E-Learning modules

Question 1

The severity of mental retardation in children correlates well with differences in:

Answer 1

dendritic spine formation

Question 2

The telencephalon is part of the:

Answer 2

forebrain.

The forebrain or prosencephalon consists of the telencephalon and diencephalon.

Question 3

One of the main functions of the rhombencephalon is:

Answer 3

attention and sleep

Question 4

A type of disease associated with the cerebellum is:

Answer 4

ataxia - a lack of coordination.

Question 5

A brain imaging method that involves injecting a labelled drug is:

Answer 5

positron emission tomography (PET).

Right! Good job! In PET scanning, the subject is given a radioactive drug that emits positrons. Positrons are the antimatter counterparts of electrons and when they collide with electrons, the two mutually annihilate and emit gamma rays. It is the gamma rays that are detected by the scanner.

Question 6

A peak in the folding of the cortex is known as a:

Answer 6

gyrus.

The peaks in the folding of the cortex are called gyri (singular = gyrus) and the troughs, sulci (singular = sulcus)

Question 7

The part(s) of a neurone specialized for the receipt of information is(are) the:

Answer 7

dendrites.

Question 8

A type of glial cell that myelinates neurones in the CNS is the:

Answer 8

oligodendrocyte.

Question 9

The “crossing over” of neuronal pathways such that the right side of the brain controls the left side of the body is known as:

Answer 9

decussation.

The word chiasm is sometimes used to describe a place where a decussation occurs.

Question 10

Which of the following components of the neuronal cytoskeleton is an actin polymer?

Answer 10

microfilaments.

Microtubules are polymers of tubulin.

Question 11

What contains the pons and medulla?

Answer 11

brain stem

Question 12

what does the thalamus do?

Answer 12

controls input to the cortex, location in the centre of the brain.

Question 13

where does motor information leave the spinal cord?

Answer 13

ventral root

Question 14

where is the cerebellum located?

Answer 14

in the rhombencephalon.

Question 15

where does sensory information enter the spinal cord?

Answer 15

dorsal root

Question 16

How does TTX act?

Answer 16

TTX targets and blocks the voltage-gated sodium channel, one of the proteins at the heart of the action potential. Without functioning sodium channels, signals are not transmitted along axons, muscles do not contract, cardiac arrhythmias occur

Question 17

make notes on Na channel structure

Answer 17

yh

Question 18

Organisms that synthesise tetrodotoxin include:

Answer 18

bacteria.

Remember that whilst puffer fish use tetrodotoxin for defence, they get it from symbiotic bacteria.

Question 19

The voltage sensor of the voltage-gated sodium channel is located in the:

Answer 19

fourth transmembrane domain

Question 20

What is the pore-lining domain?

Answer 20

The pore lining domain is a “membrane dipping” segment between the 5th and 6th transmembrane domains. The four pseudo-subunits each contribute their pore lining domain to form the lining of the channel.

Question 21

An example of an ion that is biochemically, but not physiologically useful in neurons is:

Answer 21

Mg2+

Question 22

The rate of diffusion of a molecule is described by:

Answer 22

Fick’s law.

rate of diffusion =
-D.A.concentration gradient.

where D is the diffusion coefficient and A is the area of the interface.

Question 23

The movement of ions through channels in the cell membrane:

Answer 23

is determined by the electrochemical gradient.

Remember that there are two separate forces governing the movement of ions through the membrane. The first is the concentration gradient (ions will tend to move down a concentration gradient), the second is the charge across the membrane (ions will tend to move to areas of opposite charge). Together, these are termed the electrochemical gradient

Question 24

What is the electrochamical gradient?

Answer 24

Remember that there are two separate forces governing the movement of ions through the membrane. The first is the concentration gradient (ions will tend to move down a concentration gradient), the second is the charge across the membrane (ions will tend to move to areas of opposite charge). Together, these are termed the electrochemical gradient

Question 25

Nicotinic acetylcholine receptors are:

Answer 25

pentamers

Question 26

“Red-tide” shell fish poisoning is caused by dinoflagellates that produce a blocker of voltage-gated sodium channels. This toxin is:

Answer 26

saxitoxin.

