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Physio 2 > 2-NSc-Handout-F14 > Flashcards

2-NSc-Handout-F14 Flashcards

1
Q

somato-sensory system

A
  1. principles
  2. pain
  3. proprioception
  4. touch
  5. temperature
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2
Q

special senses

A
  1. vision
  2. hearing
  3. balance
  4. taste
  5. smell
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3
Q

nervous system

A

governs actions and reactions involving 3 basic functions

  1. detection of a stimulus and transmission to CNS via afferent neurons (sensory)
  2. processing info and decision making - interneurons (association neurons)
  3. transmission of response via effector or efferent neurons (motor)
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4
Q

THE SOMATO-SENSORY SYSTEM

A

… is comprised of peripheral sensory receptors, ascending tracts and central processing centers to produce 4 sensory modalities:
TOUCH, PROPRIOCEPTION, PAIN and TEMPERATURE.

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5
Q

the somato-sensory concept??

A 
specific stimulus in a BODY part (e.g. pain)triggers an electrical change or graded potential in its specific receptor = receptor STIMULATION TRANSDUCTION of signal into action potentialsTRANSMISSION via ascending neurons/tracts to a designated brain
area within the Somato-
Sensory CORTEXallows correct
interpretation and localization of
the stimulus = Conscious PERCEPTION
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6
Q

RECEPTOR STIMULATION & TRANSDUCTION

A

Stimulation leads to changes in ionic channels, which alter ionic flow, typically leading to depolarisation of the receptor membrane = Graded Potential
–> stimulating energy is transformed into electric energy = TRANSDUCTION

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7
Q

THe somato-sensory cortex –> cerebral cortex is responsible for?

A

the conscious experience of the incoming stimulus = Perception
(also for conscious movement and cognitive skills)

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8
Q

The (somato-) sensory projection neurons (3rd order neurons) end in designated locations of the cortex –>

A

each area is dedicated to the perception of one sense = CORTICAL MAP

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9
Q

Important body areas are disproportionately represented because they contain more sensory receptors; depends on a species’ life style —>

A

SomatoSensory Map or “Humunculus”

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10
Q

adaptation

A

An organism has to primarily react to changes in the environment –> many receptors react only to initial change in stimulus strength and then adapt to it

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11
Q

RAPID Adaptation = Phasic receptors

A

Sensory receptors adapt within seconds or milliseconds

–> geared towards registering quick changes in stimulus strength, e.g. touch, smell, thermoreception

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12
Q

SLOW Adaptation = Tonic receptors

A

Sensory receptors continue to transmit impulses as long as stimulus exists,
and frequency decreases only slightly
–> keep CNS apprised of status of the body, e.g. proprioception, baroreceptors, chemical composition of blood

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13
Q

Pain

A

is an unpleasant sensory and emotional experience associated with actual or potential tissue damage

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14
Q

purpose of pain

A

Part of the body’s protection mechanism to withdraw from damage, to protect from further damage during healing and to avoid damage in the future

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15
Q

Nociception sensory receptors

A

transduce a noxious stimulus = process of NOCICEPTION, and transmit stimuli via 2. / 3. order neurons to the brain for CONSCIOUS PERCEPTION = PAIN.
Nociceptors also transmit stimuli to LMNs to initiate withdrawal reflexes (without conscious perception of pain

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16
Q

Nociception are?

A

Pain Neurons with free nerve endings

  • are present in all tissues except the brain
  • are more numerous in the skin (somatic superficial pain) than in deeper tissues like muscles and joints (somatic deep pain) or in organs (visceral pain)
  • as first-order neurons, pain fibers run in peripheral nerves to the spinal cord/dorsal horn, respectively via Cranial Nerves (V, VII, IX, X) to the brain stem
17
Q

NOCICEPTOR ACTIVATION

A
  • are triggered by high threshold chemical/mechanical/thermal energytissue disruption
  • are poly-modal chemoreceptors = carry several types of receptors / transduction channels
18
Q

Common noxious stimuli include

A 
ATP Nerve Growth Factor 
H+ Intense heat / cold 
K+ Intense pressure
Lipids Prostaglandins !! 
Bradykinin Histamine 
Serotonin Substance P(ain) 
Leukotriens Endothelin
19
Q
  1. Pain (“generation of pain”)
A

Painful impulse is triggered by initial mechanical force
of injury –> damaged cells release many chemicals –> activate nociceptors –> transduction & transmission via small myelinated A-delta fibers –> perceived as sharp / immediate / stinging / bright / localized pain = First Pain

20
Q
  1. Pain (“maintenance of pain”)
A

Activated nociceptors release additional chemicals, i.p. Substance P and Calcitonin- Gene-Related Peptide (CGRP); both:

–> Cause more pain, and
–> stimulate release / production of inflammatory
mediators from tissue macrophages & WBCs, e.g. histamine, prostaglandins, bradykinin, cytokines aka the “Inflammatory Soup”
The “Inflammatory Soup” activates nociceptors and maintains a burning / diffuse / nagging / throbbing / nauseating / long-lasting pain sensation via un- myelinated C fibers = Second Pain

21
Q

SENSITIZATION to Pain (=“enhancing pain”)

A

The Inflammatory Soup, i.p. prostaglandins, can lead to temporary changes in transduction channels:
- achieved via phosphorylation of channel proteins –> widening of channels, extended opening of channels
- via gene expression –> insertion of new channels and receptors
Both facilitate ionic flow & amplification of signal transmission = nociceptors become more sensitive to stimuli (increases protection of the affected area).

