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(MUL) Medical Physiology > Chp 48/49 Somatic Sensations > Flashcards

Chp 48/49 Somatic Sensations Flashcards

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USMLE® Step 1 flashcards
1
Q

What is the basic function of the nervous system by which one monitors the external and internal environment.

A

Sensory Function

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2
Q

Sensory function one of the basic functions of the CNS monitors the internal and external environment….this monitoring requires structures known as what?

A

Receptors

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3
Q

Define Receptors

A

Act as transducers that convert various environmental stimuli into graded signals known as Receptor Potentials

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4
Q

Once various environmental sitmuly is converted into graded signals known as “Receptor Potentials”,

What are Receptor Potentials repsonsible for?

A

Receptor Potentials then initiate Action potentials (nerve impulses) which are carried by sensory nerver fibers into the Spinal Cord and in some cases up to the Brain.

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5
Q

Define Integration at the system level

A

Integration at the system level refers to the way the nevous system inteprets sensory information and determines the appropriate responses to a sensory stimulus.

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6
Q

Provide an example of an Input which is integrated at the “lower brain level”

A

Sensory Input: from blood pressure receptors called “Baroreceptors” which are intergrated in the brainstem (Vasomotor center) to bring about minute to monute requlation of blood pressure.

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7
Q

When sensory areas of the Cortex are excited, the sensory input registers as consciousness or awareness….this conscious awareness of a sensory imput is termed a ______.

A

Sensory input called Sensation ( being able to see it, feel it)

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8
Q

Various sensations that can be distinquished can be termed_____?

A

Sensory Modalities (the senses)

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9
Q

Sensory Modalities (the senses) are commonly grouped in 2 main Categories…name each.

A
  1. Special Senses
  2. Somatic Senses
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10
Q

Special Senses include?

A
  1. Vision
  2. Hearing
  3. Taste
  4. Smell
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11
Q

Somatic Senses include?

A
  1. Thouch
  2. pressure
  3. Position sense
  4. pain
  5. thermal sensations of hot and cold
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12
Q

Name the 4 classifications of Somatic Sensation

A
  1. Exteroreceptive sensations
  2. Proprioceptive sensations
  3. Visceral sensations
  4. Deep sensations
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13
Q

Define Exteroreceptive sensations

A

Exteroreceptive sensations are those from the surface of the body.

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14
Q

Define Proprioceptive sensations

A

Proprioceptive sensations are those having to do with the physical state of the body - including:

a. position sensations,
b. tendon and muscle sensations,
c. pressure sensations from the bottom of the feet,
d. sensation of equilibrium (which is often considered a “special” sensation rather than a somatic sensation)

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15
Q

Define Visceral sensations

A

Visceral sensations are those from the viscera of the body; refers specifically to sensations from the internal organs

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16
Q

Define Deep sensations

A
  • Deep sensations* are those that come from deep tissues, such as:
    a. fasciae,
    b. muscles,
    c. bone.

These include mainly “deep” pressure, pain, and vibration.

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17
Q

Each type of receptor is highly sensitive to what ?

Provide 1 example…

A

Each type of receptor is highly sensitive to one type of stimulus for which it is designed and is almost nonresponsive to other types of sensory stimuli

Ex: Rods and Cones of the eyes are highly sensitive to Light but almost completely nonrespoinsive to normal range of heat/cold/pressure on the eyeballsor chemical change in the blood.

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18
Q

Define Modality of Sensations

A

Each of the principal types of sensation that we can experience:

a. pain
b. touch
c. sight
d. sound

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19
Q

Explain what takes place as Modality of Sensatins: Pain, Touch, sight and sound are stimulated

A
  1. each nerve tract terminates at a specific point in the central nervous system,
  2. the type of sensation felt when a nerve fiber is stimulated is determined by the point in the nervous system to which the fiber leads.
    * This specificity of nerve fibers for transmitting only one modality of sensation is called the labeled line principle.*
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20
Q

What are the 5 Classifications of Sensory Receptors?

