Lecture 1: Studying the Nervous System Flashcards
What are the primary cell types of all nervous systems?
neurons and glia
What is the point of communication between two neurons called?
synapse
What are the two types of synapses?
chemical and electrical
True or false, nerve cells are remarkably diverse in vertebrate NS, including humans
true
What is the soma?
cell body
Where is the nucleus of a neuron located?
in the soma
Where does protein synthesis occur in neurons?
in the soma
What shape do neurons possess?
highly polarized shape
What is divergence?
neurons innervate a few presynaptic cells to many postsynaptic cells
What is convergence?
neurons innervate many presynaptic cells to fewer postsynaptic cells
What are the types of glia found in the CNS?
astrocytes, oligodendrocytes, and microglia
What do astrocytes do?
help with the blood-brain barrier, buffer ions, and neurotransmitters, and secrete chemicals for synaptogenesis in the CNS
What do oligodendrocytes do?
myelinate neuronal axons in the CNS
What do microglia do?
macrophase activity and secrete cytokines, clear areas following damage in the CNS
What type of glia is found in the PNS?
Schwann cells
What do Schwann cells do?
myelinate certain neuronal axons and participate in recovery and function resulting from neuronal damage in the PNS
What do synaptic endings contain?
synaptic vesicles which contain neurotransmitters that are released during synaptic transmission
What do glial stem cells do?
lead to the production of new glial cells or neurons in response to injury
What do oligodendrocyte precursors do?
give rise to glia
How can you visualize neurons in the CNS and PNS?
can inject fluorescent compounds into neurons and see their processes light up, can stain with markers that stain RNA, proteins etc, to visualize neurons
What’s a neuropil?
a dense tangle of neuronal and glial processes
What does afferent refer to?
towards the CNS
What does efferent refer to?
away from the CNS
What signals can neurons send to each other?
excitatory, inhibitory or modulatory
What are interneurons?
short axons that participate in local circuit function
describe the myotatic/ knee-jerk reflex
- Hammer tap stimulus stretches the tendon, which in turn leads to activation of a sensory receptor on the leg extensor muscle
- The sensory receptor has an afferent axon that excites a motor neuron in the spinal cord and an interneuron
- The motor neuron conducts an AP and synapses onto extensor muscle fibers, causing it to contract
- The interneuron inhibits the activity of the flexor muscle and it relaxes
- Results in leg extending
Describe the intracellular physiological recording
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.
Describe visualizing and monitoring the activity of individual neurons in neuronal circuits
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
What is optogenetics?
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
Describe optogenetic methods used to control electrical activity in nerve cells
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
describe the structural analysis of neural systems
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
Describe the organization of the human NS
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
What is genomics?
analysis of the complete DNA sequence of a species or an individual
What are the advantages of using model organisms?
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)
Describe the Cre/lox system of genetic engineering
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
Describe the CRISPR/Cas9 method of genetic engineering
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
