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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
What are the Steps to Nerve Fiber Regeneration
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
26
What are the 2 classifications of peripheral nerves?
* cranial nerves * spinal nerves
27
What is cranial nerve 1 | name, function, pathway
* Olfactory nerves * Sensory - olfaction * Olfactory receptors of nasal cavity > cribriform plates > synapse in olfactory bulbs > primary olfactory cortex
28
What is CN 2
* optic nerves * Sensory - vision * Retinas > optic canals > cross at optic chiasma > thalamus (LGN) > visual cortex
29
What is CN 3
* 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
What is CN 4
* Trochlear nerves * Motor - superior oblique muscle Exit through superior orbital fissures
31
What is CN 5
* 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
What is CN 6
* abducens nerves * Motor - lateral rectus muscle * Exit through superior orbital fissures
33
What is CN 7
* 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
What is CN 8
* Vestibulocochlear nerves (aka Auditory nerves) * Sensory - hearing (cochlear division) & eqbm/balance (vestibular division) * pass from inner ear to brainstem through internal acoustic meatus
35
What is CN 9
* 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
What is CN 10
* 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
What is CN 11
* Spinal Accessory Nerve * Motor - trapezius & sternocleidomastoid * Rootlets of spinal cord > Foramen magnum > cranium > accessory nerves exit skull through Jugular foramina
38
What is CN 12
* Hypoglossal Nerves * Motor - tongue muscles contributing to swallowing & speech * Exit skull via hypoglossal canal
39
What are spinal nerves?
* 31 pairs of mixed nerves * Named according to point of issue from spinal cord
40
What is Dermatome
* 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
What is the flow of spinal nerves? from cord to rami
spinal cord > rootlets > root > spinal nerve > rami
42
What are the 4 mixed rami?
* Meningeal branch - to spinal meninges & blood vessels * Dorsal ramus - to posterior body trunk * Ventral ramus - form plexuses * Rami communicantes - autonomic pathways
43
Why do we have a plexus of ventral rami
* 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
What is the Cervical Plexus? Purpose?
* Innervated skin & muscles of neck, ear, back of head & shoulders * Phrenic nerve - C345 keeps diaphragm alive * Keeps you breathing
45
What is the Brachial Plexus?
* Formed by ventral rami of C5-T1 * Gives rise to nerves that innervated upper limb & pectoral girdle (motor & sensory)
46
What are the 5 Terminal branches (peripheral nerves) of the Brachial Plexus
* radial (P) * axillary (P) * musculocutaneous (A) * median (A) * ulnar (A)
47
What is function of Radial Nerve
* M - posterior muscles of arm * S - posterior skin of arm
48
What is function of Axillary Nerve
* M - deltoid, teres minor * S - skin & joint capsule of shoulder
49
What is function of Musculocutaneous Nerve
* M - anterior arm muscles * S - skin of lateral forearm
50
What is function of Median Nerve
* M - lateral flexors & pronators in forearm & some intrinsic muscles of hand * S - skin of lateral aspect of hand
51
What is function of Ulnar Nerve
* M - anterior medial forearm muscles & medial intrinsic muscles of hand * S - skin of medial aspect of hand
52
What does the Lumbar plexus innervate? What are the nerves?
* 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
What does the Sacral plexus innervate? What are the nerves?
* 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
What is a muscle spindle
* Composed of 3-10short intrafusal muscle fibers in a CT capsule * Intrafusal fibers - noncontractile in central regions (lack myofilaments)
55
Sensory Innervation of muscle spindles
* 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
Motor Innervation of muscle spindles
* Contractile end regions are innervated by gamma (y) efferent fibers that maintain spindle sensitivity * Just the ends of spindles have contractile unit
57
If only motor neurons of muscle spindle are activated...
* only extrafusal muscle fibers contract * muscle spindle becomes slack & no APs are fired * unable to signal further length changes
58
if a-y Coactivation of muscle spindle occurs ...
* both extrafusal & intrafusal muscle fibers contract * muscle spindle tension is maintained * can signal changes in length
59
What are the parts to a spinal reflex
* Integration center is in spinal cord * Effectors are skeletal muscle * receptor > sensory neuron > integration center > motor neuron > effector
60
What is a stretch reflex
* Maintain muscle tone in large postural muscles * Cause muscle contraction in response to increased muscle length (stretch) * All stretch reflexes are monosynaptic & ipsilateral
61
What is a Golgi tendon reflex
* 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
What is a flexor reflex
* Painful stimulus causes automatic withdrawal of threatened body part * Ipsilateral & polysynaptic Reciprocal inhibition
63
What is a crossed-extensor reflex
* 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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