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PHARM 110 - Anatomy and Physiology > Peripheral Nervous System - > Flashcards

Peripheral Nervous System - Flashcards

1
Q

What are the two major divisions of the peripheral nervous system?

A

Somatic and Autonomic

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2
Q

What are the two divisions of the autonomic nervous system?

A

Sympathetic and para-sympathetic

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3
Q

What are sensory receptors classified by?

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

How does transduction occur in sensory receptors?

A

stimulus energy is converted into a graded potential which must reach threshold for nerve impulse

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5
Q

What are pain receptors called and what type of fibers carry impulses there?

A

Nociceptors

  • type A (myelinated) fibers carry fast pain sensations
  • type C (unmyelinated) fibers carry slow pain sensations
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6
Q

What do chemoreceptors do?

A

Respond to water soluble and lipid soluble substances dissolved in body fluids

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7
Q

What do mechanoreceptors do and what are the subtypes of mechanoreceptors (3)?

A

Sensitive to stimuli that distort the plasma membrane –> mechanically gated ion channels

  1. Proprioceptors –> watch positions of joints
  2. Baroreceptors –> detect changes in pressure (inside stimulus, changes in blood vessels)
  3. Tactile receptors –> sensations of touch, pressure and vibrations (outside stimulus)
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8
Q

What are the three classifications of sensory receptors according to location?

A
  1. Externoreceptors –> response to stimuli from outside the body (skin and most special sense organs)
  2. Internoceptors –> respond to stimulus from internal viscera and blood vessels; sensitive to chemical changes, tissue stretch and temperature changes)
  3. Proprioceptors –> Respond to stretch in skeletal muscles, joints, tendons, ligaments and connective tissues covering bones and muscles (lets the brain know what is happening)
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9
Q

What are the anatomical classifications of sensory receptors according to structural complexity?

A
  1. Unencapuslated nerve endings

2. Encapsulated nerve endings

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10
Q

Where would you find unencapsulated nerve endings and what type of fibers are they usually made of?

A

Found abundantly in epithelial and connective tissue, mainly group C fibers and they are not protected by accessory structures

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11
Q

What type of receptors have encapsulated nerve endings and what are they enclosed by?

A

Mechanoreceptors –> enclosed by connective tissue capsule

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12
Q

What is the classification of hair follicle receptors?

A
  • unencapsulated dendritic endings
  • mechanoreceptors wrapped around air
  • rapidly adapting
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13
Q

What unencapsulated receptors have free nerve endings?

A
  • thermoreceptors (cold receptors 10-40 degrees are superficial while heat receptors 32-48 degrees are deeper)
  • Mechanoreceptors
  • Nocioreceptors
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14
Q

What is a Merkel disk and where are they found?

A

Mechanoreceptors for light steady pressure –> found in the basal layer of epidermis

*slowly adapting

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15
Q

What are Meissner’s corpuscles, what do they do and where are they found?

A

–> ENCAPSULATED dendritic endings

–> detects light pressure, discriminative touch, low frequency vibrations

–> found in dermal papillae of hairless skin

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16
Q

What are Pacinian corpuscles, what do they do and where are they found?

A

–> ENCAPSULATED dendtritic endings

–> sense deep pressure, stretch, high frequency vibratiion

–> found in the dermis and hypodermis

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17
Q

What are Ruffini endings, what do they do and where are they found?

A

–> ENCAPSULATED dendritic endings

–> receptive to continuous pressure and stretch

–> found in the dermis, hypodermis and joint capsule

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18
Q

What are the superficial and deep fast adapting dendritic endings?

A

Superficial: Miessner corpuscles

Deep: Pacinian corpuscles

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19
Q

What are the superficial and deep slow adapting dendritic endings?

A

Superficial: Merkel cells

Deep: Ruffini endings

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20
Q

What is the difference between sensation and perception?

A

Sensation: awareness of changes in the internal and external environment

Perception: conscious interpretation of the stimuli

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21
Q

What are the 3 basic levels of neural integration in sensory systems?

A
  1. Receptor level
  2. Circuit level
  3. Perceptual level
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22
Q

What must happen in order for a sensation to occur?

A

Stimulus must excite the receptor (must match receptor specificity and applied in receptive field), transduction occurs (changing stimulus energy into graded potential) and the action potential has to reach the CNS (graded potential must reach threshold)

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23
Q

What does adaptation mean in terms of sensory receptors?

A

Change in sensitivity to a constant stimulus –> receptor membranes become less responsive and potentials decline or stop

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24
Q

What is a phasic receptor?

A

Fast-adapting –> sends signals at the beginning or end of a stimulus

Ex: receptors for pressure, touch and smell

  • think about a smell being in a room, you stop noticing it after a while
  • think clothes, you don’t feel your clothes on your body all day
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25
Q

What is a tonic receptor?

