Block 2 Exam: Somatosensory Information Flashcards
Describe Mechanoreception in organs.
- artery distension.
- stretch in digestive organs
- bladder
Pacinian Corpusles
Rapidly Adapting (large receptive fields) Deep in skin
Functions: VIBRATION through mechanically gated ion channels. Also signals dynamic CHANGES
Meissner’s Corpusles
Rapidly Adapting
Superficial (shallow) layers of skin
Functions: Stroking, fine movements, grip control, where 2 point discrimination is best developed
Ruffini Endings
Slowly Adapting (enlarged nerve endings) Deep in skin
Signal presence of Stretch or tension.
Merkel’s Disks
Slowly adapting (enlarged nerve endings) Shallow in skin
Steady pressure on skin. Also texture and edges. Fire AP which stimulus present to keep TRP channels going. Directly related to pressure intensity
A-alpha fibers
PROPRIOCEPTORS of skeletal muscle: where your body is in space.
Intrafusial fibers
A-beta fibers
General Touch/MECHANORECEPTORS
Hair follicle, Meissner Corpusle, Merkel
Adelta/C fibers
Free nerve endings
Though pain heat and itch are slower, reflex mechanisms will let you withdraw.
Outer layer of skin=
Inner layer of skin=
Epidermis
Dermis
A-delta are ____ nociceptors, whereas C are ____ nociceptors.
Mechanical
Polymodal
Spinal Lesions in Cervical areas could cause dermatomes…
Neck, upper back, arms and hands
Spinal Lesions in Thoracic areas could cause dermatomes…
Middle back, breast/chest and stomach, small part of arm
Spinal Lesions in Lumbar areas could cause dermatomes…
Lower back, front legs down to toes
Spinal Lesions on Sacral areas could cause dermatomes…
Genitalia/buttocks, back of legs down to outer foot.
Homunculus
The idea that in the somatosensory cortex, places with more fine sensory info (ex: hands) take up more room.
2-point Discrimination
Why discriminate points closure on fingers than lower back. Within back, few receptors in large receptive fields.
3 Factors
- Higher density of mechanoreceptors
- Small receptive fields
- More cortical tissue devoted to finer areas.
That fact that surrounding areas invade cortical areas that lose innervation is known as
Cortical Map Plasticity
Proprioception is on the _____ side and has info go through Dorsal _____.
Ipsilateral
Dorsal Columns
Nociception (pain) is on the _____ side and has info go through Dorsal ____.
Contralateral
Dorsal Horn
Proprioception:
Upper (thoracic/cervical)–>
Lower (sacral/Lumbar)–>
Upper (thoracic/cervical)–> Lateral (cuneate Fasiscle)
Lower (sacral/Lumbar)–> Medial (gracile fascicle)
Pain:
Upper (thoracic/cervical)–>
Lower (sacral/Lumbar)–>
Upper (thoracic/cervical)–> Medial (gracile Fascicle)
Lower (sacral/Lumbar)–> Lateral (cuneate Fascicle)
Review of Dorsal Column Medial Lemniscal Pathway:
Primary neurons –> Secondary neurons in dorsal column nuclei –> Crosses at medial leminsus –> VPL of thalamus –> Somatosensory cortex (postcentral gyrus/posterior paracenteral gyrus)
Name the four types of nociception
Pain=
- Mechanical-strong pressure (crude touch)
- Thermal- extreme temperature
- Chemical- histamines/chemicals
- Polymodal
Pain=tissue damage
After injury, pain receptors exhibit increased sensitivity after injury. They have a lower threshold and are more responsive (AP). What is this called?
Hyperalgesia
Perception of innocuous (non-harmful) stimuli as painful after tissue damage is known as ______
Allodynia
What is that thing that happens to blood vessels when painful stimuli is present?
Vasodilation
Pain medications can block _____
Prostaglandins
Thalamic Lesioning (CM-PF) and deep brain stimulation are often used as treatments for what?
Intractable pain
What 4 things contribute to noxious signal?
Bradykinin
K+
Prostaglandins
Histamine (also promotes swelling)
2 functions of substance P
Release Histamine from mass cells.
Vasodilation of blood vessels.
Reticular thalamic system is
Reticular nucleus –> intralaminar nucleus of thalamus. (centromedian/parafascicular).
Underlie altering mechanisms to painful stimuli.
Dorsal Horn Layers:
Posterior Marginal Area
Upper layer 1
Receives noxious stimuli from A-delta fibers
Dorsal Horn Layers: Substantia Gelatnos
Layer 2
innocuous, so info non-painful carried in C fibers
Dorsal Horn Layers: Nucelus Proprious
Layers 3 and 4
innocuous, so info non-painful in C fibers
Dorsal Horn Layers:
Lower Lamina
Layers 5 and 6
noxious stimuli form A-delta fibers
Most layers in dorsal horn project to ____, and upper layers project to other spinal cord areas to mediate ____ actions.
Thalamus
Reflective actions
What layers of dorsal horn project to reticular system in brainstem?
What is the reticular system important for?
Layers 1 and 5
Altering attention.
What does the reticular thalamic pathway tell us?
When we are in pain.
Descending control of pain/feedback is mediated by emotional and behavioral state using what 5 brain areas?
- Somatosensory cortex
- Insula/anterior cingulate
- Periventricular Nucleus
- Periaqueductal Gray
- Raphe Nuclei
Stimulation of ____ causes analgesia, or the inability to feel pain.
Periaqueductal gray
Insula is in lateral fissure and is important for taste. Why does that matter in pain modulation?
Reward/motivation behavior
Periaqueductal Gray has a lot of ___ receptors.
opioid
____ is in lower brainstem, is important for serotonin, and projects to dorsal horn to modulate pain.
Raphe nuclei