Neurocytology 1 Flashcards
What are the two divisions of the NS?
The CNS and the PNS.
What is the CNS composed of?
The brain and the spinal cord.
What is the PNS composed of?
Nerves and ganglia.
In the CNS, groups of neuronal cell bodies are called?
Nuclei.
In the CNS, sheets of neuronal cell bodies are called?
Cortices.
In the PNS, groups of neuronal cell bodies are called?
Ganglia.
What are the support cells in the PNS?
1) Schwann cells
2) Satellite cells
What are the support cells in the CNS?
1) Ependymal cells
2) Astrocytes
3) Microglia
4) Oligodendrocytes
The first evidence of the NS is detected when?
The third week of the developing human embryo.
What gives rise to the CNS?
The neural plate.
The _______________ develops into the brain and spinal cord.
The neural tube.
What is the function of the glial cells?
1) Provide guidance to migrating neurons
2) Growth factor support
What does the epithelium of the neural tube give rise to?
1) Neurons
2) Glia
When do neurons stop dividing?
Neurons stop dividing when they differentiate.
What happens when neurons are damaged?
They cannot regenerate.
What are the morphological components of a neuron?
1) Cell body
2) Axon
3) Dendrite
What is the function of a neuron?
The function of a neuron is to receive, conduct, and transmit information.
What are the characteristics of a pyramidal cell?
1) A pyramid shaped cell body
2) A long, slender axon from the base
What are the characteristics of a Purkinje cell?
1) A round cell body
2) A slender axon
3) A HUGE dendritic tree
What are the characteristics of a multipolar cell?
A multipolar cell has 1 axon and multiple dendrites. They generally do NOT extend very far.
What are the characteristics of a bipolar cell?
A bipolar cell has 1 axon and 1 dendrite.
What are the characteristics of a pseudounipolar cell?
The pseudounipolar neuron has an axon that has split into 2 branches.
What is the name of the neurons that carry information from the CNS to the periphery?
Motor neurons.
Motor neurons are _______________ cells.
Multipolar.
In the somatic NS, the cell bodies are located…
In the CNS, which sends down an axon to the target (ex: skeletal muscle).
In the autonomic NS, the first cell is found in the…
CNS, which is called the presynaptic autonomic neuron and synapses with a cell outside of the CNS called the postsynaptic autonomic neuron. Information is then passed from the postsynaptic autonomic neuron to the target (ex: smooth muscle of blood vessels).
What is the name of the neurons that carry information from the periphery to the CNS?
Sensory neurons.
Most of the sensory neurons, are ___________ cells.
Pseudounipolar.
What is the function of a dendrite?
To receive information.
What is the main feature of a dendrite?
A dendrite is extensively branched in order to have a large surface area.
What are the protusions that come off the dendrite branches called?
Dendritic spines.
In an active cell, there are __________ dendritic spines compared to an inactive cell.
Dendritic spines.
What is the function of the dendritic spine?
1) Add more SA to the dendrite
2) Contains proteins that are responsible for the interactions between the presynaptic and postsynaptic cells
What are the 3 different types of receptors?
1) Ion channels
2) Kinase receptors
3) G-protein linked receptors
What is the function of the ion channel?
The ion channel affects the polarity of the membrane.
What is the function of the kinase and the G-protein coupled receptors?
Result in a signal cascade that changes the function of the cell.
The dendritic membrane sums ____________ and ___________ information that reaches the neuron.
Excitatory and inhibitory information.
Information is received at contact points called _______________.
Synapses.
At the axon hillock, there is a ….
High concentration of voltage sensitive ion channels –> lowest threshold for firing APs.
What is the function of the cell body?
To synthesize proteins. These proteins support the axon.
What does the cell body contain?
Nissl bodies.
What are Nissl bodies?
Ribosomes and RER.
Are Nissl bodies found in the axon?
No, they are NOT found in the axon. Therefore, the axon depends completely on the cell body for essential materials, such as proteins.
The morphology of the cell body is similar to the morphology of…
Dendrites.
Where are cytoskeleton elements found?
They are found throughout the neuron, including the axon.
What are 2 different types of axonal transport?
1) Anterograde
2) Retrograde
What is anterograde transport?
From the cell body to the terminal.
What is retrograde transport?
From the terminal to the cell body.
What is the motor for anterograde transport?
Kinesin.
What is the motor for retrograde transport?
Dynein.
What are the two types of synapses?
1) Electrical synapses
2) Chemical synapses
Electrical synapses are similar to…
Gap junctions made of connexons.
What passes through the electrical synapse?
ATP or small signaling molecules to pass from one cell to the next.
What does the chemical synapses consist of?
1) A presynaptic cell
2) A synaptic cleft
3) A postsynaptic cell
What do the synaptic vesicles contain?
Acetylcholine.
What are the features of the postsynaptic membrane?
Contains junctional folds, which are invaginations, and at the shoulders of these folds are receptors for ACh.
What happens at the active zone?
Neurotransmitters are released.
Neurotransmitters are released from vesicles by…
Exocytosis.
What does vesicles release require?
Ca2+ influx.
What is the role of Synapsin 1?
Synapsin 1 will bind the vesicles to the actin filament.
What is Synapsin 1 phosphorylated by?
The Ca2+/ calmodulin dependent protein kinase.
What happens once Synapsin 1 is phosphorylated?
The vesicles are released and move to the active zone.
What regulates the docking and fusing process?
The Ca2+ sensoring proteins.
What happens to transmitters in the synaptic cleft (to get rid of neurotransmitters)?
1) Degraded by enzymes
2) Taken up by the presynaptic terminal
3) Taken up by glia
4) Diffuse away
In some cases, vesicles may be refilled with neurotransmitters…
Without going through the early endosome pathway.
The vesicle membrane is NOT …
Reused indefinitely, therefore it is transported retrogradely to the lysosomes to be degraded.
Growth factors are transported…
Retrogradely and form signaling endosomes, which send signals that impact the function of the neuron.
What is an axo-somatic synapse?
An axon synapses with a cell body.
What is an axo-axonic synapse?
A synapse between 2 axons.
What is a dendro-dendritic synapse?
A synapse between 2 dendrites.
What are synaptic varicosities?
The axon looks like a structure with beads on a string. Important when you want to innervate a large area. Each bead has the ability to release neurotransmitters.
What happens when there is a lesion in the axon of a neuron?
1) The axon starts to shrivel and die
- No proteins are being received from the cell body
2) Chromatolysis
- Nissl substance starts to move to the periphery of the cell and disintegrate
- Growth factors are NOT being transported back to the cell body
