L1-Nervous Tissue

Question 1

What are the embryonic sources of Neural Tissue for CNS and PNS?

Answer 1

CNS = Neural Tube
PNS = Neural Crest cells

Question 2

Describe basic path of a signal in a motor unit from reception to response.

Answer 2

1. Signal received by AFFERENT, sensory nerve
2. Signal passed to CNS through DORSAL root
3. Signal received by SENSORY neuron in CNS (pass to brain from here)
4. Signal comes back from brain or directly from sensory neuron to the MOTOR neuron.
5. Motor neuron passes signal to EFFERENT, motor nerve in PNS which causes response in effector organ.

Question 3

A common classification of neurons is done by the number of fibers (processes) are present. What are three that we learned about? Describe each briefly.

Answer 3

1. Bipolar neurons: Have 1 dendritic trunk and 1 axial trunk. No dendrites emanating from Soma
2. Pseudo-unipolar: T-shaped. Has one trunk emanating from Soma that branches into separate dendritic and axial branches.
3. Multipolar: Extensive dendritic branching from soma and one long axial branch.

Question 4

What is a distinguishing feature of the axon hillock in a cell body (soma)?

Answer 4

Lack of Nissl bodies.

Question 5

What are Nissl Bodies?

Answer 5

Clumps of Ribosomes. Important because lots of protein synthesis happens in perikaryons

Question 6

Surface outpocketings on dendrites are called what? What is there purpose?

Answer 6

Dendritic spines or thorns are designed to increase surface area available to receive stimuli.

Question 7

What structures are common in terminal boutons in order to maintain energetic balance?

Answer 7

Mitochondria

Question 8

Neurotransmitters are emitted by what presynaptic structure and received by what postsynaptic structure?

Answer 8

Neurotransmitters are carried in and released by synaptic vessicles. Once the neurotransmitters cross the synaptic cleft they are bound by receptors on the postsynaptic membrane.

Question 9

What are three types of synapses? (hint: named according to structures involved)

Answer 9

1. Axodendritic: Signal passes from axon to dendrite. Standard.
2. Axospinous: Signal passed from axon to spinal projection of dendrite.
3. Axoaxonal: axon to axon

Question 10

Nerve signals are generated by changes in electrical potential accross the cell membrane. What type of change results in triggering of an action potential to spread down axon to the presynaptic region? What type inhibits?
-Where is this action potential generated?

Answer 10

If membrane potential becomes LESS negative = DEPOLARIZATION, excitatory. Depolarization must surpass threshold to cause nerve impulse within the Axon Hillock.
If membrane potential becomes MORE negative = Hyperpolarization, Inhibitory

Question 11

Proteins packaged in vesicles in the soma are transported along Microtubules to and from the axion during Anterograde and Retrograde transport. What protein complexes are responsible for each form of transport?

Answer 11

Anterograde: Kinesin
Retrograde: Dynein

Question 12

Schwann cells and oligodendrocytes are both support cells that function in protecting and myelinating axons. Where is each found? What is the major difference b/t the two?

Answer 12

Schwann Cells are found in the peripheral nervous system (PNS) and myelinate one axon. Also have unmyelinated version.
Oligodendrocytes are found in the central nervous system (CNS) and myelinate MULTIPLE axons at once.

Question 13

How do Myelin sheaths speed up signal transduction?

Answer 13

SALTATORY Conduction. Signal jumps from one node of ranvier (interuptions b/t myelin sheaths) to another.

Question 14

What are the 3 protective sheaths in peripheral nerves? What does each surround?

Answer 14

1. Epineurium: Surounds entire nerve, includes fascicles and blood vessels.
2. Perineurium: Surrounds nerve fascicles (bundle of nerve fibers).
3. Endoneurium: Surrounds individual nerve fibers within fascicles.

Question 15

What is a ganglia?

Answer 15

Groups of nerve cells.

Question 16

For Dorsal Root Ganglia...
Function?
Type of neurons found within?
Myelinated?
Prevalence of satellite cells and basal lamina?

Answer 16

• Fun: Dorsal Root Ganglia is a SENSORY ganglia. Takes info from periphery and integrates, passes it to CNS.
• Has pseudo-unipolar neurons.
• Myelinated
• Satellite cells numerous and basal lamina present

Question 17

For Sympathetic Ganglia...
Function?
Type of neurons found within?
Myelinated?
Prevalence of satellite cells and basal lamina?

Answer 17

• Fun: Autonomic (sympathetic) effector. Responsible for fight or flight response. Regulates things such as body temperature and blood pressure.
• Multipolar neurons. Lots of branching
• Mostly unmyelinated-slower response b/c modulating system
• Fewer satellite cells and no basal lamina.

Question 18

What is the function of the CNS support cells ASTROCYTES?

Answer 18

Astrocytes support CNS by binding, with their END-FEET, to blood vessels and facilitating the exchange of nutrients, gases, and metabolites with the CNS. Specifically help maintain the BBB.

Question 19

What is the function of the CNS support cell MICROGLIA?

Answer 19

Macrophage. Cleans up debris through phagocytosis.