Receptors

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  • Created by: Hindleyc
  • Created on: 27-01-19 10:46
What do receptors do
Respond only to specific stimuli
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What does each receptor do
Initiates nerve impulse in sensory neurone when it is physically deformed by an outside force
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Examples
Touch, pressure, stretching, sound waves, motion
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What do mecho receptors allow
enable us to detect touch, monitor position of our muscles bones and joints and give sense of proprioception , detects sounds and the motion of the body
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What is light touch detected by
Receptors in the skin often found close to hair follicle so even if skin isn't touched directly movement of the hair is detected
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Steps in the mouse light movement of hair
triggers a generator potential in mechanically -gated sodium channels in a neurone located next to the hair follicle
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What does this potential open
voltage-gated sodium channels and if it reaches threshold triggers an action potential in the neurone
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What aren't touch receptors
distributed evenly over the body- more in fingertips and tongue than back of hand
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Whats used
2 point threshold test- with pair of dividers determine minimum separation of the points that provides 2 separate touch sensations
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What is the ability to discriminate the 2 points
better on fingertips than small of back
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What is the density of touch receptors also reflected in the amount of
somatosensory cortex in the brain assigned to that region of the body
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What is proprioception
our body sense
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What does it enable
us to unconsciously monitor the position of our body
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What does it depend on
receptors in the muscles, tendons and joints
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Stimulation of a receptor lead to
the establishment of a generator potential
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Example of mechanical receptor
the pacinian corpuscle
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What do they have
Stretch mediated Na+ channels
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What does deforming the corpuscle create
a generator potential in the sensory neurone arising within it
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What type of response is this
graded
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The greater the deformation ..
the greater the the generator potential
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If the gp reaches a threshold
a volley of AP (also called nerve impulses) are triggered at the first node of ranvier of the sensory neurone
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So the stimulus is detected by
receptor cell
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What is there sometimes no
interneuron- one way
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What does it cause
Receptor to generate an AP
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What are pacinian corpuscles
Pressure receptors
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Where are they located
In the skin and also in various internal organs
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What Is each connected to
a sensory neuron
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What are they
Fast connecting, bulb-shaped receptors located deep in the dermis
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What does it consist of
The ending of a single neurone surrounded by lamellae
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What is it the largest of
the skins receptors and beloved to provide instant information about how and where we move- also sensitive to vibration
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Where are they also located
in joints and tendons and in the tissue that lines organs and blood vessels
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what is potential difference
All cells have a difference in electrical charge across a plasma membrane
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Resting potential
-70 caused by distribution of K+ and Na+, said to be polarised
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What an Action potential (nerve impulse)
Occurs when potential difference across an axon is temporarily reversed (inside +ve)
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What happens
-70 to +35, membrane depolarised ready to send impulse when potential difference change allow Na+ to diffuse by facilitated diffusion
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Pressure on the skin changes the shape of the PC
This changes the shape of the pressure sensitive sodium channels in the membrane, making them open
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Then what does Na+ do
Diffuse in through the channel leading to depolarisation called a generator potential
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Greater the pressure..
The more sodium channels open and the larger the generator potential
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If a threshhold value is reached
an action potential occurs and the nerve impulse travels along the sensory neurone
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Frequency of the impulse is related to
the intensity of the stimulus
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Structure of a pacinian corpuscle
Single nerve fibre in a capsule and nerve fibre surrounded by a myelin sheath
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What is it separated by
Gel
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how
pressures on layers of connective tissue around tip of sensory neurone Na floods in causing Action potential
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What does voltage gated mean
Depends on the voltage across membrane
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Low pressure
small number open doesn't cause full AP
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If layers deform enough, (high Pressure) so
enough Na+ channels open and full AP fired
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What does generator potential create
AP that passes down neurone then AP transmitted via other neurone to the CNS
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What is the adaptation
When P first applied to corpuscle initiates a volley of impulses in its sensory neurone however with continous pressure the frequency of AP decreases quickly and soon stops
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Where does this adaptation occur
In most sense receptors
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Why is it useful
because it prevents the nervous system from being bombarded with info about insignificant matters like touch and pressure of our clothing
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What do stimuli represent
changes in the environment, so if there is no change the sense receptors soon adapt
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But if we quickly remove the pressure from an adapted PC what happens
a fresh volley of impulses will be generated- speed of adaptation varies among different kinds of receptors
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R involved in proprioception
such as spindle fibres adapt slowly if at all
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Other cards in this set

Card 2

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What does each receptor do

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Initiates nerve impulse in sensory neurone when it is physically deformed by an outside force

Card 3

Front

Examples

Back

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Card 4

Front

What do mecho receptors allow

Back

Preview of the front of card 4

Card 5

Front

What is light touch detected by

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