PSY 250 Lecture Notes - Lecture 45: Autoimmune Disease, Gene Therapy, Premotor Cortex
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Chapter 11: The Body Senses and Movement Book Notes
A. Introduction Information
a. Christina was a healthy, active woman of 27
b. She began dropping things, trouble standing and sitting upright
c. Son she was bedridden, lying motionless, speaking between shallow breaths in a faint
and expressionless voice, and an expressionless face
d. Spinal tap determined she was suffering from neuritis
e. Neuritis: inflammation of the nerves that is often caused by a viral infection
f. She lost all proprioception (the sense that collects information from our muscles and
tendons and joints to tell us where our hands are and what movements our feet and legs
are making)
g. Didn’t last long, but permanently affected her, and she was in rehabilitation for a year and
was eventually able to get back to a somewhat normal life
B. The Body Senses
a. We get information about our body from the somatosensory system and from the
vestibular system
b. Somatosenses include proprioception; the skin senses, which tell us about what
conditions at the surface of our body; and the interoceptive system, concerned with
sensations in our internal organs
c. Vestibular system informs the brain about body position and movement
d. Interoceptive system operates mostly in the background and participates less directly in
behavior
e. Proprioception
i. Proprioception: Latin proprius “belonging to one’s self;” the sense that informs us
about the position and movement of our limbs and body
ii. Sensors report tension and length in muscles and the angle of the limbs at the
joints
iii. Not as glamorous a sense as vision or audition, or even touch
iv. Does more than provide information; it is critically important in the control of
movement
f. The Skin Senses
i. Skin Senses: touch, warmth, cold, and pain
ii. Studies have found new evidence that itch, until now believed to be a variant of
pain, has its own receptors and neural pathway
iii. Each sense is distinct from the others, with its own receptors and separate
“labeled line” pathway to the brain
iv. Two general types of receptors
1. Free Nerve Endings: processes at the ends of neurons; detect warmth,
cold, and pain
2. Encapsulated Receptors: more complex; their role is to detect touch
v. Touch is a complex sense that conveys several types of information
vi. Meissner’s Corpuscles (receptors on the surface of the skin)
1. Detect the texture and fine detail of objects
2. Detect movement and come into play when you explore an object with
gentle strokes of your hand or when a blind person reads Braille
vii. Pacinian Corpuscles and Ruffini Endings (receptors in deeper layers of the skin)
1. Detect stretching of the skin and contribute to our perception of the
shape of grasped objects
viii. Fingertips and lips are most sensitive and upper arms and calves of the legs are
least sensitive
ix. Other three skin senses are detected by free nerve endings
x. Transient Receptor Potential (TRP)
g. The Vestibular Sense
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i. Vestibular Sense: helps us maintain balance, and it provides information about
head position and movement
ii. Organs Involved
1. Semicircular Canals
a. Especially responsive to movement of the head and body
b. At the base of each canal is a jelly like mass called a cupula,
which has a tuft of hair cells protruding into it
c. During acceleration, the fluid shifts in the canals and displaces
cupula; bending the hair cells in one direction depolarizes them,
and bending them in the other direction hyperpolarizes them,
increasing or decreasing the firing rate in neurons
d. Deceleration has a similar effect
2. Utricle and Saccule
a. Monitor head position in relation to gravity
b. When the head tilts, gravity shifts the gelatinous mass and the
hair cells are depolarized or hyperpolarized, depending on the
direction of tilt
c. Hair cell receptors in the utricle are arranged in a horizontal
patch
d. Saccule’s receptors are on its vertical wall (the two organs can
detect tilt in any direction)
iii. Vestibular system sends projection to the cerebellum and the brain stem; there is
also a pathway to the cortex (parieto-insular-vestibular cortex)
h. The Somatosensory Cortex and the Posterior Parietal Cortex
i. The body is divided into segments called dermatomes, each served by a spinal
nerve
ii. Each dermatome overlaps the next by ⅓ to ½; this way, if one nerve is injured,
the area will not lose all sensation
iii. Body sense information enters the spinal cord (via spinal nerves) or the brain (via
cranial nerves) and travels to the thalamus
iv. The body sense neurons go to the projection area, the somatosensory cortex,
located in the parietal lobes just behind the primary motor cortex and the central
sulcus
v. Most of the neurons cross from one side of the body to the other side of the brain
