Lecture 5 Flashcards
1
Q
Name the two types of cells
A
Neurons and Glia
2
Q
What are neurons
A
Neurons are a type of cell that receives and transmits information to other cells.
3
Q
How many neurons does the adult brain have
A
Around 100 billion
4
Q
What are glia
A
A type of cell that has many functions and supports neurons in their function
5
Q
What are the 5 main parts in the structure of the neuron
A
Soma (cell body). Dendrites. Axon. Myelin sheath. Presynaptic Terminal.
6
Q
Describe the soma
A
Contains nucleus, ribosomes and mitochondria
7
Q
Describe dendrites
A
Branching fibres which receive info via synaptic receptors
8
Q
Describe axons
A
Thin fibre of constant diameter. Information sender of the neuron
9
Q
Describe myelin sheath
A
insulates the axon, nodes of ranvier: interruptions in the myelin sheath
10
Q
Describe presynaptic terminal
A
End bulb, bouton. Point from which axon transmits information
11
Q
Name the two types of axons
A
Afferent axons and Efferent axons
12
Q
What are afferent axons
A
Brings info to a structure
13
Q
What are efferent axons
A
Carries info away from a structure
14
Q
Name the two types of neurons
A
Sensory neuron. Motor neuron.
15
Q
What are sensory neurons
A
Afferent to the rest of the nervous system
16
Q
What are motor neurons
A
Efferent from the nervous system
17
Q
What are clusters within the neural structure of the nervous system made of
A
Cell bodies - CNS = nucleus, PNS = Ganglion
18
Q
What are glia
A
Smaller but more numerous than neurons (1:10) - with many supportive functions
19
Q
Do glia transmit information across long distances
A
no
20
Q
What do astrocytes do
A
Help synchronise the activity of neurons and remove waste materials
21
Q
What do microglia do
A
Remove waste materials and microorganisms
22
Q
What do oligodendrocytes and schwann cell
A
Build the myelin sheaths
23
Q
What do radial glia do
A
Guide the migration of neurons and the growth of their axons
24
Q
Name three body parts that protect the nervous system
A
Skull, backbone and meninges
25
Discuss the blood-brain barrier
It prevents viruses, bacteria, harmful chemicals from entering the brain. Depends on the endothelial cells that form the walls of the capillaries.
26
How can chemicals cross the blood-brain barrier
Cross the cells membrane.
27
What does the blood-brain barrier stop
Most viruses, bacteria and toxins. Large molecules and electrically charged molecules
28
What passes through the barrier
Small uncharged molecules - oxygen and carbon dioxide, water and fat-soluble molecules. Glucose, amino acids and some vitamins.
29
Name the two ways things can pass the blood-brain barrier
Passively or Actively
30
What is meant by something passing through the blood-brain barrier passiveky
No expenditure of energy
31
What is meant by something passing the blood-brain barrier actively
Expenditure of energy
32
What do neurons do
Receive information and convey it to other neurons
33
What do glia cells do
Serve many supporting functions, but do not convey information over larger distances
34
How do neurons conduct information
Via electrical impulses
35
How fast do neurons convey information
36
What do conduction of impulses depend on
Resting potential and action potential
37
What is the resting potential
At rest, neurons are more negative inside than outside. and the voltage difference is called the resting potential.
38
What is the typical resting potential
-70 millivolts (mV)
39
Name two negatively charged particles
Chloride ions and protein ions
40
Name two positively charged particles
Sodium ions and potassium ions
41
What are the four interacting factors that maintain the resting potential
Concentration gradients and electrical gradient. Membrane permeability at rest and sodium-potassium pump
42
Name the two homogenizing factors
Concentration gradients which are when Ions are in random motions and move from areas of high concentration to areas of low concentration. Electrical gradients which are the accumulation of charges repels like charges and attracts unlike charges
43
Describe concentration gradients
When ions are in random motion and move from areas of high concentration to areas of low concentration
44
Describe electrical gradient
Accumulation of charges repels like charges and attracts unlike charges (+ repels +, - repels -, + attracts -).
45
What are homogenizing factors counteracted by?
Membrane permeability at rest and sodium-potassium pump
46
Describe what it is meant by membrane permeability at rest
CL- and K+ pass, Na+ pass with difficulty and protein ions do not pass
47
Describe what the sodium-potassium pump does
Transports Na+ out and K+ in, but requires energy
48
What is an action potential
Response of a neuron to stimulation above a certain threshold
49
What does the resting potential do in terms on action potential
Resting potential prepares the neuron to respond quickly to a stimulus with an action potential
50
What does stimulation result in?