A

Adapt slowly or not at all

Ex: nociceptors and most proprioceptors –> you need pain in order for these to actually “turn on”

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26
Q

What happens when stimulus is being processed at a circuit level?

A

Pathways of 3 NEURONS conduct sensory impulses received from receptors towards appropriate cortical regions

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27
Q

What does feature abstraction mean as an aspect of sensory perception?

A

Identification of more complex aspects of multiple stimuli properties –> being able to describe properties of something without knowing what it is

Ex: velvet is compressible and smooth but not completely continuous

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28
Q

Pain impulses travel on what type of fibers? What do they release?

A

Thinly myelinated α fibers –> release glutamate

Unmyelinated C fibers –> release glutamate and substance P

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29
Q

What does pain warn?

A

Actual or impending tissue damage

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30
Q

What is gate control theory?

A

Non-painful inputs (AB) inhibit pain transmission (C fibers)

–> less of the information is actually going through but only while there is an application of stimulus

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31
Q

What is involved in descending pain control?

A
  • some pain impulses are blocked by inhibitory endogenous opioids (endorphins and enkephalins)
  • Descending fibers from cortex & hypothalamus release INHIBITORY neurotransmitters which suppress pain signals
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32
Q

What does hyperalgesia mean?

A

pain amplification

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33
Q

How do we “learn” pain and what does this mean?

A

NDMA receptors allow the spinal cord to “learn” hyperalgesia (as this is used more, the body gets better at feeling pain and this can lead to chronic pain)

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34
Q

What is referred pain?

A

Pain that is coming from a different region in the body but it actually comes from somewhere else.

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35
Q

What is the criteria for a neuron to be able to regenerate?

A

If the body is still intact but the axon is damaged, it can regenerate using coordinated activity between macrophages, Schwaan cells, and axons

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36
Q

What supporting neural cells have growth-inhibiting proteins?

A

ogliodendrocytes

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37
Q

What supporting neural cells cause scarring?

A

Astrocytes form scar tissues –> prevents the CNS fiber regeneration

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38
Q

What are the steps in regenerating an axon?

A
  1. Wallerian degeneration: Sheath breaks down distally (towards axon terminal)
  2. Macrophages clean out the dead axon distal to the injury
  3. Axon sprouts grow through the regeneration tube made by the Schwaan cells
  4. Axon regenerates and new myelin sheath is formed
39
Q

What are the two classifications of PNS nerves?

A

Cranial and spinal nerves

40
Q

What is CN I?

A

Olfactory –> special sensory; smell

  • comes from the olfactory receptor cells of nasal cavity
  • go through ciribriform plate
  • fibers synapse in olfactory bulbs
  • pathway reaches to primary olfactory cortex
41
Q

What is CN II?

A

Optic –> special sensory; sight

  • come from retinas, pass through optic canal, converge and partially cross in optic chiasma
  • continue to thalamus
42
Q

How can you test CN II?

A

Holding up fingers and asking them to tell you how many fingers you’re holding up

43
Q

What is CN III?

A

Oculomotor –> motor nerve

  • somatic: raises eyelid - levator palpabrae superioris
  • PSNS: sphinter pupillae & cilliary muscle

Exits through superior orbital fissure to muscles around the eye

44
Q

What is CN IV?

A

Trochlear –> motor

Innervates superior oblique muscle, lever system

Exits through superior orbital fissure

45
Q

What is CN V?

A

Trigeminal –> both motor and sensory

46
Q

What are the three divisions of the CN V, where do they pass through and are they sensory or motor?

A

CN V = Trigeminal nerve

  1. Opthalmic (V1) –> passes through superior orbital fissure
    - sensory only
  2. Maxillary (V2) –> passes through foramen rotundum
    - sensory only
  3. Mandibular (v2) –> passes through foramen ovale
    - sensory and motor
    - muscles of mastication, tensor tympani, and tensor celi palatine
47
Q

How would you test for functioning of CN V?

A

CN V = Trigeminal

Touching the forehead (V1)
Touching the cheek (V2)
Touching the jaw and watching mastication movements (V3)

48
Q

What is CN VI?

A

Abducens –> motor

  • innervates lateral rectus muscle
  • exits through superior orbital fissure
49
Q

Explain the mnemonic LR6SO4 and all the rest are 3

A

Lateral rectus is innervated by CN VI
Superior oblique is innervated by CN IV

all the other eye muscles are innervated by CN III

50
Q

What is cranial nerve VII?

A

Facial –> both sensory and motor

  • travels through internal acoustic meatuses, exits skull at stylomastoid foamina

Motor: muscles of facial expressions and stapedius, PSNS to glands

Sensory: taste from anterior 2/3 of the tongue, skin external acoustic meatus and auricle

51
Q

What is cranial nerve VIII?

