Exam #1: Neurohistology Flashcards Preview

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Flashcards in Exam #1: Neurohistology Deck (48)
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1
Q

What are sensory receptors the beginning of?

A
  • Sensory pathways to the brain

- Spinal cord reflex arc

2
Q

Where are sensory neurons located?

A

DRG

Ganglia of cranial nerves

3
Q

What part of the sensory neuron contains the peripheral sensory receptors?

A

Dendrites of sensory neurons i.e. the peripheral end of the sensory neuron

4
Q

What are the two types of sensory neurons that have sensory receptors?

A

Bipolar neurons

Pseudounipolar neurons

5
Q

What are bipolar neurons associated with?

A

Special senses:

1) Smell
2) Vision
3) Balance
4) Hearing

6
Q

What is the difference between olfactory & retinal/ vestibular/ cochlear receptors?

A

Olfactory receptors ARE the bipolar neurons

  • In the other two, bipolar neurons SYNAPSE with sensory receptors (rods/cones & hair cells)
7
Q

Where are pseudounipolar neurons located?

A

Not special senses

8
Q

Describe the two different structural phenotypes of the pseudounipolar terminal.

A
  • Naked

- Encapsulated

9
Q

What are multipolar neurons? Do multipolar neruons have sensory receptors?

A

No

10
Q

What is a sensory receptor?

A

Specialized terminal at the distal end of a sensory nerve

*Note that sensory receptors generally carry more than one modality

11
Q

What are the four modalities only carried by the cranial nerves?

A

1) Olfaction
2) Vision
3) Gustation (taste)
4) Audition

12
Q

What are the four modalities carried by cranial & spinal nerve?

A

1) Tactile sensation
2) Nociception
3) Temperature
4) Proprioception

13
Q

What are the three general classifications of tactile sensation?

A

1) Touch
2) Pressure
3) Vibration

14
Q

What are the two different types of touch?

A
  • Light touch

- Discriminative i.e. fine/ detailed touch

15
Q

What happens at the receptor when a stimulus is applied?

A

Conversion of the stimulus to an electrical signal

16
Q

What happens at the nerve terminal in response to an electrical signal from a receptor?

A

Generation of an action potential

17
Q

What is the receptive field of a receptor?

A

Region that a receptor is able to convert stimulus into a receptor potential i.e. region from which stimulation results is signal transduction

18
Q

Where are there large numbers of sensory receptors? Where are there relatively few sensory receptors?

A
  • Skin of face & hand have a large number of receptors

- Skin of other body parts has few receptors

19
Q

How do receptors with a wide receptive field compare to receptors with a narrow receptive field?

A

Precision of perception

  • Wide= less precise
  • Narrow= more precise
20
Q

What are exteroreceptors? What are the two categories of exteroreceptors?

A

Receptors located close to the surface of the body:

1) Teloreceptors
2) Contact receptors

21
Q

What is a teloreceptor?

A

Exoreceptors that can be activated at a distance e.g.

  • Light–rods/cones
  • Sound–auditory hair cells
22
Q

What are contact receptors?

A

Exoreceptors that require contact

  • Touch
  • Pressure
  • Pain
  • Temp
  • Chemicals
23
Q

What are examples of contact receptors?

A
  • Olfactory
  • Taste
  • Tactile
24
Q

Where are proprioceptors located?

A
  • Vestibular apparatus i.e. the inner ear
  • Skin
  • Muscles
  • Tendons
  • Joint capsules
25
Q

What are the two types of proprioception?

A

1) Static= stationary

2) Kinetic= moving

26
Q

What are interoreceptors?

A

Receptors found deep in the body or brain

27
Q

What are the two categories of interoreceptors? List examples.

A

Chemoreceptors

  • Hypothalamus
  • Carotid body

Baroreceptors
- Carotid sinus in urinary bladder

28
Q

What are the three classifications of receptors according to modality

A

1) Nociceptors- Aδ or C fibers
2) Thermoreceptor- Aδ or C fibers
3) Machanoreceptors- Aβ

Thus, mechanoreceptors are associated with faster conduction velocities/ fiber types

29
Q

What are the different types of nociceptors? What fiber types are these receptors associated with?

