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PHARM 110 > 9 - Peripheral Nervous System > Flashcards

9 - Peripheral Nervous System Flashcards

1
Q

What are Sensory receptors?

A
  • Specialized to respond to changes in their envmt
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2
Q

How are Sensory recpetors classified

A
  • Functionally by type of stimulus detected
  • Location of stimulus
  • Structural complexity
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3
Q

What are Nociceptors

A
  • pain receptors
  • myelinated type A - fast pain
  • unmyelinated type C - slow pain
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4
Q

What are Thermoreceptors

A
  • temperature receptors
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5
Q

What are chemoreceptors

A
  • respond to water-soluble & lipid-soluble substances dissolved in body fluids
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6
Q

What are Mechanoreceptors?

A
  • sensitive to stimuli that distort their plasma membranes
  • proprioceptors - position of joints & muscles
  • Baroreceptors - pressure changes
  • tactile receptors - touch, pressure & vibration
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7
Q

How are Sensory receptors classified by Location of stimulus?

A
  • Exteroceptors - stimuli arising outside body
  • Interoceptors (visceroceptors) - stimuli arising in internal viscera & blood vessels
  • Proprioceptors - stretch in skeletal muscles, tendons, joints, ligaments & connective tissue coverings of bones & muscles
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8
Q

How are Sensory recpetors classified by structural complexity

A
  • Unencapsulated nerve endings:
    ○ Not protected by accessory structures
    ○ Present throughout body
    ○ Mainly Group C fibers
  • Encapsulated nerve endings:
    ○ All are mechanoreceptors
    ○ Enclosed by connective tissue capsule
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9
Q

What are examples of Unencapsulated Nerve endings

A
  • hair follicle receptors
  • merkel discs
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10
Q

What are examples of Encapsulated Nerve endings

A
  • Messiner’s corpuscles
  • Pacinian corpuscles
  • Ruffini endings
  • Muscle spindles
  • Golgi (tendon) organs
  • Joint kinesthetic receptors
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11
Q

Sensation vs. Perception

A
  • Sensation - awareness of changes in internal & external environment
  • Perception - conscious interpretation of those stimuli
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12
Q

What are the 3 basic levels of neuronal integration in sensory systems

A
  • Receptor level > circuit level > perceptual level
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13
Q

Processing at Receptor level

A
  • Generating a signal - for sensation to occur, stimulus must excite a receptor & AP must reach CNS
  • Graded potential must reach threshold -> AP
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14
Q

What is Adaptation in Receptors

A
  • change in sensitivity in presence of constant stimulus
  • Receptor membranes become less responsive
  • Receptor potentials decline in frequency or stop
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15
Q

What are Phasic receptors

A
  • fast-adapting, send signals at beginning or end of stimulus
  • Ex. Receptors for pressure, touch & smell
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16
Q

What are Tonic receptors

A
  • adapt slowly or not at all
  • Ex. Nociceptors & most proprioceptors
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17
Q

Processing at Circuit Level

A
  • pathways of 3 neurons conduct sensory impulses from receptors to cortical regions
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18
Q

Processing at Perceptual level

A
  • Interpretation of sensory input depends on specific location of target neurons in sensory cortex
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19
Q

What is the Perception of pain

A
  • Warns of actual or impending tissue damage
  • Stimuli - Extreme pressure & temp & Chemicals release by tissues - histamines
  • Impulses travel on:
    • Thinly myelinated AS fibers release glutamate
    • Unmyelinated C fibers release glutamate + substance P
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20
Q

What is the Gate Control Theory

A
  • Non-painful inputs (AB) inhibit pain transmission (C fibers)
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21
Q

What is Descending Pain Control

A
  • Some pain impulses are blocked by inhibitory endogenous opioids (endorphins & enkephalins)
  • Descending fibers from cortex & hypothalamus release inhibitory NTs that suppress pain signals
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22
Q

Long Lasting/intense pain can lead to…

A
  • hyperalgesia (pain amplification), chronic pain & phantom limb pain
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23
Q

What is Visceral pain

A
  • Visceral pain results from stimulation of visceral organ receptors
    Felt as vague aching, gnawing, burning
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24
Q

What is referred pain?

