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Histology > Mammalian Nervous Tissue > Flashcards

Mammalian Nervous Tissue Flashcards

1
Q

What is the nervous system? What are its two principal purposes?

A

The nervous system:
- enables the body to respond to changes in its external environment,
- controls the functions of the internal organs and systems

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2
Q

What two principal types of cells does the nervous system consist of?

A

1) neurons
2) supporting cells

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3
Q

What are neurons?

A

Specialized cells that generate and conduct electrical impulses.

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4
Q

What are supporting cells?

A

Nonconducting cells in close proximity to nerve cells and their processes.

Supporting cells support neurons in multiple ways such as:
- nutrition
- myelin sheath production

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5
Q

What is a neuron?

A

The structural and functional unit of the nervous system.

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6
Q

What is the brain composed of?

A

Nervous tissue

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7
Q

What does the nervous system control?

A

internal organs and systems

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8
Q

What does the nervous system not control?

A

The heart.
The heart is myogenic, and controls itself.

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9
Q

What is a different name for neurons?

A

nerve cells

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10
Q

How is the nervous system divided?

A

1) Central Nervous System (CNS)
2) Peripheral Nervous System (PNS)

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11
Q

What does the CNS consist of?

A

the brain and the spinal chord

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12
Q

What does the CNS contain? (which principal type of the nervous system?)

A

gray and white matter made up of neurons and supporting cells

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13
Q

What does the PNS consist of?

A

All tissues outside the CNS such as:
- cranial nerves
- spinal nerves
- ganglia

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14
Q

What is the structure of a neuron? What is it composed of? What is its shape?

A

A neuron has a very irregular shape.

Each neuron consists of:
- a cell body
- an axon
- several dendrites

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15
Q

What is an axon? What is its function?

A

The longest process of the neuron’s cell body. It transmits electrical impulses away from the cell body.

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16
Q

What is a dendrite? What is its function?

A

The shorter process of the neuron’s cell body. It transmits impulses towards the cell body.

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17
Q

Which direction are neural signals transported through neurons?

A

From the dendrites to the axons (through the cell body).

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18
Q

How do neurons communicate with each other and effector cells?

A

Through specialised junctions called “synapses”.

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19
Q

How can one count the number of dendrites?

A

look at the cell body and how many dendrites originate from it. One dendrite can have many branches.

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20
Q

How can neurons be grouped?

A

1) Motor Neurons
2) Sensory Neurons
3) Interneurons

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21
Q

What are motor neurons? What are their functions?

A

Neurons which carry impulses from the CNS or ganglia to the effector cells.

CNS –> EFFECTORS

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22
Q

What are sensory neurons? What are their functions? What is another name for sensory neurons?

A

Neurons which carry impulses from receptors to the CNS.

RECEPTOR –> CNS

also known as “effector neurons”

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23
Q

What are interneurons? What are their functions?

A

Neurons which communicate between sensory and motor neurons.

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24
Q

Which organ are there no nerve endings?

A

the liver

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25
Q

What do all three types of neurons complete?

A

the reflex arc

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26
Q

What is neuron classification based on?

A

the structure of the neuron

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27
Q

What three classifications are neurons classified into?

A

1) multipolar neurons
2) bipolar neurons
3) unipolar neurons

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28
Q

What are multipolar neurons (main characteristics)? State examples.

A
  • numerous dendrites
  • one single axon

eg.
- motor neurons
- interneurons

(looks like the usual neuron i drew in IB)

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29
Q

What are bipolar neurons? State examples.

A
  • one single axon
  • one single dendrite (extending from the cell body)

eg.
- retina
- other special sense organs

(looks like a neuron which swallowed a balloon)

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30
Q

What are unipolar neurons? What is a different name for them? State examples.

A

different name: ‘pseudounipolar neurons’

  • one short process that arises from the cell body and bifurcates.

eg.
- sensory neurons

(looks like a neuron with a pimple that needs popping)

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31
Q

Where are the dendrites of multipolar neurons located? Why?