A “red-tide” is when the concentration of the dinoflagellates becomes so high, they turn the water red. Saxitoxin is produced by the dinoflagellates, which are then eaten by shellfish. When the shellfish are consumed by humans during a “red-tide”, the concentration of saxitoxin in the shellfish can be at fatal levels.

Question 27

In response to a stimulus above the threshold potential, the size of a neuronal action potential:

Answer 27

is independent of the stimulus size

Question 28

Where is the voltage sensor on a Na channel.

Answer 28

The voltage sensor is comprised of the fourth transmembrane domain from each of the four pseudosubunits. These transmembrane domains are charged, and so move in reaction to the membrane potential changing.

Question 29

The inactivation gate of the voltage gated sodium channel is also known as the:

Answer 29

h gate

Question 30

The diffusion of ethanol through a cell membrane depends on:

Answer 30

the concentration gradient for ethanol across the membrane

Ethanol is uncharged and therefore is not influenced by the electrical field.

Question 31

Voltage gated sodium channels are blocked by:

Answer 31

local anaesthetics
Blocking sodium channels means that action potentials cannot be transmitted, thereby stopping pain sensing neurones from sending signals to the brain.

Question 32

The equation above is the Goldman-Hodgkin-Katz (GHK) equation.
In this equation PK denotes the:

Answer 32

permeability of K ions

Question 33

what is the nernst equation?

Answer 33

describes electrical gradient and chemical gradient, whether they are in balance.

examples on E learning

Question 34

describe multiple sclerosis.

how do you test for it?

Answer 34

loss of myelin from CNS neurones.

A simple test that can indicate MS is the Visual Evoked Potential (VEP) test. This is similar to an EEG, except that it is stimulated brain activity, rather than spontaneous activity, that is measured. In a VEP test, electrodes are placed on the scalp and the patient is shown a checkerboard pattern. The electrical activity that this stimulus provokes is picked up by the electrodes and recorded. In patients with MS, there is a delay in the response. This is because demyelinated neurones conduct slower than normal.

MRI is a better test but more expensive.
MRI scans can reveal the presence of sclerotic plaques in the brain and spinal cord (yellow arrows on the figure below). These are hallmarks of MS and can help distinguish it from disorders with similar clinical symptoms.

Question 35

what is linked to the development of multiple sclerosis?

Answer 35

vitamin D, not synthesised in the body, only available from sunlight.

Question 36

In dendrites, current is attenuated but in axons it is not. This difference most strongly depends on:

Answer 36

higher density of voltage-gated channels in axons than dendrites

Question 37

In the cable equation V=V0e-x/λ, λ is the distance over which V drops to what fraction of V0?

Answer 37

37%

Question 38

Which of the following parts of a neuron is covered with myelin?

Answer 38

internode

Question 39

In mammalian neurones, the density of Na+ channels in the nodes of Ranvier is approximately:

Answer 39

10000 /µm2

Question 40

A disease that involves loss of myelin from neurones that innervate skeletal muscle:

Answer 40

Guillain-Barré syndrome.

In Guillain-Barré syndrome the Schwann cells insulating alpha motor neurones are attacked. In Multiple Sclerosis, the immune response is against oligodendrocytes in the CNS.

Question 41

Multiple sclerosis is most common in:

Answer 41

The most common age range is 15-50 years old at diagnosis. Women are two-three times more likely to develop MS than men (true of all autoimmune diseases).

Question 42

what are Autoreceptors?

Answer 42

Autoreceptors are pre synaptic receptors for the neurotransmitter released by the nerve terminal in whose membrane they reside and when activated, these receptors regulate the release of that neurotransmitter.

Usually, this regulation takes the form of inhibition.

Question 43

give a specific example of an autoreceptor.

Answer 43

noradrenaline from cardiac sympathetic neurones.

