Chapter 4 Flashcards
What is a promotor?
A region of DNA that initiates a transcription of a particular gene.
What do promotors indicate?
They indicate what kind of cells should read the gene and when
When are promotors located?
Just before the gene
How many genes does the human genome contain for the voltage gated potassium channel?
40 distinct genes
When did distinct genes for the voltage gated potassiums channel appear? Before what?
They first appeared over a billion years ago. Before the evolution of multicellular organisms
When was the last time the gene variants have changed for the voltage gated potassium channels? Since the evolution of what?
Hundreds of millions of years. Since the evolution of the nervous system in bilateral creatures
Is there a perfect voltage gated potassium channel? If not, how many are there?
No, there’s 40
How do cells make their voltage gated potassium channels?
They can choose to express one or any combination of them to optimize cell function
What are the supporting cells of the nervous system?
- Neuroglia/Glial cells
- Astrocyte
- Microglia
- Oligodendrocytes
What do Neuroglia/glial cells do?
They help traffic nutrients and maintain molecular (ionic) stability. They support many functions of the nervous system
Where are glia found?
They are found all around neurons , and even encapsulate some parts of them.
By how much do glia cells outnumber neurons in the brain?
Somewhere between 2:1 and 5:1
What is an astrocyte?
It is a glial cell that provides physical support and cleans up debris in the brain through phagocytosis
What do astrocytes do?
They control the chemical composition of the surrounding environment and help nourish neurons
What are microglia?
The smallest of glial cells.
What do microglia do?
They provide and immune system for the brain and protect the brain from invading microorganisms
What does an oligodendrocyte do?
Produce myelin sheath, which encapsulates axons
Is sheath continuous?
No, it is a series of segments.
What is the exposed axon called?
The node of ranvier
What do oligodendrocytes form during the development of the CNS?
They form processes shaped something like canoe paddles
How do the paddle shaped processes form myelin?
It wraps itself many times around the segment of an axon and while doing so, produces layers of myelin that make up part of the axon’s myelin sheath
What do excess ions do?
They hug the membrane
Where do myelinated axons come into contact with extracellular fluid?
The node of ranvier: because the axon is naked
Are there many ion channels in myelinated areas? If there is, what happens?
There are almost no ion channels. The ones that are there have no consequences because there is no extracellular fluid outside the membrane
What is saltatory conduction?
The conduction of action potentials by myelinated axons
What do action potentials do in regards to the node of ranvier? What happens to the strength of the signal?
They jump from one node of ranvier to the next? The strength of the signal is regenerated with additional voltage gated Na+ channels
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 acheived? What’s this molecule called?
By the release of a molecule from an axon terminal.
The molecule is called a neurotransmitter.
What kind of effects can a neurotransmitter have?
Simple excitatory or inhibitory effect or a complex modulatory effect on the receiving neuron.