General Principles of Sensory Processing, Touch, and Pain

Question 1

Sensory receptor organs

Answer 1

Organs specialized to detect a certain stimulus

Receptor cells within the organ convert the stimulus into an electrical signal

Question 2

Adequate stimulus

Answer 2

The type of stimulus to which a sensory organ is particularly adapted

Ex: photic light energy for the eye

Question 3

Transduction

Answer 3

Converting information to neural signals

Question 4

The doctrine of specific nerve energies says:

Answer 4

receptors and neural channels for different senses are independent

Question 5

Labeled lines

Answer 5

The concept of labeled lines says that the brain recognizes distinct senses because action potential travels along separate nerve tracts

Lines are: sound, smell, and touch

Question 6

Receptors in skin

Answer 6

Touch receptor associated w hair follicles

Question 7

Pacinian corpuscle

Answer 7

A skin receptor that detects vibration and pressure

Question 8

A stimulus to the corpuscle…

Answer 8

opens stretch-sensitive sodium channels made of a protein called Piezo, and produces a graded receptor potential (or generator potential)

Question 9

When the potential is big enough, the receptor reaches _______ and generates an action potential

Answer 9

threshold

Question 10

You can only detect the touch if…

Answer 10

an action potential is generated

Question 11

Structure and function of the Pacinian Corpuscle

Answer 11

• Cell membrane stretches, channel opens, sodium comes in
• Stimulus is touch to corpuscle
• Causes structural change in ion channel to allow sodium to come in
• Influx of sodium ions causes a change in the membrane of the cell
• If enough come in, cell fires an AP and that’s how we detect the touch that comes in

Question 12

Stimulus location is determined from…

Answer 12

the position of the activated receptors

Question 13

The action potentials produced by a sensory neuron always have the same size and duration, so one way the intensity of sensory events are encoded is…

Answer 13

in number and frequency of action potentials

Question 14

Some sensory systems employ multiple sensory receptor cells that specialize in one part of a…

Answer 14

range of intensities

Question 15

as strength of a stimulus increases…

Answer 15

more neurons sensitive to higher intensities are recruited

Question 16

Range fractionation

Answer 16

Each of the traces represents a nerve cell with a different threshold (a different response to different stimuli)

Question 17

Adaptation

Answer 17

Phasic receptors and tonic receptors

Question 18

Phasic receptors

Answer 18

Display adaptation and decrease the frequency of action potentials

Question 19

Tonic receptors

Answer 19

Show slow or no decline in action potential frequency

Question 20

Why does adaptation do this?

Answer 20

Sensory systems emphasize change in stimuli, as that is more important for survival
This prevents the nervous system from being overwhelmed by too much info coming in

Question 21

Other ways to control sensory info

Answer 21

Accessory structures: such as eyelids

Top-down processing: higher brain centers suppress some sensory inputs and amplify others

Question 22

Sensory info path in the brain

Answer 22

Sensory information enters the CNS through the spinal cord or brain stem and then reaches the thalamus

Question 23

The ________ transmits info to the cerebral cortex

Answer 23

thalamus

Question 24

Then, the cortex directs the thalamus to…

Answer 24

suppress some sensations

Question 25

Primary sensory cortex

Answer 25

Swaps information with the secondary sensory cortex

Question 26

Delivers touch info to the brain

Answer 26

The dorsal column system

Question 27

Dorsal column system

Answer 27

The stimulus triggers the receptive field of a neuron These receptors send projections via the dorsal column of the spinal cord where they synapse on dorsal column nuclei in the medulla (brain stem) Axons from neurons in the medulla cross the midline and go to the thalamus for initial processing, and then on to the primary somatosensory cortex So, the brain processes touch information from the contralateral side of the body

Question 28

Receptive field

Answer 28

The receptive field is the region in which a stimulus will alter a sensory neuron’s firing rate Receptive fields differ in size, shape, and response to types of stimulation

Question 29

What does the larger size of a region indicate?

Answer 29

The amount of neurons is different

Question 30

The more neurons in the cortex dedicated to an area...

Answer 30

the smaller the receptive field and the better that body part is detecting touch

Question 31

If we touch within a receptive field (two pokes close to each other)...

Answer 31

neuron is only triggered one time; one action potential

Question 32

The somatosensory cortex is plastic

Answer 32

Intentional stimulation of a specific body region can be changed by experience Loss of use will cause it to shrink

Question 33

Phantom limb

Answer 33

When D3 and D2 expand, the cells themselves don’t move, but their projections do Phantom limb touch happens because of neurons taking over area Ex: face neurons take over hand area, so when you touch the face some of the neurons still think you’re responding to hand

Question 34

Pain

Answer 34

An unpleasant experience associated with tissue damage Pain helps us to withdraw from its source, engage in recuperative actions, and to signal others

Question 35

Human pain can be measured

Answer 35

The McGill Pain Questionnaire describes three aspects of pain: 1. Sensory-discriminative quality (e.g., throbbing, gnawing, shooting) 2. Motivational-affective (emotional) quality (e.g., tiring, sickening, fearful) 3. Cognitive evaluative quality (e.g., no pain, mild, excruciating)

Question 36

Why is pain so hard to measure?

Answer 36

Everyone’s pain tolerance is different Level of experience with pain Expecting the pain or not

Question 37

Nociceptors

Answer 37

Peripheral receptors that respond to painful stimuli

Question 38

Free nerve endings

Answer 38

in the dermis; have specialized receptor proteins on the cell membrane that respond to various signals The free nerve endings produce different receptor proteins, so they respond to different stimuli like temperature changes, chemicals, and pain

Question 39

Peripheral mediation of pain

Answer 39

Usually stems from damaged tissue

Question 40

The anterolateral (or spinothalamic) system

Answer 40

Transmits the sensations of pain and temperature

Question 41

Receptors synapse on spinal neurons in the ___________

Answer 41

dorsal horn

Question 42

Pain information __________________ in the spinal cord before ascending to the brain

Answer 42

crosses the midline

Question 43

Phantom limb (neuropathic) pain

Answer 43

Microglial cells release chemicals that make the dorsal horn neurons hyperexcitable and cause chronic pain Visual system can change the brain’s processing of info

Question 44

Social rejection activates brain regions for affective pain

Answer 44

Activation of anterior cingulate cortex People who took Tylenol experienced less distress and showed less activation in these brain regions

Question 45

Analgesia

Answer 45

The absence or reduction in pain sensation

Question 46

Opioids

Answer 46

are endogenous opiate-like peptides in the brain

Question 47

Opiates

Answer 47

Drugs that reduce pain

Question 48

Three classes of endogenous opioids

Answer 48

Endorphins Enkephalins Dynorphins

Question 49

Opioid receptors

Answer 49

respond to opiates or opioids

Question 50

Stimulation of mu opioid receptors

Answer 50

relieves pain more effectively in men than women

Question 51

Stimulation of k opioid receptors

Answer 51

relieves pain more effectively in women

Question 52

Periaqueductal gray (PAG)

Answer 52

An area in the midbrain involved in pain perception Electrical stimulation of the PAG produces potent analgesia