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BMSC 207 > Midterm #1 > Flashcards

Midterm #1 Flashcards

1
Q

What is the definition of physiology?

A

The study of the normal functioning of a living organism and its component parts, including its chemical and physical processes

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2
Q

How is physiology an integrative science?

A

It states that the structure of a cell, tissue, or organ must provide a physical base for its function

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3
Q

What are cells?

A

Smallest unit of structure capable of carrying out life processes

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4
Q

What is a tissue?

A

Collection of cells carrying out related functions

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5
Q

What is an organ?

A

Formation of tissues into a structural and functional unit

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6
Q

What is an organ system?

A

integrated groups of organs

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7
Q

What are emergent properties?

A

Properties of a complex system that cannot be explained by a knowledge of a system’s individual components

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8
Q

What is the difference between the function and the mechanism?

A

Function: why
Mechanism: how

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9
Q

What is the definition of homeostasis?

A

The ability to maintain a relatively stable internal environment despite exposure to external variability

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10
Q

What are some examples of external changes that can be considered threats to homeostasis?

A

Toxic chemicals, physical trauma, foreign invaders

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11
Q

What are some examples of internal changes that can be considered threats to homeostasis?

A

Abnormal cell growth, autoimmune disorders, genetic disorders

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12
Q

What is the proper term for someone who is ill or diseases?

A

They are in a pathophysiological state

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13
Q

What is the Extracellular fluid (ECF)?

A

Is a buffer between cells and the external environment

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14
Q

What is the law of Mass Balance?

A

If the amount of a substance in the body is the remain constant, any gain must be offset by an equal loss

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15
Q

The body compartments are in a dynamic steady state, but are not in equilibrium, but rather a _____ ________.

A

stable disequilibrium

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16
Q

Regulated variables are kept within a normal range by what?

A

control mechanisms

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17
Q

Control systems can be i._____ or ii.______

A

i. local, smaller, and more specific
ii. reflex, widespread

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18
Q

Describe local control

A

It is restricted to the tissues or cells involved

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19
Q

Reflex control uses what kind of signalling?

A

Long-distance

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20
Q

Reflex control refers to any long-distance pathway that uses the ____ system, the _____ system, or both

A

nervous, endocrine

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21
Q

Reflex control is broken down into two parts: 1 and 2

A
  1. Response loop
  2. Feedback loop
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22
Q

What is the purpose of the response loop?

A

Its only job is to sense the cell

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23
Q

What is the purpose of the feedback loop?

A

Response alters the initial stimulus. It modulates the response loop and feeds back to ultimately influence the input

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24
Q

What are the 7 components of the feedback loop?

A
  1. Stimulus
  2. Sensor
  3. Input signal
  4. Integrating center
  5. Output signal
  6. Target
  7. Response
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25
Q

Describe a negative feedback loop

A

A pathway in which the response opposes/removes the stimulus signal

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26
Q

True or False: negative feedback loops destabilize a system?

A

False

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27
Q

True or False: are negative feedback loops homeostatic?

A

True

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28
Q

Negative feedback loops can restore the ____ ____ but cannot prevent the ____ _____

A

initial state, initial disturbance

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29
Q

What is a common example of a negative feedback loop?

A

Blood-glucose concentration

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30
Q

Describe positive feedback loops

A

They reinforce a stimulus to drive the systems away from a normal value rather than decreasing/removing it

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31
Q

True or False: positive feedback loops are homeostatic?

A

False

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32
Q

How do you stop a positive feedback loop?

A

It requires intervention, or an event outside the loop to cease the response

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33
Q

What is one of the few examples of a positive feedback loop?

A

Childbirth

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34
Q

What is feedforward control?

A

Reflexes that have evolved that allow the body to predict a change is about to occur

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35
Q

What are biorhythms?

A

variables that change predictable and create repeating patterns or cycles of changes

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36
Q

What are the 4 functions of a cell membrane?

A
  1. Physical isolation
  2. Regulation of exchange with the environment
  3. Communication between the cell and its environment
  4. Structural support
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37
Q

What is the average composition of a cellular membrane?

A

~55% proteins
~45% lipids
~small amount of carbohydrate

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38
Q

In general, the more _____ _____ the membrane is, the more _____ it contains

A

metabolically active, proteins

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39
Q

What are the three types of lipids found in the cell membrane?

A

Phospholipid, sphingolipid, and cholesterol

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40
Q

Out of the three lipids found in the cell membrane, which is the primary, secondary, and tertiary lipid?

A

Primary - phospholipid
Secondary - sphingolipid
Tertiary - cholesterol

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41
Q

When placed in aqueous solution phospholipids orient themselves so hydrophilic head interacts with water molecules and hydrophobic tails hide. What is the “sheet,” the “droplet,” “and the “aqueous center” called respectively?

