chapter 3 : Biological basis of behaviour(1)

Question 1

What is the function of the amygdala?

Answer 1

The amygdala is a crucial control centre for, among other things, the experience of fear. It is important for the regulation of fear.

Question 2

What are the two types of cells in the brain?

Answer 2

The brain consists of two types of cells: neurons and glia.

Question 3

What are neurons?

Answer 3

Neurons are individual cells in the nervous system that receive, integrate, and transmit information.

Question 4

What are glial cells?

Answer 4

Glia are cells found throughout the nervous system and they provide various types of support for neurons.

They are much smaller than neurons.

Question 5

What are the functions of the glial cells?

Answer 5

-Providing nutrition, healing, protection, and physical support for the neurons.

-Some act like cleaners, removing debris from the brain.

-Some act like a miniature Pac Man from a
video game, devouring dead and damaged cells

Question 6

What are the 3 ways in which glia provides protection?

Answer 6

-They produce Cerebrospinal fluid .(CSF) is a colourless fluid surrounding the brain and spinal cord. It has several functions, including serving to cushion the brain during an impact.

-Second, they form the blood–brain
barrier, which prevents foreign material, including some viruses and drugs, from entering the brain.

-Third, they contribute to the immune system of the brain

Question 7

What is a synapse?

Answer 7

A synapse is a junction where information is transmitted from one neuron to the next. It is the connection between an axon to the dendrites of another neuron.

Question 8

What are the 5 common structures of a neuron?

Answer 8

1. Cell Membrane
2. Cell body or Soma
3. Dendrites
4. Axon
5. Axon terminal

Question 9

What is the cell membrane and what is it’s role?

Answer 9

A barrier that separates the inside of the cell from the outside.

This barrier, called the cell membrane, has small channels or gates that allow, or prevent, molecules from
entering or leaving the cell.

Question 10

What is a cell body or soma and what is its function?

Answer 10

1. Cell body, also called a soma, which contains the nucleus and acts like a
   tiny factory where proteins and neurotransmitters.

2.The cell body is where
information from thousands of other cells is gathered and sorted out.

Question 11

What are dendrites and what is it’s function?

Answer 11

1. Dendrites, which gather
   much of the incoming information from other cells.

Dendrites are the structures that branch out from the cell body.

2. Their main purpose is to increase the surface area of the neuron so that chemicals, released from thousands of other cells, can influence the activity of the
   neuron that the dendrites belong to.

Question 12

What is axon and what is its function?

Answer 12

Axon is a long, thin fibre that transmits signals away from the soma to other neurons or to muscles or glands.

The axon’s main role is to conduct a brief electrical charge away from the cell body.

Question 13

What is an axon terminal and what is its function?

Answer 13

1. Though only one axon leaves each cell body, this axon can branch and each branch ends in an axon terminal.

2.Axon terminals are where chemicals
are released by the neuron to influence the activity of other neurons

Question 14

What is a myelin sheath?

Answer 14

In humans, many axons are wrapped in cells with a high concentration of a white, fatty substance called myelin.

The myelin sheath is insulating material, derived from specialized glial cells.

Question 15

What happens if a myselin sheath deteriotes?

Answer 15

If an axon’s myelin sheath deteriorates, its signals may not be transmitted effectively.

The loss of muscle control resulting from multiple sclerosis is due to a degeneration of myelin sheaths.

Question 16

What is the purpose of the myelin sheath?

Answer 16

• Prevents the axon from being accidently activated and also provides some protection to the neuron

1. It speeds up the transmission of signals that move along axons.
2. It is very efficient. Each cell maintains an electric charge across its membrane. Myelinated axons only have to maintain this charge at small gaps in the myelin along the length of the axon.

Question 17

What are neurotransmitters?

Answer 17

They are chemical messengers.

Question 18

The activity of neurons can be understood by examining four process, what are they ?

Answer 18

Resting potential, action potential, synaptic transmission and graded potentials.

Question 19

What is Resting potential?

Answer 19

When the cell is at rest, there is an unequal distribution of some molecules between the outside and inside of the cell.

The resting potential of a neuron is its stable, negative charge when the cell is inactive. This charge is about −70 millivolts.

