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BIO108- GENERAL PHYSIOLOGY > LECTURE 7: SENSING THE ENVIRONMENT > Flashcards

LECTURE 7: SENSING THE ENVIRONMENT Flashcards

1
Q

provide the only channels of communication
from the external world to the nervous system

A

sensory organs

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2
Q

gathered from the environment and from within the body and processed by the nervous system

A

Sensory input

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2
Q

Basic Concepts in Sensory Physiology: Information is conveyed in sensory nerves as ______________.

A

action potential

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2
Q

-cells specialized to convert stimulus energy into neural signals
-housed or clustered together in sense organs (where sensory reception begins

A

Sensory receptors

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3
Q

Basic Concepts in Sensory Physiology: Sensory organs serve as ________ where external signals generate receptor potentials

A

transducers

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3
Q

organs containing
cells (receptor cells) that are specialized to
respond to particular kinds of stimuli

A

Sensory reception

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3
Q

Basic Concepts in Sensory Physiology: Action potentials in all sensory nerves are of the __________ and __________-

A

same nature and magnitude

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3
Q

Basic Concepts in Sensory Physiology: The magnitude of the action potential is unaffected by _______________

A

stimulus intensity

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4
Q

Basic Concepts in Sensory Physiology: Stimulus intensity is coded by _______________ of the action potential

A

frequency modulation

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5
Q

positioned in many
locations (surface of inside)constitute the
first step in gathering sensory information

A

Sensory organs

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6
Q

carry information
from periphery to CNS

A

Afferent neurons

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6
Q

Receptor class that is sensitive to mechanical energy

A

mechanoreceptor

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6
Q

Receptor class that is sensitive to chemical energy

A

chemoreceptor

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6
Q

carry information
away from the CN

A

Efferent neuron

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6
Q

Receptor class that is sensitive to electrical energy

A

electroreceptor

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6
Q

Receptor class that is sensitive to thermal energy

A

thermoreceptor

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6
Q

Receptor class that is sensitive to light energy

A

photoreceptor

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6
Q

features that characterize stimuli within a
particular modality

A

Qualities

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6
Q

ability to modify the conformation of a
receptor molecule

A

Stimulus

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6
Q

respond to signals from
within the body and communicate this information to
the brain by pathways that typically are not brought into
consciousness

A

Interoceptive receptors

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7
Q

Properties of Receptor Cells

A
  1. Highly selective for a specific kind
    of energy (membranes respond
    differentially to different types of
    energy)
  2. Exquisitely sensitive to their
    selected stimuli because they can
    amplify the signal that is being
    received
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8
Q

form of energy to
which a sensory receptor is most sensitive

A

Sensory modality

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8
Q

Molecules of _____________ (cell membrane of photoreceptor cell ) absorb photons, capturing their energy.

A

rhodopsin

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8
Q

Properties of Receptor Cells: form of energy to
which a sensory receptor is most sensitive

A

Sensory modality

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8
Q

Properties of Receptor Cells: Receptor cells _________ the sensory input
(change the stimulus energy into the
energy of a nerve impulse)

A

transduce

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8
Q

Properties of Receptor Cell: transduction depends on a_____________ in particular receptor molecules
(proteins)

A

conformational change

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8
Q

produces a transient structural change that
activates a cascade of associated molecules

A

Photon

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8
Q

Sensory transduction processes:

A
  1. Absorption of stimulus energy
  2. Transduction proper
  3. Amplification of output energy
  4. Integration and Conduction of output potential
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8
Q

The basic events in a receptor cell:

A

o detection
o amplification
o encoding of the sensory stimulus

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8
Q

Basic events in a receptor cell

A
  1. Detection
  2. Amplification
  3. Encoding
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8
Q
  • threshold of detection - smallest amount of stimulus energy that will produce a response in a receptor 50% of the time
  • time constant of sensory reception -receptors must be able to respond quickly and repeatedly (for a sensory system to convey accurate information about rapidly changing stimuli)
    *receptors must be interconnected - allows the
    population of receptors to extract information
    about very rapid events on the basis of their collective
    activity
A

Detection

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8
Q

smallest amount of stimulus
energy that will produce a response in a receptor 50% of
the time

A

threshold of detection

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8
Q

receptors must be able to respond quickly and repeatedly (for a sensory system to convey accurate information
about rapidly changing stimuli)

A

time constant of sensory reception

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9
Q

allows the population of receptors to extract information about very rapid events on the basis of their collective activity

A

receptors must be interconnected

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10
Q

*sensory signals occurs within the receptor cells
* mediated by different intracellular mechanisms
* occurs at the same time that noise is suppressed, so the signal-to-noise ratio improves in the process.

