Chaptere 5 Flashcards
(24 cards)
What sensory modalities do somatosensory receptors detect?
Touch, temperature, body position (proprioception), and pain.
Which parts of the body have the highest sensitivity to touch?
The tips of the fingers and the lips.
Name the four types of touch receptors embedded in the skin.
Pacinian corpuscles, Meissner’s corpuscles, Merkel’s disks, and Ruffini endings.
What type of stimulus do Pacinian corpuscles best detect?
Rapidly changing indentations, such as vibration and flutter.
Which receptor responds well to sustained pressure on the skin?
Merkel’s disks.
What is a receptive field in somatosensation?
The area of skin over which an individual receptor responds to stimuli.
Which receptor has a larger receptive field: Pacinian corpuscles or Meissner’s corpuscles?
Pacinian corpuscles.
How do sensory nerves from touch receptors reach the brain?
Through large myelinated fibers entering the dorsal roots of the spinal cord, relaying through the medulla and thalamus to the somatosensory cortex.
Which side of the brain processes sensory input from the right side of the body?
The left hemisphere.
What is the “sensory homunculus”?
A distorted representation of the body surface mapped onto the somatosensory cortex, showing receptor density and cortical space allocation.
What test measures spatial touch discrimination on the skin?
The two-point discrimination test.
How does active exploration affect the sense of touch?
Active movement (e.g., running a fingertip over a surface) produces finer discrimination than passive contact.
How are the sensory and motor systems connected in touch?
Sensory inputs from touch receptors influence motor neurons controlling muscles, aiding grip and manipulation.
What distinguishes pain from other somatosensory sensations?
Pain is unpleasant, emotionally impactful, varies greatly between individuals, and provides little information about stimulus type.
What types of nerve fibers carry pain signals?
Fast myelinated Aδ fibers and slow unmyelinated C fibers.
Name two brain areas involved in the emotional aspect of pain.
Anterior cingulate cortex and insular cortex.
What is the difference between pain intensity and pain unpleasantness in the brain?
Pain intensity activates the somatosensory cortex; pain unpleasantness activates the anterior cingulate cortex.
Why is pain important for survival?
It warns of damage, triggers protective reflexes, and helps learn to avoid harmful situations.
What endogenous substances help suppress pain naturally?
Endogenous opioids such as met-enkephalin and endorphins.
How does the descending pain modulation pathway work?
It descends from brain areas like the periaqueductal gray to the spinal cord, raising pain thresholds.
What is hyperalgesia?
An increased sensitivity to pain, with a lowered pain threshold and sometimes pain without a stimulus.
What mechanisms contribute to hyperalgesia?
Sensitization of peripheral receptors, enhanced excitation, and reduced inhibition in pain pathways.
How does acupuncture relieve pain according to research?
By electrical stimulation triggering release of endogenous opioids like endorphins and dynorphins.
What are “meridians” in Traditional Chinese Medicine?
Specific pathways on the body along which acupuncture needles are inserted for pain relief.
