Nuerons, Synapses, and Signaling Concept Checks

Suppose a cells membrane potential shirts from -70 mV to -50 mV. What changes in the cell permeability to K+ or Na+ could cause such a shift?

A decrease in permeability to K+, an increase in permeability to Na+ or both.

How do action potential and graded potentials differ?

A graded potential has a magnitude that varies with stimulus strength, whereas an action potential has an all-or-none magnitude that is independent of stimulus strength.

Compare and contrast the structure and function of axons and Dendrites?

Axons and dendrites extend from the cell body and function in information flow. Dendrites transfer information to the cell body, whereas axons transmit information from the cell body. A typical neuron has multiple dendrites and one axon.

Suppose a mutation caused gated sodium channels to remain inactivated longer after an action potential. How would this affect the frequency at which action potentials could be generated? Explain.

the maximum frequency would decrease because the refractory period would be extended.

Organophosphate pesticides work by inhibiting acetylcholinesterase, the enzyme that breaks down the neurotransmitter acetylcholine. Explain how these toxins would affect EPSPs produced by acetylcholine

these toxins would prolong the EPSPs that acetylcholine produces because the neurotransmitter would remain longer in the synaptic cleft

How do both negative and positive feedback contribute to the changes in membrane potential during an action potential?

Positive feedback is responsible for the rapid opening of many voltage gated sodium channels causing the rapid outflow of sodium ions responsible for the rising phase of the action potential. As the membrane potential becomes positive, voltage gated potassium channels open in a form of negative feedback that helps bring about falling phase of action potential.

Describe the basic pathway of information flow through neurons that causes you turn your head when someone calls your name.

Sensors in your ear transmit information from the cell body. There the activity of inter-neuron in processing center enables you recognize your name. In response, signals transmitted by motor neuron cause contraction of the muscles that turn your neck.

Under what circumstances could ions flow through an ion channel from a region of lower ion concentration to a region of higher ion concentration?

Ion can flow against a chemical concentration gradient of greater magnitude.

In multiple sclerosis, a persons myelin sheaths harden and deteriorate. How would this affect nervous system function?

Loss of insulation provided by myelin sheath leads to a disruption of action potential propagation along axons. Voltage gated sodium channels are restricted to the nodes of Ranvier and without insulating effects myelin the inward current produced at one node during an action potential cannot depolarize the membrane to the threshold at the next node.

How might increased branching of axon help coordinate responses to signals communicated by nervous system?

increased branching of the axon would allow control of a greater number of postsynaptic cells, enhancing coordination of response to nervous system signals

How is it possible for a particular neurotransmitter to produce opposite effects in different tissues?

it can bind to different types of receptors each triggering a specific response in postsynaptic cells