2. nerve and aksi potensial
TRANSCRIPT
-
8/12/2019 2. Nerve and Aksi Potensial
1/21
-
8/12/2019 2. Nerve and Aksi Potensial
2/21
2
-
8/12/2019 2. Nerve and Aksi Potensial
3/21
3
-
8/12/2019 2. Nerve and Aksi Potensial
4/21
Active Transport of Sodium and PotassiumIons Through the MembraneThe Sodium-
Potassium (Na+-K+) Leakage of Potassium and Sodium Through
the Nerve Membrane
4
-
8/12/2019 2. Nerve and Aksi Potensial
5/21
5
-
8/12/2019 2. Nerve and Aksi Potensial
6/21
6
-
8/12/2019 2. Nerve and Aksi Potensial
7/21
Contribution of the Potassium Diffusion Potential: Because of the high ratio of potassium ions insideto outside, 35:1, the Nernst potential corresponding
to this ratio is
94 millivolts
Therefore, ifpotassium ionswere the only factor causing theresting potential
Contribution of Sodium Diffusion Through theNerve Membrane : diffusion of sodium ions
through the K+-Na+ leak channels. The ratio ofsodium ions from inside to outside the membrane is0.1
Contribution of the Na+-K+ Pump
7
-
8/12/2019 2. Nerve and Aksi Potensial
8/218
-
8/12/2019 2. Nerve and Aksi Potensial
9/219
-
8/12/2019 2. Nerve and Aksi Potensial
10/2110
-
8/12/2019 2. Nerve and Aksi Potensial
11/21
A Positive-Feedback Vicious Cycle Opens the SodiumChannels if any event causes enough initial rise in the membrane potential from90 millivolts toward the zero level, the rising voltage itself causes
many voltage-gated sodium channels to begin opening. This allowsrapid inflow of sodium ions, which causes a further rise in themembrane potential
Threshold for Initiation of the Action Potential A sudden rise in membrane potential of 15 to 30 millivolts usually is
required. Therefore, a sudden increase in the membrane potential in alarge nerve fiber from 90 millivolts up to about 65 millivolts usuallycauses the explosive development of an action potential. This level of65 millivolts is said to be the threshold for stimulation
11
-
8/12/2019 2. Nerve and Aksi Potensial
12/2112
-
8/12/2019 2. Nerve and Aksi Potensial
13/2113
-
8/12/2019 2. Nerve and Aksi Potensial
14/2114
-
8/12/2019 2. Nerve and Aksi Potensial
15/2115
-
8/12/2019 2. Nerve and Aksi Potensial
16/21
16
-
8/12/2019 2. Nerve and Aksi Potensial
17/21
17
-
8/12/2019 2. Nerve and Aksi Potensial
18/21
18
-
8/12/2019 2. Nerve and Aksi Potensial
19/21
TRANSMISI SINAPTIK
ELEKTRIK
19
Ner e fiber t pes in mammalian ner e
-
8/12/2019 2. Nerve and Aksi Potensial
20/21
Nerve fiber types in mammalian nerve.
Fiber Type Function
Fiber
Diameter
(m)
Conduction
Velocity
(m/s)
Spike
Duration
(ms)
Absolute
Refractory
Period (ms)
A
Proprioception; somatic
motor
12-20 70-120
Touch, pressure 5-12 30-70 0.4-0.5 0.4-1
Motor to muscle
spindles
3-6 15-30
Pain, cold, touch 2-5 12-30
B Preganglionic
autonomic
-
8/12/2019 2. Nerve and Aksi Potensial
21/21
Numerical classification sometimes used for sensory
neurons.
Number Origin Fiber Type
Ia Muscle spindle, annulospinal ending. A
Ib Golgi tendon organ. A
II Muscle spindle, flower-spray ending; touch, pressure. A
III Pain and cold receptors; some touch receptors. A
IV Pain, temperature, and other receptors. Dorsal root C