A

● Mechanoreceptors

● Thermoreceptors

● Nociceptors

● Electromagnetic receptors

● Chemoreceptors

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21
Q

Define Mechanoreceptors

A

mechanoreceptors

which detect mechanical compression or stretching of the receptor or of tissues adjacent to the receptor;

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22
Q

Define Thermoreceptors

A

thermoreceptors

detect changes in temperature, some receptors detecting cold and others warmth

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23
Q

Define Nociceptors

A

nociceptors (pain receptors),
which detect damage occurring in the tissues, whether physical damage or

chemical damage;

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24
Q

Define Electromagnetic receptors

A

Electromagnetic receptors

which detect light on the retina of the eye

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25
Q

Define Chemoreceptors:

A

Chemoreceptors:

detect:

a. taste in the mouth,
* b. smell in the nose,
c. oxygen level in the arterial blood*,
d. osmolality of the body fluids, carbon dioxide concentration,

perhaps other factors that make up the chemistry of the body

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26
Q

Provide examples of Mechanoreceptors found in Epidermis and Dermis

(skin tactile sensibilities)

A

Epidermis and Dermis Mechanoreceptors:

  1. Free nerve endings
  2. Expanded tip endings:
    a. Merkel’s discs
  3. Spray endings
  4. Ruffini’s endings
  5. Encapsulated endings:
    a. Meissner’s corpuscles
    b. Krause’s corpuscles
  6. Hair end-organs
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27
Q

Provide examples of Mechanoreceptors found in

(deep tissue sensibilities)

A

Deep tissue sensibilities

  1. Free nerve endings
  2. Expanded tip endings
  3. Spray endings: Ruffini’s endings
  4. Encapsulated endings:
    - Paninial corpuscles
    - Muscle spindles
    - Golgi tendon receptors
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28
Q

Mechanoreceptor for Hearing is found where?

A

Sound receptors of cochlea

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29
Q

Mechanoreceptor for Arterial pressure is found where?

A

Baroreceptors of carotid sinuses and aorta

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30
Q

Mechanoreceptors used for Equilibrium are?

A

Vestibular receptors

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31
Q

What are Nociceptors and what are they used for?

A

Are Free Nerve Endings

Used for: sensing Pain

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32
Q

What are Electromagnetic receptors responsible for and name the 2 Receptors

A

Responsible for Vision

Rods and Cones

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33
Q

Provide an Example of Chemoreceptor and its function

(Total of 6)

A
  1. Taste Receptors of taste buds
  2. Smell Receptors of olfactory epithelium
  3. Arterial oxygen Receptors of aortic and carotid bodies
  4. Osmolality Neurons in or near supraoptic nuclei 5. Blood CO2 Receptors in or on surface of medulla and in aortic and carotid bodies
  5. Blood glucose, amino acids, fatty acids Receptors in hypothalamus
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34
Q

In order to cause Receptor Potentials-

Name 4 ways in which a Receptor can be excited.

A
  1. Mechanical Deformation of the receptor, which stretches the receptor membrane and opens ion channels
  2. application of a chemical to the membrane, which alos opens ion channels
  3. change of the temperature of teh membrane, which alters the permaeability of the membrane
  4. the effects of elecromagnetic radiation such as light on retianl visual receptor
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35
Q

Describe the mechanism of Receptor Potentials

A

the basic cause of teh change in memebrane potential is a change in membrane permeability of the receptor, which allows Ions toe diffuse more or less readily throughj teh membrane and thereby leading to change teh Transmemerane Potential

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36
Q

T or F

The Receptor Potential allows to produce Action Potential in Nervous Fibers; the condition is that the receptor potential need to ne strong enough.

A

True

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37
Q

T or F

The more the Receptor potential rises above the threshold level, the greater the Action Potential Frequency

A

TRUE

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38
Q

When the receptor potential rises above the ____ for eliciting _____ ______ in the Nerve Fiber attached to the receptor, then _____ _____ occurs.

A

Threshold

Action Potential

Action Potentials

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39
Q

Define Pacinian Corpuscle

A

is an onion-shaped structure of nonneural (connective) tissue built up around the nerve ending that reduces the mechanical sensitivity of the nerve terminal itself.

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40
Q

_______ adapt either partially or completely to any constant stimulus after a period of time

A

receptor

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41
Q

What is t he longest measured time for complete adaptation of a mechanoreceptor?

Which is the adaptation time for what kind of Baroreceptors?

A
  1. about 2 days
  2. for many carotid and aortic baroreceptors.
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42
Q

Provide 2 examples of nonmechanoreceptors.

and …….Do they adapt completely?

