Midterm 1 Flashcards
(323 cards)
1
Q
What’s a receptor protein?
A
- A protein that is sensitive to and capable of communicating some signal
- Sensitive to neurotransmitters and to outside stimuli (light, touch, smell, taste)
2
Q
What are the 2 types of receptor proteins?
A
- Ionotropic receptors
- Metabotropic receptors
3
Q
What’s an ionotropic receptor?
A
- A receptor protein that is an ion channel
- When they’re activated they have an immediate effect on the membrane potential of the neuron (they either produce excitatory post-synaptic potentials or inhibitory post-synaptic potentials)
- Ionotropic receptors always have a fast and immediate effect and these effects last no more than a millisecond
4
Q
What’s the excitatory post-synaptic potential?
A
if the pore of the ion channel lets in positively charged sodium that’ll depolarize the neuron and maybe encourage it to have an action potential
5
Q
What’s the inhibitory post-synaptic potential?
A
if other ionotropic receptors let in negatively charged chloride. This will hyperpolarize the neuron and decrease its likelihood of firing an action potential
6
Q
What’s a metabotropic receptor?
A
- A receptor that’s sensitive to something outside the cell and is not an ion channel
- These receptors typically trigger an intracellular signalling cascade that involves g proteins, which can produce a variety of cellular effects such as a change in gene expression or the opening/closing of g protein-gated ion channels
7
Q
Where does the name “g protein” come from?
A
It symbolizes that these proteins use GTP molecules, instead of ATP molecules, for the energy they need to perform chemical reactions
8
Q
When is a g protein at its “on”/activated state?
A
When it is bound to a GTP molecule
9
Q
When is a g protein at its “off”/inactivated state?
A
When it has converted GTP to GDP and is now clipped onto GDP molecules
10
Q
How do g proteins let go of GDP?
A
- By finding an activated metabotropic receptor which is one that’s bound to a neurotransmitter
- They use the intracellular side of an activated metabotropic receptor to pry off their GDP molecule
- When this happens, they bind another GTP molecule and the process starts over again
11
Q
What are G protein coupled receptors?
A
They use chemical reactions inside the cell to pass along a message
12
Q
What’s the relationship between g proteins and ion channels?
A
- We often see g proteins opening up ion channels to change the membrane potential to get a neuron to spike more or to spike less
- ## Some ion channels are normally closed and the only way they open is when activated g proteins come and bind to them intracellularly which causes them to open up and let ion channels to flow through
13
Q
What’s a G protein-gated ion channel?
A
Some ion channels are gated by g proteins, which are a family of intracellular proteins that are involved in intracellular signalling cascades
14
Q
What are advantages of metabotropic receptors?
A
- They can amplify a signal
- They can prolong a signal
15
Q
How do metabotropic receptors amplify a signal?
A
One neurotransmitter binding to one receptor can cause a massive change in the membrane potential because it’s causing activated g proteins to go and open up tons of ion channels at the same time
16
Q
Which type of receptor protein has a more dramatic effect on the cell? Metabotropic or Ionotropic?
A
- Metabotropic receptors can amplify the message and hence have more dramatic effects on the cell than ionotropic receptors do
- Ionotropic receptors have only one ion channel that opens or closes
- Metabotropic receptors also have a much more prolonged signal compared to ionotropic receptors
17
Q
How do metabotropic receptors prolong a signal?
A
- When metabotropic receptors are activated, the process will take a minimum of 30 milliseconds and only 100 milliseconds later do we begin to see the effects on the cell
- Once the effect occurs, the ion channels can stay open for a while until g protein let’s go of them which it can hang onto them for a while
18
Q
What are some downstream processes that G-protein signaling cascades can affect?
A
- opening g protein-gated ion channels
- changes in gene transcription
- secretion of substances from the cell
19
Q
Where are receptors usually located?
A
Located mostly on dendrites because they’re what’s sensing the external environment in the cell determining whether they should fire an action potential
20
Q
Where are the different places that synapses can form between axon terminals and …?
A
- dendrites (dendritic shafts) - > axodendritic synapse
- dendritic spines -> axodendritic synapse
- the soma (cell body) -> axosomatic synapse
- other axon terminals -> axoaxonic synapse
21
Q
What’s the neuraxis?
A
Neuraxis is the imaginary line that runs along the length of the brain and spinal cord (Central Nervous System)
22
Q
Why do we say that all animals with a nervous system are bilateral creatures?
A
Because they have bilateral symmetry and the middle part is where the spinal cord runs down the animal
23
Q
What does anterior mean?
A
In front
24
Q
What does posterior mean?
A
Behind
25
What does superior mean?
Above
26
What does inferior mean?
Below
27
What does rostral mean?
Towards the beak
28
What does caudal mean?
Towards the tail
29
What does dorsal mean?
Towards the back
30
What does ventral mean?
Towards the belly
31
What does lateral mean?
Away from the midline
32
What does medial mean?
Toward the midline
33
What's the Golgi stain?
- A mixture of silver nitrate and potassium chromate that causes 2% of brain cells to darken in colour as silver chromate crystallizes inside of them
- Using this stain to identify the structure of the nervous system and to label the neurons
34
What's the soma/cell body of a neuron?
Where the nucleus is located
35
What are the dendrites?
- Branched, treelike extensions from the soma
- They're responsible for sensing the external environment (for collecting information relevant to the cell)
36
What are axon terminals (or terminal buttons)?
- They're responsible for releasing neurotransmitter when there's an action potential
- They release neurotransmitter onto the downstream cells that they are in contact with
37
What's the axon?
- The axon is responsible for transmitting information (via an action potential) to downstream cells
- They're often insulated with fatty myelin sheaths, which improve the speed and fidelity of the action potential
38
What are different methods of orchestrating movement from a neuro cell?
- Diffusion method
- Directed transport: having a motor protein carrying something from one way or the other
- Electrical communication
39
How do we measure the resting membrane potential?
- It's measured with glass micropipets filled with solutions which conduct charge
- The micropipet is inserted through the membrane into the cell
- We also use a voltmeter that measures the difference in electrical charge between 2 points or the potential difference
- It's measured on a relative scale
- Measured in mVs (millivolts)
40
How many mV is the resting membrane potential in nerve and muscle?
