Exam 1 Flashcards
(103 cards)
1
Q
What percentage of the CNS is made of neurons?
A
50-60%
2
Q
T/F Neurons contain most of the same organelles as any other cell of the body
A
True
3
Q
What is the process by which materials move from the cell body along microtubules and neurofilaments?
A
Axoplasmic transport
4
Q
What percentage of the total neuronal surface area available for synaptic contact is made up of dendrites?
A
Over 90%
5
Q
What cells in the cerebellum have over 1000 dendrites?
A
Purkinje cells
6
Q
What is the average number of synaptic contacts/inputs made by an average neuron?
A
7000
7
Q
Myelin is formed by what type of cells?
A
Glial cells
8
Q
What is at the nodes of Ranvier?
A
Voltage-gated sodium and potassium channels for propagation of the action potential.
9
Q
What are axon collaterals?
A
branches of axons which enable the neuron to activate more than one effector cell at a time
10
Q
What is an effector cell?
A
another neuron, muscle, or a gland
11
Q
What do axon terminals contain?
A
synaptic vesicles of chemical substances (NT)
12
Q
What is the name of a neuron that is acted upon? What is the name of a neuron that causes and action?
A
Post-synaptic neuron.
Pre-synaptic
13
Q
What determines the nature of the action of a neuron on another cell type?
A
The post-synaptic receptor
14
Q
T/F Since the post-synaptic receptor determines the effect on a cell, an NT may be excitatory for some cells and inhibitory for other cell types.
A
True
15
Q
Where are bipolar neurons found?
A
in special sensory systems (eye, auditory and vestibular systems)
16
Q
Which neuron types make up the peripheral sensory afferents?
A
Pseudounipolar neurons
17
Q
Where are iterneurons found exclusively?
A
within the CNS.
18
Q
T/F Interneurons account for about 99% of neurons
A
True
19
Q
What do nuclei form in the CNS?
A
Large clusters of gray matter (cell bodies)
20
Q
What are some terms that describe bundles of axons?
A
Tract, fasciculus, and lemniscus
21
Q
What is formed by several tracts running together?
A
Funiculus
22
Q
T/F Neuron may be described by the action of their NT
A
True
23
Q
What are the four types of CNS glial cells?
A
Oligodendrocytes, Astrocytes, ependymal ells, and microglia
24
Q
Which type of Schwann cells are crucial for inducing nerve sprouting?
A
non-myelinating type of schwann cells
25
What is a glioblastoma multiforme?
an astrocytoma that often spreads extensively from one side of the brain to the other via the corpus callosum with lethal consequences
26
Schwannomas and neurofibromas are tumors of the PNS. Which type is easily removed?
Schwannomas
27
Why are neurofibromas more difficult to remove?
They infiltrate nerve fibers
28
The outside of cells has a predomination of what charged ion? Inside of cell?
Na+. K+
29
Which ion has the ability to move INTO the cell passively?
Na+
30
How do ion pumps help restore the concentration gradients of ions?
By pumping Na+ OUT and K+ into the cell
31
What are graded potentials also known as?
Local potentials
32
What is the process called when a cell membrane depolarizes a small amount?
EPSP
33
What is the process called when a cell membrane hyperpolarizes a small amount?
IPSP
34
What are the two types of summation in graded potentials?
Temporal and spatial
35
Where do graded potentials usually occur?
In unmyelinated synapse regions
36
What do astrocytes do in the CNS?
Help to remove some excess K+ ions
37
What are plateau potentials?
Relatively prolonged (but not slow) depolarizations mediated by calcium entry into the neuron. Contribute to myotonia, gongenita, spasticity
38
What region of the neuron has the lowest threshold for excitation and highest density of voltage-sensitive Na+ channels?
Axon hillock
39
Where is the initiation of action potentials in sensory neurons? In motor neurons?
In the periphery.
| In the CNS
40
Unmyelinated axons have Na+ and K+ channels all along the length of the axon, where as myelinated axon has voltage gate Na+ channels concentrated at the _________
Nodes of Ranvier
41
What is the conduction velocity along myelinated axons? How many times faster is it than on unmyelinated axons?
120 meters/sec. As much as 50 times faster
42
What is the conduction in the opposite direction of action potentials?
Antidromic conduction (elicited by machanical or electrical stimulation of the neuron)
43
What is synaptic transmission?
Electrical signal in the presynaptic neuron is converted into a chemical signal at the synapse, and then into an electrical signal again in the post-synaptic neuron
44
Synapses in the soma tend to be ______ where as those on dendrites tend to be excitatory
inhibitory
45
What are some amino acids that can act as NTs?
glycine, glutamate, aspartate.
46
What does an action potential do to the membrane of the axon terminal as it propagated down the axon?
It depolarizes the membrane
47
Where do voltage-gated calcium channels open?
in the axon terminal
48
What does entry of calcium into the axon cause the synaptic vesicles to do?
move to the synaptic terminal.
fuse their membranes with that of the presynaptic terminal.
release their contents into the synaptic cleft
49
IPSP make the membrane more _______ where as EPSPs make it less _______
polarized/negative
50
What are three ways that synaptic transmission can be terminated?
NTs diffuse away.
NTs are inactivated by specific enzymes
Nts may be taken back into the presynaptic axon terminal
51
Where does an IPSP never occur?
A synapse between an alpha motor neuron and its post-synaptic cells, the skeletal muscle cell. It all happens in the CNS before it ever gets out to the muscle
52
What is the EPSP at the NMJ called?
endplate potential
53
What is excitation-contraction coupling?