A

Mainly in the brain, because the body is the most most important part of the neuron (has a nucleus).

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32
Q

What is the difference between a pseudounipolar neuron and a unipolar neuron.

A

A unipolar neuron looks like a ball with a line and an axon. While the pseudo-unipolar neuron looks like a nerve with a pimple.

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33
Q

Where are the cell bodies of neurons typically found?

A

In the Central Nervous System.

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34
Q

If the cell bodies of neurons are not found in the CNS, then, where can they be found?

A

In the ganglia (which are a part of the peripheral nervous system).

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35
Q

What is RER in neurons known as?

A

Nissl bodies

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36
Q

What of the neuron can one see in the microscope? What cannot be seen?

A

The axon and the dendrite. The whole axon cannot be seen.

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37
Q

What are the different types of supporting cells (Neuroglia)? Where are they found?

A

Central neuroglia (PNS)
Peripheral neuroglia (PSN)

38
Q

How many different types are there of central neuroglia? name them

A

four types:
1) Astrocytes
2) Ogliodendrocytes
3) Microglia (Microphages)
4) Ependymal cells

39
Q

What is the name of the most common supporting cell?

A

Astrocyte

40
Q

What are astrocytes? How do they look? What shape do they have?

A
  • the most common type of SUPPORTING CELLS
  • make connections called “end-feet” with capillaries, and they facilitate metabolic exchange between blood and neurons.
  • they are STAR-SHAPED in appearance.
41
Q

What is the function of astrocytes? What connections do they make?

A
  • they facilitate metabolic exchange between blood and neurons
  • it is a bridge between a neuron and blood vessel
  • make connections called “end-feet” with capillaries
42
Q

What are ogliodendrocytes? How do they look? What shape do they have?

A
  • generate the myelin sheath (for up to 50 axons)
  • look like a spikey ball
43
Q

What is the name of the cell which generates the myelin sheath?

A

Ogliodendrocytes

44
Q

What is the function of the myelin sheath?

A
  • insulates the nerve
  • increases the rate at which the axon conducts the action potential
  • saltatory conduction
45
Q

What is the name of the disease in which the myelin sheath is damaged?

A

multiple sclerosis

46
Q

What happens in multiple sclerosis?

A

The myelin sheath is damaged and axons become demyelinated.

47
Q

What type of compound is myelin?

A

fat

48
Q

What are microglia? How do they look? What shape do they have?

A
  • play a role in immune defence
  • act as antigen-presenting cells
  • can become phagocytic
49
Q

What can microglia become?

A

phagocytic

50
Q

What type of Neuroglia cell plays a role in the immune defence system?

A

microglia cells

51
Q

How is the CNS separated from the remaining organism? What does this lead to?

A

By blood barriers. This causes a low rate of infection of the CNS.

52
Q

What are ependymal cells? How do they look? What shape do they have?

A
  • make up the ependyma (lining of the ventricles of the brain and the central canal of the spinal cord)
  • contain microvilli
  • contain one or more cilia on their apical (lumenal) surface
53
Q

What do ependymal cells do?

A

Create and move liquid which fills the ependyma, allowing for brain nutrition.

54
Q

What are the two different matters of the brain?

A

1) Gray matter
2) White matter

55
Q

What colour of mater is displayed in the CNS?

A

Gray and white

56
Q

What does gray matter contain?

A
  • cell bodies of neurons (beginnings and endings of neurons)
  • unmyelinated dendrites
  • supporting cells (neuroglia)
57
Q

What does white matter contain?

A
  • myelinated processes of neurons
  • small number of cell bodies (from supporting cells only (neuroglia only))
58
Q

What shape does the gray matter make in the spinal chord?

A

A butterfly shape. It is located on the inside.

59
Q

What shape does the gray matter make in the brain?

A

Cortex. It is located on the outside.

60
Q

What takes place in the brain cortex?

A

Processes such as learning, memorising etc.

61
Q

What are the two types of peripheral neuroglia?

