Chapter 2: Nerve Cells and Nerve Impulses

Question 1

main structures of neurons

Answer 1

-neurons receive and transmit information
-shape varies a lot between neurons
-structures similar to animal cell
Membrane
Nucleus
Mitochondria
Ribosomes
Endoplasmic Reticulum

Question 2

structural differences among neurons

Answer 2

Efferent=exit
Afferent=admit
Interneuron=all cell dendrites and axon are completely contained within a single structure
-vary in shape, size, and function
*be able to draw motor and sensory neuron

Question 3

types of glia

Answer 3

Astrocytes 
Microglia 
Oligodendrocytes 
Schwann Cells 
Radial Glia

Question 4

Astrocytes

Answer 4

• wrap around presynaptic terminal,
• takes up ions released by axons and then releases them back to axon to help with synchronicity,
• remove waste from dead neurons
• control blood flow

Question 5

Microglia

Answer 5

• very small
• remove waste
• virus
• fungi
• other microorganisms

Question 6

Oligodendrocytes

Answer 6

• in brain

- build myelin sheath

Question 7

Schwann Cells

Answer 7

• periphery

- build myelin sheath

Question 8

Radial Glia

Answer 8

• guide migration of neurons, axons, and dendrites during embryonic development
• post development they turn into neurons, small # turn into astrocytes and oligodendrocytes

Question 9

advantages of the blood-brain barrier

Answer 9

• does not let a lot of chemicals across because neurons are not easily replaced if destroyed
• essential to health

Question 10

disadvantages of the blood-brain barrier

Answer 10

• some viruses can get through and stay with you for the rest of your life
• keeps out some good chemicals
• keeps out many medications

Question 11

why the neuron uses considerable energy to produce a resting potential

Answer 11

uses lots of energy to produce resting potential so the neuron responds rapidly and is ready when needed

Question 12

competing forces of the electrical and concentration gradients on potassium ions and how this competition produces the resting potential

Answer 12

Selectively permeable membrane:
-ve charge on inside creates electrical gradient
ie- opposites attract therefore +ve ions on outside (K+) are pulled in
Na+/K+ pump - active transport= more Na+ on inside and more K+ on outside
Concentration gradient- less K+ on inside more on outside therefore K+ pulled in
-K+ ions slowly leak back out into cell when pumped out
-Na+ stays out when pumped out due to concentration gradient

Question 13

function of the action potential

Answer 13

fires when reaches specific threshold to send messages

Question 14

molecular basis of the action potential

Answer 14

resting potential= -ve on inside, more Na+ outside, more K+ inside
depolarization=becomes more +ve inside neuron
reaches threshold=voltage gate channels open and Na+ floods inside of neuron
Peak of action potential=voltage gate Na+ channels close (reversed polarity)
-K+ voltage gate channels always open allowing for slow leakage

Question 15

how an action potential is conducted down an axon

Answer 15

ALL OR NONE- cannot increase strength of action potential, can only increase speed
MOTOR NEURON- starts at axon hillock
+ve ions flow within axon to neighbouring regions and depolarize next area of membrane
-action potential starts next action potential a bit further down the membrane

Question 16

how myelin sheaths contribute to this process

Answer 16

• layer of fat around neuron that speeds transmission
• action potential jumps from node of Ranvier to node of Ranvier
• saltatory conduction
• action potential at node triggers flow of current to next node where membrane regenerates the action potential
• thinner=slower (smaller diameter)
• thicker=faster (larger diameter)

Question 17

how local interneurons transmit information without benefit of action potentials

Answer 17

• no axon therefore do not follow all or none law
• graded potential=membrane potential varies in size in proportion to intensity of stimulus
• spreads in all directions to adjacent cells and decays as it travels