Nerve Tissue Flashcards Preview

Histology > Nerve Tissue > Flashcards

Flashcards in Nerve Tissue Deck (103)
Loading flashcards...
1
Q

Our body contains on average about how many neurons?

A

100,000,000

2
Q

Neurons have a large, rounded usually ___ nucleus with a prominent ____

A

euchromatic; nucleolus

3
Q

____ is the cell body which varies in size between 5-135 um

A

Perikaryon

4
Q

The RER is extremely well-developed and forms dense structures, visible in the light microscope that are called ____ bodies. These are formed by parallel arrays of RER cisternae.

A

Nissl

5
Q

Neurons have very few mitochondria. True or false?

A

false, have many

6
Q

Lysosomes are never present in the cytoplasm of neurons. True or false?

A

false, usually present

7
Q

Neurons usually lack ____. This means the cell in not capable of cell division.

A

centrioles

8
Q

The only neurons that are replaced in an adult human body on a regular basis are the ___ neurons

A

olfactory

9
Q

Cytoskeleton of neurons is very well developed and consists of _____, ____ and _____

A

nerofilaments, microfilaments, and microtubles

10
Q

Each neuron has how many axons per cell?

A

only one

11
Q

Axons begin from an elevated platform on the perikaryon called the ___ ___. Nissl bodies are absent here.

A

axon hillock

12
Q

The axon is enclosed by the continuation of the plasma membrane called ____

A

axolemma

13
Q

The cytoplasm of the axon does not contain either ___ ___ or ____ but has well-developed ER

A

Nissl bodies; ribosomes

14
Q

The transport from the perikaryon to the periphery of the axon is called the _____ flow. The opposite direction is called what?

A

anterograde; retrograde

15
Q

What is the motor used in anterograde flow?

A

kinesin

16
Q

Slow axonal transport (1-6 mm/day) is used to move substances such as?

A

tubulin molecules, actin molecules, proteins that form neurofilaments

17
Q

Fast axonal transport (100-400 mm/day) is used to move what?

A

membrane bound organelles, such as SER compartments, synaptic vesicles, and mitochondria

18
Q

The fast retrograde flow provides transport of material taken up by ____ at axon terminal back to perikaryon

A

endocytosis

19
Q

Most neurons have several dendrites per cell. Dendrites are designed to deliver the signal form the cell ____ to the ___

A

periphery; perikaryon

20
Q

There can be up to ____ synapses in one dendritic tree

A

200,000

21
Q

The surface of dendrites is covered with ___ ___, where synapses with axonal process of other neurons are formed. They have a mushroom shape and the head is where the most postsynaptic receptors are located

A

dendritic spines

22
Q

Are dendrites myelinated?

A

no

23
Q

The cytoplasmic composition of dendrites is similar to that of the perikaryon. They contain ___ and ___, but not ____

A

ribosomes; RER: golgi

24
Q

The following describes axon or dendrite:

no nissl bodies; myelin sheath; constant diameter; restricted branching; smooth surface

A

axon

25
Q

The following describes axon or dendrite:

nissl bodies; no myelin sheath; tapered; branches profusely; rough surface

A

dendrite

26
Q

_____ neurons are primarily sensory neurons that have a single large process that begins from the perikaryon.

A

pseudounipolar

27
Q

Where are pseudounipolar neurons usually found?

A

dorsal root galnglia and some cranial nerve ganglia

28
Q

____ neurons are sensory neurons that are rather limited in their distribution. They have two processes that extend from the cell body: an axon and dendrite.

A

bipolar

29
Q

where are bipolar neurons commonly found?

A

major sense organs such as: eye retina, olfactory mucosa, and cochlea and semicircular canals of the inner ear

30
Q

____ neurons represent the most common type of neurons. These neurons have one axon and many dendrites

A

Multipolar

31
Q

There are two types of multipolar neurons. Describe each one.

A

Golgi type I: long axon, large motor neurons found in motor nuclei of CNS
Golgi type II: short axon, interneurons found in the CNS

32
Q

Nerve cells are similar to muscle cells in the fact that the plasma membrane of a nerve cell is an electric _____, like the sarcolemma of a muscle cell.

A

capacitor

33
Q

The voltage on the inner side of the plasma membrane is negative (-70) relative to the outer side, so there is a ____ membrane potential in a resting cell

A

negative

34
Q

The concentration of Na+ is ___ X greater outside the cell

A

10

35
Q

Define action potential

A

brief positive going changes in the membrane potential that are propagated along the length of the membrane at a speed up to 120 m/sec

36
Q

Electrical synapses in mammals are represented by ___ ____, which allow direct passage of ions from one cell to another to transmit the wave of depolarization.

A

gap junctions

37
Q

_____ synapses are the principal type of synapses found in mammals. There is no protoplasmic continuity between the two cells and the signal is transmitted by release of NT by one cell.

