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Nervous System Biology > NSB 6. Sensory Receptors and Pathways > Flashcards

NSB 6. Sensory Receptors and Pathways Flashcards

1
Q

What are Receptors? (definition)

A

they are TRANSDUCERS that convert external or internal STIMULI into ELECTRICAL POTENTIALS

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2
Q

What are Sensory Pathways? (definition)

A

they carry information from RECEPTORS to CNS integrating centres

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3
Q

What are the 2 types of receptors that turn stimuli into electrical signals?

A

[1] Central Receptors

[2] Peripheral Receptors

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4
Q

What type of receptor is more complicated?

A

Central Receptors are more complicated than Peripheral Receptors.

  • central receptors have multiple cell types that work together
  • peripheral receptors have individual cell types
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5
Q

What is the relay nucleus?

A

it is where the 1st and 2nd neuron synapse

- after the relay nucleus the 2nd neuron may decussate

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6
Q

What are the types of mechanoreceptors for?

A

[1] Touch
[2] Audition
[3] Vestibular (balance)

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7
Q

What is the receptor type for touch?

A

pacinian corpuscle

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8
Q

What is the receptor type for audition?

A

hair cell

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9
Q

What is the receptor type for vestibular (balance)?

A

hair cell

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10
Q

Where are the receptors for touch located?

A

skin

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11
Q

Where are the receptors for audition located?

A

organ of corti

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12
Q

Where are the receptors for vestibular stimuli located?

A

macula, semicircular canal

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13
Q

What are the photoreceptors for?

A

for vision

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14
Q

What is the receptor type for photoreceptors?

A

rods and cones

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15
Q

Where are the receptors for photoreceptors located?

A

retina

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16
Q

What are the types of chemoreceptors?

A

[1] Olfaction
[2] Taste
[3] Arterial pO2
[4] pH of CSF

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17
Q

What are the receptors for olfaction stimuli called?

A

olfactory receptor

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18
Q

Where are the olfactory receptors located?

A

olfactory mucosa

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19
Q

What are the receptors for taste stimuli called?

A

taste buds

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20
Q

Where are the receptors for taste located?

A

tongue

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21
Q

Where are the arterial pO2 receptors located?

A

carotid + aortic body

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22
Q

Where are the receptors to measure the pH of CSF located?

A

ventrolateral medulla

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23
Q

What are the receptors for thermoreceptors called?

A

temperature receptors – cold/warm receptors

24
Q

Where are the thermoreceptors located?

25
Q

What are nociceptors used for? What are the different types of nociceptors?

A
  • extremes of pain and temp.

[1] Thermal Nociceptors
[2] Polymodal Nociceptors

26
Q

Where are the nociceptors located?

27
Q

What are the 3 types of sensory receptors?

A

[1] Simple Neural Receptor
[2] Complex Neural Receptor
[3] Special Senses Receptor

28
Q

List some of the characteristics of the simple neural receptor.

A
  • unmyelinated (impulses are quite slow)
  • has free nerve endings
  • e.g. pain receptor
29
Q

List some of the characteristics of a complex neural receptor.

A
  • myelinated (fast impulses)
  • enclosed nerve ending by layers of connective tissue
  • e.g. mechanoreceptors (pacinian corpuscle)
30
Q

List some of the characteristics of a special senses receptor.

A
  • has specialized receptor (e.g. hair cell)
  • has a synapse between the specialised receptor and neuron
  • myelinated (fast impulses)
  • e.g. hair cells in the auditory system
31
Q

List the most important receptors in the skin. [5]

A 
[1] Hair Receptor
[2] Merkel's Disc
[3] Pacinian Corpuscle
[4] Ruffini Endings
[5] Meissner's Corpuscle
32
Q

What are the traits and characteristics of hair receptors in the skin?

A
  • fast adapting
  • – react really quickly and then they return to normal (e.g. displacement of the hair)
  • located in hairy skin
33
Q

What are the traits and characteristics of merkel’s disc receptors in the skin?

A
  • they have open nerve endings
  • found in hairy + non-hairy skin
  • they respond to indentation (e.g. pressing on the skin)
34
Q

What are the traits and characteristics of pacinian corpuscle receptors in the skin?