Depolarization
51
What is depolarization
The neuron becomes less negative
52
What happens when stimulation that results in a depolarization beyond the threshold of excitation
Results in a sudden, massive depolarization
53
What happens after depolarization
Potential returns to slightly below resting potential and back to the resting potential value
54
Define repolarization
When the potential returns back to the resting potential value
55
What does sub-threshold stimulation produce
Depolarization proportional to the strength of stimulation
56
What does stimulation above the threshold produce
A very similar action potential - all of non law: amplitude and velocity of an action potential are independent of the initiating stimulus
57
Describe the molecular basis of the action potential
Initial sodium enters the cell, and a bit later potassium leaves the cell, which makes it negative again - the sodium-potassium pump then restores the original ion distribution
58
What happens immediately after an action potential
The membrane area cannot produce another action potential
59
Define refractory period
When the membrane cannot produce another action potential as an action potential has just happened
60
What is it called immediately after an action potential, when a membrane cannot produce another action potential
Refractory period
61
What is meant by 'absolute refractory period'
No action potential can be produced
62
What is meant by 'relative refractory period'
Stronger than usual stimulus can initiate an action potential
63
When a stronger than usual stimulus can initiate an action potential what is that called
Relative refractory period
64
Describe the propagation of the action potential
Action potential begins at the axon hillock, action potential propagates along the axon
65
Describe the mechanism of propagation of the action potential
Slight depolarization of adjacent areas to reach its threshold. Then action potential is regenerated.
66
What is determined by the refractory period
Direction of propagation
67
Direction of propagation is determined by what
Refractory period
68
Describe the action potential conducion speed
It depends on the axon's diameter - thin axons are 1m/s but thick axons are 10m/s. Myelin sheath increases speed up to 100m/s - action potential jumps from node to node and thus increases speed and saves energy
69
Describe what is meant by saltatory conduction
Action potentials jump from node to node which increases speed and saves energy
70
What is a synapse
A side at which information flows from one neuron to another. The small gap between neurons.
71
What are the three main parts of a synpase
Presynaptic terminal. Synaptic cleft and postsynaptic neuron
72
What events happen at the synapse
Action potential arrives at the presynaptic terminal, where calcium enters and neurotransmitters are released into the synaptic cleft. Neurotransmitters attach to receptors and alter activity of the postsynaptic neuron. Neurotransmitters separate from their receptors and are taken up by the presynaptic cell or diffuse away
73
Describe the activation of postsynaptic receptors
Neurotransmitters attach to postsynaptic receptors via a key-lock-system, meaning there is a specific receptor for specific neurotransmitter
74
Describe Ionotropic receptors
Effect fast and short, neurotransmitter opens/closes channels directly.
75
What are iontropic receptors relevant for
Vision & hearing, being able to quickly change information
76
Describe metabotropic receptors
Effect slow & long, neurotransmitter activates G- protein within the cell, G-protein can bind to ion channels or stimulate synthesis of second messengers.
77
What are metabotropic receptors relevant for
Hunger, thirst, fear & anger (long-term changes in behaviour)
78
Describe the inactivation and reuptake of neurotransmitters
Break down by enzyme, detachment from receptor without break down - neurotransmitter taken up and reused by presynatpic neuron (reuptake)
79
Describe temporal and spatial summation
Neurons conduct information through action potentials, neurons communicate through synpases. One synapse does NOT initiate an action potential. (Postsynaptic potentials are graded potentials - the more stimulation, the larger the change). Action potentials can be initiated by temporal or spatial stimulation of excitatory postsynaptic potentials
80
Describe temporal summation
Summation of excitatory postsynpatic potentials from one source. Effect depends on - size of EPSP's, time between them and threshold of the postsynaptic neuron
81
Describe spatial summation
Summation of several simultaneous EPSP from separate locations, effect depends on - size of EPSP's, timing, and threshold of the postsynaptic neuron
82
Explain how cocaine has a psychoactive effect
Dopamine and norepinephrine agonist. It blocks the reuptake of dopamine and norepinephrine - both continue to activate postsynaptic receptors.
83
What are the effects of cocaine use
Euphoria, loss of appetite, insomnia and addiction
84
Explain how benzodiazepines have psychoactive effects
Diazepam & Chlordiazepoxide, GABA agonists. Increases the binding of BAGA molecules and thus inhibitory effect of GABA.
85
What are the effects of benzodiazepines
Reduce anxiety, induce sleep & reduce seizues
