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Physiology > Cell Physiology, Nervous system > Flashcards

Cell Physiology, Nervous system Flashcards

1
Q

neural communication

A
  • accomplished by nerve cells
  • specialized for rapid electrical signaling and for secreting neurotransmitters
  • short-distance
  • act on nearby target organs
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2
Q

hormonal communication

A
  • accomplished by hormones
  • long distance chemical messengers
  • secreted by endocrine glands into the blood
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3
Q

polarization

A
  • anytime the membrane has potential other than 0 mV

- positive or negative direction

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4
Q

depolarization

A
  • membrane becomes less polarized
  • going closer to 0mV
  • big is an action potential
  • small is a graded potential
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5
Q

repolarization

A

-the membrane returns to resting potential after having been depolarized

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6
Q

hyperpolarization

A
  • membrane becomes more polarized

- inside becomes more negative than resting potential

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7
Q

graded potentials

A
  • occurs in active area of the membrane
  • magnitude varies directly with the magnitude of the stimulus
  • spread decrementally by local current flow
  • die over a short distance
  • the larger the triggering event the larger the graded potential
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8
Q

triggering event

A

-triggers a change in membrane potential by alternating membrane permeability

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9
Q

action potential

A
  • excitable cell membrane is depolarized to threshold potential
  • at threshold, NA+ and K+ permeability are initiated
  • goes from -70mV to +30mV
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10
Q

threshold potential

A

between -50 and -55 mV

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11
Q

voltage-gated channels

A
  • when Na+ and K+ channels are activated at threshold
  • opening a Na+ channel is dependent on positive feedback cycle
  • Na+ exist in 3 conformations (closed and capable of opening, open, closed and not capable of opening)
  • K+ channels can exist in 2 conformations (open and closed)
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12
Q

Na+ and K+ channels at resting potential

A

-all voltage gated channels are closed

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13
Q

Na+ and K+ channels at threshold

A
  • Na+ activation gate opens and permeability of Na+ rises

- Na+ enters cell causing a depolarization to +30mV (rising phase of action potential)

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14
Q

Na+ and K+ channels at peak of action potential

A
  • Na+ inactivation gate closes and the permeability of Na+ falls, ending the net movement into the cell
  • at the same time K+ activation gate opens and the permeability of K+ rises
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15
Q

Na+ and K+ channels at the falling phase

A

-K+ leaves the cell causing repolarization to resting potential

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16
Q

Na+ and K+ channels at returning to resting potential

A
  • Na+ activation gate closes and inactivation gate opens

- resetting channel to respond to another depolarizing triggering event

17
Q

Na+ and K+ channels at hyperpolarization

A
  • K+ still open and flows outward briefly

- K+ gate closes and sets membrane back to resting potential

18
Q

refectory periods

A
  • absolute and relative
  • ensures the one-way propagation of action potentials
  • responsible for setting an upper limit on the frequency of action potentials
19
Q

absolute refectory periods

A
  • period of time when a patch of membrane cannot be re-stimulated no matter how strong the stimulus
  • Na+ channels cannot open again until they reach the “closed but capable of opening again” confirmation when resting potential is restored
20
Q

relative refractory period

A
  • period of time during which a patch of membrane can only be re-stimulated by a stronger than normal stimulus
  • fewer voltage gated Na+ channels are in the position to be jolted open (some take longer to be restored at their capable of opening conformation state)
21
Q

action potential characteristics

A
  • occur either maximally in response to stimulation or not at all
  • the all or none law
  • variable strengths of stimuli are coded by varying the frequency of action potentials, not their size
22
Q

two types of action potential propagation

A
  • contiguous conduction

- saltatory conduction

23
Q

contiguous conduction

A
  • in unmyelinated fibers

- slower

24
Q

saltatory conduction

A
  • in myelinated fibers
  • faster (jump)
  • 50 times faster
  • form local currents an action potential at one node produces an action potential at the next node
  • schwann cell in PNS and oligodendrocytes in the CNS
25
Q

myelin

A
  • thick layers of lipids that cover axon at regular intervals
  • insulator to prevent leakage of current
  • nodes of Ranvier: between myelinated regions, bare patch of membrane
  • current flows across the nodes
26
Q

neurotransmitter action

A
  • excitatory post-synaptic potential (EPSP)

- inhibitory post-synaptic potential (IPSP)

27
Q

excitatory post-synaptic potential

A
  • if binding of the neurotransmitter opens K+ and Na+ channels that result in a small depolarization
  • cell gets closer to threshold
28
Q

inhibitory post-synaptic potential

A
  • if binding of the neurotransmitter opens either K+ or Cl- channels the result is a small hyperpolarization
  • less likely to reach threshold
29
Q

synaptic summation

A
  • temporal
  • spatial
  • if excitatory is dominate, the cell is brought closer to threshold, inhibitory is taken further from threshold
  • the summation of all inputs are called the grand post synaptic potential (GPSP)
30
Q

temporal summation

A

-EPSP/IPSP from a single, repetitively firing, presynaptic input that occur so close together in time they add together

31
Q

spatial summation

A
  • adding EPSP/IPSP simultaneously from different presynaptic inputs
  • faster
32
Q

neuropeptides

A
  • large molecule made up of 2-40 amino acids
  • function as neuromodulators
  • act slowly to produce long term changes at the synapse
33
Q

cellular communication

A
  • direct: via gap junctions and linkup of complementary surface markers
  • indirect: carried out through extracellular chemical messengers
  • more common
34
Q

extracellular chemical messengers

A
  • paracrines: local chemical messengers
  • neurotransmitters: short range chemical messengers released by neurons
  • hormones: long range chemical messengers, secreted into the blood by endocrine glands
  • neurohormones: long range chemical messengers secreted into the blood by neurons
35
Q

hormonal communication

A
  • hydrophilic: highly water soluble, low lipid solubility

- lipophilic: highly lipid solubility, poorly soluble in water, go into cell easier

36
Q

convergence

A
  • a given neuron that may have many other neurons synapsing on it
  • one cell is influenced by many
37
Q

divergence

A
  • the branching of axon terminals so that a single cell synapse with and influences many other cells
  • one cell influences many others

Physiology (13 decks)

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