22
Q

Two forms of sensitization:

A
  1. HYPERALGESIA
    an exaggerated pain response to a noxious stimulus
  2. ALLODYNIA
    a pain response to a non-noxious stimulus, e.g. a gentle touch
23
Q

When does sensitization typically resolve?

A

as the injury heals. If it persists in the absence of injury –> chronic pain

24
Q

PAIN TRANSMISSION & ASCENDING PATHWAYS

A

Nociceptive afferent fibers (A delta and C fibers) enter spinal cord
via dorsal root –> dorsal horn –> synapse with 2.order neurons, using excitatory Neurotransmitters, e.g. Substance P, Glutamate –>
axons enter the SPINOTHALAMIC TRACT (STT) in the Lateral Funiculus: - always contralateral in primates
- ipsi- and contralateral in domestic animals

25
Q

The STT projects to various brain regions:

A
  1. to Somatosensory Cortex via Thalamus (relay) for acute perception and localization of pain = discriminative pain pathway; receives input mostly from A delta fibers; aka Neo-STT = a “new” evolutionary tract
  2. to Reticular Formation and Limbic System; receives input mostly from C fibers; aka Paleo-STT
    >evokes dull, aching, burning, diffuse pain
    >evokes autonomic responses, e.g pulse, blood pressure, sweat
    >evokes emotional & behavioral responses, e.g. fear & avoidance
    >maintains arousal / wakefulness
26
Q

Pain is also carried in many other tracts….

A

in the Fasciculus proprius

27
Q

Pain can be moderated / inhibited via descending ANALGESIA Pathways:

A
  • originate in the cortex, thalamus and brain stem and descend in the lateral funiculus
  • are activated by incoming pain (also by high sympathetic tone/ excitement / danger)
  • form multiple synapses with ascending pain neurons and end on inhibitory interneurons in the dorsal horns
  • interneurons use a variety of inhibitory neurotransmitters where they synapse with incoming pain fibers to block transmission of pain signals (from 1. to 2. order pain neurons), i.p. the ENDOGENOUS OPIOIDS Enkephalins, Endorphins, and Dynorphins; also GABA, Glycine
  • Endorphins are also released into blood by hypothalamus
28
Q

chronic pain

A
  • aka Pathological Pain or ‘Bad Pain” ( vs acute, physiological or good pain)
  • serves no physiological purpose & persists IN THE ABSENCE OF TISSUE INJURY
  • is characterized by hypersensitivity of the pain transmission system
    = Hyperalgesia and Allodynia (see2.2.4), which can last months or years
29
Q

Underlying mechanism (of “neuroplasticity”)

A

Strong stimulationaltered signaling pathways (e.g. phosphorylation) and altered gene expression of c-fos, transcription factors, kinases –> induce neuron-remodeling with profound changes in receptors, channels, neurotransmitter production & release, cellular proliferation –> amplification of pain signals; two forms:

  1. Peripheral Sensitization: Nociceptor re-modeling as discussed (2.2.4); induced by inflammatory mediators
  2. Central Sensitization: aka ‘Wind-Up”; hyper-excitability of neurons within the CNS upon strong stimulation; triggered by bursts of nociceptor activity, e.g. during surgical incisions
30
Q

The key to preventing chronic pain?

A

is preemptive analgesia

31
Q

Unmanaged pain / chronic pain can be debilitating, causing multiple stress responses, such as

A
  • reduced food/water intake
  • reduced healing / prolonged recovery times - impaired immune system function
  • cardio-respiratory effects (high blood
    pressure, tachycardia, tachypnoe) - renal effects (reduced GFR, salt
    & water retention)
32
Q

“Is the animal in pain?”

A

Observation of behavior, expression, responsiveness, vital signs;
Pain expression differs greatly depending on species with prey animals typically showing less obvious signs

33
Q

“Can the animal feel pain?” (neurological examination)

A
  • skin prick for detection of superficial pain sensation (runs largely in the
    Spinothalamic tracts)
  • pinching digits / joints strongly with fingers or hemostat for detection of deep pain
    (runs in deeper tracts, e.g. Fasciculus Proprius)
34
Q

Because of different neurotransmitter (NT) pattern in different pain pathways with a wide variety of …

A

excitatory and inhibitory NTs, multimodal analgesia is used to combat most / all pain transmission

> CNS, via descending analgesia system, affecting pre- and/or post-synaptic transmission:
- Opiods
- Alpha 2 agonists
- Serotonin (via re-uptake inhibitors) - Paracetamol ?
Axon Transmission
local anesthetics (block Na-voltage gated channels)
Nociception
NSAIDs, e.g. ibuprofen, salicylic acid
via inhibition of Prostaglandin production

35
Q

Proprioception: Sense of Body Position and Movement

A

> Gives continuous and detailed information about positions of limbs relative to the body and their rate of movement
Is essential for accurate, coordinated, purposeful movements and gait
Receptors constantly monitor:
- muscle length / tension via muscle spindles - tendon length / tension via tendon organs
- joint angulation / rotation via joint receptors
stimuli ascend via spinal cord to cerebellum (unconscious proprioception) and cerebral cortex (conscious proprioception)
loss of unconscious a/o conscious sense of proprioception will lead to incoordinated movements = ATAXIA

Note: full sense of orientation in space also requires the sense of equilibrium = special sense (= head position relative to ground)

Physio 2 (2 decks)

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