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HN220 > Chapter 10: Sensory Physiology > Flashcards

Chapter 10: Sensory Physiology Flashcards

Sensory, Reflexes, ANS, PNS

1
Q

what is sensory physiology?

A
  • the afferent branch of peripheral nervous system
  • transmits information from the periphery to the central nervous system
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2
Q

2 classes of receptors in sensory physiology

A

1) sensory receptors = detect stimuli in the external environment
2) visceral receptors = detect stimuli that arise within the body

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3
Q

what are visceral afferent neurons?

A

a class of afferent neurons that transmit information to the CNS from stimulus occurring inside the body

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4
Q

what is perception?

A

the conscious interpretation of the world based on
sensory systems, memory, and other neural processes

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5
Q

what is the somatosensory system?

A
  • part of the sensory system concerned with the conscious perception of touch, pressure, pain, temperature, position, movement
  • necessary for perception of sensations associated with skin and position of the limbs and the body
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6
Q

what is somesthetic sensations?

A

sensations that arise from receptors in the skin

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7
Q

what is proprioception?

A

perception of the position of the limb and body

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8
Q

what are special senses?

A

are necessary for:
- vision
- smell
- taste
- hearing
- equilibrium/balance

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9
Q

what are sensory receptors?

A

specialized structures detect a specific form of energy in the external environment

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10
Q

what modalities can be detected from sensory receptors?

A
  • light waves
  • sound waves
  • pressure
  • temperature
  • chemicals
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11
Q

what is the law of specific nerve energies?

A

states that a given sensory receptor is specific for a particular modality

–> this means cells in the eye called photoreceptors detect light waves, but not sound waves

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12
Q

what is the adequate stimulus?

A

refers to the idea that a sensory receptor is adapted to respond best to a certain modality/stimulus

i.e photoreceptors can respond to visible light

–> modalities other than the adequate stimulus may activate the sensory receptor BUT only at higher energy levels

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13
Q

5 types of sensory receptors in somatosensory system

A
  • photoreceptors (light)
  • chemoreceptors (taste and smell)
  • thermoreceptors (temperature)
  • mechanoreceptors (touch and pressure)
  • nocireceptors (pain)
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14
Q

what is the function of sensory receptors?

A

sensory transduction!
–> they convert the energy of a sensory stimulus into changes in membrane potential (called receptor potential)
–> converts from one energy type to another (electrcial)
–> activation of these receptors by stimuli causes graded potentials triggering nerve impulses along the afferent PNS fibers reaching the CNS.

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15
Q

what is sensory transduction?

A
  • is the conversion of stimulus energy into electrical energy
  • sensory receptors convert the energy of a sensory stimulus into changes in membrane potential called receptor potentials/ generator ­potentials
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16
Q

what are receptor potentials?

A
  • are graded potentials (magnitude varies with strength of a stimulus) resulting from changes in membrane potential
  • receptor potentials are caused by the opening or closing of ion channels in response to sensory receptors detecting a sensory stimulus in the external environment
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17
Q

how do sensory receptors perform their function?

A

when a sensory receptor is exposed to a specific stimulus (i.e light), the receptor cell is activated
- this leads to changes in the permeability of its membrane to ions, so ion channels may open or close.
- as a result, the flow of ions across the membrane changes and alters the membrane potential of the receptor cell
- receptor potentials are graded. this means the magnitude of depolarization depends on intensity of the stimulus
–> A stronger stimulus leads to a larger receptor potential (more depolarization)
–> A weaker stimulus results in a smaller receptor potential (less depolarization)
- if the receptor potential exceeds threshold, it can
generate an action potential
- the action potential is a rapid and all-or-nothing electrical signal that is propagated to the CNS (brain or spinal cord)
- the electrical signals are then processed and interpreted, leading to the perception of the original stimulus.

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18
Q

how are post-synaptic potentials different from receptor potentials?

A
  • postsynaptic potentials are triggered by the binding of neurotransmitter to receptors
  • receptor potentials are triggered by sensory stimuli
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19
Q

two basic forms of sensory receptors

A

1) the sensory receptor exists as a specialized structure at the peripheral end of an afferent neuron
–> if the receptor is depolarized to threshold, an action potential is generated in the afferent neuron and propagated to the CNS

2) the sensory receptor is a separate cell that communicates through a synapse with an associated afferent neuron
–> a change in the receptor’s cell membrane potential via calcium channel causes the release of a neurotransmitter (big stimuli = more released)
–> the transmitter binds to the receptors on the afferent neuron and causes a change in membrane potential of that cell, causing depolarization to threshold and generation of an action potential which is transmitted to CNS

20
Q

what is receptor adaptation? what happens?

A
  • is a decrease in the magnitude of the receptor potential when a stimulus is constant

–> results in decrease in frequency of action potentials = perception of the stimulus decreases

21
Q

what are slowly adapting/tonic receptors?

A
  • show little adaptation
  • the receptors keep firing as long as the stimulus is present but the firing rate decreases over time.
22
Q

what are rapidly adapting/phasic receptors

A
  • adapt quickly
  • they respond respond maximally at the onset of a stimulus but then adapt briefly after
  • their response decreases if the stimulus is maintained
23
Q

what are sensory pathways?