A

Vestibulocochlear/Auditory –> special sensory; hearing

Cochlear division - hearing
Vestibular division - equilibrium and balance

Afferent fibers go from inner ear to brainstem through internal acoustic meatuses

52
Q

What is cranial nerve IX?

A

Glossopharyngeal –> both sensory and motor

Motor: PSNS to parotid gland, stylopharyngeus which elevates pharynx during swallowing

Sensory: taste on posterior 1/3 of tongue, sensor for pressure (how much blood is going into the brain and the chemical composition of it)

53
Q

What is Cranial nerve X?

A

Vagus –> both sensory and motor

Motor: PSNS innervation of heart, lungs and abdominal viscera, muscles of larynx and pharynx

Sensory: thoracic/abdominal viscera, external acoustic meatus, and taste from posterior tongue and pharynx
–> baroreceptors and chemotrceptors

54
Q

What does vagus mean?

A

Wanderer –> the nerve wanders from the brain all the way to the viscera (liver, stomach, kidneys, intestines)

55
Q

What is cranial nerve XI?

A

Spinal Accessory –> motor
- innervates trapezius and sternocleidomastoid

Formed from ventral rootlets from C1-C5 region of spinal cord (NOT THE BRAIN), enters brain through foramen magnum and exits through jugular foramen

56
Q

How do you test CN XI?

A

CN XI = Spinal accessory nerves

Test the surrounding muscles for function

57
Q

What is cranial nerve XII?

A

Hypoglossal –> motor
- innervates majority of tongue muscles contributing to swallowing and speech

Exits skull through hypoglossal canal

58
Q

How would you test for CN VII?

A

CN VII = facial nerve

If a person can open their eyes and mouth really wide and shut them really tight

Also testing for symmetry - do both sides of the lips move up when smiling?

59
Q

What is a dermatome and what is it used for?

A

Area of skin innervated by cutaneous branches of a single spinal nerve –> used to determine spinal cord damage

60
Q

What is Hilton’s law?

A

Any nerve serving a muscle that produces movement at a joint also innervates the joint and the skin over the joint

61
Q

What is the organization of the spinal cord to rami?

A

Spinal cord –> rootlets –> root –> spinal nerve –> rami

62
Q

Each spinal nerve branches into 4 mixed rami, what are these rami?

A
  1. Meningeal branch: to spinal meninges and blood vessels
  2. Dorsal ramus: to posterior body trunk
  3. Ventral ramus: form plexuses
  4. Rami communicantes: autonomic pathways (join to ventral rami in thoracic region)
63
Q

What are the exceptions of ventral ramus forming plexuses?

A

T2-T12: they act as intercostal nerves –> muscles of ribs, anerolateral thorax & abdominal walls

64
Q

Why do we have plexuses of ventral rami?

A

Plexus of ventral rami allows each limb to receive nerve supply from multiple spinal cords –> the benefit is that damaging one spinal segment or root will not completely paralyze any limb muscle

65
Q

What does the cervical plexus do and where is it?

What is the very important nerve in the plexus?

A

Cervical plexus runs from C1-C5 –> it innervates skin and muscles of neck, ear, back of the neck and shoulders

C345 = Phrenic nerve
This nerve keeps the diaphragm alive, very important for breathing

66
Q

What happens if you damage the spinal cord above C1 or C2? What about below that?

A

Above C1, C2 –> could be fatal

Just below that you would still be able to breathe but not move

67
Q

What ventral rami forms the brachial plexus and what does it do?

A

Brachial plexus is made from C5-C8 and T1 –> innervates upper limb and pectoral girdle

68
Q

Be able to draw the brachial plexus

What is the easy way to do this?

A

Three Y’s men went bowling. One got a strike and one got a spare

  1. Draw the sideways Y’s, the open end of the top and bottom one at the right side of the page
  2. the M (for men) goes between the sticks at the ends of the first and second Y
  3. the strike (X) goes in between the first and second Y
  4. the spare () goes between the second and the third Y
69
Q

What are the branches of the brachial plexus?

A

Musculotaneous, axillary, median, radial, and ulnar

in descending order according to the brachial plexus map

70
Q

What are the general functions of the radial branch?

A

Motor: post posterior muscles of limb

Sensory: posterior skin of limb

71
Q

What are the general functions of the Axillary branch of the brachial plexus?

A

Motor: deltoid, teres minor

Skin: skin & joint capsule of the shoulder

72
Q

What are the general functions of the musculocutaneous branch of the brachial plexus?

A

Motor: anterior arm muscles

Sensory: skin of lateral forearm

73
Q

What are the general functions of the median branch of the brachial plexus?

