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Body Logistics > Nervous Tissue - Structure and Function > Flashcards

Nervous Tissue - Structure and Function Flashcards

1
Q

What can the nervous system be divided into?

A

The central nervous system and the peripheral nervous system.

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2
Q

What does the CNS consist of?

A

The brain and the spinal cord

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3
Q

What does the PNS consist of?

A

Cranial and spinal nerves

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4
Q

What kind of neurons can be found in the CNS?

A

Relay neurons also called interneurons.

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5
Q

What kind of neurons can be found in the PNS?

A

Sensory neurons and motor neurons.

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6
Q

Where can grey matter be found in the brain and spinal cord?

A

In the brain it can be found on the periphery.

In the spinal cord it can be found centrally.

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7
Q

Where can white matter be found in the brain and spinal cord?

A

In the brain it can be found centrally.

In the spinal cord it can be found on the periphery.

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8
Q

What does grey matter consist of?

A 
Nerve cell bodies
Dendrites
Axon terminal
Non-myelinated axons
Neuroglia
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9
Q

What does white matter consist of?

A

Myelinated material

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10
Q

Describe the macro structure of grey matter.

A

Roughly in the form of a butterfly in the spinal cord.
It has anterior and posterior horns called ventral horns (anterior) and dorsal horns (posterior) They are connected by the dorsal commissure.

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11
Q

Describe the macro structure of white matter.

A

White matter contains myelinated nerve fibres that form ascending and descending tracts from the brain to the periphery. Blood vessels of the Pia mater (outer connective tissue layer), the ventral fissure, and dorsal roots is white matter.

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12
Q

What is the basic structure of the neutron?

A

It has many dendrites (branches) but on single axon.
It has a main cell body called the soma.
Usually the proximal part of an axon is in the CNS and the distal axon is within the PNS.
The axon is often coated in myelin but not always.

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13
Q

By what structure is the myelin for the axon produced in the CNS?

A

Oligodendrocytes

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14
Q

By what structure is the myelin for the axon produced in the PNS?

A

Schwann cells

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15
Q

What is the major difference between Schwann cells and oligodendrocytes?

A

Oligodendrocytes can coat several neurons

Schwann cells can only coat one each.

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16
Q

What are the four major neuron types? Where can they be found?

A

Motor (CNS to PNS)
Sensory (PNS to CNS)
Integrative (CNS)
Anaxonic (found in retina and some parts of CNS)

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17
Q

Where can you find most of the pseudounipolar, bipolar and postsynaptic autonomic neutron cell bodies?

A

Outside the CNS in the PNS.

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18
Q

What kinds of macro structures of neurons are there?

A

Pseudounipolar/unipolar
Bipolar
Multipolar
Anaxonic

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19
Q

Describe multipolar neuron.

A

One axon and multiple dendrites
Most common
Most neurons in the brain and spinal cord (CNS)

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20
Q

Describe bipolar neuron.

A

One axon and one dendrite.

Olfactory cells, retina and inner ear.

21
Q

Describe unipolar neuron.

A

Singe process leading away from soma.
One dendrite one axon.
Sensory from skin an organs to spinal cord.

22
Q

Describe anaxonic neuron.

A

Many dendrites but no axon at all.

Helps mostly in visual process as a relay in the retina.

23
Q

What is histologically special about the neuron structure in the CNS?

A

It has lots of rER
Lots of Golgi
Many free ribosomes

24
Q

How are vesicles carried from and to the soma in the neuron?

A

By microtubules and intermediate filaments. It works like a railway where the microtubule is the train carrying the vesicle and the intermediate filaments (neurofilaments and microfilaments) are the railway.

25
Q

Briefly explain neurotransmitter synthesis and its release in the synaptic cleft.

A

Neurotransmitter is formed and put in a vesicle in the soma. It is then transported to the presynaptic terminal.
An action potential travels across the axon of the neuron and reaches the presynaptic cleft.
This causes an influx of calcium to enter and this causes a release of the neurotransmitter from the presynaptic terminal to the synaptic cleft.
The neurotransmitter binds to a receptor and either activates or inhibits it.
The neurotransmitter then dissociates from the receptor and is the taken up by the presynaptic terminal to be transported back to the soma and recycled.

26
Q

What are the two fates of vesicles?

