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Psych 314 > Chapter 1 Nerve Cells and Nerve Impulses > Flashcards

Chapter 1 Nerve Cells and Nerve Impulses Flashcards

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1
Q

Cells of the Nervous System [placeholder]

A

.

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2
Q

The adult brain consists of about how many neurons and glia cells?

A

100 billion

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3
Q

Neurons

A
  • receive and transmit information to other cells
  • Aka “nerve cells” or “nerves”
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4
Q

Glia

A
  • don’t transmit information over long distances
  • perform several tasks (we’ll talk about those later)
  • 10 times more numerous than neurons but 1/10 the size; occupy the same amount of space as neurons
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5
Q

Motor Neurons

A

– receive messages in its soma in the brain or spinal cord and sends the message to muscle or gland cells. Responsible for movement. (up to down – brain to muscle)

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6
Q

Sensory Neurons

A
  • specialized to receive particular types of sensory information from our sense organs, and sends that information to the brain. (down to up – for example, from skin to brain)
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7
Q

The Structures of an Animal Cell [placeholder]

A

.

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8
Q

Membrane (aka plasma membrane)

A

Definition

  • a structure that separates the inside of the cell from the outside. Made up of 2 layers of fat molecules

Function

  • Small, uncharged chemicals (H2O, O, CO2) can pass freely across the membrane at any spot
  • Some charged ions (Na, K, Ca, Cl) can cross, but only through special openings called protein channels
  • Most things cannot cross the membrane
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9
Q

Nucleus

A

The structure that contains the chromosomes

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10
Q

Mitochondrion

A

structure where the cell performs metabolic (food into energy) activities.

Provides the cell with energy, needs oxygen and fuel to provide the cell with energy

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11
Q

Ribosomes

A

sites at which the cell synthesizes (make something by synthesis usually chemically) new protein molecules

The site in which synthesis occurs to make new protein molecules

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12
Q

Proteins

A

cell building material and facilitators of chemical reactions

The cell building material that facilitates chemical reactions

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13
Q

Endoplasmic reticulum

A

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

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14
Q

The structure of a Neuron [placeholder]

A

.

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15
Q

Cell body (aka Soma)

A

contains the nucleus and other structures found in most cells

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16
Q

Dendrites

A

Definition

  • branching fibers that get narrower as they extend from the cell body toward the periphery

Function

  • Their surfaces are lined with synaptic receptors that receive information and send it to cell body
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17
Q

Synaptic Receptors

A
  • receive information and send it to cell body
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18
Q

Dendritic Spines

A

short outgrowths that increase the surface area available for receptors

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19
Q

Axon

A

Definition

  • thin fiber of constant diameter, in most cases longer than the dendrites

Function

  • sends information from cell body to the terminal buttons – little branches of nubs on the end of the axon where chemical information is sent out to other neurons, muscles, and glands. TBs aka presynaptic terminals
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20
Q

Terminal Buttons

A

little branches of nubs on the end of the axon where chemical information is sent out to other neurons, muscles, and glands.

TB’s are also known as presynaptic terminals

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21
Q

Myelin Sheath

A
  • insulating material covering axons in many neurons;

Function

speeds up communication along the axon

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22
Q

Nodes of Ranvier

A

The gaps of the myelin sheath

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23
Q

Other Terms Associated With Neurons [placeholder]

A

.

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24
Q

Efferent

A

Axons carries information away from something

Ex: motor neurons are efferent from the brain; they receive excitation from other brain neurons and conduct impulses from the brain to muscle cells (Think “e” for exit!)

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25
Q

Afferent

A

axons brings information into something

Ex: sensory neurons are afferent to the brain; specialized at one end to be highly sensitive to a particular type of stimulation (e.g., touch…travels from hand to brain) (Think “a” for arrive!)

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26
Q

Intrinsic Neuron (or interneuron)

A

As the name suggests, interneurons are the ones in between - they connect spinal motor and sensory neurons. As well as transferring signals between sensory and motor neurons

  • convey information only to immediately adjacent neurons
27
Q

Other Properties of Neurons [placeholder]

A

.

28
Q

Size

A
  • from virtually non-existent to about a meter in length (from spinal cord to feet)
29
Q

Shape

A
  • branching determines connections with other neurons
  • dendrites can grow and extend and retract
30
Q

Types of Glia (aka neuroglia) [placeholder]

A

.

31
Q

Astrocytes (star shaped glia)

A

Function

  • help synchronize activity of several neurons to produce simultaneous firing
  • remove waste material, including dead neurons
32
Q

Radial glia

A

Definition

  • A type of astrocyte

Function

  • guide the migration of neurons
  • guide the growth of axons and dendrites during embryonic development
33
Q

Microglia

A

removes wastes, viruse, fungi, microorganisms

34
Q

Oligodendrocytes

A

Function

are located in the CNS and produce and repair myelin sheaths for axons; their counterparts in the PNS (Peripheral Nervous System) are called Schwann Cells

35
Q

Blood Brain Barrier (BBB) [placeholder] {Still has function, try to guess it right}

A

Function

  • mechanism that keeps most chemicals out of the body
  • Capillaries are tiny tubes that carry blood. Their walls are made up of endothelial cells. In most of our body, these cells have gaps b/t them and things can move back and forth from the blood to the body. But in the brain those cells are pushed tightly together.
  • Small, uncharged molecules, oxygen, CO2, fat soluble molecules (heroin, marijuana, nicotine) passively cross BBB
  • Active transport system pumps glucose, amino acids (protein building blocks), vitamins and hormones into brain
36
Q

Nourishment of Vertebrate Neurons [placeholder]

A

.

37
Q

Glucose

A
  • A simple sugar
  • primary energy source for the brain
  • liver converts carbohydrates, fats and proteins into glucose
38
Q

What is needed to metabolize glucose?

