Signaling Within the Neuron

Question 1

what kind of cell is a neuron

Answer 1

• eukaryote

Question 2

resting potential of the cell

Answer 2

• -70 mV
• done by testing the squid’s giant axons with al electrode on the outer and inner side of the neuron

Question 3

Oscilloscope

Answer 3

• a device that measures electric potential as a function of time
• used to record voltage changes on an axon

Question 4

measuring neurons electrical activity

Answer 4

• charged particle (ion) movement across the eukaryote’s cell membrane results in a different electrical charge inside the cell relative to the interstitium

Question 5

cations

Answer 5

• positively charged ions
• sodium, potassium and calcium

Question 6

anions

Answer 6

• negatively charged ions
• chloride and some protein molecules

Question 7

membrane potential

Answer 7

• unequal ion concentration inside vs outside the cell membrane produce result in a measurable voltage across the membrane called the membrane potential

Question 8

Maintaining resting potential

Answer 8

• potassium and chloride channels are ungated which means they allow potassium and chloride ions to pass freely thought the membrane in both directions
• sodium channels are gated which means that Na+ cannot pass freely through the membrane unless the gate is held open
• active ions pumps located in the membrane export 3 Na+ ions from the cytoplasm to the interstitium and import 2 K+ ions from the intersitium into the cytoplasm with each pump cycle

Question 9

Altering the neuron’s membrane potential

Answer 9

• changing the permeability of the neuron’s plasma membrane to various species of ions causes the transmembrane potential to deviate from its resting level of -70 mV
• adding positive ions to the cytoplasm will depolarize the membrane potential while adding negative ions to the cytoplasm will hyperpolarize it

Question 10

depolarization

Answer 10

• if the change in the membrane potential goes from -70 mV to values less negative

Question 11

hyperpolarization

Answer 11

• if the change in the membrane potential from -790 mV to calues more negative

Question 12

graded potentials

Answer 12

• found mainly in the dendrites
• excitatory postsynaptic potentials (EPSPs)
• Inhibitory postsynaptic potentials (IPSPs)
• a brief variable change in the transmembrane potential measured in the neuron’s dendrites and soma caused by the sum of the EPSPs and IPSPs generated by the binding of neurotransmitter molecules to receptors on the postsynaptic membrane of the receiving cell

Question 13

EPSP’s

Answer 13

• excitatory postsynaptic potentials are created by neurotransmitter chemicals binding to excitatory receptors embedded in the membrane of the neuron’s dendrite that caused the resting potential in the dendritic region to depolarize

Question 14

IPSPs

Answer 14

• inhibitory postsynaptic potentials are created by neurotransmitter chemicals bringing to inhibitory receptors embedded in the membrane of the neuron’s dendrites that causes the cell’s resting potential in the dendritic region to hyperpolarize

Question 15

action potential

Answer 15

• a brief all or on change in the membrane potential generated in the neuron’s soma and propagated without decrement along the full length a neuron’s axon to its terminal futons
• action potentials can carry information over great distances using changed in the production rate rather than changes in amplitude

Question 16

the rate law

Answer 16

• demonstrated form the intracellular recording of action potentials generated in the optic nerve of the cat to top a weak and bottom a strong light stimulus
• note there are spontaneous APs produced in the neuron both before and after the light stimulus is presented
• more frequent when the stimulus is strong

Question 17

velocity of aciton potential

Answer 17

• conduction speed varies inversely with the cytoplasm’s electrical resistance
• cytoplams resistance varies inversely with the cross-secontal area
• an axon with a large cross-sectional areaa as a lower cytoplasmic resistance thus a higher conduction velocity

Question 18

speed of action potential

Answer 18

• conduction speed also varies inversely with the electrical capacitance of the axon membrane
• myelinated axons have a lower capacitance than unmyelinated axons
• a myelination axons with a large cross sectional area has the highest conduction velocity