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Pharmacophysiology > Sensory System Principles > Flashcards

Sensory System Principles Flashcards

1
Q

What is the sensory system?

A

Represents the afferent arm of the somatic nervous system and provides the brain with information about the internal and external environment.

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2
Q

How does the sensory system work?

A

A sensory receptor receives and converts a stimulus energy into action potentials. Afferent (peripheral) neurons conduct those action potentials to the integration center. The integration center experiences conscious sensation and perception and elicits a response.

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3
Q

What are the 3 essential parts of the sensory system?

A

1) Sensory receptors
2) Neural pathways
3) Brain

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4
Q

What do sensory receptors do?

A

They receive stimuli from the external or internal environment.

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5
Q

What do neural pathways do?

A

Conduct info from receptors to the brain or spinal cord.

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6
Q

What does the brain do with info from neural pathways?

A

Processes info derivative of sensory stimiuli.

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7
Q

Define a sensory receptor.

A

Receptors that detect/identify info about ext and int environment.

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8
Q

Name 5 examples of sensory receptors and explain what they do.

A

1) Photoreceptors - detect light
2) Mechanoreceptors - transmit mechanical deformation (muscles and joints, etc)
3) Thermoreceptors - detect temperature
4) Chemoreceptors - detect chemicals (smell, taste)
5) Nociceptors - detect pain

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9
Q

What are the two main types of sensory receptors?

A

1) Specialized nerve endings on primary afferent neurons

2) Specialized receptor cells associated with primary afferent neurons

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10
Q

What is the primary function of a sensory receptor?

A

Sensory receptors are transducers.

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11
Q

Define a transducer.

A

A device that transforms energy from one type to another.

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12
Q

What are the electrical signals produced by sensory receptors called?

A

Receptor potentials

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13
Q

What do the receptor potentials trigger upon reaching threshold level? (Hint: conducted to CNS)

A

Action potentials (APs)

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14
Q

How is receptor potential generated?

A

Ion flux across the receptor membrane leads to change in membrane potential.

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15
Q

Where does the action potential first arise?

A

First node of Ranvier.

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16
Q

What is the relationship between stimulus and AP frequency?

A

More stimulus = more frequency.

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17
Q

Name the 6 main characteristics of receptor potential.

A

1) Graded response to a stimulus that either is depolarizing or hyperpolarizing
2) Has threshold in stimulus amplitude that must be reached to trigger AP
3) Involves opening/closing of specific ion channels in receptor membrane
4) Can work to trigger AP within same cell or adjacent cell
5) The magnitude of the receptor potential decreases with distance from origin
6) Magnitude of receptor potential determines frequency of the AP (not amplitude)

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18
Q

How can you tell the magnitude of the receptor potential?

A

With larger depolarization, increased AP firing frequency occurs so primary afferent neuron firing frequency reflects the magnitude of the receptor potential which reflects magnitude of stimulus.

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19
Q

Define receptor adaptation.

A

Decrease in receptor sensitivity leading to a decrease in AP frequency in afferent neuron despite stimulus.

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20
Q

What are the two types of receptor adaptation?

A

1) Rapidly Adapting (phasic receptors)

2) Slowly Adapting (tonic receptors)

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21
Q

How does rapid receptor adaptation work?

A

Generates RP and AP at onset of stimulus and quickly stops responding.

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22
Q

What is an example of rapid receptor adaptation?

A

Receptors of skin pressure when sitting.

23
Q

How does slow receptor adaptation work?

A

Maintains a persistent or slowly decaying RP during constant stimulus while initiating an AP for the duration of stimulus.

24
Q

What is an example of slow receptor adaptation?

A

Constantly monitoring joints and muscles for posture.

25
Q

What is coding?

A

Coding is the conversion of stimulus energy into a signal that relays the relevant sensory info to CNS.

26
Q

Where does coding begin?

A

Receptive neurons.

27
Q

What 3 things is coding influenced by?

A

1) modality (type)
2) intensity (strength)
3) location

28
Q

What is a sensory unit?

A

A single afferent neuron with all receptor endings.

29
Q

Define receptive field.

A

An area that leads to activity in a particular afferent neuron when stimulated. Usually overlap with neighboring neurons.

30
Q

What is the specific form of energy of a stimulus called?

A

Modality.

31
Q

What is adequate stimulus?

A

The modality to which the receptor responds to best.

32
Q

How might one stimulus give rise to multiple sensations? (i.e. cube of ice on skin, cold AND touch)

A

When receptive fields for different modalities overlap.

33
Q

How is the intensity of a stimulus determined to be weak or strong if both transmitted as APs?

A

Frequency of APs generated in the first order neuron.

34
Q

What is AP frequency determined by?

A

The size of the receptor potential that is generated.

35
Q

Define recruitment of sensory units.

A

Stronger stimuli excite more receptors and afferents.

36
Q

What is touch, temperature, and pain that can all be localized to a site on the body?

A

Stimulus locations.

37
Q

What does the labeled line code do?

A

Connects the peripheral receptor to the CNS via a series of distinct neurons.

38
Q

What is the acuity of locating a stimulus dependent upon?

A

The amount of convergence or neuronal input in specific ascending neural pathways.

39
Q

How does convergence affect acuity of locating a stimulus?

A

Greater the convergence, the less acuity is displayed.

40
Q

What are the 3 factors that affect acuity?

A

1) Size of receptive field covered by single sensory unit
2) Density of sensory units
3) Amount of overlap in nearby receptive fields

41
Q

Why is a robust response to a stimulus produced by an afferent neuron if stimulus is applied at center of receptive field?

A

High density of receptors in center of receptive field.

42
Q

Why will a single stimulus trigger more than one sensory unit?

A

Because receptor endings of different afferent neurons overlap.

43
Q

Why is it difficult to detect a precise location of stimulus in a single afferent neuron?

A

Receptive field overlap.

44
Q

What is lateral inhibition?

A

Enhances contrast between center and periphery of stimulated region, increasing brain’s ability to localize sensory input.

45
Q

How does lateral inhibition work?

A

Inhibitory neurons diminish APs from being passed concertedly so neighboring neurons and their respective second order neurons.

46
Q

What are afferent sensory pathways comprised of?

A

Bundles of 3 or more neurons.

47
Q

Once sensory pathways enter the CNS, what do they synapse with first?

A

2nd order interneurons.

48
Q

If a single type of sensory information is carried, which kind of ascending pathway will it travel?

A

Specific ascending pathway.

49
Q

If multiple types of sensory information is carried, what ascending pathway type will it take?

A

Non-specific ascending pathway.

50
Q

Where do specific ascending pathways eventually end up in the CNS?

A

Opposite side of CNS in specific regions called receiving centers.

51
Q

What are 3 examples of receiving centers?

A

1) Eyes -> Visual cortex
2) Taste buds -> Gustatory cortex
3) Ears -> Auditory cortex

52
Q

What does the association cortex do and where is it located?

A

It elaborates information (complex analysis) and it is located outside the primary cortical sensory or motor areas.

53
Q

Define a sensation.

A

A consciously perceived stimulus.

54
Q

Define a perception.

A

Awareness of a stimulus combined with understanding of the meaning.

Pharmacophysiology (6 decks)

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