Somatic Sensation Flashcards
For a free nerve ending:
What is the Primary Sensory
What is the Secondary Sensory
What does the Synapse have…
And what is its adaptation?
For Meissner’s Corpuscles:
What is the Primary Sensory
What is the Secondary Sensory
What does the Synapse have…
And what is its adaptation?
For Pacinian Corpuscles:
What is the Primary Sensory
What is the Secondary Sensory
What does the Synapse have…
And what is its adaptation?
For Ruffini Corpuscle:
What is the Primary Sensory
What is the Secondary Sensory
What does the Synapse have…
And what is its adaptation?
For Merkel receptors:
What is the Primary Sensory
What is the Secondary Sensory
What does the Synapse have…
And what is its adaptation?
What do all these skin sensory receptors feel for?
Define noxious stimuli.
Stimulus, which is left in contact with the tissue will cause damage.
What’s the speed of light vs speed of conduction of neurons for us?
Light: 3x10^8
Conduction(us): 1x10^2. Waaaay slower :(.
When are cold receptors activated?
When the temperature is lower than body temperature.
There are two types of warm receptors, what are the conditions for each to activate?
- Literal warm receptors: Above body temperature to about 45°C. (113°F)
- Pain receptors activated above 45°C.(113°F)
What type of channel do all thermoreceptors use?
Cation channels called transient receptor potential channels. Or TRP Channels.
For (Somatosensory) Alpha-beta Nerve fibers:
What are the Fiber Characteristics.
What is the speed of conduction.
What stimuli is it associated with?
They are Large, and Myelinated
30-70 m/sec
Mechanical Stimuli
For (Somatosensory) Alpha-delta Nerve fibers:
What are the Fiber Characteristics.
What is the speed of conduction.
What stimuli is it associated with?
Small, myelinated
12-30 m/sec
Cold, fast pain, mechanical stimuli.
For (Somatosensory) C Nerve fibers:
What are the Fiber Characteristics.
What is the speed of conduction.
What stimuli is it associated with?
Small, unmyelinated
0.5-2 m/sec
Slow pain, heat, cold, mechanical stimuli
For (Somatosensory) Alpha-alpha Nerve fibers:
What are the Fiber Characteristics.
What is the speed of conduction.
What stimuli is it associated with?
Large, myelinated
80-120 m/sec
Proprioception: sense of self/sense of position of limbs.
Explain what sensory neurons dictate how precise we can feel the sense.
It is based on how many primary sensory neurons go to a singular secondary sensory neuron.
The more primary sensory neurons that go to a singular secondary sensory neuron the less specific the receptive field is and vice versa .
Primary neuron response is _________ to stimulus strength.
Proportional
When the primary neuron stimulates the secondary neuron, the secondary neuron then inhibits surrounding neighboring secondary neurons, why?
The inhibition of lateral neurons, enhances perception of the stimulus to give a more precise location of original stimulus.
What are the four types of somatic sensation?
Touch, proprioception, temperature, nociception(pain and itch).
Where do the pathways for somatic perception project to in the brain?
To the cortex and cerebellum.
Where are the receptors located for somatic senses?
Skin and viscera.
Where do primary sensory neurons synapse? (Connect to other neuron, which one and where?)
Synapse in CNS with secondary sensory neurons.
Where do secondary sensory neurons synapse? (Connect to other neuron, which one and where?)
Interneruons in the CNS - synapse with tertiary sensory neurons in the thalamus
Where do tertiary sensory neurons synapse? (Connect to other neuron, which one and where?)
Project to Somatosensory cortex and many project to the cerebellum Somatosensory cortex.
Fill in the blanks
There are two distinct somatosensory pathways.
(1) One for fine touch, proprioception, and vibration. (2) The other for Nociception, temperature, and coarse touch. What are the difference in these two pathways? What’s the same?
(1): primary sensory neuron synapses in the medulla
(2): primary sensory neuron synapses in dorsal horn of spinal cord.
(1): secondary sensory neuron crosses, midline of body in medulla.
(2): secondary sensory neuron crosses midline of body in spinal cord.
Other two are the same.
What is the most defining characteristic of nociceptor?
What does it respond to?
Where is it found?
Where are they not found?
When is it activated?
Where do they integrate(connect to secondary neuron)
What are the two types of primary sensory fibers?
Most defining: neurons with free nerve endings
Responds to noxious stimulus
Found everywhere, skin, joints, muscles, bones, viscera.
NOT found in CNS.
Activated as a reflex protective response .
Alpha-delta fibers and C fibers.
Why do we and why can we have brain surgeries with the patient fully awake?
There are no pain receptors in the brain!
Explain how pain is a subjective perception.
Humans learn to what a given stimulus is. Meaning it’s a judgment that you make based on the nature of the action potentials that are coming into your brain.
Ex. Think about how newborns have such a delayed response to pain. They are learning what pain feels like and how to respond to it, and why they don’t cry right away .
Think about the trend where parents would knock on a wooden door and then pretend the baby was hurt and then the baby would start crying. It is learned to some degree, ALL BASED ON ACTION POTENTIALS TO THE BRAIN.
What differentiates fast pain from slow brain to us?
Fast pain is described as sharp and localized. Produced by Alpha-delta fibers.
Slow pain is described as dull and more diffuse .
Produced by C fiber .
What is the leading theory on why these voltages are so different and our preception of them is so different?
Because of the difference in conduction velocity.
Explain how we feel itching after an injury? Why is it referred to as a reverberating loop?
From the same skin nociceptors that transmit the Afferent message of pain, also release neurotransmitters substance P (attract Mast cells and neutrophils) and CGRP(go into blood vessels).
The neutrophil’s released histamine
This histamine, as well as other substances activate the C fibers. Continuing the dull pain which is often referred to as itching.
So in summary when pain receptors are activated, they release signals that attract other cells that secrete signals that continue to signal the pain receptors.
Define inflammatory pain
Increase sensitivity to pain at sites of injury
What are the five common local chemicals that mediate inflammatory response at site of injury?
K+, histamine, prostaglandins, serotonin, substance P
Where do reflexive protective responses integrate?
At the level of the spinal cord.
Define what the withdrawal reflex is.
Protective reflex response to pain.
Define what referred pain is.
Poorly localized pain perceptions from visceral and somatic pain pathways converging on a single ascending track.
Often sensed on the surface of the body when in fact, the pain is in an internal organ.
Ex. Someone’s first Heart attack.
What is the leading theory on why humans have referred pain?
We believe that Certain pathways, share common, secondary, and tertiary neurons to the spinal cord or in the medulla. Making it hard for the brain to distinguish the different perceptions of pain. Particularly when you’re unfamiliar with the stimulus.
Humans will learn what this pain feels like for example, after the first heart attack the second one you will know it’s a heart attack and shoulder pain .
Why is it very harmful if you experience pain for too long?
Because overtime there will be permanent changes in the wiring of your neurons.
Making any sensation to that area, painful even when it’s not actually damaging any tissue .
Define gate control theory
Define Analgesic drugs, and name two common drugs under this category.
A class of drugs that treat pain and can also reduce fever and inflammation.
Aspirin
Opioids
Explain how Aspirin works
Inhibits prostaglandins, decreases inflammation, and slows transmission of pain to site of injury.
Explain how opioids work. (Hint: two kinds)
Exogenous opioids bind opioid receptors.
Endogenous opioids include endorphins(beta-endorphin), enkephalins, dynorphins.
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