Neuro-sensory function Flashcards
The somatosensory system
afferent vs efferent
first second third order neurons
provides the CNS with information on touch, temperature, body position and pain.
• General somatic afferent neurons have branches distributed throughout the body with distinct types of receptors for sensations including pain, touch, and temperature.
• Special somatic afferent neurons have receptors located primarily in muscles, tendons, and joints. Sense position and movement changes.
• General visceral afferent neurons have receptors on various visceral structures that sense fullness and discomfort
• Sensory systems can be conceptualized as a serial succession of neurons consisting of first-, second-, and third-order neurons.
• Fig. 14-1, p. 344
• First order neurons transmit sensory information from the periphery to the CNS
• Second order neurons communicate with various reflex networks and sensory pathways in the spinal cord and travel directly to the thalamus.
• Third order neurons relay information from the thalamus to the cerebral cortex.
Pain (sensory vs perception)
- Pain is viewed in context of the injury, both sensory and perception
- Sensory = the process by which the person experiences the pain
- Perception = influence by endogenous analgesia system that modulates the sensation of pain (not feeling gunshot wound until out of the situation)
- Fig. 14-7, p. 351
- Mechanism of acute pain. Tissue injury leads to release of inflammatory mediators with
Components of nociceptive pain
activated by injury to peripheral tissues
• Pain receptors (nociceptors) – nerve endings in afferent nervous system that respond to stimulation
• They are not evenly distributed in the body so pain will vary in different areas of the body
• Afferent nociceptor pathways: carry impulses from peripheral nerves to the spinal cord and CNS
o Myelinated A-delta fibers: fast wave, ex burn
o Unmyelinated C fibers: slow wave, dull aching pain
• Efferent nociceptor pathways: carry impulse from CNS to the spinal cord–to localize pain
Nociceptive pain process
noxious stimuli through a normally functioning nervous system:
o Figure 14-9, p. 354
o Pain transduction: exposure to a stimuli
o Pain transmission: mediated by neurotransmitters
o Pain perception
o Pain threshold vs. tolerance
o Pain threshold-amount of time elapsed before person reports painful stimuli
o Pain tolerance-duration of time before the individual can no longer tolerate the painful stimulus
As pain threshold increases pain tolerance increases
o Pain modulation is the increase or decrease in pain
o Neuromodulators
o Excitatory neuromodulators
o Inhibitory neuromodulators
Types of pain
- Cutaneous pain-superficial
- Deep somatic pain-tendons, bones, joints, muscles
- Visceral pain-pelvis abd cavity
- Referred Fig. 14-11, p. 356
- Acute and chronic pain – Table 14-1, p. 355
Pain sensitivity alterations
- Hyperalgesia-increased sensitivity to pain
- Hypoalgesia-decreases sensitivity to pain
- Allodynia- nerve pain (pain from a stimulus that does not normally cause pain, ex light feather touch)
Neuropathic pain
- Neuralgia-intense typically intermittent pain along the course of a nerve, especially in head and face
- Phantom limb pain- pain in a limb that is no longer there
Headache ( 3 types)
-Migraine Etiology/Pathophysiology may include: Trigeminal nerve activation Neurogenic vasodilation Hormonal fluctuations -Tension-type headache -Temporomandibular joint pain
Pain by age
- Neonates- lower threshold
- Children- will remember pain
- Older adults – increased incidence of pain
Disorders of Vision
• Conjunctivitis-inflammation of the conjunctiva of the eye (‘Pink Eye’
o Viral
o Bacterial
Disorders of the Lens
• Disorders of refraction – Fig. 19-11, p. 493
o Myopia: near sightedness; can’t see far away.
o Hyperopia: farsightedness; can’t see up close
o Astigmatism: a defect in the eye or lens caused by deviation from spherical curvature, that results in distorted images
o Etiology
o Pathophysiology: error in the shape of the cornea, lens has an irregular curve. Changes the way light comes in
o Manifestations: blurry, fuzzy, distorted vision
Disorders of the retina
Retinopathies (Fig. 10-18 diabetic retinopathy):
Retinal detachment: Fig. 19-19, p. 502): tear in the retina with fluid accumulation; floaters
Macular degeneration – Fig. 19-20, p. 503: seen with aging, obesity, smoke-degeneration of the macula; blurred vision, blind spot
Disorders of intraocular pressure
Open-angle glaucoma: increased in ocular fluid pressure
Angle-closure glaucoma: obstruction of aqueous flow; builds up pressure
Infantile glaucoma: glaucoma with onset in the first years of life. incorrect development of eye drainage system
Disorders of neural pathways and cortical centers
Hemianopia: vision loss in half of your vision field (one eye)
Scotoma: partial vision loss in an otherwise normal vision field
Disorders of eye movement
Strabismus: abnormal alignment of the eyes; the condition of having squint
Amblyopia: impaired or dim vision without obvious defect or change in the eye
Eyelid ptosis: abnormal low-lying or drooping upper eyelid
