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Anatomy and Physiology I > Chapter 13: The Peripheral Nervous System and Reflex Activity > Flashcards

Chapter 13: The Peripheral Nervous System and Reflex Activity Flashcards

1
Q

5 sensory receptors classified by stimulus type

A
  1. Mechanoreceptors
  2. Thermoreceptors
  3. Photoreceptors
  4. Chemoreceptors
  5. Nociceptors
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2
Q

Mechanoreceptors

A

respond to touch, pressure, vibration, and stretch

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3
Q

Thermoreceptors

A

sensitive to changes in temperature

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4
Q

Photoreceptors

A

respond to light energy, light sensitive (e.g., retina)

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5
Q

Chemoreceptors

A

respond to chemicals (e.g., smell, taste, changes in blood chemistry)

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6
Q

Nociceptors

A

sensitive to paint-causing stimuli (e.g., extreme heat or cold, excessive pressure, inflammatory chemicals)

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7
Q

1st step in regeneration of a PNS axon

A
  • the axon fragments
  • cut axon ends seal themselves off
  • axon transport interrupted, causing cut ends to swell
  • without access to cell body, axon and its myelin sheath begins to disintegrate distal to the injury
  • degeneration of distal end of cut axon, called Wallerian degeneration, spreads down axon
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8
Q

2nd step in regeneration of a PNS axon

A
  • Schwann cells and macrophages clean out dead axon distal to injury
  • surviving Schwann cells engulf myelin fragments and secrete chemicals that recruit macrophages
  • macrophages help dispose of debris and release chemicals that stimulate Schwann cells to divide
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9
Q

3rd step in regeneration of a PNS axon

A
  • axon filaments grow through a regeneration tube
  • Schwann cells release growth factors and express cell adhesion molecules (CAMs) that encourage axon growth
  • Schwann cells line up along the tube of remaining endoneurium, forming a regeneration tube that guides the regenerating axon “sprouts” across the gap to their original contact
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10
Q

4th step in regeneration of a PNS axon

A
  • the axon regenerates and a new myelin sheath forms
  • Schwann cells protect and support the regeneration axon and ultimately produce a new myelin sheath
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11
Q

Cranial nerves (I-XII)

A

I. Olfactory
II. Optic
III. Oculomotor
IV. Trochlear
V. Trigeminal
VI. Abducens
VII. Facial
VIII. Vestibulocochlear
IX. Glossopharyngeal
X. Vagus
XI. Accessory
XII. Hypoglossal

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12
Q

Sensory cranial nerves

A

I. Olfactory: smell
II. Optic: vision
VIII. hearing and balance: cochlea (hearing receptors) and vestibule of inner ear (equilibrium receptors)

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13
Q

Motor cranial nerves

A

III. Oculomotor
IV. Trochlear
VI. Abducens
XI. Accessory
XII. Hypoglossal

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14
Q

Motor cranial nerves: motor nerves for eye movement

A

III. Oculomotor: innervates 4/6 extrinsic eye muscles: inferior oblique, superior rectus, inferior rectus, medial rectus
IV. Trochlear: innervates 1/6 extrinsic eye muscles: superior oblique muscle
VI. Abducens: innervates 1/6 extrinsic eye muscles: lateral rectus muscle

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15
Q

Other motor cranial nerves

A

XI. Accessory: move head and neck innervates sternocleidomastoid and trapezius
XII. Hypoglossal: swallowing and speech; innervates all extrinsic and intrinsic muscles of tongue except palatoglossus

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16
Q

Sensory and motor cranial nerves

A

V. Trigeminal- sensory: general sensation; motor: mandibular branch, muscle of mastication (chewing)
VII. Facial- sensory: taste; motor: chief motor nerve of face- facial expression, lacrimal glands, salivary glands
IX. Glossopharyngeal- sensory: taste; motor: tongue and pharynx for swallowing, parotid salivary glands
X. Vagus- sensory: taste; motor: heart, lung and abdominal vescera (regulate heart rate, breathing, digestive system activity), pharynx and larynx (swallowing)