A
  • most rapidly adapting
  • they encode vibration
  • found in both hairy and non-hairy skin
35
Q

What are the traits and characteristics of ruffini endings receptors in the skin?

A
  • they are activated by stretching of skin

- found in both hairy and non-hairy skin

36
Q

What are the traits and characteristics of meissner’s corpuscle receptors in the skin?

A
  • they are abundant in the fingertips and lips
  • they are for fine touch
  • they are found in non hairy skin (!)
37
Q

What are receptive fields?

A

Definition: a receptive field defines an area of the body that when stimulated results in a change in firing rate of a sensory neuron

  • — basically a part of the body that is supplied by the neuron
  • receptive fields exist for 1, 2 and 3 order neurons
  • you can have overlapping receptive fields
38
Q

Can you have overlapping receptive fields?

A

Yes

- for example, one area may have more than one sensory receptor there

39
Q

What is the difference between a small and a large receptive field?

A

Small Receptive Field:
- the patch of skin is innervated by only ONE sensory receptor

Large Receptive Field:

  • the patches of skin are innervated my multiple sensory receptors
  • the sensory receptors all synapse onto the same 2nd order neuron
  • think of it as a duster (it spreads out like that)
40
Q

What is the purpose of both excitatory and inhibitory receptive fields to synapse on the same 2nd order neuron?

A

in order for the brain to have a better idea where the stimulus is coming from (increase in accuracy), they have inhibitory receptive fields
– they inactivate the 2nd order neuron

41
Q

What is 2-point discrimination?

A

it is to determine how finely innervated an area of skin is

  • if the 2 points only send ONE signal to the brain, this means that the primary sensory neurons merge into the same 2nd order neuron
  • if the 2 points send 2 separate signals to the brain, this means that the primary sensory neurons do not merge into the same 2nd order neuron
42
Q

The intensity of a stimulus is encoded in 3 ways which are:

A

[1] # of receptors activated
[2] difference in firing rates of sensory neurons
[3] activation of different types of receptors

43
Q

What are tonic receptors?

A
  • they fire as long as the stimulus is present at threshold levels
  • they do not stop firing
  • e.g. baroreceptors, nociceptors, merkel’s receptors
44
Q

What are phasic receptors?

A
  • they fire at stimulus onset, but they adapt or cease to fire when constant (steady state) stimulus
  • they filter out unnecessary stimuli to focus on new, essential info
  • e.g. olfactory receptors, pressure, pacinian corpuscle
  • – for example, you don’t smell a smell anymore
45
Q

Describe the structure and location of primary sensory afferents?

A
  • the cell body is in the dorsal root ganglion
  • axon part connects with the sensory receptor
  • the other part of the sensory afferent transmits the info from the receptor into the dorsal horn of the spinal cord
46
Q

What are the 3 types of polarity of neurons?

A

[1] Multipolar Neuron
- most abundant
[2] Bipolar Neuron
[3] Unipolar Neuron

47
Q

What are the 2 types of fibre types? How do they differ?

A

[1] Proprioception, Vibration + Discriminative Touch
- travels in HEAVILY MYELINATED, LARGE DIAMETER, FAST conducting peripheral nerve fibres (A-alpha and A-beta)

[2] Pain, Temperature
- travels in THINLY MYELINATED + UNMYELINATED, MODERATE to SLOWLY conducting peripheral nerve fibres (A and C)

48
Q

What is the spinothalamic pathway important for?

A

pain + temperature

49
Q

Explain how the spinothalamic pathway works.

A

[1] 1st order neuron recieves the stimulus

[2] the 1st order neuron axons transmit from receptor to spinal cord via dorsal root
- they synapse in dorsal horn of spinal cord (with the 2nd order neuron)

[3] 2nd order neuron cross the spinal cord in anterior commissure
- they cross the midline (decussate)

[4] the 2nd order neuron ascend in the contralateral spinothalamic tract

[5] 2nd order neurons synapse with 3rd order neurons in thalamus

[6] the 3rd order neurons have axons that project from the thalamus to sensory cortex

50
Q

What is the dorsal column/medial lemniscus system important for?

