Module 1 - Class 2

Question 1

Astrocyte

Answer 1

-Most common type of glial cell in the CNS - their functions are many and diverse, but most of those functions involve regulating the environment of the neurons they surround, including ion concentrations, neurotransmitter levels, and levels of nutrients and wastes. They also control the BBB, and local blood flow in the brain, and some types of astrocytes can actually serve as stem cells for new glia and neurons in the brain.
-Astro = ‘star’ - these cells are named for the number of fine cellular processes they have (these processes are usually smaller and thinner than neurites).

Astrocytes are only found within the CNS.

Question 2

Axon

Answer 2

-Specialized neurites (aka nerve processes) that allow for the propagation of action potentials , transmitting information from the neuronal soma to synapses. There is only ever one axon that leaves a neuron cell body, though axons can branch extensively, creating divergent outputs.
-Axon - relates to ‘axis’, referring to the fact that the axon is usually easily the longest neurite in the cell.

Question 3

Dendrite

Answer 3

-Specialized neurites (aka nerve processes) that allow for the reception of signals from other cells (via synapses), or for the generation of new signals in sensory neurons (via receptor potentials). Inputs generated at dendrites are graded potentials, and are transmitted toward the soma or axon hillock (whichever is closer).
-Dendrite means branch, and is named for the striking resemblance of dendrites to tree branches.

Question 4

Effector Neuron (aka motor neuron)

Answer 4

A neuron which receives synaptic input from other neurons but which makes synapses onto non-neuronal cells (effector cells), such as muscle cells, or secreting cells. If an effector neuron makes synapses onto a muscle cell, it is a motor neuron.

Question 5

Ependymal cell

Answer 5

Glial cells that line the walls of the ventricles and the choroid plexus within the ventricles. Ependymal cells are responsible for secreting CSF (see Lecture 1 defintions) and/or for modifying its composition.

For histology nerds: ependymal cells are a type of simple epithelium.

Question 6

Interneuron

Answer 6

A neuron which is only synaptically connected to other neurons (i.e. it receives synapses from neurons and makes synapses on other neurons).

Inter’ = between.

Question 7

Microglia

Answer 7

Mobile glial cells that are derived from macrophages, and which mostly perform immune functions (e.g. phagocytosis of pathogens, inflammatory responses) within the CNS. They also have roles in synaptic remodelling.

Question 8

Myelin

Answer 8

Lipid- and protein-rich substance produced inside myelinating glia and filling the cytosol where those glia are wrapped many times around axons. Myelin produces electrical insulation properties of these glia

Myelin’s name is derived from a word meaning white, referring to the opaque white colour that the high level of lipid gives this substance.

Question 9

Myelinating cell (oligodendrocyte or Schwann cell

Answer 9

Glial cells which can produce myelin and create myelin sheaths around axons by wrapping around these neurites.

Oligodendrocytes are found in the CNS, Schwann cells in the PNS.

Question 10

Neurite

Answer 10

A long, thin projection emerging from the cell body of a neuron.

Question 11

Neuronal compartment

Answer 11

A term that recognizes the distinct types of neurites in most neurons, but also includes somata and axon terminals which also have distinct anatomy and functions but are not actually neurites.

Question 12

Oligodendrocyte

Answer 12

Myelinating cell in the CNS (see above)

Oligo’ = few ‘dendrite’ = branch - indicating that oligodendrocytes usually myelinate multiple (4-5) axons at once.

Question 13

Satellite cell

Answer 13

Glial cell found in the PNS (specifically in PNS ganglia) which performs many of the same functions as astrocytes.

Question 14

Schwann cell

Answer 14

Myelinating cell in the PNS (see above)

Question 15

Sensory neuron (aka afferent neuron)

Answer 15

A neuron which can perform sensory transduction (i.e. convert some kind of external stimulus into a membrane potential signal). Sensory transduction occurs at sensory neuron dendrites.

n some sensory modalities (e.g. taste, hearing) transduction of the sensory stimulus actually occurs in receptor cells which are not neurons, which then release neurotransmitter onto an ‘afferent neuron’, which transmits that signal into the CNS.

Question 16

Synapse

Answer 16

A location where two neurons make contact and are able to pass physiological information from one cell to another. Most synapses in most nervous systems are chemical (i.e. use neurotransmitters to cross between cells), but electrical synapses do also occur.

Literally translates as ‘clasp’, referring to the close contact between two neuronal compartments in distinct cells