Nervous tissue Flashcards
1
Q
What are the two part of the nervous system?
A
- Central nervous system
- Peripheral nervous system
2
Q
What makes up the CNS?
A
- Brain
- Spinal cord
3
Q
What makes up the PNS?
A
- Cranial nerves
- Spinal nerves
4
Q
What is the PNS divided up into?
A
- The somatic nervous system (SNS)
- The autonomic nervous system (ANS)
5
Q
What are the two types of matter present in the brain?
A
- Gray matter
- White matter
6
Q
What is gray matter composed of?
A
- Neuron perikarya (cell bodies)
- Glial cells
- Axons
- Dendrites
- Synapses
7
Q
What is white matter composed of?
A
Axons, myelin sheath and glial cells
8
Q
What is not present in white matter that is present in gray matter?
A
No neuron, perikarya or synapses
9
Q
What are the two functional divisions of PNS?
A
- Sensory (afferent) divisions
- Motor (efferent) division
10
Q
What does the sensory (afferent) divisions do?
A
Carries signals to the CNS
11
Q
What does the motor (efferent) division do?
A
From CNS to effectors
12
Q
What is are the divisions of sensory?
A
– Somatic division, eg touch, pressure
– Visceral sensory division, eg taste, hunger
13
Q
What is are the divisions of sensory division? and give effectors for each
A
- Somatic motor division
Effectors: skeletal muscles - Visceral motor division (also called ANS)
Effectors: glands and cardiac/smooth muscles
14
Q
What is the function of the somatic nervous system?
A
Motor innervation of all skeletal muscles
15
Q
What is the function of the autonomic nervous system?
A
Motor innervation of smooth muscle, cardiac muscle, and glands.
16
Q
What are the general functions of the visceral sensory?
A
Stretch, pain, temperature, chemical changes and irritation in viscera; nausea and hunger
17
Q
What are the special functions of the visceral sensory?
A
Taste, smell
18
Q
What are the general functions of the somatic sensory?
A
Touch, pain, pressure, vibration, temperature and propriception in skin, body wall and limbs
19
Q
What are the special functions of the somatic sensory?
A
Hearing, equilibrium, vision
20
Q
What are the major brain cell types?
A
- neurons
- astrocytes
- microglia
- oligodendrocytes (CNS)
- schwann Cells (PNS)
21
Q
What is the function of oligodendrocytes?
A
Provide myelin sheaths that insulate axons
22
Q
What is the function of capillaries (in brain)?
A
Form the blood-brain-barrier
23
Q
What is the function of microglia?
A
The macrophages of the brain, provide an immune system against infections but release molecules that kill neurons
24
Q
What is the function of astrocytes?
A
To release growth factors, create scar tissue, control
brain-blood-barrier
25
What is the soma?
The cell body
26
What is the function of dendrites?
They receive information
27
What is the synapse?
Where two neurons 'meet'
28
What is the myelin sheath?
Protective neuronal 'covering'
29
What are the three structural classifications of neurons?
- unipolar (1 branch)
- biopolar (2 branches)
- multipolar (many branches)
30
H & E function
Stains nucleus, no detail on cytoplasm can be seen
31
Nissl function
stains RNA – note absence from the axon (A)
32
Heavy metal impregnation technique function
Shows detail of the cytoplasm, negative image of the nucleus. Note the terminal boutons (B) making synapses with the cell body.
33
Gold method function
Provides excellent detail of neuronal shape shows the presence of cytoskeleton in the dendrites and axons; the blue counterstain shows the nuclei of surrounding cells.
34
Describe silver impregnation method
Purkinje cell in the cerebral cortex. These cells have a single small axon A at one pole and a finely branching dendritic tree at the other pole.
35
What is the function of sensory neurons?
- Nerves that make you feel
- Deliver info from sensory
receptors in PNS to CNS
36
What is the function of motor neurons?