Between -40 to -90 mV
41
Where is the reference electrode placed when measuring the resting membrane potential?
- Placed in the extracellular fluid which is designed as the ground and assigned a charge of 0 mV
- Extracellular fluid isn't neutral
42
Is the cell membrane permeable or impermeable in water?
Impermeable
43
What's an ion?
Charged atom or molecule
44
What's a cation ion?
Positively charged ion
45
What's an anion ion?
Negatively charged ion
46
What's the electrostatic pressure?
Attractive force between molecules that are oppositely charged (negative/positive) or repulsive force between molecules that are similar charged (positive/positive)
47
What are ion channels?
- Specialized protein molecules that sit in the cell membrane
- They have a pore (hole) in them through which specific ions can enter or leave cells
48
What are leak channels?
An ion channel protein that is in the membrane and has a pore that's always open
49
Do ions naturally cross the cell membrane?
No, they make proteins and they stick them in the membrane and these proteins will have a pore or hole through which specific ions can enter the cell
50
What are the main elements of a cell?
CHNOPS
- Hydrogen (H) 59%
- Oxygen (O) 24%
- Carbon (C) 11%
- Nitrogen (N) 4%
- Others (Phosphorus, sulfur,...) 2%
51
What are examples of positively charged ions?
Monovalent cations:
- Sodium (Na+)
- Potassium (K+)
Divalent cations:
- Calcium (Ca2+)
- Magnesium (Mg2+)
52
What are examples of negatively charged ions?
Chloride (Cl-)
53
Which ions are more abundant outside of cells (in the extracellular space)?
- Sodium
- Calcium
- Magnesium
- Chloride
54
Which ions are more abundant inside of cells (in the intracellular space)?
Potassium
55
What does monovalent mean?
1 charge
56
What does divalent mean?
2 charges
57
What happens if there is an equal concentration of positively and negatively charged ions on either side of the membrane?
Then,
- Outside of cell = 0 mV
- Inside of cell = 0 mV
- 0 electric potential
58
What 2 proteins are responsible for setting up and maintaining the resting membrane potential of neurons?
- Sodium-Potassium transporter
- Leak potassium channels
59
What's the Sodium-Potassium transporter (or sodium-potassium pump)?
- Concentrates sodium and potassium outside and inside the cell, respectively
- The function of this protein is to pump Sodium or Na+ atoms out of the cell and Potassium or K+ atoms in
60
Describe the Leak potassium channels
- They're always open
- The number of these channels largely determines the resting membrane potential
61
What concentration gradients does the Sodium-Potassium pump create?
- Causes K+ ions to be 30x more concentrated inside the cell than out
- Causes Na+ ions to be 15x more concentrated outside the cell than in
- These concentration gradients never change, ever, unless the cell dies
- There is no electrical charge difference yet (the membrane potential = 0), because there is a similar concentration of positive/negative ions inside and outside the cell
62
What ions are creating potential energy with regards to the sodium-potassium pump concentration gradient?
Potassium (K+) ions are creating potential energy related to the force of diffusion because K+ ions are crowded inside the cell, and they will leave if they can
63
What's the force of diffusion?
If there's a concentration gradient and no forces or barriers to prevent free movement of molecules, then molecules will move, on average, from regions of high concentration to regions of low concentration
64
When is the electrostatic energy of K+ equal and opposite to the diffusional force of K+ ?
When the inside of a cell reaches -90 mV
65
When a cell goes down to -90mV, what do we assume is in charge of this drop?
Leak channels
66
What's the membrane potential?
Electrical charge across a cell membrane; difference in electrical potential inside and outside the cell
67
What's the resting membrane potential?
- Membrane potential of a neuron when it's not being altered by signalling molecules that cause excitatory or inhibitory postsynaptic potentials;
- At rest, the membrane potential ranges between -40 and -90 mV across different types of neurons
68
What happens when a neuron has a lot of K+ channels?
The more K+ leak channels a neuron has, the more permeable it will be to K+ relative to other ions and the closer its membrane potential will be to -90 mV
69
What kind of stimuli in the external world do cells use proteins to detect?
- the presence of certain molecules (e.g., neurotransmitters)
- physical pressure (movement, touch)
- electrical pressure (voltage)
- temperature
- pH (acidity, basicity)
- electromagnetic radiation (light)
70
What's depolarization?
When the membrane potential of a cell becomes less negative than it normally is at rest
(Ex: -60 to -50 mV from influx of Na+ ions)
71
What happens when positive Na+ ions enter a neuron through an ion channel which causes membrane depolarization?
It causes K+ ions to immediately leave the cell through leak channels, which restores the resting membrane potential
72
What are the 5 proteins involved with the action potential?
- Sodium-Potassium transporter
- Leak potassium channels
- Voltage-gated sodium channel
- Voltage-gated potassium channel
- Voltage-gated calcium channel
73
What is the purpose of the Voltage-gated sodium channel in the action potential?
To initiate and propagate the action potential
74
What is the purpose of the Voltage-gated potassium channel in the action potential?
To restore the resting membrane potential
75
What is the purpose of the Voltage-gated calcium channel in the action potential?
- Located in the axon terminal
- Triggers release of neurotransmitter
76
Describe the voltage-gated sodium channel
- These ion channels are found all over the axon, along its entire length
- The channel is closed at resting potential
- The gate opens whenever the membrane potential becomes less negative than -40 mV
- Voltage-gated channels have electrical charges on their doors, such that they open or close when the charge difference across the membrane is greater or smaller than some number
77
Describe the what happens when Na+ channels open?
- The opening of an Na+ channel allows Na+ ions to rush in, propelled by both diffusion and electrostatic forces
- This influx of Na+ depolarizes the membrane further, which causes additional voltage-gated Na+ channels to open
- Soon there's an avalanche effect as all voltage-gated Na+ channels open causing the membrane potential to shoot up to +40mV
- Sodium goes in until the cell reaches +40 mV then it doesn’t wanna go in anymore, it’s happy
78
What's the action potential?
- The action potential is a brief electrical impulse that provides the basis for conduction of information along the axon
- It's a rapid change in the membrane potential caused by the opening and closing of voltage-gated ion channels
79
What's the threshold of excitation?