A
  1. the chemoreceptors
  2. pain receptors

Note: probably never adapt completely.

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43
Q

What do Slowly Adapting Receptors detect ?

Provide an example

A

Slowly Adapting Receptors Detect Continuous Stimulus Strength –

Ex: The “Tonic” Receptors

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44
Q

Define tonic receptor

A

Slowly adapting receptors continue to transmit impulses to the brain as long as the stimulus is present (or at least for many minutes or hours)
Therefore, they keep the brain constantly apprised of the status of the body and its relation to its surroundings.

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45
Q

Slowly adapting receptors continue to transmit impulses to the brain, keeping the brain constantly apprised of the status of the body and its relation to its surroundings……Provide an example of a slow adapting receptor

A

impulses from the muscle spindles and Golgi tendon apparatuses allow the nervous system to know the status of muscle contraction and load on the muscle tendon at each instant.

46
Q

Provide example of some other slowly adapting receptors:

Because the slowly adapting receptors can continue to transmit information for many hours, they are known as?

A

Other slowly adapting receptors include
(1) receptors of the macula in the vestibular apparatus

(2) pain receptors,
(3) baroreceptors of the arterial tree,
(4) chemoreceptors of the carotid and aortic bodies.

Known as: Tonic receptors

47
Q

Rapidly Adapting Receptors detect change in what?

Can receptors that adapt rapidly be used to transmit continuous signal?

A

Detect Change in Stimulus

Receptors that adapt rapidly cannot be used to transmit a continuous signal because these receptors are stimulated only when the stimulus strength changes.

Note: they react strongly while a change is actually takning place!!

48
Q

Rapidly adapting recetors react strongly while a change is actually taking place, therefore these receptors are known as?

A
  1. Rate receptors
  2. movement receptors
  3. Phasic receptors
49
Q

Provide an example of Rapidly adapting receptor…

A

Pacinian Corpuscle

50
Q

Pacinian Corpuscle is considered to be what type of Receptor and why?

What makes Pacinian Corpuscle exceedingly important?

A
  1. Rapidly Adapting Receptor:

In the case of the Pacinian Corpuscle, sudden
pressure applied to the tissue excites this receptor for a few milliseconds, and then its excitation is over even though the pressure continues. But later, it transmits a signal again when the pressure is released.

  1. Pacinian corpuscle is exceedingly important in apprising the nervous system of rapid tissue deformations, but it is useless for transmitting information about constant conditions in the body.
51
Q

The somatic senses can be classified into 3 physiologic types:

A

(1) the mechanoreceptive somatic senses:
a. tactile
b. position sensations that are stimulated by mechanical displacement of some tissue of the body.
(2) the thermoreceptive senses which detect heat and cold
(3) the pain sense,which is activated by any factor that damages the tissues.

52
Q

Meissner’s Corpuscle adaption to nerve impulses is considered…rapid or slow?

A

Rapidly Adapring

53
Q

Merkel’s Cell adaptation is rapid or slow?

A

Slowly Adapting

54
Q

Nerver Fibers that transmit different types of signals come in all sizes:

What is the size of the Diameter?

What is the range of conduction velocities?

A
  1. between .5 and 20 micrometers in Diameter
  2. Range of conducting velocities is between .5 and 120 m/sec
55
Q

T or F

The larger the diameter of Nerve Fiber the weaker the conducting velocity.

A

FALSE

The larger the diameter of Nerve Fiber the GREATER the conducting velocity.

56
Q

Spatial Summation is defined as ?

provide an example….

A

The process whereby increasing signal strength is transmitted by using progressively greater numbers of fibers

ex. Receptor Field of the fiber = entire cluster of fibers from one pain fiber frequently covers an area of skin as large as 5 centimeters in diameter.

57
Q

T or F

Transmitting signals of Increasing Strength is by Increasing the Frequency of Nerve impulses in each fiber.

A

TRUE

58
Q

the tactile senses include:

They are all detected by the same type of receptor, however poses 3 principal differences among them…Name these differences

A
  1. touch generally results from stimulation of tactile receptors in the skin or in tissues immediately beneath the skin
  2. pressure generally results from deformation of deeper tissues
  3. vibration results from rapidly repetitive sensory signals, but some

of the same types of receptors as those for touch and pressure are used.