A

Oxygen

39
Q

Thiamine (vitamin B)

A
  • necessary for the use of glucose
  • prolonged deficiency can lead to death of neurons and Korsokoff’s Syndrome (severe memory impairments)
  • Many alcoholics have a diet deficient in thiamine
40
Q

The Nerve Impulse

A
  • Neurons communicate through electrical impulses that travel along the axon 10 -100 meters per second
41
Q

Resting potential or electrical gradient

A

Definition

  • the difference in voltage or electrical charge b/t the in and outside of a neuron

Function

  • An electrical gradient of -70mV (millivolts) exists between inside and outside of neuron cell because far more sodium (NA+) outside than inside
42
Q

A neuron’s membrane is

A

Selectively permeable, some chemicals can pass through more easily than others

43
Q

Why can some chemicals pass through a neuron’s membrane more easily than others?

A
  • A neuron’s membrane has specific Na+ and K+ (and other) channels that allow these elements through.
  • When the membrane is at rest, the Na channels are closed, preventing almost all Na flow, and the K channels are almost closed, so K flow through very slowly (but Na is the slowest)
44
Q

The Na/K pump is a feature of a cell that…

A

that continuously lets 3 Na ions out while allowing 2 K ions in. But the K can leak back in through the channels.

45
Q

How is there always Na on the inside to pump out?

A
  • 2 forces act to continuously push Na back in
  • The electrical gradient – Na is positively charged, so it is attracted to the negatively charged inside of the ion
  • The concentration gradient – concentrated molecules tend to spread out on their own. Na is very concentrated on the outside and wants to go to the inside where it’s less crowded
46
Q

What about K? How is there always K inside?

A
  • K is positively charged, so it likes the inside of the cell. But, it’s more concentrated on the inside, so it also wants to go out. So it pretty much keeps it in balance.
  • Overall, there’s more K on the inside and Na on the outside
47
Q

The Action Potential [placeholder]

If we took an electrode and applied different electrical charges to the inside of a cell we could produce either…

A
  • Hyperpolarization
  • Depolarization
48
Q

Hyperpolarization

A

increase in the negative charge outside of the membrane; returns to rest after small increase

49
Q

Depolarization

A

decrease in the negative charge inside the neuron; returns to rest after small decrease

50
Q

Action Potential

A
  • stimulation beyond a certain level crosses the threshold of excitation and produces a sudden, massive depolarization of the membrane
  • This opens the Na channels and causes Na to rush in, making the inside even more positive
  • rapid depolarization continues to about +30 mV and then returns rapidly to its resting potential
  • So, an action potential is a rapid depolarization and slight reversal of the usual polarization (from negative to positive)
51
Q

The opened Na channel are called?

A

voltage-activated, or voltage-dependent b/c their opening depends on the voltage difference across the membrane

52
Q

The Action Potential Continued

A
  • The threshold is the negative number it has to get to in order to open the channels so it can go positive (somewhere b/t -70 and 0)
  • At the peak of the action potential, the Na channels snap shut and can’t be opened again for a while – no more Na gets in
  • Right before the peak, the K channels open and K flows out of the axon, taking away some positive charge, and bringing it all almost back to normal
  • There’s still a little too much Na in and too much K out, so the Na/K pumps finish it up by bringing it completely back to normal
53
Q

The all-or-none-law

A
  • you either have an AP or you don’t – no in-between
  • the size, amplitude, and velocity of an action potential are independent of the intensity of the stimulus that initiated it
  • It’s the FREQUENCY of APs that sends a strong or weak message
54
Q

Molecular Basis of the Action Potential [placeholder]

A

.

55
Q

Sodium channels

A
  • with slight depolarization, sodium channels open slightly
  • once the threshold is reached, sodium channels open wide and NA+ ions rush into cell
  • at the peak of action potential, sodium channels close and cannot be opened again for next millisecond or so
56
Q

Potassium channels

A
  • open wide as the action potential approaches its peak allowing K+ ions to flow out of the cell
  • cell becomes hyperpolarized and overshoots resting membrane potential, and then returns to -70 mV
57
Q

The Refractory Period [placeholder]

A

.

58
Q

The Refractory Period has 2 parts [placeholder]

A

.

59
Q

Absolute Refractory (1ms)

A
  • the sodium gates are firmly closed
  • the membrane cannot produce an action potential, regardless of the stimulation
60
Q

Relative Refractory Period (another 2-4 ms)

A
  • the sodium gates are reverting to their usual state, but the potassium gates remain open
  • a stronger than normal stimulus can result in an action potential
61
Q

Propagation of the Action Potential

A
  • The action potential begins at the axon hillock – a swelling where the axon exits the soma
  • Remember, the axon is like a long tube and the action potential happens at one part. As NA+ ions enter the axon they depolarize the neighboring area and regenerate the action potential in a flowing action down the axon, like a wave
  • Propagation of the action potential refers to the transmission of an AP down the axon
  • The action potential does not reverse directions because the area where the action potential just came from is still in the refractory period
  • The action potential continues to the pre-synaptic terminals at the end of the axon
62
Q

The Myelin Sheath and Saltatory Conduction

A
  • Speed of impulses increase from <1m/s up to about 10 m/s as diameter of axon increases
  • Myelin sheaths on some axons increase the speed of impulses up to 100 m/s or more

—> area under sheath does not have sodium channels (so can’t regenerate the action potential)

—> sheath is interrupted at intervals of 1mm by unmyelinated sections called Nodes of Ranvier that have sodium channels

—> NA+ ions that started action potential at hillock diffuse rapidly to next Node of Ranvier where action potential is regenerated

63
Q

Saltatory Conduction

A

occurs as action potentials “jump” from node to node

Psych 314 (11 decks)

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