Chapter 3

Question 1

What type of symmetry does the brain have?

Answer 1

Bilateral symmetry.
Each side receives information from the opposite side –> contralateral

Question 2

What is the outermost section of the brain called, and how are they organized?

Answer 2

Cortex –> neurons organized in cortical columns that are perpendicular to the layers. There are 6 layers with unique neurons.

Question 3

How do cortical regions communicate with each other?

Answer 3

Via axon tracts.

Question 4

What are the components of a synapse?

Answer 4

• Presynaptic neuron
• synaptic cleft
• postsynaptic neuron

Question 5

What contains the NT in the presynaptic neuron, and how do they exit the cell?

Answer 5

Vesicles and exocytosis

Question 6

How do synapses relate to neuroplasticity?

Answer 6

In neuroplasticity, the cells remain the same. The configuration of the synapses is what changes in response to environmental stimuli. Dendritic spines can be rapidly altered, facilitating remodeling of neural connections.

Question 7

What is the name of the cone-shaped area of the cell body where the action potential is initiated and is also the site of integration?

Answer 7

Axon Hillock

Question 8

What is axonal transport?

Answer 8

Movement of materials within the axon via motor proteins.

Question 9

What are the two types of axonal transport?

Answer 9

Anterograde - supplies from cell body –> axon terminals
Retrograde - messages from axon terminals –> cell body

Question 10

Differences between axons and dendrites

Answer 10

Axon - 1 per cell, myelin, axon hillock, can be very short or very long, uniform until the start of terminal branching

Dendrites - many per cell, no axon hillock, shorter than axons, thinner towards end, no myelin

Question 11

What is neurophysiology?

Answer 11

The study of electrical and chemical processes in neurons.

Information flows within neuron through electrical signals and between neurons using chemical signals.

Question 12

What is the membrane potential?

Answer 12

More negative on the inside of the cell than in the intracellular matrix –> polarized

There are more anions inside of the neuron

Question 13

What is the resting membrane potential?

Answer 13

-65 mV

Question 14

What are the fluids in and out of the cell called, and what separates them?

Answer 14

The intracellular fluid and the extracellular fluid which is separated by the phospholipid bilayer

Question 15

What are the 4 things that work to maintain the resting membrane potential?

Answer 15

• Sodium potassium pumps
• Selectively permeable ion channels
• Diffusion
• Electrostatic forces

Question 16

How do selectively permeable ion channels help maintain the resting membrane potential?

Answer 16

Potassium channels are open all the time and allow ions to flow into and out of the cell.

K+ is more concentrated inside the cell

Question 17

How do electrostatic forces/pressure help maintain the resting potential?

Answer 17

Opposites attract and like charges repel, which makes ions move in certain directions.

Question 18

How does diffusion help maintain the resting membrane potential?

Answer 18

Ions passively move through selectively permeable channels from an area of high concentration to an area of low concentration.

Question 19

How does the sodium-potassium pump help maintain the resting membrane potential?

Answer 19

The sodium-potassium pump uses ATP to actively pump 2 atoms of K+ into the cell and 3Na+ out of the cell.

Question 20

Explain when K+ is at its equilibrium potential

Answer 20

K+ is more concentrated inside the cell, so it wants to move out via diffusion; however, the electrostatic forces attract it to the negatively charged inside of the cell.

When the diffusion and electrostatic forces are equal, the membrane potential is approximately -65 mV. Sodium-potassium pumps help keep all this in balance.

Meanwhile, Na+ is clustered close to the membrane on the outside of the cell, as it’s attracted to the cell’s negative charge, but it can’t come in cause the channels are closed.

Question 21

What is an action potential?

Answer 21

A rapid electrical signal that travels along the axon of a neuron. They originate in the axon hillock.

Question 22

What are hyperpolarization and depolarization?

Answer 22

Hyperpolarization: Further decreasing the potential of the neuron by increasing the negative charge inside. Going from -65mV to -70mV

Depolarization: Increasing the potential of the neuron. Making it less negative. Going from -65mV to -50mV.

Question 23

What is the normal pattern that charge follows when you depolarize a neuron?

Answer 23

The potential is said to be local –> bc it spreads passively from the point of stimulation.

The response diminished as you get further from the source.

The response is graded –> the stronger the stimulus, the stronger the response.

Question 24

What is the threshold potential of a neuron and what happens when you reach it?

Answer 24

• (-)40 mV
• An action potential is started

Question 25

What are some characteristics of an AP?

Answer 25

- Not graded --> it's all or nothing and doesn't vary in size - Doesn't diminish --> full strength all the way down the axon - Applying a stronger stimulus doesn't change the shape of the action potential, it just produces more of them

Question 26

Explain what happens after the neuron reaches -40mV (threshold potential).

Answer 26

- At this potential, the voltage-gated sodium ion channels are opened, - This allows for the flow of sodium ions into the cell, which brings the membrane potential to +40mV - This is when an action potential is triggered

Question 27

Explain what happens after an action potential is fired at +40mV

Answer 27

- Voltage-gated potassium channels open - K+ ions rush out of the cell, lowering the membrane potential down to -70mV - This is called the after potential, in which the membrane is hyperpolarized - After this all voltage gates channels are closed and the neuron returns to its resting potential

Question 28

How is the action potential triggered in the next node of ranvier?

