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266 Cards in this Set
- Front
- Back
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Where does the spinal cord begin in an adult
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Foramen magnum
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Where does the spinal cord terminate in an adult
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conus medullaris, between L1-L2
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How many spinal cord segments are there?
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31
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Where do spinal nerves delineate from?
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A pair of spinal nerves delineate from each of the 31 spinal cord segments
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Where are spinal nerves connected to the spinal cord?
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Posterior (dorsal) and anterior (ventral) roots
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Where does afferent (sensory) information enter the spinal cord?
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Via the posterior roots
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Where does efferent (motor) activity leave the cord?
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Via the anterior roots
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What part of the spinal cord is the butterfly-shaped, central region of the spinal cord?
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The gray matter
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What does the gray matter contain?
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Nerve cell bodies, axons, and synapses
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What spinal cord segments contain the posterior (dorsal) and anterior (ventral) horns
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All segments
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What spinal cord segments contain the lateral horns?
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In segments T1-T12 and L1-L2
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In each segment of the cord how many neurons are in the gray matter?
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Several million
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What types of neurons are contained in the gray matter?
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Sensory relay neurons, anterior motor neurons, and interneurons
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Where are the anterior motor neurons located?
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In the anterior (ventral) horns of the gray matter
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Where do anterior motor neurons leave the spinal cord and where do they innervate?
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They leave the cord via the anterior (ventral) roots and innervate skeletal muscle fibers
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What are the two types of motor neurons?
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Alpha motor neurons and gamma motor neurons
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Are the majority of motor neurons alpha or gamma motor neurons?
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Alpha about 2/3 of total motor neurons
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Where do alpha motor neurons innervate?
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Extrafusal skeletal muscle fibers
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Which neurons have a larger diameter alpha or gamma motor neurons?
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Alpha
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Are alpha and gamma motor neurons mylenated?
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Yes
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What kind of nerve axons do alpha motor neurons give rise to?
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Large A-alpha nerve axons
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What kind of nerve axons do gamma motor neurons give rise to?
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A-gamma axons
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Where do gamma motor neurons innervate?
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Intrafusal fibers in muscle spindles
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Where do motor neurons receive most of its direct input?
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Via Interneurons, they do receive some input directly from sensory neurons
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Where are interneurons present within the gray matter?
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In all areas of the gray matter
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What are the most numerous cell type within the gray matter?
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Interneurons
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Are interneurons in the gray matter excitatory or inhibitory?
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Both
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Where do interneurons synapse?
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With alpha motor neurons
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What does white matter contain?
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Numerous bundles or tracts of nerve axons
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What are 2 examples of ascending tracts in the white matter?
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Lateral spinothalamic tracts and posterior spinothalamic tracts
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What is the principle pathway for transmission of pain and temperature sensations
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Lateral spinothalamic tracts
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What is the principle pathway for transmission of tactile and proprioceptive sensations
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Posterior spinothalamic tracts (dorsal columns)
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What are 2 types of descending nerve tracts?
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Corticospinal (pyramidal) tracts, and nerve tracts associated with the sympathetic nervous system
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What is another name for corticospinal nerve tracts?
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Pyramidal
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Where do corticospinal nerve tracts originate and terminate?
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Originate in the motor cortex and terminate primarily on interneurons in the spinal cord gray matter
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Where do descending nerve tracts associated with the sympathetic nervous system originate and terminate?
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Originate in the brainstem and terminate in the spinal segments T1-T12 and L1-L2
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What are the 3 layers of connective tissue surrounding the cord?
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Pia mater, arachnoid mater, and dura mater
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Where does the dura and arachnoid mater extend to?
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S2
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What does the subarachnoid space contain?
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CSF
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What does the epidural space contain?
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Fat, connective tissue, and venous plexuses
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Where does the epidural space extend to and from?
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From the foramen magnum to the sacral hiatus
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What are the 3 ligaments of the spinal cord from the interior to the exterior?
