3. neurons

Question 1

what is a nerve impulse / action potential

Answer 1

begins as a small depolarization which is carried as a wave of depolarization across the membrane of the neuron, in the form of an action potential.
a wave of depolarization, in the form of an action potential, that is propagated along a neuron or chain of neurons as the means of transmitting signals in the nervous system

action potential:
- Is an electrical impulse thats caused by movement of small electrically-charged particles (ions) that move across the cell membrane of a neuron
- the electrical signals carried by axons and transmitted to dendrites
- Happens in the soma/cell body (at the base of the axon)

Question 2

How is a nerve impulse generated? *** where does the action potential occur?

Answer 2

sodium and potassium and something with the pressure maybe??

the action potential happens at the axon
a. Resting potential (polarized -70mV)

b. Depolarization happens when the stimulus is strong enough to reach the threshold (opening Na+ channels)
Inside of the cell is more positive.
Anything below the threshold will not causes an action potential

c. Repolarization Na+ channels starts closing, K+ channels starts opening.

d. Hyperpolarization Return back to the resting potential. K+ channels close slower. The inside of the cell is even more negative.
-> refractory period: no more action potential. Absolute/relative

e. Threshold Minimum voltage required for action potential

Question 3

How is information transported from one neuron to the next neuron?

Answer 3

through synaptic transmission (look at that flashcard)

alsooo thru membrane potential/resting potential:
The membrane potential is the difference in electrical charge between the inside and the outside of the neuron. When a neuron’s membrane potential passes the action potential threshold, it triggers the opening of what are known as voltage-gated sodium channels, which allow positively charged sodium ions to pass into the cell. This causes the cell’s membrane potential to rapidly become more positive, leading to the spike.

Resting Potential
Not sending signals (cell is at rest)
Inside - more negative
Outside - more positive
Difference in electric potential: -70mV
The sodium are closed when the membrane is at rest
The potassium are nearly closed so it can pass through when at rest

Question 4

What are neurotransmitters and what is their role?

Answer 4

Chemicals substances that transmit signals and ensures that the gates open to allow ions to pass through

Types:
Small transmitters
Amino acids - GABA, glutamates
Monoamines - Dopamine, Serotonin, epinephrine, norepinephrine
Acetylcholine
unconventional neurotransmitters
Large transmitters
Neuropeptides: Endorphins
Other
Gasses - nitric oxide
Purines - ATP

Question 5

explain what action potential and resting potential is

Answer 5

action potential is when the message is being fired down the neurons axon and all that good stuff, resting potential is when the cell is at rest, not firing any signals

Question 6

what are the different phases of the action potential

Answer 6

a. Resting potential (polarized -70mV) The resting potential enables the neuron to react fast to stimulation (like the bow and arrow example)
When the neuron is stimulated, the resting potential is disturbed, when the stimulation is strong enough (if the threshold of stimulation is reached) then the sodium channels open
This opening evokes a fast flow of sodium to enter the membrane
The reason why the sodium moves so fast into the neuron is because of the electrostatic pressure and the pressure from concentration gradient

b. Depolarization happens when the stimulus is strong enough to reach the threshold (opening Na+ channels)
This causes the membrane potential to be more positive on the inside of the neuron than on the outside.
Anything below the threshold will not causes an action potential

c. Repolarization Na+ channels starts closing, K+ channels starts opening. At the peak of this sodium ion influx, the sodium ions close while the potassium channels are still open so potassium can go out of the neuron
This makes the membrane repolarized

d. Hyperpolarization Return back to the resting potential. K+ channels close slower. The inside of the cell is even more negative.
-> refractory period: no more action potential. Absolute/relative
Then as more potassium ions continue to leave the neuron, it becomes even hyperpolarized. And then the resting potential is restored.

e. Threshold Minimum voltage required for action potential

Question 7

membrane***

Question 8

ion channels

Answer 8

Electrically-charged particles that cause electrical impulses
Either have a positive or negative charge
2 important positively charged ions that cause the membrane potential
Sodium ions (Na+) -Potassium ion (K+)

Question 9

sodium-potassium pump

Answer 9

The sodium-potassium pump: 3 sodium are sent out, 2 potassium are sent in (active process) -> causes indifference.
Selective permeability
a protein complex in cell membrane.
3 sodium ions out and at the same time 2 potassium into the neuron
This increases the concentration of sodium outside.
Pump works really hard to keep this imbalance which requires a lot of energy.
These pumps close and open depending on the voltage
Why doesnt the sodium rush in the cell: due to selective permeability

Question 10

Electrostatic pressure (electrical gradient)

Answer 10

More sodium outside the neuron than potassium on the inside
We already know the sodium potassium pump has been working hard to maintain this distribution so in this resting potential, the inside of the neuron is negatively charged while outside is positive. “And as u may know, opposites attract to each other” so the positively charged ions from the outside are attracted by the negative charges and want to go into the neuron.
(need to ask if i understood correctly) the outside is naturally a positively charged environment and inside is negatively charged. Ions are drawn to negativity so thats why the positively charged ions wanna go into the neuron? Cuz the inside is negative and theyre both positive so the Na+ wants to go in and the K+ wants to stay in?