A

Sheet: phospholipid bilayer
Droplet: micelle
Aqueous center: liposome

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42
Q

Describe phospholipids

A

They are the major lipid

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43
Q

Describe sphingolipids

A

Lipid rafts, specialized regions of the membrane

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44
Q

Describe cholesterol

A

Positioned between phospholipid heads to add viscosity and help make the membrane impermeable to small water-soluble molecules. Glycoproteins and glycolipids are carbohydrates

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45
Q

What is the fluid mosaic model?

A

Where proteins are dispersed throughout, and the extracellular surface contains glycoproteins and glycolipids

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46
Q

Describe peripheral proteins

A

Attach to integral proteins, and are loosely attached to the phospholipid head

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47
Q

What are the roles of peripheral proteins?

A

Participate in intracellular signaling, and form submembraneous cytoskeleton

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48
Q

What do integral proteins include?

A

Transmembrane proteins and lipid anchored proteins

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49
Q

What are the roles of
integral proteins?

A
  • Membrane receptors
  • Cell adhesion molecules
  • Transmembrane movement
  • Enzymes
  • Mediators of intracellular signaling
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50
Q

Lipid rafts commonly contain an abundance of proteins important in what?

A

cell signal transduction

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51
Q

Describe glycoproteins

A

A protein with a carbohydrate attached, it forms a protective coat (glycocalyx), and is useful for cell-to-cell recognition

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52
Q

Describe glycolipids

A

A lipid with a carbohydrate attached, it forms a protective coat (glycocalyx), and is useful for cell-to-cell recognition

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53
Q

What percentage of the body is considered water?

A

~60%

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54
Q

___, ___, and ____ _____ composition can alter the total water content in the body

A

Age, sex, body fat

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55
Q

Compare adipose tissue with skeletal muscle

A

Adipose: ~90% lipids, small fraction of water, higher in women
Skeletal: ~75% water, ~18% protein, higher in men

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56
Q

Extracellular and intracellular compartments are in _____ equilibrium

A

osmotic

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57
Q

What is osmosis?

A

The movement of water across a membrane in response to a solute concentration gradient

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58
Q

Water moves from a region of ___ solute concentration to a region of ___ solute concentration.

A

low, high

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59
Q

Water can move freely between the intracellular and extracellular spaces via what?

A

Aquaporin channels

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60
Q

True or False: osmotic equilibrium does not equal chemical or electrical equilibrium?

A

True

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61
Q

What is the distribution of ions that are higher in the extracellular fluid?

A

Na+, Cl-, Ca2+, HCO3-

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62
Q

What is the distribution of ions that are higher in the intracellular fluid?

A

K+, anions (HPO4-, H2PO4-), proteins

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63
Q

What is osmotic pressure?

A

The pressure that would have to be applied to oppose and prevent osmosis

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64
Q

Osmolarity describes..?

A

The # of particles in solution. Osmol/L

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65
Q

What is isosmotic?

A

Solutions have identical osmolarities

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66
Q

What is hyperosmotic?

A

Describes the solution with the higher osmolarity

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67
Q

What is hyposmotic?

A

Describes the solution with the lower osmolarity

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68
Q

What is tonicity?

A

Describes a solution and how that solution would affect the cell volume if a cell were placed in the solution and allowed to come to equilibrium

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69
Q

Compare tonicity vs osmolarity in terms of units

A

Osmolarity has units: mOsm/L
Tonicity has no units

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70
Q

Compare tonicity vs osmolarity in terms of what they compare

A

Osmolarity compares two solutions
Tonicity compares solution and a cell

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71
Q

Tonicity depends on the concentration of ___-______ _____

A

non-penetrating solutes

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72
Q

Why does tonicity focus on non-penetrating solutes rather than penetrating solutes?

A

Penetrating solutes can cross the cell membrane and will do so until reaching equilibrium across the membrane when the cell is exposed to the solution, which is why they do not contribute to cell volume changes

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73
Q

What is the difference between osmolarity and osmolality?

A

Osmolarity: osmol/L
Osmolality: osmol/kg

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74
Q

Osmolarity is often used when ____ and ___ are relatively constant

A

temperature, pressure

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75
Q

Diffusion is the movement of molecules from an area of ___ concentration to an area of _____ concentration

A

higher, lower

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76
Q

Diffusion uses what kind of energy, and does it require an outside source?

A

Kinetic energy of molecular movement, and does not require an outside energy source

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77
Q

Under what conditions can diffusion be accelerated?

A
  1. Along higher concentration gradients
  2. Over shorter distances
  3. At higher temperatures
  4. For smaller molecules
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78
Q

Under what conditions can the rate of diffusion through a membrane becomes accelerated?