Question 20

How does the inside of the cell have a larger concentration of negative ions compared to the outside?

Answer 20

Positively charged ions and negatively charged ions flow back and forth across the cell membrane, but they do not cross at the same rate.

The difference in flow rates leads to a slightly higher concentration of negatively charged ions inside the cell.

Question 21

How is the resting potential maintained?

Answer 21

To create and maintain the resting potential, two
ions are critical: potassium (K+) and sodium (Na+).
There are small openings in the cell membrane, called gates or channels, which allow potassium to move more easily in and out of the cell.

There are channels for sodium (Na+) as well, but they are usually closed

Question 22

How is the resting potential created?/ What is the sodium-potassium pump?

Answer 22

To create the resting potential there is an exchange
system that pumps three sodium ions out of the
cell for every two potassium cells it pumps in.

This exchange system is known as the sodium -potassium pump.

Question 23

What is the purpose of the sodium-potassium pump?

Answer 23

It is responsible for keeping more sodium ions
just outside the cell membrane

Because sodium ions are positively charged, the greater concentration of sodium just outside of the cell membrane means that the inside of the cell has a relatively negative charge—this is critical for maintaining the resting potential.

Question 24

Why is the resting potential called the resting potential?

Answer 24

1. First, the resting potential is maintained when the cell is relatively at rest.
2. Second, the uneven distribution of ions represents a potential energy stored in the cell.

Question 25

How important is the resting potential?

Answer 25

Well, half the energy the brain uses is used to create and maintain the resting potential. Without the resting potential, the brain would not allow us to think, feel, learn, or move. This is because the second process, the action potential, requires the resting potential.

Question 26

What is the action potential and what is the process of it?

Answer 26

When a neuron is stimulated by the activity of other
cells there can be a complete, rapid, and brief reversal of the electrical potential across that neuron’s membrane. During this reversal, the inside of the cell may go from its resting potential of 270 millivolts to 130 millivolts.

This reversal in polarity allows for an electric charge to race down the axon. This charge is called the action potential, which is a very brief shift in a neuron’s electrical charge that travels along an
axon.

Question 27

What are the steps of the action potential process?

Answer 27

1. When the cell is sufficiently stimulated, sodium
   channels from a small section of the membrane open.
2. This allows for the sodium ions near this channel,
   which have been built up on the outside of the cell
   membrane, to rush into the cell.
3. This in turn causes the next section of the membrane to open its sodium channels.
4. This process continues so that the opening of the channels allows for the electrical charge to race down the length of the axon until it reaches the end of the axon.

Question 28

What is the “all or none” principle?

Answer 28

Once started, the full action potential completes its journey to the cell’s end, the axon terminals.

This has been referred to as the all-or-none
law because either the cell fires or it does not.There
are, with few exceptions, no partial action potentials.

Question 29

How can we detect degrees of stimulation if the only information the brain receives is an on or off pulse?/How can we perceive differences in intensity of stimulation from a process that only has two levels?

Answer 29

The answer is found in the rate of the action
potentials. Typically, action potentials can occur at
rates of up to 1000 times per second. The greater the
rate, the greater is the intensity of the stimulus.

Question 30

What is the absolute refractory period?

Answer 30

This time, after the sodium channels have opened and the rushing in of the sodium reverses the cell’s polarity, is called the absolute refractory period, which is the minimum length of time after an action potential during which another action potential cannot begin.

Question 31

When does a neuron fire again after the absolute refractory period?

Answer 31

It is not until the sodium channels close and the resting potential is restored that the cell is ready to fire again.

Question 32

What does the speed of the action potential depend on/ limited by?

Answer 32

A limiting factor in the speed of the action potential is the size of the axon.

Axons with a larger diameter have less resistance, so the speed of the action potential can be increased

Question 33

What is the advanatges myelination?

Answer 33

1. There are small gaps in the myelination that leave the axon exposed. the resting potential only needs to be maintained at these gaps. This has the important benefit of saving energy.
2. During an action potential, the rapid reversal of polarity only occurs at these gaps. This allows the
   action potential to “leap frog” down the axon up to
   30 times faster than down an unmyelinated axon