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Semester 2 Molecular Medicine > Sensory receptors > Flashcards

Sensory receptors Flashcards

1
Q

What are the 5 basic types of sensory receptors?

A
  1. Mechanoreceptors
  2. Thermoreceptors
  3. Nociceptors (pain)
  4. Electromagnetic receptors
  5. Chemoreceptors
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2
Q

What are the types of Chemoreceptors?

A
  • Taste: receptors of taste buds
  • Smell: receptors of olfactory epithelium
  • Arterial oxygen: receptors of aortic and carotid bodies
  • Osmolality: neurones in or near supraoptic nuclei
  • Blood Co2: receptors on or in the medulla and in aortic bodies
  • Blood glucose, amino acids, fatty acids: receptors in hypothalamus
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3
Q

Describe the formation of a receptor potential of a receptor of the Pacinian corpuscle

A
  • Compression changes the membrane and opens the channels allowing more sodium ions to move into the fibre- this is the receptor potential which creates a local current flow within the area
  • Greater stimulus= greater amplitude of the receptor potential
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4
Q

What happens in a pacinian corpuscle after the local current has been created

A

• Local current flow causes depolarisation at the first node of ranvier and this causes the action potential

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5
Q

What happens when there is a low stimulus in comparison to a greater intensity stimulus (touch)

A

An increased frequency of action potentials

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6
Q

What happens when there is a low stimulus in comparison to a greater intensity stimulus (touch)

A

An increased frequency of action potentials

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7
Q

How can we tell the modality of sensation

A

Depends on where the nerve terminates in the CNS

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8
Q

How does phantom limb sensation arrive?

A

When sensory neurones from absent limbs are spontaneously active and can be mimicked by electrical stimulation

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9
Q

Which receptors are rapidly adapting?

A
  • Hair follicles
  • Meissner corpuscle
  • Pacinian corpuscle
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10
Q

Which receptors are slow acting?

A
  • Merkel cell-neurite complex
  • Ruffini corpuscle
  • C-fibre LTM
  • Mechano-noiceptor, polymodal noiceptor
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11
Q

What determines the precision of localisation of a particular stimulus?

A
  • Size of the individual nerve fibre receptive field
  • Density of sensory units
  • Amount of overlap in nearby receptive fields
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12
Q

If there is a greater overlap, how does this influence the precision of localisation

A

It decreases it

Although it aid stimulus localisation it is thought to muddy the image

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13
Q

What is the role of lateral inhibiton?

A

• Aids in enabling localisation of the stimulus

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14
Q

How does lateral inhibition work?

A

• Information from afferent neurones whose receptors are at edge of a stimulus are strongly inhibited compared to information from the stimulus’ centre

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15
Q

What is a mechanoreceptor?

A

Receptor that detects mechanical compression or stretching of the receptor or the tissues adjacent to the receptor

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16
Q

What are the skin tactile sensibilities (epidermis and dermis)?

A
  • Free nerve endings
  • Expanded tip endings (Merkel’s disks)
  • Spray endings
  • Ruffini’s endings
  • Encapsulated endings (meissner’s corpuscles, Krause’s corpuscles)
  • Hair-end organs
17
Q

What are the deep tissue sensibilities?

A
  • Free nerve endings
  • Expanded tip endings
  • Spray endings (Ruffini’s)
  • Encapsulated endings (pacinian)
  • Muscle endings
  • Muscle spindles
  • Golgi tendon receptors
18
Q

Pacini’s corpuscles

A
  • Largest
  • 2mm
  • AB fibres
  • In the deep layers of the dermis
  • High frequency (40-500Hz)
  • High sensitivity - low activation threshold
  • Glabrous and hairy skin types
  • Slick viscous fluid between the layers
19
Q

Meissner’s corpuscles

A
  • Encapsulated nerve endings
  • Stacks of discs interspersed with nerve branch endings
  • Found between the dermal papillae
  • Detects touch, flutter and low frequencys (2-40Hz)
  • AB fibres
  • Glabrous (non-hairy) skin types
  • Low activation threshold - sensitive
  • Work with merkel discs to help determine texture
20
Q

Merkel discs

A
  • Non-encapsulated nerve endings
  • Detect static touch and light pressure
  • AB fibres
  • All skin types
  • Specialised epithelial cell and nerve fibre
  • Slowly adapting
  • Found just under the skins surface
  • Multiple branches are often found in an ‘iggo dome’
  • Work with meissners corpuscles to help determine texture
21
Q

Ruffini corpuscles

A
  • Responds to skin stretch
  • Located in the deeper layers of the skin as well as the tendons and the ligaments
  • Encapsulated nerve endings
  • all skin types
  • Abundant in hands, fingers and soles of the feet
  • Nerve endings weave between collagen fibres which activate the nerve when pulled longitudinally
22
Q

Skin hair receptors

A
  • Each type of skin hair receptor has a mechxnosensitive receptor wrapped around its follicle
  • Detects muscular movements of the hair (erector muscle)
  • Detects the external displacement of the hair
23
Q

How do we hear?

A

Sound receptors of the cochlea

24
Q

How do we sense equilibrium?

A

Vestibular receptors

25
Q

How do we sense arterial pressure?

A

Baroreceptors of carotid sinuses and aorta

26
Q

Thermoreceptors

A

Detect changes in temperature, some detect cold, some detect warmth

27
Q

Nociceptors

A

Detects physical or chemical damage occurring in the tissues; free nerve endings

28
Q

Electromagnetic receptors

A

Detect light on the retina of the eye; vision via rods and cones

29
Q

Chemoreceptor

A

Detects taste, smell, oxygen in arterial blood, osmolality of the body fluids, carbon dioxide concentration and other factors

30
Q

What is a receptor potential?

A

The change in the membrane electrical potential when the receptor is stimulated

31
Q

How can a receptor potential be created?

A
  • Mechanical deformation- stretches the receptor membrane and opens ion channels
  • Application of a chemical to the membrane which opens ion channels
  • Change in membrane temperature which changes the membrane permeability
  • Effects of electromagnetic radiation e.g. light on a visual receptor which changes the receptor membrane characteristics, allowing ions to flow through the membrane channels
32
Q

How do signals from sensory nerve endings get to the CNS?

A
  • Frequency is directly related to its amplitude at any moment
  • non damaging stimulus: coded by the frequency of action potentials in the sensory nerve
33
Q

What is labelled line principle?

A

Nerves terminate at a specific point in the CNS and there type of sensation felt is determined by the point in the nervous system to which the fibre leads

34
Q

how is information delivered to the CNS?

A

In a topographic fashion

35
Q

What causes 2 point discrimination?

A
  • Receptive field size

* Receptor density in the area

36
Q

The smaller the receptive field…

A

… The better the liner discrimination between stimuli is

37
Q

What is needed for high linear discrimination?

A

More sensory fibres/neurones to cover the area with small receptive fields

38
Q

Why do we not have high linear discrimination all over the body?

A
  • Not needed in certain areas e.g. the torso

* Would cause an issue with space in the spinal cord

39
Q

How is some space saved in places that have a high linear discrimination?

A

• Multiple same modality sensory neurones with overlapping fields all project to a single ascending neurone

Semester 2 Molecular Medicine (27 decks)

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