A
  1. The membrane’s surface area is larger
  2. The membrane is thinner
  3. The concentration gradient is larger
  4. The membrane is more permeable to the molecule
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79
Q

Membrane permeability to a molecule depends on..?

A
  1. The molecule’s lipid solubility
  2. The molecule’s size
  3. The lipid composition of the membrane
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80
Q

What is Fick’s Law of Diffusion?

A

Rate of Diffusion ∝ surface area × concentration gradient × membrane permeability

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81
Q

What is the membrane permeability relationship to lipid solubility and molecular size?

A

Membrane permeability ∝ (lipid solubility/molecular size)

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82
Q

Channel proteins create a ___-filled pore

A

water

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83
Q

What is the composition of channel proteins?

A

Made of membrane spanning proteins subunits that create a cluster of cylinders with a pore through the center

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84
Q

Gated channels are normally closed, so they need a _____ to open the gate

A

stimulus

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85
Q

What are the three kinds of gated channels?

A

Chemically gated (ligand)
Voltage gated
Mechanically gated

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86
Q

Selectivity in channel proteins is determined by the ? and the ? lining the pore, which is usually negative

A

size of the pore, charge of the amino acids

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87
Q

Describe carrier proteins

A

Large complex proteins, change conformation to move molecules, only open one compartment at a time, it is very slow, and they can move small organic molecules that cannot pass through channels

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88
Q

Carrier proteins can be classified into 3 kinds on transporters…?

A
  1. Uniport carriers: one kind of substrate in one direction
  2. Symport carriers (co-transporters): +2 substrates in the same direction
  3. Antiport carriers (exchangers): move +2 substrates in opposite directions
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89
Q

Describe facilitated diffusion

A

Use channels or carrier proteins, they move down their concentration gradient, there is no energy required, and stops once equilibrium is reached

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90
Q

Describe active transport

A

Moves molecules against their concentration gradients (from low to high)
Support a state of disequilibrium
Requires energy
Uses carrier proteins

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91
Q

What are the two kinds of active transport?

A

Primary and secondary

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92
Q

Describe primary active transport

A

The energy to move molecules comes directly from hydrolyzing ATP

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93
Q

Describe secondary active transport

A

Uses the potential energy stored in the concentration gradient of one molecules to push another molecule against their concentration gradient

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94
Q

What is specificity?

A

Refers to the ability of a transport to move one molecule or a closely related group of molecules

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95
Q

What is competition?

A

A carrier may move several members of a related group of substances but these substances compete with one another

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96
Q

What is saturation?

A

Rate of transport depends on concentration and number of transporters. Transport normally increases with increasing concentration until transport maximum is reached

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97
Q

What is phagocytosis?

A

Creates vesicles using the cytoskeleton. It requires ATP to move the cytoskeleton and for intracellular transport of the vesicles

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98
Q

How does endocytosis differ from phagocytosis?

A

Membrane indents
Vesicles are much smaller
Can be constitutive
Also requires ATP

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99
Q

What is the non-selective and selective kinds of endocytosis?

A

Non-selective: pinocytosis (allows ECF to enter)
Selective: receptor mediated transport

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100
Q

_____ can be used instead of clathrin coated pits

A

Caveolae

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101
Q

Substances entering and exiting the body or moving between compartments often cross a layer of _____ cells

A

epithelial

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102
Q

What is absorption?

A

From lumen/organ to ECF

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103
Q

What is secretion?

A

From ECF to lumen/organ

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104
Q

What is another word for the free surface of an epithelial cell?

A

Apical

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105
Q

What are the 3 kinds of epithelial transport?

A

Transcellular, Paracellular, Transcytosis

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106
Q

Describe transcellular transport

A

across epithelial cell

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107
Q

Describe paracellular transport

A

between tight junctions

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108
Q

Describe transcytosis

A

extracellular cargo is endocytosed, shuttled across the cytoplasm in membrane‐bound vesicles, and secreted at a different plasma membrane surface

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109
Q

Why are transporting epithelia polarized?

A

Polarized distribution of membrane transporters ensures one-way movement

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110
Q

Compare passive vs. active vs. vesicular vs. epithelial transport in terms of energy

A

Passive: does not require energy
Active: require energy
Vesicular: requires energy
Epithelial: sometimes requires energy

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111
Q

Compare passive vs. active vs. vesicular vs. epithelial transport in terms of types

A

Passive: simple and facilitated
Active: primary and secondary
Vesicular: phago, endo, and exocytosis
Epithelial: paracellular, transcellular, and transcytosis

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112
Q

The body as a whole is electrically ______

A

neutral

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113
Q

What is the membrane potential difference or membrane potential (Vm)?

A

The electrical disequilibrium that exists between the ECF and ICF

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114
Q

What is the electrochemical gradient?

