Chapter 7 Sensory Physiology

Question 1

specialized cells that generate graded potentials called receptor potentials in response to a stimulus

Can be a specialized endings of the primary afferent neurons or

Separate receptor cells that signal the primary afferent neurons using neurotransmitters

Answer 1

Sensory Receptors

Question 2

five major divisions of these sensory receptors based on stimuli that they respond to:

Answer 2

1. Mechanoreceptors
2. Thermoreceptors
3. Photoreceptors
4. Chemoreceptors
5. Nociceptors

Question 3

the process of converting sensory information into electrochemical signals that are sent to the brain.

Answer 3

Primary Sensory Coding

Question 4

is the conversion of a stimulus into a signal that is conveyed to the central nervous system.

Answer 4

Coding

Question 5

is conveyed by both the frequency and the amplitude of the resulting signals.

Answer 5

Information

Question 6

A decrease in receptor sensitivity, results in a decrease in action potential frequency in an afferent neuron despite a stimulus of constant strength

Answer 6

Adaptation

Question 7

• Increased by increasing frequency of action potentials in a single afferent neuron
• As the strength of a local stimulus increases, receptors on adjacent branches of an afferent neuron are activated

Answer 7

Stimulus Intensity

Question 8

• Coded by the site of a stimulated receptor
• Action potentials from each receptor travel along unique pathways to a specific region of the CNS

Answer 8

Stimulus Location

Question 9

one stimulus location can be discerned from an adjacent one depends upon the amount of convergence of neuronal input in the specific ascending pathway

Answer 9

Acuity

Question 10

how does Overlapping Receptive Fields happen

Answer 10

• When receptor endings of different afferent neurons overlap, a stimulus will trigger activity in more than one sensory unit
  A high action potential frequency in one neuron but low in the others provide more accurate localization of the stimulus

Question 11

• enables the localization of a stimulus site
• information from afferent neurons whose receptors are at the edge of a stimulus is strongly inhibited
• enhances the contrast between stimulated region

Answer 11

Lateral Inhibition

Question 12

• Exact localization with __________ is possible because it removes the information from the peripheral regions

Answer 12

Lateral Inhibition

Question 13

____________ are subject to extensive modification before they reach higher levels of the CNS.

Answer 13

Sensory signals

Question 14

Modification can come from

Answer 14

• inhibition from collaterals from other ascending neurons (lateral inhibition)
• pathways descending from the brain
• by synapses on the axon terminals of the afferent neurons (example of presynaptic inhibition)
• indirectly via interneurons that affect other neurons in the sensory pathways.

Question 15

a chain of three or more neurons that form an ascending pathway to the CNS

Answer 15

Neural Pathways in Sensory Systems

Question 16

what are the chain of three or more neurons that form an ascending pathway to the CNS

Answer 16

• First order neuron
• Second order neuron
• Third order neuron

Question 17

what happens when afferent neurons enter the CNS and synapse with the interneurons

Answer 17

• The process may diverge to terminate on several interneurons
  or
• Many afferent neurons terminate upon a single interneuron

Question 18

Processing of afferent information happens in:

Answer 18

• primary cortical receiving areas
• association areas in the cerebral cortex where complex integration occurs

Question 19

• relies upon various association areas of the cortex to properly process sensory information

Answer 19

Primary somatosensory cortex

Question 20

perceptual processing involves arousal, attention, learning, memory, language, and emotions

Answer 20

true

Question 21

Perception of sensory information is dependent upon numerous factors

Answer 21

true

Question 22

• Sensation from the skin, muscles, bones, tendons and joints, or somatic sensation
• initiated by a variety of sensory receptors

Answer 22

Somatic Sensation

Question 22

Factors that Affect Perception

Answer 22

1. Receptor adaptation and afferent processing
2. Emotions and experiences
3. Not all stimuli give rise to a conscious sensation
   - Ex: stretch receptors monitor blood pressure
4. Lack of receptors for certain stimuli
   - Ex: radio waves
5. Damaged neural pathways
6. Drugs

Question 23

general principles of sensory
stimulus organization

Answer 23

1. Specific sensory receptor types are sensitive to certain modalities and submodalities.
2. A specific sensory pathway codes for a particular modality or submodality.
3. The specific ascending pathways are crossed so that sensory information is generally processed by the side of the brain opposite the stimulated side of the body.
4. In addition to other synaptic relay points, most specific ascending pathways synapse in the thalamus on their way to the cortex.
5. Information is organized such that initial cortical processing of the various modalities occurs in different parts of the brain.
6. Specific ascending pathways are subject to descending controls.

Question 23

Somatic Sensation receptors respond to:

Answer 23

- Touch and pressure - Sense of posture and movement - Temperature - Pain

Question 24

slowly adapting mechanoreceptor, touch and pressure

Answer 24

Merkle's corpuscle

Question 24

-rapidly adapting mechanoreceptor, touch and pressure

Answer 24

Meissner's corpuscle

Question 25

slowly adapting, some are nociceptors, some are thermoreceptors, and some are mechanoreceptors

Answer 25

Free nerve ending

Question 25

slowly adapting mechanoreceptor, skin stretch

Answer 25

Ruffini corpuscle

Question 25

apidly adapting mechanoreceptor, vibration and deep pressure

Answer 25

Pacinian corpuscles-

Question 26

Differs from the other somatosensory modalities * After transduction of the first noxious stimuli into action potentials, changes occur in the pain pathway that alter response to subsequent stimuli. * can be altered by past experiences, suggestion, emotions, and the simultaneous activation of other sensory modalities

Answer 26

Pain

Question 27

an increased sensitivity to painful stimuli

Answer 27

Hyperalgesia

Question 28

is the selective suppression of pain without effects on consciousness or other sensations.

Answer 28

Analgesia

Question 29

Some mechanisms to achieve pain relief:

Answer 29

Electrical stimulation of the CNS - Drugs: NSAIDs and Morphine (opioids) - neurons in the inhibitory pathways that release morphine-like endogenous opioids - Acupuncture - Transcutaneous Electrical Stimulation (TEMS) - Massage

Question 30

The brain is "confused" and you feel pain from an internal organ as another area of the body.

Answer 30

Referred Pain

Question 31

Distinguish between a sensation and a perception

Answer 31

A sensation is the raw, immediate sensory input received by the body from the environment through the senses, like feeling the warmth of a cup or seeing a bright light, while a perception is the brain's interpretation and organization of that sensory information, which gives meaning to the sensation, like recognizing the warmth as a hot cup of coffee or identifying the bright light as a car headlight.

Question 32

How does the nervous system distinguish between stimuli of different types?

Answer 32

The nervous system distinguishes between different types of stimuli by using specialized sensory receptors that are designed to detect specific stimuli, sending signals along dedicated neural pathways to specific regions of the brain, essentially acting like "labeled lines" where the identity of the stimulus is preserved throughout the transmission process; this means different types of stimuli activate different sets of neurons, allowing the brain to interpret the information accordingly.