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
- 3. 3 -ve b c d
- 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
- 6. 6 Action Potential: change of membrane permeability to Na+ & K + channel opens = permeability increases
- 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.
- 12. Saltatory Propagation along a Myelinated Axon
- 13. Saltatory Propagation along a Myelinated Axon
- 14. Propagation of an Action Potential along an Unmyelinated Axon
- 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.
- 20. 20 freq. only
- 21. 21 1. Axon Diameter (thicker > faster) 2. Myelin Sheath (faster) 3. Temperature (higher > faster) Factors affect rate of impulse transmission How fast do nerve impulses travel May 27, 2000. 119m/s (muscles) 76.2m/s (touch) 0.61m/s (pain)