- Nerves that make you move
| - Deliver motor commands from CNS to PNS, muscle, glands
37
What is involved in neurotransmittion? (basic)
1. Action potentials reach presynaptic terminal
2. Stimulate Ca2+ entry
3. Neurotransmitters released from synaptic vesicles
4. Neurotransmitter crosses synaptic junction (synapse)
5. On postsynaptic terminal transmitter binds receptor
6. Receptor activated to transmit a signal in postsynaptic neuron
38
What is involved in neurotransmittion? (chemical)
1. Presynaptic membrane depolarization induces
2. Brief opening of calcium channels
3. Calcium influx promotes exocytosis of synaptic vesticles with..
4. Release of neurotransmitter
5. Neurotransmitter reacts with receptors
6. Promotes postsynaptic membrane depolarization
39
Diameter of synapytic vessels
40-60 nm
40
Where are synaptic vesicles concentrated?
In clusters at nerve terminals
41
What does neurotransmitter release involve?
1. Targeting of SVs to release sites
2. Docking of SVs to plasma
membrane
3. Priming to fuse SVs during impulse
4. Fusion/exocytosis & transmitter release
5. Retrieval of SV by endocytosis
'KISS & RUN' PROCESS
42
How do SVs recycle in presynaptic transmitter release?
Recycle without collapsing into membrane
43
What are two types of drugs?
- Agonist drugs
| - Antagonists drugs
44
What is the function of agonist drugs?
Activate receptors like neurotransmitters
45
What is the function of antagonists drugs?
Inhibit receptors and block neurotransmitters binding to receptors
46
What are the steps in postsynaptic receptor activation?
1. Neurotransmitters bind receptors
2. Receptors are then activated
3. Activation of receptors transmits signal into the cell
4. Signals cause the cell to grow, die, move, etc
47
What does myelination aid with?
Signal conduction velocity down the axon
48
What is myelin?
An electrical insulator sheath wrapped around axons
49
What do oligodendrocytes produce?
Produce myelin on CNS axons
50
What do schwann cells produce?
Produce myelin on PNS axons
51
What are the short gaps in myelin along axons called?
Nodes of Ranvier
52
How many myelin sheaths does a schwann cell form?
One
53
What do myelin sheaths prevent?
Prevents flux of ions across the membrane
54
What is the distance between nodes of ranvier?
1mm
55
Where do the AP's occur?
At ion channels
56
What do cable properties mean?
That the AP’s jump from node to node
57
What is the name for when the AP’s jump from node to node
Saltatory conduction
58
What does myelination aid with?
Proprogation down the axon
59
Name a consequence of demyelination
Multiple sclerosis
60
What is multiple sclerosis?
An auto Immune Disease which is when the body starts to destroy itself
61
What occurs in MS?
The body attacks and destroys the fatty tissue called myelin that insulates an axon/nerve, and is called demyelination.
62
What does MS affect?
The central nervous system and inflames the white matter in the brain which creates plaques.
63
What can occur if damage with MS is sever?
It can also destroy the nerve/axon itself
64
How does the PNS communicate with the CNS?
1. Sensory (afferent) neurons conduct signals from receptors to the CNS
65
How does the PNS communicate with the CNS?
1. Sensory (afferent) neurons conduct signals from receptors to the CNS
2. Interneurons (association) are confined to the CNS
3. Motor (efferent) neurons conduct signals from teh CNS to effectors such as muscles and glands
66
What is the sensory system composed of?
3 neurons
1oy Primary Neuron
2oy Secondary Neuron
3oy Tertiary Neuron
67
Where does interpretation of the three neurons occur?
In cortex
68
Afferents (direction)
Body to brain
69
Where does the 2oy secondary neuron run?
Up to thalamus
70
Where does the 3oy tertiary neuron run?
Up to cortex
71
Where is the 1oy primary neuron from?
Synapse
72
Efferents direction
Brain to body
73
General synapse basic connection
nerve-nerve
74
Neuromuscular junction basic connection
Nerve-muscle
75
Give the key features of generalised synapse
- Nerve-nerve synapse smaller than a NMJ with a narrower synaptic cleft
- Smooth postsynaptic membrane gives small surface area
- May be excitatory or inhibitory
- Numerous transmitter substances
76
What are the key features of the neuromuscular junction?
* NMJ is larger than a nerve-nerve synapse with a wider synaptic cleft
* Folds of postsynaptic membrane gives large surface area
* the NMJ is always excitatory
77
How many transmitter does the neuromuscular junction have?
One – Acetylcholine
78
How many muscle fibres in eye?