A

chemical

38
Q

____ synapses increase the negative potential, which hyper polarizes the postsynaptic membrane, making it less likely to generate an action potential

A

inhibitory

39
Q

Presynaptic ____ contains synaptic vesicles that are 40-60 nm in diameter and contain the NT

A

knob

40
Q

As the action potential reaches the presynaptic terminal it opens ___ channels briefly

A

Ca2+

41
Q

The influx of Ca2+ into the cytoplasm does what?

A

causes synaptic vesicles to migrate to the presynaptic membrane and fuse with it. The NT then diffuses across the cleft

42
Q

After the vesicles with NT fuse to the postsynaptic membrane, what happens to the extra plasma membrane that was formed due to the vesicles fusing?

A

removed by endocytosis using clathrin-coated vesicles

43
Q

Up to 80% of the NTs that have been released into the cleft can be recaptured through the mechanism known as ___ ____. The NT is reincorporated by endocytosis into vesicles that are ready for repackaging

A

high-affinity reuptake

44
Q

Enzymes associated with synaptic membrane, break down the remaining NT (ex: norepinephrine) that is left in the synaptic cleft. A drug that inhibited these enzymes would be beneficial in treating what?

A

depression

45
Q

If the connection is between an axon and a dendrite, the synapse is called _____

A

axodendritic

46
Q

If the connection is between an axon and perikaryon, the synapse is called _____

A

axosomatic

47
Q

If the connection is between an axon and another axon, it is called ____

A

axoaxonic

48
Q

______ ______ represents the neuromuscular junction and is a specialized type of synapse

A

motor end-plate

49
Q

What 3 things do motor end-plates consist of?

A
  1. axon terminal contains presynaptic vesicles with the NT acetylcholine
  2. synaptic cleft is the space between the plasma membranes of the nerve cell and the muscle cell
  3. sarcolemma of a muscle cell forms multiple junctional folds where the sites for acetylcholine are located
50
Q

Several toxins disable the chemical synapses including motor end-plates and do not allow the depolarization of the sarcolemma. The two best known toxins are the curare toxin and botulinum toxin. Describe each one.

A

Curare: binds to acetylcholine receptors and acts as a muscle relaxant (fun fact: used by Indians for hunting)

botulinum: produced by clostridium botulinum; prevents release of acetylcholine form the synaptic vesicles (botox is a brand name of this toxin)

51
Q

Describe the autoimmune disease myasthenia gravis

A

affects neuromuscular junction, characterized by muscle weakness
mechanism: 1. auto-antibodies to the acetylcholine receptors are produced. 2. auto-antibodies bind to the receptor sites, which weakens the muscle response to nerve stimuli

52
Q

Describe how Rabies virus works

A
  1. virus replicates in muscle after bite (1-2 weeks)
  2. virus finds motor-end plate and gets into cleft
  3. virus enters synaptic terminal and via retrograde axonal transport, reaches CNS and spreads to other neurons
  4. Severe inflammation in CNS - any change in light intensity or sound can cause seizure (ex: running water)
  5. virus spreads into the salivary glands
  6. after symptoms have shown up, generally there is no cure
53
Q

The PNS contains two major types of support cells. What are they?

A

Schwann cells, satellite cells

54
Q

Schwann cells form a lipid layer called ___ ____ that surrounds axons in the peripheral nerves

A

myelin sheath

55
Q

True or false? myelin sheath is necessary for rapid conduction of electrical impulses

A

true

56
Q

Gaps in myelin sheath are called what?

A

nodes of ranvier

57
Q

nodes of ranvier have a high concentration of ___ channels

A

Na+

58
Q

Action potential in myelinated nerve fibers travels via saltatory conduction, which means what?

A

the membrane is only depolarized at the nodes of ranvier

59
Q

True or false?

Schwann cells only support myelinated nerve fibers.

A

false; both myelinated and unmyelinated

60
Q

Action potential travels through myelinated fibers using ___ ____ (fast)

A

saltatory conduction

61
Q

Describe action potential in unmyelinated fibers

A

wave-like

62
Q

Satellite cells provide ___ ___ for the bodies of neurons. How are they different than schwann cells?

A

electric insulation; do not have myelin

63
Q

All of the support cells in the CNS stain positive for GFAP, which forms the ___ ____ cytoskeleton of these cells

A

intermediate filament

64
Q

____ are among the largest neuroglial cells and provide support for neurons and vascular structures of the CNS. They have a granular cytoplasm and large nuclei; the mitochondria are numerous in the cytoplasm

A

astrocytes

65
Q

Astrocytes play an important role in what?

A

moving metabolic substances between blood and nerve cells and forming the blood-brain barrier

66
Q

There are two types of astrocytes, protoplasmic and firbrous. Describe them.

A

protoplasmic: found in gray matter of brain, have numerous short, branching processes that form structures called perivascular feet
fibrous: have more prominent cytoskeleton, found in white matter of the brain, have fewer processes with less expressed branching

67
Q

Tumors derived from astrocytes are called _____

A

astrocytomas

note: represent 20% of all brain tumors

68
Q

Astrocytes give rise to ___% of all tumors that originate in the brain

A

80

69
Q

____ are the most common neuroglial cells of the CNS. These are smaller cells, than astrocytes. They have small nuclei, abundant SER and prominent golgi.