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Ligamentum flavum (lies just posterior to the epidural space), interspinous ligament, and the supraspinous ligament
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Where does the spinal cord receive its blood supply from?
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the vertebral arteries and the thoracic and abdominal aorta
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What artery supplies the anterior 2/3 of the cord?
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Anterior spinal artery
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Is the anterior spinal artery/arteries a single artery or paired?
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A single midline artery
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Where does the anterior spinal artery originate?
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From the vertebral arteries at the base of the skull
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What blood vessel supplies the posterior 1/3 of the cord?
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The posterior spinal arteries
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Where does the posterior spinal arteries arise from?
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The posterior cerebellar arteries
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What do the radicular arteries supply blood to?
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the anterior and posterior spinal arteries
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What is the Artery of Adamkiewicz?
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Single branch of the aorta that supplies blood flow to the lower thoracic and lumbar cord
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Where does the Artery of Adamkiewicz almost always arise?
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On the left side
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Spinal cord ischemia may result from injury to what artery?
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Artery of Adamkiewicz
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What are some things that cause spinal cord ischemia and what is the result?
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surgical dissection or aortic cross-clamping. paraplegia
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Spinal nerves are formed by joining what 2 things?
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Anterior and posterior roots at each of the spinal cord segments
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Where do spinal nerves exit the vertebral column?
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Opening called the intervertebral foramina
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How many pairs of spinal nerves are there?
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31
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How many cervical nerves are there?
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8
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How many thoracic nerves are there?
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12
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How many lumbar nerves are there?
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5
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How many sacral nerves are there?
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5
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How many coccygeal nerves are there?
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1
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The lower lumbar and sacral nerves descend as the what, before exiting the vertebral column?
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cauda equina
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What kind of nerves are spinal nerves?
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mixed nerves
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What are mixed nerves?
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they contain somatic and autonomic nerve fibers
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Each spinal segment supplies a specific region of what?
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Skin - dermatomone and skeletal muscle
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What are the 2 major branches of spinal nerves?
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Anterior primary division (anterior ramus) and the posterior primary division (posterior ramus)
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What branch of the spinal nerve is the major portion of the spinal nerve?
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The anterior ramus
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What branch of the spinal nerve supplies the muscles of the back and the tissue overlying them
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Posterior ramus
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What is a nerve plexus?
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An intermingling collection of nerves that emanate from different cord segments. They typically contain sensory and motor nerve fibers that innervate a particular region of the body
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What are the 3 main nerve plexuses?
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Cervical plexus, brachial plexus, and the lumbosacral plexus
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What spinal nerves join to form the cervical plexus in the neck?
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The anterior rami of spinal nerves C1-C4
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Peripheral nerves emerging from the cervical plexus supply what?
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skin and muscles of the neck and posterior scalp
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What plexus does the phrenic nerve emerge from and what does it innervate?
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The cervical plexus and innervates the diaphragm
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What spinal nerves join to form the brachial plexus?
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Anterior rami of spinal nerves C5-C8 and T1
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Peripheral nerves emerge from the brachial plexus to innervate what?
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The upper limbs, shoulders, and pectoral muscles
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What are 3 examples of peripheral nerves of the brachial plexus?
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Musculocutaneous, median, ulnar
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What spinal nerves join to form the lumbosacral plexus?
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Anterior rami of spinal nerves L1-L5 and S1-S4
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Peripheral nerves emerge from the lumbosacral plexus to innervate what?
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Lower limbs and pelvis
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What are 3 examples of peripheral nerves of the lumbosacral plexus?
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obtrurator, femoral, and sciatic
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What is another name for muscle receptors?
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proprioceptors
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What are muscle receptors?
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They provide continuous feedback information to the CNS with respect to muscle length and tension, and the rates of change of muscle length and tension during movement
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Where is feedback information from muscle receptors directed?
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The spinal cord, cerebellum, and motor cortex
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What are 2 types of muscle receptors?
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Muscle spindles and Golgi tendon organs
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Where are muscle spindles located?
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Distributed within skeletal muscle
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What is the function of muscle spindles?