A

The combination of electrical and concentration gradients

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115
Q

What is equilibrium potential?

A

The membrane potential that exactly opposes the concentration gradient

116
Q

What is the resting membrane potential?

A

The membrane potential of a cell when it is not active

117
Q

What is the function of Na-K ATPase?

A

Sets up concentration gradients that determines membrane potential, and maintains the concentration gradients for Na+ and K+

118
Q

If the membrane potential becomes less negative than the resting potential the cell ____

A

depolarizes

119
Q

If the membrane potential becomes more negative, it ______

A

hyperpolarizes

120
Q

Describe the nervous system?

A

Coordinates voluntary and involuntary actions and transmits signal to and from different parts of its body

121
Q

What is the term Afferent?

A

Carry information towards CNS

122
Q

What is the term Efferent?

A

Carry information away from CNS

123
Q

What is included in the Central Nervous System?

A

Brain and spinal cord

124
Q

What is included in the Peripheral Nervous System (PNS)?

A

Nerve tissue outside the CNS: cranial nerves and branches, spinal nerves and branches, ganglia, plexuses, and sensory receptors

125
Q

What are the 2 subdivision of the peripheral nervous system?

A

Afferent (sensory) division
Efferent (motor and autonomic) division

126
Q

What comprises the efferent division?

A

Somatic motor and autonomic

127
Q

What three components feed into the afferent division?

A

Somatic sensory
Visceral sensory
Special sensory

128
Q

What are neurons?

A

Basic signaling units of the nervous system

129
Q

What are glia?

A

support cells

130
Q

What is the cell body (soma)?

A

Considered the control center, with processes that extend outward; dendrites and axons

131
Q

What are dendrites?

A

Receive incoming signals from neighboring cells

132
Q

What are axons?

A

Carry outgoing signals from the integrating center to target cells

133
Q

What are presynaptic terminals?

A

Contain transmitting elements

134
Q

What is the synapse?

A

The region where an axon terminal communicates with its postsynaptic target cell

135
Q

Describe afferent (sensory) neurons

A

Carry information about temperature, pressure, light, and other stimuli to the CNS
Specialized receptor converts stimulus to electrical energy

136
Q

What are interneurons?

A

Complex branching neurons that facilitate communication between neurons

137
Q

Describe efferent (motor and autonomic) neurons

A

Motor: control skeletal muscles
Autonomic: influences many internal organs
Usually have axon terminals or varicosities

138
Q

What are the two categories of the autonomic neuron?

A

Sympathetic and parasympathetic

139
Q

What are nerves?

A

Bundles of peripheral neurons, they can be efferent, afferent or mixed

140
Q

The axon is specialized to convey ____ and ____ _____ that require a variety of different types of proteins

A

chemical and electrical signals

141
Q

The axon contains many types of ____ and _____ but lacks ____ and ___ necessary for protein production

A

fibers and filaments, ribosomes and ER

142
Q

Arrange the following statements into the proper order of axonal transport:
1. Synaptic vesicle recycling
2. Fast axonal transport walks vesicles and mitochondria along microtubule network
3. Vesicle contents are released by exocytosis
4. Retrograde fast axonal transport
5. Old membrane components digested in lysosomes
6. Peptides are synthesized on rough ER and packaged by the Golgi

A

6, 2, 3, 1, 4, 5

143
Q

What is considered fast axonal transport?

A

Membrane bound proteins and organelles (vesicles or mitochondria). Anterograde (up to 400mm/day) and retrograde (up to 200mm/day)

144
Q

What direction is anterograde?

A

cell body to axon terminal

145
Q

What direction is retrograde?

A

axon terminal to cell body

146
Q

What is slow axonal transport?

A

Cytoplasmic proteins (enzymes) and cytoskeleton proteins. Not well characterized, may be due to frequent periods of pausing of movements

147
Q

What are kinesins?

A

Anterograde transport

148
Q

What are dyneins?

A

Retrograde transport

149
Q

___ ____ drives movement of proteins to “walk” along filaments

A

ATP hydrolysis

150
Q

In the synapse, the space contains ____ ____ that hold the pre and post synaptic cells in close proximity

A

extracellular matrix

151
Q

Axons of embryonic neurons contain _____ _____ that sense and move towards particular chemical signals

A

growth cones

152
Q

Growth cones depend on..?

A

Growth factors
Molecules in the extracellular matrix
Membrane proteins

153
Q

Synapse must be maintained through ?

A

Repeated use

154
Q

Where are glial cells found?

A

Ependymal cells - CNS
Astrocytes - CNS
Microglia - CNS
Oligodendrocyte - CNS
Schwann cells - PNS
Satellite cells - PNS

155
Q

What is myelin?

