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BIO 202 Alara > Lecture 7: Electrical Signalling > Flashcards

Lecture 7: Electrical Signalling Flashcards

1
Q

Who are the first people to suggest that neurons work like circuits?

A

Hodgin and Huxley

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2
Q

What did Hodgin and Huxley study?

A

They studied a squid because it has one of the longest neurons.

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3
Q

What is the most basic unit of the nervous system?

A

The neuron

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4
Q

What are neurons able to do?

A
  1. Nerves carry signals from our sensory organs and others to the Central Nervous System (CNS)
  2. Nerves carry signals from the CNS to muscles and other organs
  3. Nerves transmit and process signals within the central nervous system
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5
Q

Anatomy of a Neuron and its parts

A
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6
Q

Define Dendrite

A

Dendrites are projections from the cell body, or soma, of neurons, the cells of the nervous system.

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7
Q

Dendrite function?

A

Receive electrical signals from other neurons, called pre-synaptic neurons, in the form of neurotransmitters.

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8
Q

Cell Body (Soma) function?

A

The cell body is the core section of the neuron.

The cell body contains genetic information, maintains the neuron’s structure, and provides energy to drive activities. Like other cell bodies, a neuron’s soma contains a nucleus and specialized organelles.

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9
Q

What is an axon and what is its function?

A

This is portion of a nerve cell (neuron) that carries nerve impulses away from the cell body.

Signals travel through this from the cell body to terminals - transmits electrical signals to neurons, muscles, glands.

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10
Q

What is a Myelin Sheath?

A

The myelin sheath is a protective membrane that wraps around part of certain nerve cells.

Speeds up nerve impulse transmission.

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11
Q

What are Myelins made of?

A

Fats and proteins - so they are excellent insulators!

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12
Q

What is a Node of Ranvier?

A

Nodes of Ranvier are gaps in the myelin sheath coating on the neural axon. The myelin allows the electrical impulse to move quickly down the axon. The nodes of Ranvier allow for ions to diffuse in and out of the neuron, propagating the electrical signal down the axon. In other words, their function is to speed up propagation of action potentials along the axon via saltatory conduction. As the electrical signal or impulse travels along the axon, it jumps from one node to the next.

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13
Q

Internode

A

Each section of myelin is called an internode.

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14
Q

What is each gap in the myelin sheath called?

A

Nodes of Ranvier

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15
Q

What is an axon terminal?

A

Axon terminals are the ends of axons which transmit messages to other cells via use of neurotransmitters at synapses.

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16
Q

What is the function of an axon terminal?

A

Functionally, the axon terminal converts an electrical signal into a chemical signal. When an action potential arrives at an axon terminal (A), the neurotransmitter is released and diffuses across the synaptic cleft.

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17
Q

What is neurogenesis?

A

Birth of new neurons, continues into adulthood.

New neurons play an important role in learning.

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18
Q

Name the four types of Neuroglial Cells in the CNS

A
  1. Ependymal cells
  2. Microglial cells
  3. Astrocytes
  4. Oligodendrocytes
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19
Q

Neurons vs Neuroglial Cells

A

The nervous system consists of neurons and glial cells. Neurons generate and propagate electrical and chemical signals, whereas glia function mainly to modulate neuron function and signaling.

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20
Q

What is the function of Ependymal Cells?

A

A glial cell in the CNS. Ependymal cells are important cells that line the fluid-filled spaces in the brain and acts as a key barrier between the cerebrospinal fluid and the underlying brain tissue.

Their primary function is to regulate what flows in and out of the brain to maintain overall brain health.

Assists in producing, circulating and monitoring cerebrospinal fluid (CSF)

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21
Q

Name the two types of Neuroglial Cells in the Peripheral Nervous System

A
  1. Schwann Cells
  2. Satellite Cells
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22
Q

True or False: Ependymal cells are connected to the cell body

A

False, they are connected to the dendrites

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23
Q

What is the function of Microglial Cells

A

A glial cell in the CNS. Mobile phagocytic cells that remove celullar debris, waste products and pathogens.

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24
Q

True or False: Glial cells send signals

A

False, glial cells do not send signals but helps support and maintaining neurons and CSF health

