The Brain (Kapitel 3)

Question 1

What is the difference between an ‘anion’ and a ‘cation’?

Answer 1

An ‘anion’ is a negatively charged ion, such as a protein or chloride.

An ‘cation’ is a positively charged ion, such as potassium (k+) or sodium ion.

Question 2

A ‘resting membrane potential’ can be described as?

Answer 2

A difference in electrical potential across the membrane of a nerve cell during an inactive period.

Question 3

Where can the ‘lipid bilayer’ be located, and what does it consist of?

Answer 3

It is the structure of the neuronal cell membrane, which consists of two layers of lipid molecules, within which float various specialized proteins, such as receptors.

Question 4

Explain the function of the ‘sodium-potassium pump’.

Answer 4

The sodium-potassium pump, is the energetically expensive mechanism that pushes sodium (Na+) ions out of the cell, and potassium (K+) ions in.

Question 5

Explain what ‘Action Potential’ is.

Answer 5

Action potentials are very brief large changes in neuronal polarization, which are propagated at high speed along the axon. The information that a neuron sends to its postsynaptic targets is encoded in patterns of these action potentials.

Action potential is created by the movement of sodium ions (Na+) into the cell, trough channels in the membrane.

Question 6

What is the relation and difference between hyperpolarization and depolarization?

Answer 6

Hyperpolarization is an increase in membrane potential (the interior of the neuron becomes even more negative). This is in opposition to depolarization where there is a reduction in membrane potential ((the interior of the neuron becomes less negative). So, depolarization of a neuron brings its membrane potential closer to zero (mV).

Question 7

Name a “Na+ selective channel that opens or closes in response to changes in the voltage of the local membrane potential - it mediates the action potential”

Answer 7

The voltage-gated Na+ Channel

Question 8

Frank Oceans most recently released album is called?

Answer 8

‘Blond’.

Question 9

What is meant by the ‘all-or-none property’ of the action potential?

Answer 9

The amplitude (size) of the action potential is independent of stimulus magnitude. It turns out that information is encoded by changes in the frequency of action potentials rather than in their amplitude.

Question 10

What happens when the ‘treshold’, at about -40Mv, is reached?

Answer 10

Voltage gated Na+ neurons channels open causing a rapid change of polarity (the action potential). Shortly after, the Na+ channels close automatically; gated K+ channels open, repolarizing and even hyperpolerizing the cell (afterpotential).

Question 11

An absolute refractory phase is..

Answer 11

.. a brief period of complete insensitivity to stimuli (following the action potential).

Question 12

What is the difference between ‘conduction velocity’ and ‘saltatory conduction’?

Answer 12

Whereas ‘the conduction velocity’ refers to the speed at which an (un-myelinated) action potential is propagated along the length of the axon, ‘the saltatory (latin, saltare = to leap or jump) conduction’ refers to the conduction that is characteristic of myelinated axons, in which the action potential jumps from one Node of Ranvier to the next.

The saltatory is often way faster, than the conduction velocity itself.

Question 13

Is it true, that an..

Excitatory postsynaptic potential causes hyperpolarization?

Answer 13

No, excitatory postsynaptic potential (EPSP) causes depolarization in the postsynaptic neuron.

Question 14

Is it true, that an..

Inhibitory postsynaptic potential (IPSP) causes hyperpolarization?

Answer 14

Yes, exactly that.

Question 15

The function of inhibitory postsynaptic potential (IPSP) is..

Answer 15

.. To decrease the probability that the postsynaptic neuron will fire an action potential.

Question 16

Complete the following sentence:

“Whether a neuron fires an action potential at any given moment is decided by the balance between..”

Answer 16

”.. The number of extatory and the number of inhibitory signals that it is receiving”.

Question 17

Hvad kalder man en etnisk person, som styrer et fly?

Answer 17

En pilot.

Question 18

Explain the ‘spatial summation’, compared to the ‘temporal summation’ in/on the cellbody.

Answer 18

Spatial (rumlig?) summation refers to the summation at the axon hillock of postsynaptic potentials from across(!) the cell body. If this summation reaches threshold, an action potential is triggered.

Temporal (tid?) summation, on the other hand, refers to the summation of postsynaptic potentials that reach the axon hillock at different times. The closer in time that potentials occur, the more complete the summation.

Question 19

Finish the sentence:

“This summation of potentials from different physical locations across the cellbody is called..”

Answer 19

”.. spatial summation”.