A

A substance composed of multiple concentric layers of phospholipid membrane wrapped around an axon

156
Q

What is the purpose of myelin?

A

Provides structural stability, acts as insulation around the axon to speed up electrical signals, supply trophic factors

157
Q

Where do you find myelin in the CNS?

A

oligodendrocyte

158
Q

Where do you find myelin in the PNS?

A

Schwann cells

159
Q

Where do you find satellite glial cells?

A

Exist within ganglia in the PNS

160
Q

What is the purpose of satellite glial cells?

A

Form a supportive capsule around the bodies of neurons. Supply nutrients, structural support, and provide a protective cushion

161
Q

What are astrocytes?

A

Highly branched glial cells in the CNS believed to make up half of all cells in the brain. There are several subtypes that form a functional network

162
Q

What are the four functions of astrocytes?

A

Take up and release chemicals at synapses
Provide neurons with substrates for ATP production
Help maintain homeostasis in the ECF
Surround vessels (part of the blood-brain barrier)

163
Q

What are microglia?

A

Specialized immune cells that reside in the CNS

164
Q

What is the purpose of microglia?

A

Serve to protect and preserve neuronal cells from pathogens and facilitate recovery from metabolic insults

165
Q

If the signals that activate microglia pass a threshold with respect to intensity, or microglia remain activated past a certain time period, these cells start to display..?

A

Detrimental properties

166
Q

What are ependymal cells?

A

Line fluid filled cavities in the brain and spinal cord

167
Q

What is the purpose of ependymal cells?

A

Help to circulate cerebrospinal fluid that fills these cavities and surrounds the brain and spinal cord. Is for protection, chemical stability, and clearing wastes

168
Q

What is the difference in the ability to repair a neuron injury between the PNS and CNS?

A

CNS repair is less likely to occur naturally, as the glia tend to seal off and form scar tissue. However, the PNS can repair naturally

169
Q

Schwann cells can create a tube to ____ the regenerating axon

A

guide

170
Q

What does the Goldman-Hodgkin-Katz equation predict?

A

That membrane potential that results from the contribution of all ions that can cross the membrane

171
Q

How is the Goldman-Hodgkin-Katz equation determined?

A

As the combined contribution of each ion (concentration x permeability) to the membrane potential

172
Q

How does the Goldman-Hodgkin-Katz equation and Nernst equation differ?

A

Goldman-Hodgkin-Katz equation: combined contribution of each ion
Nernst equation: calculates the equilibrium potential for a single ion

173
Q

What is the resting membrane potential in most neurons? What mainly causes that?

A

~-70mV, mainly caused by K+

174
Q

What alters the membrane potential?

A

A change in the K+ concentration or a change in permeability to ions

175
Q

A significant change in membrane potential does not indicate ..?

A

A change in concentration gradient of a given ion

176
Q

How many ions need to move to alter the membrane potential?

A

Very few

177
Q

The concentration gradients for ions remain relatively ____ during most alterations in membrane potential

A

constant

178
Q

Ion permeability is primarily altered by ..?

A

Opening/closing ion channels in the membrane

179
Q

What are the 5 major types of ion channels?

A
  1. Na+
  2. K+
  3. Ca2+
  4. Cl-
  5. Monovalent cation channels
180
Q

What is conductance?

A

The ease with which ions flow through a channel

181
Q

How do mechanically gated channels open?

A

Open in response to physical forces found in sensory neurons

182
Q

How do chemically gated channels open?

A

In neurons respond to ligands including extracellular neurotransmitters and neuromodulators or intracellular signaling molecules

183
Q

How do voltage gated channels open?

A

Respond to changes in the cells membrane potential

184
Q

What are some examples of variation in gated channels?

A
  1. Voltage required for channel opening
  2. The speed at which channels open/close
  3. Many channels that open to depolarizations will close during repolarization
  4. Some channels spontaneously inactivate
  5. Each major channel type has subtypes
185
Q

What is the affect of this channelopathy: mutation alter permeation pathways?

A

Can disrupt how ions normally flow through the ion channel

186
Q

What is the affect of this channelopathy: mutation changes channel activation?

A

Can alter channel activation

187
Q

What is the affect of this channelopathy: mutation change channel inactivation process?

A

Can alter channel inactivation

188
Q

What is current?

A

The flow of electrical charge carried by an ion

189
Q

What is Ohm’s law?

A

Current flow (I) is ∝ to the electrical potential different (V) between two points and inversely proportional to the resistance (R); I = V/R

190
Q

What are two sources of resistance in a cell?

A

Membrane resistance (Rm) - resistance of phospholipid bilayer
Internal resistance of the cytoplasm (Ri) - cytoplasmic composition and size of the cell

191
Q

Resistance will determine..?