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Function as stretch receptors and detect changes in muscle length
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What is each muscle spindle made up of?
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Several intrafusal muscle fibers
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Where are muscle spindles attached?
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To the glycocalyx of surrounding extrafusal fibers
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What is the central region of the muscle spindle innervated by?
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Sensory nerves types Ia and II.
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The central region of the muscle spindle is extremely sensitive to what?
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stretch of the muscle
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The end portions of the intrafusal fibers of the muscle spindle contain what?
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Actin and myosin
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What are the end portions of the intrafusal fibers of the muscle spindles innervated by and what do they regulate?
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A-gamma motor fibers which regulate the tension in the intrafusal fibers and thus the sensitivity of the spindles to stretch
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Where are golgi tendon organs located?
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In the muscle tendons near the point of attachment of the tendons to the skeletal muscle fibers
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What are golgi tendon organs?
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Sensory receptors/nerve endings
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What are the golgi tendon organs sensitive to?
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Tension development within the muscle
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What type of sensory nerves transmit information from the Golgi tendons to the CNS?
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Type Ib
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Where are the signals of the Type Ib sensory nerves from the golgi tendon organs directed?
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Spinal cord, cerebellum, and cerebral cortex
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What type of reflex is the stretch reflex?
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monosynaptic reflex with very little delay
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What is another name for the stretch reflex?
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Myotatic
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Explain the sequence of events with the stretch reflex
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Stretch activates muscle spindles, sensory info delivered via type Ia sensory fibers to dorsal root of spinal cord and form there to alpha motor neurons, activation of alpha motor neurons that innervate the same muscle that was stretched, muscle contraction to oppose stretch
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What is an example of the stretch reflex?
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Knee-jerk reflex
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What is the flexor reflex most often stimulated by?
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A painful stimulus
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What is another name for the flexor reflex?
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Withdrawl
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What type of reflex is the flexor reflex?
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Poly-synaptic reflex
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What is the sequence of events for the flexor reflex?
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Activation of sensory receptor, info is directed to interneurons in spinal cord, excitation of alpha motor neurons that innervate appropriate flexor muscles, contraction of flexor muscles to remove affected body area from painful stimuli
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What is crossed extension?
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When flexion of one limb is accompanied by extension of the opposite limb. Delayed reflex 200-500 msec
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When does crossed extension occur?
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Occurs during flexor response to painful stimulus. when you have flexion in response to the painful stimulus you get extension on the opposite side to maintain equilibrium
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What represents a reflex response to irritation of the muscle?
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muscle spasms
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What are some examples of insults that can result in spinal cord injury?
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Trauma, degenerative and demyelinating disorders, tumors, infections, and ischemia
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What happens initially after a spinal cord transection?
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Initial period of spinal shock - somatic and autonomic reflexes below the lesion are temporarily interrupted; BP can fall precipitously but recovers within a few days
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Several weeks after a spinal cord transection what happens to spinal neurons below the lesion?
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Regain excitability and at least some reflex activity. Loss of sensation and voluntary movement below transection is permanent
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What is autonomic hyperreflexia and when is is commonly seen?
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Overactivity of the sympathetic nervous system. Typically seen in patients with cord transection at T5 or above (unusual below T10)
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What type of stimuli can trigger a strong autonomic responses in autonomic hyperreflexia?
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Cutaneous and visceral stimulation below the level of transection
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What happens in autonomic hyperreflexia?
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Sympathetic discharge - vasoconstriction below the lesion
Reflex brady and vasodilatation occur above the lesion Hypertension results Cardiac dysrhythmias may occur |
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In a spinal block where are local anesthetics injected?
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the subarachnoid space of the spinal cord
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Where is a spinal block usually performed?
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Below the end of the spinal cord - at L3-L4 or L4-L5
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Where is the main site of action with spinal blocks?
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Spinal nerve roots
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What 3 things allow uptake of local anesthetics in a spinal block?
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Spinal nerve roots, dorsal root ganglia, and the spinal cord itself
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Does CSF circulation affect distribution of the drug with a spinal block?