A

Motor: most lateral flexors & pronators in forearm + some lateral intrinsic muscles muscles of hand

Sensory: skin of lateral aspect of hand

74
Q

What are the general functions of the of the ulnar branch of the brachial plexus?

A

Motor: anterior medial forearm muscles and most medial intrinsic muscles of hand

Sensory: skin of medial aspect of hand

75
Q

What nerves make up the lumbar plexus and what is its function?

A

L1-L4 make up the lumbar plexus –> innervates thigh, abdominal wall and psoas major

76
Q

Which nerves make up the lumbar plexus and what do they innervate?

A

Obturator nerve –> innervates adductor muscles

Femoral nerve –> innervates anterior thigh muscles and skin of anterior/medial thigh and medial leg

Pudendal nerve –> skin and muscles of perineum

Siatic nerve –> innervates hamstrings, adductor magnus and most muscles in leg and foot

77
Q

What is a muscle spindle?

A

Made of 3-10 short intrafusal muscle fibers in a connective tissue capsule

78
Q

What is an intrafusal fiber?

A

Non-contractile in central regions (lack myofilaments) –> contractile components at the end and they sense the stretch in the muscles

79
Q

What are the 2 different types of afferent endings in intrafusal fibers?

A

Primary/anulospiral –> sensory endings that innervate spindle centre and are stimulated by rate and degree of stretch

Secondary/flower spray –> sensory endings of type 2 fibers that innervate spindle ends and degree of stretch

80
Q

What fibers maintain spindle sensitivity?

A

gamma efferent fibers –> innervate contractile end regions

81
Q

What innervates extrafusal fibers

A

α efferent fibers

Extrafusal fibers are also called contractile muscle fibers

82
Q

What are the two ways to excite muscle spindles?

A
  1. External stretch of muscle and muscle spindle
  2. internal stretch of muscle spindle –> activating gamma motor neurons stimulates ends to contract and stretches muscle spindle
83
Q

Explain co-activation of muscle spindles

A

Both intrafusal and extrafusal muscle fibers contract –> muscle spindle tension is maintained and it can still signal the changes in length of the muscle

*if we did not have this function, activity would be lost - co-activation is necessary to determine sensitivity (we would know that there was a contraction but have no idea how much of a contraction)

84
Q

What are the two types of reflexes?

A
  1. Inborn/intrinsic –> rapid, involuntary, predictable motor response to stimulus
  2. Learned/acquired reflexes –> resulting from practice or repetition
85
Q

How do spinal reflexes work and why are they important?

A

Spinal somatic reflexes have an integration center in the spinal cord and the effectors are skeletal muscle

These are important because they can clinically evaluate sensorimotor function of body

86
Q

What is a Golgi tendon organ and what does it do?

A

Golgi tendon organ is the inside of a tendon and has afferent sensory neurons that tell the brain the amount of tension in muscle and tendons

87
Q

What is the importance of stretch reflexes?

A

They maintain muscle tone in large postural muscles and cause muscle contraction in response to increased muscle length

These reflexes are monosynaptic and ipsilateral

88
Q

Explain the steps in the patellar reflex

A
  1. tapping the ligament excites the muscle spindles in the quadriceps femoris
  2. Afferent impulses (la primary sensory endings) travel to the spinal cord where they synapse with α motor neurons and interneurons
  3. α motor neurons send activating impulses to quads and cause them to contract (extends the knee)
    - -> interneurons make inhibitory synapses with ventral horn neurons that stop the contraction of antagonist muscles (hamstrings)
89
Q

Explain reciprocal inhibition

A

the way interneurons will make inhibitory synapses with ventral horn neurons that stop contracting antagonist muscles

90
Q

What does a Golgi tendon reflex do?

A

Helps prevent damage due to excessive stretch and is important for smooth onset and termination of muscle contraction

Produces muscle RELAXATION in response to tension

  • afferent impulses transmitted to spinal cord
  • contracting muscle relaxes and antagonist contracts (reciprocal activation)
  • information transmitted simultaneously to cerebellum is used to adjust muscle tension
91
Q

What is the purpose of flexor reflexes?

A

Flexor reflex = withdrawal reflex

Painful stimulus causes automatic withdrawal of threatened body part –> ipsilateral

92
Q

What is a crossed-extensor reflex and why is it important?

A

Occurs with flexor reflexes in weight-bearing limbs to MAINTAIN BALANCE

need this to be able to walk –> stimulated side is withdrawn and the contralateral side is extended (reflex consists of ipsilateral flexor reflex and contralateral extensor reflex)

93
Q

What is a superficial reflex? What are some examples?

A

Excited by gentle cutaneous stimulation –> polysnaptic reflexes that depend on upper motor pathways & cord-level reflex arcs

Ex: plantar reflex, abdominal reflexes, cremaster reflex

PHARM 110 - Anatomy and Physiology (6 decks)

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