One very well-characterized example of how a presynaptic autoreceptor works is at sympathetic synapses in the heart. Here, noradrenaline released by sympathetic neurones acts on beta adrenoceptors on cardiac muscle to speed up the heart and increase its force of contraction. On the presynaptic nerve terminal there are Alpha 2 type adrenoceptors (adrenoceptors are receptors for noradrenaline and adrenaline) that act as autoreceptors and regulate noradrenaline release. These alpha 2 receptors are GPCRs that interact with the G protein Gi. The main effect of Gi is to decrease the activity of the enyzme adenylate cyclase, which turns ATP into the intracellular signalling molecule cAMP. Thus the effect of activating the alpha 2 receptors is to decrease the concentration of cAMP in the nerve terminal. As cAMP increases the activity of voltage-gated calcium channels, and thus noradrenaline release, the consequence of activating the alpha 2 autoreceptors is to decrease noradrenaline release.

Question 44

What is a heteroreceptor?

Answer 44

on the presynaptic neurone, responds to a different NT.

Question 45

Give an example of a heteroreceptor.

Answer 45

Acetylcholine Regulates Dopamine Release in the Striatum via presynaptic nicotinic acetylcholine receptors.

These synapses have been intensively researched because a deficit in dopaminergic transmission in the striatum is one of the key problems in Parkinson’s disease, and an excess of dopamine in a different part of the striatum is thought to be involved in some of the symptoms of schizophrenia.

Question 46

what does an alpha in front of a toxin name mean?

Answer 46

it targets nicotinic acetylcholine receptors.

Question 47

describe how nicotinic receptors are regulated.

Answer 47

there are a series of peptides produced in the brain that can interact with nicotinic receptors and change their function. The best-characterized of these proteins, called Lynx1, is thought to be very important in regulating nicotinic receptors during brain development, especially of the visual system.

Lynx1 is a member of a ubiquitous protein superfamily called Ly6: even organisms as simple as C. elegans have genes encoding Ly6 proteins. In the human genome there seem to be 27 genes coding for Ly6 proteins but the function of most of them is unknown.

Question 48

name 3 metabotropic receptors (G protein coupled receptors)

Answer 48

dopamine
GABAb
muscarinic acetylcholine

Question 49

A key component of an electrical synapse is the:

Answer 49

conexin.
Electrical synapses are where neurones or other cells make direct electrical connections with one-another (as opposed to chemical synapses). Conexin is a subunit of the gap junction channel that connects the cytoplasm of electrically synapsed cells together.

Question 50

The fusion of vesicles containing acetylcholine with the presynaptic membrane is mediated by:

Answer 50

SNARE proteins.

SNARE proteins comprise two sets of proteins: the v-SNAREs that are present on the vesicle membrane and the t-SNAREs that are present in the cytoplasmic membrane. When the two bind together, it facilitates vesicle fusion with the membrane. Releasin is a made-up protein and the other two enzymes are involved in acetylcholine synthesis/metabolism.

Question 51

A key protein in the recycling of synaptic vesicles is:

Answer 51

Clathrin forms coated “pits” in the cell membrane, which then facilitate the budding of a coated vesicle into the cytoplasm. Within the cytoplasm, the clathrin coat dissociates from the vesicle and is recycled to the membrane. This process allows membrane from vesicles that have fused with the cytoplasmic membrane to be “recycled” into vesicles. Acetylcholinesterase is an enzyme involved in the metabolism of acetylcholine. t-SNARE is a SNARE protein (involved in vesicle docking) and phospholipase C is an enzyme involved in the IP3 signalling pathway (linked to G protein coupled receptors).

Question 52

The release of acetylcholine at the neuromuscular junction occurs in “packets” of a fixed size. This type of release is described as:

Answer 52

quantal

Question 53

Select a ligand that does NOT bind to nicotinic acetylcholine receptors.

Answer 53

Omega conotoxin

Toxins with an ‘alpha’ at the front of their name are most likely to be ligands at nicotinic acetylcholine receptors (alpha conotoxin and alpha cobra toxin). Lynx is a neuromodulatory peptide that acts on nicotinic acetylcholine receptors in the brain. Omega conotoxin, however, inhibits calcium channels.

Question 54

Select a toxin that destroys SNARE proteins.

Answer 54

Botulinum toxin

Botulinum toxin disrupts neuromuscular transmission. The enzyme components of botulinum toxin are proteases. They cleave the SNARE proteins that are involved in the fusion of neurotransmitter-containing vesicles with the synaptic membrane. This means that ACh cannot be released and results in a (frequently) fatal paralysis. Alpha bungarotoxin acts on nicotinic acetylcholine receptors, omega conotoxin acts on voltage gated calcium channels and tetrodotoxin acts on voltage gated sodium channels.

