Chapter 3

Question 1

How much does the brain weight?

Answer 1

3 pounds

Question 2

Neurons

Answer 2

‘Nerve cells’ that arrange in a network, that send and receive electrical signals in the brain.

Question 3

How many neurons can be found in the average human brain?

Answer 3

Approximately 85 billion to 100 billion.

Question 4

How many interconnections, and how many connections per neuron are in the brain?

Answer 4

Approximately one quadrillion interconnections, and 10,000 connections per neuron.

Question 5

Glial Cells

Answer 5

Cells that take care of the neurons by providing nutrients, oxygen, support, and destroying/removing dead neurons (cleaning up, also absorbs toxins and waste). Known as ‘nurse cells’.

Question 6

How many glial cells can be found in the human brain?

Answer 6

Approximately 1 trillion.

Question 7

What are the three main types of neuron?

Answer 7

Sensory, Association/Inter-neuron, Motor.

Question 8

Explain what a sensory neuron does.

Answer 8

Detects stimuli from external factors (heat, a punch in the face??? being stabbed????), as well as internal feelings in our body (high sodium content in blood means you a thirsty bitch, and pressure in the bladder means ya weewee gotta peepee).

Question 9

Explain what an association/inter-neuron does.

Answer 9

Collects all the information from the sensory neurons and convert it into one message. Imagine sensory neurons each giving inter-neurons a piece of a puzzle and the inter-neurons work to form the whole picture with the puzzle pieces and give it to the motor neurons to put up.

Question 10

Explain what a motor neuron does.

Answer 10

Motor neurons send the signal to the muscles to move, or the glands to secrete hormones into the body. Basically, tells the non-neurons what the fuck to do.

Question 11

What are the three main components of a neuron?

Answer 11

Dendrites, Cell Body, Axon.

Question 12

What does the dendrites do?

Answer 12

Receives messages from the other neurons.

Question 13

What does the cell body do?

Answer 13

Combines, and processes all incoming signals from the dendrites (or sometimes directly). The cell body also contains vital cell structures such as the nucleus which carries DNA, determining the cell function. Furthermore, it contains cellular metabolism to keep the cell alive.

Question 14

What does the axon do?

Answer 14

Sends out signals to the next dendrite (other neurons), to muscles, or glands.

Question 15

How do ions move through cell membranes during resting potential?

Answer 15

The sodium-potassium pump found in the cell membrane pushes 3 Na+ ions out of the cell membrane, while only pulling in 2 K+ ions at a time.

Question 16

What are the charges around the cell membrane during resting potential?

Answer 16

The outside is positive due to the 3 Na+ ions, while the inside is negative since only 2 K+ ions replace them. Tip: The sun is nature’s Prozac! Outside is happier, so more positive!

Question 17

Resting Potential

Answer 17

Refers to when a neuron has a built up charge and it is ready to fire. Difference is -70mV

Question 18

Polarization

Answer 18

When the charge on one side of the neuron is different than on the other, the neuron is said to be polarized. Resting potential difference is -70mV.

Question 19

Depolarization

Answer 19

Occurs during the passage of an action potential along the axon when the nerve is transmitting an impulse. Difference goes from -70mV to +40mV, as the Na+ ions begin to enter the cell membrane while the potassium channels are still closed (this takes less than 1 ms).

Question 20

‘Propogated’ Response

Answer 20

The signal travels down the axon without decreasing in size. This means that depolarization occurs in a pulse-like manner.

Question 21

Hyper-polarization

Answer 21

Occurs when depolarization tries to move back to polarization, though because only 2 K+ ions enter with 3 Na+ ions, the outside become extra positive, while the inside becomes extra negative, creating hyper-polarization, since polarization is ‘regularly’ negative.

Question 22

Refractory Period

Answer 22

The period of time after a neuron has fired during which it cannot fire again (lasts approximately 1 to 2 ms). It is during hyper-polarization that it is hard for a neuron to fire again.

Question 23

What happens before action potential?(threshold)

Answer 23

Right before action potential begins, sodium channels open up and raise the membrane potential to -50mV.

Question 24

Myelin Sheath

Answer 24

A fatty layer of insulation surrounding an axon, making the signals send faster. (skipping stones). Not all neurons have myelin sheath!

Question 25

Nodes of Ranvier

Answer 25

The gaps between the ‘beads’ of the myelin sheath.

Question 26

Saltatory Conduction

Answer 26

When the signal leaps from node to node on the myelin sheath.

Question 27

Neurotransmitters

Answer 27

Chemical substances that help neurons communicate with each other.

Question 28

What is the name of the disease where the immune system attacks the myelin sheath?

Answer 28

Multiple sclerosis.