A

1) Schwann cells
2) Satelite cells

62
Q

What does one Schwann cell generate?

A

the myelin sheath around the axon between each node of Ranvier.

63
Q

What are Schwann cells? What do they do to the neuron?

A
  • main type of supporting cell in the PNS
  • wrap their plasma membrane concentrically around the axon, forming a segment of myelin sheath
64
Q

Around how long is one segment of myelin sheath?

A

1mm

65
Q

What do the small gaps between each segment of sheath (nodes of Ranvier) allow for?

A

Saltatory conduction

66
Q

What is saltatory conduction?

A

The propagation of nerve impulses from one node to the next.

67
Q

What is the main type of supporting cell in the PNS?

A

Schwann cells

68
Q

The deeper the gap is between the myelin sheath the?

A

the faster the conduction.

69
Q

What are satellite cells? What is their function?

A
  • Maintain a controlled microenvironment around the nerve cell bodies in the ganglia of the PNS.
  • provide nutrition to the ganglions
70
Q

What is the ganglion?

A

Neurons which are not in the CNS.

71
Q

What are unmyelinated axons?

A

Axons with Schwann cells which do not form tightly wrapped layers around the axons, instead the Schwann cell envelops several axons.

72
Q

Is myelin present in unmyelinated cells?

A

yes!
but one Schwann cell integrates multiple axons.

73
Q

How is nervous connective tissue classified?

A

Into 3 groups:
1) Endoneurium
2) Perineurium
3) Epineurium

74
Q

What does connective tissue do to nerves?

A
  • supports their function
  • makes nerves into the nervous system organ
75
Q

What does the ENDOneurium do?

A

It surrounds each individual nerve fibre and associated Schwann cell.

76
Q

What does the PERIneurium do?

A

It surrounds each nerve fascicle.

77
Q

What does the EPIneurium do?

A

It surrounds a peripheral nerve and fills the spaces between nerve fascicles.

78
Q

What does “peri” mean?

A

near

79
Q

What is the order of nerve coverings from smallest to largest?

A

Endoneurium,
Perineurium,
Epineurium.

80
Q

What are mechanoreceptors?

A

Nerve endings responsible for sensitivity to vibration and pressure.

81
Q

Describe the structure of lamellar corpuscles.

A
  • they are connective tissue capsules
  • oval-cylindrical shaped
  • 1mm length
  • wrapped by a layer of connective tissue
  • capsule: 20-60 concentric lamellae
82
Q

What is a different name for mechanoreceptors?

A

Lamellar corpuscles.

83
Q

Why does pain appear?

A

Due to the overreaction of nerves. (more activation + impact = more pain)

84
Q

Explain neural regeneration.

A

Neurons do not divide.
Regeneration begins 20 days after injury.

1) after injury macrophages phagocytite debris and stimulate schwann cells to secrete substances that promote axon growth
2) Schwann cells form myelin sheath around axon sprouts. it takes a year to complete.

85
Q

Can neurons divide? Can they regenerate?

A

Neurons cannot divide as they cannot regenerate. They can only partially regenerate.

86
Q

What happens right after injury (neuroregeneration)?

A

Macrophages phagocytize debris and stimulate Schwann cells to secrete substances that promote axon growth.

87
Q

How long does it take for shwann cells to form myelin sheath around the axonal sprout?

A

A year

88
Q

What are the axon growth rates?

A

small nerves: 2mm/day
large nerves: 5mm/day

89
Q

What happens if the body of the neuron is damaged?

A

The nerve will not recover. All remaining parts (dendrites and axons) will die.

90
Q

What happens if the axon of the neuron is damaged?

A

The neuron can be repaired.

91
Q

Which part of the neuron can be damaged for the neuron to be later repaired? Which part of the neuron cannot be damaged for the neuron to be later repaired?

A

The axon can be damaged, the cell body cannot be damaged.

92
Q

How can transplants be done for the muscles to continue moving.

A

The nerves must be damaged at the axon so that they can later be regenerated.

Histology (11 decks)

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