Question 11

Pressure from concentration gradient

Answer 11

Pressure is induced by the uneven distribution of ions itself. This creates some pressure on the ions
Analogy: imagine a room with 100 ppl and they’re all crowded in a room. This wouldn’t happen cuz ppl like their personal space and naturally spread out kinda evenly. Same with ions.
In the cell membrane there are protein molecules,
There’s the sodium potassium pump but also, There’s ions that are specialized to let through either sodium ions and potassium ions. (one in the middle is a sodium potassium pump.
During resting stage, sodium channel is closed so no Na+ ions can come in and K+ channels are almost completely closed. So only a tiny bit of potassium ions can pass thru the membrane.

Question 12

Myelin sheaths and nodes of Ranvier and how they play a role in saltatory conduction

Answer 12

Describes a way an electrical impulse goes from node to node
The axon is responsible for making the signal travel fast for a long distance
Myelin sheaths help accomplish this.
Composed of proteins and something else
Increase distance or reach of action potential and how far ahead it can influence the electrostatic pressure in the axon
The domino effect goes way faster because the action potential only has to be generated at the nodes (gaps) between the myelin sheaths.
Nodes of ranvier: between myelin sheaths.
In each node, a new action potential can be generated

Question 13

neurotransmitters: adrenaline

Answer 13

fight or flight

Question 14

neurotransmitters: noradrenaline

Answer 14

concentration

Question 15

neurotransmitters: dopamine

Answer 15

pleasure

Question 16

synapse

Answer 16

Where 2 neurons interact. Gap between
Presynaptic- axon of neuron that sends info and
postsynaptic-Dendrite and cell body that receives the info

Question 17

presynaptic neurons and postsynaptic neurons

Answer 17

Presynaptic Neurons - sends information
Postsynaptic Neurons - receives information

Question 18

receptors and autoreceptors

Answer 18

Where neurotransmitters can bind and its located in the postsynaptic neuron
Lock-key mechanism

Feedback Mechanism & Autoreceptors - Regulates the release of neurotransmitters by sending an signal post synaptic
autoreceptors (pre synaptic neurons) controls the release of the right amount of neurotransmitters

Ionotropic Receptors - when neurotransmitter binds -> opening or closing of the ion channels immediately (ex. GABA and glutamate)

Metabotropic receptors - when neurotransmitter binds -> a small cascade of metabolic reactions in the cell -> receptor releases G protein -> this activates the second messenger system (ex. autoreceptors)

Question 19

reuptake pumps (transporters)

Answer 19

Reuptake of Neurotransmitters - some of the neurotransmitters stays in the synaptic cleft -> reabsorption

Reuptake is the reabsorption of a neurotransmitter by the molecular transporter of a pre-synaptic neuron after it has performed its function of transmitting a neural impulse. This prevents further activity of the neurotransmitter, weakening its effects.
Neurotransmitters move freely in the synapse
The presynaptic membrane reuptakes the dopamine with reuptake pumps
It ensures that not too many neurotransmitters remain in the synapse
There can be multiple receptors (dopamine receptors and opiate receptors that bind to endorphins)
Feedback mechanism: job is to make sure there’s just enough neurotransmitters at the synapse, they regulate it. When the neurotransmitter binds to the autoreceptors, a signal is released that less neurotransmitters should be produced/released.

As an example, serotonin is a neurotransmitter (a chemical messenger). It is produced by nerve cells in the brain and is used by nerves to communicate with one another. A nerve releases the serotonin that it has produced into the space surrounding it. The serotonin either travels across that space and attaches to receptors on the surface of nearby nerves or it attaches to receptors on the surface of the nerve that produced it, to be taken up by the nerve, recycled, and released again. This process is referred to as reuptake. A balance is reached for serotonin between attachment to the nearby nerves and reuptake. A medication that acts as a selective serotonin reuptake inhibitor (SSRI) blocks the reuptake of serotonin and thereby increases the level of serotonin in the brain.

When a neuron’s receptor cells are blocked by neural inhibitors, all of it is forced to be released into the bloodstream, increasing the levels. Popular SSRIs like Zoloft and Prozac do this, causing the serotonin to be collected by the receptor cells and overall increasing the levels of the neurotransmitter.

Question 20

ionotropic vs metabotropic receptors

Answer 20

Ionotropic Receptors - when neurotransmitter binds -> opening or closing of the ion channels immediately (ex. GABA and glutamate)

A metabotropic receptor, also referred to by the broader term G-protein-coupled receptor, [1] is a type of membrane receptor that initiates a number of metabolic steps to modulate cell activity. The nervous system utilizes two types of receptors: metabotropic and ionotropic receptors. While ionotropic receptors form an ion channel pore, metabotropic receptors are indirectly linked with ion channels through signal transduction mechanisms, such as G proteins.

