Review Questions

Question 1

What is found in greater abundance in the cytoplasm axon than in the neuronal cell body?

Answer 1

Neurotubules (microtubules- transport) & neurofilaments (structural support-intermediate filaments)

Question 2

What is transported within the axon?

Answer 2

Organelles, vesicles, proteins, and cytoskeletal elements

Question 3

What is the general speed of fast and slow axoplasmic transport?

Answer 3

Answer 9. Slow transport is about 0.2-4mm/day, while fast is 20-400 mm/day.

Question 4

What are the presynaptic and postsynaptic densities?

Answer 4

The presynaptic density contains the proteins required for docking and release of vesicles of neurotransmitter. The postsynaptic density contains the receptors and associated regulatory molecules and enzymes.

Question 5

What is an action potential and what ions are responsible for it?

Answer 5

An action potential (nerve signal) is the sudden depolarization of the neuron due to movement of sodium ions through voltage gated sodium channels.

Question 6

Why do action potentials move in one direction and not “double back” on themselves?

Answer 6

After an action potential, the voltage-gated sodium channel inactivates for a period of time, producing a period in which it cannot be activated (absolute refractory period) and preventing the signal from “doubling back”.

Question 7

How does neurotransmitter cross the synapse?

Answer 7

Neurotransmitter crosses by simple diffusion. That is why the synapse must be narrow.

Question 8

What are the possible effects of a nuerotranmsitter on the postsynaptic cell?

Answer 8

Neurotransmitters can be stimulatory (i.e., increase the chances of generating an action potential), inhibitory (decrease the chances of generating an action potential) or modulatory (having some longer term effect on the postsynaptic cell through second messengers).

Question 9

What are the three mechanisms for termination of action of neurotransmitter?

Answer 9

Inactivation of neurotransmitters occurs by reuptake, enzymatic degradation or diffusion away from the synapse (usually to be taken up by glia).

Question 10

What are the two broad types of receptors for neurotrasmitters?

Answer 10

Neurotransmitters bind to ionotropic (ligand-gated ion channels) or metabotropic receptors. The latter type consist of transmembrane proteins that are linked to 2nd messenger systems.

Question 11

What is a Schwann cell?

Answer 11

A Schwann cell is derived from neural crest cells and interacts with axons in the peripheral nervous system. It may simply encase them (as unmyelinated axons) or it may wrap them tightly (as the myelin sheath).

Question 12

What is the process of myelination of peripheral nerve fibers?

Answer 12

Schwann cells interact with specific signals (glycoproteins) on the axon and on their own membranes to wrap plasma membrane around axons. Gap junctions interconnect the wraps of myelin to allow communication within the sheath.

Question 13

What transmembrane proteins would be in high concentration at the node of Ranvier?

Answer 13

There is a high concentration of voltage-gated sodium channels at the nodes of Ranvier (to make them sensitive sites of action potential generation).

Question 14

What is the range of conduction speeds from unmyelinated axons to the fastest myelinated axons?

Answer 14

The range is from

Question 15

What are the connective tissue sheaths of peripheral nerves?

Answer 15

Nerve divided like muscle by connective tissue. The epineurium: surrounds the entire nerve. The perineurium: surrounds individual fascicles of the nerve and the enodneurium surrounds each axon.

Question 16

What are the two types of ganglia?

Answer 16

The two types of ganglia are the sensory and the autonomic ganglia.

Ganglia are a collection of nerve cell bodies outside the CNS

Question 17

What are satellite cells?

Answer 17

Satellite cells surround ganglion cells and maintain proper environment.

Question 18

What is the function of astrocytes?

Answer 18

Astrocytes maintain proper ionic concentrations with nervous system. They support neurons with trophic factors and participate in clearing excess neurotransmitter. They are the origin of the signals that result in the creation and maintenance of the blood-brain barrier.

Question 19

What are the functions of oligodendrocytes?

Answer 19

Oligodendrocytes have several processes that each myelinate a segment of axon.