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No
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What are 2 complications of a spinal block?
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Hypotension - venous pooling, decreased venous return and CO
Postspinal headache - CSF leakage - tension in the meninges |
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What is an epidural block?
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Placement of local anesthetics into the epidural space of the spinal cord
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What level is the epidural block done at?
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Typically the lumbar level
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What does the epidural space of the spinal cord contain?
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Fat, connective tissue, and venous plexuses - does not have free-moving fluid
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What is the major site of action with an epidural block?
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The spinal nerve roots
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Is onset of sympathetic blockade slower or faster with an epidural vs a spinal?
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Slower with an epidural so you don't see the abrupt fall in BP (hypotension still a potential complication though)
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When does sensation begin?
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When a stimulus is detected by a specific sensory receptor
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A sensory receptor is usually what?
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A sensory nerve ending
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A sensory nerve ending acts as a transducer, converting the natural form of the stimulus into what?
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Electrical impulses/action potentials ,which are necessary for the nervous system to process the sensory event
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A stimulus causes a change in membrane permeability of the receptor, causing what?
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depolarization/receptor potential
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The magnitude of receptor potential is determined by what?
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The stimulus strength or intensity
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What is receptor potential analogous to in the CNS?
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The excitatory postsynaptic potential in the CNS
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The frequency of action potentials produced by the receptor is proportional to what?
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The magnitude of the receptor potential
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All sensory receptors have what?
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A receptive field/an area over which the receptor will detect a stimulus
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What allow for very precise localization of a stimulus?
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Adjacent receptive fields have extensive overlap
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Do sensory receptors show adaptation to a stimulus?
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Yes, all sensory receptors show some degree of adaptation to a stimulus
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What are 5 types of sensory receptors?
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1. Mechanoreceptors
2. Thermoreceptors 3. Nociceptors 4. Electromagnetic receptors 5. Chemoreceptors |
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What are mechanoreceptors?
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Detect mechanical deformation of tissue
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What are thermoreceptors?
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Detect changes in tissue temperature
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What are nociceptors?
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Detect tissue injury
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What are electromagnetic receptors?
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Detect light waves
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What are chemoreceptors?
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Detect changes in the chemical composition of the local environment
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In the general classification system what are the 2 different classifications?
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Type A - myelinated, subgroups: alpha, beta, gamma, and delta
Type C - small diameter and nonmyelinated (low conduction velocity) |
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In the general classification system what sensory nerve classification comprises more than 50% of somatic sensory nerves?
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Type C
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In the sensory classification system what are the 5 classifications?
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Group Ia - muscle spindles
Group Ib - Golgi tendon organs Group II - muscle spindles and most tactile receptors Group III - thermoreceptors and some nociceptors (fast pain) Group IV - thermoreceptors and some nociceptors (slow pain) |
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What are the 2 main types of sensory modalities?
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Special senses and somatic sensations
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What are the "special" senses?
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Vision, hearing, taste, smell, and equilibrium
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Where do somatic sensations arise from?
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The body surface and from deep tissues such as viscera, muscles, and bone
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What are 5 different somatic sensations?
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1. Tactile sensations
2. Proprioceptive sensations - limb position and joint angle 3. Kinesthesis - body and limb movements 4. Temperature 5. Pain |
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What are tactile sensations?
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Touch, pressure, vibration
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What type of sensory receptor is for tactile sensation?
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Mechanoreceptors
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What are the 6 types of mechanoreceptors for tactile sensation?
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1. Free nerve endings
2. Meissner's corpuscles 3. Merkel's discs 4. Ruffini end-organs 5. Pacinian corpsucles 6. hair end-organs |
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Where are free nerve ending found and what do they detect?
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Found extensively in the skin and detect touch and pressure (also found in the cornea)
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Are free nerve endings encapsulated?
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No
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Where are meissner's corpuscles found and what are they important for?
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Found in the skin, important for discriminative touch and recognition of texture of an object
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To what degree do Meissner's corpuscles adapt?
