Lecture 1: Studying the Nervous System

Question 1

What are the primary cell types of all nervous systems?

Answer 1

neurons and glia

Question 2

What is the point of communication between two neurons called?

Answer 2

synapse

Question 3

What are the two types of synapses?

Answer 3

chemical and electrical

Question 4

True or false, nerve cells are remarkably diverse in vertebrate NS, including humans

Answer 4

true

Question 5

What is the soma?

Answer 5

cell body

Question 6

Where is the nucleus of a neuron located?

Answer 6

in the soma

Question 7

Where does protein synthesis occur in neurons?

Answer 7

in the soma

Question 8

What shape do neurons possess?

Answer 8

highly polarized shape

Question 9

What is divergence?

Answer 9

neurons innervate a few presynaptic cells to many postsynaptic cells

Question 10

What is convergence?

Answer 10

neurons innervate many presynaptic cells to fewer postsynaptic cells

Question 11

What are the types of glia found in the CNS?

Answer 11

astrocytes, oligodendrocytes, and microglia

Question 12

What do astrocytes do?

Answer 12

help with the blood-brain barrier, buffer ions, and neurotransmitters, and secrete chemicals for synaptogenesis in the CNS

Question 13

What do oligodendrocytes do?

Answer 13

myelinate neuronal axons in the CNS

Question 14

What do microglia do?

Answer 14

macrophase activity and secrete cytokines, clear areas following damage in the CNS

Question 15

What type of glia is found in the PNS?

Answer 15

Schwann cells

Question 16

What do Schwann cells do?

Answer 16

myelinate certain neuronal axons and participate in recovery and function resulting from neuronal damage in the PNS

Question 17

What do synaptic endings contain?

Answer 17

synaptic vesicles which contain neurotransmitters that are released during synaptic transmission

Question 18

What do glial stem cells do?

Answer 18

lead to the production of new glial cells or neurons in response to injury

Question 19

What do oligodendrocyte precursors do?

Answer 19

give rise to glia

Question 20

How can you visualize neurons in the CNS and PNS?

Answer 20

can inject fluorescent compounds into neurons and see their processes light up, can stain with markers that stain RNA, proteins etc, to visualize neurons

Question 21

What’s a neuropil?

Answer 21

a dense tangle of neuronal and glial processes

Question 22

What does afferent refer to?

Answer 22

towards the CNS

Question 23

What does efferent refer to?

Answer 23

away from the CNS

Question 24

What signals can neurons send to each other?

Answer 24

excitatory, inhibitory or modulatory

Question 25

What are interneurons?

Answer 25

short axons that participate in local circuit function

Question 26

describe the myotatic/ knee-jerk reflex

Answer 26

1. Hammer tap stimulus stretches the tendon, which in turn leads to activation of a sensory receptor on the leg extensor muscle
2. The sensory receptor has an afferent axon that excites a motor neuron in the spinal cord and an interneuron
3. The motor neuron conducts an AP and synapses onto extensor muscle fibers, causing it to contract
4. The interneuron inhibits the activity of the flexor muscle and it relaxes
5. Results in leg extending

Question 27

Describe the intracellular physiological recording

Answer 27

intracellular recordings from each of the neurons in the myotatic reflex circuit show the temporal relationships between electrical signals in the circuit: (i) action potential measured in a sensory neuron; (ii) postsynaptic potential recorded in an extensor motor neuron; (iii) postsynaptic potential recorded in an interneuron; (iv) postsynaptic potential recorded in a flexor motor neuron. Such intracellular recordings are the basis for understanding the cellular mechanisms that coordinate the sequence and timing of action potential generation in a circuit, and the sensory receptor and synaptic potentials that trigger these conducted signals.

Question 28

Describe visualizing and monitoring the activity of individual neurons in neuronal circuits

Answer 28

can remove part of the skull to perform calcium imaging via calcium-sensitive dyes that allow you to measure changes in calcium from neurons as calcium can trigger neurotransmitter release, providing various stimuli that can measure calcium change as you can see which neurons are important for visualizing. when stimuli are in a certain orientation, it leads to the activation of certain neurons, can see this in graphs that show the change in fluorescence, spikes mean optics are in a preferred orientation and neurons are being activated

Question 29

What is optogenetics?

Answer 29

A technique for controlling the communication between neurons. Genes for light-sensitive proteins (e.g., opsins) are introduced into certain neurons to monitor and control their activity in response to light signals. these genes are often found in algae or bacteria and they’re transgenically expressed into a protein to activate/inactivate neurons

Question 30

Describe optogenetic methods used to control electrical activity in nerve cells

Answer 30

Channel rhodopsin is a light-activated cation channel, light of appropriate wavelength opens the channel and cations can enter the cell of the neuron, in response to blue light, the cell is polarized and we see neuron firing (triggers APs)
Halorhodopsin is a light-activated chloride transporter, activated by green light, and chloride is transported into the cell of interest, this silences the AP, therefore you can control electrical activity via light and understand how neurons communicate in the neural circuit

Question 31

describe the structural analysis of neural systems

Answer 31

lesion studies reveal the direction of information flow and specific genes can be labelled via transgenic reporters, specific proteins can be labelled via antibody labelling and localizing mRNAs for a particular protein can be labelled by in situ hybridization

Question 32

Describe the organization of the human NS

Answer 32

Internal and external environments lead to the activation of various sensory components in PNS (beyond the brain and spinal cord), sending a signal to CNS (brain and spinal cord) which sends a signal to motor components which have effects of various effectors

Question 33

What is genomics?

Answer 33

analysis of the complete DNA sequence of a species or an individual

Question 34

What are the advantages of using model organisms?

Answer 34

due to their genomes being completely sequenced, especially C. elegans, we can do lots of experiments using their genome due to them having the same genes as humans too (genetic analysis of neural systems)

Question 35

Describe the Cre/lox system of genetic engineering

Answer 35

Ex. The gene of interest is an androgen receptor gene, through genetic engineering, the loxP site is added before and after the 2nd exon, loxP won’t disrupt the androgen receptor gene, but if we apply cre recombinase (not found in mammalian NS, expressed using transgenic methods) its expressed in certain tissues or neurons, using the promoter for nestin gene that’s expressed in the NS, we can express cre recombinase in NS so now if you were to look at something outside the NS, wouldn’t find any recombination but if you look at NS, cre recombinase is expressed bc its under control of nestin gene so cre recombinase recognizes loxP and creates excision that removes exon 2 and this disrupts the androgen receptor gene so you can use the cre/lox system to selectively disrupt this androgen receptor gene inside the NS while it’s undisturbed outside the NS and can do this for other neurons

Question 36

Describe the CRISPR/Cas9 method of genetic engineering

Answer 36

allows you to perform gene editing, the guide RNA (created for a specific region of DNA), recognizes an endonuclease (Cas9) and the DNA it was meant to target, it brings Cas9 to the DNA and makes a cut in the DNA sequence, once dsDNA break made, it will either do simple repair (repairs normally or introduces mutation) or after dsDNA break, apply DNA fragment which has homology to the region where the break was made and if you supply this dna fragment during the repair, get homology-directed repair that results in the dna fragment inserted where the break occurred