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SF2- Exam 2 > Mechanisms of Sensory Systems and Somatosensory Receptor Physiology > Flashcards

Mechanisms of Sensory Systems and Somatosensory Receptor Physiology Flashcards

1
Q

____________refers to the detection of the elements and energies in our internal and external environment.

A

Sensation

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2
Q

Sensation requires the conversion of ___________ into signals that can be recognized by our __________.

A

Environmental signals; CNS

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3
Q

______________ is the interpretation of the significance, meaning or quality of sensory information.

A

Perception

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4
Q

What factors play a role in perception?

A

Learning

Memory

Context

Physiological state

*Perception can vary widely between individuals

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5
Q

What is sensory physiology?

A

The study of the mechanisms guiding the transduction of a stimulus into action potentials that travel to the brain resulting in sensation (conscious or unconscious).

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6
Q

What are the three types of sensory systems? What does each system produce and convey?

A

Somatosensory Systems

  • Convey: impulses from skin, skeletal muscles, and joints
  • Produce: sensations of temperature, touch, pressure, itch, pain, and muscle tension

Visceral Sensory Systems

  • Convey: impulses from visceral organs
  • Produce: sensations of stretch, pressure, pain

Special Sensory Systems

  • convey: impulses from special sense organs (ears, eyes, nose, tongue)
  • Produce: sensations of light, sound, taste, smell, head motion & equilibrium/balance
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7
Q

Which type of sensory system is involved in subconscious detection?

A

Visceral sensory systems process subconscious detection of osmolarity, pH, O2, and CO2.

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8
Q

Distinguish between general and special senses

A

žGeneral senses are detected by sensory receptors that are scattered throughout the body.

žSpecial senses are detected by receptors localized to special sensory organs (located in the head)

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9
Q

What are the general senses?

A

Temperature

Touch

Pressure

Pain

Proprioception

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10
Q

What are the special senses?

A

Sight

Sound

Taste

Smell

Balance

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11
Q

What are the steps of the afferent pathway?

A

Sensory receptors-> Primary afferent neuron-> Secondary sensory neuron-> Thalamus-> Brain

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12
Q

What are the steps of the efferent pathway?

A

Brain-> Effector

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13
Q

Of the basic types of neurons, which type is not found in humans?

A

Unipolar

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14
Q

What are the functions of transducers?

A
  • Specialized to detect environmental energy (stimuli)
  • Convert stimulus energy into changes in transmembrane electical potential of the sensory (afferent) neuron
  • Trigger action potentials (in the primary afferent neuron) that are transmitted to secondary and tertiary afferent neurons and travel to the brain
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15
Q

Where do transducers initially trigger action potentials?

A

In the primary afferent neuron

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16
Q

Type of receptor that responds to stimuli arising from outside the body. Where is this receptor type found and what does it produce?

A

Exteroceptors

Location: in skin and special sensory organs

Produce : sensations of light, sound, smell, taste, touch, temperature

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17
Q

Type of receptor that responds to stimuli arising in internal viscera and blood vessels. What is this receptor type sensitive to and what does it produce?

A

Interoceptors

›Sensitive to chemicals, pH, tissue stretch, and temperature

›Produce sensations of distension or pain; many do not lead to sensations

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18
Q

Interoceptors are also known as________________

A

Visceroceptors

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19
Q

Type of receptor that responds to stimuli arising in skeletal muscles, tendons, joints, ligaments, and connective tissue. What is this receptor type sensitive to and what does it produce?

A

Proprioceptors

›Sensitive to contraction, stretch, movement

›Produces sensations of body movements and special position

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20
Q

What are the 5 main types of receptors? What type of stimulus does each type respond to?

A

žMechanoreceptors

  • Respond to mechanical forces
    • Touch, pressure, vibration, stretch, tension

žThermoreceptors

  • Respond to temperature changes
    • Heat, cold

žPhotoreceptors

  • Respond to wavelength of light

žChemoreceptors

  • Respond to chemicals
    • Osmolality, pH, CO2, O2, organic molecules, airborne molecules

žNociceptors (polymodal)

  • Respond to potentially damaging stimuli
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21
Q

General senses

Location of cell body

Neuronal structure

A

Location of cell body: Dorsal root ganglia or cranial nerve ganglia

Neuronal structure: Pseudounipolar

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22
Q

Special senses

Location of cell body

Neuronal structure

A

Location of cell body: In special sense organs

Neuronal structure: Bipolar

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23
Q

What are the different structures of sensory receptors? What are characteristics of each?

A

Simple

  • Naked nerve endings
  • Encapsulated naked nerve endings

Complex

  • Specialized receptor cells
    • produce neurotransmitters
  • Primary afferent neuron is a separate​ cell from the receptor cell
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24
Q

What are the steps of stimulus transduction in simple receptors?