The value of the membrane potential that must be reached to produce an action potential
80
What triggers an action potential?
The initial depolarization that starts an action potential is usually driven by the activation of a receptor that lets Na+ ions enter
81
What's the membrane potential at the peak of the action potential?
- The membrane potential is +40mV
82
Why can't we rely on Potassium leak channels to end the action potential?
It would take too long
83
To speed up restoration of the membrane potential, what other voltage-gated ion channel does the cell use?
The voltage-gated potassium channel, which activate at the peak of the action potential
84
What's the refractory period?
A post action potential hyperpolarization, which is caused by all voltage-gated K+ channels not closing quick enough leading to the membrane falling below what it normally is at rest
85
Can you start another action potential immediately after one?
No, because of the refractory period, it becomes hard and takes longer to trigger another action potential right after one is completed
86
When do Voltage-gated K+ channels join in the action potential?
- They open in the middle of an action potential, when the membrane potential is around 0 mV.
- The opening of the voltage-gated K+ channels helps bring the membrane potential back down to -60 mV
87
The initial rising phase of the action potential reflects a sudden increase in membrane permeability of which ion?
Sodium (Na+), because the voltage-gated sodium channels are open
88
How can the speed of conduction of an action potential be calculated?
It can be calculated from the delay between the stimulus and the action potential
89
What's the concentration of calcium inside vs outside the cell?
Calcium is 1000x more concentrated outside the cell than in
90
When do voltage-gated calcium channels open?
when the axon terminal becomes depolarized (i.e., in response to an action potential).
91
What's the primary means of communication between neurons?
Synaptic transmission
92
What's synaptic transmission?
- Transmission of messages from one neuron to another via the presynaptic release of a chemical (a neurotransmitter) that crosses the synapse and binds to receptors located on the post-synaptic membrane
- It operates by diffusion
93
What happens when voltage-gated calcium channels open?
- The influx of calcium causes several synaptic vesicles to simultaneously fuse with the presynaptic membrane
- Upon fusion, these vesicles break open and spill their contents into the synaptic cleft
94
In what direction does conduction of the action potential occur?
In a unidirectional manner
95
What's the rate law?
The rate law states that the strength of the stimulus is represented by the rate of the firing axon
96
Which protein involved in the action potential requires ATP?
Sodium-Potassium transporter
97
What's a protein?
a long chain of amino acids that fold up into complex 3 dimensional structures
98
How do you make a hole in membrane (potassium ion channel) that lets in a bigger ion (potassium) but not a smaller one (sodium)?
- Voltage-gated potassium channels are 4 proteins coming together to make a hole
- When zooming in on amino acids there are some bumps on them that make it so that different ions can enter (bigger ones rather than smaller ones)
- Bigger ions can enter rather than smaller ions is due to the water (hydration shell) -> these charges want to be balanced and this shell of water will cover them to balance them
- Carbonyl groups are spaced exactly to remove the hydration shell from the potassium which is a perfect fit with the carbonyl groups. But sodium ions are too small and don’t fit in these carbonyl groups so they can’t pass
- Sodium is covered in the hydration shell because it’s not the perfect fit so instead of going through it, it just floats away
99
When wanting to make a gene, what cells to scientists usually use?
- The egg cell from frogs’ ovaries (huge cells easy to see) and these don’t have ion channels
- People take out the eggs of the frog and stick in the gene that they want to study
100
What's a gene promoter?
- A region of DNA that initiates transcription of a particular gene
- Indicates what kind of cells should read the gene and when.
- Promoters are typically located just before the gene
101
How many genes does the human genome contain for the voltage-gated potassium channel?
- 40 distinct genes that code different voltage-gated potassium channels
- Each cell can choose to express one or any combination of them to optimize cell function
102
What's neuroglia (or glia cells)?
- Glia are found all around neurons and even physically encapsulate some parts of them
- They help traffic nutrients and maintain molecular (ionic) stability in the extracellular space
- They support many functions of the nervous system
- It's estimated that they outnumber neurons in the brain
103
What are 3 types of glia cells?
- Astrocyte
- Microglia
- Oligodendrocytes
104
What's an astrocyte?
- A glial cell that provides physical support and cleans up debris in the brain through phagocytosis
- They control the chemical composition of the surrounding environment and help nourish neurons
105
What's a microglia?
- The smallest of the glial cells
- They provide an immune system for the brain and protect the brain from invading microorganisms
106
What are Oligodendrocytes?
- Glial cells that produce the myelin sheath, which surround many axons in the central nervous system
- The sheath is not continuous; it is a series of segments
- Speed up action potentials
107
What's the node of Ranvier
The exposed axon between the myelin sheaths
108
What are the processes formed by oligodendrocytes shaped like?
Like canoe paddles
109
What's the only place along a myelinated axon that comes into contact with extracellular fluid?
At the node of Ranvier
110
What's saltatory conduction?
- the conduction of action potentials by myelinated axons
- Action potential appears to jump from one node of Ranvier to next
- At each node, the strength of the signal is regenerated with additional voltage-gated Na+ channels
111
The transmission of what kind of sensory information is very slow for the action potential?
The transmission of pain information, as the cell for pain takes much longer (full second to get to the brain) when you touch heat
112
What's a synapse?
A junction between the axon terminal of the sending neuron and the cell membrane of the receiving neuron
113
How is communication across the synapse achieved?
- By the release of a molecule (neurotransmitter) from an axon terminal
- This molecule can have a simple excitatory or inhibitory effect or a complex modulatory effect on the receiving neuron
114
What's the presynaptic membrane?
- The membrane of the terminal button (the sending cell)
- This is where neurotransmitter is released from
- Presynaptic side is the one that sends off information
115
What's the postsynaptic membrane?
- The membrane of the receiving cell that is opposite the axon terminal
- Postsynaptic side is the one that receives info
116
What's a synaptic vesicle?
- Synaptic vesicles contain molecules of neurotransmitter
- They attach to the presynaptic membrane and release neurotransmitter into the synaptic cleft
117
What's the synaptic cleft?
The space between the pre and postsynaptic membranes
- It's filled with an extracellular fluid
118
What's an electron microscopy?