A

How far current will flow in a cell before the energy is dissipated

192
Q

Voltage changes across the membrane can be classified
in to two types of electrical signals..?

A
  1. Graded potentials
  2. Action potentials
193
Q

What are graded potentials?

A

Variable strength signals that travel over short distances and lose strength as they travel. They can be depolarizing or hyperpolarizing. If graded potentials create a large enough depolarization, it can induce an action potential

194
Q

What are action potentials?

A

Very brief, large depolarizations that travel for long distances through a neuron without losing strength. Rapid signals over long distances

195
Q

Where are the graded/action potentials in the CNS and efferent neurons?

A

Graded: dendrites, nucleus, and soma
Action: axon, and axon terminals

196
Q

Where are the graded/action potentials in sensory neurons?

A

Graded: sensory receptors
Action: peripheral process, central process, axon

197
Q

Why are graded potentials considered “graded”?

A

Because amplitude (size) is directly proportional to the strength of the stimulus an can vary

198
Q

How are graded potentials generated?

A

By the chemically gated (ligand gated) ion channels or closure of leak channels (CNS and efferent neurons)

199
Q

What is local current flow?

A

A wave of depolarization or hyperpolarization that moves through the cell

200
Q

Graded potentials lose strength as they move through the cell due to..?

A
  1. Current leak: open channels allow ions to leak out
  2. Cytoplasmic resistance
201
Q

Between depolarization and hyperpolarization, which is excitatory and which is inhibitory?

A

Depolarization: excitatory postsynaptic potential (EPSP)
Hyperpolarization: inhibitory postsynaptic potential (IPSP)

202
Q

What is the trigger zone?

A

AKA the axon hillock. There is a high concentration of voltage gated Na+ channels, and if the membrane potential is ~-55mV, and action potential will be generated

203
Q

Where do action potentials travel?

A

Electrical signals of uniform strength that travel from the trigger zone to the axon terminals

204
Q

____ opening of voltage gated ion channels in the axon membrane as electrical current moves down.

A

Sequential

205
Q

What is conduction?

A

Movement of an action potential along the axon, they travel over long distances without losing energy

206
Q

True or False: action potentials travel through the cell

A

False, not a single action potential that travels through the cell but rather a new action potential generated in each adjacent area

207
Q

Conduction of the action potential requires a few types of ion channels..?

A

Voltage gated Na+ and K+ channels as well as the leak channels that help set the resting membrane potential

208
Q

Voltage gated Na+ and K+ channels are both activated by _____, K+ channels just open more slowly

A

depolarization

209
Q

Order these steps into the proper chronological order:
1. Na+ channels close and slower K+ channels open
2. Depolarizing stimulus
3. Cell returns to resting ion permeability and resting membrane potential
4. Rapid Na+ entry depolarizes cell
5. Resting membrane potential
6. K+ channels remain open and additional K+ leaves the cell, hyperpolarizing it
7. K+ moves from the cell to ECF
8. Voltage gated K+ channels close, less K+ leaks out of the cell
9. Membrane depolarizes to threshold. Voltage gated Na+ and K+ channels begin to open

A

5, 2, 9, 4, 1, 7, 6, 8, 3

210
Q

What is the rising phase?

A

Depolarization
Depolarizing stimuli open voltage gated Na+ channels, allow Na+ to travel down electrochemical gradient

211
Q

What is the falling phase?

A

Repolarization
Voltage gated K+ channels also open in response to depolarization, but do so more slowly than Na+ channels causing delayed efflux

212
Q

What is the after-hyperpolarization phase?

A

Undershoot. Voltage gated K+ do not immediately close when reaching -70mV, causing the membrane potential to dip below the resting membrane potential. Leak channels bring the membrane potential back to -70mV

213
Q

___ ___ returns ions to original compartments

A

Na-K ATPase

214
Q

Compare graded and action potential in terms of what type of signal?

A

Graded: input signal
Action: regenerating conduction signal

215
Q

Compare graded and action potential in terms of where it ocurs?

A

Graded: usually dendrites and cell boy
Action: trigger zone through the axon

216
Q

Compare graded and action potential in terms of the types of gated ion channels involved?

A

Graded: mechanically, chemically, or voltage gated channels
Action: voltage gated channels

217
Q

Compare graded and action potential in terms of the ions involved?

A

Graded: usually Na+, K+, Ca2+
Action: Na+, K+

218
Q

Compare graded and action potential in terms of depolarizing/hyperpolarizing?

A

Graded: depolarizing or hyperpolarizing
Action: depolarizing

219
Q

Compare graded and action potential in terms of the strength of the signal?

A

Graded: depends on the initial stimulus, can be summed
Action: all-or-none, cannot be summed

220
Q

Compare graded and action potential in terms of what initiates the signal?

