The Nervous System: Structure + Intracellular Signal Transmission

Question 1

Why do complex organisms need a nervous system?

Answer 1

-cells inside body are not in direct contact with outside world
-cells live in different environments + are specialised so they need to be co ordinated to function

Question 2

How do communication systems help cells function in a co ordinated way?

Answer 2

-keep cell activity constant and adjusts activity when needed
-signals from one group or group of cells change properties of receiving cell

Question 3

What are the functions of a neuron?

Answer 3

-generation + transmission of elec impulses that reach specific targets
-modify activity and allows selective control of specific target structures
-elec activity modulated by integrated input from other cells (structured communication)

Question 4

What is the form + size of a neuron?

Answer 4

-vague pyramid shape that has long extensions coming from soma
-cant store energy (glucose + 02 needs to be supplied)

Question 5

Life span of a neuron?

Answer 5

• develop from neural stem cells
  -when neurogenesis complete dead neurons not replaced

Question 6

What does neurogenesis mean?

Answer 6

generation of neurons

Question 7

Around what time is neurogenesis complete?

Answer 7

around 5 months after conception

Question 8

What are glia cells?

Answer 8

provide a protected environment for neurons to survive

Question 9

How do glia cells develop?

Answer 9

from neural stem cells

Question 10

Name 3 glia cells

Answer 10

Astrocytes
Microglia
Oligodendroglia

Question 11

What do astrocytes look like and do?

Answer 11

they are star shaped
-transport nutrients from blood vessels to neurons
-waste products taken away from neurons and hold neurons in place

Question 12

What do microglia look like and do?

Answer 12

they are small and are the mobile for defensive function
- produce chemicals that aid repair of damaged neurons and digest dead neurons (phagocytosis)

Question 13

What do oligodendroglia look like and do?

Answer 13

they are large flat branches wrapping around axons
-they contain myelin sheath

Question 14

Where is the axon hillock?

Answer 14

where the axon meets the soma

Question 15

How do we get a signal in the neuron?

Answer 15

in the axon there is internal space filled with chemical fluid surrounded by a thin membrane (this has holes that have gates where signal transmission occurs)
- if gate in dendrite opens and its - inside the cell, + ions will move in
-go down axon hillock and adjacent part will burst open and suck in + charge and get rid of other part in membrane

• this will release chemicals at axon terminals

Question 16

How does the signal transmission work?

Answer 16

electro-chemical gradients

Question 17

What percentage of dead neurons are there in brain development?

Answer 17

20-80%

Question 18

Why do neurons have internal space filled with fluid?

Answer 18

neurons are not empty and do not exist in a vaccum (they are a thick chemical soup of electrically charged particles)

Question 19

How does our body get to resting state?

Question 20

What is resting potential?

Answer 20

The difference in ion concentrations between the inside and outside of a cell at rest

Resting potential is essential for the generation of action potentials in neurons.

Question 21

What role do ion gradients play in resting potential?

Answer 21

They create a difference in concentration of ions across the cell membrane

Ion gradients are crucial for the electrical activity of neurons.

Question 22

What happens if the membrane is non-permeable?

Answer 22

Electrical activity remains static

A non-permeable membrane prevents any ion movement, maintaining the resting state.

Question 23

What allows ions to enter and leave the neuron?

Answer 23

Protein channels in the membrane

These channels are specific to certain ions, regulating their movement.

Question 24

What is an example of an ion that has a concentration gradient affecting resting potential?

Answer 24

K+ (potassium)

The concentration of K+ is higher inside the cell compared to outside.

Question 25

What forces act on K+ ions in the resting potential?

Answer 25

* Concentration gradient pulls K+ out * Electrical gradient pulls K+ in ## Footnote These opposing forces are crucial for maintaining the resting potential.

Question 26

What would happen if the channels in the membrane acted as holes?

Answer 26

The membrane would depolarize, leading to no electrical activity ## Footnote This would disrupt the neuron's ability to transmit signals.

Question 27

What is the function of the sodium/potassium pump?

Answer 27

It works against the concentration gradients to maintain resting potential ## Footnote The pump actively transports Na+ out and K+ into the cell, requiring energy.

Question 28

Why do neurons need energy to maintain resting potential?

Answer 28

Active channels work against equilibrium ## Footnote Maintaining resting potential is an active process that consumes ATP.

Question 29

What is the basis of electrical activity in signal transmission?

Answer 29

Movement of electrically charged particles (ions) ## Footnote This includes the movement of both positive and negative ions across the membrane.

Question 30

What are ion specific channels?

Answer 30

Gates that can open due to chance or response to stimulation ## Footnote These channels regulate the flow of specific ions across the cell membrane.