An electron microscopy allows us to see small anatomical structures (e.g. synaptic vesicles and details of cell organelles) using a special electron microscope
119
What's the neuromuscular junction?
Where a neuron is attached to a muscle
120
What's a ligand?
- A signaling molecule that binds to the binding site of a receptor
- Most cell signaling and cell communication occurs through ligand-receptor interactions
- Neurotransmitters are ligands
121
What are the 2 categories of neurotransmitter receptors?
- Ionotropic receptors
- Metabotropic receptors
122
Where can receptors be located?
- On the cell membrane (surface receptors)
- Inside the cell (intracellular pool of receptors)
123
Neurotransmitter receptors are generally what kind of receptors?
Surface receptors
124
Where are postsynaptic receptors located?
They're located on the postsynaptic membrane
125
Where are presynaptic receptors located?
They're located on the presynaptic membrane
126
Where are extrasynaptic receptors located?
They're located somewhere near but outside the synapse
127
What's a neurotransmitter?
A signaling molecule that will bind to a receptor
128
What 3 ion channels do ionotropic receptors comprise of?
- leak channel
- voltage-gated ion channel
- ligand-gated ion channel
129
What's a binding site?
Location on a receptor protein to which a ligand binds
130
What's a postsynaptic receptor?
Receptor protein in postsynaptic membrane of a synapse that contains a binding site for a neurotransmitter
131
What's the ligand-gated ion channel
- A receptor that is an ion channel, AKA an ionotropic receptor
- The ion channel opens when the ligand (e.g., the neurotransmitter) binds to it
132
Neurotransmitter signaling in the synapse is kept brief by which two mechanisms?
- Enzymatic deactivation
- Reuptake
133
What's enzymatic deactivation?
- The destruction of a neurotransmitter by enzyme after its release
- Usually cuts them in half to destroy them
134
What's reuptake?
The reentry of a neurotransmitter just liberated by a terminal button back through its membrane, thus terminating postsynaptic potential
135
What's the postsynaptic potential?
Alterations in the membrane potential of a postsynaptic neuron, produced by neurotransmitter release into the synapse and receptor activation
136
What are the two forms that postsynaptic potentials can take?
- Excitatory (influx of positive sodium ions depolarize the cell)
- Inhibitory (influx of negative chloride ions hyperpolarize the cell)
137
What's hyperpolarization?
When the membrane potential of a cell becomes more negative than it normally is at rest
(Ex: Influx Cl- ions can hyperpolarize a neuron from -60 to -70 mV)
138
Describe what the excitatory postsynaptic potential (EPSP) is?
Brief depolarization of the membrane potential, typically caused by neurotransmitter activation of ionotropic receptors that let in positively charged sodium ions
139
How can EPSPs trigger an action potential without Potassium leak channels getting in the way?
- Many EPSPs have to occur at nearly the same time
- Sodium ions have to come in at a faster rate that potassium ions can leave in order to depolarize the membrane to the threshold of activation
- This depolarization has to reach the beginning of the axon (the axon hillock) where voltage-gated sodium channels are congregated and can trigger an action potential
140
Describe what the inhibitory postsynaptic potential (IPSP) is?
Brief hyperpolarization of the membrane potential, typically caused by neurotransmitter activation of ionotropic receptors that let in negatively charged chloride ions
141
What's the interaction of the excitatory and inhibitory synapses on a particular neuron called and describe it?
- Neural integration
- Describes how when EPSPs and IPSPs occur at the same time, the influx of negatively charged chloride ions diminish the impact of the positively charged sodium ions. IPSPs hence decrease the likelihood that the cell will fire
142
What determines the direction of the postsynaptic potential (EPSP vs IPSP)?
- The receptor
- It's up to the postsynaptic cell to determine how it wants to respond to the signaling molecule
143
What on the ion channel or ionotropic receptor, will determine if it causes EPSPs or IPSPs?
The properties of the pore
144
Where do all sensory neurons carry information to?
The spinal cord. So if you burn your finger, the sensory neurons have to travel up to your spinal cord before it can trigger an action since there are no sensory neurons on your fingers
145
What's the process that occurs when a human comes in contact with a hot object?
-The dendrites of a sensory neuron are stimulated by a noxious stimulus (such as contact with a hot object)
- It sends messages down the axon to terminal buttons located in spinal cord
- The sensory neuron will activate an interneuron, which in turn will active a motor neuron and cause a withdrawal reflex
146
What are the 3 main ways to cut a brain?
- The coronal section (or transverse plane)
- The sagittal plane
- Horizontal plane
147
What's the mid-sagittal cut?
- A mid-sagittal cut means the exact middle (between the eyes)
- The only cut that actually cuts the brain in half
148
What's the coronal section cut?
Most common brain slice used in neuroscience is the coronal section (cutting the ears)
149
What does contralateral mean?
Structures on opposite side of the body (e.g. the motor cortex controls movements of the contralateral hand)
150
What's contralateral organization?
One side of the brain controls the other side of the body
151
What does Ipsilateral mean?
- Structures on same side of body (e.g. taste information is processed ipsilaterally, which means that taste receptors on the left side of your tongue are processed by your left cerebral hemisphere)
- Taste and smell are the only sensory systems that do not have contralateral organization
152
What does superficial mean?
Located close to the surface, close to the exterior of the animal
153
What does deep mean?
located far away from the surface, deep in the interior of the animal
154
What's the difference between proximal and distal?
Proximal – nearby
Distal – far away
155
What's the brain nuclei?
In the brain, the word nuclei means a collection of neurons that are clustered together that all work together to serve some function
Ex: there are many different brain nuclei in the hindbrain. One controls breathing, another controls vomiting, etc.
156
What are the 2 parts of the nervous system?
- Central nervous system
- Peripheral nervous system
157
What's the central nervous system?
Comprises of everything in the brain and spinal cord
158
What's the peripheral nervous system?
- Any part of the nervous system outside the brain and spinal cord, including the nerves attached to the brain and spinal cord
- This is sensory information (that goes into your skin) and motor information (that goes to your muscles)
159
How is myelin created in the central nervous system vs in the peripheral nervous system?
- Central nervous system: created by Oligodendrocytes
- Peripheral nervous system: created by Schwann cells
160
How many myelin sheaths do Oligodendrocytes make VS Schwann cells?
