coordination of body functions addendumcoordination of body functions addendum heyer 1 neuron: a...
TRANSCRIPT
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Coordination of Body Functions addendum
Heyer 1
Neuron: A Nerve Cell
• Dendrites: increase surface area of cell body to receive signals.
• Cell body: location of nucleus and most organelles.
• Axon: conducts electrochemical impulses.
• Termini: transmit message to target cell.
Axons are Polarized: Resting Potential
2
3
Resting Membrane Potential• Resting membrane potential of
most cells ranges from—65 to –85 mV.
Time (ms)
Volta
ge (m
V)
0
–65
+30
Resting potential
Axons are Polarized:
Time (ms)Vo
ltage
(mV)
0
–65
+30
Resting potential
Axons are Polarized:
Time (ms)
Volta
ge (m
V)
0
–65
+30
Resting potential
If Na+-gates open ⇢Na+ enters →Depolarizes (less negative)
Axons are Polarized:
Time (ms)
Volta
ge (m
V)
0
–65
+30
Resting potential
If Cl–-gates open ⇢Cl– enters
OR
If K+-gates open ⇢K+ leaves
→ Hyperpolarizes(more negative)
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Coordination of Body Functions addendum
Heyer 2
Generator PotentialAt axon hillock:If sufficient depolarizations add to threshold;more Na+-gates open (positive feedback)→ action potential
Time (ms)
Volta
ge (m
V)
0
–65
+30
Resting potential
threshold potential
spike potential
action potential
generator potential
Generator PotentialAt axon hillock:But hyperpolarizations push further from threshold→ inhibit action potential from starting
Time (ms)
Volta
ge (m
V)
0
–65
+30
Resting potential
threshold potential
spike potential
Generator Potential = summation of EPSPs and IPSPs• Excitatory neurons ⇢ neurotransmitter opens Na+-gates
→ Excitatory post-synaptic potentials (EPSP)• Inhibitory neurons ⇢ neurotransmitter opens K+-gates or Cl–-gates
→ Inhibitory post-synaptic potentials (IPSP)
Generator Potential = summation of EPSPs and IPSPs
• Generator Potential is graded• Action potential is “all-or-none”
Time (ms)
Volta
ge (m
V)
0
–65
+30
Resting potential
threshold potential
spike potentialsame
action potential
inadequategenerator potential
stronggenerator potential
adequategenerator potential
• Once an action potential is generated at the axon hillock, the signal is conducted down the axon.• Since each action potential is “all-or-none”, so is each nerve impulse.