A

Amplification

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11
Q

_______ is captured by a visual pigment molecule

A

photon

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12
Q

Capturing of photon by visual pigment molecule activates __________

A

transducin (GTP-binding protein, or G
protein)

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12
Q

activates a phosphodiesterase to
hydrolyze cyclic guanosine monophosphate A
(cGMP)

A

Transducin

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13
Q
  • sensory information into a neuronal signal to be transmitted to the brain depends on changes in the conductance through membrane ion channels
    *channel conductance changes - shift the probability that the neuron will produce an AP
A

Encoding

14
Q

Characteristics of Receptor Potential

A
  1. An adequate stimulus elicits a graded RP, the amplitude of which is a function of stimulus intensity.
  2. The frequency of resultant AP in a receptor is a coded representation of the intensity of the adequate stimulus.
14
Q

Types of Sensory receptors

A
  1. Phasic receptor
  2. Tonic receptors
15
Q

The graded depolarization of a receptor in response to stimulation

A

Receptor potential

16
Q

-produces APs during only part of the
stimulation ( onset or at the
offset of the stimulus -cannot
by itself convey information
about the duration of the
stimulus)
-adapt more rapidly and cease impulse discharge even during a prolonged stimulus.

A

Phasic receptor

17
Q

-continue to fire APs throughout the
stimulation (can directly
convey information about the
duration of the stimulus
-adapt relatively slowly and continue to discharge impulses throughout duration of prolonged stimulus.

A

Tonic receptors

17
Q

Steps link the onset of a stimulus to the production of APs in a
sensory pathway

A

*receptor cells (RC) generate and carry APs into the CNS
* RC synaptically modulate APs in other neurons that carry the
signal into the CNS

17
Q

The decrease in the response of a receptor to a steadily maintained stimulus over time

A

Receptor Adaptation

17
Q

Stages from stimulus to output where
adaptation can take place:

A
  1. Mechanical properties of the receptor cell -
    act as a filter that preferentially passes
    transient, rather than sustained, stimuli.
  2. The transducer molecules “run down” during
    a constant stimulus.
  3. Enzyme cascade activated by a transducer
    molecule may be inhibited by the accumulation
    of a product or an intermediate substance.
  4. Electrical properties of the receptor cell may
    change in the course of sustained stimulation.
  5. Membrane of the spike-initiating zone
    may become less excitable during
    sustained stimuli.
  6. Sensory adaptation can also take place
    in higher-order cells in the CNS
17
Q

o pressure and vibration receptor found in the skin, muscles, mesentery, tendons, and joints of mammals
o region of receptor membrane -sensitive to mechanical stimuli (surrounded by concentric
lamellae of connective tissue)
o something presses on the corpuscle (deforming it) -disturbance is transmitted
mechanically through the layers to the sensitive membrane of the receptor neuron

A

Pacinian corpuscle

17
Q

adapts
quickly to constant
stretch, producing only a
short train of impulses

A

Phasic receptor

17
Q

fires
steadily during
maintained stretch but
frequency decreases

A

Tonic receptor

17
Q

transducing photons of light into
electrical signals that can be interpreted by the nervous
system, and photoreceptive organs (eyes)

A

Photoreception

17
Q

*Adaptation in the Pacinian corpuscle depends on the ______________________________________-

A

mechanical properties of accessory structures

17
Q

based upon a very highly conserved
set of protein molecules that provide an optical pathway
leading light to the photo-receptive surface and that
capture photons within the photoreceptors

A

visual transduction

17
Q

o protein visual pigment molecules
o each molecule - seven transmembrane domains
o coupled to photopigment molecules, which are structurally altered by the absorption of photons and which in turn modify the properties of the opsin protein

A

opsins

17
Q

-few receptors in an
open cup of screening pigment
cells
- surrounding distribution of
light and dark, but they do not
provide enough information to
allow detection of either predators
or prey

A

eyespots

17
Q

o spherical lens in aquatic animals
o provides the high refractive
power needed to focus images
under water (spherical aberration)
o lens is not homogeneous (dense
with a high refractive index in the
center and has a gradient of
decreasing density and refractive
index toward the periphery.

