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Anatomy (Pharm 110) > 7.1 Peripheral nervous system > Flashcards

7.1 Peripheral nervous system Flashcards

1
Q

explain division of the PNS -> what are the two main divisions?

A
  • two main divsions= sensory (afferent) and motor (efferent)
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2
Q

describe sensory recpetors

A
  • specialized to respond to changes in their environment
  • Receptors have specificity for stimulus energy (ex retina can only pick up light, cant feel light)
  • stimulus must be appleid in a recpetive field
  • transduction occurs:
  • > stimulus energy is converted into a graded potential
  • > must reach threshold for nerve impulse
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3
Q

how are sensory receptors classified?

A
  1. Functionally by type of stimulus detected
  2. Location of stimulus
  3. Structural complexity
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4
Q

what are the subcategories of the functionality by type of stimulus detected

A
  1. Nociceptors: pain receptos
    • myelinated type A fibers: carry sensations of fast pain
    • unmyelinated type C fibers: carry sensations of slow pain
  2. Thermoreceptors: temerapture receptors
  3. Chemoreceptors: respond to water soluble and lipid soluble substances dissolved in body fluids
  4. Mechanoreceptors: sensitive to stimuli that distory plasma membranes (mechanicaly gated ion channels)
    • proprioceptors: monitor position of joint and muscles
    • Baroreceptors: detect pressue changes
    • Tactile receptors: provide sensations of touch, pressure and vibration
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5
Q

what are the subcategories under location of stimulus

A
  1. Exteroceptors
  2. Interoceptors (visceroceptors)
  3. proprioceptors
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6
Q

describe exteroceptors

A

* receptor classification describe by location of stimulus

  • Respond to stimuli arising outside body
  • Receptors in skin (touch, pressure, pain, & temperature) & most special sense organs
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7
Q

describe interoceptors

A

*receptor type describred by location of stimulus

aka viscerocepors

*stim inside the body

  • Respond to stimuli arising in internal viscera & blood vessels
  • Sensitive to chemical changes, tissue stretch, & temperature changes
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8
Q

descirbe proprioceptors

A

receptor type describred by location of stimulus

  • Respond to stretch in skeletal muscles, tendons, joints, ligaments, & connective tissue coverings of bones & muscles
  • Inform brain of one’s movements
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9
Q

what are the subcategories under the calssification by strutural complexity

A
  • classified as unencapsulated nerve endings vs encapsulated nerve endings
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10
Q

Describe unencapsulated nerve endings

A
  • subcategory within the receptor classification by structural complexity
  • Not protected by accessory structures

Present throughout body (abundant in epithelial & connective tissue)

  • Mainly group C-fibers (slow)
    include: hair follice receptors, free nerve endsings and merkel discs
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11
Q

describe encapsulated enrve fibers

A
  • subcategory within the receptor classification by structural complexity
  • all are mechanoreceptors
  • enclosed by connective tissue capsule
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12
Q

describe hair follice receptors

A

*uncapsulated dendritic endings (classified by structural complexity)

Mechanoreceptors wrapped around hair; activated by deflection of hair

-Rapidly adapting

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13
Q

describe free nerve endings

A

*uncapsulated dendritic endings (classified by structural complexity)

  • thermoreceptors: Cold receptors (10-40 Csuperficial; Heat receptors (32-48 C) deeper
  • mechanoreceptors: pressure
    chemoreceptors: itch (histamine), pH
  • Nociceptors: pinching, chemicals frmo damages tissue, extreme temps, capsaicin (spicy)
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14
Q

describe merkel discs

A

*uncapsulated dendritic endings (classified by structural complexity)

* in deepest skin epithelial layer

  • Mechanoreceptor for light steady pressure
  • Tactile cell in basal layer of epidermis
  • Slowly adapting

*can also esist as capsulated

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15
Q

can are the types of encapsulated dendritic endings?

A
  • Meissners corpuscles:
    • ​light pressure, discriminative touch, low freq vibrations
    • dermal papillae of hairless skin
  • Pacinian corpsulces
    • deep pressure, stretch, high freq vibration
    • dermis and hypodermis
    • big onions
  • Ruffini endings:
    • deep continuous pressure and stretch
    • dermis, hypodermis, joint capsule
  • Markel discs
    • mechanoreceptor for light steady pressue
    • basal layer of dermid
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16
Q

what encapsulated dendritic endsings are fast adapting vs slow adapting?

which are superfiical vs deep?

A

Meissner corpuscles: superfiical and fast adapting

Merkel cells: superficial and slow adapting

Pacinian corpuscles: Deep and fast adapting

Ruffini endings: deep and slow adapting

*fast adapting gives tingling and vibratory sensations

*slow adapting gives snesations of steady pressure

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17
Q

muscle spindles, (golgi)tendon organs and joint kinestheric recptoers have ____ dendritic endings

A

ecapsulated dendritic endings

muscle spindles: do muscle stretch and skeletal uscle perimysium

Golgi tendon organs: strench in tnedond

Joint kinestheic receptors: stretch in articular capsules

18
Q

sensation vs preception

A

sensation: awareness of changes in internal & external environment

Perception: conscious interpretation of stimule (how we choose to respond)

19
Q

what are the 3 basal levels of neural integration in sensory systems

A
  1. receptor level: sensory reception and transmission to CNS
  2. Circuit level: processing in ascening pathways
  3. Perceptual level; processing in cortical sensory centers

