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Biological Psychology 402 > Chapter 2 Nerve cells and Nerve Impulses > Flashcards

Chapter 2 Nerve cells and Nerve Impulses Flashcards

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1
Q

What did Ramon y Cajal demonstrate? 2.1

A

Anatomical researcher and illustrator detailed drawings of the nervous system

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2
Q

List the major structures of animals cells and give the main function of each. 2.1

A

Plasma membrane-separates inside cell from outside environment
Nucleus: contains chromosomes
Mitochondria: performs meatbolic activity
Ribosomes- protein synthesis
Endoplasmic reticulin: transports newly synthesized proteins.

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3
Q

What are the functional and structural differences between motor and sensory neurons? 2.1

A

Notor neuron- has its soma in the spinal cord
Receives excitation from other neurons through its dendrites and conducts impulses along its axon to muscles
Sensory neuron- specialized at one end to be highly sensitve to light/sound/ touch

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4
Q

What are the main subdivisions of the neuron and the function of each? 2.1

A

Dendrites: receives info
Soma-cell body
Axon-delivers information
Presynaptic terminals-

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5
Q

List several anatomical distinctions between dendrites and axons 2.1

A

Dendrite branches are like trees and contains synaptic receptors
Axon-thin fibre of constant diameter in most cases longer than dendrites (information sender).

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6
Q

What is the myelin sheath? 2.1

A

Insulating material that covers axons in many vertebrates.
Interruptions in the myelin sheath are called nodes of Ranvier.
Invertebrate axons do not have myelin sheaths.

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7
Q

What is the function of the presynaptic terminal or end bulb? 2.1

A

Point at which axon releases chemicals that cross through the junction between one neuron and the next

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8
Q

Describe the structural and functional differences among sensory, motor, and local neurons. 2.1

A

2.1
Motor neuron- has its soma in the spinal cord. It receives excitation from other neurons through its dendrites and conducts impulses along its axon to a muscle
Sensory Neuron- is specialized at one end to be highly sensitive to a particular type of stimulation such as light, sound or touch.
Local neurons- small neurons that do not have an axon. These do not follow the all or none law. These have graded potential
2.1

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9
Q

What do the terms afferent and efferent mean? Can an axon be both afferent and efferent? Explain. 2.1

A

Afferent-brings info into a structure
Efferent-carries info away from a structure
Yes in any giving neuron is efferent from one structure and afferent to another neuron.

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10
Q

What in an intrinsic neuron? 2.1

A

If a cells dendrites and axon are entirely contained within a single structure

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11
Q

How do glia cells differ from neurons? 2.1

A

Other major components of the nervous system do not transmit info over long distances and neurons do although they perform many other fucntions.

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12
Q

What are four functions of glia? 2.1

A

Astrocyte (type of glia) helps synchronize activity of axon-enabling the to send messages in waves
Remove waste material when neurons die and control amount of blood flow to each brain area.
Microglia- removes waste as well as viruses fungi etc
Oligodendrocytes: build myelin sheath
Radial glia-guide migration of neurons during embroyonic development.

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13
Q

Whar are two functions of astrocytes? 2.1

A

Helps synchronize the activity of the axons enabling them to send messages in waves
Also removes waste material created when neurons die and control the amount of blood flow to each brain area.

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14
Q

What two kinds of glia for myelin sheaths?2.1

A 
Oligodendrocyte (in the brain and spinal cord)
Schwann cells (periphery of body)
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15
Q

What is the function of radial glia? What related function do Schwann cells perform? 2.1

A

-guide the migration of neurons and thir axons and dendrites during embroyonic development
When embroyonic development finishes radial glia differentiate into neurons (few astrocytes and oligodentrocytes)

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16
Q

Why do we need a blood-brain barrier? Why don’t we have a similar barrier around other body organs? 2.1

A

Neurons do not regenerate and it needs to be protected from viruses etc.