  1. tickle senses
59
Q

The Position Senses include:

A
  1. Static Position
  2. Rate of movement senses
60
Q

Name the 6 different types of Tactile receptors.

A

1• Merkel’s discs

2• Meissner’s corpuscle
3• Free nerve endings

  1. Hair end-organ
    5• Ruffini’s end-organs

6• Pacinian corpuscles

61
Q

Name the contents of “Hairy Skin” located in the Epidermis/Dermis/Hypodermis

A

Epidermis: Merkel’s Cell (SA1 sensor)

Dermis: Hair Follicle

Hypodermis: Pacinian Corpuscle

62
Q

Name the contents of “Hairless Skin” located in the Epidermis/Dermis/Hypodermis

A
  1. Epidermis:

Meissner’s Corpuscle

Merkel’s Cell (SA1 sensor)

  1. Dermis:

Ruffini’s Corpuslce (SA2 sensor)

Nerve Fibers

  1. Hypodermis:

Pacinian Corpuscle

63
Q

Define Meissner’s Corpuscle

A

Elongated, encapsulated, mechanoreceptor, nerve ending of a Large (type AB) myelinated sensory nerve fiber, located superficially within the dermal papillae

64
Q

Where are Meissner’s Corpuscles found ?

A

Found in nonhairy parts of the skin and are particularly abundant in the fingertips, and other areas of the skin where one’s ability to discern spatial locations of touch sensations is highly developed

They adapt in a fraction of a second after they are stimulated, they are particularly sensitive to movement of objects over the surface of the skin as well as to low- frequency vibration.

65
Q

Define Merkel’s discs

A
  1. Merkel’s discs –tonic receptors are expanded tip tactile receptors Non-hair skin

EX: Fingertips and other areas that contain large numbers of Meissner’s corpuscles

Merkel’s discs differ from Meissner’s corpuscles in that they transmit an initially strong but partially adapting signal and then a continuing weaker signal that adapts only slowly.

66
Q

What are Merkel’s discs responsible for?

A

Responsible for giving steady state signals that allow one to determine continuous touch of objects against the skin

67
Q

Describe Hair end-organ phasic receptor

A

Each hair and its basal nerve fiber called:

Hair end-organ are a touch receptor.

This receptor adapts readily

and, like Meissner’s

corpuscles, detects mainly

movement of objects on the surface of the body or

initial contact with the body.

68
Q

Define Ruffini’s End-organ and identify type of Receptor..

A

Tonic Receptor

Located in the deeper layers of the skin and also in still deeper internal tissues

-multibranched, encapsulated endings

  • Adapt very slowly
  • are important for signaling continuous states of deformation of the tissues: EX- Heavy prolonged touch and pressure signals.

-found in joint capsules and help to signal the degree of joint rotation.

69
Q

Describe Pacinian corpuscles and identify type of receptor.

A

Phasic Receptor

  • lie both immediately beneath the skin and deep in the fascial tissues of the body
  • Stimulated only by rapid local compression of the tissues because “They adapt in a few hundreadths of a second”
  • important for detecting

tissue vibration other rapid changes in the mechanical state of

the tissues.

70
Q

Name 2 Rapidly adapting mechanoreceptors

A
  1. Pacinian Corpuscle
  2. Meissner’s Corpuscle
71
Q

Name 2 slowly adapting Mechanoreceptors

A
  1. Ruffini’s corpuscle
  2. Merkel Cell
72
Q

Whick Tactile Receptors are involved in detection of Vibration ?

A

All Tactile Receptors are involved in detection of vibration

73
Q

Pacinian corpuscles can detect signal vibraitions from _____ to_____ cycles per second.

A

-Can detect signal vibrations from 30 to 800 cycles per second because they respond extremely rapidly per minute

  • -* rapid deformations of the tissues,
  • also transmit their signals over type (Aβ Nerve Fibers) which can transmit as many as 1000 impulses per second.
74
Q

Low-Frequency vibrations ranges from ____ to _____ cycles per second, in contrast stimulate other tactile receptors, especially “______ _____”. which are less rapidly adapting than Pacinian corpuscles.

A

Vibrations from 2 up to 80 cycles per second

Meissner’s Corpuscle

75
Q

Which of the Receptors is the only one to elicit the tickle and itch sensations?

A

Very sensitive, rapidly adapting Mechanoreceptive free nerve endings elicit the tickle and itch sensations.

