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Physiology > Peripheral Nervous System > Flashcards

Peripheral Nervous System Flashcards

1
Q

peripheral nervous system (PNS)

A

-composed of the afferent and efferent fibers that relay signals between the CNS and the periphery (other parts of the body)

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2
Q

afferent division

A

detects, encodes and transmits the peripheral signals to the CNS

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3
Q

sensory receptors

A
  • specialized peripheral ending of afferent neurons
  • each type responds to its one adequate stimulus
  • translates the energy form of the stimulus into electrical signals
  • process is called signal transduction
  • very specific
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4
Q

sensory transduction

A
  • the conversion of stimulus energy into a receptor potential
  • receptor potentials in turn trigger action potentials in the afferent fiber
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5
Q

adequate stimulus

A

-each type of receptor is specialized to respond to one type of stimulus

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6
Q

photoreceptors

A

responsive to visible wavelengths of light

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7
Q

mechanoreceptors

A
  • sensitive to mechanical energy

- skin, eardrum, muscles

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8
Q

thermoreceptors

A

sensitive to heat and cold

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9
Q

osmoreceptors

A

-detect changes in solute concentrations in body fluids and resultant in osmotic activity

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10
Q

chemoreceptors

A
  • sensitive to specific chemicals
  • taste and smell
  • detect O2 and CO2 in blood
  • detect chemical content of digestive tract
  • pH and the concentration of H ions
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11
Q

nociceptors

A
  • pain receptors

- sensitive to tissue damage or distortion of tissue

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12
Q

information detected by receptors

A
  • regulating motor behavior in accordance with external circumstances
  • coordinating internal activities directed at maintaining homeostasis
  • cortical arousal and consciousness
  • perceptions of the world around us
  • changing emotional states
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13
Q

receptor potentials

A
  • a graded, depolarizing receptor potential promoting net Na+ entry
  • if strong enough will generate action potentials
  • move along afferent fibers to the CNS
  • the strength of the stimulus determines the frequency of action potentials
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14
Q

receptor adaptation

A
  • may adapt slowly or rapidly to sustained stimulation

- may be tonic or phasic receptors

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15
Q

tonic receptors

A
  • do not adapt at all or adapt slowly
  • useful when it is valuable to maintain information about a stimulus
  • muscle stretch receptors
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16
Q

phasic receptors

A
  • rapidly adapting receptors

- useful when it is important to signal a change in stimulus intensity rather than delay the information

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17
Q

receptive fields

A
  • an area surrounding a receptor within which the receptor can detect stimuli
  • the acuity (to distinguish) of a body region varies inversely with the size of the receptive fields
  • smaller receptive fields show higher acuity
  • also influenced by lateral inhibition
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18
Q

hair receptor

A
  • rapidly adapting

- senses hair movement and very gentle touch

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19
Q

Merkel’s disc

A
  • slowly adapting
  • detects light
  • sustained touch and texture
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20
Q

pacinian corpuscle

A
  • rapidly adapting

- responds to vibration and deep pressure

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21
Q

ruffini endings

A
  • slowly adapting

- respond to deep, sustained pressure and stretch of the skin

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22
Q

Meissner’s corpuscle

A
  • rapidly adapting

- sensitive to light, fluttering touch

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23
Q

perception

A
  • the conscious interpretation of the external world
  • what the brain perceives from its input is an abstraction and not reality
  • the only stimuli that can be detected are those for which receptors are present
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24
Q

pain

A
  • primarily a protective mechanism to bring aware that tissue damage is occurring
  • starts with nociceptors
  • sensation of pain is accompanied by behavioral responses and emotional reactions
  • can be influenced by past or previous experiences
  • mechanical, thermal and polymodal
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25
Q

polymodal

A

-receptors respond to multiple pain stimuli

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26
Q

pain pathway

A
  • afferent pain fibers terminate in the spinal cord
  • ascending pathways that transmit the signal to the brain
  • substance P is the spinal cord pain neurotransmitter
  • descending pathways use endogenous opiates to suppress the release of substance P
  • descending pathways serve as built in analgesic system
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27
Q

