Lecture 17: Senses

Question 1

What are 3 Levels of Processing of Sensory Information?

Answer 1

1. Receptor level
2. Circuit level
3. Perceptual level

Question 2

1.

Generating Signal at Receptor Level

Answer 2

stimulus energy must match receptor specificity (touch receptors do not respond to light)
graded potentials must reach threshold in first-order sensory neuron

Question 3

1

Adaptation at Receptor Level

Answer 3

Adaptation is the change in sensitivity in the presence of a constant stimulus.

The receptor membranes become less responsive and the receptor potentials decline in frequency or stop.

Question 4

1

Peripheral Adaptation at Receptor Level

Answer 4

Level of the receptor and reduces how much information is sent to the CNS

Central adaptation is at the level of the neural pathway to the brain and involves brain nuclei

Question 5

1

Phasic Receptors

Answer 5

Phasic receptors send signals when there is a phase change, so the start of something or end of something.

Question 6

1

Tonic Receptors

Answer 6

Adapt slowly or not at all.

Question 7

1

Phasic Receptor Example

Answer 7

Receptors for touch; you notice when you change your clothes or take them off but you don’t really think about them while you have them on.

Question 8

1

Tonic Receptor Example

Answer 8

Nociceptors and most proprioceptors.

Question 9

2.

Processing at the Circuit Level (Function)

Answer 9

to get information to the correct area of the cortex so that one is aware(perception) and can localize source of stimulus

Question 10

2.

Serial Processing

Answer 10

1st order neuron —> 2nd order neuron —-> 3rd order neuron
ex. skin receptor (for pain) —-> dorsal horn of spinal cord
—-> thalamus —-> cortex

Question 11

2 Curcuit Level Processing

1.

Answer 11

Ascending pathways carry impulses to appropriate regions of cerebral cortex

Question 12

2 Curcuit Level Processing

2.

Answer 12

First order brings signal to spinal cord

Question 13

2 Curcuit Level Processing

3.

Answer 13

Synapse with second order neurons in cord or medulla UNLESS reflex- then doesn’t go to brain, just synapses directly with motor neuron

Question 14

2 Curcuit Level Processing

4.

Answer 14

Second order carries impulse to thalamus or cerebellum

Question 15

2 Curcuit Level Processing

5.

Answer 15

Synapses with third order in thalamus

Question 16

2 Curcuit Level Processing

6.

Answer 16

Transmits signals to somatosensory cortex or cerebrum

Question 17

2 Curcuit Level Processing

7.

Answer 17

goes to perceptual level

Question 18

Three main pathways for somatosensory information to ascend the spinal cord

Answer 18

1.Dorsal column-medial lemniscal pathways
2.Spinothalamic pathways
3.Spinocerebellar pathways

Question 19

1 Dorsal column-medial lemniscal pathways

Answer 19

target is the thalamus; usually a single type of receptor (or a few related types) that can be localized precisely on the body surface (discriminative touch, vibrations; also proprioceptors);decussation at the level of the medulla

Question 20

2 Spinothalamic pathways

Answer 20

• target is also the thalamus; input from several types of receptors with information pertaining to pain, temperature, coarse touch and pressure; don’t localize source as precisely; decussation at level of spinal cord

Question 21

3 Pinocerebellar pathways

Answer 21

• target is the cerebellum; information about muscle or tendon stretch so cerebellum can coordinate skeletal muscle activity; ipsilateral, so do not decussate; we are not consciously aware

Question 22

Processing at the Perceptual Level

Answer 22

• Information has to get to the right place to be understood and localized; using the correct neural pathway to permit arrival at the correct destination is key
• Notion of sensation (aware of changes in internal/external environment) versus perception (conscious interpretation of those changes); perception determines how you will respond

Question 23

Properties of Sensory Perception

Answer 23

1. Perceptual detection
2. Magnitude estimation
3. Spatial discrimination
4. Feature abstraction
5. Quality discrimination
6. Pattern recognition

Question 24

1 Perceptual detection

Answer 24

Simply put, one is aware; need to sum inputs from several receptors to achieve detection

Question 25

2 Magnitude estimaton

Answer 25

Intensity of the stimulus; encoded by action potential frequency

Question 26

3 Spatial discrimination

Answer 26

Localize the stimulus; notion of “two-point discrimination test” as a measure of how precise that localization can be; can vary between 5 and 50 mm, depending on body area

Question 27

4 Feature abstraction

Answer 27

Each neuron tuned to one feature or property of a stimulus - often several features come together for the sensory experience (temperature, texture, firmness, & dimensions of something you are touching)

Question 28

5 Quality discrimination

Answer 28

Distinguish submodalities of a particular sensation (e.g. submodalities of taste)

Question 29

6 Pattern recognition

Answer 29

E.g. recognition of a familiar face, a letter, a piece of music

Question 30

Pain

Answer 30

• Can be helpful - warns of tissue damage and motivates us to take action
• Pain is very personal – can’t really be measured
• Extreme temperature or pressure
• Pain chemicals include histamine, K+, ATP, acids, bradykinin

Question 31

Pain suppression

Answer 31

Endogenous opioids are endorphins and enkephalins; their release can be triggered by the activation of the SNS.

Question 32

Pain Tolerence

Answer 32

Pain threshold (amount of stimulus needed to generate sensation of pain) is the same for everyone, but tolerance (ability to withstand high levels of pain) varies and can be influenced by genetics as well as mental state, even gender, social isolation, stress.

Question 33

Somatic Pain

Answer 33

Musculoskeletal pain; often described as aching, gnawing, throbbing or cramping; usually easy to localize because the bones and muscles are well innervated

Question 34

Visceral pain

Answer 34

Pain associated with organs of the thorax and abdominal cavity – aching, burning, gnawing – can be the result of extreme stretching of tissues, ischemia, irritating chemicals, muscle spasms – uses same pathways as somatic pain making it possible to have referred pain

Question 35

Referred Pain

Answer 35

Pain arising from one part of the body appears to come from somewhere else; (e.g. heart attack and pain along medial aspect of left arm – both are spinal nerves T1 to T5)

Question 36

Phantom Pain

Answer 36

A type of hyperalgesia (pain amplification) which involves NMDA receptors making it a “learned” pain – if limb amputated under general anesthesia, then spinal cord still experienced the pain of amputation; better to use epidural anaesthetics to block spinal cord during the surgery