A

oligodendrocytes

70
Q

There are few tongue-like cell process that extend from oligodendrocyte cell body to wrap around the axons of the neurons of the CNS forming segments of ___ ___

A

myelin sheath

71
Q

___ ___ is a disease that is caused by damage to the myelin sheath of the axons in the CNS done by cells of the immune system. It results in the partial loss of the myelin sheath

A

multiple sclerosis

72
Q

What are the symptoms of multiple sclerosis?

A

loss of sensitivity, partial paralysis, etc. depending on the area that is damaged

73
Q

Microglial cells have distinctive ___ properties.

A

phagocytic

74
Q

Microglial cells are derived form ___ ____ and are part of the mononuclear phagocytic system. They are the smallest neuroglial cells.

A

blood monocytes

75
Q

Microglial cells have dark indented nuclei and limited cytoplasm. They have few short twisted process that are covered with spikes. The cytoplasm of microglial cells may contain many lysosomes. What is the function of microglial cells?

A

remove debris from CNS

76
Q

Microglial cells are abundant in patients with ____ and ____ diseases. It is possible that they are partially responsible for plaque formation, demyelination, and destruction of nerve fibers in the CNS of patients with these diseases.

A

Alzheimer’s; Parkinsons

77
Q

The ventricles of the brain and cavities of the spinal cord are lined with ___ cells.

A

ependymal

78
Q

Ependymal cells are responsible for what?

A

production and absorption of CSF

79
Q

Ependymal cells are arranged in a form of ___ ___ epithelium

A

simple cuboidal

note: unlike true epithelium, there is no basal lamina

80
Q

The nerves of the ___ are made of many nerve fibers that carry sensory and motor information between the organs and tissues of the body. They are composed of _____ and ____ axons.

A

PNS; myelinated; unmyelinated

81
Q

____ surrounds individual nerve fibers
____ surrounds nerve fasicles
____ surrounds individual nerves

A

endonerium; perinerium; epineurium

82
Q

____ are clusters of neuron cell bodies outside the central nervous system.

A

ganglia

83
Q

The major types of ganglia are the sensory craniospinal ganglia and the motor ganglia of the ANS. Describe both

A

Sensory craniospinal ganglia: contain pseudounipolar neurons that have a single process which T-branches not peripheral and central process. The peripheral process goes to receptor organ. the central process goes to spinal cord. Satellite cells surround the neurons of these ganglia.

Motor ganglia: contain multipolar neurons and satellite cells

84
Q

Special endings can be either motor or sensory. True or false?

A

true

85
Q

Free nerve endings are branched sensory endings that do what?

A

mediate pain

86
Q

These nerve endings include messiness’ corpuscle, pacinian corpuscle and several others

A

encapsulated nerve endings

87
Q

Describe meissner’s corpuscle

A

cylindrical structure formed by the stacks of lamellae that surround one or two sensory nerve endings. These receptors provide the sense of touch and are most common in the skin of fingers and toes

88
Q

Describe Pacnian corpuscle

A

largest encapsulated nerve ending and is most complex. it is spherical in shape and consists of up to 30 concentric sheets of connective tissue with fluid between the layers

89
Q

Pacinian corpuscles respond to what? Where are they found?

A

respond to vibration and deep pressure; found in dermis, mesenteries, and inside internal organs

90
Q

____ are designed to collect information about the angulations of joints and muscle tension

A

proprioceptors

91
Q

Inside the muscle spindle are ___ fibers

A

intrafusal

92
Q

The ___ nerve fibers wrap around the intrafusal fibers and transmit information about the degree of stretching. The ___ nerve fibers regulate sensitivity of the stretch receptor

A

sensory; motor

93
Q

The CNS consists of what?

A

spinal cord and brain

94
Q

Clusters of neurons in the CNS are called what?

A

nuclei

95
Q

Nerve fibers are organized into ___

A

tracts

96
Q

____ matter consists of neuron bodies and unmyelinated fibers that form dense fibrous network

A

gray

97
Q

In the spinal cord the ___ matter is internal to the ___ matter

A

gray; white

note: this is opposite of brain

98
Q

In the brain, the gray matter is external to the white matter and is often thrown into deep folds called gyri. In the cerebellum these folds are called what?

A

folia

99
Q

The three main types of neurons found in the cerebrum are?

A

pyramidal cells, fusiform cells, and granule cells

100
Q

In the cerebellum, the gray matter is organized into three layers: The molecular layer, purkinje cell layer, and granular layer. Describe each layer.

A

molecular layer is most external, contains few cell bodies of neurons called basket cells and numerous cell process

the purkinje cell layer is a thin layer composed of very large neurons called purkinje cells

the granular layer is the most internal layer, adjacent to the white matter. It is highly composed of small neurons called granule cells

101
Q

White matter consists of what?

A

myelinated axons and glial cells.

102
Q

True or false. The white matter has a plentiful blood supply compared to gray matter.

A

false; limited blood supply compared to gray matter

103
Q

Generally, there are no synaptic contacts within white matter. True or false?

A

true