A
  • a chain of neurons, from receptor organ to cerebral cortex, that are responsible for relaying information for the perception of sensations
24
Q

what are labeled lines in sensory pathways?

A
  • a specific neural pathways that transmits information of a specific particular modality (i.e light, temperature)
  • each sensory modality follows its own labeled line
25
Q

what is a sensory unit?

A
  • a single afferent neuron and all the receptors associated with it
  • all the receptors are of the same type
  • an action potential may occur in the afferent neuron if any of the associated sensory receptors are triggered
26
Q

what is a receptive field?

A
  • the region containing receptors on an afferent neuron in which a stimulus can produce a response (excitatory or inhibitory)
27
Q

what is the sensory transduction mechanism for somatic senses?

A
  • sensory transduction begins with sensory receptors such as photo, mechano, therom, nociceptors
    –> each sensory receptor has an adequate stimulus which is the specific modality they are designed to respond to
  • when the adequate stimulus is applied to a sensory receptor, it activates the receptor, leading to depolarization of the cell and graded receptor potential.
  • if the receptor potential exceeds threshold based on the strength of the stimulus, it can generate an action potential
  • the action potentials travel along sensory (afferent) neurons to reach the brain or spinal cord (CNS)
  • once the sensory signals reach the central nervous system, they are processed and interpreted in various regions of the brain
  • each modality follows their own labeled line (a neural pathway) to the be perceived
28
Q

what are the 3 orders of neurons?

A

first order = directly receive input from sensory receptors and carry signals from the periphery to the spinal cord
second order = carry signals from the spinal cord to the thalamus (a relay station)
third order = carry signals from the thalamus to the cerebral cortex, where sensory perception occurs

29
Q

what is sensory coding?

A

the process of how sensory stimuli are translated and read by the brain so it can interpreted and perceived.

30
Q

what are the 3 components of sensory coding?

A
  • the type of stimulus
  • the location of the stimulus in the receptive field
  • the relative intensity of the stimulus
31
Q

what is coding for stimulus type?

A

the stimulus type is identified by the particular receptor and pathway that is activated when the stimulus is applied

–> Each sensory modality (i.e vision) has specific receptors and neural pathways dedicated to processing and coding information related to it

i.e light waves activate photoreceptors which communicate via a specific pathway to the visual cortex

32
Q

what is coding for stimulus intensity?

A

the intensity of the stimulus is coded/identified by the frequency of action potentials (frequency coding) and the number of receptors activated (population coding)

–> it’s how the body determines if a stimulus is strong or weak, loud or soft, bright or dim, etc.
–> allows you to differentiate the stregnth of a stimulus

33
Q

what is frequency coding?

A
  • a stronger stimulus results in a larger receptor potential = exceed threshold = stronger depolarization to overcome relative refractory period = generate a second action potential
    –> therefore, as the intensity of a stimulus increases, the frequency of action potentials increases
34
Q

what is population coding?

A
  • a stronger stimulus may activates/recruits a greater number of receptors
  • more receptors that are activated = more receptor potentials that are generated = frequency of action potentials sum and cause a stronger signal being transmitted to the CNS for perception
35
Q

what is coding for stimulus location?

A
  • the coding of where a stimulus is located in the external environment is based on a sensory units receptive fields
  • includes the size of the receptive fields (small or big) and degree of overlap (over the same area) = affects 2 point discrimmination
36
Q

what is acuity?

A

the ability of a sensory systems to distinguish fine details and precision in the perception of stimuli.

37
Q

what is lateral inhibition?

A
  • refers to when a stimulus that strongly excites receptors in a given location inhibits activity in the afferent pathways of other nearby receptors
38
Q

what is the purpose of lateral inhibition?

A
  • increases acuity (preciseness of stimuli)
    –> this occurs because it increases the contrast of signals in the nervous system
    –> this means it allows the transmission of strong signals in some neurons BUT suppresses the transmission of weaker signals arising in nearby neurons
39
Q

what is two-point discrimmination?

A
  • the ability of a person to perceive two fine points pressed against the skin as two distinct points
  • only occurs if the two points are applied to the receptive field of two different afferent neurons
    –> the minimum distance that exists to be perceived as two separate points is called the two-point discrimination threshold
  • if the two points are closer together than the threshold, then it will be perceived as a single point
  • the smaller the receptive field, the greater ability to discriminate the two points
40
Q

what is pain perception?

A

is the sensation produced by potentially tissue-damaging stimulus

41
Q

what does perception of pain depend on?

A
  • depends on your past experiences and the circumstances under which the stimulus was applied

–> i.e tooth ache during a busy day at work is less noticeable than when trying to fall asleep at night

42
Q

what is fast and slow pain?

A

fast = sharp sensation that is easily localized
slow = dull ache that is poorly localized

43
Q

what is visceral pain?

A

is pained that originates in internal organs, and not limited to just the body surface

44
Q

what is referred pain?

A
  • when a sensation is “referred” to a body surface
  • you may have hurt one area of your body but feel pain somewhere else
45
Q

what is the gate control theory?

A

suggests that the spinal cord has a neurological ‘gate’ that controls pain signals to the brain

–> if certain interneurons are active, then transmission of pain signals can be suppressed and the perception of pain is lessened

HN220 (12 decks)

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