OCR A LEVEL BIOLOGY NEURONAL
COMMUNICATION TEST AND LATEST
RELEASED.
Schwann cells which make myelin... - CorreCt Answers -Myelin-secreting
membrane surrounds the axon multiple times, simultaneously blocking
Na+/K+ channels - forcing AP to 'jump'.
Schwann cells which don't make myelin... - CorreCt Answers -2/3rds of
peripheral neurons, each cell houses several axons, providing protection.
There is a small gap between the Schwann cell membrane and the
axon/dendron so Na+ and K+ channels can form along the whole
axon/dendron
All receptors are ________ to their stimulus - CorreCt Answers -specific
Receptors - CorreCt Answers -Cells and special structures that allow living
organisms to sense changes in their internal or external environment. They
are transducers
Transducer - CorreCt Answers -Something which converts 1 form of energy
into another.
Examples of receptors - CorreCt Answers -Photoreceptors
Thermoreceptors
Chemoreceptors
Mechanoreceptors
,Photoreceptors - CorreCt Answers -Convert light energy to electrical
energy. (E.G. rods and cones)
Thermoreceptors - CorreCt Answers -Detect heat energy and convert it to
electrical energy. (e.g. receptors in hypothalamus (internal) and skin
(external)).
Chemoreceptors - CorreCt Answers -Convert chemical energy to electrical
energy (e.g. olfactory sensors in the nose)
Mechanoreceptors - CorreCt Answers -Convert energy from
movement/stretch/pressure and transfer it to electrical energy. (e.g.
Parcinian Corpuscle)
How do parcinian corpuscles work at rest? - CorreCt Answers -Na+/K+
pumps actively pump 3 Na+ out and 2 K+ in, causing the parcinian
corpuscle to be more positive on outside and more negative on inside. Some
non-gated K+ channels are always open in the membrane, so some K+
leaves via facilitated diffusion, so is even more + on outside and - on inside.
Inside also has anions, so is even more negative. It is polarised.
Why could even more K+ leave the parcinian corpuscle at rest than leave
through open K+ ion channels? - CorreCt Answers -The membrane is 20x
more permeable to K+ than Na+, so even more K+ diffuses out.
Resting potential (for parcinian corpuscle) - CorreCt Answers --70mV
, Parcinian corpuscle when stimulated - CorreCt Answers -When pressure is
applied it causes the connective tissue to stretch/deform, which causes
stretch-mediated Na+ channels to open so Na+ enters through facilitated
diffusion into the nerve ending, so it becomes less negative on inside. This
depolarisation is the generator potential, if it reaches the threshold
potential (-55mV), Na+ channels open = huge influx of Na+, causing
membrane to reach +40mV and an AP happens.
What happens when the parcinian corpuscle is stimulated with more
pressure? - CorreCt Answers -More stretch-mediated Na+ channels open,
even more Na+ enters.
All or none law - CorreCt Answers -The principle that the action potential in
a neuron does not vary in strength; the neuron either fires at full strength
when it reaches +40mV or it does not fire at all
How is an action potential generated? - CorreCt Answers -RP is achieved
through the Na+/K+ pump pumping more Na+ out & K+ channels &
anions. When stimulus happens, voltage gated Na+ channels open & Na+
enters neuron. If enough Na+ enters to reach -55mV, more channels open
so huge influx of Na+ to +40mV (full depolarisation). Then voltage-gated
Na+ close & K+ channels open, K+ leaves so more + on outside & - on
inside, K+ take long time to close, so enough leaves that membrane is
hyperpolarised to less than -70mV, Na+/K+ pump then begins again to
return it back to resting potential (another AP cannot be fired during this,
known as "refractory period.")
How do ions move into a neuron? - CorreCt Answers -Down an
electrochemical gradient via facilitated diffusion
COMMUNICATION TEST AND LATEST
RELEASED.
Schwann cells which make myelin... - CorreCt Answers -Myelin-secreting
membrane surrounds the axon multiple times, simultaneously blocking
Na+/K+ channels - forcing AP to 'jump'.
Schwann cells which don't make myelin... - CorreCt Answers -2/3rds of
peripheral neurons, each cell houses several axons, providing protection.
There is a small gap between the Schwann cell membrane and the
axon/dendron so Na+ and K+ channels can form along the whole
axon/dendron
All receptors are ________ to their stimulus - CorreCt Answers -specific
Receptors - CorreCt Answers -Cells and special structures that allow living
organisms to sense changes in their internal or external environment. They
are transducers
Transducer - CorreCt Answers -Something which converts 1 form of energy
into another.
Examples of receptors - CorreCt Answers -Photoreceptors
Thermoreceptors
Chemoreceptors
Mechanoreceptors
,Photoreceptors - CorreCt Answers -Convert light energy to electrical
energy. (E.G. rods and cones)
Thermoreceptors - CorreCt Answers -Detect heat energy and convert it to
electrical energy. (e.g. receptors in hypothalamus (internal) and skin
(external)).
Chemoreceptors - CorreCt Answers -Convert chemical energy to electrical
energy (e.g. olfactory sensors in the nose)
Mechanoreceptors - CorreCt Answers -Convert energy from
movement/stretch/pressure and transfer it to electrical energy. (e.g.
Parcinian Corpuscle)
How do parcinian corpuscles work at rest? - CorreCt Answers -Na+/K+
pumps actively pump 3 Na+ out and 2 K+ in, causing the parcinian
corpuscle to be more positive on outside and more negative on inside. Some
non-gated K+ channels are always open in the membrane, so some K+
leaves via facilitated diffusion, so is even more + on outside and - on inside.
Inside also has anions, so is even more negative. It is polarised.
Why could even more K+ leave the parcinian corpuscle at rest than leave
through open K+ ion channels? - CorreCt Answers -The membrane is 20x
more permeable to K+ than Na+, so even more K+ diffuses out.
Resting potential (for parcinian corpuscle) - CorreCt Answers --70mV
, Parcinian corpuscle when stimulated - CorreCt Answers -When pressure is
applied it causes the connective tissue to stretch/deform, which causes
stretch-mediated Na+ channels to open so Na+ enters through facilitated
diffusion into the nerve ending, so it becomes less negative on inside. This
depolarisation is the generator potential, if it reaches the threshold
potential (-55mV), Na+ channels open = huge influx of Na+, causing
membrane to reach +40mV and an AP happens.
What happens when the parcinian corpuscle is stimulated with more
pressure? - CorreCt Answers -More stretch-mediated Na+ channels open,
even more Na+ enters.
All or none law - CorreCt Answers -The principle that the action potential in
a neuron does not vary in strength; the neuron either fires at full strength
when it reaches +40mV or it does not fire at all
How is an action potential generated? - CorreCt Answers -RP is achieved
through the Na+/K+ pump pumping more Na+ out & K+ channels &
anions. When stimulus happens, voltage gated Na+ channels open & Na+
enters neuron. If enough Na+ enters to reach -55mV, more channels open
so huge influx of Na+ to +40mV (full depolarisation). Then voltage-gated
Na+ close & K+ channels open, K+ leaves so more + on outside & - on
inside, K+ take long time to close, so enough leaves that membrane is
hyperpolarised to less than -70mV, Na+/K+ pump then begins again to
return it back to resting potential (another AP cannot be fired during this,
known as "refractory period.")
How do ions move into a neuron? - CorreCt Answers -Down an
electrochemical gradient via facilitated diffusion
