Nerve Tissue Flashcards

1
Q

What are the functions of the nerve tissue?

A

Rapid and specific communication

Keeping up with changing environment

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2
Q

What is the composition of the nerve tissue

A

Neurons which are specialized nerve cells and electrically excitable
Support cells which help neurons, they are called neuralgia. They are non conducting so not electrically excitable

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3
Q

What are the categories of neurons ?

A

Sensory-gather information from receptors
Interneurons-form a communicating network
Motor-convey impulses to effector cells

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4
Q

What is the cell structure of a neuron?

A
Perikaryon-cell body
Large rounded euchromatic nucleus
Well developed RER concentrated in granules called Nissl bodies
Golgi complex
Many mitochondria
Lysosomes
No centrioles
Cytoskeleton made with neurofilaments and microtubules
Cell processes
Synapses that transmit information
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5
Q

What are the cell processes?

A

Axon-from the perikaryon to the next neuron or effector

Dendrites-From periphery to the perikaryon

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6
Q

What is the purpose of the synapse?

A

The synapses transmit information.

They can be excitatory or inhibitory

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7
Q

What is the structure of an axon?

A

Axolemma (plasma membrane)
Axoplasm- axonal cytoplasm which does not have Nissl bodies or ribosomes but have a developed SER and mitochondria
Cytoskeleton with abundant microtubules and neurofilaments

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8
Q

What are the characteristics of axon?

A
One per cell
Received signal from perikaryon
Variable length 
Axon hillock with no Nissl bodies
Myelin sheath might be present and provide insulation for the axon
Might have collateral branches
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9
Q

What are the types of axonal transport?

A

Anterograde flow

Fast retrograde flow

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10
Q

What are the characteristics of anterograde flow?

A
From the perikaryon 
Involves organelles like mitochondria 
Neurotransmitters  vesiccles
Actin filaments, proteins
Motor is kinesin
2 types:
Slow-tubular, actin, neurofilaments
Fast-SER vesicles, NT vesicles, mitochondria
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11
Q

What are the characteristics of Fast retrograde flow?

A

To the perikaryon
Material taken by endocytosis
Transport used by viruses and toxins
Motor is dynein

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12
Q

What are the characteristics of dendrite?

A

Delivers signal to the perikaryon
Short, thick, tapered
Highly branched forming dendritic trees and synaptic contacts
Have dendritic spines which increase the areas of synapses
Non myelinated
Possess Nissl bodies and many free ribosomes
No Golgi complex

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13
Q

What are the major types of neurons?

A

Pseudounipolar
Bipolar
Multipolar

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14
Q

What are the characteristics of pseudounipolar neurons?

A

Sensory

One process with 2 branches-a peripheral process from the periphery and a central process to the CNS

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15
Q

Where do you find pseudounipolar neurons?

A

Spinal ganglia in the dorsal nerve root

Cranial nerve ganglia

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16
Q

What are the characteristics of bipolar neurons?

A

Sensory
Small with 2 short processes (dendrite and axon)
Non myelinated

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17
Q

Where do you find bipolar neurons?

A

Retina
Cochlea
Olfactory mucosa

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18
Q

What are the characteristics of multipolar neurons?

A
Motor
Interneurons
Multiple processes with single axon and many dendrites
2 types in the CNS:
Golgi type I with long axon
Golgi type II with short axon
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19
Q

What are the types of synapse?

A

Electrical-have gap junctions or ion passage

Chemical-most common

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20
Q

What are the characteristics of chemical synapse?

A
No protoplasmic continuity
Have a presynaptic cell with presynaptic terminal 
Synaptic cleft
Postsynaptic cell (receptors)
Can be inhibitory or excitatory
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21
Q

What are the sequence of events of a chemical synapse?

A

Action potential depolarized membrane
Calcium channels open
Synaptic vesicles released through exocytosis
Neurotransmitters bind to postsynaptic membrane
Action potential generated
Membrane depolarized
Extra membrane removed through endocytosis (clathrate coated vesicles)
Removal of neurotransmitters in 2 ways:
Recapture by high affinity reuptake (catecholamines)
Dégradation by hydrolysis (acetylcholine)

22
Q

What is the clinical implication with the removal of neurotransmitter?

A

Mechanism use for treatment of depression by
Inhibition of enzyme that degrades norepinephrine
Inhibition of high affinity reuptake

23
Q

What are the types of synapses?

A
Axondendritic-between axon and dendrite
Axosomatic-Axon-perikaryon
Axoaxonic-Axon to axon
2 special types:
Motor-end plate-axon to skeletal muscle
Neuroglandular junctiomn-Axon to gland
24
Q

What are the characteristics of the motor end plate?

A

Synaptic vesicles located on the axon terminal release acetylcholine in the synaptic cleft
Sarcolemma increases surface areas through to the junctional folds with contain the receptors for acetylcholine

25
Q

What are the clinical relevances of the motor end plate?

A

Disorders of neuromuscular junctions
Toxins
Pathologies
Rabies virus

26
Q

What are some toxins affecting the motor end plate

?

A

Curare-Present in skin of South American frogs. Highly toxin and bind to acetylcholine receptors preventing binding of acetylcholine. Result in muscle unable to contract leading to respiratory distress and death
Botulinum-Prevents release of acetylcholine

27
Q

What is a pathology associated to the motor end plate?

A

Myasthenia gravis-Autoimmune disease characterized by release and binding of auto antibodies to the acetylcholine receptor protein.