A

1) Mechanosensitive= injury- Aδ
2) Temperature= heat or cold- Aδ
3) Polymodal= respond to various noxious stimuli- C
4) Pruriceptors= itching that respons to histamine, associated with C fibers

30
Q

What are the non-encapsulated mechanoreceptors?

A
  • Free nerve endings
  • Peritrichial nerve ending= around hair follicle
  • Merkel Disc= dialated & naked pseudounipolar dendrite

*****Associated with Aβ fibers

31
Q

What are the encapsulsed mechanoreceptors?

A

Meissner corpuscle= dermal papillae–light touch
Pacinian corpuscle= in skin–vibration & pressure
Ruffini end organ= joint–proprioception
Muscle spindle
Golgi tendon

32
Q

What is a muscle spindle?

A

Specialized mechanoreceptor (proprioceptor) unique to skeletal muscle that monitors muscle length

33
Q

What is an extrafusal fiber?

A
  • This is a typical skeletal muscle fiber that forms the gross muscle
  • Innervated by alpha motor neurons to produce contraction
34
Q

What are nuclear bag and nuclear chain fibers?

A

These are the two different intrafusal or muscle spindle fiber types i.e. the inner components of the muscle spindle

  • Differences are based on morphology
  • Have contractile & non-contractile properties
35
Q

What is the function of nuclear chain fibers?

A

Detect static changes in muscle length

36
Q

What is the function of nuclear bag fibers?

A

Detect static & dynamic changes in muscle length

  • Static= detects changes in muscle length
  • Dynamic= detect the rate of change
37
Q

What is an annulospiral ending?

A

Intrafusal fibers receive two types of sensory innervation, one of which is in the form of annulospiral endings

  • Annulopsiral respond to the onset of muscle stretch
  • Type Ia
38
Q

What is a flower spray ending?

A

This is the second type of sensory innervation to intrafusal fibers

  • Flower spray fibers are activated when muscle stretch is in progress
  • Type II
39
Q

What is the golgi tendon organ?

A

This is a specialized mechanoreceptor located where the muscle inserts into its tendon; the function of the GTO is to monitor the amount of tension applied to a tendon

40
Q

What happens in response to a central CNS lesion? Why?

A

No regeneration b/c:

1) Schwann cell are needed to tell axons don’t know where to go–NOT present in CNS
2) Oligodendrocytes INHIBIT axon growth
3) Astrocytes don’t make enough growth factor & form scar tissue

*****No regeneration & permanent neurologic deficits

41
Q

What is a receptor potential?

A

Electrical signal produced in response to stimulation of a sensory nerve

42
Q

What is sensory transduction? How does this differ from a receptor potential?

A

Sensory transduction is the actual conversion of a stimulus into an electrical signal (vs. the receptor potential, which is the electrical signal)

43
Q

What is an Aα fiber?

A
  • Myelinated fibers

- Fastest

44
Q

What is the difference between Type Ia & Ib Aα fibers?

A

Both are myelinated

  • Ia= form annulospiral endings innervating muscle spindles
  • Ib= innervate golgi tendon organs (GTO)
45
Q

What are Aβ or Type II fibers?

A

Myelinated fibers from flower spray endings

46
Q

What are Aδ or Type III fibers?

A

Lightly myelinated fibers that relay:

  • Pain
  • Temperature
  • Crude touch

*****Note that the pain signals transmitted by these fibers are “sharp & well localized (vs. C)

47
Q

What are C or Type IV fibers?

A

UNMYELINATED fibers that relay:

  • Pain
  • Temperature
  • Touch

*****Note that the pain signals transmitted by these fibers are “dull & poorly localized (vs. Aδ) & this is the SLOWEST fiber type

48
Q

What is the difference between cold and warm receptors in terms of fiber type?

A
Cold= Aδ
Warm= C