Question 55

A receptor whose effects are normally inhibitory due to influx of chloride ions is the:

Answer 55

GABAa

The GABAA receptor is a ligand gated chloride channel. Because the equilibrium potential for chloride is close to the resting membrane potential (RMP), increasing permeability to chloride stabilises the RMP and prevents depolarisation.

Question 56

The hobbit uses the amino acid alanine as a neurotransmitter in its spinal cord. At one common type of synapse, alanine is released by the presynaptic nerve terminal and binds to alanine type A receptors on the post-synaptic neurone. Alanine also binds to alanine type B receptors on the presynaptic nerve terminal. Activation of these type B receptors causes negative feedback on alanine release.
What is the most appropriate description for the alanine type B receptors?

Answer 56

autoreceptor.

Good job! A receptor that binds the neurotransmitter released by the neurone in whose membrane it is embedded, is known as an autoreceptor (a less common name is a homoreceptor).

Question 57

An example of a neurotransmitter acting on a heteroreceptor is:

Answer 57

acetylcholine acting on presynaptic nicotinic receptors at a dopaminergic nerve terminal

A heteroreceptor is a receptor that binds a neurotransmitter other than the transmitter released by the neurone in whose membrane the heteroreceptor sits.

Question 58

What is patch clamping?

Answer 58

atch clamp seals can be made on cells in thin slices of brain tissue, or even in whole brains. This type of recording is made by applying positive pressure to the fine glass recording-electrode. A jet of solution comes out of the tip of the electrode and is used like a pressure washer to “blast” debris out of the way as the electrode is pushed into the tissue. In slices, it is sometimes possible to use a microscope to see when the electrode is close to a neuron, but frequently the technique is done “blind” with the neuron hunter relying on changes in electrical resistance to indicate when a cell is under the tip of the electrode. Suction is then applied and recordings can be made just as you would with a cultured cell.

patch clamp gives investigators the ability to measure the activity of ion channels and receptors in a single cell

Question 59

how is reverse transcription PCR an extension of the patch clamp?

Answer 59

Just as patch clamp gives investigators the ability to measure the activity of ion channels and receptors in a single cell, so single cell RT PCR allows them to measure the levels of individual mRNA molecules and thus infer the expression levels of particular proteins.

Question 60

describe RT PCR.

Answer 60

At the end of a patch clamp recording experiment the contents of the cell are sucked into the patch clamp electrode.

The contents of the electrode are then transferred into a test tube for RT PCR.

The first step in RT PCR is the conversion of the mRNAs present in the sample into cDNAs using a reverse transcriptase enzyme. Primers are added for the protein of interest and the corresponding cDNA is amplified and measured using quantitative PCR (qPCR).

Question 61

A technique for measuring the movement of ions across membranes that offers the advantage of simplicity, but lacks spatial and temporal resolution is:

Answer 61

Radioactive ion flux assays cannot distinguish which part of a cell or tissue ions are moving into (poor spatial resolution). They are also slow unless very complicated equipment is used (poor temporal resolution)

Question 62

The fastest events that electrophysiology is capable of measuring occur on the following time scale:

Answer 62

hundreds of µs

Question 63

A dye that selectively binds Ca2+ is:

Answer 63

Fura-2 binds calcium via its negatively charged carboxylic acid groups. Fura-2 AM is a esterified version of Fura-2. It can pass through membranes but cannot bind calcium.

Question 64

You wish to study an ion channel by measuring currents through single channels. You know that for the ion channel you are studying, it is important to keep the cell intact. A suitable mode of the patch-clamp would be:

Answer 64

cell attached
In the cell-attached configuration, the electrode is sealed onto the outside of the cell and the membrane is left intact. In all other types of patch clamp, the membrane is disrupted in some way.

Question 65

When patch clamping in tissue slices, positive pressure is applied to the patch electrode in order to:

Answer 65

remove debris when “neuron hunting”

The jet of solution from the electrode abrades away the tissue debris to allow a pathway to be cleared to a neurone. A second function is to prevent the electrode from becoming blocked.