28
Q

What are the characteristics of the rabies virus?

A

Bite by a rabies infected animal causes muscle damage and inoculation of the virus.
The virus replicates in the muscle in 1-2 weeks which is the period when the vaccine can be helpful.
The virus finds a motor end plate
The virus is uptaken into the axon terminal by retrograde axonal transport
Once the virus reaches the perikaryon, it travels to the CNS
The affected CNS causes inflammation (encephalitis)
Encephalitis is the cause of death due to random firing of the neurons
The virus reaches the salivary glands causing foaming
Death will most likely occur in 2-10 days after symptoms have shown up

29
Q

What are the support cells of the nervous tissue/

A
In the PNS:
Schwann cells
Satellite cells
In the CNS
Astrocytes
Oligodendrocytes
Microglial cells 
Ependymal cells
30
Q

What are the characteristics of Schwann cells?

A

Peripheral nerves
Form myelin sheath which is a lipid rich layer providing electrical insulation and rapid conduction of impulses
Have gaps in myelin sheath-Nodes of Ranvier
Nodes of Ranvier are the sites of depolarization providing saltatory conduction and also sites of synaptic contacts

31
Q

What are the characteristics of myelinated axons?

A

Schwann cell on the periphery
One axon in the center
Saltatory conduction

32
Q

What are the characteristics of unmyelinated axons?

A

Schwann cell is in the center
Several axons on the periphery
Wave like potential

33
Q

What are the characteristics of satellite cells?

A

Ganglia
Ensheath neurons
Controlled microenvironment (Electrical insulation-Pathway for metabolic exchange)

34
Q

What are the characteristics of astrocytes?

A

Most common support cells in the CNS (8-10 microns)
Prominent cytoskeleton with GFAP
Cellular processes between capillaries and neurons
Have perivascular feet with the endothelium form the blood brain barrier
2 types:
Protoplasmic in the gray matter
Fibrous in the white matter

35
Q

What is the clinical relevance of astrocytes?

A

Prolifération of astrocytes causes astrocytoma
Astrocytoma is a common tumor about 20% of all types
Scar formation after damage, gliosis, Glial scar

36
Q

What are the characteristics of oligodendrocytes?

A

Small cell 6-8 microns
Small heterochromatic round nucleus
Have abundant SER
Well developed Golgi
Few tongue like processes which wrap around axons of CNS neurons
Processes go to different axons and form part of the myelin sheath
Analogous to Schwann cells

37
Q

What is the clinical relevance of the oligodendrocytes?

A

Demyelination get diseases like multiple sclerosis
MS is due to damage to the myelin sheath (CNS) by cells of the immune system
Results in loss of sensitivity, and partial paralysis

38
Q

What are the characteristics of microglial cells?

A
Phagocytic cell
Monocyte derived
Smallest neuroglia
Indented heterochromatic nuclei
Limited cytoplasm
Many lysosomes
Few processes with spikes
Increase with injury
39
Q

What are the characteristics of ependymal cells?

A

Simple cuboidal lining in the fluid filled CNS cavities (ventricle)
Does not have basal lamina
Produce and absorb CSF
Possess microvilli and few cilia
basal processes interdigitale with astrocytes

40
Q

What are the components of the nervous system?

A

PNS with nerves, ganglia and special endings like motor end plate and sensory endings
CNS made of the spinal cord and brain

41
Q

What are the characteristics of the peripheral nerves?

A

Carry impulses
Can be myelinated or unmyelinated
Have CT sheaths (epineurium, perineurium and endoneurium)

42
Q

What are the characteristics of ganglia?

A

Cluster of neurons outside CNS
Capsule (CT)
Satellite cells

43
Q

What are the types of ganglia?

A

Craniospinal

Autonomic

44
Q

What are the characteristics of craniospinal ganglia ?

A

Sensory
Pseudounipolar neurons
Satellite cells

45
Q

What are the characteristics of autonomic ganglia?

A

Motor
Multipolar
Satellite cells

46
Q

What are the characteristics of sensory nerve endings?

A
Special senses (hearing, sight, equilibrium)
Somesthetic receptors can have  free nerve endings which mediate pain or encapsulated nerve endings like Meissner's Corpuscle, pacifiant corpuscle.they can also be proprioreceptors (muscle spindle)
47
Q

What are the characteristics of Meissner’s corpuscle?

A

Cylindrical shape with stacks of lamellae, and sensory nerve ending
Tactile receptors (touch organ )- can detect pressure
Found on skin

48
Q

What are the characteristics of Pacinian Corpuscle?

A

Large up to 2mm
Concentric sheets of CT with 30 0r more and have fluid between layers
Single nerve fiber
Responds to vibrations and deep pressure
Found in pancreas, dermis and mesenteries

49
Q

What are the characteristics of muscle spindle?

A

Stretch receptor
Structure made of external capsule, fluid filled space, internal capsule, intrafusal fibers (thin skeletal muscle fibers), sensory nerve fibers (spiral around) and motor nerve fibers

50
Q

What are the characteristics of the spinal cord?

A

Gray matter on the inside looks like a butterfly with anterior horns (motor) and dorsal horns (sensory)
White matter on the periphery

51
Q

what are the characteristics of the cerebellum?

A

Gray matter made of cortex and folia

White matter made of medulla

52
Q

What are the layers of cerebellum?

A

Molecular layer contains basket cells, dendrites and axons
Purkinje cell layer contains Purkinje cells and dendrites
Granular layer contains small granular cells