A
  • pain from one body region perceived as coming from different region
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25
Q

What are the Steps to Nerve Fiber Regeneration

A
  1. axon becomes fragmented at injury site
  2. Macrophages clean out dead axon
  3. axon sprouts grow through regeneration tube formed by schwann cells
  4. axon regenerates & new myelin sheath forms
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26
Q

What are the 2 classifications of peripheral nerves?

A
  • cranial nerves
  • spinal nerves
27
Q

What is cranial nerve 1

name, function, pathway

A
  • Olfactory nerves
  • Sensory - olfaction
  • Olfactory receptors of nasal cavity > cribriform plates > synapse in olfactory bulbs > primary olfactory cortex
28
Q

What is CN 2

A
  • optic nerves
  • Sensory - vision
  • Retinas > optic canals > cross at optic chiasma > thalamus (LGN) > visual cortex
29
Q

What is CN 3

A
  • Motor
  • Somatic - raising eyelid (levator palpebrae superioris), directing eyeball (4 extrinsic eye muscles)
  • PSNS - sphincter pupillae & ciliary muscle
  • Exits through superior orbital fissure to various muscles around/ in eye
30
Q

What is CN 4

A
  • Trochlear nerves
  • Motor - superior oblique muscle
    Exit through superior orbital fissures
31
Q

What is CN 5

A
  • Trigeminal nerves
  • Ophthalmic (V1) - passes through superior orbital fissure
  • Maxillary (V2) - passes through foramen rotundum
  • Mandibular (V3) - passes through foramen ovale
  • V1 & V2 - sensory ONLY
  • V3 - sensory & motor
32
Q

What is CN 6

A
  • abducens nerves
  • Motor - lateral rectus muscle
  • Exit through superior orbital fissures
33
Q

What is CN 7

A
  • facial nerves
  • Motor - Muscles of facial expression & stapedius, PSNS to glands
  • Sensory - Taste from anterior 2/3 of tongue, Skin external acoustic meatus & auricle
  • internal acoustic meatuses to exit skull via stylomastoid foramina
34
Q

What is CN 8

A
  • Vestibulocochlear nerves (aka Auditory nerves)
  • Sensory - hearing (cochlear division) & eqbm/balance (vestibular division)
  • pass from inner ear to brainstem through internal acoustic meatus
35
Q

What is CN 9

A
  • glossopharyngeal nerves
  • Motor - PSNS fibers to parotid gland (salivary gland), Stylopharyngeus (elevates pharynx during swallowing)
  • Sensory - Taste - posterior 1/3 tongue , Sensory - posterior 1/3 tongue, oropharynx, tympanic membrane, middle ear, auditory tube, Impulses from carotid chemoreceptors & baroreceptors
  • Exit skull through jugular foramen
36
Q

What is CN 10

A
  • vagus nerve
  • Motor - PSNS innervation of heart, lungs & abdominal viscera, Muscles of larynx & pharynx
  • Sensory - Sensory info from thoracic/abdominal viscera & posterior ear/external acoustic meatus, Baroreceptors & chemoreceptors, Taste from posterior tongues & pharynx
  • Exit skull via jugular foramen
37
Q

What is CN 11

A
  • Spinal Accessory Nerve
  • Motor - trapezius & sternocleidomastoid
  • Rootlets of spinal cord > Foramen magnum > cranium > accessory nerves exit skull through Jugular foramina
38
Q

What is CN 12

A
  • Hypoglossal Nerves
  • Motor - tongue muscles contributing to swallowing & speech
  • Exit skull via hypoglossal canal
39
Q

What are spinal nerves?

A
  • 31 pairs of mixed nerves
  • Named according to point of issue from spinal cord
40
Q

What is Dermatome

A
  • Area of skin innervated by cutaneous branches of a single spinal nerve
  • All spinal nerves except C1
  • Way of determining site of spinal cord damage
41
Q

What is the flow of spinal nerves? from cord to rami

A

spinal cord > rootlets > root > spinal nerve > rami

42
Q

What are the 4 mixed rami?

A
  • Meningeal branch - to spinal meninges & blood vessels
  • Dorsal ramus - to posterior body trunk
  • Ventral ramus - form plexuses
  • Rami communicantes - autonomic pathways
43
Q

Why do we have a plexus of ventral rami

A
  • each muscle in a limbreceives its nerve supply from more than 1 spinal nerve
  • damaging one spinal segment will not completely paralyze a limb
44
Q

What is the Cervical Plexus? Purpose?