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17
Q

What happens if a virus does enter the nervous system? 2.1

A

Probaby remains in system for life- remains dormant eg chicken pox => shingles

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18
Q

Describe the arrangement of the endothelial cells that form the blood-brain barrier. 2.1

A

Endothelial cells that form the walls of the capillaries are joined so tightly that nothing can pass through.

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19
Q

What types of chemcals can cross the blood-brain barrier freely? 2.1

A

-small uncharges molecules pass though freely- O2, CO2,
Water crosses through special protein channels in the wall of endothelial cells molecules that dissolve in fat(eg Vit A and D and Drugs that affect brain- antidepressants , psychiatric drugs and heroin cross passively

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20
Q

Give one reason why heroin produces stronger effects than does morphine. 2.1

A

Dissolves in fat (heroin) therefore passively crosses the blood brain barrier

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21
Q

What is the role of the active transport system? What four types of chemicals are transported in this way? 2.1

A 
Transports materials to the brain that can't passively cross 
-glucose
-aa's
-purines
-cholines
-a few vitamins
-iron
And certain hormones
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22
Q

What is the major fuel of neurons? 2.1

A

Depend almost entirely on glucose (as opposed to carbs and fats)
Metabolic pathway of glucose requires oxygen

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23
Q

Why can’t most parts of the adult brain use fuels other than glucose? 2.1

A

Only nutrient (glucose) that crosses blood brain barrier

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24
Q

Why is a shortage of glucose usually not a problem? 2.1

A

Body mobilizes glucose from carbs and fats

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25
Q

Why is a diet low in thiamin a problem? What is Korsakoff’s syndrome? 2.1

A

Vit b, thiamin is needed in order for glucose to be used

Korsakoff’s syndrome-severe memory impairment due to chronic alcoholism => death of neurons

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26
Q

How is the electrical potential across the membrane measured? 2.2

A
  • voltage
  • inserting a very thin micro electrode into the cell body
  • use of a volt meter
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27
Q

What is meant by selective permeability of the membrane? Which chemicals can cross the membrane and which ones cannot? How do a few biologically important ions cross? 2.2

A
  • only certain molecules can cross freely such as O2, CO2, urea water
  • Na, K, Ca, Cl thru membrane gates via active transport
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28
Q

What is the sodium-potassium pump? How does its exchange of sodium and potassium ions lead directly to an electrical potential across the membrane? 2.2

A

The sodium-potassium pump is an active transport mechanism.

It is a protein complex 3 Na2+ out and 2 K+ in

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29
Q

How does selective permeability of the membrane increase the electrical potential? 2.2

A

Prevents the Na ions that were pumped out of the neuron from leaking back in

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30
Q

Describe the competing forces acting on potassium ions. Why don’t all the potassium ions surrounding a neuron migrate inside the cell to cancel the negative charge there? 2.2

A

K+ is positively charged so electrical gradient tends to pull K+ in
But K+ is more concentrated in the cell so concentration gradient tends to drive K+ out.

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31
Q

What is the advantage of expending energy during the “resting” state to establish concentration gradients for sodium and potassium? 2.2

A

Prepares the neuron to rapidly respond

32
Q

What happens to the electrical potential of a cell if a negative charge is applied? What is this change called? 2.2

A

Hyperpolarization- Increased polarization

33
Q

What happens to the potential if a brief, small positive current is applied? What is this change called? 2.2

A

Depolarization - goes toward 0

34
Q

What happens to the potential if a threshold depolarization is applied? 2.2

A

=> rapid depolarization then reversal of depolarization = action potential.

35
Q

What does the term “voltage-activated sodium channels” mean? 2.2

A
  • permeability depends on voltage difference across membrane
  • resting Na channels closed
  • depolarization reached = open and Na flows into the cell.
36
Q

What causes the initial rapid increase in positivity of the action potential? Why doesn’t the potential stop at 0 rather than actually reversing polarity? 2.2

A
  • freely flowing Na into cells.
  • because concentration of Na outside still greater than inside Na continues to flow in until channels close
  • K channels remain open after Na channels close enough K leaves to drive potential to temporary hyperpolarize.
37
Q

What accounts for the ensuing repolarization after there is an initial rapid increase in positivity of the action potential? Why does the neuron hyperpolarize slightly rather than stopping at the previous resting potential?

