Chapter 9- The nervous system (2) Flashcards
Why can’t axons rely on passive diffusion to get elements where they are needed to be?
Because axons are very long
What method of transport do axons rely on?
Axonal transport
What does axonal transport contain?
Contains various cytoskeleton components and motor proteins which act as locomotives, pulling essential elements down the tracks.
What is anterograde?
Transporting substances away from the nucleus
What is retrograde?
Transporting substances towards the nucleus.
What is an axon terminal?
This is where the signal is transmitted to another neuron, or to a muscle.
How does an axon terminal transmit its signal?
It transmits the signal by releasing a chemical called a neurotransmitter.
What is a nerve?
Is a collection of neurons in the PNS
What can a single nerve contain?
Both efferent and afferent fibres.
What is a nerve called in the CNS?
A tract
What are some neutron corrections and clarifications?
1- Not all electrical activity arrives at dendrites
2- Not all neurons have multiple dendrites.
3- Not all neurons have an axon.
Only around half of the cells of the nervous system are neurons. What are the other half?
Neural support cells called glia.
What are the key functions of the glia?
1- Helping to hold neurons in place
2- Supplying oxygen and nutrients to neurons
3- Removing pathogens and dead neurons
CNS glia include:
1- Oligodendrocytes
2- Microglia
3- Ependymal cells
PNS glia include:
1- Schwann cells
2- Satellite cells
In the PNS, what do Schwann cells produce?
Myelin
What does a Schwann cell do?
The Schwann cell membrane repeatedly wraps itself around an axon.
Then it squeezes tight to form a myelin sheath and making it largely non conductive.
A single Schwann cell provides myelin for how many PNS neurons?
Only one PNS neuron
What is the Nodes of Ranvier?
Gaps in the myelin sheath that occur between individual Schwann cells.
This is where the electrical signal is regenerated.
What is an oligodendrocyte?
The functional equivalent to Schwann cells but in the CNS
Unlike Schwann cells, a single oligodendrocyte can do what?
Myelinate multiple axons.
What are astrocytes and what do they do?
Star shaped structures that cover blood vessels in the CNS
They store nutrients
What are satellite cells and what do they do?
Coat the soma of nerve cells in the PNS.
Similar in function to astrocytes in the CNS in that they supply nutrients.
They also act as a protective barrier
What are the microglia and what do they do?
Involved in the CNS.
Involved in injury. They will move to the damage site and will engage in phagocytosis and consume debris and pathogens which will destroy any unwanted substances.
What are the ependymal cells and what do they do?
Line the ventricles of the brain and line the central canal of the spinal cord.
Involved in secretion of cerebrospinal fluid (CSF)- provides a degree of mechanical support. It cushions the spine and brain against trauma.
