The Nervous System Part 3

Question 1

What is a 1000 times thinner than paper and more numerous in you than grains of sand on a beach?

Answer 1

The Synapse. The meeting point between two neurons. The neurons strength and purpose lies in their connections. Synapse comes from the greek for clasp or join.

Question 2

How many neurons does a human brain have?

Answer 2

The human brain has over 100 billion neurons

Question 3

How many synapses does your brain have?

Answer 3

Each neuron has 1,000 to 10,000 synapses so your brain has between 100 and 1000 trillion synapses

Question 4

In simple terms explain a synapse’s role in an action potentials journey

Answer 4

An action potential travels down an axon and hits a synapse that converts it into a different type of signal and flings it over to another neuron

Question 5

What do synapses allow us to do?

Answer 5

Synapses are able to change and adapt in response to neuron firing patterns which allows us to learn and remember

Question 6

What are the two main ways nerve cells communicate?

Answer 6

Electrical - Much more abundant in embryonic nervous tissue where they help guide neural development (The group texts) and Chemical - Used more often than electrical, messages are more controlled and personal

Question 7

How do nerve cells send electrical messages?

Answer 7

Electrical synapses send an ion directly from the cytoplasm of one nerve cell to another through small junctures called gap junctions. This action potential in one neuron creates an action potential in the other cells across the synapse. This message is super fast as it is never converted

Question 8

Where are electrical messages important?

Answer 8

Electrical synapses and messages are important in autonomic functions where it is important for muscles to be triggered in synchrony ie muscle cells of the heart

Question 9

What do nerve cells use to send chemical messages throughout the nervous system?

Answer 9

These messages use neurotransmitters or chemical signals which defuse across a synaptic gap in order to deliver their message

Question 10

What is the main advantage of chemical messages over electrical?

Answer 10

The main advantage chemical synapses have over electrical is they can effectively convert the message in steps from electrical to chemical back to electrical which allows for different ways to control that impulse

Question 11

What can the long term translation of messages in chemical synapses be the result of?

Answer 11

Potentiation, or the strengthening of a synapse through classic conditioning Habituation or when a synapse decreases its response to a common stimulus Sensitisation, when a reaction to one stimulus causes other synapses to be more sensitive to reactions

Question 12

What is the cell sending the action potential referred to as?

Answer 12

The presynaptic neuron

Question 13

What does a neuron transmit an action potential through?

Answer 13

The presynaptic terminal (usually an axon terminal). There terminals are filled with tiny synaptic vesicles (sacks) each filled with 1000s of molecules of a given neurotransmitter

Question 14

What is a cell that receives an action potential referred to as?

Answer 14

The postsynaptic neuron. It accepts the neurotransmitters in its receptor region (usually on the dendrite)

Question 15

Do neurons touch?

Answer 15

Negatory. Neurons do not touch there is a small gap between synapses and receptro regions, this is called the synaptic cleft and it is less than 5 millionths of a cm apart

Question 16

When an action potential races along an axon activating the sodium and potassium channel in a wave, what occurs when it reaches the presynaptic terminal?

Answer 16

When an action potential reaches a presynaptic terminal it activates the voltage-gated calcium channels (Ca²) opening them and releasing calcium ions into the neuron’s cytoplasm

Question 17

What does the flow of positevly charged calcium ions into a neruons cytoplasm cause in a presynaptic terminal?

Answer 17

This flow of positively charged ions causes all the tiny synaptic vesicles to fuse with cell membrane and purge their chemical messengers

Question 18

What do neurotransmitters released from a presynaptic terminal act as?

Answer 18

These neurotransmitters act like couriers defusing across the synaptic cleft and binding to receptor sites on the post synaptic neuron

Question 19

Once a presynaptic neuron has successfully converted an electrical impulse to a chemical message and diffused it across the synaptic cleft utilising neurotransmitters what needs to happen in order for the message to continue traveling throughout the nervous system?

Answer 19

It needs to be converted back to electrical. This conversion back occurs once a neurotransmitter binds to a receptor because thats what causes the ion channels to open

Question 20

What do neurotransmitters tell neurons?

Answer 20

The neurotransmitter tells the neuron what to do. Depending on which particular neurotransmitter binds to which receptro the neuron might either get excited or inhibited

Question 21

What are Excitatory Neurotransmitters?

Answer 21

Excitatory Post-Synaptic Potentials (EPSPs):

Graded potentials that push the neuron closer to threshold and make an action potential more likely to fire

They depolarise the post synaptic neuron by making it’s inside more positive bringing it closer to threshold

Question 22

What are Inhibitory Neurotransmitters?

Answer 22

Inhibitory Post-Synaptic Potentials(IPSPs)

Graded potentials that push the neuron further from the threshold which makes an action potential harder to achieve

They hyperpolarise the postsynaptic neuron making it’s inside more negative

Question 23

What does the likelihood of a postsynaptic neuron developing an action potential depend on?

Answer 23

Any region of a single neuron might have 100s of synapses each with different excitatory or inhibitory neurotransmitters. The likelihood of the postsynaptic neuron developing an action potential depends on the sum of all the excitations and inhibitions in that area

Question 24

How many naturally occurring neurotransmitters do we have?

Answer 24

We have over 100 naturally occurring neurotransmitters

Question 25

What happens to neurotransmitters once they are binded to a receptor?

Answer 25

Neurotransmitters only stay bonded to receptros for a few milliseconds then either degrade or get recycled. Some kinds of neurotransmitters get reabsorbed by the presynaptic neuron in a process called reuptake. Others are broken down by enzymes in the synaptic cleft or sent away by diffusion

Question 26

How do psychoactive drugs work?

Answer 26

Psychoactive drugs excite or inhibit the production of neurotransmitters or mimic neurotransmitters

Question 27

Which 3 neurotransmitters does cocaine target?

Answer 27

Serotonin, Dopamine and Norepinephrine

Question 28

What are the basic properties of serotonin?

Answer 28

Serotonin

Mainly inhibitory - plays role in regulating mood, apetite, circadian rhythm and sleep

Some antidepressants help stabalise mood by stabalising serotonin levels

Question 29

What are the basic properties of dopamine?

Answer 29

Dopamine

Released when you hug a loved one, have great sex or eat a kick ass donut

Influences emotion and attention mostly makes you feel awesome

Question 30

What are the basic properties of norepinephrine?

Answer 30

Norepinephrine

Amps you up by triggering your fight or flight response

Increases heart rate and primes muscles to engage

Under supply depresses normal mood

Question 31

How does cocaine work?

Answer 31

Cocaine blocks the reuptake of neurotransmitters by blocking channels of presynaptic neurons. This allows these powerful chemicals to float around and accumulate

Question 32

What happens to your neurons after using cocaine?

Answer 32

Because you have a limited supply of serotonin, dopamine and norepinephrine, and they take time to replenish, the depletion of chemicals eventually leaves you feeling terrible in a number of ways. Feeling sick, anxious, aggressive, upset, tired and weak etc.

Prolonged use may cause the brain to adapt as all your receptors remember how great those chemicals feel. Over time you start to lose receptors