vi. Somatotopic Map: of the body, with adjacent body parts represented in adjacent
parts of the cortex
vii. Some of the cortical cells have complex receptive fields on the skin
1. Some have excitatory centers and inhibitory surrounds like the visual
system
2. Some of them are large, while smaller excitatory-inhibitory fields sharpen
the localization of excitation and help distinguish two points touching the
skin
viii. Primary Somatosensory Cortex: consists of four areas, each of which contains a
map of the body and plays a role in processing sensory information from the
body
1. Thalamus sends its output to two of these subareas, which extract some
information and pass the result on to the other two areas, which in turn
send their output to the secondary somatosensory cortex
ix. Secondary Somatosensory Cortex: receives input from the left and the right
primary somatosensory cortices, so it combines information from both sides of
the body
x. Neurons in this area are responsive to stimuli that have acquired meaning
xi. Posterior Parietal Cortex: an association area that brings together the body
senses, vision, and audition
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xii. Body Integrity Identity Disorder (Apotemnophilia): people with no apparent brain
damage - or mental or emotional disorder, for that matter - are so convinced that
a limb doesn’t belong to them that they actually ask to have it amputated
1. Limb is touched, there is no response in superior parietal area
2. Skin conductance response to stimulation is doubled in that limb when
indicates a high level of emotional feeling about the limb
xiii. Out-of-Body Experience: the individual hallucinates seeing his or her body from
another location, for example, from a position above the detached body
1. Causes include traumatic damage and epilepsy affecting the junction
between the parietal and temporal lobes
2. Experience can also be produced by electrical stimulation in that area
i. Pain and its Disorders
i. Detecting Pain
1. Pain begins when certain free nerve endings are stimulated by intense
pressure or temperature, by damage to tissue, or by various chemicals
2. Tissue injury causes injured cells to release a wide array of signaling
molecules, referred to as the “inflammatory soup”
a. Histamine, bradykinin, prostaglandins, and cytokines
3. Substance P: a neuropeptide that increases pain sensitivity
4. Pain information passes through the thalamus to the somatosensory
cortex
5. The anterior cingulate cortex and the insula carry out additional
processing of the emotional implications of pain, and the prefrontal
cortex is concerned with pain of longer duration
ii. Treating Pain
1. Local anesthetics - those that are applied to or injected into the painful
area - block sodium channels in the pain neurons and reduce their ability
to fire
2. General anesthetics (injected or inhaled) make the patient unconscious
a. Work in the CNS
b. Affect the functioning of several proteins
c. Aspirin and ibuprofen
i. Block enzymes required for producing prostaglandins, so
they reduce inflammation as well as pain
d. Acetaminophen
i. Blocks the same enzymes but weakly and with no anti-
inflammatory benefit, so its major effect is probably the
CNS
3. Ameliorating pain takes stronger drugs (morphine)
4. Tanezumab (an antibody for nerve growth factor) has shown safety and
effectiveness in clinical trials with chronic back pain and the inflammatory
pain of arthritis
5. An experimental drug that blocks the TRPV1 receptor produces modest
reduction of bone cancer pain in mice, but much smaller doses
significantly increase the effectiveness of morphine when the two are
used in combination
6. Gene therapy shows success in cancer patients whose pain wasn’t
relieve by 200 mg of morphine a day
7. Chronic pain patients given continuous fMRI feedback of activity in their
cingulate gyrus learned to reduce pain-related brain activity and their
experience of pain
iii. Internal Mechanisms of Pain Relief
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Document Summary
Chapter 11: the body senses and movement book notes. Interoceptive system operates mostly in the background and participates less directly in behavior: proprioception. Proprioception: latin proprius belonging to one"s self; the sense that informs us about the position and movement of our limbs and body. Sensors report tension and length in muscles and the angle of the limbs at the joints. Not as glamorous a sense as vision or audition, or even touch. Does more than provide information; it is critically important in the control of movement: the skin senses. Studies have found new evidence that itch, until now believed to be a variant of pain, has its own receptors and neural pathway. Each sense is distinct from the others, with its own receptors and separate. Two general types of receptors: free nerve endings: processes at the ends of neurons; detect warmth, cold, and pain, encapsulated receptors: more complex; their role is to detect touch.