Question 31

What happens when positive ions enter a cell?

Answer 31

The membrane depolarises ## Footnote This change in membrane potential is crucial for initiating action potentials.

Question 32

What happens when negative ions enter a cell?

Answer 32

The membrane hyperpolarises ## Footnote Hyperpolarisation makes the inside of the cell more negative compared to the outside.

Question 33

What is electrotonic transmission?

Answer 33

Passive and graded transmission of electrical signals along the membrane ## Footnote It involves electrochemical gradients that sweep ions along, but signals can decay before reaching the axon hillock.

Question 34

What is the key characteristic of action potentials?

Answer 34

Active and not graded transmission of electrical signals ## Footnote Action potentials maintain the same strength of signal regardless of distance.

Question 35

How do voltage-gated membrane channels work?

Answer 35

They open/close in response to electrical changes at the membrane ## Footnote This mechanism is crucial for the initiation and propagation of action potentials.

Question 36

What is the sequence of events during membrane depolarisation?

Answer 36

1. Membrane depolarises 2. Some NA+ channels open 3. NA+ ions enter cell 4. Membrane depolarises, depending on threshold 5. All nearby NA+ channels open 6. Membrane is depolarised (more positive inside than outside) ## Footnote This sequence describes the rapid changes in membrane potential that occur during the action potential.

Question 37

Fill in the blank: The movement of ions across the membrane can lead to _______.

Answer 37

membrane depolarisation or hyperpolarisation

Question 38

True or False: Electrotonic transmission is graded and can decay before reaching the axon hillock.

Answer 38

True

Question 39

What happens to the membrane potential at the axon hillock if it remains below threshold?

Answer 39

Resting potential returns ## Footnote The axon hillock is the part of the neuron where action potentials are initiated.

Question 40

What occurs when the membrane depolarizes at the axon hillock?

Answer 40

NA+ channels open, resulting in action potential ## Footnote This is the initial step in generating an action potential.

Question 41

What must happen for an action potential to occur?

Answer 41

Enough + ions must arrive to reach threshold ## Footnote The threshold is the critical level of depolarization needed to trigger an action potential.

Question 42

What happens to the cell when NA+ enters during depolarization?

Answer 42

The inside of the cell becomes positive ## Footnote This influx of sodium ions is crucial for the depolarization phase of the action potential.

Question 43

What occurs after complete depolarization in the action potential process?

Answer 43

Closing of NA+ channels and opening of K+ channels ## Footnote This transition helps restore the resting membrane potential.

Question 44

When do K+ channels close during the action potential process?

Answer 44

When resting potential is restored ## Footnote This typically occurs after the cell has hyperpolarized.

Question 45

Where does the action potential originate?

Answer 45

At the axon hillock ## Footnote This is the site where the decision to fire an action potential is made.

Question 46

How does the action potential travel down the axon?

Answer 46

Each burst of depolarization acts as a trigger for adjacent sections ## Footnote This sequential opening of sodium channels propagates the action potential.

Question 47

Why does the action potential not travel backwards?

Answer 47

During hyperpolarization, the membrane is difficult to depolarize ## Footnote The refractory period ensures unidirectional propagation of the action potential.

Question 48

What are the properties of an action potential?

Answer 48

* No decay * Either generated or not * Minimal time between subsequent action potentials * Speed of 1-10m/s ## Footnote These properties ensure reliable and efficient signal transmission in neurons.

Question 49

What is saltatory conduction?

Answer 49

The jumping of action potentials from node to node in myelinated axons ## Footnote This process greatly increases the speed of conduction in sensory and motor neurons.

Question 50

What does myelination do to axons?

Answer 50

Insulates the axon, preventing ion inflow and outflow ## Footnote Myelination is essential for efficient nerve signal transmission.

Question 51

What are nodes of Ranvier?

Answer 51

Gaps in myelination where action potentials are generated ## Footnote These nodes facilitate the rapid propagation of action potentials along myelinated axons.

Question 52

How does the nervous system code information qualitatively?

Answer 52

By location ## Footnote Qualitative coding refers to how different types of information are represented based on where they originate in the nervous system.

Question 53

How does the nervous system code information quantitatively?

Answer 53

By the strength of a stimulus ## Footnote Quantitative coding involves measuring the intensity of a stimulus and how it affects neuronal responses.

Question 54

What effect does a strong input have on a neuron's firing rate?

Answer 54

Increases the likelihood of sending out action potentials (APs) ## Footnote A stronger stimulus can lead to a higher frequency of action potentials in response.

Question 55

Can microglia swim through the brain?

Answer 55

Yes