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Adapt rapidly
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Are Meissner's corpuscles encapsulated?
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Yes
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Where are Merkel's discs located and what do they transmit?
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Located in the skin and transmit information regarding continuous touch
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Are Merkel's discs encapsulated?
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Yes
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To what degree to Merkel's discs adapt?
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Adapt slowly
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Where are Ruffini end-organs found and what are they important for?
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Found in deeper skin layers and in deeper tissues, important for signaling continuous tissue deformation and pressure
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Are Ruffini end-organs encapsulated?
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yes
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To what degree to Ruffini end-organs adapt?
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Very little
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Where are Pacinian corpuscles found and what are they for?
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Found in the skin and deep fascia, vibration receptors
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To what degree do Pacinian corpuscles adapt?
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They adapt very rapidly
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Where are hair end-organs and what are they a receptor for?
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Nerve fibers associated with base of hair, they are touch receptors - movement of hair activates the nerve ending
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To what degree do hair end-organs adapt?
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Adapt rapidly
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Signals from most tactile sensory receptors are transmitted to the CNS via what type of axon?
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Large, myelinated A-beta (group II) axons
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Signals from free nerve endings are transmitted to the CNA via what type of axons?
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myelinated A-delta axons and nonmyelinated type C axons
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Sensory information enters the spinal cord via what?
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The dorsal roots
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After entering the spinal cord sensory information is directed to the brain via what?
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The dorsal columns
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What happens to a sensory nerve axon after it enters the cord?
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It branches.
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When a sensory nerve signal ascends to the brain where do the ascending axons synapse?
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In the dorsal column nuclei in the MEDULLA
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After ascending axons synapse in the medulla what happens?
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Second-order nerve axons immediately cross over (decussate) and pass upward to the thalamus
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What pathway do second order neurons use to cross over in the medulla?
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The medial lemniscus pathway
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At what level in the CNS do tactile signals cross over and via what pathway?
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The medulla via the medial lemniscus pathway
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What do axons in the medial lemniscus pathway synapse with and where?
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With specific sensory relay nuclei in the thalamus
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Third order nerve axons transmitting tactile signals project from sensory relay nuclei to where?
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The somatic sensory cortex
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when sensory nerve axons branch after entering the cord where do tactile signal go? Describe the entire pathway
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Ascend via the dorsal column and synapse with dorsal column nuclei in the medulla, second order neurons cross over via the medial lemniscus pathway and ascend to the thalamus, 3rd order axons project from nuclei in the thalamus to the somatic sensory cortex
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The representation of body receptive fields is preserved where?
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Within the dorsal column-lemniscal system as it proceeds upward to the thalamus
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What is faithfulness of transmission?
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The intensity of a signal as it travels to the cerebral cortex is preserved
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Where is the somatic sensory cortex?
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In the anterior portion of each parietal lobe
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What 2 areas of the somatic sensory cortex are involved?
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SS area II and SS area II
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Where is the somatic sensory area I?
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located in the post central gyrus
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What exists within SS area I?
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A distinct organization of body areas
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What is the sensory homunculus?
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In SS area I The areas of the body are represented according to the density of their somatic sensory receptors
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What areas of the body are highly represented in the sensory homunculus?
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The lips, face, and hands
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What areas of the body have a small representation relative to their actual body sizes in the sensory homunculus?
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The trunk and lower parts of the body
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How are neurons of the somatic sensory cortex arranged?
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In columns 0.3-0.5mm in diameter. They extend through all 6 layers of the cortex
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Each column in the somatic sensory cortex contains how many neurons and responds to what?
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10,000 and responds to a specific sensory modality
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What can injury to the SS I cause
|
Loss of discrete touch
Inability to judge the shapes of objects Inability to judge texture of an object Inability to judge pressure against the body surface |
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Where is the somatic association cortex located and where does it receive input from?
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Located in the parietal lobe behind SS I and receives input from SSI, the thalamus, the visual cortex, and the auditory cortex
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What does the somatic association cortex play an important role in?