Question 20

What are the functions of ependymal cells?

Answer 20

Ependymal cells line the ventricles. They do not provide any barrier between the CSF and the brain. However, there are specialized ependymal cells (choroid plexus epithelial cells) that cover capillaries of the choroid plexus and comprise the blood-CSF barrier.

Question 21

What are the functions of microglia?

Answer 21

Microglial cells are phagocytic cells of the CNS and they are involved in immune responses in the CNS

Question 22

What is the blood-brain barrier and what actually comprises the barrier?

Answer 22

The blood-brain barrier is comprised of capillaries of the CNS that have tight junctions and few pinocytotic vesicles. They have specific transport molecules for many things that need to get into the brain, while blocking many things that would be harmful. The foot processes of astrocytes communicate through molecules with the endothelial cells, causing them to assume this form and function.

Question 23

What is the blood-CSF barrier and what actually comprises the barrier?

Answer 23

Choroid plexus epithelial cells form the barrier between the blood in the fenestrated capillaries of the choroid plexus and the CSF. There are tight junctions between these epithelial cells and they only allow certain molecules to pass into the CSF.

Question 24

What is tunica intima?

Answer 24

This consists of simple squamous endothelial cells with basement membrane and some CT and, in most arteries, an internal elastic lamina

Question 25

What is the tunica media?

Answer 25

The tunica media consists of layers of smooth muscle and fibroelastic connective tissue. This layer is more prominent in arteries than veins)

Question 26

Tunica adventitia?

Answer 26

The tunica adventitia consists mostly of connective tissue that blends with the surrounding CT layers. This layer is more prominent in veins. There may be an external elastic lamina separating it from the tunica media, especially in muscular arteries

Question 27

What are vasa vasorum?

Answer 27

Small blood vessels that supply the blood vessel wall

Question 28

What are the features of elastic arteries and where would you find them?

Answer 28

These are the largest arteries, close to the heart. Their wall contains lots of smooth muscle and layers of elastic fibers.

Question 29

What are the features of muscular arteries?

Answer 29

Muscular arteries have a prominent internal elastic lamina in their intima and a media with 4-40 layers of smooth muscle. These include medium and small arteries, which have progressively less elastic fibers and smooth muscle as the artery becomes smaller with branching.

Question 30

What is the structure of arterioles and what do they do?

Answer 30

Arterioles contain ~1-4 layers of smooth muscle in a vey small vessel. These provide the greatest contribution to peripheral resistance (TPR) that is needed to maintain blood pressure.

Question 31

What are met arterioles?

Answer 31

Metarterioles are the smallest arterioles and regulate flow into local capillary beds via contraction of smooth muscle cells that can close off the flow to capillaries. Branch arterioles and capillaries together

Question 32

What are the nervi vascularis?

Answer 32

Nerves that supply blood vessels. may consist of sensory fibers and autonomic nerve fibers.

Question 33

What are the structure of capillaries?

Answer 33

Capillaries consist of a layer of endothelial cells and a surrounding basement membrane. There may be a pericyte within the basement membrane (which can have contractile functions despite the fact that it is not true smooth muscle).

Question 34

What are the three types of capillaries?

Answer 34

There are three types of capillaries. Continuous capillaries are the most common and the endothelial cells are uninterrupted. Transport across these cells has to be either by diffusion, specific transport mechanisms or by pinocytotic vesicles. Fenestrated capillaries have small pores within the endothelial cells, which may or may not be closed by pore diaphragms. These allow for somewhat freer transport. Discontinuous capillaries have large pores and gaps between endothelial cells. They also usually have an incomplete basement membrane. They are the most common lining for sinusoids.

Question 35

Where are the three types of capillaries found?

Answer 35

Continuous: Muscle, brain, lung, bone Fenestrated: GI, endocrine, kidney Discontinuos: liver, bone marrow, spleen

Question 36

Function of post-capillary venule?

