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BILD 2 - Multicellular Life > Nervous System III > Flashcards

Nervous System III Flashcards

0
Q

I. AP Refractory Period

definition

A

prevents back-firing

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1
Q

Nervous Systems III

parts

A 
I. AP Refractory Period
II. Saltatory Conduction
III. Generator Potentials (GPs)
IV. Chemical Synapses
V. Model Example: Vertebrate Neuromuscular Junction (NMJ)
VI. Postsynaptic Potentials (PSPs)
VII. Summation of PSPs
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2
Q

I. AP Refractory Period

parts

A

A. Absolute Refractory Period (about 1 ms)

B. Relative Refractory Period (2-3 ms)

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3
Q

Absolute Refractory Period

A

about 1ms

VGNaC’s remain inactive about1 ms

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4
Q

Relative Refractory Period

A

about 2-3 ms

still have VGRC’s open (producing the “undershoot”)

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5
Q

II. Saltatory Conduction

parts

A

A. Big axons wrapped in MYELIN

B. AP moves by “jumping” from node to node

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6
Q

Big axons wrapped in myelin

A
  • “insulates”

- open “nodes”along axon allow local ion flux

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7
Q

AP moves by “jumping” from node to node

A

(this is faster for AP conduction along the axon, jumping from node to node

Figure 37.13 Schwann Cells and the myelin sheath
Figure 37.14 Saltatory Conduction

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8
Q

III. Generator Potentials (GPs)

A
  • in sensory neurons
  • transduces physical stimulus (ex. touch) into electrical signal.

ex)
-crayfish stretch receptor neuron- diagram (lots of diagrams)
- stretch muscle (increase length) cause depolarization of Vm in neuron = GP
Figure: Sensory Transduction in the crayfish stretch receptor

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9
Q

IV. Chemical Synapses

parts

A

A. Structure

B. Synaptic Transmission

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10
Q

A. Structure

parts

A
  1. Presynaptic nerve terminal

2. Postsynaptic neuron

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11
Q
  1. Presynaptic nerve terminal
A 
- synaptic vesicles (SVs)
contain neurotransmitter (NT)
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12
Q
  1. Postsynaptic neuron
A

localized high concentration of NT receptors (membrane proteins)
“ligand-gated ion channel”

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13
Q

B. Synaptic Transmission

A
  1. AP invades presynaptic terminal
    - induce “EXOCYTOSIS” of S.V. & release NT
  2. NT diffuses fast across synaptic cleft
  3. NT binds to NT receptors of postsynaptic cell
    - opens internal channels
  4. Ions flow through receptors –>
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14
Q

IV. (Model Example): Vertebrate Neuromuscular Junction (NMJ)

definition

A 
Motor neuron (spinal cord)
--> axon to skeletal muscle

[Motor neuron (in spinal cord) sends axon out to muscle fiber and makes a synapse on it (NMJ)]

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15
Q

IV. (Model Example): Vertebrate Neuromuscular Junction (NMJ)

parts

A

A. Neuromuscular Junction (NMJ) Chemistry

B. Role of Ca++

16
Q

IV. (Model Example): Vertebrate Neuromuscular Junction (NMJ)

A. Neuromuscular Junction (NMJ) Chemistry

A
  1. NT= acetyl choline (ACh)

2. Postsynaptic NT R’s

17
Q
  1. NT= acetyl choline (ACh)
A

a) made in nerve terminal:
choline + acetylCo-A => ACh + Co-A

b) pack into SVs

18
Q
  1. Postsynaptic NT R’s
A

a) Nicotinic AChR, (NAChRs)
b) Ion Channels permeable to cations (K+, Na+)
ACh + nAChR(closed) = ACh-nAChR(open)

19
Q

IV. Vertebrate Neuromuscular Junction (NMJ)

B. Role of Ca++

A
  1. AP arrives in presynaptic nerve terminal, (DEPOLARIZING the Vm)
  2. ⬆️Vm => open VGCaCs in membrane
    => allow Ca+ influx
  3. Ca+ influx => ⬆️ [Ca] in –> induce exocytosis of “docked” SVs
  4. NT release
  5. SV recycled & refilled

Figure: 37.15 A Chemical Synapse
Figure 37.10 Depolarization Can Induce an AP

20
Q

IV. Postsynaptic Potentials (PSPs)

Parts

A

A. Ionic Basis
B. Excitatory Postsynaptic Potentials (EPSPs)
C. Inhibitory Postsynaptic Potentials (PSPSs)

21
Q

IV. Postsynaptic Potentials (PSPs)

A. Ionic Basis

A

e.g. NT opens Rs permeable to Na+; this allows Na+ influx

diagram/graphs

22
Q

IV. Postsynaptic Potentials (PSPs)

B. Excitatory PSPs

A
  1. NT can drive Vm to threshold for AP
  2. Examples: ACh & glutamate
  3. Stimulate presynaptic nerves
    - diagram
23
Q

IV. Postsynaptic Potentials (PSPs)

C. Inhibitory PSPs

A
  1. diagram
  2. E(Na) = +60
    E(K) = -90
    E(Ca) = +50
    E(Cl) = -60
  3. Visual NT’s for IPSPs
    a) ⬆️ Cl- flow –> Cl- in
    => more negative Vm
    b) usually GABA (gamma - amino- butyric acid) & glycine
24
Q

VII. Summation of PSPs

parts

A

A. PSP properties
B. Spatial summation
C. Temporal Summation
D. Integration

25
Q

VII. Summation of PSPs

A. PSP properties

A
  1. Local “graded” responses

2. PSPs not equal to APs

26
Q
  1. Local “graded” responses
A

amplitude proportional to number of ions flowing

–> proportional to R’s opened. (therefore PSPs can be ADDITIVE.)

27
Q
  1. PSPS are not equal to APs
A

a) not all-or-none
b) not actively propagated
i. e. not regenerative

28
Q

VII. Summation of PSPs

B. Spatial summation

A
  1. Multiple synapses / neuron ( > 10^3 / neuron in CNS)
  2. EPSPs arrives simultaneous can add
    (simultaneous EPSPs at multiple synapses can spatially summate to
    reach AP threshold)

Diagram

29
Q

VII. Summation of PSPs

C. Temporal Summation

A

Fire 1 synapse repeatedly & rapidly

Diagram

30
Q

VII. Summation of PSPs

D. Integration

A

diagram

EPSPs & IPSPs co-occurring: IPSPs can prevent EPSPs from driving Vm to threshold

BILD 2 - Multicellular Life (8 decks)

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