Download Chapter 7 - Psychology

Chapter 7 Understanding Pain
congenital insensitivity - a very rare genetic disorder that prevents one from
experiencing any pain at all. While it may sound good, the consequences are
very serious.
somatosensory system - The part of the nervous system that carries sensory
information from various parts of the body (e.g., from the skin and muscles) to
the brain.
afferent neurons - are also called sensory neurons. They relay information from
the sense organs (e.g., touch) toward the brain.
efferent neurons - are also called motor neurons. They carry neural impulses
from the brain to the muscles.
primary afferents - Are specialized sensory neurons in the skin and other
places. They respond to physical energy (e.g., touch) and convert it to neural
signals that travel to the spinal cord and brain.
action potential - is the technical term for when a neuron "fires." In response to
sufficient amounts of neurotransmitters, or physical stimulation (for the primary
afferents), a signal travels down the neuron's axon and causes release of
neurotransmitters.
nocioception - is the process of perceiving pain.
nociceptors - Sensory receptors in the skin and organs that
are capable of responding to various types of stimulation that may cause tissue
damage (heat, cold, cutting, or burning).
myelin - A fatty substance that acts as insulation for the axons of some neurons.
Neural impulses are transmitted much faster by neurons with myelinated axons.
fiber size - larger fibers (of larger neurons) transmit messages faster than
smaller fibers. A fiber is basically the same thing as an "axon."
A beta fibers - are both large and myelinated. They transmit information "100
times faster" than C fibers. They rapidly transmit sensory information.
A-delta fibers - are small sensory fibers that are involved in the experience of
“fast” pain that is "sharp" or "pricking."
C fibers - are smaller and unmyelinated. Their slower transmission results in
sensations that are dull, aching, or lingering. About 60% of all sensory afferents
are "C fibers."
nerve - A group or bundle of fibers (axons) that travel together (like a large
electrical cable made up of hundreds of wires). Some nerves (afferent and
efferent) are referred to as "Tracts."
the cranial Nerves - Sensory information from the head and neck area travel to
the brain via "12 cranial nerves." Information from all other body areas travels to
the brain via the spinal cord.
spinal cord - carries afferent (sensory) information to the brain and efferent
(motor) information from the brain to the muscles (see Figure).
dorsal horns - The back part of the spinal cord (away from the stomach) that
receives sensory input (via the sensory tracts). There, the sensory fibers
connect to small "secondary afferents" which, in turn, connect to efferent (motor)
fibers that leave the ventral (front) side of the spinal cord. The messages also
travel up the spinal cord via other neurons to the brain.
transmission cells - "secondary afferents" and "interneurons" are all different
names for the same thing, cells that connect neurons to other neurons.
laminae - Are different layers of the dorsal horns which are composed of cell
bodies.
substantia gelatinosa - Is made up of layers 1 and 2 of the dorsal horns and is
important in modulating sensory input.
thalamus - Structure in the forebrain that acts as a relay center for incoming
sensory information and outgoing motor information (from and to the spinal cord).
somatosensory cortex - The part of the brain that receives and processes
sensory input from the body.
primary somatosensory cortex - receives information from the thalamus that
allows the entire surface of the skin to be mapped onto the somatosensory
cortex. The more sensitive areas of the skin (face and lips) take up a much
larger part of the cortex relative to less sensitive parts like the back (see Figure).
emotional and physical pain - May be all the same to the brain. Eisenberg et.
al. (2003) found that experimentally induced emotional pain (social rejection) had
the same activating effect on certain brain areas as physical pain.
endorphins - Along with the enkephalins and dynorphin are naturally occurring
neurochemicals whose pain lowering effects resemble those of the opiates.
glutamate and substance p - Are neurotransmitters that sensitize (or excite) the
neurons that relay pain messages.
periaqueductal gray - An area of the midbrain that, when stimulated, decreases
pain. It sends signals, via the medula, to the substantia gelatinosa in the spine's
dorsal horn. Endorphin release blocks pain transmission (see Figure)
medulla - The structure of the hindbrain just above the spinal cord. Sensory and
motor messages travel through it.
how pain is viewed - Prior to about 1900, pain was thought to be directly
proportional to the extent of tissue damage. C. A. Strong then proposed that the
experience of pain reflected BOTH sensory information AND the person's
interpretation of it.