A

K channels remain open after Na channels close => hyperpolarize

38
Q

What effect does scorpion venom have on the membrane? 2.2

A

Overstimulates the neurons
They can stimulate postsynaptic receptors

(Also some like puffer fish-or nerve impulse is blocked => muscle paralysis)

39
Q

What is the effect of local anesthetic drugs like Novocaine

and Xylocaine? 2.2

A

Attach to Na channels of membrane preventing Na ions from entering therefore there is no action potentials.

40
Q

What is the effect of general anesthetics? 2.2

A

2.2

inhibit nerve transmission at synapse (from web)

41
Q

What is the all-or-none law? How may a neuron signal “greater than”? 2.2

A

Amplitude and velocity of an action potential are independent of intensity of stimulus that initiated it provided the stimulus reached threshold.
Puts constraints on how an axon can send a message.

42
Q

What is the absolute refractory period? What causes it? 2.2

A

Membrane cannot produce an action potential regardless of stimulus.
Immediately after an action potential Na channels closed and K flowing out of the cell at a faster rate.

43
Q

What is a relative refractory period? What causes it? 2.2

A

Second part of refractory period where a larger than normal stimulus is needed.

44
Q

How does and action potential propagate down and axon? 2.2

A

Positive charge flows down the axon

45
Q

What is the major advantage of the myelin sheath and how is this advantage conferred? 2.2

A

Insulates and the flow of ions is faster down the axon

46
Q

What is a node of Ranvier? What would happen if the axon were wrapped with one long expanse of myelin without any nodes of Ranvier? 2.2

A

Small gaps between the myelin sheath.

Helps with saltatory conduction– “to jump”

47
Q

What is saltatory conduction? 2.2

A

Jumping of the action potential from node to node (nodes of Ranvier) when there is a myelin sheath

48
Q

in what ways is transmission by local neurons different from the usual conduction by axons? Why is this local transmission restricted to very short distances? 2.2

A

No axon
Graded potential
Varies in intensity in proportion to stimulus.

49
Q

What is the composition of the membrane covering the neuron? Describe its structure
2.1

A

8 nm thick
2 layers of phospholipid molecules containing chains of fatty acids and a phosphate group.
Embedded among the phospholipids are cylindrical protein molecules through which various chemicals can pass.

50
Q

Plasma membrane

A

A structure that separates the inside of the cell from the outside environment.
2.1

51
Q

Nucleus

2.1

A

The structure that contains the chromosomes

2.1

52
Q

Mitochondrion

2.1

A

Is the structure that performs metabolic activities, providing energy that the dell requires for all other activities.
2.1

53
Q

Ribosomes

2.1

A

Are the sites at which the cell synthesizes new protein molecules.
Proteins provide building materials for the cell and facilitate various chemical reactions.

54
Q

Endoplasmic reticulum

2.1

A

A network of thin tubes that transport newly synthesized proteins to other locations.

55
Q

Motor neuron

2.1

A

A motor neuron has a soma in the spinal cord.

It receives excitation from other neurons through its dendrites and conducts impulses along its axon to a muscle

56
Q

Sensory neuron

2.1

A

Specialized neuron that is highly sensitive to a particular type of stimulation, such as light, sound or touch.

57
Q

Dendrites

2.1

A

Branching fibres that get narrower near their ends. The dendrite’s surface is lined with specialized synaptic receptors at which the dendrite receives information from other neurons. The greater the surface area of a dendrite the more information it can receive.