Question 20

Finish the sentence:

“If too much time passes between EPSPs, each will..”

Answer 20

”.. fade away before the next occurs, and the neuron will never fire”.

Question 21

How does glial cells play a role in synaptic transmission?

Answer 21

They increase the strength of the postsynaptic potential, overlying the presynaptic terminal and thereby preventing neurotransmitter from leaking out of the synaptic cleft.

Question 22

What happens during ‘Exocytosis’?

Answer 22

Exocytosis is the fusion of vesicles with the presynaptic membrane, which releases transmitter into the cleft. The process is facilitated by influx of Ca2+. Typically, an action potential causes the ‘exocytosis’ of several hundred vesicles at a time.

Question 23

What is the function of autoreceptors on the presynaptic neuron?

Answer 23

Transmitter bind to autoreceptors in the presynaptic membrane. This helps to adjust the concentration of neurotransmitter in the presynaptic neuron.

Question 24

What is acetylcholine (ACh)?

Answer 24

A neurotransmitter; produced and released by parasympathetic postganglionic neurons, by motorneurons, and by neurons throughout the brain.

Question 25

What is a ‘ligand’?

Answer 25

A substance that binds to recepter molecules, such as those on the surface of the cell.

Question 26

Explain the difference between a ‘endogenous ligand’ and a ‘exogenous ligand’?

Answer 26

A endogenous ligand, is any substance made within the body, that selectively binds to type of recepter that is under study.

The same is true for a exogenous ligand - only, that this comes from outside the body (could be a drug or poisen like ‘Curare’ or ‘Bungarotoxin’).

Question 27

Hvilket instrument spiller Bo Møhl i sin fritid?

Answer 27

Trommer.

Question 28

Decribe the difference / relation between an ‘agonist’ and an ‘antagonist’? (Here in a biological frame.. the concept is also known from theater and literature).

Answer 28

Molecules, such as muscarine and nicotine that act like a neurotransmitter at a receptor, are called agonists of that transmitter. Conversely.. molecules that interfere with or prevent the action of a neurotransmitter - in the manner that curare or bungarotoxin blocks the action of ACh - are called antagonists.

Question 29

Why would it be nice to dream like Otto Loewi?

Answer 29

.. You could win the Noble Prize.

Question 30

What is the role of ‘G proteins’?

Answer 30

A class of proteins that reside next to the intracellular portion of a receptor and that are activated when the receptor binds an appropriate ligand on the extracellular surface. (see p. 81 for illustration).

Question 31

What is meant by ‘degradation’ in the synaptic cleft?

Answer 31

The chemical breakdown of a neurotransmitter into inactive metabolites (thus preventing, for example ACh from starting a false message at another neuron).

Question 32

Explain what happens at ‘reuptake’.

Answer 32

It is the process by which released synaptic transmitter (ex. Norepinephrine, dopamine, serotonin) molecules are taken up and reused by the presynaptic neuron, thus stopping synaptic activity.

Question 33

There are four different types of synaptic connections (p. 82). Can you name the four?

Answer 33

1. Axo-dendritic
2. Axo-somatic
3. Axo-axonic
4. Dendro-dentritic

Question 34

What is ‘ectopic-transmission’ between neurons?

Answer 34

Cell-cell communication based on release of neurotransmitter in regions outside traditional synapses.

Question 35

Can you give an example of a ‘neural chain’?

Answer 35

A good example is the basic circuit for the stretch reflex. It consists of a sensory neuron, that communicates with a motor neuron. The Axons involved have a large diameter and are myelinated.. Thus the very rapid response.

Question 36

Epilepsy is marked by?

Answer 36

.. Major sudden changes in the electrophysiological state of the brain, that are also referred to as seizures. (Watch out: Not to be misunderstood with a stroke, that is something else entirely!)

Question 37

Whats meant by ‘Convergence’ and ‘Divergence’?

Answer 37

Convergence, is the phenomenon of neural connections in which many cells send signals to a single cell. With, Divergence, its sort of the other way around.. Here one cell sends signals to many other cells.

Question 38

What does ‘ERP’ stand for?

Answer 38

ERP stands for event-related potential. Averaged EEG recordings measuring brain responses to repeated presentations of a stimulus. Components of the ERP tend to be reliable because the background noise og the cortex has been averaged out.

Question 39

What happens in ‘Kindling’?

Answer 39

Kindling is a method of experimentally inducing an epileptic seizure by repeatedly stimulating a brain region.