resting and digesting
    • - waiting and mating
    • - its activity is illustrated in a person who relaxes after a meal
    • - blood pressure, heart rate, and respiratory rates are low
    • - gastrointestinal tract activity is high
    • - the skin is warm and the pupils are constricted
  49. Neurotransmitters
    • - Ach is released by both presynaptic and postsynaptic neurons
    • - one neurotransmitter, but two different types of receptors
  50. Neurotransmitter Receptors
    • 1. Muscarinic receptors
    • - activated by muscarine
    • - found on target such as smooth muscle, cardiac muscle, and glands
    • - receptor activation can be excitatory or inhibitory
    • 2. Nicotinic receptors
    • - activated by nicotine
    • - found on skeletal muscles, all postsynaptic neurons, and the adrenal medulla
    • - always stimulatory
  51. What is an agonists?
    bind to receptors and stimulate a response
  52. what is an antagonist?
    • - bind to receptor and block a response
    • - also called blockers
  53. Bethanechol
    • - muscarinic receptor agonist
    • - increase intestinal motility
    • - causes bladder muscle to contract and opens the involuntary bladder
    • Sphincter
  54. Atropine
    • - a muscarinic receptor antagonists
    • - slows gut and bladder function
    • - slows the release of body secretions
    • - high dose increases heart rate
  55. Structure of the Sympathetic Division
    • - more developed and complex then parasympathetic branch
    • - uses short presynaptic neurons
    • - emerges from T1 - L2 of spinal cord
    • - leaves the spinal cord in spinal nerves
    • - after leaving spinal nerves, presynaptic neurons synapse in the sympathetic chain
    • - there are 23 ganglia of varying size and shape within each chain
    • - from the chain, postsynaptic neurons travel in the thoracic, lumbar and sacral
    • splanchnic nerves to abdominal organs
  56. Functions of the Sympathetic Division
    • - the sympathetic division is the fight-or-flight system
    • - involves E activities - exercise, excitement, emergency and embarrassment
    • - promotes adjustments during exercise - blood flow to organs is reduced, flow to
    • muscles is increased
    • - its activity is illustrated by a person who is threatened
    • - heart rate increases, and breathing is rapid and deep
    • - the skin is cold and sweaty, and the pupils dilate
  57. Unique effects of the Sympathetic Division
    • - no effect by the parasympathetic branch
    • - increases sweat gland activation
    • - activates adrenal medulla gland
    • - increases cellular metabolic rate
    • - increases lipolysis by fat cells
    • - increases blood sugar via glucose release from the liver
    • - activates RAS (brain becomes more alert)
  58. Neurotransmitter - Sympathetic
    • - presynaptic neurons release ACh
    • - postsynaptic neurons release epinephrine or norepinephrine
    • - these bind to adrenergic receptors
  59. Alpha Receptors
    • - two subtypes
    • - alpha (a 1) receptors are on blood vessels, not on cardiac muscles
    • - alpha (a 2) receptors are on platelets
    • - both types bind epinephrine and norepinephrine equally
  60. Beta Receptors
    • - three subtypes
    • - Beta 1 (b 1) commonly on the heart, blood vessels and kidneys
    • - Beta 2 (b 2) common on lungs and abdominal organs
    • - Beta 3 (b 3) common on adipose tissue
    • - Beta receptors bind epinephrine better than norepinephrine
  61. Propanolol
    • - broad beta receptor antagonist
    • - used to slow heart and treat arrhythmias
    • - however, blocking beta 2 receptors can cause bronchoconstriction
  62. Metoprolol
    • - beta 1 specific antagonist
    • - used to slow heart rate and treat arrhythmias
  63. Albuterol
    • - a beta 2 agonist
    • - used to dilate bronchioles, increases air flow
  64. Doxazosin
    • - an alpha receptor antagonist
    • - relaxes blood vessels, which lowers blood pressure
  65. Ephedrine or phenylephrine
    • - alpha receptor agonists
    • - used to excite the body
    • - found in cold medicines to mask symptoms
  66. Raynaud’s Disease
    • - caused by excessive sympathetic activity
    • - constricts blood vessels, particularly in extremities
    • - causes pain and paleness in the fingers and toes
    • - triggered in response to cold weather and stress
  67. Mental Stress
    • - causes excess sympathetic activity
    • - increases blood pressure
    • - increases brain alertness
    • - inhibits intestinal and breeding functions
  68. Localized vs Diffuse Effects
    • - the parasympathetic division exerts short-lived, highly localized control
    • - the sympathetic division exerts long-lasting, diffuse effects
  69. Referred Pain (Figure 14.8)
    • - pain stimuli arising from the viscera are perceived as somatic in origin
    • - this may be due to the fact that visceral pain afferents travel along the same pathways as somatic pain fibers

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