A

single-chambered eye

17
Q

reducing the size of
the aperture to produce a pinhole
eye (B)

A

simplest eyes

17
Q

three lenses in series
that together correct for
spherical aberration (D)

A

eye with multiple lenses

18
Q

o combines small aperture
with a refractile lens
o very high quality image
that is focused on the layer
of photoreceptors in the
retina

A

vertebrate eye (E)

19
Q

Main parts of the vertebrate eye

A

-sclera
-choroid
-retina
-lens
-iris
-optic disk

19
Q

white outer layer, including cornea

A

sclera

19
Q

pigmented layer

A

choroid

20
Q

regulates the size of the pupil

A

iris

21
Q

2 cavities of the eye

A

-Anterior cavity
-Posterior cavity

21
Q

focuses light on the retina

A

lens

21
Q

a blind spot in the retina where the
optic nerve attaches to the eye

A

optic disk

21
Q

contains photoreceptors

A

retina

22
Q

filled with watery aqueous humor

A

anterior cavity

22
Q

filled with jellylike vitreous humor

A

posterior cavity

22
Q

The ___________ produces the aqueous humor

A

ciliary body

22
Q

In mammals
accommodation is
accomplished by
_______________________

A

changing the shape of the lens

23
Q

____________________ is the
focusing of light in the
retina.

A

Accommodation

24
Q

two types of photoreceptors

A
  • Rods
  • Cones
25
Q

light-sensitive but don’t distinguish colors

A

Rods

26
Q

distinguish colors but are not as sensitive to
light

A

Cones

26
Q

In humans, cones are concentrated in the ______

A

fovea

26
Q

What is Fovea?

A

the center of the visual field

27
Q

is the visual pigment of rods.

A

Rhodopsin (retinal + opsin)

27
Q

rods are more concentrated around the ________________

A

periphery of the retina

28
Q

The absorption of light by rhodopsin initiates a __________________________-

A

signal-transduction pathway

29
Q

Visual processing begins with
rods and cones synapsing with
_______________

A

bipolar cells

29
Q

Bipolar cells synapse with
________________

A

ganglion cells

29
Q

Visual processing in the retina
also involves ___________ and ___________

A

horizontal cells
and amacrine cells

29
Q

Vertical pathway of Visual processing

A

photoreceptors → bipolar cells → ganglion
cells axons

29
Q

Lateral pathways of visual processing

A

Photoreceptors → horizontal cells → other
photoreceptors

29
Q

result to more distance photoreceptors and bipolar
cells are inhibited → sharpens edges and
enhances contrast in the image.

A

Lateral Inhibition

30
Q

Pathway that is a results in lateral inhibition, this time of the ganglion cells

A

Photoreceptors → bipolar cells → amacrine
cells → ganglion cells

30
Q

Stages of the vertebrate eye

A
  1. Initial stage
  2. Further bent or refracted as they pass through the lens and finally form an inverted image on the rear internal surface of the eye (retina)
30
Q

incident light rays are bent as they pass
through the clear outer surface of the eye (cornea)

A

Initial stage

30
Q

incident light is refracted by the cornea and the lens and is focused
on the _________________

A

photosensitive retina

31
Q

image focused on the retina is inverted by the lens. The lens is held in place by the ______________

A

zonularfibers

31
Q

image is focused - changing the curvature and thickness of the lens –changes the distance at which an image passed through the
lens comes into focus (_________________)

A

focal length of the lens

32
Q

When ciliary muscle fibers contract, tension on the zonular fibers is __________, and the elastic properties of the lens cause it to become
more ______________, shortening the focal length.

A

-reduced
-rounded

32
Q

modification of the tension
exerted on the perimeter of the lens is caused by

A

shape of the lens is changed

33
Q

lens is held in place within the eye by the radially oriented fibers
of the _________

A

zonula

BIO108- GENERAL PHYSIOLOGY (10 decks)

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