Both receptor types are activated by specific chemical ligands. When an ionotropic receptor is activated, it opens a channel that allows ions such as Na+, K+, or Cl− to flow. In contrast, when a metabotropic receptor is activated, a series of intracellular events are triggered that can also result in ion channels opening or other intracellular events, but involve a range of second messenger chemicals.[2]

in my own words:
Ionotropic receptors
Are ligand activated channels
Similar to io channels
When a neurotransmitter binds to it, it leads to the opening of it.
So the receptor itself is a channel
When ions enter the cell, they change potentials very quick
So these receptors can be used for very fast events like muscle movements and eyesight
Neurotransmitters involved in this transition are glutamate and GABA
metabotropic receptors??

Question 21

EPSPs and IPSPs

Answer 21

EPSP
Excitatory post-synaptic potential
Stimulates the chance of a action potential to occur

IPSP
Inhibitory post-synaptic potential
Less excitable state: inhibits the chance of a action potential

Question 22

what are the 2 ways neurons can send messages thru

Answer 22

Chemicals → between neurons (synaps)
Electricity → within neurons (axon)

Question 23

during resting potential, is it more positive or negative inside?

Answer 23

Inside - more negative
Outside - more positive

Question 24

explain the steps of synaptic transmission

Answer 24

1. within the axon of the neuron are neurotransmitters, which are held in storage-like vesicles until they are released when the neuron is stimulated
2. the small space between the axon terminal and the dendrite of the next axon is called the synapse. an action potential stimulates the release of neurotransmitters across the synapse
3. the neurotransmitter binds itself to the receptor sites on dendrites of the next neuron, causing a change in potential

Question 25

synapse
presynaptic neurons
postsynaptic neurons
exocytosis

Answer 25

Synapse - where the communication between neurons happens
Presynaptic Neurons - sends information
Postsynaptic Neurons - receives information
Exocytosis - the process of releasing neurotransmitters

Question 26

all or nothing response

Answer 26

The impulse is not influenced by the intensity of the stimulation. As long as the stimulation is enough to create the threshold then the action potential will be fired.
Basically there’s no bigger or smaller action potential
Toilet flushing example

Question 27

rate law**

Answer 27

here could be more action potentials but the strength stays the same. There could be higher action potential frequency -> need stronger stimulus

When a neuron is stimulated more strongly, this does not result in a bigger action potential, but the frequency of the action potential rises

Question 28

in a nutshell:
action potential
membrane potential

Answer 28

action potential: Is an electrical impulse thats caused by movement of small electrically-charged particles (ions) that move across the cell membrane of a neuron

Membrane potential: Difference between voltage in inside and outside of the neuron

Question 29

properties of synapses
Reflex arc
Temporal Summation
Spatial Summation
Postsynaptic potential
Graded potential:

Answer 29

Reflex arc - sensory neurons -> motor neurons

Temporal Summation - single stimuli over short period of time

Spatial Summation - multiple stimulus in multiple places at the same time

Postsynaptic potential
Opening of the iron channels and changes the potential of the postsynaptic neuron
Postsynaptic potential can either decrease or increase

Graded potential: when the impulse is not strong enough to active a action potential
The graded potential can either depolarize or hyperpolarize

Question 30

neurotransmitter: serotonin

Answer 30

Serotonin is a neurotransmitter (chemical messenger) produced within the central nervous system (CNS) that contributes to feelings of happiness.
Too little serotonin has shown associations with depressed feelings, sadness, and fatigue. Too much serotonin, however, could result in serotonin syndrome, which could lead to symptoms of restlessness, hallucinations, and confusion.
Serotonin is also known as a hormone within the enteric nervous system of the body, primarily found within the gastrointestinal tract (gut).
In the enteric nervous system, serotonin plays a role in numerous biological processes such as controlling cardiovascular function, bladder control, and bowel movements.
Serotonin in the brain, however, is of interest to psychologists as its role as a neurotransmitter is thought to contribute to many important functions such as playing a role in mood, especially in relation to mood disorders such as depression and anxiety.

Question 31

neurotransmitter: GABA

Answer 31

amma-aminobutyric acid (GABA) a chemical made in the brain. As an inhibitory neurotransmitter, GABA reduces a nerve cell’s ability to send and receive chemical messages throughout the central nervous system. Fluctuating levels of GABA are linked to medical conditions including anxiety, autism, and Parkinson’s disease.

GABA is known for producing a calming effect. It’s thought to play a major role in controlling nerve cell hyperactivity associated with anxiety, stress and fear.

Question 32

neurotransmitter:
acetylcholine

Answer 32

learning
acetylcholine appears to have multiple roles. It is known to play an important role in memory and learning and is in abnormally short supply in the brains of persons with Alzheimer disease.

Question 33

neurotransmitter: glutamate

Answer 33

memory
Glutamate is the most abundant excitatory neurotransmitter in your brain and central nervous system. It’s needed to keep your brain functioning properly. Glutamate plays a major role in shaping learning and memory.

Question 34

neurotransmitter: endorphins

Answer 34

euphoria
Endorphins are released by the hypothalamus and pituitary gland in response to pain or stress, this group of peptide hormones both relieves pain and creates a general feeling of well-being. The name of these hormones comes from the term “endogenous morphine.”

Endorphins may help with some mental disorders like schizophrenia.