N165: Quiz 3; Unit 3a

  1. Cutaneous Senses
    perception of touch and pain from stimulation of the skin
  2. Proprioception
    ability to sense position of the body and limbs
  3. Kinesthesis
    ability to sense movement of body and limbs
  4. Skin
    • the largest organ in the body both in surface and in weight.
    • the skin provides many functions, including protection (germs, trauma, UV, toxins), excretion (water, waste products like urea, ammonia, uric acid), endocrine processes (vitamin D production), regulation of body temperature and water loss, and sensation (tactile information).
  5. There are 3 layers of skin
    • epidermis
    • dermis
    • subcutaneous tissue
  6. Epidermis
    The outermost, protective layer of the skin, composed mostly of dead cells
  7. Basement membrane
    • Immediately below the epidermis is the basement membrane, a specialized structure that lies between the epidermis and dermis.
    • It includes various protein structures linking the basal layer of keratinocytes (skin cells) to the basement membrane and the basement membrane to the
    • underlying dermis.
    • Once skin-cancer cells cross this boundary, they can begin to spread through the body through the vascular system of the dermis.
  8. Dermis
    the middle layer of skin below the epidermis that forms the true skin, containing blood capillaries, nerve endings, sweat glands, hair follicles, and other structures
  9. Subcutaneous tissue
    The deepest layer of the skin, made up of vessels, fat, and connective tissue
  10. Hairy skin
    • most of our skin has hair.
    • the primary somatosensory receptor in hairy skin is the follicle receptor, which is a mechanoreceptor triggered by distortion of the hair shaft
  11. Glabrous skin
    • hairless skin (e.g., on palms, soles, lips, labia, penis)
    • contains more specialized types of mechanoreceptors
  12. Mechanoreceptor
    • a sensory receptor that responds to mechanical pressure or distortion (stretching, vibration) via mechanotransduction: movement of the cell membrane physically pulls open/pushes closed ion channels in the memberane, leading to changes in cell signaling.
    • Normally there are four main types in glabrous mammalian skin: Pacinian corpuscles, Meissner's corpuscles, Merkel's discs (also known as Merkel’s receptors), and Ruffini cylinders (also known as Ruffini endings).
    • These differ along several factors, including morphology, skin location, rate of adaption, frequency selectivity, spatial receptive field, and perceptual task.
  13. Slowly adapting fibers (SA)
    • fire continuously as long as pressure is applied to provide detailed/high acuity tactile info
    • found in Merkel’s disks (upper dermis) and Ruffini cylinders (lower dermis)
  14. Rapidly adapting fibers (RA)
    • fire at onset and offset of stimulation to provide info about the start and stop of a sensation
    • found in Meissner’s corpuscles (upper dermis) and Pacinian corpuscles (lower dermis)
  15. Acute nociceptive pain:
    • Part of a rapid warning relay instructing the motor neurons of the central nervous system to minimize detected physical harm. It is mediated by nociceptors, on A-δ and C fibers.
    • These nociceptors are free nerve endings that terminate just below the skin, in
    • tendons, joints, and in body organs. They serve to detect cutaneous pain, somatic pain and visceral pain.
    • Nociceptors (pain sensors) are specialized for heat, chemicals, severe pressure, and cold. Hot and cold sensations are carried via thermoreceptors.
    • Threshold of eliciting receptor response must be balanced to warn of damage but not be affected by normal activity
  16. Chronic inflammatory pain
    • Inflammatory nociceptive pain is associated with tissue damage and the resulting inflammatory process.
    • It is adaptive in that it elicits physiologic responses that promote healing.
  17. Chronic neuropathic pain
    • Neuropathic pain is produced by damage to the neurons in the peripheral and central nervous systems and involves sensitization of these systems.
    • In peripheral sensitization, there is an increase in the stimulation of peripheral nociceptors that amplifies pain signals to the central nervous system.
    • In central sensitization, neurons that originate in the dorsal horn of the spinal cord become hyperstimulated, increasing pain signals to the brain and thereby increasing pain sensation.
  18. Spinal cord
    • a long, thin, tubular bundle of nervous tissue and support cells (like glia) that extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column.
    • The brain and spinal cord together make up the central nervous system (CNS). In contrast to cortex, gray matter is in the inside of the spinal cord (beige butterfly shape in image) and is surrounded by white matter.
    • The spinal cord has three major functions: as a conduit for motor information, which travels down the spinal cord, as a conduit for sensory information in the reverse direction, and finally as a center for coordinating certain reflexes.
  19. Vertebral column
    bony structure made of multiple vertebrae that protects the relatively shorter spinal cord. Spinal nerves project through small openings in the vertebral bones.
  20. Dorsal root ganglion
    • The sensory nerves of the peripheral nervous system have their cell bodies in the dorsal root ganglion (ganglion means a group of cell bodies)
    • These cells have projections (really like dendrites) that carry information from the peripheral sensory receptors –peripheral nerve- and also projections (axons) that carry information into the spinal cord – dorsal root.