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the interpretation of sensory information
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Damage to the somatic association cortex in the nondominant parietal lobe can cause what?
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Loss of sense of body form - amorphosynthesis (forgetting that one side of the body exists)
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What are proprioceptive sensations?
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Limb position and kinesthesis
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Where are proprioceptive sensation receptors?
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In the joint capsules and ligaments, in tissue around the joints, and in muscle spindles
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What are 2 joint capsule and ligament receptors?
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Ruffini end-organs
Golgi tendon receptors |
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Transmission of proprioceptive sensory information to the somatic sensory cortex occurs via what?
|
The dorsal column-lemniscal system
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What is pain?
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an unpleasant sensory and emotional experience associated with actual or potential tissue damage
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Pain is an experience affected by what?
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Past events, suggestion, and emotional arousal
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What part of the brain is critical in the arousal of pain?
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The limbic system
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What are the 2 types of pain?
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Fast and slow pain
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Fast pain is also referred to as what?
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Acute pain, sharp pain, pricking pain
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What is the onset of fast pain?
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0.1 sec
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Where does fast pain typically arise from?
|
In skin, generally not felt in deeper tissue
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What type of pain is well localized?
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Fast pain
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For fast pain signals are transmitted to the spinal cord via what tips of nerve axon?
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Myelinated type A-delta sensory nerve axons
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What is slow pain also referred to as?
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Throbbing, burning, aching, chronic pain
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What is the onset of slow pain?
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1 sec or more
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What type of pain sensation can increase with time?
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Slow pain
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Where does slow pain arise from?
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in skin and deeper tissues - poorly localized
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Slow pain signals are transmitted to the spinal cord via what type of nerve axon?
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Non-myelinated type C
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What is sensitization?
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The sensation of pain can increase with time - slow pain
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The majority of nociceptors are what?
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Free nerve endings - not encapsulated
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What type of stimuli do nociceptors respond to?
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mechanical, thermal, and chemical alogens (stimuli) - polymodal
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What are the 2 main location categories of nociceptors?
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Somatic and visceral nociceptors
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Where are somatic nociceptors?
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In the skin and deep tissues
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Where are visceral nociceptors?
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GI tract, kidneys...
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What is hyperalgesia?
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When persistent stimulation of pain receptors increase their sensitivity
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Do all pain receptors show adaptation?
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No, some show little or no adaptation
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Where do A-delta axons synapse?
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With second-order neurons, primarily in laminae I and V of the spinal cord gray matter
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Where do type C axons synapse?
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Primarily with interneurons in laminae II (substantia gelatinosa) and III of the spinal cord gray matter
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After type C axons synapse with interneurons where is the information directed?
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To second-order neurons in lamina V
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Does all slow pain synapse in the substantia gelatinosa?
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No, some synapse directly with second-order neurons in lamina V
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Where in the gray matter does all pain eventually synapse?
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In lamina V - Wide dynamic Range
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Where are 2nd order neurons most abundant?
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In lamina V
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What is significant about the second-order neurons in lamina V?
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These neurons increase their firing rate exponentially in response to persistent pain stimulus ("wind up")
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Where does pain stimuli crossover?
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At the level of the cord.
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Second order neurons immediately cross over to the opposite side of the cord and ascend in what?
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The lateral spinothalamic tracts
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Where is fast pain directed in the brain?
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Primarily to the ventrobasal nuclei of the thalamus and from there via 3rd-order neurons to the somatic sensory cortex
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Where is slow pain directed in the brain?
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Primarily to the midbrain reticular formation, the periaquaductal gray area, intralaminar nuclei of the thalamus, and the limbic system
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What type of pain projects to lower areas of the brain?
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Slow pain
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Chemical mediators of pain are called what?
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allogens
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What are the 2 types of pain sensitization?
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Peripheral sensitization and central sensitization
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What allogens are released from injured tissue and tissue mast cells?
