Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Neuroscience 🧠 > Chapter 12: Somatic Sensory System > Flashcards

Chapter 12: Somatic Sensory System Flashcards

The Somatic Sensory System

1
Q

Introduction

Describe the Somatic Sensation and its characteristics

A
  • Responsible for touch, itch & pain.
  • Receptors are broadly distributed (not all in one location)
  • Responds to many kinds of stimuli (Many different types of primary receptor cells)
  • Divided into two major subtypes
    1. Mechanosensory: touch & body position.
    2. Temperature & Pain
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Introduction

Whate are the four groups of somatosensory receptors

A

Based on Function
1. Mechanoreceptors
2. Nociceptors (pain)
3. Pruriceptors (itch)
4. Thermoreceptors (temperature)

Based on Morphology
1. Free nerve endings (unmyelinated terminal branches)
- Nociceptors (pain)
- Pruriceptors (itch)
2. Encapsulated
- mechanoreceptors for touch

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Introduction

What are the steps of sensory transduction

A
  1. Stimuli deforms (comes in contact) w/ skin
  2. Receptors detect stimuli
  3. Receptor potential is generated in those nerve endings
  4. Nerve endings are depolarized and generates action potentials
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Mechanoreceptors

What are the characteristics for Mechanoreceptors’s receptive fields?

A

Mechanoreceptors vary in their preferred stimulus properties, pressures, and RFs.
* Specific area of skin where it can transduce pressure or vibration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Mechanoreceptors

What are the four types of receptive fields for Mechanoreceptors and their adaptation and size?

A
  • Meissner’s Corpuscle: Small receptive field and Rapid adpation
  • Pacinian Corpuscles: Large receptive field and Rapid adaptation
  • Merkel’s Disk: Small receptive field and Slow adaptation (action potential all the time)
  • Ruffini’s Ending: Large receptive field and Slow adaptation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Mechanoreceptors

What are the Characteristics of Pacinian corpuscles

A
  • Has a football shaped capsule with layers of connective tissue.
  • Generates a large receptor potential at stimulus onset and offset but rapidly adapting
  • bare axons generate a receptor potential that is more slower adaptation rate
  • deformation of axon is key to response
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Mechanoreceptors

what do mechanosensitive ion channels do?

A
  • Mechanosensitive ion channels convert mechanical force into change of ionic current
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Mechanoreceptors

What is two-point discrimination?

A

a measure of spatial resolution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Mechanoreceptors

What works best with two point discrimination and why

A

Fingertips work best because
1. much higher density of mechanoreceptors
2. enriched in receptors types (merkel’s disks) that have small receptive fields
3. More brain tissue is devoted to each square mm of the fingertip
4. special neural mechanisms devoted to high resolution discrimination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

primary afferent axons

What are primary afferent axons?

A
  • Axons that bring info from somatic sensory receptors to spinal cord or brain stem.
  • Enters the spinal cord through the dorsal roots (cellbodies lie in DRG)
  • has widely varying diameters
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

primary afferent axons

Give axon diameter characteristics

A
  • Axon diameter: Determinant of conduction velocity
  • C fibers have smallest diameter and are unmyelinated.
  • mediate temp, throbbing, pain & itch
  • AB axons are larger
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Segmental Organization of Spinal Cord

What are the four divisions

A
  • Cervical Cord
  • Thoracic Cord
  • Lumbar Cord
  • Sacral Cord
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Segmental Organization of Spinal Cord

What is dermatome

A

Area of skin innervated by the right and left dorsal roots of a spinal segment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Segmental Organization of Spinal Cord

What are the divisions of spinal gray matter?

A

Dorsal Horn, Intermediate Zone, Ventral horn

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Segmental Organization of Spinal Cord

How do AB axons from cutaneous mechanoreceptors enter the dorsal horn?

A
  • one branch synapses in dorsal horn on 2nd order neurons
  • Initiate or modify reflexes
  • Other branch ascends straight to the brain ipsilateral to stimulus
  • responsible for perception
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Touch Pathways

Describe the Dorsal Column - Medial Lemniscal Pathway

A

This pathway mediates tactile sensation, vibration, and proprioception
1. AB axons enter and ascend via ipsilateral dorsal column
- Axons terminate in dorsal column nuclei in medulla
2. Axons from dorsal column** crosses over and ascend via the medical lemniscus.**
- Medial Lemniscus axons synapse in ventral posterior nucleus thalamus
- VPN neurons send axons to primary somatosensory cortex (S1)

17
Q

Segmental Organization of Spinal Cord

Describe the Trigeminal Touch Pathway

A
  • Somatosensory information from face is supplied by the trigeminal nerve (CNV)
  • Innervates the face, mouth, some of tongue, and dura
  • Three branches include: Ophthalmic (V1), Maxillary (V2) & Mandibular (V3)
  • Enters brainstem at the pons
  • Crosses over and sends projections to medial VPN thalamus
  • VPN sends info to** S1**
18
Q

Segmental Organization of Spinal Cord

What are the characteristics of the Somatosensory cortex or S1?

