Chapter 7+8 Flashcards Preview

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Flashcards in Chapter 7+8 Deck (33):
1

Two types of electrical signals in neurons

Graded potentials (short-distance)
Action potentials (short- and long distance)

2

What is resting membrane potential?

Neurons exhibit an electrical voltage difference across the membrane

3

4 types of ion channels

Leakage Channel
Voltage-gated Channel
Ligand-gated Channel
Mechanically gated Channel

4

Explain leak gate channels

Always open and are responsible for the resting membrane potential

5

Explain volatage-gated channels.

They open and close in response to changes in the membrane potential

6

Explain Ligand gated channels

Open and close in response to the binding of a chemical messenger to a specific receptor in plasma membrane

7

What is a graded potential: two states

Small deviations from the resting state.
Hyperpolarized (inside more negative)
Depolarized (inside less negative)

8

Where does graded potential mainly occur?

Occurs mainly in the dendrites of sensory neurons and cell body of a neuron

9

What does the sign of the membrane potential always refer to?

Potential inside the cell relative to the potential outside.

10

Resting membrane potential negative or positive?

Negative

11

What is hyperpolerization ?

membrane potential becomes more negative

12

What is depolarization?

less negative membrane or to a positive potential.

13

What is repolarization?

When the membrane returns to resting membrane potential following a depolarization

14

First phase of action potential? Caused by what?

Depolarization. Caused by rapid inrease in permeability to sodium

15

What is the second phase of an action potential? What increases

Repolarization. Potassium permeability increases.

16

Electrical resting state of -70 is due to what?

Unequal distribution of ions across cell membrane
Relative permeability to Na+ and K+

17

What is the refractory period?

Period of time during which no action potential can be generated( right after)

18

What is the absolute refractory period?

No act. pot. can propagate, Bigger diameter axons mean longer time of this period. Happens during depolarization phase plus most of the re polarization phase.

19

What is the relative refractory period?

Immediately after absolute part, possible for second action potential if stimulus is much stronger. Due to increased permeability of potassium channels.

20

How does propagation of nerve impulses move

From dendrites to axon terminal

21

What is the difference between mylinated axon and unmylinated

Unmyelinated has slow process called continuous conduction, myelinated is fast process called salvatory conduction

22

Steps of continuous conduction

Starts when the threshold is reached (–55mV)
Na+ is moving into cytosol and in the ECF (current)
Local current spreads in all directions, passes the axon hillock and reaches initial segment
Action Potential propagates along the axon

23

Three components of saltatory condution

Impulse leaps from node to node (Ranvier node)
Schwann Cell and Ranvier node allow a faster transmission along the axon
Allows to open a smaller number of channels

24

What effect does axon diameter have on conduction speed?

Smaller diameter= faster conduction

25

Two types of signal transmissions at synapses

Electrical synapse:Action potentials conduct directly between adjacent cells through gap junctions
Faster communication and better synchronization
Chemical synapse
Structured with pre- and post-synaptic neurons

26

Transmission steps

Impulse goes until end bulb
Depolarization opens voltage-gated Ca+ channels
Triggers vesicle movement through the layer (neurotransmitters)
Neurotransmitters diffuse through the cleft
Binding of Neurotransmitters with receptors triggering ion flow across post-synaptic layer
Ion flow triggers the post-synaptic potential
If threshold is reached than back to the step one

27

Removal of neurotransmitter occurs how?

Diffusion (pass through synapse cleft)
Enzymatic degradation (specific enzymes break down neurotransmitters)
Uptake by cells (actively transported back into the neuron)

28

What is spatial and temporal summation

Spatial summation results from several pre-synaptic end bulbs. Generally comes from two or more neurons

Temporal summation results of rapid successions of impulse from one neuron

29

Acetylecholine released by what

PNS and CNS (excitatory and inhibitory effects)

30

Ex of amino acid and released from where

Glutamate, asparate (release by CNS – excitatory effect)

31

Biogenic amines

Catecholamines, serotonin (involve in skeletal muscle tone, lymbic system, sensory aspects

32

atp

When ATP breaks down its residue (ADP, AMP) serves as neurotransmitters in CNS and PNS.

33

Nitric Oxide important why?

Important neurotransmitter through the body (serves for vasodilation, smooth muscle relaxation