A
  1. Stimulus is detected by receptor
  • Alters membrane permeability to ions
  • Activate second messender systems which then lead to altered membrane permeability to ions
  1. Change in graded potential
  2. Graded potential triggers action potentials in afferent neurons
  3. Action potentials are propagated
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25
Q

For sensation, generator potential must reach threshold at ___________.

A

Trigger zone

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26
Q

What are the steps of stimulus transduction in special sensory cells (complex)?

A
  1. Stimululus detected by receptor cell
  2. Change in graded potential in receptor cell
  3. Receptor cell releases neurotransmitter
  4. Neurotransmitters genreate graded potentials in primary sensory neuron
  5. Graded potential triggers APs in primary afferent neuron
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27
Q

What are the receptors from the organs listed below?

Eyes

Tongue

Nose

Otolith organ

Organ of corti

A
  • Eyes (retina): rods and cones
  • Tongue: Taste buds
  • Nose: Olfactory cells
  • Otolith organs: hair cells
  • Organ of corti: hair cells
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28
Q

Accessory organs direct and transfer input _________.

A

Energy

29
Q

What is the role of the pinna?

A

The pinna, also known as the outer ear, amplifies and directs sound waves into the auditory canal

30
Q

What is the role of the tempanic membrane?

A

The tempanic membrane, also known as the eardrum, amplifies sound waves

31
Q

What is the role of the cornea and lens of eye?

A

Focus entry of light onto the retina of the eye

32
Q

What is the role of the hair cells on body?

A

Transmits light touch and movement

33
Q

Sensory systems mediate what four attributes of a stimulus

A
  • Modality
    • Form of energy to which the receptor responds
  • Intesity
    • # of receptors activated
    • Frequency of APs
  • Duration
    • Duration of action potentials
    • APs at onset and again at the cessation of a stimulus
  • Location
34
Q

What are the different modalities to which a receptor can respond?

A
  • Mechanical (touch, pressure, vibration, stretch, acceleration)
  • Thermodynamic (heat, cold)
  • Electromagnetic (light)
  • Chemical (oxygen, pH, odorants, glucose and other organic molecules)
  • Damaging Intensities (tissue damage or potentially damaging levels of other stimulus modalities)
35
Q

____________ is the specific sub-modality (specific range of modality) to which a receptor is most sensitive.

A

žAdequate stimulus

36
Q

Very low levels of the adequate stimulus affects the __________ potential.

A

Receptor

37
Q

What is the labeled line principle?

A

Excitation of sensory receptor and sensory neuron elicits only one sub-modality of sensation

  • This localizes the stimulus and identifies the type of stimulus

Premises:

  • Individual receptors preferentially transduce information about an adequate stimulus
  • Individual primary afferent fibers carry information from a single type of receptor

NOTE: Stimulation anywhere along the sensory pathways from a sensory receptor to the specialized sensory cortex will only result in one particular sensation

38
Q
A
39
Q

Which areas of the brain process skeletal muscle movement?

A

Primary motor cortex

Motor association area (premotor cortex)

40
Q

Which areas of the brain process sensory information from skin, musculoskeletal system, viscera, and taste buds?

A

Primary somatic sensory cortex

Parietal lobe

Sensory association area

41
Q

Which areas of the brain process sensory information from vision?

A

Visual association area

Occipital lobe

Visual cortex

42
Q

Which areas of the brain process sensory information from hearing?

A

Auditory association area

Auditory cortex

Temporal lobe

43
Q

Which areas of the brain process sensory information from taste?

A

Temporal lobe

Gustatory cortex

44
Q

Which areas of the brain process sensory information from smell?

A

Temporal lobe

Olfactory cortex

45
Q

Which areas of the brain coordinates information from other association areas, and controls some behaviors?

A

Frontal lobe

Prefrontal association area

46
Q

What determines the frequency of APs?

A
  • Directly related to the receptor potential
  • Modified by inhibitory or stimulatory inputs
  • Modified by adaptation
47
Q

Sensation of the duration of an AP is modified by it’s ability to ____________.

A

Adapt

48
Q

_______________ is the decreased sensitivity to a sustained stimulus.

A

Adaptation

  • žReceptor membranes become less responsive
  • Receptor potential decreases
  • Action potentials decline in frequency
  • Dictated by the receptor structure
49
Q

What ion channel activity causes a receptor potential to decrease?

A
  • Inactivation of Na+ or Ca2+ channels
  • Activation of K+ channels

ž

ž

50
Q

_______________ adapt slowly or not at all.

A

Tonic receptors

  • Usually coupled to small diameter, unmyelinated fibers
51
Q

Which type of receptors are tonic receptors?

