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Anatomy & Physiology 207 > Peripheral Nervous System Part I Study Guide > Flashcards

Peripheral Nervous System Part I Study Guide Flashcards

1
Q

How is the peripheral nervous system essential to our survival?

A

Provides the links between our brains and the outside world
Consistent sensory inputs and motor outputs are essential to survival

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2
Q

What anatomical structures make up the peripheral nervous system?

A

Sensory receptors, afferent nerves + efferent nerves and their associated ganglia, and motor endings

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3
Q

What are sensory receptors specialized to do?

A

respond to changes in their environment

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4
Q

What happens when a sensory receptor is activated?

A

results in graded potentials that trigger nerve impulses

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5
Q

What happens when the generated nerve impulses reach the brain?

A

Once nerve impulses (sent along the afferent pns fibers to the cns) reach the brain, awareness of the stimulus (sensation) and interpretation of the meaning of the stimulus (perception) occurs in the brain

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6
Q

What are the 5 TYPES of receptors we discussed in class? (Classification by stimulus type)

A

Mechanoreceptors
Thermoreceptors
Photoreceptors
Chemoreceptors
Nociceptors

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7
Q

Mechanoreceptors

A

respond to mechanical forces such as touch, pressure, vibration, and stretch

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8
Q

Thermoreceptors

A

respond to changes in temperature

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9
Q

Photoreceptors

A

respond to light energy (ex-retina)

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10
Q

Chemoreceptors

A

response to chemicals in solution (ex-smell, taste, changes in blood chemistry)

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11
Q

Nociceptors

A

respond to pain-causing stimuli; these stimuli are potentially harmful (ex-extreme heat, cold, pressure, or inflammatory chemicals)

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12
Q

exteroreceptor

A
  • Classification by location
  • Respond to stimuli arising outside the body
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13
Q

location of exteroreceptor

A

the body’s surface
- ex. receptors in the skin for touch, pressure, pain, and temperature, and most receptors for the special sense (vision, hearing, equilibrium, smell, and taste)

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14
Q

interoreceptor

A
  • Classification by location
  • Respond to internal stimuli such as from the internal viscera and blood vessels
  • Respond to changes in stretch and body position - inform the brain of one’s movements
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15
Q

location fo interoreceptors

A

Occur in skeletal muscles, tendons, joints, ligaments, and the connective tissue coverings of the bones and muscles

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16
Q

2 structural classifications for receptors

A
  • Simple receptors of the general senses
  • Receptors of the special sense
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17
Q

General sensory receptors are either _______________ or ________________

A
  • nonencapsulated (free) nerve endings
  • encapsulated nerve endings
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18
Q

location of nonencapsulated nerve endings

A

Abundant in epithelial and connective tissues

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19
Q

What type of fiber are nonencapsulated nerve endings made of

A

Most are nonmyelinated, small diameter, group C fiber; distal terminals have knoblike swellings

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20
Q

what kinds of stimuli do nonencapsulated nerve endings typically respond to

A

mostly to temperature, pain, or light touch

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21
Q

thermoreceptors

A
  • Cold receptors are activated by temps from 50-104°F
  • Located in the superficial dermis
  • Average skin temperature is about 93°F
  • Heat receptors are activated by temps from 89-118°F
  • Located in the deeper dermis
  • Outside of these temperature ranges, heat or cold trigger nociceptors and are interpreted as pain
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22
Q

Nociceptors

A

pain receptors that respond to extreme temperatures, pinch, or the release of chemicals from damaged tissue

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23
Q

Itch receptors

A

located in the dermis, activated by the chemical histamine

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24
Q

Tactile (merkel) discs

A

lie at the junction of the epidermis and dermis; function as light touch receptors

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25
Q

Hair follicle receptors

A

free nerve endings that wrap around hair follicles – act as light touch receptors that detect bending of the hairs

26
Q

What makes a nerve fiber “encapsulated”?

A

One or more fiber terminals of sensory neurons enclosed in connective tissue capsules

27
Q

Almost all encapsulated dendritic endings are ____________.