76
Q

Where are the “Mechanoreceptive free Nerve endings” found?

A

Almost exclusively in the superficial layers of the skin, which is also the only tissue from which the tickle and itch sensations usually can be elicited.

77
Q

What is the “tickle and itch sensations” transmited by?

A

These sensations are transmitted by very small type C unmyelinated fibers similar to those that transmit the aching, slow type of pain.

78
Q

What is the purpose for itch senstation?

A

to call attention to mild surface stimuli such as a flea crawling on the skin or a fly.

79
Q

Name the two alternative sensory pathways for transmitting Somatic Signals into the CNS…

A
  1. the dorsal column:
    - medial lemniscal system
  2. the anterolateral system

These two systems come back together partially at the level of the thalamus.

80
Q

what is the Dorsal column: medial lemniscal system responsible for?

A
  • It carries signals upward to the medulla of the brain mainly in the dorsal columns of the cord.
  • after the signal synapse and cross to the opposite side of the medulla, they continue upward through the brain stem to the thalamus by way of Medial Leminiscus.
81
Q

Explain signals in the Anterolateral system, immediately after entering the spinal cord…….

A
  • signals in the anterolateral system, immediately after entering the spinal cord from the dorsal spinal nerve roots, synapse in the dorsal horns of the spinal gray matter, then cross to the opposite side of the cord and ascend through the anterior and lateral white columns of the cord.

They terminate at all levels of the lower brain stem and in the thalamus.

82
Q

What is the Dorsal Column-Medial Lemniscal system composed of?

A

-composed of large, myelinated nerve fibers that transmit signals to the brain at velocities of

30 to 110 m/sec,

83
Q

What is the Anterolateral system composed of?

A

the anterolateral system is composed of smaller myelinated fibers that transmit signals at velocities ranging from a few meters per second up to 40 m/sec.

84
Q

Which Sensory Pathway system has higher degree of spatial orientation of the nerve fibers with respect to their origin?

A

The Dorsal Column-Medial lemniscal system has a higher degree of spatial oreientation of the nerve fibers with respect to their origin

85
Q

T or F

The Anterolateral System has much higher spatial orientation

A

False:

Dorsal Column-Medial lemniscal system has the higher degree of spatial orientation of the nerve fibers with respect to their origin

86
Q

In the Thalamus:

the Medial Lemniscal Fibers terminate in the Thalamic sensory relay area known as what?

A

Ventrobasal Complex

Form the Ventrobasal complex, 3rd Order nerve fibers project mainly to the Postcentral Gyrus of the cerebral cortex which is called

Somatic Sensory Are 1.

87
Q

Somatosensory Are 1 is responsible for what parts of body systems?

(3,1,2)

A
  1. Thighs
  2. Thorax
  3. Neck
  4. Shoulder
  5. Hand
  6. Fingers
  7. Tongue
  8. Abdomen
88
Q

Somatosensory Area II is responsible for which system parts?

(5a, 7a)

A
  1. Leg
  2. Arm
  3. Face
89
Q

The anterolateral system has a special capability that the dorsal system does not have…

Explain it…

A

-the ability to transmit a broad spectrum of sensory modalities pain, warmth, cold, and crude tactile sensations;

90
Q

What is the Dorsal System limited to?

A

The dorsal system is limited to
discrete types of mechanoreceptive sensations.

91
Q

In the Dorsal Column-Medial Lemniscal System:

What do Touch Sensations require?

A
    1. Touch sensations* requiring a high degree of localization of the stimulus
      1. Touch sensations requiring transmission of fine gradations of intensity
92
Q

What occurs in the Dorsal Column-Medial Lemniscal System?

5 major points…

A
  1. Touch sensations requiring a high degree of localization of the stimulus
  2. Touch sensations requiring transmission of fine gradations of intensity
  3. Phasic sensations, such as vibratory sensations
  4. Sensations that signal movement against the skin Position sensations from the joints
  5. Pressure sensations having to do with fine degrees of judgment of pressure intensity
93
Q

What is Anterolateral System responsible for ?

A
    1. Pain
    1. Thermal Sensations: including both Warmth and Cold Sensations
    1. Tickle and itch sensations
    1. Sexual sensations
    1. Crude touch and pressure sensations capable only of crude localizing ability on the surface of the body
94
Q

Somatosensory Cortex isit is divided into about 50 distinct areas called ______based on histological structural differences.