A

encodes for proprioception (only in arms, not in legs), vibration, discriminative touch

51
Q

Explain how the dorsal column-medial lemniscal pathway works. (this one is a little more complicated)

A

LUMBAR CORD: for LOWER LIMBS
[1] 1st order neuron enters the lumbar cord and travels up the spinal cod until it meets the NUCLEUS GRACILIS in the medulla

[2] at the nucleus gracilis, the 2nd order neuron decussates in the lower medulla and goes to the thalamus

[3] the 2nd order neuron travels up into the thalamus where it synapses with the 3rd order neuron

[4] the 3rd order neurons have axons that project from the thalamus to sensory cortex

CERVICAL CORD: for UPPER LIMBS
[1] the 1st order neuron travels up until it meets the NUCELUS CUNAEUS in the medulla

[2] at the nucleus cunaeus, the 2nd order neuron decussates in the lower medulla and goes to the thalamus

[3] the 2nd order neuron synapses in the thalamus

[4] the 3rd order neurons have axons that project from the thalamus to sensory cortex

52
Q

What is the spinocerebellar pathway important for?

A

it is for unconscious proprioception

  • it does NOT pass through the thalamus
  • it is a 2 neuron pathway
  • it provides info to the cerebellum about the position of the body in space
53
Q

How is the spinocerebellar pathway different than the other 2 pathways?

A

it is for unconscious activites and so, the neurons do NOT pass through the thalamus
- and it only has 2 neurons in its pathway

54
Q

What are the 3 main neuron pathways/system?

A

[1] Spinothalamic Pathway/Anterolateral System
[2] Dorsal-Column-Medial Lemniscal System
[3] Spinocerebellar Pathway

55
Q

Explain how the spinocerebellar pathway works. (this one is a little more complicated)

A
  1. UNCONSCIOUS PROPRIOCEPTION OF UPPER LIMBS
    [a] 1st order neuron carries impulse into spinal cord through dorsal root where it enters FASCICULUS CUNEATUS

[b] 1st order neuron continues to carry impulse upwards in CUNEOCEREBELLAR TRACT terminating in the ACCESSORY CUNEATE NUCLEUS in medulla

[c] 1st order neuron synapses with 2nd order neuron in medulla

[d] 2nd order neuron carries impulse to ipsilateral (same side) cerebellum through the inferior cerebellar peduncle

[e] the 2nd order neuron continues to carry the impulse to the appropriate region of the cerebellar cortex

  1. UNCONSCIOUS PROPRIOCEPTION OF LOWER LIMBS
    [a] 1st order neuron enters spinal cord through dorsal root where it enters the FASCUCULUS GRACILIS

[b] the axon of the 1st order neuron ascends for a number of segments util it reaches CLARKES COLOUMN

[c] 2nd order neurons arising in Clarkes Coloumn carry the impulse and enter the ipsilateral (same side) DORSAL SPINOCEREBELLAR TRACT

[d] the 2nd order neuron continues upwards towards the medulla through the dorsal spinocerebellar tract

[e] from the medulla, the 2nd order neuron entesr the ipsilateral (same side) CEREBELLUM via the inferior cerebellar peduncle

[f] the 2nd order neuron carries the impulse to an inappropriate area of the cerebellar cortex

56
Q

What is convergence and divergence of sensory input along the spinothalamic pathway? Why is it important?

A

CONVERGENCE: a # of 1st order neurons synapse into a single 2nd order neuron

DIVERGENCE: only one 1st order neuron supplies multiple 2nd order neurons

  • it influences the quality of the sensation at the conscious/subconscious level within the CNS
57
Q

What are the 2 types of unconscious perceptions?

A

[1] Somatic Stimuli
- muscle length/tension

[2] Visceral Stimuli

  • blood pressure
  • blood + CSF + pH
  • blood pO2
  • body fluid osmolarity
  • temperature
  • blood glucose
  • GIT distension
  • lung inflation

Nervous System Biology (4 decks)

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