10
79
How many muscle fibres in biceps?
1000's
80
What is the effect of curare on neurotransmission?
Blocks nicotinic acetylcholine receptor
81
What is the effect of curare on neurotransmission?
Blocks nicotinic acetylcholine receptor
82
What is the effect of organophosphates on neurotransmission?
Blocks acetylcholine-esterase
83
What is the effect of atropine on neurotransmission?
Blocks muscarinic acetylcholine receptor
84
What is the effect of botulinum toxin on neurotransmission?
Blocks acetylcholine release
85
What is the effect of black widow venom on neurotransmission?
Promotes acetylcholine release
86
What effect does curare have on muscle?
Muscle weakness
87
What effect does botulinum toxin have on muscle?
Muscle weakness
88
What effect does atropine have on muscle?
Dilates pupils, increases heart rate
89
What effect does black widow venom have on muscle?
Continuous contraction
90
What effect does organophosphates have on muscle?
Continuous contraction
91
What is myasthenia gravis?
An autoimmune disorder
92
What occurs in the body during myasthenia gravis?
Body makes antibodies that attack nicotinic ACh receptors at NMJ
93
What develops in myasthenia gravis?
Muscular weakness
94
Action potentials in myasthenia gravis?
Fewer action potentials in muscle so muscle contractile force is reduced
95
End plate potential of myasthenia gravis?
Smaller end plate potential which may be sub-threshold
96
Symtoms of myasthnia gravis
- Eye muscle weakness
- Weakness of other limbs
- Respiratory muscles – may need intubation to maintain airway
97
Treatments for myasthenia gravis
- Cholinesterase inhibitors eg neostigmine
| - Immunosuppressants
98
Excitatory or inhibitory nerve-nerve synapse vs neuromuscular junction
NN - Excitatory or inhibitory
| NMJ - always excitatory
99
Surface area of NN synapse vs NMJ
NN - smooth postsynaptic membrane gives small
surface area
NMJ - folds of postsynaptic membrane gives larger surface area
100
Size of NN synapse vs NMJ
NN- smaller with a narrower synaptic cleft
| NMJ - larger with a wider synaptic cleft
101
Transmitter substances of NN vs NMJ
NN - numerous transmitter substances
| NMJ - One transmitter – Acetylcholine
102
Potential of NN vs NMJ
NN - lower - always subthreshold
| NMJ - higher - always suprathreshold
103
Summation in NN vs NMJ
NN - summation needed
| NMJ - no summation needed
104
Give the functions of neuroglia
Protect the neurons and help them function - no axons or dendrites.
105
Give an example of neuroglia
In the fetus, guide young migrating neurons to their destinations
106
Number of neuroglia vs neuons
Neurons are outnumbered by neuroglia in the nervous system
107
What are the four types of neuroglial cells in the CNS?
- Astrocytes
- Oligodendrocytes
- Ependymal cells
- Microglia
108
What are the most abundant glial cells?
Astrocytes
109
What is the function of astrocytes?
- Form framework of CNS
- Link neurons to blood vessels
- Contribute to blood-brain barrier.
110
What do oligodendrocytes form?
Myelin sheaths in CNS
111
Function of ependymal cells
Line ventricles of the brain and central canal of the spinal cord; produce cerebral spinal fluid.
112
What are microglia formed from?
Monocytes
113
What is the function of microglia?
Engulf invading microbes
114
Where are microglia present?
In areas of infection, trauma or stroke
115
What are the two types of neuroglail cells in the PNS
- Schwann cells
| - Satellite cells
116
What are schwann cells?
Myelinate fibers of PNS
117
What do schwann cells assist in?
In the regeneration of damaged fibres
118
Where are satellite cells present?
Surround cell bodies in ganglia
119
What is the function of satellite cells?
They regulate the chemical environment of the neurons
120
What do microglia act as?
Scavengers
121
Name a modified immune cell
Microglia
122
Give two functions of ependymal cells
- Create barriers between compartments
| - Source of neural stem cells
123
Give a function of astrocytes
Take up K+, water, neurotransmitters
124
Give a function of schwann cells
Secrete neurotrophic factors
125
Give a functino of satellite cells
Support cell bodies
