Sensory Receptors

Question 1

what is the role of sensory receptors

Answer 1

change sensory stimuli (touch, temperature) into nerve signals that are then conveys to and processed in the CNS

Question 2

What is the role of mechanoreceptors

Answer 2

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

Question 3

What are the two types of sensibilities

Answer 3

skin tactile sensibilities (epidermis and dermis) and deep tissue sensibilities

Question 4

what mechanoreceptors are in the skin tactile sensibilities

Answer 4

• free nerve endings
• expanded tip endings
  merkels discs
  several others
• spray endings
• ruffians endings
• encapsulated endings
  meissners corpuscles
  krauses corpuscles
• hair end-organs

Question 5

what kind of mechanoreceptors are fun in deep tissue sensibilities

Answer 5

- free nerve endings
–  Expanded tip endings
–  Spray endings
•  Ruffini’s endings
–  Encapsulated endings
•  Pacinian corpuscles
•  Plus a few other variants
–  Muscle endings
–  Muscle spindles
–  Golgi tendon receptors

Question 6

Pacinis corpuscles

Answer 6

• largest mechanise receptor
• onion like encapsulation of nerve endings
• found in deep layers of the dermis and detects high frequency vibration ( 40-500Hz)
• Abeta fibres, glabrous and hairy skin types
• low activation threshold and is rapidly adaptive due to slick viscous fluid between layers

Question 7

meissners corpuscles

Answer 7

encapsulated nerve endings
stacks of discs interspersed with nerve branch endings
found between dermal papillae
touch flutter and low frequency vibration 2-40Hz
Abeta fibres and glabrous skin types
low activation threshold so is sensitive

Question 8

merkel discs

Answer 8

found just under the surface of the skin
consist of specialised epithelia cell + a nerve fibre
detect static touch and light pressure
nonencapsulated nerve endings
Abeta fibres and are in all skin types
slow adapting
work with meisners corupuscles to determine texture

Question 9

iggo dome

Answer 9

where multiple branches of Merkel disks are found

Question 10

Ruffini corpuscles

Answer 10

responds to skin stretch
located in the deep layers of the skin
encapsulated nerve endings and in all skin types especially abundant in hands and fingers as well as soles of the feet
nerve endings weave between collagen fibres which activate the nerve hen they are pulled longitudinaly

Question 11

skin hair receptors

Answer 11

mechanoreceptor is rapped around the hair follicle

detect muscular movements of the hair (erector) and external displacements of the hair

Question 12

what are the other functions of mechanoreceptors

Answer 12

•  Hearing
– Sound receptors of cochlea
•  Equilibrium – Vestibular receptors
•  Arterial pressure
– Baroreceptors of carotid sinuses and aorta

Question 13

thermoreceptors

Answer 13

which detect changed in temperature with some detecting cold and some detecting warm

Question 14

Nociceptors (pain receptors)

Answer 14

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

Question 15

electromagnetic receptors

Answer 15

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

Question 16

chemoreceptors

Answer 16

• detect taste in the mouth
• smelling the nose
• oxygen level in arterial blood
• osmolality of the body fluids
• carbon dioxide concentration

Question 17

chemoreceptor smell

Answer 17

– Receptors of olfactory epithelium

Question 18

chemoreceptor arterial o2

Answer 18

– Receptors of aortic and carotid bodies

Question 19

chemoreceptor Osmolality

Answer 19

– Neurons in or near supraoptic nuclei

Question 20

chemoreceptor blood co2

Answer 20

– Receptors in or on surface of medulla and in aortic and carotid
bodies

Question 21

chemoreceptor Blood glucose, amino acids, fatty acids

Answer 21

– Receptors in hypothalamus

Question 22

change in electrical potencial is also called receptor potential

Answer 22

receptor potential

Question 23

what can receptor potential be generated by

Answer 23

– Mechanical deformation which stretches the receptor membrane and also opens ion channels.
– Application of a chemical to the membrane which opens ion channels.
– Change in membrane temperature which changes the permeability of the membrane.
– Effects of electromagnetic radiation eg light on visual receptor which changes receptor membrane characteristics allowing ions to flow through membrane channels.

Question 24

what happens when compression occurs

Answer 24

corpusle will elongate, indent or deform the central fibre.

cTip unmyelinated, then fibre myelinated shortly before leaving corpuscle.

Question 25

why does amplitude if receptor potential change in compression

Answer 25

progressively stronger mechanical compression applied to central core of Pacinian Corpuscle.

Question 26

in what fashion is sensory information delivered to the CNS

Answer 26

topographic fashion

Question 27

Phantom limb sensation

Answer 27

arises when sensory neurons from absent limbs are spontaneously active, and can be mimicked by electrical stimulation

Question 28

The precision of localisation of a particular stimulus is determined by:

Answer 28

– the size of the individual nerve fibre receptive field. – the density of sensory units
– the amount of overlap in nearby receptive fields.

Question 29

Receptor field overlap

Answer 29

• Aids stimulus localisation (even though it could be thought to “muddy” the image).

Question 30

Variations in the results of the two point discrimination test

Answer 30

• seen across different regions the body
• are a result of the receptive field size and receptor density in the area.
• This does not represent sensitivity to stimulus

Question 31

Lateral inhibition

Answer 31

• Aids in enabling localisation of stimulus.
• Information from afferent neurons whose receptors are at edge of a stimulus are strongly inhibited compared to information from the stimulus’ centre.

Question 32

Implications of the size range in receptive fields

Answer 32

The smaller the receptive field is, the better the linear discrimination between stimuli is
This is not the same as high sensitivity

Question 33

Why are not all areas of the body given high linear discrimination ?

Answer 33

High linear discrimination needs more sensory fibres/neurons to cover the area with small receptive fields
There is no requirement for the torso to be able to have that level of discrimination, and the extra neurons would present a space problem in the spinal cord

Question 34

where does sensory information go in the brain

Answer 34

passes through the thalamus and on to the primary sensory cortex which is located in a strip posterior to the post central sulcus of the brain.
• Sensory information is projected in a topographical manor to this area, with areas of higher discrimination having a larger proportion of the space.