Lecture 8 - Nervous System

Question 1

Which axons are myelinated and which are not always myelinated?

Answer 1

Sensory and motor axons are always myelinated, and autonomic axons are not

Question 2

Which nerves enter through dorsal roots?

Answer 2

Sensory nerves

Question 3

Do synapses occur in the sensory ganglia?

Answer 3

No

Question 4

What type of neurons are the sensory nerves?

Answer 4

Pseudounipolar

Question 5

Where are the central bodies of the motor nerves found?

Answer 5

Ventral horn of the spinal cord

Question 6

Which nerves use the two neuron system?

Answer 6

The autonomic nerves

Question 7

Generally, are autonomic nerves myelinated?

Answer 7

The preganglionic nerves are, and the postganglionic nerves are usually not.

Question 8

Is the preganglionic neuron of the sympathetic nervous system usually short or long?

Answer 8

They are short and synapse with the post-ganglionic neuron right outside the spinal cord. The post-ganglionic neuron is long and reaches the target tissue

Question 9

What tissues do the sympathetic nerves target?

Answer 9

Smooth muscle, cardiac muscle, sweat glands

Question 10

What tissues do the parasympathetic nerves target?

Answer 10

Smooth muscle in viscera, cardiac muscle, sweat glands

Question 11

Where do the parasympathetic pre-ganglionic neurons originate?

Answer 11

Cranial and sacral segments of the brain and spinal cord

Question 12

Is the preganglionic neuron of the parasympathetic nervous system usually short or long?

Answer 12

The pre-ganglionic neuron is long and synapses with the 2nd neuron close or within the target tissue

Question 13

What are the enteric nerves?

Answer 13

Autonomic ganglia located within the gut wall

Question 14

How do the cytoplasms of neurons stain? Why?

Answer 14

They are basophilic due to extensive rough ER (AKA Nissl substance)

Question 15

Where are bipolar nerves found?

Answer 15

Sensory tissues of the ear, eye, nose.

Question 16

Where are multipolar nerves found?

Answer 16

Most common in the autonomic ganglia and in grey matter in the CNS.

Question 17

Where are pseudounipolar nerves found?

Answer 17

Sensory ganglia, both spinal and cranial ganglia

Question 18

Describe the perineurium, endoneurium, and epineurium.

Answer 18

The epineurium surrounds the entire nerve/CT investment, the perineurium surrounds nerve fascicles, and the endoneurium surrounds individual axons/supporting cells

Question 19

Are peripheral nerve axons myelinated?

Answer 19

Yes, all of them

Question 20

What are Schmidt-Lanterman incisures?

Answer 20

Interruptions in the myelin sheath that allow for communication between the axon and the Schwann cell

Question 21

How does the myelin sheath stain?

Answer 21

The high lipid content is usually lost in preparation, but residual proteins may remain and can stain with eosin. This residual shit is called NEUROKERATIN.

Question 22

What are the three types of PNS ganglia?

Answer 22

sensory, autonomic, enteric

Question 23

Where do sensory ganglia reside? Do they contain synapses? What is the cell type?

Answer 23

Reside close to the spinal cord in dorsal roots. No synapses, pseudounipolar

Question 24

Compare histological differences between sensory and autonomic ganglia.

Answer 24

Sensory ganglia have central nuclei and a ring of satellite cells, and no synapses. Autonomic ganglia have eccentric nuclei, dispersed satellite cells, and abundant synapses.

Question 25

What are Auerbach’s/myenteric and Meissner’s/submucosal ganglia? How are they identified histologically?

Answer 25

These are enteric ganglia. Auerbach’s are located between muscle layers of the gut wall. Meissner’s are located within submucosa. They can be seen as interposed between circular and longitudinal smooth muscle layers of the gut wall

Question 26

What is unique about bouton en passant?

Answer 26

They are specialized nerve cells in the smooth muscle that release neurotransmitter at far distances from target and rely on diffusion

Question 27

What is Walkerian/anteretrograde degeneration?

Answer 27

Degeneration of nerves distal to the site of an injury.

Question 28

Can Nissl bodies be seen in the axon hillock?

Answer 28

No they are not present there

Question 29

What is a mesaxon?

Answer 29

Its the place where the Schwann cell plasma membrane engulfs an axon and comes together (like if you held a soda can, the part where the tips of your fingers touched)