58
Q

Dendritic spines

2.1

A

These are short outgrowths on dendrites that increase the surface area available for synapses

59
Q

Cell body or soma

2.1

A

Contains the nucleus, ribosomes and mitochondria.
Most of the metabolic work of the neuron occurs here
Range from 0.005 mm to 0.1 mm in mammals and up to a full millimetre in certain invertebrates.

60
Q

Axon

2.1

A

-A thin fibre of constant diameter, in most cases longer than the dendrites
The neurons informations sender
Many axons in vertebrates are covered with an insulating material called the myelin sheath.

61
Q

Presynaptic terminal

2.1

A

An axon has many branches, each of which swells at its tip forming the presynaptic terminal
AKA end bulb or bouton.
This is the point from which the axon releases chemicals that cross through the junction between one neuron and the next.

62
Q

Afferent neuron

2.1

A

“Admits” information into the structure.

63
Q

Efferent axon

2.1

A

2.1 carries information away from the structure

“Exit”

64
Q

Interneuron or intrinsic neuron

2.1

A

2.1

When a cells dendrites and axon are contained within a single structure it is called and interneuron.

65
Q

Glia or neuroglia

2.1

A

The other major components of the nervous system.
Do not transmit information over long distances and neurons do.
Smaller but more numerous than neurons.
Several types of glia: astrocytes, microglia, Schwann cells, oligodendrocytes, and radial glia.

66
Q

Astrocyte

2.1

A

Type of glia (one of 5)
Wrap around presynaptic terminals of a group of functionally related axons.
They take up ions released by axons and then release them back to axons, an astrocyte helps synchronize the activity of the axons enabling them to sent messages in waves.
Also remove waste material created when neurons die and control the amount of blood flow to each brain area.
Also during periods of heightened activity in some brain areas, astrocytes dilate the blood vessels to bring more nutrients to the area.

67
Q

Microglia

2.1

A

Type of glia that are very small.
Function removes waste material as well as viruses, fungi and other microorganisms.
(In effect function like part of the immune system)

68
Q

oligodendrocytes

2.1

A

Located in the brain and spinal cord
Specialized types of glia that build the myelin sheaths that surround and insulate certain vertebrate axons.
Schwann cells have the same function except they are located in the periphery of the body.

69
Q

Schwann cells

2.1

A

Are located in the periphery of the body
They are specialized types of glia that build the myelin sheaths that surround and insulate certain vertebrate axons.
Like Oligodentrocytes which are located in the brain and spinal cord.

70
Q

Radial glia

2.1

A

Function: guide the migration of neurons and their axons and dentrites during embryonic development.
When embryological development finishes most radial glia differentiate into neurons and a smaller number to astrocytes, and oligodendrocytes.

71
Q

Electrical gradient
Aka polarization
2.2

A

In the absence of any outside disturbances the membrane maintains an electrical gradient which is a difference in electrical charge between the inside and outside of the cell.
The neuron inside the membrane has a slightly negative electrical potential with respect to the outside mainly because of negatively charged proteins inside the cell.

72
Q

Resting potential

2.2

A

The difference in voltage in a resting neuron.

73
Q

Selective permeability 2.2

A

Some chemicals pass through the membrane more freely than others.
Oxygen, carbon dioxide, urea and water cross freely through channels that are always open.
Na, K, Ca and Cl cross through membrane channels that are sometimes open and sometimes closed preventing almost all sodium flow. Certain kinds of stimulation can open the the Na channels.
When the membrane is at rest, K channels are nearly but not entirely closed so K flows slowly

74
Q

Sodium-potassium pump 2.2

A

A protein complex that repeatedly transports three sodium ions out of the cell while drawing two potassium ions into it.
This is active transport that requires energy.
Na ions are more than 10x more concentrated outside the membrane than inside and K ions are similarly more concentrated inside.

75
Q

Concentration gradient 2.2

A

The difference in distribution of ions across the membrane

76
Q

Does the all or none law apply to dendrites? Why or why not? 2.2

A

The all or none law does not apply because they do not have action potentials.

Biological Psychology 402 (15 decks)

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