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Physiology MD2002 > Sensory Receptors > Flashcards

Sensory Receptors Flashcards

1
Q

What is the role of sensory receptors?

A

They change sensory stimuli (touch/temp) into nerve signals that are then conveyed to and processes in the CNS

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2
Q

Name the 5 basic types of sensory receptors

A

1) Mechanoreceptors -
2) Thermoreceptors
3) Nociceptors (pain receptors)
4) Electromagnetic receptors
5) Chemoreceptors

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3
Q

Describe the function of mechanoreceptors

A

1) Mechanoreceptors - detect mechanical compression or stretching of the receptor or tissue adjacent to the receptor

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4
Q

Describe the function of thermoreceptors

A

Thermoreceptors - Detect changes in temperature with some detecting cold and some warmth.

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5
Q

Describe the function of nociceptors

A

3) Niciceptors (pain receptors) - detect physical or chemical damage occurring in tissue (free nerve endings)

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6
Q

Describe the function of electromagnetic receptors

A

4) Electromagnetic receptors - Detect light on the retina of the eye

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7
Q

Describe the function of chemoreceptors

A

Chemoreceptors - Detect taste in mouth, smell in nose, oxygen levels in arterial blood, osmolality in body fluids and other factors that make up chemistry of the body.

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8
Q

Name the two types of mechanoreceptors

A

Skin tactile sensibilities (in the dermis and epidermis)

Deep tissue sensibilities

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9
Q

Name the types of endings in skin tactile sensibilities

A

Free nerve endings, expanded tip endings (eg, merkel’s discs), spray endings (Ruffini’s endings), Encapsulated endings (Meissner’s corpuscles and Krause’s corpuscles) and finally Hair end-organs

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10
Q

Name the types of endings in deep tissue sensibilities

A

Free nerve tip, expanded tip endings, spray endings (Ruffini’s endings), Encapsulated endings (eg, Pacinian corpuscles) - Same as skin tactile
Others are Muscle endings, Muscle spindles and golgi tendon receptors.

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11
Q

Describe some of the features of the pacinian corpuscles

A
  • Largest mechanoreceptor
  • Found in deep layer of the dermis
  • Detects high frequency vibrations
  • A,beta fibres found in both glabrous and hairy skin
  • Rapidly acting due to slick viscous layers
  • Low activation threshold meaning it is sensitive
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12
Q

Describe some of the features of Meissner’s corpuscles

A
  • Encapsulated nerve endings similar to pacini’s but are much smaller.
  • They have stacks of discs with nerve branches between them
  • Found between dermal papillae and detect low frequency vibrations, flutters and touch
  • A,Beta fibres found in glabrous skin types
  • Low activation threshold so its sensitive
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13
Q

Describe some of the features of Merkel Disks (structure, fibres, adaptation ect)

A
  • Non-encapsulated nerve endings which detect static tough and light pressure
  • A,beta fibres found in all skin types
  • Slowly adapting
  • Found just under the skin and are good for discrimination
  • They have multiple branches found in ‘iggo dome
  • Work with meissner’s corpuscles
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14
Q

Describe some of the features of Ruffini Corpuscles (Response, location ect)

A

They respond to skin stretch and are located in deep layers of the skin as well as tendons sand ligaments.
Encapsulated nerve endings found in all skin types. The nerve endings weave between collagen fibres which activate them when pulled longitudinally.

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15
Q

Describe some of the features of skin hair cell receptors

A

Mechanosensitive receptors wrapped around its follicle. It detects muscular movement of erector muscle and external displacement of hair

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16
Q

Where are other places you can find mechanoreceptors?

A
  • In the ear where they act as sound receptors of the cochlea
  • Vestibular receptors which are found in the ear and help balance
  • Baroreceptors in coratid sinus and aorta to regulate arterial pressure
17
Q

Where will you find chemoreceptors and what to they respond to?

A
  • Receptors of taste buds, respond to taste
  • Receptors of olfactory epithelium to respond to smell
  • Receptors of aortic and carotid bodies that respond to arterial oxygen
  • Receptors near/in supraoptic nuclei to respond to osmolality
  • Receptors on/in medulla and in the aortic and carotid bodies to respond to blood CO2
  • Receptors in hypothalamus to respond to blood glucose, amino acids and fatty acids
18
Q

Once a receptor is stimulated what is the immediate effect?

A

A change to the membrane electrical potential, this is called the receptor potential

19
Q

What is another word for receptor potential?

A

Generator potential

20
Q

A receptor/generator potential can be created by?

A

Mechanical deformation which stretches receptor membrane and opens ion channels

  • Application of chemical to membrane which opens ion channels
  • Change in membrane temp which changes permeability
  • Effects of electromagnetic radiation
21
Q

What occurs when the receptor potential rises above the threshold?

A

An action potential occurs in the nerve fibres attached to the receptor

22
Q

What occurs with a larger receptor potential?

A

Larger receptor potentials means a greater action potential frequency

23
Q

Describe the relationship between the stimuli intensity and the action potential

A

The greater the intensity of a stimuli then the higher the frequency of the action potentials in the sensory nerve which is traveling to the CNS

24
Q

How does the body know the modality of a stimuli? (whether its pain or touch or light ect) and what is this called?

A

Because the nerves terminate at a specific point in the CNS and therefore the type of sensation felt is determined by the point in the CNS where the fibre leads. This is called the Labelled Line Principle

25
Q

Modal info is delivered to the CNS in a topographic fashion. What does this mean?

A

It means that pain felt from an area will be delivered to the part of the CNS that recivies info about stretch of vibrations from that area.

26
Q

What does the adaptation of a receptor mean?

A

It refers to the reduction in sensitivity for a stimuli after constant exposure from the stimuli.

27
Q

What does it mean if a receptor is rapidly adapting

A

It means that they will stop producing action potentials quickly when exposed to a constant stimuli

28
Q

What is the precision of localisation of a stimuli determined by?

A
  • Size of the individual nerve receptor feild
  • The density of sensory unit
  • The amount of overlap in nearby receptor fields because it allows for a larger amount of firing
29
Q

What allows for a higher resolution? in terms of picking up different signals?

A

Having a variation of receptors all across the skin - increases the number of modalities felt

30
Q

What areas of the skin have good two point discrimination and what areas have poor two point discrimination?

A

Good - Hands and face

Poor - trunk

31
Q

What is the function of lateral inhibition and how does it work

A

Function - Aids in localisation of stimuli
Works - The neurons whose receptors are at an edge of a stimuli are strongly inhibited compares to the neuron at the centre of a stimuli. Neurons weakly stimulated send weak inhibition, while neurons strongly stimulated will send out strong inhibition

32
Q

What does a small receptor field provide?

A

A better linear discrimination (not the same as sensitivity though)

33
Q

Why does the torso not have high linear discrimination

A

Because there is no need for it and the extra neurons that are required would cause a space issue in the spinal cord

34
Q

Describe the neural patheays of the somatosensory system

A

Primary afferent is a first order neuron which terminates in the spinal cord or brain stem.
The second order neuron projects to the thalamus and the third order neuron projects to the brain.

35
Q

Where does the sensory information travel too?

A

Through the thalamus to the primary sensory cortex which is a strip located posteriorly to the central sulcus of the brain.

36
Q

How are sensory nerves arranged?

A

Segmentally, view a picture

Physiology MD2002 (33 decks)

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