A

Lost to neurolemma

Recycled through clathrin-coated endcytosis

27
Q

What types of nerves can be found in the PNS?

A

All 3 types can be found:
Sensory
Motor
Interneuron (this is however not as common)

28
Q

What 4 layers are neuron and nerve fibres bundle into?

A

Endoneurium
Perineurium
Epineurium
Paraneurium

29
Q

What is the endoneurium?

A

A loose connective tissue surrounding single nerve cells

30
Q

What is the perineurium?

A

A specialised connective tissue which transports proteins.

Surrounds a bundle of nerve cells called fascicles.

31
Q

What is the epineurium?

A

A dense irregular connective tissue

It separates different types of nerves and fills the spaces between fascicles.

32
Q

Wat is the paraneurium?

A

Fascia that separates nerves from surrounding structures.

33
Q

Look at the histology of nerves on page 17,18 and 19.

A

Yup.

34
Q

What is the difference in electrical conduction between myelinated and unmyelinated axons?

A

Myelinated is much faster. The AP ‘jumps’ instead between the nodes of ranvier.

35
Q

Regarding to electrical conduction, why is the internodal distance important, and what is it?

A

Internodal distance is the distance between nodes of ranviers.
The larger distance the faster conduction.

36
Q

What else does electrical conduction depend on in axons?

A

The diameter of the axon. A larger diameter means faster conduction.

37
Q

Look at page 20 for more information on conductance.

A

Yup.

38
Q

Explain myelination by Schwann cells.

A

The axon sits in a groove surrounded by the Schwann cell.
The mesaxon membrane initiates myelination by surrounding the embedded axon.
A sheet-like extension of the mesaxon membrane starts wrapping around the axon forming multiple layers of membrane, it wraps around about 19-20 times.
The cytoplasm in between the layers is then squeezed out into the schwannn cell again.
The layers of membrane surrounding the axon now is the myelin.

39
Q

How is myelination by oligodendrocytes different from Schwann cells?

A

It happens in the CNS instead of the PNS

Oligodendrocytes wrap around multiple axons simultaneously.

40
Q

To find information about unmyelinated nerve cells look at page 23.

A

Yup.

41
Q

What other cells can be found in the CNS?

A

Supporting cells such as astrocytes.

Microglial cells and ependymal cells.

42
Q

Explain the structure of an astrocyte.

A

A cell with a star like structure.
They have perineurial feet that contain gap junctions.
These perineurial feet contribute to the blood-brain barrier.
One foot is connected to a blood vessel and another foot is connected to the myelin sheath on the neuron.

43
Q

What is the purpose of the astrocyte?

A

They control flow of nutrients in the CNS.
They transport nutrients like lactate from blood to nerve cells through their perineurial feet.
They also regulate nerve impulses by releasing glutamate near the node of ranvier. This means that they can slow down nerves.

44
Q

Explain the structure of microglial cells.

A

Large cells that are also somewhat star like, not as prominent though. They have an elongated nucleus and found throughout the CNS.

45
Q

What is the purpose of the microglial cell?

A

It works as a resident macrophage in the CNS.
Immune function and remove damaged nerve cells by sensing abnormal concentration of K+.
Also thought to digest protein tangles that are associated with dementia and Alzheimer’s.

46
Q

Explain the ependymal cell and its origin.

A

Derived from the neural crest and is neural tissue.
They look like columnar epithelial cells lining the spinal canal.
The apical surface has both cilia and microvilli.

47
Q

What is the purpose of the ependymal cell?

A

Synthesis and secretion of cerebrospinal fluid in the ventricles.
The cilia mover the CSF though the ventricles of the spinal cord.
Microvilli absorb CSF in order to remove pathogens by presenting them to microglial cells and astrocytes.
There are also modified tight junctions here to control fluid release into brain.

48
Q

Briefly explain Multiple Sclerosis.

A

It is a remitting and relapsing disease caused by autoimmune degradation of myelin.
This is thought to might have to do with the Epstein-Barr Virus. Scar tissue is formed where the myelin used to be. This causes a loss of conduction velocity.

49
Q

What are symptoms of MS?

A 
Fatigue
Vision problems (diplopia)
Slurred speech (dysarthria)
Numbness and tingling sensation (paraesthesia)
Mobility issues (muscle spasms)

Body Logistics (21 decks)

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