Answer 36

Post-capillary venules are the site of significant gaseous/nutrient exchange, as well as the site where most WBCs leave the blood stream to enter the tissues.

Question 37

Vein structure?

Answer 37

Veins have three layers. The intima and media are quite thin and the tunica adventitia is the largest layer. There are bicuspid valves to prevent backflow and some longitudinal smooth muscle in the media.

Question 38

Functions of endothelial cells?

Answer 38

Endothelial cells are important for transfer of nutrients and wastes to and from the interstitial spaces. They are active in the inflammatory response and also have an antithrombogenic (prevent clots) function. They produce and secrete several vasoactive substances including vasoconstricors (Endothelin) and vasodialators (NO).

Question 39

What are Purkinje fibers and what do they look like?

Answer 39

Purkinje fibers are modified cardiac muscle cells that are large and paler staining than regular cardiac muscle cells. These are specialized to conduct impulses from the atria toward the apex of the heart. They run in a sub-endocardial position.

Question 40

Structure of lymphatic vessels?

Answer 40

Lymphatic vessels have thin walls, lined by endothelium, with a connective tissue casing. They share some similarities with small veins in that they have weak walls, with valves. However, they do not contain blood cells.

Question 41

Diameter of RBC

Answer 41

They are around 7.2 micrometers and can be used to measure structures on a microscope slide.

Question 42

What are reticulocytes and about how many should there be in the blood?

Answer 42

Reticulocytes are immature erythrocytes containing some ribosomes (basophilic stippling). They have this appearance for about a day after they are released from the bone marrow. Since about 1% of your RBCs are normally turned over each day, there should be about 1% reticulocytes.

Question 43

What are “azurophilic granules”?

Answer 43

Azurophilic granules are lysosomes that are present in all granulocytes. They can also be seen in monocytes.

Question 44

What is the function of neutrophils?

Answer 44

These are phagocytic cells that react to areas of inflammation and infection and destroy pathogens (esecially bacteria).

Question 45

Appearance of neutrophils

Answer 45

These are multilobed structures (one lobe of which may be a Barr body). Therefore, neutrophils are often called “polymorphonuclear leukocytes”, “polys” or “PMNs”.

Question 46

What is the appearance of a PMNs that is newly released from the bone marrow?

Answer 46

The nucleus has a horseshoe shape, called a band or stab cell. These increase in acute infections (particularly bacterial), where polys are being released as rapidly as possible.

Question 47

Eosinophil function and purpose?

Answer 47

Eosinophils have a bilobed nucleus. The specific granules have a red-orange appearance with a “cat eye” shape. They contain and release major basic protein in parasitic infections and allergic reactions.

Question 48

Appearance of basophils?

Answer 48

Basophils are very rare in the blood. They contain dark blue/black specific granules that contain heparin, histamine and slow-reacting substance of anaphylaxis. In this regard they are similar to mast cells.

Question 49

Smallest leukocyte?

Answer 49

Lymphocytes are the smallest leukocytes. They are the 2nd most abundant type and are important in immune reactions.

Question 50

What are the largest leukocytes?

Answer 50

Monocytes are the largest leukocyte. These differentiate into macrophage in the tissues and are part of the mononuclear phagocytic system.

Question 51

What is the most abundant formed blood element?

Answer 51

Red blood cells are the most abundent, followed by platelets (100-300,000/microliter).

Question 52

What is the appearance of a platelet?

Answer 52

These are dark-staining, disk shaped cell fragments (from megakaryocytes of the bone marrow). There is no nucleus, just cytoplasm with many layers of membrane and circumferential bands of microtubules

Question 53

Lifespan of platelets?

Answer 53

10 days

Question 54

Function of platelets

Answer 54

The cytoplasm contains clot forming substances and many vasoactive substances. They play a role in adhesion and aggregation (plugging) of endothelial injuries, formation of fibrin clots, retraction of clots (actin, myosin) and lysis of clots (plasmin).