17
Q

Largest cranial nerve

A

Trigeminal (V): actually 3 nerves

18
Q

2 cranial nerves with multiple branches and names of the branches

A

Facial (VII): 5 branches- temporal, zygomatic, buccal, mandibular, and cervical
Trigeminal (V): 3 branches- ophthalmic, maxillary, and mandibular

19
Q

Tic Douloureux - cause & cranial nerve associated

A

Cause: compression of trigeminal nerve near brain stem
What is it: inflammation of trigeminal nerve, produces excruciating pain
* treated with meds, if unresponsive –> surgery to relieve compression or destroy nerve –> loss of sensation on side of face with destroyed nerve

20
Q

Bell’s palsy: cause & cranial nerve associated

A

cause: inflamed, swollen facial nerve, possibly due to herpes simplex 1 viral infection
What is it: paralysis of facial muscles on affected side with partial loss of taste
* treatment w/ corticosteroids

21
Q

Nerve Plexuses

A
  • interweaving network of nerves formed by branching and interconnection of ventral rami
  • each branch contains fibers from several different spinal nerves
22
Q

What is the benefit of arranging nerves in plexuses

A
  • damage to one branch does not cause paralysis because there are other branches involved in the plexus
  • allows for a more organized distribution of nerve signals to different body parts
23
Q

How might the major nerve of the sacral plexus be damaged

A
  • sciatica: stabbing pain in sciatic nerve
  • causes: fall, disc herniation, improperly placed injection buttocks
  • if nerve cut leg nearly useless- cannot flex leg, foot drop (plantar flexion bc foot and ankle cannot move)
  • recovery from sciatic nerve injury is slow and incomplete (deficits remain)
24
Q

Nerve plexuses and their major nerves

A
  • cervical; major nerve: phrenic
  • brachial; major nerves: axillary, musculocutaneous, median, radial, ulnar
  • lumbar; major nerves: femoral, obturator
  • sacral; major nerves: sciatic (composed of tibial and common fibular)
25
Q

Brachial plexus- how subdivisions are oriented from medial to lateral (4)

A
  1. Roots: five ventral rami (C5 to T1 which unite to form…
  2. Trunks: upper, middle, and lower, which unite to form…
  3. Divisions: anterior and posterior, which unite to form…
  4. Cords: lateral, medial, and posterior
26
Q

Intrinsic (inborn) reflexes

A
  • rapid, predictable, involuntary motor movements in response to some stimuli
  • not learned, not premeditated, subconscious (happen without thinking)
  • regulated by brain stem and spinal cord
  • ex. posture, control of visceral activities
27
Q

Learned (acquired) reflexes

A
  • acquired, result from practice or repetitions
  • ex. riding a bike, driving a car
  • with practice these activities become largely automatic bc we have put a lot of time and effort into developing the skill
28
Q

Dermatomes - what are they

A
  • area of skin innervated by cutaneous branches of a single spinal nerve (all spinal nerves except C1)
  • areas of skin that send signals to the brain through spinal nerves
29
Q

Dermatomes - how are they useful to clinicians

A
  • can help healthcare provider detect and diagnose conditions or problems affecting spine, spinal cord, or spinal nerves
  • extent of spinal cord injuries ascertained by affected dermatomes
30
Q

Stretch reflexes (4)

A
  • plantar
  • crossed extensor
  • knee-jerk
  • tendon reflex
31
Q

Stretch reflexes purpose

A
  • maintain posture and muscle tone in postural muscles
  • muscles contract if stretched too far
32
Q

Can you artificially trigger any of the stretch reflexes? If so, how would you trigger that stretch reflex to assess it in a clinical setting?

A

Stretch reflexes can be used for clinical testing, such as by tapping the patellar tendon, to stimulate the knee-jerk reflex, which slightly stretches the quadriceps muscle

33
Q

Babinski’s sign- what is it

A

damage to primary motor cortex or corticospinal tracts causes abnormal response called Babinski’s sign- big toe dorsiflexes, smaller toes fan out laterally
* normal response: downward curling (flexion) of toes

34
Q

What reflex is this associated with

A

plantar (babinski) reflex

35
Q

When is it normal vs abnormal to see babinski’s sign

A

normal: infants (1-1.5 years old) due to incomplete myelination of nerve fibers
abnormal: children older than 2

Anatomy and Physiology I (7 decks)

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