afferent pain pathways

A
  • fast: myelinated, sharp, prickling pain signals

- slow carries dull, aching, persistent pain signals

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28
Q

eye

A
  • sensory organ for vision

- three layers: sclera/cornea, choroid/ciliary body/iris, retina

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29
Q

sclera

A
  • tough outer layer of connective tissue

- forms visible white part of eye

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30
Q

cornea

A
  • anterior, transparent outer layer

- light rays pass through it before entering interior of eye

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31
Q

choroid

A
  • middle layer underneath sclera, contains blood vessels that nourish retina
  • forms ciliary body and iris
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32
Q

ciliary body

A

controls lens shape

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33
Q

iris

A

controls the amount of light entering the eye

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34
Q

pupil

A
  • opening through which light enters the eye

- size is adjusted by the iris muscle

35
Q

blind spot

A

area with no rods or cones (photoreceptors)

36
Q

retina

A
  • innermost coat under choroid
  • consists of inner nervous-tissue layer and outer pigmented layer
  • rods and cones: light detecting photoreceptors in the nervous tissue layer
  • pigmented layer absorbs light after it passes by the rods and cones
37
Q

refraction of light

A
  • the bending of a light ray
  • convex: converge light rays
  • concave: diverge light rays
  • changes in different media
38
Q

cornea and lens

A
  • primary refractive structures that bend incoming light rays
  • cornea contributes most of the total refractive ability of the eye
  • strength of lens can be adjusted to accommodate for differences in near and far vision
39
Q

eye accommodation

A
  • ability to adjust strength of lens by changing its shape

- shape is regulated by ciliary muscle

40
Q

presbyopia

A

-age related reduction in accommodation ability

41
Q

myopia

A

nearsightedness

42
Q

hyperopia

A

farsightedness

43
Q

neural retina

A
  • contains 3 layers of excitable cell
  • outermost: rods and cones (absorb light)
  • middle: bipolar cells
  • inner: ganglion (axons join to form the optic nerve)
44
Q

optic disc

A
  • point of retina where the optic nerve leaves
  • called bling spot
  • no image can be detected
45
Q

fovea

A
  • small depression in center of retina
  • has only cones
  • no bipolar or ganglion cells
  • point of most distinct vision
46
Q

macula lutea

A
  • area immediately surround fovea
  • has cones, bipolar and ganglion cells
  • fairly high acuity
47
Q

photopigment

A
  • opsin: integral protein in the plasma membrane

- retinal: a derivative of vitamin A that absorbs light (carrots)

48
Q

rhodopsin

A
  • photopigment in rods
  • in the dark, inactivated, cis conformation
  • in the light, activated, trans conformation
49
Q

phototransuction

A
  • process of converting light stimuli into electrical signals
  • activation of the photopigment by light causes a receptor potential in the rod or cone which can lead to action potentials in ganglion cells
50
Q

visual pathways

A
  • right brain receives information from the left field of view of each eye and vise versa
  • cross at the optic chiasm
51
Q

ear contains three parts

A

external, middle and inner

52
Q

external and middle ear

A

-transmit and amplify airborne sound waves to the fluid filled inner ear

53
Q

inner ear

A
  • contains neural receptors cells for 2 sensory systems:
  • cochlea: hearing
  • vestibular: apparatus for equilibrium
54
Q

sound waves

A

-traveling vibration of the air

55
Q

pitch or tone

A

-determined by the frequency of vibrations

56
Q

intensity or loudness

A

-depends on the amplitude of the sound waves

57
Q

hearing involves two aspects:

A
  • identification of the sound, “what”

- localization of the sounds “where”

