BioT2C3-Action potential-transmission of impulse 2015-student.ppt
1. Resting Potential & Action Potential
Resting potential—
membrane potential of a neuron membrane when
not conducting an impulse
Resting neurons, there is an imbalance of ions inside & outside
of cell membranes.
Cytoplasm inside membrane is –ve charge, fluid outside the
membrane is +ve. The membrane is polarized.
The difference in electrical charge carries potential energy,
which can be measured as a voltage
What is the resting potential of a resting neuron?
a resting neuron has a resting potential of -70 mv
5. the state of cell membrane while conducting an
impulse
is triggered when a nerve impulse triggers voltage-gated Na+
channels to open, and Na+ rush into cell, reversing the charges
Cytoplasm inside the membrane becomes +ve in charge,
the fluid outside the membrane becomes -ve.
Na+ channels close, while voltage-gated K+ channels open,
allowing K+ to rapidly diffuse out.
Plasma membrane returns to being +ve on outside & -ve on the
inside, and the K+ channels close
Action potential
8. Define (3 m)
(i) Resting potential –
(ii) Action potential
(iii) Threshold
9. 9
Propagation of nerve impulses
depolarization of action potential
Spreads to neighboring region of
the membrane, reiniatiatng action
potential.
- To the left of this region, membrane
is repolarizing as K+ flows outward
Depolarization-repolarization process
is repeated in next region of the
membrane.
-Local currents of ions across
plasma membrane cause action
potential to be propagated along the
length of axon.
An action potential is generated
as Na+ flows inward across
membrane at one location.
15. In a nerve impulse, what happens at the site
following the highest point of the action
potential? (1 m)
A. Voltage-gated Na+ channels open, Na+ is
pumped in.
B. Voltage-gated Na+ channels open, Na+
diffuses out.
C Voltage-gated K+ channels open, K+ is
pumped out.
D Voltage-gated K+ channels open, K+ diffuses
out.
16. Explain how a nerve impulse passes along a non-
myelinated neuron (axon). (6 m)
In resting neurons, there is imbalance of ions inside & outside
of cell membranes-“resting potential”.
Cytoplasm inside the membrane is –ve charge, fluid outside the
membrane is +ve.
- The membrane is said to be polarized.
Difference in electrical charge carries potential energy, which
can be measured as a voltage
A resting neuron has a resting potential of ~-70 mv.
An action potential is triggered when a nerve impulse triggers
voltage-gated sodium channels to open, Na+ rush into the cell,
reversing the charges
- Cytoplasm inside membrane becomes +ve in charge, and the
fluid just outside the membrane becomes -ve.
Very quickly, Na + channels close, voltage-gated K + channels
open, allowing K + to rapidly diffuse out.
- Plasma membrane returns to resting stage, K + channels close
17. What is the role of active transport in the
transmission of nerve impulses by neurones?
A. Propagates an action potential by pumping Na+
across the membrane out of the neurone.
B. Propagates an action potential by pumping Na+
across the membrane into the neurone.
C. Initiates the action potential needed for the
transmission of an impulse by pumping Ca+ out of
the endoplasmic reticulum.
D. Establishes the resting potential needed for the
transmission of an impulse by pumping Na+ and
K+ ions across the membrane.
18. Action Potential Generation Properties
Absolute Refractory
- During this period, voltage gated channels
responsible for action potential have not
reset, do not respond to stimulation.
Relative Refractory
- This period corresponds to the hyperpolarization of the cell.
- It is more difficult to generate a 2nd action potential.
• Refractory periods
- times when it is either impossible or
more difficult than normal to
generate a 2nd action potential.
