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Cell Bio & Developmental Genetics > Lecture 9 (4b) - Neurons, Glia, and Nervous Systems > Flashcards

Lecture 9 (4b) - Neurons, Glia, and Nervous Systems Flashcards

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1
Q

Nervous systems can vary in

A

size and complexity
• ganglia larger and fuse in more complex organisms
• ganglia - cluster of neurons

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2
Q

Cnidarians have simple networks of neurons called

A

nerve nets

• there is little or no processing of signals

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3
Q

In more complex animals, neurons are organized into clusters called

A

ganglia

• complex animals must process and integrate larger amounts of information

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4
Q

In bilaterally symmetrical animals

A

the ganglia are often paired

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5
Q

Ganglia may be enlarged and fused at the anterior end to form

A

a brain

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6
Q

Squid

A 
signal eye (sensory)   -->
brain (integration )      -->
mantle (motor output to propel)
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7
Q

The human brain contains … neurons

A

10^11 neurons

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8
Q

One given neuron can have … synapses

A

1,000 synapses

10^11 x 10^3 = 10^14 synapses

  • the number of combinations of possible networks is almost infinite
  • the incredible ability of the human brain to process information, learn, solve complex tasks, have emotions…
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9
Q

Neural networks are for

A

information processing

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10
Q

3 stages for information processing

A
  1. sensory input
  2. integragion
  3. motor output
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11
Q

Integration

A

central nervous system of brain and spinal cord

sensory input and motor output

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12
Q
  1. integration
A

vertebrates have a central nervous system including the brain and spinal cord - the sites of most of the information processing, storage, and retrieval

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13
Q
  1. sensory input and 3. motor output are carried in and out of the CNS by
A

the peripheral nervous system

• includes sensory and effector (motor) neurons

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14
Q

Sensor to effector

A 
sensory   -->
sensory input (PNS)   -->
integration (CNS)   -->
motor output (PNS)   -->
effectore
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15
Q

Afferent neurons

A

Arrive sensory information to the brain
• carry sensory info to the nervous system
• sensory neurons - internal or external stimuli

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16
Q

Efferent neurons

A

information arrives at the Effectors
(eg motor neurons)
• carry commands to effectors such as muscles, glands
• motor neurons

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17
Q

Information processing is supported by neural networks

A
  • afferent neurons
  • efferent neurons
  • interneurons
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18
Q

Example of a simple neural network - the knee-jerk reflex

A
  • afferent (sensory) axons in a spinal nerve inter the spinal cord through the dorsal rot
  • efferent (motor) axons leave through the ventral root

• cell body in dorsal root
- long axon not in cell body
• dorsal = afferent
• ventral = efferent

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19
Q

Gray matter

A

rich in neural cell bodies

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20
Q

White matter

A

contains myelinated axons

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21
Q

Matter inside/outside

A

gray matter inside, white matter outside

- other way around in the brain

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22
Q

Spinal reflex

A

conversion of afferent to efferent information in the spinal cord without participation of the brain

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23
Q

Limb movements are coordinated by

A

antagonistic sets of muscles - flexors and extensors
• 1 muscle excites and 1 muscle contracts
(bc antagonist muscles opposite)

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24
Q

The coordination of antagonistic muscles is achieved by

A

an interneuron, which makes an inhibitory synapse onto themotor neuron of the antagonistic muscle

  • 1 contracts/flexes
  • 1 extends
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25
Information processing in the spinal cord
* interneuron decides flexor or extensor | * encode, process, store info to regulate physiological/behavioral
26
What cells are unique to the nervous system?
* CNS includes the forebrain and spinal cord * nervous system has 2 types of cells * • neurons * • glia, or glial cells
27
Neurons/nerve cells
• excitable - they generate and transmit electrical signals called ACTION POTENTIALS
28
Glia/glial cells
modulate neuron activity and provide support
29
Action potentials are
unidirectional | • dendrite --> axon
30
Action potentials are integrated in
the hillock | • integrates action potentials
31
The brain is mostly
interneurons
32
The neuron's structure depends on
function
33
Neurons have 4 regions
* cell body * dendrites * axon * axon terminals
34
Cell body
contains the nucleus and organelles
35
Dendrites
bring information to the cell body | • receive information from other neurons
36
Axon
carries information away from the cell body
37
Axon terminal
at the tip of the axon | • synapse with a target cell
38
Axons carry informatoin as
ationpotentials away from the originating cell body (presynaptic cell) to the receiving target cell (postsynaptic cell) UNIDIRECTIONAL
39
The plasma membranes of all neurons can
generate and conduct action potentials
40
Action potentials can travel at speeds up to
100 m/sec (360 km/hr)
41
The axon terminal comes extremely close to the membrane of
the target cell, forming a SYNAPSE
42
Dendrites in the retina are
small • information comes from a local area • doesn't need to store information for a long time
43
Some neurons branch over
a broad area
44
Axons with fewer dendrites
process fewer inputs
45
Bushy dendrites collect information from
many other cells
46
Some neurons communicate
over long distances via long axons
47
Electrical synapses allow the action potential to pass
directly between 2 neurons
48
Synapses can be
electrical or chemical
49
In vertebrates, most synapses are
chemical
50
The action potential arriving at the terminal causes it to release
neurotransmitter chemicals which diffuse to the receptors on the target cells
51
Glial cells outnumber neurons in the human brain by
10x
52
In the brain and spinal cord, glial cells are called
oligodendrocytes
53
Oligodendrocytes
wrap around neuron axons, forming the concentric layers of insulating plasma membrane
54
For the nerves (not CNS), glia is called
Schwann cells and wrap the axons
55
Insulating plasma membrane is
myelin • myelin is not continuous = nodes of Ranvier (jump makes faster)
56
Oligodendrocytes and Schwann cells produce
myelin that covers axons
57
Some diseases affect
myelin and impair conduction of action potentials
58
Multiple sclerosis
* an autoimmune disesase * antibodies to proteins in myelin in the brain and spinal cord are produced (motor impairment) * oligodendrocytes myelin
59
Disease that attacks Schwann cells myelin
Giullain-Barre syndrome
60
Glia that contribute to the blood-brain barrier
astrocytes
61
The blood-brain barrier
protects the brain from toxic substances in the blood
62
Astrocytes
* blood-brain barrier * take up and release neurotransmitters, and alter the activities of neurons * plasticity (memory)
63
Astrocytes store
glycogen that can be broken down to supply neurons with fuel • aid in repair and regeneration of neurons • make contact with both blood vessels and neurons, and can signal changes in the composition of the blood
64
Projections of 1 astrocyte may make contact with more than
100,000 synapses
65
Tripartite synapse
the idea that a synapse includes the pre- and postysynaptic neurons as well as connections from astrocytes
66
The blood-brain barrier typically prevents
antibodies form entering the brain and spinal cord
67
Microglia act as
macrophages and mediators of inflammatory responses, thus providing the nervous system with immune defenses • microglia = antibodies of the brain
68
The whole nervous system initially comes from
the ectoderm
69
The ectoderm gives rise to the
epidermis and neural plate
70
The neural plate will give rise to the
neural tube and the neural crest cells
71
The neural crest cells
lead the development of the connections between the CNS and the rest of the body
72
Nervous system process
The whole nervous system initially comes from the ECTODERM that gives rise tot he EPIDERMIS and the NEURAL PLATE. The NEURAL PLATE gives rise to the NEURAL TUBE and the NEURAL CREST cells that lead the development of the connections between the CNS and the rest of the body.
73
Future CNS =
forebrain + spinal cord

Cell Bio & Developmental Genetics (27 decks)

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