A

Graded: entry of ions through gated channels
Action: above-threshold graded potential at the trigger zone opens ion channels

221
Q

Compare graded and action potential in terms of unique characteristics?

A

Graded: no minimum level requires to initiate, two signals coming close together will sum, initial stimulus strength is indicated by the frequency of a series of action potentials
Action: threshold stimulus required to initiate, refractory period: two signals too close together in time cannot sum

222
Q

How do voltage gated Na+ channels suddenly close at the peak of an AP?

A

Contains two gates: an activation gate and an inactivation gate.

223
Q

What are the steps in closing a voltage gated Na+ channel?

A
  1. With activation gate open. Na+ enters the cell
  2. Inactivation gate closes and Na+ entry stops
  3. During repolarization caused by K+ leaving the cell, the two gates reset to their original positions
224
Q

Double gating of Na+ channels creates a ____ ____

A

refractory period

225
Q

What is an absolute refractory period?

A

A second AP cannot be initiated 1-2msec

226
Q

What is a relative refractory period?

A

A second AP can be initiated but requires a larger than normal depolarizing stimulus (graded potential) 2-5msec

227
Q

What is the purpose of a refractory period?

A

Ensures an AP travels in one direction, and limits the rate at which signals can be transmitted down a neuron

228
Q

When ____ ions enter the neuron, current flows to ____ sections of the axon

A

positive, adjacent

229
Q

Order the steps in how action potentials are conducted:
1. Local current flow causes new section of the membrane to depolarize
2. Voltage-gated Na+ channels open, and Na+ enters the axon
3. Graded potential enters trigger zone
4. Positive charge spreads along adjacent sections of axon by local current flow
5. The refractory period prevents backwards conduction
6. Loss of K+ repolarizes the membrane

A

3, 2, 4, 1, 6, 5

230
Q

What are the two physical parameters to determine the velocity of conduction?

A
  1. The diameter of the axon
  2. The resistance of the axon membrane to ion leakage
231
Q

What is the relationship between the velocity of conduction and the diameter of the axon?

A

A larger diameter axon will offer less internal resistance to current flow

232
Q

AP conduction is more rapid in axons with ___-____ membranes (decreased current leak)

A

high resistance

233
Q

Nodes of Ranvier contain an abundance of ___ channels

A

Na+

234
Q

____ axons are larger diameter axons (10µm ~120m/sec), ______ axons are smaller diameter axons (1.5µm ~2m/sec)

A

myelinated, unmyelinated

235
Q

Due to the fact that only nodes contain Na+ channels, the AP cannot be maintained in the ____ region, due to a lack of Na+ channels

A

unmyelinated

236
Q

Current leaks out of the _____ region, increasing the likelihood that the ___ __ _____ is subthreshold

A

unmyelinated, wave of depolarization

237
Q

Chemicals exist that can interfere with ______ by binding to Na+, K+, or Ca2+ channels in the neuron

A

conduction

238
Q

Electrical activity can also be altered through changes in _____ ____ of certain ions

A

extracellular concentration

239
Q

The concentration gradient for ___ is crucial in setting the resting membrane potential

A

K+

240
Q

Neurons communicate at ___

A

synapses

241
Q

Neurons communicate at synapses: ______ ___ (neuron) to ______ ____ (neuron, muscle, taget cell)

A

presynaptic cell, postsynaptic cell

242
Q

Describe electrical synapses and where they may be found

A

Ions flow from one cell directly to the next. May be found in: some CNS neurons, cardiac muscle, smooth muscle

243
Q

Describe chemical synapses and where they may be found

A

Electrical signals from the presynaptic cell is converted to a neurocrine signal that crosses the synaptic cleft and binds to a receptor on the postsynaptic cell
May be found in: the majority of neurons in the nervous system

244
Q

What is a neurocrine?

A

A chemical substance released from neurons used for cell-to-cell communication

245
Q

What are the three types of neurocrine?

A

Neurotransmitters, neuromodulators, neurohormones

246
Q

What are neurotransmitters?

A

A chemical that is released, acts on a postsynaptic cell in close vicinity and causes a rapid response in the postsynaptic cell

247
Q

What are neuromodulators?

A

A chemical that is released, acts on a postsynaptic cell in close vicinity and causes a slow response in the postsynaptic cell

248
Q

What are neurohormones?

A

Are secreted into the bloodstream and act on targets throughout the body

249
Q

The ____ neurocrine can act as a ____ at one synapse and a _____ at another depending on the receptors present

A

same, neurotransmitter, neuromodulator

250
Q

There are 2 categories of neurocrine receptors: ?

A
  1. Ionotropic receptors (ligand gated channels)
  2. Metabotropic receptors (g-protein coupled receptors)
251
Q

Ligand binding to ionotropic receptors causes a ______ change leading to the opening of the channel

A

conformational

252
Q

True or False: ionotropic receptors are only specific for one ion?

