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Brain and Behaviour > The Nervous System: Structure + Intracellular Signal Transmission > Flashcards

The Nervous System: Structure + Intracellular Signal Transmission Flashcards

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1
Q

Why do complex organisms need a nervous system?

A

-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

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2
Q

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

A

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

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3
Q

What are the functions of a neuron?

A

-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)

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4
Q

What is the form + size of a neuron?

A

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

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5
Q

Life span of a neuron?

A
  • develop from neural stem cells
    -when neurogenesis complete dead neurons not replaced
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6
Q

What does neurogenesis mean?

A

generation of neurons

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7
Q

Around what time is neurogenesis complete?

A

around 5 months after conception

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8
Q

What are glia cells?

A

provide a protected environment for neurons to survive

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9
Q

How do glia cells develop?

A

from neural stem cells

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10
Q

Name 3 glia cells

A

Astrocytes
Microglia
Oligodendroglia

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11
Q

What do astrocytes look like and do?

A

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

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12
Q

What do microglia look like and do?

A

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

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13
Q

What do oligodendroglia look like and do?

A

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

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14
Q

Where is the axon hillock?

A

where the axon meets the soma

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15
Q

How do we get a signal in the neuron?

A

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
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16
Q

How does the signal transmission work?

A

electro-chemical gradients

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17
Q

What percentage of dead neurons are there in brain development?

A

20-80%

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18
Q

Why do neurons have internal space filled with fluid?

A

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

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19
Q

How does our body get to resting state?

A
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20
Q

What is resting potential?

A

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.

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21
Q

What role do ion gradients play in resting potential?

A

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

Ion gradients are crucial for the electrical activity of neurons.

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22
Q

What happens if the membrane is non-permeable?

A

Electrical activity remains static

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

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23
Q

What allows ions to enter and leave the neuron?

A

Protein channels in the membrane

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

24
Q

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

A

K+ (potassium)

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

25
Q

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

A
  • Concentration gradient pulls K+ out
  • Electrical gradient pulls K+ in

These opposing forces are crucial for maintaining the resting potential.

26
Q

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

A

The membrane would depolarize, leading to no electrical activity

This would disrupt the neuron’s ability to transmit signals.

27
Q

What is the function of the sodium/potassium pump?

A

It works against the concentration gradients to maintain resting potential

The pump actively transports Na+ out and K+ into the cell, requiring energy.

28
Q

Why do neurons need energy to maintain resting potential?

A

Active channels work against equilibrium

Maintaining resting potential is an active process that consumes ATP.

29
Q

What is the basis of electrical activity in signal transmission?

A

Movement of electrically charged particles (ions)

This includes the movement of both positive and negative ions across the membrane.

30
Q

What are ion specific channels?

A

Gates that can open due to chance or response to stimulation

These channels regulate the flow of specific ions across the cell membrane.

31
Q

What happens when positive ions enter a cell?

A

The membrane depolarises

This change in membrane potential is crucial for initiating action potentials.

32
Q

What happens when negative ions enter a cell?

A

The membrane hyperpolarises

Hyperpolarisation makes the inside of the cell more negative compared to the outside.

33
Q

What is electrotonic transmission?

A

Passive and graded transmission of electrical signals along the membrane

It involves electrochemical gradients that sweep ions along, but signals can decay before reaching the axon hillock.

34
Q

What is the key characteristic of action potentials?

A

Active and not graded transmission of electrical signals

Action potentials maintain the same strength of signal regardless of distance.

35
Q

How do voltage-gated membrane channels work?

A

They open/close in response to electrical changes at the membrane

This mechanism is crucial for the initiation and propagation of action potentials.

36
Q

What is the sequence of events during membrane depolarisation?

A
  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)

This sequence describes the rapid changes in membrane potential that occur during the action potential.

37
Q

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

A

membrane depolarisation or hyperpolarisation

38
Q

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

A

True

39
Q

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

A

Resting potential returns

The axon hillock is the part of the neuron where action potentials are initiated.

40
Q

What occurs when the membrane depolarizes at the axon hillock?

A

NA+ channels open, resulting in action potential

This is the initial step in generating an action potential.

41
Q

What must happen for an action potential to occur?

A

Enough + ions must arrive to reach threshold

The threshold is the critical level of depolarization needed to trigger an action potential.

42
Q

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

A

The inside of the cell becomes positive

This influx of sodium ions is crucial for the depolarization phase of the action potential.

43
Q

What occurs after complete depolarization in the action potential process?

A

Closing of NA+ channels and opening of K+ channels

This transition helps restore the resting membrane potential.

44
Q

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

A

When resting potential is restored

This typically occurs after the cell has hyperpolarized.

45
Q

Where does the action potential originate?

A

At the axon hillock

This is the site where the decision to fire an action potential is made.

46
Q

How does the action potential travel down the axon?

A

Each burst of depolarization acts as a trigger for adjacent sections

This sequential opening of sodium channels propagates the action potential.

47
Q

Why does the action potential not travel backwards?

A

During hyperpolarization, the membrane is difficult to depolarize

The refractory period ensures unidirectional propagation of the action potential.

48
Q

What are the properties of an action potential?

A
  • No decay
  • Either generated or not
  • Minimal time between subsequent action potentials
  • Speed of 1-10m/s

These properties ensure reliable and efficient signal transmission in neurons.

49
Q

What is saltatory conduction?

A

The jumping of action potentials from node to node in myelinated axons

This process greatly increases the speed of conduction in sensory and motor neurons.

50
Q

What does myelination do to axons?

A

Insulates the axon, preventing ion inflow and outflow

Myelination is essential for efficient nerve signal transmission.

51
Q

What are nodes of Ranvier?

A

Gaps in myelination where action potentials are generated

These nodes facilitate the rapid propagation of action potentials along myelinated axons.

52
Q

How does the nervous system code information qualitatively?

A

By location

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

53
Q

How does the nervous system code information quantitatively?

A

By the strength of a stimulus

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

54
Q

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

A

Increases the likelihood of sending out action potentials (APs)

A stronger stimulus can lead to a higher frequency of action potentials in response.

55
Q

Can microglia swim through the brain?

A

Yes

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