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Physio > Pt6 Sensory System I > Flashcards

Pt6 Sensory System I Flashcards

1
Q

What are the 6 sensory pathways?

A
  1. Sensory reception
  2. Transduction
  3. Amplification/adaptation
  4. Transmission
  5. Integration
  6. Perception
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2
Q

What is the general functional organization of the nervous system?

A

PNS = sensory & motor input (to environment internal/external)
CNS = integration (unconscious/conscious)

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3
Q

What is the hierarchical organization in the nervous system?

A

(LOW to HIGH)
1. Receptors distributed with axons projecting via cranial & spinal nerves into CNS.
2. Fibers connect w local circuit for reflex functions (dont need CC for reflexes) or travel cranially to synapse in brain. brainstem, cerebellum, thalamus, CC
3. Primary receiving areas: auditory, sensory, visual, olfactory
4. Association areas integrate input & connect with motor areas via interneurons (takes into account previous experiences) to plan a response.

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4
Q

Describe sensory receptors.

A

-present in every tissue
-sensory info acquired at terminal end of spinal & cranial sensory nerve fibers & conveyed to CNS
-conscious: pain, touch, temp, bladder
-unconscious: BP, O2/CO2 levels

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5
Q

What are somatosensory signals?

A

-originate from cutaneous areas: muscle & joints
-respond to mechanical/chemical/thermal stimuli
-produce sensation of: pain, pressure/vibration, touch, temp
-vision & hearing = somatic special

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6
Q

What are viscerosensory signals?

A

-originate from internal structures
-some signals are conscious (ex. Bladder, full stomach)
-taste & gustation = visceral special

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7
Q

What is the “labeled line” principle?

A

-nerve fibers transmitting only ONE modality of sensation
-when a sensory fiber is stimulated the perception is related w the type of fiber regardless of the type of stimulus excites it
EX:
~stimulus = overheating, electricity, crushing, damage to fiber
~Perception = pain
EX:
Pain receptors dont respond to normal touch/pressure, only active when stimuli is severe to damage tissue

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8
Q

What is a sensory receptor?

A

-nerve ending, a cell or group of cells, or sense organ
-when stimulated = produces afferent/sensory impulse

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9
Q

What are the 3 sensory receptors?

A
  1. Simple receptors
    -free nerve endings
    -not myelinated
    -common
  2. Complex receptors
    -sheathed by CT capsule (enclosed nerve ending)
    -encapsulated portions of axon are not myelinated
  3. Special senses receptors
    -specialized receptor cells (ex. Hair cell)
    -sensory ganglion
    -myelinated
    -synaptic vesicle
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10
Q

What are mechanoreceptors?

A

Receptors for:
1. Skin tactile sensibilities: (dermis & epidermis)
-free nerve ending (pain, heat, temp)
-merkles discs (touch)
-Ruffinis endings (pressure)
-meissners corpuscules (touch)
-Krauses corpuscules
-hair end organs (touch)
2. Deep tissue sensibilities
-ruffinis endings
-pacinian corpuscles (strong pressure)
-muscle spindles
-golgi tendon receptors
3. Hearing
-sound receptors of cochlea
4. Equilibrium/balance
-vestibular receptors
5. Arterial receptors
-baroreceptors of carotid sinuses and aorta

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11
Q

What are muscle spindles?

A

-encapsulated group of 3-12 skeletal muscle fibers (receptors)
-contractile elements = restricted to the ends
>none in middle (lacks myofibrils)
>affect sensitivity for transducing muscle stretch
>contractile part = innervated by gamma motor neurons (give rise to Type A gamma fibers)
» gamma motor neurons from CNS innervate intrafusal fibers to CNS
-middle part innervated by sensory neurons and carry AP from spindle to the CNS

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12
Q

Describe muscle spindle structure.

A

-buried in extrafusal fibers of muscle = contractile fibers
-sends info about muscle stretch to CNS
-golgi tendon organ links muscle & tendon
-intrafusal fibers found in muscle fibers

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13
Q

What is the function of muscle spindles?

A

-stretch receptors = to correct changes in muscle length
-stretching middle segment of intrafusal muscle fiber = generates AP along spindle sensory neurons
>stretch ion channels open
>leads to membrane depol & AP gen
>muscle contraction

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14
Q

What are the 5 steps for the muscle stretch reflex?