- Oligodendrocytes makes about 50 myelin sheaths
- Each Schwann cell only makes 1 myelin sheath
161
Why is the fact that there are different cells in the CNS and PNS that create myelin sheaths an important distinction between the 2 nervous systems?
Because if there’s a neurological disorder where the immune system begins to attack Schwann cells, you’re going to lose your myelin sheaths in the peripheral nervous system but it won’t affect myelin sheaths in the central nervous system
162
What's the difference between the circulatory system in the PNS vs in the CNS?
- Throughout the body there are holes in our blood vessels, in our capillaries, allowing blood to leak out. When this blood leaks out, it forms the extracellular fluid of all the cells in the body
- The brain doesn’t like this system, so all blood vessels going through the brain and spinal cord don’t have holes in them and so there’s no blood leaking out (blood-brain barrier). The brain is hence not getting its extracellular solution directly from the blood and has to make it in its own way
- If the brain wants something out of the blood, it actively has to take it out because nothing else will leak through
163
What's the blood-brain barrier?
- Semipermeable barrier between the blood and the brain
- Absence of holes in the blood vessels
164
What's lymph?
The extracellular fluid of the body that flows around cells providing nutrients and collecting waste, which is then collected into lymph vessels and brought to lymph nodes / lymph organs
165
What's the function of lymph nodes and lymph organs?
- They largely have an immune function, as they’ll assess the lymph solution (analyze it for immune functions) to see if there are any invading organisms, any foreign particles, anything the immune system has to be aware of
- They’ll then break down the garbage and drop it all back into the blood and start again
166
What's cerebrospinal fluid?
Rather than letting blood leak out, the brain simply makes its own extracellular solution by picking out exactly what it needs from the blood
167
What are the 3 types of meninges?
- The dura mater
- The arachnoid membrane
- The pia mater
168
Where's the subarachnoid space?
between the arachnoid membrane and pia mater
169
Describe the dura mater
- The outer layer right beneath the bone
- It's thick, tough, unstretchable tissue
170
What are meninges?
Tough, protective connective tissues that surround the brain and are right beneath the skull
171
Describe the arachnoid membrane
- The middle layer
- It's soft and spongy and has a web-like appearance
- Provides a cushion to the brain, as the brain jostles around it can kind of mush these blood vessels without causing any damage
172
Describe the pia mater
- Third layer that sits closest to the brain
- This layer and the space above it has blood vessels in it
- A really thin protective wrapping
173
What is cerebrospinal fluid made by?
Choroid plexus
174
What's choroid plexus?
- A tissue that's lining each of the brain ventricles (i.e., the 4 interconnected hollow spaces within the brain)
- For blood vessels that come around these ventricles, the choroid plexus takes that blood and picks out exactly what it wants from it to make the cerebrospinal fluid
175
What are the 4 brain ventricles?
- 2 lateral ventricles
- Third ventricle
- Fourth ventricle
176
Describe the 2 lateral ventricles
- They're the largest
- They sit underneath the cerebrum or cerebral cortex
177
Describe the third ventricle
It lies between the two thalamic nuclei
178
Describe the fourth ventricle
It sits between the pons and cerebellum
179
What's the cerebral aqueduct?
A long, tube-like structure that connects the third and fourth ventricle
180
What's the trajectory of cerebrospinal fluid in the brain?
The cerebrospinal fluid can flow through the neurons or it can flow down and around the brain and all the subarachnoid space. It’ll flow down and around the whole spinal cord and back up and then it’s collected and brought into blood vessels to be disposed of
181
What's an interneuron?
The word interneuron is only used for CNS neurons whose axon stays local (it only makes synapses on nearby neurons)
182
What's a projection neuron?
The term projection neuron is used when the axon of a cell goes outside the area where its soma is located
183
What are the 2 parts to the peripheral nervous system?
- Sensory neurons
- Motor neurons
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What are efferent fibers?
- Fibers that bring information away from … (the CNS)
- They're the "outputs"
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What are afferent fibers?
- Fibers that bring information towards … (the CNS)
- They're the "inputs"
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Where are motor neurons located?
- The actual cell body (and its dendrites) of a motor neuron is located in the spinal cord (central nervous system)
- Its axon is located in the peripheral nervous system (myelinated by schwann cells)
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What do motor neurons do?
They control muscle contraction and gland secretion
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Where are sensory neurons located?
Sensory neurons are entirely in the peripheral nervous system
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What do sensory neurons do?
They detect changes in the external (outside world) and internal (the body) environment
190
What's the difference between spinal nerves and cranial nerves?
- Spinal nerves come off your spinal cord
- Cranial nerves come off the brain directly
191
How are the brain and spinal cord connected to the peripheral nervous system?
- Through nerves
- Nerves are what make up the peripheral nervous system -> once they leave the brain or spinal cord and they exit they’re then part of the peripheral nervous system
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What are nerves?
- A nerve is a sheath of tissue that encases a bundle of axons (or nerve fibers) (bundles of bundles of axons)
- These bundles of bundles of axons are wrapped up in a lot of protective tissue called collagen that’s full of blood vessels to provide oxygen and nutrients
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What are the different directions nerves usually move in?
- Nerves are either coming from the spinal cord and going to muscle (efferent fibers)
- Or they’re coming from the skin sensing stuff and bringing information towards the brain (ex: funny bone)
194
How do the brain and spinal cord communicate with the rest of the body?
Via nerves: cranial nerves and spinal nerves
195
How many pairs of spinal nerves are there?
There are 31 pairs of spinal nerves attached to the spinal cord, about 1 pair for each vertebrae
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How many pairs of cranial nerves are there?
- There are 12 pairs of cranial nerves that attach to the ventral surface of the brain
- All the cranial nerves except the 10th serve sensory and motor functions of head and neck region
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What's the vagus?
- The 10th cranial nerve, also called the “wandering” nerve because its branches wander throughout thoracic and abdominal cavities
- It regulates functions of the heart, lungs, upper digestive track, and other organs in that area
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What's the principal function of the spinal cord?
- Its principal function is to distribute motor fibers to the effector organs of the body (glands and muscles) and to collect somatosensory information to be passed on to the brain
- It also has a certain degree of autonomy from the brain; various reflexive control circuits are located there
199
Describe how efferent and afferent motor fibers interact in the spinal cord?