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Bradykinin and prostaglandin E2, and K+, H+, and histamine
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Persistent release of alogens in response to tissue injury can cause what?
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enhanced excitability of nociceptors, or primary hyperalgesia (exaggerated pain response at the site of injury)
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Local collateral axons of pain afferent nerves release what? and what does this release stimulate?
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Releases substance P which stimulates mast cells and platelets to release alogens such as histamine and serotonin that cause primary hyperalgesia
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Spread of alogens to tissue surrounding the area of injury contributes to what?
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secondary hyperalgesia
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What is secondary hyperalgesia?
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Exaggerated pain caused by stimuli outside of the area of injury
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What do afferent pain fibers release in the dorsal horn?
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glutamate and substance P
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What post-synaptic receptors does glutamate activate?
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AMPA and NMDA
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What post-synaptic receptors does substance P activate?
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NK-1
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Where does central sensitization of second order neurons most often occur?
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WDR neurons
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What is the common mechanism of central sensitization?
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Increased intracellular calcium
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What causes increased Ca++ permeability on the second order neuron?
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Glutamate binds to the NMDA receptor which causes removal of a Mg++ block and increased Ca++ permeability
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What does central sensitization greatly enhance?
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Pain transmission and pain perception in the CNS and contributes to secondary hyperalgesia
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Once _______ is established it is very difficult to interrupt pain transmission and perception in the CNS, even with opioids.
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Central sensitization
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Where is the Periaqueductal gray area and what does it receive?
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upper pons and midbrain surrounding the aqueduct of Sylvius), it receives ascending pain activity
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What does the Periaqueductal gray area activate?
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Descending adrenergic tracts to the spinal cord and descending enkephalin-secreting tracts to the raphe magnus nucleus in the upper medulla and lower pons
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What does the Raphe magnus nucleus activate?
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Descending serotoninergic tracts to the spinal cord gray matter
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Descending adrenergic axons release what neurotransmitter and activates what?
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Norepinephrine and activates presynaptic and postsynaptic alpha-2 receptors which inhibit pain transmission
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What do descending serotoninergic axons stimulate release of?
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Stimulate interneurons to release enkephalins which bind to presynaptic opioid receptors on pain afferents and inhibit substance P release - inhibits pain transmission
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What 2 descending pathways converge in the gray matter of the spinal cord and inhibit pain transmission?
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The descending adrenergic axons and serotoninergic axons
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Release of endorphins in the peraquductal gray area and limbic system does what?
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Interferes with pain transmission and modulation of pain perception
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What are 2 endogenous opioids?
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Endorphins and enkephalins
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What 2 endogenous opioids are released in the peraqueductal gray area and limbic system in response to pain?
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Beta-endorphin and dynorphin - both endorphins
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What 2 endogenous opioids are released in the spinal cord to inhibit pain transmission?
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Met-enkephalin and leu-enkephalin
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Pain perceived in a part of the body that is removed from the actual site of painful stimulus is called what?
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Referred pain
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With referred pain, pain typically originates and terminates where?
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Originates in the viscera and referred to the body surface
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What is the possible mechanism for referred pain?
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Visceral pain fibers synapse in the spinal cord with the same neurons (second-order and interneurons) that receive pain afferent fibers from the body surface
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What type of somatic sensory receptors does the viscera contain?
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Just pain receptors which are sparsely distributed
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Does highly localized tissue damage cause a lot or little pain? And why?
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Little because pain receptors in the viscera are sparsely distributed
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Visceral pain typically involves what?
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Diffuse activation of pain receptors d/t ischemia, chemical irruption, distension/spasm of visceral smooth muscle, and stretching of ligaments
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Visceral pain is transmitted to the CNS via what type of sensory fiber?
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Autonomic type C
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Visceral pain is typically referred where?
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To a particular body area
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What is parietal pain?
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When injury to a visceral organ affects the parietal wall overlying the organ
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Parietal pain is transmitted to the spinal cord via what?
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Somatic sensory nerves
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Where is parietal pain sensation localized?
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to the area directly over the painful stimulus
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