For every action potential in an alpha motor neuron, there will be an action potential in the muscle cell innervated by that motor neuron
54
What are the five broad classes of NTs?
Monoamines, cholinergic, amino acids, neuropeptides, non-traditional NTs
55
What are some monoamines?
1. Catecholmines such as norepinephrine, epinephrine, and dopamine.
2. Serotonin.
56
Acetylcholine is a _______ NT
cholinergic
57
What are three common amino acid NTs?
GABA, glycine, and glutamate
58
What are some neuropeptide NTs?
endorphins, calcitonin gene-related peptide, and substance P
59
Whare some non-traditional NTs?
NO and CO2
60
Generally NTs that open Na+ channels are ________ and those that open chloride channels are inhibitory
excitatory
61
What are the targets for most pharmocological interventions?
NTs and their receptors
62
What are the two broad classes of receptors?
Ionotropic and Metabotropic
63
What are ionotropic receptors?
form channel in membrane thru which ions can pass, NTs bind and cause a conformation change in the transmembrane proteins to open ion channels
64
What are metabotropic receptors?
G-protein coupled receptors.
Initiate range in chemical changes.
NT binds to receptor and change its shape and this activates the G-protein
65
What can activated G-proteins do?
open ion channels.
activate genes
modulate intracellular calcium concentrations
66
What NTs are of interest?
ACh, norepinephrine, dopamine, serotonin, glutamate, GABA
67
When does fertilization occur?
12-24 hours after ovulation
68
When does 2-cell stage occur? 4-cell stage (second cleavage)?
30 hours
| 40 hours
69
When is the 16-cell stage reached?
3 days
70
What does the inner cells mass, the embryoblast give rise to? What is the outer cell mass called and when does it form?
the embryo proper.
| blastocyst at five days
71
When does implantation occur?
day 6
72
When are the endoderm and ectoderm formed?
at the end of the second week
73
When does a layer of mesoderm become visible?
3rd week
74
What are the five stages of Nervous System Development?
Neurulation, Cellular proliferation, neuronal migration, cytodifferentation and axonal elongation, maturation of synaptic contacts and refinement
75
When does neurulation occur? From what layer does the nervous system begin to form?
At about 16 days of gestation.
| Ectoderm
76
What are the layer of a trilaminalr embryo?
Endoderm, mesoderm, ectoderm
77
What does the endoderm become?
viscera
78
What does the mesododerm become?
heart and circulatory system, muscle, bone, and meninges and the notochord
79
What does the notochord develop into?
nucleus pulposis of the intervertebral disks
80
What does the ectoderm become?
CNS structures, adrenal medulla, and skin
81
What is the progressive formation of CNS structures?
Neural plate, neural groove, neural folds, neural tube, neural crest
82
When should the rostral portion of the neural tube close? Caudal portion?
by day 27. by day 30
83
What does the neural crest form?
sensory ganglia of spinal and cranial nerves
84
What is the name of the congenital malformation where the rostral neuropore fails to close?
Anencephaly
85
What is the name of the congenital malformation where the caudal neuropore fails to close?
Spina bifida - oculta, meningocele, myelomeningocelef
86
What is the Arnold-Chiari malformation?
part of the cerebellum and caudal brainstem herniate through the foramen magnum
87
What are the three functional layers neural plate and neural tube formation?
Germinal zone, intermediate zone, marginal zone (aka cortical plate)
88
The germinal zone is the ______ most layer consisting of pluripotent neuroepithelial cells
inner
89
Newly divided cells in the germinal layer can be referred to as what?
Neuroblasts, glioblasts. Neuroblasts use the glioblasts to help them migrate out of the germinal zone
90
What do neuroblasts use to migrate from the germinal zone to the brains outer layers?
use fibers from radial glial cells and their own axons
91
What do glial cells secrete to help neurons find the correct pathway?
Chemical attractants
92
What do neuron cells have that helps them bind to glial cells?
adhesion molecules
93
What is tangetial migration?
Moving from one radial glia to another of following axons
94
Incomplete neuron migration can be caused by what factors?
radiation, genetic mutations, drugs such as alcohol and cocaine. Or childhood epilepsy
95
What are the regions of the spinal cord during formation?
sulcus limitans, alar plate, basal plate
96
What forms can plasticity take at the synapse?
Increased/decreased number of synaptic vesicles.
Increased/decreased number/density of postsynaptic membrane receptors.
Change in the type of postsynaptic membrane receptor
Formation of novel synapses on the same cell
Pruning of established synapses
97
In the axon, what forms can neuroplasticity take on?
Regenerative sprouting or collateral sprouting
98
In the soma, what forms can neuroplasticity take on?
Altered gene expression
99
Functionally, what does nueroplaticity result in?
Strengthening of connections between neurons.
Weakening or loss of connections between neurons.
Novel connections between neurons that previously were not connected by a synapse.
Cells becoming healthier or taking on new functions
100
What is Hebb's Law?
Cells that fire together, wire together - the synapse of two neurons is strengthened when their temporal activation is concurrent
101
Which two NTs are only metabotropic?
Norepinephrine and dopamine
102
The ionotropic receptor for ACh is ______. For meabotropic it is both _______ and ______
excitatory.
| Excitatory and inhibitory
103
T/F the actions of GABA are inhibitory for both ionotropic and metabotropic receptors
True