the IASP definition of pain - The international Association for the Study of Pain
(IASP) defined pain as "an unpleasant sensory and emotional experience
associated with actual or potential tissue damage, or described in terms of such
damage."
acute pain - Short-term pain that results from tissue damage or other trauma
(e.g., burns, surgery, dental work, childbirth).
chronic pain - Pain that endures beyond the time of normal time of healing, it is
frequently experienced in the absence of detectable tissue damage.
prechronic pain - Pain that endures beyond the acute phase but has not yet
become chronic. This is the "most crucial stage of pain" because if the person
does not overcome or adjust to the pain now, it may become chronic and be
accompanied by feelings of hopelessness.
chronic recurrent pain - Refers to alternating episodes of intense pain and no
pain.
the experience of pain - Henry Beecher (1946, 1956) suggested that "the
intensity of suffering is largely determined by what the pain means to the patient."
He observed that some wounded WW II soldiers didn't mind the pain that much
because it removed them from the chance of further injury or death.
conditioning - Both classical and operant, plays a role in pain. For many, the
sound of the dentist's drill has been "classically conditioned" as a stimulus that
predicts pain. Person's who receive sympathy and are released from work or
other responsibilities because of their illness may develop chronic pain because
their "pain" behaviors are being reinforced by "operant conditioning."
the "pain resistant personality" - Does NOT exist according to our authors.
They do suggest that there are "cultural differences" in how people respond to
pain.
anxiety, worry, and negative outlook - have been associated with heightened
sensitivity to pain. Chronic pain sufferers do have higher levels of anxiety and
depression BUT cause and effect is hard to determine.
specificity theory of pain - An early theory suggesting that specific pain fibers
and pathways exist. Thus, pain would be equal and proportional to the amount
of tissue damage. The theory is now viewed as being "incorrect."
gate control theory of pain - A theory of pain holding that structures in the
spinal cord (e.g., the substantia gelatinosa) act as a gate for sensory input that is
interpreted as pain. In general, A beta and C fibers open the gate (more pain). A
delta fibers close the gate (less pain) (see Figure)
central control trigger - Proposed by Melzack and Wall, "cognitive processes"
such as beliefs and prior experiences trigger nerve impulses that descend from
the brain and influences the perception of pain.
measurement of pain - Researchers have developed three types of
measurement: (1) self-report ratings, (2) behavioral assessments, and (3)
physiological measures.
visual analogue scale (VAS) - Is a self-report rating scale in which patients
mark a point on a line (no pain at one end, worst possible pain at the other) and
the line length from no pain to the marked point is measured. Research has
showed the VAS as superior to word descriptors and numerical scales.
McGill Pain Questionnaire - Consists of several sections and is currently the
most widely used pain questionnaire.
the "neurotic triad" - is a personality "profile" on the Minnesota Multiphasic
Personality Inventory (MMPI) that has been consistently associated with reported
pain (high hypochondriasis, depression, and hysteria scores).
Electromyography (EMG) - Measures muscle tension and has been used to
asses back, neck, and jaw pain. However, reports of pain and EMG levels are
not consistent so it may NOT be a very good assessment of pain.
syndrome - Is a set of symptoms that occur together and characterize a
condition. Headaches are the most common pain syndrome.
migraine headaches - Involve blood flow, originate in the brainstem, may be
partially genetic in cause, have a rapid onset, and affect one side of the head.
Some experience an "aura" (sensory disturbance) before onset. More common
among women by two to three times.
tension headaches - Are caused by sustained muscle contractions in the neck,
shoulders, scalp, and face. Onset is gradual and both sides of the head are
affected.
cluster headaches - A type of severe headache that occurs in clusters
(bunches) on a daily or near daily basis. These are much more common in men
than in women (10 to 1).
rheumatoid arthritis - An autoimmune disorder with severe pain characterized
by loss of cartilage, bone, and tendons, within or around joints.
osteoarthritis - Is the most common form of arthritis. It involves progressive
inflammation of the joints, made worse by movement. It is mostly confined to
older people.
phantom limb pain - The experience of chronic pain in an absent body part. To
the brain, the body part is still there.
back braces? - For support have become common for those whose jobs require
a lot of lifting and moving. According to our text, these devices have NO effect in
preventing injuries.