Where do all modalities of sensation terminate?

A

Brodmann’s areas

Note: this map is important because virtually all neurophysiologists and neurologists use it to refer by number sensory signals from all modalities of sensation terminate in the cerebral cortex immediately posterior to the central fissure.

95
Q

Brodmann’s Area Diagram Review

A
96
Q

Define Cortical Homunculus

A

Physical representation of the human body, located within the Brain.

A “neurological Map” of the anatomical divisions of the body.

97
Q

There are 2 Types of “Cortical Homunculus”

Name the 2 types

A
  1. Sensory
  2. Motor
98
Q

What happens when “Widespread Bilater excision of Somatosensory Area 1” occurs?

Name all that apply..(5 statements)

A

Causes “Somatosensory Area 1” loss of sensory judgement.

  1. unable to judge critical degrees of pressure against the body
  2. unable to judge the weights of objects.
  3. unable to judge shapes or forms of objects.

This is called astereognosis

  1. unable to localize discretely the different sensations in the different parts of the body
  2. unable to judge texture of materials because this type of judgment depends on highly critical sensations caused by movement of the fingers over the surface to be judged.
99
Q

Define Two-Point Discrimination

This method is utilized to test what type of discrimination?

A
  • A method used to test tactile discrimination is to determine a person’s so-called “two-point” discriminatory ability.

In this test, two needles are pressed lightly against the skin at the same time, and the person determines whether two points of stimulus are felt or one point.

100
Q

Vibratory signals are rapidly repetitive and can be detected as vibration up to ____ cycles per second.

A

700 cycles per second.

101
Q

The higher-frequency vibratory signals originate from the ____ _____ in the Skin and deep tissue

These signals are transmitted only in the _____ _____ _____.

A

Pacinian Corpuscles

dorsal column pathway.

102
Q

Lower-frequency signals (below about _____ ____ ______) can originate from _______corpuscles

A

lower-frequency signals (below about 200 per second) can originate from Meissner’s corpuscles as well.

103
Q

define Stereognosis

Impaired stereognosis is an early sign of damage to what?

A

The ability to identify objects by handling them without looking at them.

Impaired stereognosis is an early sign of damage to the cerebral cortex and sometimes occurs in the absence of any detectable defects in touch and pressure sensation when there is a lesion in parietal lobe posterior to the postcentral gyrus

104
Q

Neurologists use the “Application of Vibration” to test what?

A

The application of Vibration “tuning fork”

to diffent periperal parts of the body is an important took used by neurologist for testing functional integrity of the dorsal columns.

105
Q

What are position senses frequently called?

They can be divided into 2 Subtypes:

A

proprioceptive senses.

(1) static position sense, which means conscious perception of the orientation of the different parts of the body with respect to one another, and
(2) rate of movement sense, also called kinesthesia or dynamic proprioception.

106
Q

Define Thermal Sensations:

Name the 3 types of Receptors:

A

The human being can perceive different gradations of cold and heat, to burning hot- Via Thermal Receptors

  • Thermal gradations* are discriminated by at least three types of sensory receptors:
    1. cold receptors
    2. warmth receptors
    3. pain receptors
107
Q

What are Pain receptors stimulated by?

A

The pain receptors are stimulated only by extreme degrees of heat or cold and, therefore, are responsible, along with the cold and warmth receptors, for “freezing cold” and “burning hot” sensations.

108
Q

In Thermal Sensations.. where are “Cold and Warm” receptors located?

Which thermal senstation carries prominence along the area of the body?

A
  1. The cold and warmth receptors are located immediately under the skin at discrete separated spots.
  2. There are 3 to 10 times as many cold spots as warmth spots,
109
Q

What is the Peak for Cold receptor?

A

Peak for cold receptor is 24 deg. celcius

110
Q

What is the Peak for Hot receptor?

A

Peak for Hot receptor is 44 deg. Celcius

111
Q

Number of skin Temperature Receptors in %

Head

Trunk

Arms

Hands

Upper Legs

Lower Legs

A

Head 21%

Trunk 38%

Arms 13%

Hands 5%

Upper Legs 15%

Lower Legs 8%

112
Q
A

(MUL) Medical Physiology (11 decks)

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