Answer 28

The Na+ in the previous node of Ranvier diffuses to the next node of Ranvier, depolarizing it enough to reach the threshold potential.

Question 29

What are the types of refractory periods?

Answer 29

- Absolute refractory period (right before, during, and immediately after AP) - no new AP can be fired - Relative refractory period (after AP through after after potential) - AP can be fired if the signal is strong enough

Question 30

Why can't the neuron fire when it's in its absolute refractory period?

Answer 30

Because the Na+ channels are already open, a new AP can't be fired.

Question 31

What happens to the axon segment left behind after the axon potential?

Answer 31

It enters the refractory period?

Question 32

How does the myelin help propagate the AP?

Answer 32

It stops ions from leaving and shoots ions to the next node. This is called saltatory conduction as the potential jumps from node to node.

Question 33

Why are nodes of Ranvier needed?

Answer 33

If they weren't there, the signal wouldn't be strong enough to reach the end of the axon.

Question 34

What is the disorder where neurons become demyelinated called, and how does it work?

Answer 34

Multiple Sclerosis The body's immune system produces antibodies that attack the myelin, altering conduction of AP. Symptoms depend on which axons are attacked.

Question 35

How does neurotransmission look in the presynaptic neuron?

Answer 35

The AP reaches the axon terminals, which open voltage-gated Ca+ ion channels. Ca2+ rushes into the cell. V SNARES (attached to vesicle) and T SNARES ( attached to membrane) become docked Ca2+ binds to synaptotagmin Synaptotagmin catalyzes exocytosis by binding to SNAREs and plasma membrane.

Question 36

What happens after NT leaves the presynaptic neuron?

Answer 36

NTs are released into the synaptic cleft and bind to receptors in the postsynaptic neuron, where they cause small changes in the membrane potential.

Question 37

What are the different ways in which the NT is removed from the synaptic cleft?

Answer 37

- Enzymes - Diffusion - Reuptake through transporters

Question 38

What are some animal toxins that can block neural transmission?

Answer 38

- Tetrodotoxin (TTX) and Saxitoxin (STX): block voltage-gated Na+ channels - Batrachotoxin: forces Na+ channels to stay open - Botulinum toxin (Botox) and tetanus toxin: inhibit neural transmission by cutting up SNARE proteins and stopping exocytosis.

Question 39

How is it determined if the postsynaptic neuron will fire?

Answer 39

The binding of NT to the receptors causes local (spreads passively) graded changes in the membrane potential of the postsynaptic neuron. A neuron receives synapses from hundreds of neurons. The addition of all of these potentials determines whether the neuron will fire (if the threshold reaches the axon hillock it generates an AP)

Question 40

What are the brief changes produced in the postsynaptic neuron called?

Answer 40

Post-synaptic potentials (PSP)

Question 41

What is a EPSP and what does it cause?

Answer 41

Excitatory postsynaptic potential Caused depolarization of the postsynaptic neuron, which makes the neuron more likely to fire. This is accomplished as positive ions are let into the cell.

Question 42

Which is the most common NT that causes EPSP?

Answer 42

Glutamate

Question 43

What are IPSP and what does it cause?

Answer 43

Inhibitory postsynaptic potential Causes hyperpolarization of the postsynaptic neuron, which makes it more negative and less likely to happen. Negatively charged ions (Cl-) enter the cell.

Question 44

What is the most common NT that causes IPSP?

Answer 44

GABA

Question 45

What are spatial summation and temporal summation?

Answer 45

Spatial summation: summation of input across space at the same time. Temporal summation: Adding stimulation at one spot across time. One input is not enough; the second input builds off the first one, and the third one builds off the other two combined.

Question 46

What are ligands?

Answer 46

They fit receptors exactly and activate or block them

Question 47

What is the difference between an endogenous ligand and an exogenous one?

Answer 47

Endogenous ligands are produced inside the body. They include things like hormones and NT. Exogenous ligands are produced outside of the body. They include things like toxins and drugs.

Question 48

What are the types of postsynaptic receptors and how do they work?

Answer 48

Ionotropic receptors: Also known as ligand-gated ion channels. When the NT binds to the receptor, it causes the receptor to change shape and allow ions to enter the cell. The NT doesn't enter the cell. Metabotropic receptors: They are composed of 7 transmembrane subunits. When the NT binds to them, it activates G-protein molecules that open nearby channels or cause biochemical reactions in the cell. Metabotropic receptors utilize second messenger system --> 1st messenger is NT and 2nd one is G protein. The second messenger amplifies the effects of the first messenger and can initiate a greater change in membrane potential.

Question 49

What are the receptors that regulate the quantity of NT released into the synaptic cleft called?

Answer 49

Autoreceptors They are located in the presynaptic neuron, and they can stop neurotransmission by stopping exocytosis.

Question 50

How do other synapses regulate NT release?

Answer 50

Axo-axonic synapses - One axon attaches to another one, near the axon terminal, and regulates how much NT is released from the terminal. Dendro-dendritic contacts also facilitate the coordination of activities (not very common). Retrograde synapses - use gases to signal from the dendritic postsynaptic neuron to the axon terminal of the presynaptic neuron to release more NT.