6. cns 2

A graded potential is a local electrical change in the membrane. ,[object Object],[object Object],[object Object],[object Object]

Upward deflection = Decrease in potential Downward deflection = Increase in potential Repolarization Hyperpolarization Depolarization Resting potential

Graded potentials spread by passive current flow. ,[object Object]

Graded potentials die out over short distances. ,[object Object],[object Object],[object Object]

An action potential occurs if a membrane reaches threshold potential. ,[object Object],[object Object],[object Object]

Graded potential (change in membrane potential relative to resting potential) Magnitude of stimulus Resting potential Time Stimuli applied

Action potentials travel from the axon hillock to axon terminals. ,[object Object],[object Object],[object Object],[object Object]

Once initiated, an action potential is conducted throughout the axon. ,[object Object],[object Object],[object Object],[object Object]

Change in membrane potential in mV relative to resting potential— i.e., magnitude of electrical signal Few mm Distance Initial active area Decremental spread of graded potential Decremental spread of graded potential Resting potential Few mm

Myelination with nodes increases the speed of conduction of the action potential. ,[object Object],[object Object],[object Object]

Nerve fibers can regenerate. ,[object Object],[object Object]

Two neurons can interact at the synapse. ,[object Object],[object Object],[object Object]

A neurotransmitter can carry a signal across the synapse by a series of steps. ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Presynaptic axon terminal Voltage-gated Ca 2+ channel Ca 2+ Neurotransmitter molecule Synaptic cleft Chemically gated ion channel for Na + , K + , or Cl - Receptor for neurotransmitter Postsynaptic neuron Subsynaptic membrane Synaptic vesicle Synaptic knob

The signal at the synapse either excites or inhibits the postsynaptic neuron. ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Excitatory synapse Threshold potential Activation of synapse EPSP

Inhibitory synapse IPSP Threshold potential Activation of synapse

Excitatory presynaptic inputs Inhibitory presynaptic input Recording potential of postsynaptic cell

Temporal summation Spatial summation EPSP–IPSP cancellation Threshold potential Resting potential Recording potential of postsynaptic cell

Recording potential of postsynaptic cell C

Recording potential of postsynaptic cell C Threshold potential Resting potential

Other characteristics of neurotransmitters are: ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Neuropeptides act mainly as neuromodulators. ,[object Object],[object Object],[object Object]

The effectiveness of presynaptic input can be altered by presynaptic facilitation or inhibition. ,[object Object],[object Object],[object Object]

Drugs and diseases can alter synaptic transmission. ,[object Object],[object Object],[object Object],[object Object],[object Object]

Neurons are linked through complex converging and diverging pathways. ,[object Object],[object Object]

Presynaptic inputs Postsynaptic neuron Convergence of input (one cell is influenced by many others) Presynaptic inputs Divergence of output (one cell influences many others) Postsynaptic neurons Arrows indicate direction in which information is being conveyed.

6. cns 2

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6. cns 2