Neurocellular Anatomy

Question 1

Perikaryon cytoplasm consists of:

Answer 1

1. membranous cisternae
2. lysosomes
3. aging pigment
4. mitochondria
5. multivesicular bodies
6. neurotubules
7. neurofilaments
8. ribosomes

Question 2

Membranous cisternae of the perikaryon can be divided into which groups?

Answer 2

1. rough/granular endoplasmic reticulum
2. smooth/agranular endoplasmic reticulum
3. subsurface cisternae
4. Golgi apparatus

Question 3

Granular endoplasmic reticulum does what?

Answer 3

Forms part of the Nissl substance.

Question 4

What is another term for aging pigment?

Answer 4

lipofuscin granules

Question 5

Describe Nissl substance of the perikaryon:

Answer 5

1. It consists of the intracytoplasmic basophilic masses that ramify loosely throughout the cytoplasm and is typical of most neurons.
2. The distribution of Nissl substance in certain neurons is characteristic and can be used as a criterion for identification.
3. It is seen to comprise regular arrays or scattered portions of flattened cisternae of the rough ER surrounded by clouds of free polyribosomes.
4. Sometimes cisternal walls meet at fenestrations.
5. The rough ER of neurons produces most of its proteins for use within that neuron.
6. Nissl substance does not penetrate axons but does extend along dendrites.

Question 6

Describe smooth endoplasmic reticulum of the perikaryon:

Answer 6

1. Ribosomes are not associated with smooth ER.
2. The cisternae usually assume a branching course throughout the cytoplasm.
3. Individual cisternae of the smooth ER extend along axons and dendrites.

Question 7

Describe subsurface cisternae of the perikaryon:

Answer 7

1. They are a system of smooth, membrane-bound, flattened cisternae that can be found in many neurons.
2. They are referred to as hypolemmal cisternae.
3. They border the plasmalemma of the neuron and constitute a secondary membranous boundary within the cell.

Question 8

Describe the Golgi apparatus of the perikaryon:

Answer 8

1. It is a highly specialised form of agranular reticulum.
2. Consists of aggregates of smooth-walled cisternae and a variety of vesicles.
3. It is surrounded by a heterogeneous assemblage of organelles, including mitochondria, lysosomes, and multivesicular bodies.
4. It encompasses the nucleus and extends into dendrites but it is absent from axons.
5. The stacks of cisternae are pierced periodically by fenestrations.
6. Coated vesicles (alveolate vesicles) proliferate from the lateral margins of flattened cisternae.
7. Acid hydrolases are rich in the alveolate vesicles, and these vesicles are believed to represent primary lysosomes.
8. Acid phosphatase is also found elsewhere in the cisternae but in lesser amount than in alveolate vesicles.

Question 9

Describe the lysosomes of the perikaryon:

Answer 9

1. They are the principle organelles responsible for the degradation of cellular waste.
2. The primary lysosome is elaborated from Golgi saccules as a small, vesicular structure. Its function is to fuse with the membrane of phagosomes, into which it releases hydrolytic enzymes. Sequestered material is then degraded within the vacuole, and the organelle becomes a secondary lysosome, which is usually electron-dense and large. It contains acid phosphatase.
3. Residual bodies containing nondegradable material are considered to be tertiary lysosomes, and in the neuron some are represented by lipofuscin granules.

Question 10

waste-containing vacuoles

Answer 10

phagosomes

Question 11

What are the aspects of lipofuscin granules?

Answer 11

1. They contain brown pigment.
2. Contain lamellar stacks of membrane material.
3. Are more common in the aged brain.

Question 12

The nucleolus of the neural nucleus contains which two textures?

Answer 12

1. pars fibrosa

2. pars granulosa

Question 13

What are the pars fibrosa of the neural nucleolus?

Answer 13

fine bundles of filaments

Question 14

What are the pars granulosa of the neural nucleolus?

Answer 14

predominately dense granules

Question 15

Describe the multivesicular bodies of the perikaryon:

Answer 15

1. They are usually found in association with the Golgi apparatus and are small, single membrane-bound sacs.
2. They contain several minute, spherical profiles.
3. They are believed to belong to the lysosome series prior to secondary lysosomes because they contain acid hydrolases and apparently are derived from primary lysosomes.

Question 16

Describe the neurotubules of the perikaryon:

Answer 16

1. Also called neuronal microtubules.
2. Usually arranged haphazardly throughout the perikaryon of neurons but are aligned longitudinally in axons and dendrites.
3. Each neurotubule consists of a dense-walled structure enclosing a clear lumen, in the middle of which may be found an electron-dense dot.
4. Each microtubule wall consists of 13 filamentous subunits arranged helically around a lumen.
5. Axonal microtubules display 5 nm filamentous side-arms known to be involved in axoplasmic transport in association with the molecular motor proteins, kinesin and dynein.

Question 17

Describe the neurofilaments of the perikaryon:

Answer 17

1. Belong to the family of intermediate filaments and usually are found in association with neurotubules.
2. Constant components of axons but are rarer in dendrites.
3. In the axon, individual filaments possess a minute lumen and interconnect by proteinaceous side-arms, thereby forming a meshwork.
4. Because of these cross-bridges, they do not form tightly-packed bundles in the normal axon, in contrast to filaments with astrocytic processes, which lack cross-bridges.
5. Neurofilaments within neuronal somata usually do not display cross-bridges and can be found in tight bundles.
6. Microfilaments are composed of actin.
7. Microfilaments are involved in mechanical stress and organelle transport via nanotubular highways known as ‘tunneling nanotubes’.
8. Actin microfilaments facilitate movement and growth.

Question 18

Describe the mitochondria of the perikaryon:

Answer 18

1. They are centers for oxidative phosphorylation and are the respiratory centers of all cells.
2. Usually they are aerobic, but some are anaerobic.
3. Consist of double-membraned sacs surrounded by protuberances (cristae), extending from the inner membrane into the matrix space.