A

False: they can be specific or a non-selective cation channel

253
Q

Do ionotropic receptors mediate fast/slow postsynaptic responses? And which neurocrine can this be aligned with?

A

Fast, neurotransmitter

254
Q

Do metabotropic receptors mediate fast/slow postsynaptic responses? And which neurocrine can this be aligned with?

A

Slow, neuromodulators

255
Q

The cytoplasmic tail of the receptor is linked to ? (aka the g-protein)

A

three part membrane transducer protein

256
Q

Ligand binding to metabotropic receptor leads to 2 different g-protein mediated cellular responses: ?

A
  1. Interact directly with ion channels
  2. Activate membrane bound enzymes
257
Q

In metabotropic receptors, when they interact directly with ion channels, what does this lead to?

A

Can lead to the opening or closing of a channel depending on the g-protein

258
Q

In metabotropic receptors, there are two main types of interactions with a membrane bound enzyme: ?

A

A. Phospholipase C Signal transduction pathway
B. Adenylyl cyclase signal transduction pathway

259
Q

Describe the phospholipase C signal transduction pathway

A

There is an increase in intracellular Ca2+ that mediates a cellular response. PKC can also mediate a cellular response

260
Q

Describe the adenylyl cyclase signal transduction pathway

A

PKA phosphorylates proteins to cause a cellular response

261
Q

True or False: one neurocrine can have multiple receptors?

A

True

262
Q

Vesicles containing neurotransmitter accumulate in the ___ ____ ready to be released on demand

A

axon terminal

263
Q

Describe synthesis in terms of neurotransmitters in vesicles

A

Large peptide neurotransmitters are produced and packaged into vesicles at the soma and transported by fast axonal transport. They are dense core vesicles

264
Q

Small neurotransmitters are synthesized and packaged at the ___ ____ (empty vesicles transported from soma or recycled vesicles)

A

axon terminal

265
Q

The enzymes for synthesis are brought to the terminal via ___ axonal transport

A

slow

266
Q

Neurotransmitter release occurs via..?

A

Ca2+ mediated exocytosis

267
Q

The presynaptic terminal contains a high concentration of ____-_____ __ channels

A

voltage-gated Ca+

268
Q

Neural signaling of ___ duration is due to the..?

A

short, rapid removal or inactivation of neurotransmitter in the synaptic cleft

269
Q

Neurotransmitter binding depends on the ____ in the cleft

A

concentration

270
Q

Order these statements into the proper order:
1. Enzymes inactivate neurotransmitters
2. Neurotransmitters can diffuse out of the synaptic cleft
3. Neurotransmitters can be returned to axon terminals for reuse or transported into glial cells

A

3, 1, 2

271
Q

A single AP releases a ___ ____ of neurotransmitter in one neuron

A

set amount

272
Q

Increased AP firing leads to ? and ?

A

A greater influx of Ca2+
Increased neurotransmitter release

273
Q

True or False: one excitatory event is often not enough to reach threshold in the postsynaptic cell?

A

True

274
Q

What is convergence?

A

Many presynaptic neurons may converge on one or a small number of postsynaptic neurons

275
Q

What is divergence?

A

Neurons can have branching axons that contact many different postsynaptic neurons

276
Q

Input from ? on a single postsynaptic neuron is summated to determine the output of the postsynaptic neuron

A

multiple presynaptic neurons converging

277
Q

In terms of neurons, what is the meaning of spatial?

A

Different locations

278
Q

Spatial summation occurs when..?

A

Currents from multiple nearly simultaneous graded potentials combine

279
Q

Each individual EPSP is subthreshold, but..?

A

All reach a trigger zone simultaneously and summate

280
Q

True or False: spatial summation is only promotional in nature?

A

False: it can be inhibitory

281
Q

Graded potentials from the ___ presynaptic neuron arriving at the trigger zone nearly ______ may be summated

A

same, simultaneously

282
Q

What is postsynaptic integration?

A

When both temporal and spatial graded potentials are incorporated in a neuron

283
Q

What is an axo-axonic synapse?

A

Excitatory or inhibitory neurons may synapse on synaptic terminals and augment communication

284
Q

What is presynaptic inhibition?

A

Inhibits neurotransmitter release

285
Q

What is presynaptic facilitation?

A

Increases neurotransmitter release

286
Q

Synaptic activity can be altered by changing the target (postsynaptic) cell’s ______ to a neurotransmitter

A

responsiveness

287
Q

How can a cell’s responsiveness to a neurotransmitter be altered?

A

Usually be changing the structure, affinity, or number of neurotransmitter receptors

BMSC 207 (3 decks)

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