A

Nociceptors

Proprioceptors

Thermoreceptors

Crude Touch

52
Q

___________ are fast adapting and signal at the beginning and end of stimulus.

A

Phasic receptors

  • Usually coupled to large, myelinated fibers
53
Q

Which type of stimuli activate phasic receptors?

A

Pressure

Fine Touch

Smell

54
Q

Absolute threshold

A
  • Minimum stimulation needed to detect a particular stimulus
  • Usually defined as the stimulus needed for detection 50% of the time
55
Q

Difference Threshold

A
  • Minimum difference between two stimuli that a subject can detect 50% of the time
  • Just noticeable difference (JND)
  • Increases with magnitude
56
Q

What is the relationship between stimulus intensity and receptor potential at stimulus intensities less than 1.5?

A

Exponential

57
Q

What is the relationship between stimulus intensity and receptor potential at stimulus intensities between 1.5 to 3?

A

Linear

58
Q

What is the relationship between stimulus intensity and receptor potential at stimulus intensities between 3 and 4.5?

A

Logarithmic

59
Q

What is the relationship between stimulus intensity and receptor potential at stimulus intensities greater than 4.5?

A

Horizontal

60
Q

Weber’s Law

A

States that the amount of change in stimulus intensity that is needed for the change to be detectable is proportional to the initial intesity of the stimulus

ΔI/I= K

*NOTE: The constant K varies according to stimulus modality

61
Q

What are examples of skin mechanoreceptors? What does each receptor detect?

A

Hair follicle receptor

  • Light touch
  • Moving touch

Pacinian corpuscles

  • Deep pressure
  • Vibration

Meissner’s corpuscles

  • Fine touch

Merkel receptors

  • Pressure & texture

Ruffini endings

  • Skin stretch
  • Deep pressure
62
Q

Hair Follicle Receptor

Location

Accessory organ

Receptor

Receptive Field

Adaptation

Fiber type

A

Location: Deep dermis

Accessory organ: Hair follicle

Receptor: Free nerve endings tightly coiled around hair follicle

Receptive Field: Small

Adaption: Rapid

Fiber Type: žAβ & Aδ

63
Q

What is the transduction mechanism for hair follicle receptors?

A
  1. Hair is deflected
  2. Motion of hair follicle against nerve endings triggers opening of mechanosensitive ion channels
  3. Ion channels are opened
  4. Ion channels are quickly blocked by collagen fibers
64
Q

Pacinian Corpuscle

Location

Accessory organ

Receptor

Receptive Field

Adaptation

Fiber type

A

Location:

  • Deep dermis hairy and glabrous (hairless) skin
  • Joint capsules (proprioceptor)

Accessory organ

  • Concentric lamellae of flattened cells
  • Supported by collageneous tissue
  • Spaces between lamellae are filled with fluid

Receptor:

  • Bare nerve terminals
  • Occupies center of corpuscle

Receptive Field: Large

Adaptation : Rapid

Fiber type: žAβ

65
Q

What is the transduction mechanism for Pacinian Corpuscle?

A
  1. Applied pressure is transmitted to the nerve terminal derfoming it
  2. Mechanically gated Na+ channels are opened, depolarizing the membrane
  3. AP are generated along the fiber
  4. Fluid between lamellae is quickly dispersed, relieving the pressure on the terminal
  5. Membrane potential returns to resting level
  6. Removal of the probe again deforms nerve terminal resulting in depolarization
66
Q

Meissner’s Corpuscle

Location

Accessory organ

Receptor

Receptive Field

Adaptation

Fiber type

A

Location:

  • Beneath the epidermis
  • Fingers, palm of the hand, plantar surface of the foot (glabrous skin)

Accessory organ

  • ​Stacks of horizontally flattened epithelial cells enclosed in a connective tissue sheath

Receptor:

  • Bare nerve terminals arborizes among the epithelial cells

Receptive Field: Small

Adaptation: Rapid

Fiber type: žAβ

67
Q

Merkel’s Cells

Location

Receptor

Transduction

Receptive Field

Adaptation

A

Location:

  • Below the epidermis
  • Lips, Finger tips (glabrous skin)

Receptor:

  • Large epithelial cell in close contact with a sensory neuron terminal

Transduction: Merkel’s cell releases neurotransmitter

Receptive Field: Small

Adaptation: Slowly adapting

Fiber type

68
Q

Rufini’s ending

Location

Accessory organ

Receptor

Receptive Field

Adaptation

Fiber type

A

Location:

  • Deep dermis layer of both hairy and glabrous skin

Receptor:

  • Endings of sensory neuron encapsulated within bundles of collagen fibrils that are connected with similar fibrils of the dermis

Receptive Field: Large

Adaptation: Slow

Fiber type: žAβ

SF2- Exam 2 (16 decks)

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