A

mechanoreceptors

28
Q

Tactile (Meissner’s) Corpuscles

A

small receptors involved in discriminative touch – found just below the epidermis, mostly in sensitive and hairless areas

29
Q

Lamellar (Pacinian) Corpuscles

A

large receptors that respond to 1st application of deep pressure and vibration – located deep in the dermis and subcutaneous tissue

30
Q

Bulbous Corpuscles (Ruffini Endings)

A

a spray of nerve endings, respond to deep and continuous pressure – located in the dermis, subcutaneous tissue, and joint capsules

31
Q

Muscle Spindles

A

spindle-shaped proprioceptors that respond to muscle stretch; found in the perimysium; initiate the stretch reflex

32
Q

Tendon Organ

A

proprioceptors located in tendons; detect stretch; initiate the stretch/relax reflex

33
Q

Joint Kinesthetic Receptors

A

proprioceptors that monitor stretch in the articular capsules; provide information on joint position and motion

34
Q

nerve

A

Cordlike organ of the pns – a bundle of myelinated and nonmyelinated peripheral axons enclosed by connective tissue

35
Q

2 types of nerves

A

cranial and spinal

36
Q

connective tissue coverings for the different layers of the nerve

A

Endoneurium
Perineurium
Epineurium

37
Q

Endoneurium

A

loose connective tissue that encloses individual axons + their myelin sheaths

38
Q

Perineurium

A

coarse connective tissue that bundles fibers into fascicles

39
Q

Epineurium

A

tough, fibrous sheath that encloses all fascicles and blood + lymphatic vessels to form a nerve

40
Q

Most nerves contain a mixture of what 4 things?

A
  • Afferent + Efferent fibers
  • Somatic + Autonomic (visceral) fibers
41
Q

Mixed Nerves

A

contain both sensory and motor fibers – impulses travel both to and from the CNS

42
Q

Sensory (Afferent) Nerves

A

impulses only move toward the CNS

43
Q

Motor (Efferent) Nerves

A

impulses only move away from the CNS

44
Q

Are sensory nerves efferent or afferent? What about motor nerves?

A
  • Sensory nerves are afferent
  • Motor nerves are efferent
45
Q

What happens if damage to a neuron is close to the cell body

A

the whole neuron may die – other neurons typically stimulated by its axons may also die

46
Q

what if there is damage is further from the cell body?

A

axons in the pns can regenerate – axons in the cns cannot regenerate

47
Q

Compare/contrast nerve regeneration in the central and peripheral nervous systems. Which system has more regeneration capacity? Be sure to understand the respective roles played by oligodendrocytes and Schwann cells.

A
  • Pns has more regenerative capacity – axons of the cns do not regenerate
  • Oligodendrocytes of the cns bear growth inhibiting proteins that prevent cns fiber regeneration
  • Schwann cells are stimulated to divide in order to regenerate axons of the pns very slowly
48
Q

wallerian degeneration

A

Pns only – axon fragments and myelin sheaths distal to the injury degenerate

49
Q

peripheral motor ending

A

Pns elements that activate effectors by releasing neurotransmitters

50
Q

examples of effectors activated by the PNS

A

skeletal muscles (neuromuscular junction), visceral muscles, and glands

51
Q

3 levels of motor control in the PNS

A

Segmental level
Projection level
Precommand level

52
Q

movements are controlled by the segmental level

A

Reflexes and automatic movements

53
Q

CPGs

A

circuits that control locomotion and specific, often repeated motor activities

54
Q

What happens at the projection level of control? Reminder this is your middle manager role!

A
  • Projection level consists of neurons acting through direct and indirect motor pathways
  • Upper motor neurons of the motor cortex initiate direct (pyramidal) pathways to produce voluntary skeletal muscle movements
  • Brain stem motor nuclei oversee indirect (extrapyramidal) pathways to control and modify reflex and CPG-controlled motor areas
  • Projection motor pathways send information to lower motor neurons and keep the higher command levels informed
55
Q

2 anatomical areas are responsible for the precommand level of control

A

Cerebellum
Basal nuclei

56
Q

List the specific functions of the precommand level of control.

A
  • Regulating motor activity
  • Precisely start and stop movements
  • Coordinating movements with posture
  • Blocking unwanted movements
  • Monitoring muscle tone
  • Performing unconscious planning and discharge in advance of willed movements
57
Q

Inborn (Intrinsic) Reflex

A

rapid, involuntary, predictable motor response to a stimulus
- Regulated by the subconscious lower regions of the CNS – the brain stem and spinal cord
- Ex: maintain posture, control visceral activities
- Inborn reflexes are unlearned, but they can be modified by learning and conscious effort
- ex. When we are holding something hot but instead of dropping it we burn ourselves and put the hot thing down in a safe place (like food)

58
Q

Learned (Acquired) Reflex

A

results from practice and repetition
Ex: driving a car

59
Q

effectors in a somatic reflex

A

skeletal muscles

60
Q

effectors in a autonomic reflex

A

visceral effectors (smooth/cardiac muscles, glands)

Anatomy & Physiology 207 (44 decks)

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