The Excitable Cell Flashcards
(47 cards)
Neurones must..?
- Collect
- Integrate
- Output
What does the nervous system do?
System of communication that allows an organism to react rapidly and modifiably to changes in its environment
Electrical activity provides a ____, _____, and _____ means for neurons to receive, integrate and transmit signals
- Rapid
- Reliable
- Flexible
Electrical signals may be divided into…
- Action potentials
- Graded potentials
Action potential
- Fixed size
- All-or-nothing
- Propagate the axon
- Can pass both ways but tend to go only one way
Graded potential
- Variable size
- Local signals not propagated over long distances
- Pass both ways along neuronal membrane
Action potentials are coded by…
Frequency
Graded potentials are coded by…
Size
Why do neurons have a resting potential?
Consequence of..
- Selectively permeable membrane
- Unequal distribution of charged molecules/ions
- Physical forces
Channels….
Confer selectivity
Pumps assist…
Unequal charge distribution
What is the resting potential of a membrane?
Between -65mV and -90mV
What is an absolute requirement for a functioning nervous system?
A negative Vm
Important ion pumps
- Na+/K+ ATPase
- Ca2+ pumps
Na+/K+ ATPase
- Exchanges extracellular K+ for intracellular Na+
- Against concentration gradient - uses ATP
- Uses about 70% brain ATP
Ca2+ pump
- Transports Ca2+ out of neurons
- Maintains low intracellular Ca2+
- Ca2+ is toxic at high intracellular levels
Intracellular K+
100 mM
Extracellular K+
5 mM
Intracellular Na+
15 mM
Extracellular Na+
150 mM
Intracellular Ca2+
0.0002 mM
Extracellular Ca2+
2 mM
Intracellular Cl-
13
Extracellular Cl-
150
