neurophysiology. membrane potential how is the resting membrane potential changed?
TRANSCRIPT
Neurophysiology Neurophysiology
Membrane Potential
How is the Resting Membrane Potential Changed?
Changes in Membrane Potential
• From -70 mV to +30 mV
Channels and Changes in the Membrane Potential
Chemically Gated Channels Chemically Gated Channels
Voltage-Gated Channels Voltage-Gated Channels
When these gates are opened, ions move down their electrochemical gradient!When these gates are opened, ions move down their electrochemical gradient!
How are Graded Potentials Different from Action Potentials?
Only occur in ‘excitable membranes’Muscle cells Neurons Axon Hillock
Graded potentials may turn into action potentialsSummation
○ Temporal and Synaptic
Comments Strength does not decreaseSelf propagating
Only occur in ‘excitable membranes’Muscle cells Neurons Axon Hillock
Graded potentials may turn into action potentialsSummation
○ Temporal and Synaptic
Comments Strength does not decreaseSelf propagating
Propagation(fig. 11.13)
Propagation(fig. 11.13)
ThresholdsThresholds
Ion channels - openNeuron cannot respond to another stimulus Na+ channels must close first!
○ Resets normal polarized state
Types AbsoluteRelative
Pre-Synaptic and Post-Synaptic Activity
• Depolarization waves– Moves towards the synapse
• Conduction speed depends on – Diameter of axon– Myelination
• Nerve Fiber Types– Group A, B, C
Saltatory Conduction
When the Nerve Transmission Reaches the Synapse
Electrical Synapse – less common; coordinate neuron activity between neurons; ions move through gap junctions; most abundant in embryonic tissue; brain find stereotyped movements (hippocamus); glial cells of CNS
Chemical Synapses – ions flow between channels; Neurotransmitters are released
Chemical Synapse
At the Synapse
Summation
• Neurons of CNS – neuronal pools – Integrate incoming information
• Neurons of CNS – neuronal pools – Integrate incoming information
1. Discharge zone 2. Facilitated zone 1. Discharge zone 2. Facilitated zone
Neural Circuits