2-08 The Mechancical Sense

Front 1

Objective

Identify three kinds of touch receptors.

Back 1

1. Receptors with simple bare neuron endings tend to act as pain receptors.
2. Receptors with elaborated neuron endings include: Meissner’s corpuscles, which respond to light touch, and Ruffini endings, which respond to heat.
3. There are receptors that have bare endings surrounded by non-neuronal cells, which modify the receptors’ function. Example: Pacinian corpuscles, which detect joint movements

Front 2

Objective

Discuss the significance of a dermatome map.

Back 2

Each spinal nerve innervates a limited area of the body. The skin area connected to a single sensory spinal nerve is called a dermatome.

For example, the third thoracic nerve (T3) innervates a strip of skin just above the nipples as well as the underarm area.

But the borders between dermatomes are not as distinct as a typical dermatome map would imply; there is actually quite a bit of overlap between adjacent pairs.

Front 3

Objective

Explain how opiate receptors regulate pain.

Back 3

Opiates exert their effects by binding to certain receptors found mostly in the spinal cord and the periaqueductal gray area of the midbrain.

Researchers have also found that opiate receptors act by blocking the release of substance P (a neuropeptide involved in transmission of pain impulses).

Front 4

Objective

State the basic premise of gate theory.

Back 4

According to the gate theory, spinal cord neurons that receive messages from pain receptors also receive input from touch receptors and from axons descending from the brain. These other inputs can close the “gates” for the pain messages—at least partly by releasing endorphins (which act as natural pain killers).

Basically, non-pain stimuli can modify the intensity of pain. You have no doubt noticed this principle yourself. When you have an injury, you can decrease the pain by gently rubbing the skin around it or by concentrating on something else.

Front 5

Objective

Explain how capsaicin can be used for relieving pain.

Back 5

Capsaicin is a chemical substance found in hot peppers that stimulates pain receptors. Capsaicin produces a burning or painful sensation caused by releasing substance P. However, it releases substance P faster than neurons can re-synthesize it, leaving the cells less able to send pain messages. Also, high disease of capsaicin damage pain receptors. Capsaicin rubbed onto a sore shoulder, an arthritic joint, or other painful areas produces a temporary burning sensation followed by a longer period of decreased pain.

Front 6

Objective

Identify a method of preventing chronic pain.

Back 6

To prevent chronic pain, it is important to limit pain from the start. If you were about to undergo major surgery, you would start taking morphine before the surgery. Allowing pain messages to bombard the brain during and after the surgery increases the sensitivity of the pain nerves and their receptors. People who begin taking morphine before surgery need less of it afterward.

Front 7

semicircular canals

Back 7

Interconnected tubes inside the ear

Oriented in three different planes, filled with a jellylike substance, and lined with hair cells

An acceleration of the head at any angle causes the jellylike substances in one of theses canals to push against the hair cells

Action potentials travel through part of the eighth cranial nerve to the brainstem and cerebellum

Front 8

somatosensory system

Back 8

The sensation of the body and its movements

Front 9

pacinian corpuscle

Back 9

Somatosensory receptor that detects sudden displacements or high-frequency vibrations

Front 10

spinal nerve

Back 10

Bundle of spinal axons coming from the spinal cord that transmits sensory and motor information

Front 11

dermatome

Back 11

Skin area connected to a single sensory spinal nerve

Front 12

capsaicin

Back 12

Chemical substance found in hot peppers that stimulate pain receptors

Front 13

Substance P

Back 13

Neuropeptide involved in the transmission of pain impulses

Front 14

opioid mechanisms

Back 14

Systems that respond to opiate drugs and similar chemicals

Front 15

endorphins

Back 15

Transmitters that attach to the same receptors as morphine

Produce pain-relieving effects

Front 16

gate theory

Back 16

Spinal cord neurons that receive messages from pain receptors also receive input from touch receptors and from axons descending from the brain

These other inputs can close the “gates” for the pain messages—at least partly by releasing endorphins (which act as natural pain killers)

Front 17

placebo

Back 17

Drug or other procedure with no pharmacological effects