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25
What is the function of Astrocytes?
-Glial cell in the CNS -Maintains the blood-brain barrier by keeping away the blood from interacting with neurons (isolates the CNS) -Structural support -Regulate ion, nutrient and gas concentration in interstitial fluid around neurons -Absorb/recycle neurotransmitters -Form scar tissue after injuries
26
What is the function of Oligodendrocytes?
-Glial cell in the CNS -Responsible for stabilizing the axon -Produce myelin
27
What is the function of Schwann Cells?
-Glial cells in the PNS -Participate in axon repair -Wraps the axon and produces myelin for the myelin sheath production
28
What is the equivalent of Schwann Cells (PNS) in the CNS?
Oligodendroctyes
29
What is the function of Satellite Cells?
Regulate environment around neurons
30
What is the equivalent of Satellite Cells (PNS) in the CNS?
Astrocytes
31
Anaxonic Neuron
- Doesn't have any dendrites or projections -Mostly found in the CNS -Doesn't need to send signals far, that's why it doesn't have projections
32
Unipolar Neuron
-Has one extension from the cell body - Insects have this, but we humans don’t have these neurons - The cell body acts as the dendrite, and there is a terminal
33
Bipolar Neuron
- Two projections - Information is received one way and passed down another way
34
Multipolar Neuron
- a most common type of neuron - Has more than two dendrites - Has one axon - Therefore it can receive information from multiple things but only deliver through one axon - Big neurons, such as motor neurons
35
Pseudounipolar Neuron
has a dendrite on one end and a terminal on the other
36
What is Equilibrium Potential
-The cell has a hydrophobic membrane - The membrane is impermeable to charged ions - Has channels that are permeable to certain ions
37
Neuroglial Cells in the CNS Anatomy
38
Inside the cell
-Negatively charged proteins -Mostly K+ and less Na+
39
Potassium (K+) has a tendency to _____ cells
LEAVE
40
Sodium (Na+) has a tendency to ______ cells
ENTER
41
Outside the cell
Mostly Na+ and less K+
42
On the membrane
Leaky channels (more K+ leaky channels than Na+ leaky channels) Na-K pump
43
Voltage inside of the membrane at rest is
-70 mV
44
Define membrane potential
The difference in total charge between the inside and outside of the cell is called the membrane potential
45
Depolarization
Membrane potential becomes more positive (interior is more positive)
46
Hyperpolarization
Membrane potential becomes more negative (interior is more negative)
47
Repolarization
Membrane voltage returns to resting state - can go either positive or negative
48
Define Graded Potential
Graded potentials are changes in membrane potential that vary according to the size of the stimulus, as opposed to being all-or-none.
49
True or False: Change in membrane potential is proportional to the stimulus applied
True Less Neurotransmitters - less ion channels open - smaller magnitude of graded potential More Neurotransmitters - more ion channels open - larger magnitude of a graded potential
50
Define Axon Hillock
The axon hillock is the region of a neuron that controls the initiation of an electrical impulse based on the inputs from other neurons or the environment.
51
What does the net change in postsynaptic membrane voltage determine?
Net change in the postsynaptic membrane voltage determines whether the postsynaptic cell has reached the threshold required for an action potential
52
What is synaptic summation?
A single neuron can receive both excitatory and inhibitory inputs from multiple neurons. All these inputs are added together at the axon hillock. If the EPSPs are strong enough to overcome the IPSPs and reach the threshold of excitation, the neuron will fire.
53
Why is synaptic summation and threshold important?
Act as a filter so that random "noise" in the system is not transmitted as important information
54
Integration of information
-Single neuron may receive information from thousands of synapses -Axon hillock integrates all stimuli, determines rate of action potential generation at initial segment
55
Where is an action potential generated?
the Axon Hillock
56
Remember
During the rising phase sodium enters the cell and during the falling phase potassium leaves the cells
57
Action potential generation step by step
58
Why doesn't action potential travel in both directions?
- Current is going through both slides - However, action potential only travels in one direction - This is because only certain sodium channels are activated - This means that it can only go one way as the other way has inactive sodium channels
59
Why is myelination so important?
-Insulate action and make sure the signal is not lost by leaking out -Faster propagation of the action potential
60
Voltage gated channels occur only at ...
the gaps of the myelin sheath called Nodes of Ranvier
61
Depolarization occurs only at....
the nodes causing the Action Potential to jump from node to node along the axon
62
Define the synapse
The synapse is the place where information is transmitted from one neuron to another
63
Where do synapses form?
Between axon terminals and dendritic spines There are also axon to axon, dendrite to dendrite and axon to cell body synapses
64
Name the two types of synapses
1. Electrical 2.Chemical
65
Define Electrical Synapses
Direct flow of electrical current from one cell to the next through gap junctions
66
Define Chemical Synapses
Secrete neurotransmitter molecules that activate receptors
67
True or False: Chemical synapses are faster than electrical synapses
False, chemical synapses are slower than electrical synapses as there are many points of intervention
68
How do electrical synapses work?
The presynaptic and postsynaptic membranes are very close together and are actually physically connected by channel proteins forming gap junctions
69
What is the importance of gap junctions?
Gap junctions allow current to pass directly from one cell to the next In addition to the ions that carry this current, other molecules such as ATP can diffuse through the large gap junction pores.
70
Describe some characteristics of electrical synapses
-There is no delay in transmission -The signalling is bidirectional -More reliable as they are less likely to be blocked
71
What is the synaptic cleft?
The synaptic cleft, also known as the synaptic gap, is the space in between the axon of one neuron and the dendrites of another and is where the electrical signal is translated to a chemical signal that can be perceived by the next neuron.
72
Define neurotransmitters
A chemical compound released by a neuron at a synapse and affects the transmembrane potential of another cell
73
Chemical Synapses Chart
74
Define neuromodulators
A chemical compound, released by a neuron, that adjusts the sensitivities of another neuron to specific neurotransmitters
75
Is the outside of the membrane hydrophobic or hydrophilic?
Hydrophilic, the inside tails are hydrophobic
76
Why does hyperpolarization occur?
Repolarization is caused by the closing of sodium ion channels and the opening of potassium ion channels. Hyperpolarization occurs due to an excess of open potassium channels and potassium efflux from the cell. There are more K channels than Na channels
77
How does an action potential start?
When neurotransmitters bind to the receptors on the dendrites of a neuron!
78
Refractory Period Physiology
In its wake, the action potential leaves the Na+ channels inactivated and K+ channels activated for a brief time. These transitory changes make it harder for the axon to produce subsequent action potentials during this interval, which is called the refractory period.
79
Absolute Refractory Period vs Hyperpolarization
absolute refractory period: The period from the opening of the sodium channels until the sodium channels begin to reset. hyperpolarization: A phase where some potassium channels remain open and sodium channels reset.
80

BIO 202 Alara (2 decks)

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