58
Q

timbre or quality

A
  • depends on the overtones

- additional frequencies superimposed on the fundamental pitch/tone

59
Q

sound transduction

A
  1. waves enter through the external ear
  2. tympanic membrane vibrates with sound waves
  3. middle ear converts tympanic membrane vibrations into fluid movements in cochlea
  4. the organ of corti (sense organ for hearing) rests on the basilar membrane in cochlea
  5. movement of fluid in inner ear causes the basilar membrane to vibrate
  6. cilia on hairs are bent
  7. the bending of cilia transduces sound waves into electrical signals
60
Q

role of stereocilia in transduction

A
  1. tips link stretch and open channels when the stereocilia bend towards the tallest member
  2. more K+ enters
  3. cell depolarizes
  4. opens Ca2+ voltage gated channels
  5. Ca2+ entry cause a greater release of the neurotransmitter
  6. more transmitters leads to a higher rate of action potentials
61
Q

pitch discrimination

A

-depends on region of the basilar membrane that vibrates

62
Q

loudness discrimination

A

-depends on the amplitude of vibration of the basilar membrane

63
Q

auditory cortex

A
  • primary: in the temporal lobe, tonotopically organized
  • each region of the basilar membrane is connected to a specific region
  • specific cortical neurons are activated only by particular tones
  • higher-order auditory cortex- integrates the separate sounds into a meaningful pattern
64
Q

vestibular apparatus

A

-consists of semicircular canals and otolith organs

65
Q

equilibrium

A

-sense of body orientation and motion

66
Q

semicircular canals

A

-detect rotational or angular acceleration or deceleration of the head

67
Q

otolith organs

A
  • detect changes in the rate of linear movement

- provide info about head position relative to gravity

68
Q

production of receptor potential in hair cells

A
  • hair depolarizes when stereocilia are bent towards the kinocilium
  • hair hyperpolarizes when stereocilia are bent away from kinocilium
69
Q

equilibrium transduction

A
  • neural signals are generated as fluid moves within vestibular sense organs
  • mechanical deformation of hair cells occurs in response
  • the bending either depolarizes or hyperpolarizes receptor potentials
70
Q

otoliths

A
  • crystals of CaCO3

- calcium carbonate

71
Q

vestibular projections

A
  • signals from the vestibular apparatus are carried through the vestibulocochlear nerve to the vestibular neclei
  • maintains balance, posture, eye movement, perceiving motion and orientation
72
Q

chemoreceptors

A

-detect taste and smell

73
Q

taste receptors

A

-found in taste buds on tongue

74
Q

olfactory receptors

A

-located in the olfactory epithelium in the nasal cavity

75
Q

taste and smell senses

A
  • dissolved molecules bind to site on the receptor membrane
  • binding causes receptor molecules which lead to action potentials
  • continuously renewed
  • route 1: to cortex for conscious perception
  • route 2: limbic system for emotional and behavioral processing
76
Q

taste bud

A
  • small opening: taste pore

- fluid in mouth enter pore and come into contact with receptor cell

77
Q

taste receptor cells

A

-modified epithelial cells with microvilli

78
Q

tastants

A
  • plasma membrane of microvilli contains receptors for specific chemical signals
  • binding causes receptor to induce electrical signals in cell
79
Q

primary tastes

A
  • salt: chemical salts
  • sour: acids
  • sweet: configuration of glucose
  • bitter: diverse group of tastants
  • umami: savory taste triggered by animo acids
80
Q

olfactory mucosa 3 cells

A
  • olfactory receptor neurons
  • supporting cells
  • basal cells
81
Q

olfactory receptor neurons

A
  • primary sensory neuron
  • dendrite exposed at surface of mucosa
  • dendrite contains cilia where odorant molecules bind
  • axons of receptors cells collectively form olfactory nerve
82
Q

supporting cells (olfactory)

A

-secrete mucus to help odorant molecules interact with receptor sites

83
Q

basal cells (olfactory)

A
  • precursors of new olfactory receptor cells

- as olfactory nerves degenerate, basal cells divide to give rise to new receptor cells

84
Q

olfactory bulb

A
  • axons from the olfactory neurons
  • synapse onto mitral cells (output cells of bulb)
  • synapse takes place in the glomerulus
  • axons from the mitral cells from the olfactory tract and project to the limbic system and cerebral cortex

Physiology (13 decks)

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