Week 2 neuro sl 1-55

Question 1

How thick is the cell membrane?

Answer 1

2 molecules thick, 2 phospholipid molecules thick

Question 2

What is simple diffusion?

Answer 2

Process that doesn’t consume energy

Question 3

What are 4 types of simple diffusion?

Answer 3

1) small uncharged molecules that are relatively lipid souble can diffuse through lipid bilayer (ex. steroid hormone)
2) Small uncharged molecules (ions) can diffuse through water-filled pores
3) Ion channels, some are leaky and ions flow in or out as needed
4) Some ion channels are voltage gated, and they open or close in response to changes in electrical voltage

Question 4

What is active transport for? Give some examples.

Answer 4

-To move substances in and out of cells against gradients, uses metabolic energy, usually ATP
-ex. Endocytosis, exocytosis, phagocytosis

Question 5

What can integral membrane proteins act as regarding the cell membrane?

Answer 5

Act as transporters

Question 6

Why are ion channels important in nervous system?

Answer 6

Because they help produce electrical impulses that transmit information rapidly

Question 7

What is resting membrane potential?

Answer 7

Cells in the body have a potential difference or voltage across membrane

Question 8

Which is more negatively charged? the inside or outside of the cell

Answer 8

The inside is more negatively charged

Question 9

What is the charge in neurons?

Answer 9

It’s -70mV

Question 10

Why are voltage gated ion channels important for electrical activity in axons?

Answer 10

Because when the channels open, they can change the membrane potential of the cell, which is needed to conduct an electrical signal in neurons

Question 11

What are action potentials?

Answer 11

Signals that go along nerves, taking signal from one place to another

Question 12

What do neurons recieve send and pass signals on as?

Answer 12

As action potentials

Question 13

What causes action potentials?

Answer 13

Brief discharges (depolarizations) of resting membrane potential, caused by a rapid influx of Na+ through the opening of sodium channels

Question 14

Where do action potentials move once initiated?

Answer 14

Once initiated, they move along axon membrane toward the synapse

Question 15

How do signals travel so far?

Answer 15

Signals must go a long way without weakening, so signals are continously reamplified, using voltage-gated ion channels

Question 16

What is depolarization?

Answer 16

Neuron cell initially -70mV. Stimulation causes positive charges to flow into the cell, and the cell becomes more positive than resting potential.

Question 17

What happens regarding Na+ membrane permeability in channels during action potentials.

Answer 17

Explosive increase in Na+ permeability results in depolarization -70mV to +30mV. Then, Na+ channels close and theres a rapid decrease in Na+ permeability.

The cell must then repolarize to compensate. K+ is positively charged so it will diffuse out of the cell, making the inside of the cell more negative again, back to original resting membrane potential

Question 18

What doe Na+ and K+ pumps do and where?

Answer 18

They work constantly in the plasma membrane, they pump out Na+ that entered the axon during action potentials, and pump in K+ that left.

Question 19

What happens in non myelinated axons action potentials?

Answer 19

Action potential passes smoothly along axon and all parts of membrane are depolarized

Question 20

What happens in myelinated axons action potentials?

Answer 20

Action potential jumps between non-insulated nodes of ranvier, by saltatory conduction, enabling faster transmission and requiring less energy to restore the membrane

Question 21

What does refractory period in axons do?

Answer 21

Ensures the action potential only goes in one direction, down the axon to its end

Question 22

What do action potentials do once they reach the end of the axon?

Answer 22

They stimulate the next cell

Question 23

What happens in pre-synaptic nerve endings?

Answer 23

Presynaptic nerve endings release neurotransmitters that stimulate action potentials in the postsynaptic cell

Question 24

What does the presynaptic neuron end in?

Answer 24

A terminal bouton

Question 25

What separates presynaptic neuron from postsynaptic neuron?

Answer 25

synaptic cleft

Question 26

What is the process of what happens in the presynaptic neuron?

Answer 26

1) Action potentials reach axon terminals 2) Voltage-gated Ca2+ channels open 3) Ca2+ binds to sensor protein in cytoplasm 4) Ca2+ protein complex stimulates fusion and exocytosis of neurotransmitter

Question 27

What occurs on the postsynaptic neuron side?

Answer 27

-Neurotransmitter binds to it's receptor on the dendrite, causing ion channels on post synaptic dendrite membrane to open. These gates are chemically regulated. -Cells are stimulated to produce action potentials

Question 28

What process occurs in the postsynaptic neuron?

Answer 28

1)Chemically (ligand) gated channels open. 2)Na⁺ diffuses inward, causing depolarization (EPSP). 3)EPSP spreads locally and decreases over distance. 4)Voltage-gated Na⁺ and K⁺ channels open. 5)Action potential is conducted.

Question 29

How can we record membrane potential?

Answer 29

Patch clamp technique using microelectrode, records voltage for a certain area of the cell membrane over time

Question 30

What are neuromuscular disorders and how can they be caused?

Answer 30

-delayed relaxation of skeletal muscle after voluntary contraction or electrical stimulation -Can be caused by mutations in muscle Cl- channel -1) channel gates do not open properly -2) repolarization delayed, several action potentials fire instead of just one