  21. Ventral root
    is the motor nerve exiting the spinal cord to innervate muscle fibers.
  22. Fascicle
    A bundle of neuronal axons surrounded by connective tissue; a component of a nerve
  23. Spinal reflex pathway
    • A neural pathway that controls a reflex action (e.g., withdrawal reflex).
    • As most sensory neurons synapse in the spinal cord before going to cortex, spinal motor neurons can be rapidly activated without waiting for signals to go to/come from the brain first.
    • Sensory input is sent to the brain while the reflex is being carried out.
  24. Posterior columns
    • a set of somatosensory white matter tracts in the posterior spinal cord that carry information about fine touch, vibration, pressure, and joint position from the spinal cord to the thalamus (and then to S1).
    • Name turns into ‘medial lemniscus’ when tracts reach the brainstem, where the dorsal root ganglion axons then synapse and cross to opposite side.
    • Organized somatotopically.
  25. Spinocerebellar tract
    • a set of somatosensory white matter tracts in the posterior/lateral spinal cord that carries information about joint position and muscle fiber tension from the spinal cord to the cerebellum
    • projections do NOT cross to opposite side.
    • Organized somatotopically.
  26. Lateral spinothalamic tract
    • a set of somatosensory white matter tracts in the lateral spinal cord that carries information about pain and temperature from the spinal cord to the thalamus
    • dorsal root ganglion axons synapse and cross immediately to opposite side.
    • Organized somatotopically.
  27. Anterior spinothalamic tract
    • a set of somatosensory white matter tracts in the anterior spinal cord that carries information about crude touch and pressure from the spinal cord to the thalamus
    • dorsal root ganglion axons synapse and cross immediately to opposite side.
    • Organized somatotopically.
  28. Thalamus
    The sensory ‘relay station’ in the brain (located subcortically) to which all sensory neuronal pathways project prior to entering cortex, except for those involved in olfaction.
  29. Primary somatosensory cortex (S1)
    • A strip of cortex just posterior to the central sulcus, where the primary control of sensation occurs.
    • S1 contains a somatotopic (bodymap) representation.
    • S2 is the second somatosensory area located just inferior and posterior to S1.
  30. Somatotopy
    is the point-for-point correspondence of an area of the body to a specific point on the central nervous system; somatotopic organization is present in both S1 and M1.
  31. Pain matrix
    • a number of different areas of the brain involved in pain perception.
    • Signals from nociceptors travel up the spinothalamic pathway and activate many of these areas
    • New research demonstrates that S1 and S2 are also directly involved in pain perception.
  32. Tactile agnosia
    • A disorder characterized by the inability to identify by touch an object (or specific characteristics of an object, e.g., weight)
    • possibly caused by damage to S1.
    • Much like visual agnosia, but symptoms now apply to touch.
    • Specific tactile agnosias may also arise from damage to higher-order regions of the somatosensory system, including inability to identify an object’s weight or size (but still identify the object with tactile info).
  33. Cotard syndrome
    • The delusional belief that one is dead, does not exist, is putrefying or has lost his/her blood or internal organs (‘walking corpse syndrome’)
    • paradoxical delusions of immortality may also occur (‘I am dead already, so now I can’t be killed’).
    • Associated with depression, schizophrenia, Capgras syndrome, bipolar disorder, migraine, herpes medication (acyclovir).
    • May arise from a disconnection between high order sensation/face perception(?) and emotional processing of limbic cortex
    • Treatments may include electro-convulsive shock therapy (ECT).
  34. Congenital analgesia (also known as congenital insensitivity to pain (CIP))
    • is a set of rare conditions in which a person cannot feel (and has never felt) physical pain.
    • Condition may be cause by
    • 1) increased endorphins/natural opioids, or
    • 2) mutation in sodium channel in pain receptors. Causes high risk of serious injury, illness, and death.
  35. Insensitivity to pain means
    that the painful stimulus is not even perceived: a patient cannot describe the intensity or type of pain.
  36. Indifference to pain means
    that the patient can perceive the stimulus, but lacks an appropriate response: they do not flinch or withdraw when exposed to pain.
  37. Chronic pain
    • pain that extends beyond the expected period of healing.
    • Affects 1/3 of all Americans, has major impacts on quality of life, and creates a large economic burden on society.
    • Patients are severely undertreated, yet chronic pain affects more people than heart disease, cancer, and diabetes COMBINED.
    • There are affective (mood) and emotional effects on pain perception, but chronic pain is NOT ‘all in the patient’s head.’
  38. Phantom limb syndrome
    • A disorder characterized by having sensations (usually pain) in a limb that is no longer attached to the body
    • mirror therapy or virtual reality may provide some relief.
    • Although phantom pain can be debilitating, the sensation of a phantom limb can actually improve a person’s ability to use a prosthetic.
Card Set
N165: Quiz 3; Unit 3a