Efferent motor fibers and afferent sensory fibers leave/enter the spinal cord in different areas, but as soon as they get away from the spinal cord and go out toward the rest of the body, they’re all bundled together
200
What's the gray matter on the spinal cord?
It's where cell bodies are, where the somas are for all the neurons
201
What are the 2 sections of the peripheral nervous system?
- Somatic nervous system
- Autonomic nervous system
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Describe the Somatic nervous system
- It senses and interacts with the external environment
- Controls skeletal muscle movements and processes sensory information that relates to the outside world
- Often associated with conscious processes
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Describe the function of the afferent nerves in the somatic nervous system
They carry sensory signals from eyes, ears, skin, etc TO CNS
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Describe the function of the efferent nerves in the somatic nervous system
They carry motor signals FROM CNS to skeletal muscles
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Describe the function of the efferent nerves in the autonomic nervous system
They carry motor signals FROM CNS to internal organs
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Describe the function of the afferent nerves in the autonomic nervous system
They carry sensory signals from internal organs TO CNS
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Describe the autonomic nervous system
- Regulates the body’s internal
environment
- Concerned with sensation and regulation of smooth muscle, cardiac muscle, and glands
- Usually associated with automatic or reflexive processes
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What are the 2 parts that the autonomic nervous system efferent branch is spilt up into?
- the parasympathetic nervous system
- the sympathetic nervous system
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Describe the sympathetic nervous system
- Primes the body for action, particularly in life threatening situations (e.g., it mediates the flight-fight-freeze response when animals are threatened)
- It's always active to some extent, as it regulates heart rate, blood flow, and the activity of almost every organ in the body
- But when acutely stimulated, it shunts blood away from the organs that are not necessary for immediate survival and increases blood flow to the organs involved in intense physical activity
- When people have the sympathetic division of the nervous system activated, they generally lose sexual arousal, lose hunger and are in a state of stress or panic and they’re mobilized to react
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Describe the parasympathetic nervous system
- Supports activities that occur when the body is in a relaxed state and all is well
- It's generally involved with increasing the body's energy stores (i.e., digestion)
- Its functions also include sexual arousal, defecation, urination, and salvation
- Involved in "feed and breed" and "rest and digest" activities.
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What are the 3 major divisions of the brain?
- Forebrain
- Midbrain
- Hindbrain
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What are the principal structures of the forebrain?
- Cerebral cortex
- Basal ganglia
- Limbic system
- Thalamus
- Hypothalamus
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What are the principal structures of the midbrain?
- Tectum
- Tegmentum
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What are the principal structures of the hindbrain?
- Cerebellum
- Pons
- Medulla oblongata
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What ventricle do each major divisions of the brain get their cerebrospinal fluid from?
Forebrain: Lateral & Third
Midbrain: Cerebral aqueduct
Hindbrain: Fourth
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Describe the medulla oblongata
- It contains a collection of brain nuclei that regulate different autonomic (involuntary) functions, such as heart rate and blood flow, breathing, vomiting, sneezing, etc.
- Area postrema is a famous part of the medulla, as the blood–brain barrier is noticeably weak here.
- Also contains part of the reticular formation, which plays an important role in sleep and arousal
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Describe how the area postrema is unique and beneficial to our survival
- The area postrema has a noticeably weak blood-brain barrier as this part of the brain works with vomiting and hence if blood that contains poison can leak out here, the neurons around this area will detect the toxins or poisons and trigger a vomiting reflex
- The brain is almost absolute in its blood-brain barrier except for spots like the area postrema that allows the brain to gain control of vomiting
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Describe the pons
- A large bulge in the brain stem that relays information between the cerebrum and cerebellum (relay structure)
- It also contains part of the reticular formation as well as several cranial nerve nuclei, which participate in hearing, balance, taste, and sensations and movements of the face
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Describe the cerebellum
- Plays an important role in motor control
- Doesn't initiate movement, but it contributes to its coordination, precision, and accurate timing
- Integrates sensory information and motor commands to exert a coordinating and smoothing effect on movement (and cognition)
- Plays an important role in motor learning, particularly when parts of the body grow and change (which necessitate adjustments in sensorimotor integration)
- Involved with moment-to-moment reflexive movements
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What are the symptoms of cerebellar damage?
Cerebellar damage primarily results in jerky, poorly coordinated, exaggerated movements. Leads to issues with balance. Extensive cerebellar damage makes it impossible even to stand.
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Which major division of the brain is the most caudal division?
The hindbrain
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Describe brain development in humans?
- A hollow, enclosed neural tube forms during 1st month of human development. The 1st cells are neural progenitor cells, and they initially only exhibit symmetrical cell division: each cell becomes two of the same type.
- This period of symmetrical cell division ends and asymmetrical cell division starts 40 days after conception
- Over next 85 days, each time a neural progenitor cell divides, it produces one neural progenitor cell and either one neuron or one glial cell
- By day 125 after conception, there are over 100 billion neurons in the human brain
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What's nerogenesis?
- The production of new neurons
- Neural progenitor cells produce neurons when they undergo asymmetrical cell division.
- Human neurogenesis largely stops 4 months after conception
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What's apoptosis?
- A process of programmed cell death that occurs in multicellular organisms
- Highly regulated and controlled form of cell suicide that ensures a dying cell doesn't cause problems for its neighbors
- Human neural progenitor cells undergo apoptosis 125 days after conception
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What's the function of the Midbrain?
A collection of nuclei that orchestrate complex reflexive behaviours, such as species typical responses to threat and pain, as well as orienting responses to sounds and lights
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Describe the tectum ("roof")
- Involved with orienting reflex
- Appear as two pairs of bumps on the dorsal surface of the midbrain
- Top 2 bumps are the superior colliculi
- Bottom 2 bumps are the inferior colliculi
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What's the superior colliculi?
Involved in orienting the animal to things seen in peripheral vision
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What's the inferior colliculi?
Involved in orienting to unexpected sounds
229
Describe the tegmentum
- Includes several structures that coordinate and motivate complex species-typical movements
- Some areas process pain and orchestrate behavioural responses to threats
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What is the pons related to in the forebrain?