A
  • Innervated skin & muscles of neck, ear, back of head & shoulders
  • Phrenic nerve - C345 keeps diaphragm alive
  • Keeps you breathing
45
Q

What is the Brachial Plexus?

A
  • Formed by ventral rami of C5-T1
  • Gives rise to nerves that innervated upper limb & pectoral girdle (motor & sensory)
46
Q

What are the 5 Terminal branches (peripheral nerves) of the Brachial Plexus

A
  • radial (P)
  • axillary (P)
  • musculocutaneous (A)
  • median (A)
  • ulnar (A)
47
Q

What is function of Radial Nerve

A
  • M - posterior muscles of arm
  • S - posterior skin of arm
48
Q

What is function of Axillary Nerve

A
  • M - deltoid, teres minor
  • S - skin & joint capsule of shoulder
49
Q

What is function of Musculocutaneous Nerve

A
  • M - anterior arm muscles
  • S - skin of lateral forearm
50
Q

What is function of Median Nerve

A
  • M - lateral flexors & pronators in forearm & some intrinsic muscles of hand
  • S - skin of lateral aspect of hand
51
Q

What is function of Ulnar Nerve

A
  • M - anterior medial forearm muscles & medial intrinsic muscles of hand
  • S - skin of medial aspect of hand
52
Q

What does the Lumbar plexus innervate? What are the nerves?

A
  • Innervated thigh, abdominal wall & psoas muscles
  • Obturator nerve - passes through obturator foramen to innervate adductor muscles
  • Femoral nerve - innervated anterior thigh muscles & skin of anterior/medial thigh & medial leg
53
Q

What does the Sacral plexus innervate? What are the nerves?

A
  • Serves buttock, lower limb, pelvic structures, & perineum
    • Pudendal nerve - skin/muscles of perineum
    • Sciatic nerve - longest/thickest nerve of body
      ○ Innervates hamstrings, adductor magnus, & most muscles in leg & foot
      ○ Composed of tibial & common fibular nerves
54
Q

What is a muscle spindle

A
  • Composed of 3-10short intrafusal muscle fibers in a CT capsule
  • Intrafusal fibers - noncontractile in central regions (lack myofilaments)
55
Q

Sensory Innervation of muscle spindles

A
  • Intrafusal muscle fibers wrapped w/ 2 types of afferent (sensory) endings
  • Primary sensory endings (type Ia fiber) - rate & degree of stretch
  • Secondary sensory endings (type II fiber) - degree of stretch
56
Q

Motor Innervation of muscle spindles

A
  • Contractile end regions are innervated by gamma (y) efferent fibers that maintain spindle sensitivity
  • Just the ends of spindles have contractile unit
57
Q

If only motor neurons of muscle spindle are activated…

A
  • only extrafusal muscle fibers contract
  • muscle spindle becomes slack & no APs are fired
  • unable to signal further length changes
58
Q

if a-y Coactivation of muscle spindle occurs …

A
  • both extrafusal & intrafusal muscle fibers contract
  • muscle spindle tension is maintained
  • can signal changes in length
59
Q

What are the parts to a spinal reflex

A
  • Integration center is in spinal cord
  • Effectors are skeletal muscle
  • receptor > sensory neuron > integration center > motor neuron > effector
60
Q

What is a stretch reflex

A
  • Maintain muscle tone in large postural muscles
  • Cause muscle contraction in response to increased muscle length (stretch)
  • All stretch reflexes are monosynaptic & ipsilateral
61
Q

What is a Golgi tendon reflex

A
  • Polysynaptic reflexes
  • Help to prevent damage due to excessive stretch
  • Produce muscle relaxation in response to tension
  • Contracting muscle relaxes & antagonist contracts (reciprocal activation)
62
Q

What is a flexor reflex

A
  • Painful stimulus causes automatic withdrawal of threatened body part
  • Ipsilateral & polysynaptic
    Reciprocal inhibition
63
Q

What is a crossed-extensor reflex

A
  • Occurs w/ flexor reflexes in weight-bearing limbs to maintain balance
  • Consists of ipsilateral flexor reflex & contralateral extensor reflex
    ○ Stimulated side is withdrawn (flexed)
    ○ Contralateral side is extended

PHARM 110 (12 decks)

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