Zusammenfassung der Ressource
Receptors
- These are cells which
detect a stimulus and
are usually found on
the surface of cells.
- They are very specific and detect
only one form of a stimulus, e.g.
photoreceptors only detect light
intensity.
- Resting potential
- During this, the inside of
the receptor cell is positive
and the outside is negative,
creating a voltage in the
cell membrane.
- Voltage is also known is also
known as potential difference,
hence why this is called resting
potential.
- Also, since nothing is happening yet, the
resting potential has to be maintained by
the movement of Na+ through ion pumps
and channels.
- As Sodium ions are positively
charged, if they move out into
the receptor cell, the inside
would become more positive.
- For every 2 K+ in,
3Na out.
- generator potential
- This comes after resting potential and is created by the detection
of a stimulus
- This detection causes the receptor cell membrane to
become more permeable, opening more ion
channels, so Na+ ions diffuse in and out of a cell, resulting
in a larger potential difference of the cell membrane.
- The stronger the
stimulus, the higher the
generator potential.
- Action potential
Anmerkungen:
- The potential differences are measured in milivolts (mV).
- If the generator potential reaches a particular
level, an action potential is triggered which
causes a nerve impulse to travel through a
sensory neuron. This level is known as the threshold.
- After this, the impulse travels to
your brain to send the information
really fast.
- The Pacinian corpuscle
- It is found on the
surface of your skin.
- It is a mechanoreceptor so
only detects, movement
and vibrations.
- After it detects a stimulus e.g. a tap
on your arm, its layers deform.
- This means the membrane of
your sensory nerve ending also
deform e.g. the stretch-mediated
Na+ channels.
- The movement of Na+ by active transport
creates a generator potential. If it reaches the
threshold, an impulse is released.
- This allows you to feel certain objects
- Rods and cones.
- These are found on the
retina in your eye
- These are photoreceptors so
detect light intensity
- The light shines through the
lens in your eye, onto your rods
and cones (the optical pigments).
- The rods only detect black and white
light. However, they have a low visual
acuity (the detail of your image).
- This is because many rods
are joined to just one bipolar
nerve, which joins onto the
optic nerve.
- Therefore, the message your brain
receives is more so it cannot
distinguish between two points..
- These are found in
the peripheral part of
the retina.
- The cones detect 3 colors, green, red and blue.
- They have a larger visual acuity as each cone
is joined t only one bipolar neuron.
- They also absorbs low light intensities compared to rods.