A
  1. Stretching of muscles stimulates muscle spindles
  2. Activation of sensory neurons
  3. Info processing at motor neuron
  4. Activation of motor neuron
  5. Contraction of muscle
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15
Q

Describe the gamma and alpha motor neurons?

A

-muscle spindle participates in sensory & motor function
-co-activation of alpha & gamma neurons = allow brain to test whether the amount of contraction intended by the brain was what actually occurred
-alpha = extrafusal
-gamma = infrafusal

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16
Q

What is the golgi tendon organ?

A

-helps control muscle tension
-encapsulated sensory receptor = muscle tendon fibers pass
>10-15 muscle fibers connected to each golgi
-stimulated when small bundle of muscle fibers are tensed by contraction

17
Q

What’s the difference between muscle spindle & the golgi tendon organ?

A

MUSCLE SPINDLE:
-detects muscle length & changes in muscle length
GOGLI TENDON ORGAN:
-detects muscle tension reflected by the tension in itself

18
Q

What is the golgi tendons role in the nervous system?

A

-provides nervous system w info on the degree of tension
-signals conducted through sensory nerve fibers
>excite inhibitory interneurons in spinal cord
>inhibit alpha motor neuron activity
>causes muscle relaxation
prevents excessive tension on muscle

19
Q

What are the 5 sensory receptors?

A
  1. Mechanoreceptors
  2. Thermoreceptors
  3. Nociceptors
  4. Photoreceptors
  5. Chemoreceptors
20
Q

Describe thermoreceptors.

A

-temp
-warm/cold receptors
-free nerve ending receptors

21
Q

Describe nociceptors.

A

-pain
-free nerve endings

22
Q

Describe photoreceptors.

A

-vision
-rods & cones

23
Q

Describe chemoreceptors.

A

Receptors for:
-taste = taste bud receptors
-smell = receptors of olfactory epithelium
-arterial oxygen = receptors of aortic & carotid sinus
-osmolality = neurons in/near supraortic nuclei
-blood CO2 = surface of medulla & in aortic & carotid bodies
-blood glucose, AA, FA = receptors in hypothalamus

24
Q

Describe the transduction of receptor stimulus.

A

-the type of stimulus that excites the receptor = change the membrane electrical potential
-change = receptor potential or generator potential
-4 ways to stimulate a receptor potential

25
Q

What are the 4 ways to stimulate a receptor potential?

A
  1. Mechanical deformation
  2. Application of a chemical to the membrane
  3. Change of temp of membrane
  4. Effects of electromagnetic radiation
    >light on a retinal visual receptor

all are related with changes in membrane permeability = allows ions to diffuse more/less
stimulation change resting membrane potential
Ex. Pacinian corpuscle = onion like structure in dermis & hypodermis

26
Q

What is the relationship between receptor potential & action potentials (amplification).

A

-more receptor potential rises above threshold level = greater becomes the action potential freq.
-more intense stimulus = greater the # of receptors stimulated

27
Q

Describe the adaptation of receptors.

A

-can adapt either partially/completely to constant stimulus
-continuous sensory stimulus = receptor responds at a high impulse rate at first & then at a slower rate
-rate of AP decrease to few or none
-diminish extent of their depol despite sustained stimulus strength

28
Q

Describe slow adapting receptors.

A

“Tonic receptors”
-transmit impulses to brain as long as stimulus is present
EX: baroreceptors & chemoreceptors
pain never adapts

29
Q

Describe fast adapting receptors.

A

“Phasic receptors”
-stimulated when stimulus strength changes
EX: pacinian corpuscle

30
Q

Describe stimulus perception in the dog.

A

-detect diff modalities of stimulus & know location of stimulus applied to the body
-segments of spinal cord innervates a receptive field of body
>dermatoma
-trigeminal nerve (CN V) fibers have receptive fields on the face

areas of skin innervated by cutaneous branches from a single spinal nerve = “dermatome”
cutaneous areas supplied by adjacent spinal nerve overlap

31
Q

The precision of stimulus location is acuity and depends on:

A

receptive fields of afferent neurons (tactile sensations in skin) code for stimulus location
-size & # receptive fields = smaller the receptive field the greater the acuity
>lips and fingertips have better acuity than back & shoulder bc of ability to perceive 2 fine points presses against skin as two points & not one (two-point distribution)
-lateral inhibition = occurs when a strong stimulus applied to receptive field of one neuron = neuron inhibits transmission of signals by neurons w neighboring receptive fields
>increases acuity bc it increases contrast of signals in NS

Physio (35 decks)

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