L04 Flashcards
What is a promoter?
A region of DNA that initiates transcription of a particular gene. They indicate what kind of cells should read the gene and when.
How many genes does the human genome have for voltage-gated potassium channels?
40, each cell can choose to express one or any combination of them to optimize cell function.
When did voltage-gated potassium channels appear in history?
Over a billion years ago
Have voltage-gated potassium channels changed since their apparition?
A little, but not really. Most of their gene variants have been conserved for hundreds of millions of years, meaning they haven’t changed much in that time - since the evolution of the nervous system in bilateral creatures.
What is an astrocyte?
A glial cell that provides physical support and cleans up debris in the brain through phagocytosis. They control the chemical composition of the surrounding environment and help nourish neurons.
What is a microglia?
It is the smallest of the glial cells. They provide an immune system for the brain and protect the brain from invading microorganisms.
What is a oligodendrocyte?
A glial cell that produce the myelin sheath, which encapsulates axons. The sheath is not continuous; it is a series of segments.
How do oligodendrocytes form myelin sheath?
During development of the CNS, oligodendrocytes form processes shaped like canoe paddles. Each of those processes then wraps itself many times around a segment of an axon and, while doing so, produces layers of myelin that make up part of the axon’s myelin sheath. A single oligodendrocyte forms many myelin sheaths segments on adjacent axons.
What is the only place where a myelinated axon comes into contact with extracellular fluid?
At the node of Ranvier, where the axon is naked
What is saltatory conduction?
The conduction of action potentials by myelinated axons.
What is a synapse?
A junction between the axon terminal of the sending neuron and the cell membrane of the receiving neuron.
How is the communication across the synapse achieved?
By the release of neurotransmitters from an axon terminal
What are the possible effects of neurotransmitters?
They can have a simple excitatory or inhibitory effect or a complex modulatory effect on the receiving neuron.
What are synaptic vesicles?
They are vesicles that contain neurotransmitters. They attach to the presynaptic membrane and release neurotransmitter into the synaptic cleft.
What is the presynaptic membrane?
The membrane of the terminal button (the sending cell). This is where neurotransmitters are released from.
What is the synaptic cleft?
The space between the pre- and postsynaptic membranes. It is filled with an extracellular fluid.
What is the postsynaptic membrane?
The membrane of the receiving cell that is opposite to the axon terminal
What does electron microscopy allow us to see?
It allows us to see small anatomical structures (ex: synaptic vesicles and details of cell organelles) using a special electron microscope.
What is an example of a microscope used with electron microscopy?
A transmission electron microscope
What are ligands?
Signaling molecules that bind to the binding site of a protein receptor. Neurotransmitters are ligands.