The thalamus
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What is the medulla oblongata related to in the forebrain?
Hypothalamus
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What is the cerebellum related to in the forebrain?
Cerebral cortex
233
Describe the hypothalamus
- Generally regulate autonomic nervous system activity
- Critically involved in behaviours that directly relate to survival (i.e. the four F’s: feeding, fighting, fleeing and mating)
- Different hypothalamic nuclei control body temperature, sleep-wake cycles, hunger, and social behaviour, among other things
- One of the most important functions is to link the nervous system to the endocrine system (release of hormones into the blood stream) via the pituitary gland
- Controls sexual arousal and aggression
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What's an endocrine gland?
- Gland that secretes chemical signals (hormones) into the bloodstream
- Much of endocrine system is controlled by hormones produced by cells in hypothalamus
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What's the difference between brain signaling molecules & blood signaling molecules?
- Brain signaling molecules: neurotransmitters
- Blood signaling molecules : hormones
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What's a hormone?
A chemical substance that's released by an endocrine gland and that has effects on target cells in other organs
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Describe the thalamus
- Another bilateral structure that is divided into several nuclei, many of which relay ascending sensory information to different regions of the cerebral cortex
Ex: visual information from the eye passes through the thalamic lateral geniculate nuclei, whereas sound information from the ear passes through the thalamic medial geniculate nuclei
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Describe the cerebral cortex
- The largest site of neural integration in the central nervous system
- Plays a key role in attention, perception, awareness, thought, memory, language, decision making, and consciousness
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What are the 4 lobes to the cerebral cortex?
- Frontal lobe
- Parietal lobe
- Occipital lobe
- Temporal lobe
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What's the difference between the longitudinal and lateral fissure?
- The longitudinal fissure separates the two hemispheres
- The lateral fissure separates frontal from the temporal lobe
241
What's the central sulcus?
A good landmark separating the rostral and caudal divisions of the cerebral hemisphere
242
What's the function of the frontal lobe?
Controls movement
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What's the function of the parietal lobe?
Processes touch information
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What's the function of the occipital lobe?
Processes visual information
245
What's the function of the temporal lobe?
Processes auditory information
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Where are taste and smell processed?
- Near the junction of the frontal, parietal, and temporal lobes inside the lateral fissure
- Taste is processed in insular cortex
- Smell is processed in piriform cortex
247
What are the basic molecules of life/found in cells ?
- Water
- Sugar
- Lipid
- Nucleic acid
- Amino acid
248
Describe the primary motor cortex
- In the frontal lobe
- Contains the motor neurons that synapse in the spinal cord
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Describe the somatosensory cortex
- In the parietal lobe
- Where touch information first enters the cerebral cortex
- Different regions of the somatosensory cortex receive information from different parts of the body (e.g. feet, hands, fingers)
250
Describe the primary visual cortex
- In the occipital lobe
- Where visual information first enters the cerebral cortex
251
Describe the auditory visual cortex
- In the temporal lobe
- Where auditory information first enters the cerebral cortex
252
Describe the insular cortex
- Hidden in the lateral fissure
- Where gustatory information first enters the cerebral cortex
253
What happens when you damage a primary cortical area?
You lose conscious perception or control of the area
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What's the sensory association cortex?
- Each primary sensory area of the cortex sends information to adjacent regions called the sensory association cortex
- Perception takes place there and memories are stored there
- Regions of the association cortex located closest to primary sensory areas receive information from only one sensory system
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Describe the basal ganglia
- Collection of nuclei in the forebrain (located beneath the lateral ventricles).
- As a circuit, they regulate intentional movements, motivation, reinforcement learning, and habits
- Many neurological disorders (classic “movement” disorders) are associated with basal ganglia dysfunction
Ex: Parkinson’s disease relates to the loss of dopamine signaling in the basal ganglia
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What are the basal ganglia and limbic system often referred to as?
Subcortical structures, since they sit beneath the cerebral cortex
257
Describe the limbic system
- Regulates emotions and episodic memories
- Comprised of several distinct, interconnected structures, including the hippocampus, amygdala, and cingulate cortex
258
What's the main function of the hippocampus?
Critical for explicit memory formation
259
What's the main function of the amygdala?
Critical for feeling and recognizing emotions, particularly fear
260
What are the 6 classical neurotransmitters?
- Glutamate
- GABA
- Dopamine
- Norepinephrine
- Acetylcholine
- Serotonin
261
What's the main excitatory neurotransmitter?
Glutamate
262
What's the main inhibitory neurotransmitter?
GABA
263
What are the main neuromodulators?
- Dopamine
- Norepinephrine
- Acetylcholine
- Serotonin
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What's a neuromodulator?
Neuromodulators primarily act on metabotropic receptors and tend to exert more of a modulatory influence on postsynaptic cell activity (rather than causing fast EPSPs or IPSPs)
265
More than 99% of neurons release one of which 2 neurotransmitters?
- Glutamate
- GABA
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Describe glutamate and its agonist/antagonist effects
- Typically excitatory (the gas pedal)
- Ionotropic glutamate receptors induce excitatory post-synaptic currents (EPSCs) and membrane depolarization, perhaps an action potential
- Agonists: often cause seizures and excitotoxicity (kainic acid, NMDA)
- Antagonists: dissociative anesthetics (ketamine, PCP)
267
Describe GABA and its agonist/antagonist effects
- Typically inhibitory (the brakes)
- Ionotropic GABA receptors induce inhibitory post-synaptic currents (IPSCs) and membrane hyperpolarization
- Antagonists: often cause seizures
- Agonists: anesthetics, anticonvulsants, muscle relaxants, sleeping pills, anti-anxiety (alcohol, barbiturates, benzodiazepines)
268
What's acetylcholine related to?
Attention & memory
269
What's dopamine related to?
Fine motor movements
270
What's serotonin related to?
Mood & depression
271
What's noradrenaline related to?
Attention and cognition
272
Where are neuromodulators acting?
Everywhere
273
What's the difference between noradrenaline & norepinephrine VS adrenaline & epinephrine?
- Noradrenaline & norepinephrine: mostly used as a neurotransmitter in the CNS
- Adrenaline & epinephrine: mostly used as a hormone in the body
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What are the different types of neurotransmitters?