A
  • Somatosensory cortex located in the parietal lobe
  • 3B is the primary SMC because it recieves input from the VPN of thalamus, responsive to somatosensory stimuli, lesions impair somatic sensations, stimulation evokes somatic sensory experiences
  • Laminar structure
  • Layer IV recieves thalamic input
  • S1 neurons with similar inputs are stacked vertically into columns.
19
Q

Somatic mapping

What are Phantom Limbs?

A

People still have the sensation that limb is there even if it’s been removed or cut off

20
Q

Somatic mapping

What is somatotopy?

A

Mapping of the body’s surface sensations onto a structure in the brain

21
Q

Somatic mapping

Describe Somatotopic Map Plasticity

A

Example: Cortex devoted to removed finger now responded to stiumulation of adjacent digits
Missing digit caused** reorganization**

22
Q

Somatic mapping

Posterior Parietal Cortex

A
  • BA 5 & 7
  • Invovled in somatic sensation, visual stimuli, movement planning, attentiveness
  • Damage to posterior parietal areas causes interesting neurological disorders.
23
Q

Somatic mapping

What are some diseases that can be caused by damage to the Posterior Parietal Cortex?

A
  • Agnosia: inability to recognize object even though simple sensation is normal
  • Astereognosia: Normal sense of touch but lack the ability to identify objects by feeling them.
  • Neglect Syndrome: A part of body or visual field is ignored or its existence is denied
24
Q

Pain & Itch pathways

Describe the Spinothalamic Pathway

A

Pain, itch, & temp info is conveyed from spinal cord to brain
1. Axons of these 2nd order neurons decussate in the spinal cord and ascend by the spinalthalamic tract.
2. Fibers from this tract ascend to the thalamus without synapsing.

25
Q

Pain & Itch pathways

Describe the Trigeminal Pain Pathway

A
  1. Small diameter fibers from trigeminal nerve synapse onto 2 order neurons in trigeminal nucleaus
  2. Axons decussate and ascend to thalamus via trigeminal lemniscus.
26
Q

Pain & Itch pathways

What is Trigeminal Neuralgia?

A
  • Suicide Disease
  • Caused by blood vessel pressing on trigeminal nerve and this causing damage to the myelin sheath
27
Q

Pain regulation

Why when we rub a boo-boo, the pain decreases?

A

Pain regulation.
* Pain projection neuron is inhibited by an interneuron
* interneuron is then excited by the large sensory axon (AB) and inhibited by the pain axon (c-fiber)
* Activity in the pain axon alone maximally excites the pain projection neuron, pain signals go to the brain
* If the mechanoreceptor axon signlas simultaneously, the interneuron is activity and pain signal is suppressed.

28
Q

Pain regulation

What do opioid drugs do?

A
  • They reduce pain without producing producing unconsciousness
  • Can lead to coma and death at high doses
  • produces a sense of euphoria
29
Q

Pain regulation

Where does opiods come from?

A
  • Opium is an extract from poppy plant
    Opiate refers to natural
    Opioid is includes synthetic and semi-synthetic.
30
Q

Temperature

What are thermoreceptors and describe their characteristics

A
  • Neurons sensitive to temperature
  • Several TRP channels in thermoreceptors that has different sensitivities to temp.
  • Each thermoreceptive neuron expresses a single type of channel
31
Q

Temperature

What kinds of temp corresponds to what kind of sensory axons?

A
  • Cold receptors are coupled to a-delta and
  • Warm receptors are coupled to C fibers.
32
Q

Temperature

What is the difference between the response rates of warm and cold receptors?

A
  • Warm and cold recepors are greatest during and shortly after a temp change.
  • Cold recetors fires more APs when temp drops
  • Warm receptors fires less APs when temp drops.
33
Q

Temperature

What axons are cold and hot receptors coupled to?

A
  • Cold receptors coupled to A - delta and C fibers
  • Hot receptors coupled to C fibers
34
Q

Summing it all up

What is the main different between touch and pain/temp/itch pathways?

A
  • Touch ascends ipsilaterally until the media
  • Pain ascends contralaterally from the level of the spinal cord
35
Q

Summing it all up

How do the touch and pain/temp/itch pathways differ in nerve endings?

A

Touch: encapsulated structures
Pain: free nerve endings

36
Q

Summing it all up

How do the touch and pain/temp/itch pathways differ in diameter of axons?

A

Touch: larger diameter, myelinated
Pain: thin diameter, lighty myelinated & unmyelinated

37
Q

Summing it all up

How do the touch and pain/temp/itch pathways differ in connections in spinal cord?

A

Touch: Ascends ipsilaterally (crosses in medial lemniscus in medulla)
Pain: Ascends contralaterally (crosses at spinal cord level)

Neuroscience 🧠 (14 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions