Lecture 6 - Nervous Tissue

Question 1

What are the three basic components of a neuron?

Answer 1

Cell body, axon, dendrites

Question 2

Type of neuron where a single process extends from the cell body and then divides into two branches.

Answer 2

Pseudounipolar

Question 3

Type of neuron with irregularly shaped body & more than two cell process: an axon and multiple dendrites

Answer 3

Multipolar

Question 4

What is a Nissl body/substance?

Answer 4

it is the highly developed and easily visible rER of neurons.

Question 5

Where is the initial segment and what is the significance of the initial segment of an axon?

Answer 5

The initial segment of the axon follows the axon hillock and exists as a slight narrowing in the axon. It has the lowest threshold of excitability.

Question 6

What allows orthograde transport down axons?

Answer 6

Kinesis: (+) end directed motor protein

Question 7

Where is the axon hillock located and what does it look like?

Answer 7

It appears at the initial segment of the axon (as it leaves the cell body) and it images as clear area.

Question 8

What allows retrograde transport up axons?

Answer 8

Dynein: (-) end directed motor protein

Question 9

What is the function of dendritic spines?

Answer 9

Structures specialized for synaptic contact

Question 10

What cytoskeletal elements exist in dendritic spines?

Answer 10

Actin, some microtubules, very few neurofilaments (which are 10nm intermediate filaments within neurons)

Question 11

Name for synapse between:

1) axon and dendrites
2) axon and cell body
3) axon and axon
4) axon and dendritic spine
5) dendrite and dendrite

Answer 11

1) axodendritic
2) axosomatic
3) axoaxonic
4) axospinous
5) dendrodendritic

Question 12

What induces fusion of synaptic vesicles with axon terminal membrane?

Answer 12

Depolarization (Ca2+ channels allow influx of Ca2+)

Question 13

How wide is the synaptic cleft?

Answer 13

20nm

Question 14

What structures characterize the presynaptic process?

Answer 14

40-60nm synaptic vesicles & mitochondria

Question 15

List the types of neuroglia present in the CNS. (4 types)

Answer 15

Astrocytes, Oligodendrocytes, Microglia, Ependymal cells

Question 16

What produce myelin sheaths in the CNS? PNS?

Answer 16

CNS: Oligodendroctyes
PNS: Schwann cells

Question 17

Where are astrocytes located relative to mater layers of CNS?

Answer 17

under pia mater

Question 18

What type of astrocytes have granular cytoplasm with short think branches?

Answer 18

Protoplasmic astrocytes (CNS gray matter)

Question 19

What type of astrocytes have long slender, infrequently branches processes?

Answer 19

Fibrous astrocytes (CNS white matter)

Question 20

What is the primary role of astrocytes?

Answer 20

Assist in maintenance of electrolyte balance in CNS & nutrient transport to neurons

Question 21

What is unique about the nucleus of microglia?

Answer 21

It is condensed and elongated.

Question 22

Phagocytic cells in CNS that are derived from monocytes.

Answer 22

Microglia

Question 23

Where are ependymal cells located?

Answer 23

Line neural tubes and ventricles of brain.

Question 24

What is the choroid plexus?

Answer 24

Ependymal cells & associated capillary loops that are modified to produce CSF.

Question 25

From what type of cell do Schwann cells originate?

Answer 25

Neural crest cells

Question 26

What are the three types of nerve fibers? Include speed of signal transduction with each.

Answer 26

Type A: large, myelinated, long internodes (space between nodes of Ranvier), high velocity 15-100 m/s Type B: Smaller diameter, shorter internodes, medium conduction velocity 3-14 m/s Type C: Thin, non-myelinated, slow velocity 0.5-2 m/s

Question 27

What is the name for the connective tissue layer surrounding an entire nerve?

Answer 27

Epineurium

Question 28

What is the name of the sheath surrounding a single neuron (Schwann cell sheath)?

Answer 28

Neurolemma

Question 29

What is the name for the connective tissue layer that surrounds a nerve fiber bundle.

Answer 29

Perineurium

Question 30

What is the name for a group of Schwann cell sheathed axons within the perineurium?

Answer 30

Endoneurium

Question 31

Define ganglion.

Answer 31

Aggregation of nerve cell bodies outside of the CNS

Question 32

What class of neurons typically makes up a DRG?

Answer 32

Pseudounipolar

Question 33

What class of neurons typically makes up a sympathetic root ganglion?

Answer 33

Multipolar

Question 34

What is the size/function of neurons make up the anterior horn?

Answer 34

Large motor neurons that terminate at muscle in motor end plates

Question 35

What is the size/function of neurons make up the posterior horn?

Answer 35

Small nerve cells which receive afferent impulses from sensory nerve cells

Question 36

What is the size/function of neurons make up the lateral horns?

Answer 36

Intermediate size nerve cells which send axons to autonomic ganglia

Question 37

What is the function of Pacini's corpuscles and where are they located? Also, what do they look like? (i.e. What is their general shape?)

Answer 37

Sense vibration, pressure, and tension. Located in subcutaneous tissue of finger pads, peritoneum, tendons and ligaments, around viscera. They are round. Look like an onion.

Question 38

What is the function of Meissner's corpuscles and where are they located?

Answer 38

Touch receptors (mechanoreceptors) that are numerous in dermal papillae of finger pads. Also found in lips, genital skin, edge of eyelids. These are involved in two point discrimination.

Question 39

What makes up the blood-brain barrier?

Answer 39

Cells processes of astrocytes

Question 40

Drugs with what property can cross the blood-brain barrier?

Answer 40

Lipid soluble (lipophilic)

Question 41

What is the size cutoff for substances entering the blood-brain barrier?

Answer 41

>500 daltons restricted