- Conventional neurotransmitters (glutamate, GABA, dopamine, serotonin, norepinephrine, acetylcholine)
- Neuropeptides (oxytocin, vasopressin, enkephalin, prolactin, NPY, ghrelin, CRH)
- Lipid-based signaling molecules (the cannabinoids anandamide and arachidonoyl glycerol)
275
Which neurotransmitters are monoamines?
- Serotonin (indolamines)
- Dopamine (catecholamines)
- Norepinephrine (catecholamines)
- Each of these neurotransmitters has its own reuptake transporter protein, which traffics the neurotransmitter from the synapse back into the axon terminal
276
What person advanced the field of neuroscience the most?
Charles Darwin
277
When was the formation of the first atoms in the timeline of our universe?
During the afterglow light (red glow)
278
What does tolerance mean?
- When an effect of the drug diminishes because of repeated administration
- It's the body’s attempt to compensate for the effects of the drug
279
What does sensitization mean?
occurs when a drug becomes more and more effective through repeated use
280
What are withdrawal symptoms?
opposite effects of the drug (i.e., euphoria vs dysphoria)
281
How does heroin enter the brain?
Crosses the blood-brain barrier quickly because it is very lipid (fat) soluble
282
How does morphine enter the brain?
Crosses the blood-brain barrier a bit slower because it is less lipid soluble
283
How does Imodium Anti-Diarrheal enter the brain?
Does not cross the blood-brain barrier
284
Drugs that pass the blood brain barrier very quickly have higher chances of being what?
Addictive
285
What are 3 very strong opiates?
- Morphine
- Heroin
- Imodium Anti-Diarrheal
286
Motor neurons generally release what as their main neurotransmitter?
Acetylcholine
287
Sensory neurons generally release what as their main neurotransmitter?
Glutamate
288
What's Botulinum Toxin (Botox)?
It's an acetylcholine system antagonist, because it prevents the release acetylcholine causing muscle paralysis
289
What kind of drug administration do we usually do when we want the drug concentration to be really intense really fast?
Intravenous injection administration
290
What kind of drug administration will release large amounts of a drug slowly (more natural)
Intramuscular and subcutaneous injections
291
What's neostigmine?
- Drug that inhibits activity of acetylcholinesterase, which is the enzyme that breaks down acetylcholine in the synaptic cleft. Neostigmine causes acetylcholine to hang around in the synapses for a longer period of time
- Famous drug that targets the neuromuscular junction
292
What's the difference between exogenous and endogenous?
- Exogenous: comes from outside the body
- Endogenous: something within the body that’s made normally, comes from within
293
What are antipsychotics/neuroleptics?
- Class of drugs used to treat psychosis
- They're mostly dirty drugs, which means they bind to more than 1 type of receptor, but the one action they all have in common is they directly block the dopamine D2 receptor, which is an inhibitory metabotropic receptor expressed by neurons all over the brain
294
What are the 4 drugs that directly activate serotonin 2A receptors and which are Hallucinogens and which are not?
- mescaline (hallucinogen)
- psilocybin (hallucinogen)
- LSD (hallucinogen)
- lisuride (non-hallucinogen)
295
What's Biased agonism?
When a metabotropic receptor ligand causes the receptor to preferentially activate one type of intracellular g protein, whereas another ligand at the same receptor might preferentially activate a different g protein
296
What are Allosteric modulators?
Non-competitive drugs that only influence receptor activity when the neurotransmitter is also bound to the receptor.
297
What kind of drugs are very powerful drugs?
Non-competitive antagonists are very powerful drugs, because it doesn’t matter how much dosage you give, every molecule of drug that finds its receptor will prevent that receptor from opening and it doesn’t matter how much normal neurotransmitter is there
298
What's the treatment for Parkinson's disease?
Injecting L-Dopa
299
What are 6 techniques to studying the human brain?
- Computerized tomography scan
- Magnetic resonance imaging (MRI)
- Diffusion tensor imaging (variant of MRI)
- Functional MRI
- Positron emission tomography (PET scan)
- Macroelectrode EEG
300
What's the function of a Computerized tomography scan?
Scans structure of living brain
301
What's the function of a Magnetic resonance imaging (MRI)?
Scans structure of living brain
302
What's the function of a Diffusion tensor imaging (variant of MRI)?
Visualizes axon tracts
303
What's the function of a Functional MRI?
Measures brain activity during behaviour
304
What's the function of a positron emission tomography (PET scan)?
Detects radioactive compounds
305
What's the function of a Macroelectrode EEG?
Records activity of a large number of neurons on cortical surface
306
Humans and chimpanzees share how much percent of their DNA?
98.8 percent
307
What's the corpus callosum?
a bundle of nerve fibers that connect the left and right sides of the cerebral cortex
308
What's consciousness?
The state or quality of our awareness...awareness of our thoughts, perceptions, memories and feelings
309
What are proteins made of?
Chains of amino acids
310
What's one big difference between humans and other animals?
It's Neoteny = extended youth
- Human brain development takes much longer than other animals
311
The stronger the stimulus the more ... the action potential
The higher the frequency of the action potential
312
How do myelin sheaths affect the speed of the action potential?
They can make them faster
313
What are the main elements of cells (of life on Earth)?
CHNOPS
- Hydrogen
-Oxygen
- Carbon
- Nitrogen
- Others (phosphorus, sulfur, …)
314
What are the basic molecules of life?
- Water
- Sugar
- Lipid
- Nucleic acid
- Amino acid
315
RNA refers to a strand of a what type of nucleic acid?
Ribonucleic acids
316
The cell membrane is basically a ...
Liposome
317
What are microtubules?
allow for rapid transport of material throughout the neuron
318
What's a gene?
section of DNA that encodes a specific protein
319
Outside the nucleus, ribosomes translate what into proteins?
RNA
320
What's a chromosome?
a strand of compacted DNA
321
What's the genome of a cell?
- The genome of a cell (of an organism) refers to all of its DNA
- The genome provides the information necessary to synthesize all of the cell’s proteins
322
What are protein isoforms?
Different versions of a protein that are made from one gene
323
Most (>99.9%) of the atoms in the universe are what?
Hydrogen or Helium