*input comes in from receptors and is processed (moves thru NS) as it is relayed towards the brain

20
Q

Describe the criteria required for generation of a signal for processing at the receptor level

A
  • for sensation to occur, stimulus must excit receptor, and AP must reach CNS
  • stimulus energy must beapplied within receptive field
  • transduction must occur: energy of stimulus is converted into graded potential
  • > generator potential in general receptors
  • > receptor potential in psecial sense receptors
  • graded potentials must reach threshold -> AP
21
Q

describe adaptation for processing at receptor level

A
  • Adaptation: Change in sensitivity in presence of constant stimulus
  • > receptor memrbanes become less responsive
  • recpeotr potential decline in freq or stop
  • phasic receptors (fast adapting) send signals at beginning or end fo stimulus
    ex: receptors for pressure, touch, and smell (quickly get used to smell)
  • tonic receptors: adapt slowly or not at all (dont want fast adaption to pain)
    ex: nociceptors and most proprioceptors
22
Q

Describe processing at Cirucit level

A
  • pathway of 3 neurons conduct sensory impulses received from receptors upward t appropriate cortical regiosn
23
Q

what is processing at the perceptual level

A

interpretation of sensory input depends on specific location of target neurons in sensory cortex

24
Q

what is perceptual detection

A

* aspects of sensory perception

ability to detect stimulus (pick up that a change occured)

25
Q

what is magnitude estimation

A

aspects of sensory perception

  • intensity coded in frequency of impulses
26
Q

What is spatial discrimination

A

aspects of sensory perception

  • indentifying site or pattern of stimulus
27
Q

what is feature abstraction

A

aspects of sensory perception

*higher order processing

  • indentification of more complex aspects and several stimulus porperties
    (ex: velvet is warm, compressible and smooth but not completely continuous)
28
Q

what is quality discrimination

A

aspects of sensory perception

*higher order processing

  • ability to identify submodalities of a sensation (ex sweet vs sour taste)
29
Q

what is pattern recognitiion

A

aspects of sensory perception

*higher order processing

  • recognition of familiar or significant patterns in stimuli
30
Q

describe perception of pain

A
  • warns of actual or impending damage
  • stimuli include: extreme pressure and temp, chemicals released by tissues (histamine, K+, ATP, acids, bradykinin)
  • impulses travel onL thinly myelinated Aδ fibers -> release glutamate (fast pain)
  • unmyelinated C fibers release glutamate + substance P (pain substance, these are slow apin)
31
Q
A
32
Q

describe the gate control theory of pain modulation

A
  • non painful inputs (Aβ) inhibit pain transmission (C fibers)

*if hammer hits hand, you rub/touch it

  • > slow pain comes in and synpases on ascending neurons get a strong painful stimulus to brain
  • > have a tonically active inhibitory interneuron -> if touch/non painful stim you increase firing of the Aβ fiber and get inhibiton of the pain transmission form C fiber
  • > get less pain sensation to the brain
33
Q

Describe descending pain conrol in pain modulation

A
  • some pain impulses are blocked by inhibitory endogenous opioids (endorphins and enkephalins)
  • descening fibers from cortex and hypothalamus release inhibitory neurotransmitters that suppress pain signals

*if a lot of activation in hypothalamus in stressful situation you dont realize you are in pain bc signals are repressed

* pain suppression occurs ar periaquductal gray

34
Q

Describe homeostatic imbalance

A
  • long lasting/intense pain -> hyperalgesia (pain amplification), chronic pain and phantom limb pain

*pathways used again and again, circuit becomes stronger and more efficiency in pian transmission -> learn pain, can lead to chornic pain

  • modulated by NMDA receptors - allow spinal chord to “learn” hyperalgesia

*early pain management is critical

35
Q

What is Phantom limb pain

A
  • felt in limb no longer present
  • now use epidural anesthesia to reduce

anesthetic at spinal chrod, prevents pain transmittion during amputation

36
Q

describe visceral pain

A
  • visceral pain results from stimulation of visceral organ receptors
  • felt as vauge aching, snawing, curning (not precise, poorly localized, v general)
37
Q

describe referred pain

A
  • pain from one body region perceived as coming from a different region

(bdoy misinterprets the source)

38
Q

describe the regeneration of nerve fibers

A
  • mature neurons are amitotic
  • if soma of damaged nerve is intact, axon can regenerate

*if damage body of nerve it cant regenerate

  • involves coordinated activity between: macrophages, schwann cells and axons
39
Q

why cant nerve fibers in the CNS be regenerated?

A

CNS oligodendrocytes bear growth-inhibiting proteins & astrocytes form scar tissue that prevent CNS fiber regeneration

40
Q

describe the process of axon regeneration to damaged nerve cell

A

* only in PNS
1. axon becomes fragmented at injury site

  1. Macrophages clean out dead axon distal to injury
  2. axon sprouts (of filaments) grow through regeneration tube formed by Schwann cells
  3. Axon regenerats & a new myelin sheath forms
41
Q

how are peripheral nerves classifed

A

cranial (comes off brain) or spinal (off spine)

*msot nerves are mis of afferent and efferent somatic and autonomic visceral fibers

42
Q
A

Anatomy (Pharm 110) (41 decks)

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