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Human Physiology > Unit 1 > Flashcards

Unit 1 Flashcards

1
Q

Controlled Variable

A

A parameter that is monitored and regulated.

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2
Q

Negative Feedback

A

A mechanism in which an initial stimulus leads to changes that oppose/negate the stimulus.

Negative feedback mechanisms are used to regulate/normalize homeostatic variables.

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3
Q

Positive Feedback

A

A mechanism in which an initial stimulus leads to changes that amplify/increase the stimulus.

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4
Q

Set Point

A

The acceptable value/range of a controlled variable.

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5
Q

Stimulus

A
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6
Q

Receptor

A

A structure/compound that detects the current value of a controlled variable.

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7
Q

Effector

A

A structure/compound that produces a change to bring the controlled variable closer to the set point value/range.

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8
Q

Control Center

A

A structure that compares the current value (of a controlled variable) to the set point and sends commands to effectors to correct deviations from the set point.

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9
Q

Homeostasis

A

The maintenance of a relatively stable internal environment amidst a changing external environment and varying internal activity.

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10
Q

Temperature Homeostasis: Elevated Body Temperature

A
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11
Q

Temperature Homeostasis: Lowered Body Temperature

A
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12
Q

Equilibrium

A
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13
Q

Homeostasis vs. Equilibrium

A
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14
Q

Body Fluids

A
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15
Q

Intracellular Fluid (ICF)

A
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16
Q

Extracellular Fluid (ECF)

A
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17
Q

Interstitial Fluid

A
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18
Q

Plasma

A
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19
Q

What does the internal environment of the body refer to?

A
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20
Q

Disorder

A
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21
Q

Disease

A
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22
Q

Active Transport

A

The transmembrane movement of solutes/substances against their electrochemical gradient that requires the input of cellular energy.

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23
Q

Physiology

A

The study of how the human body functions in health and disease.

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24
Q

Error

A

A deviation from the set point value/range.

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25
Q

Examples: Negative Feedback

A
  • Regulation of Blood Pressure
  • Regulation of Blood Glucose Levels
  • Regulation of Body Temperature
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26
Q

Examples: Positive Feedback

A
  • Oxytocin Release During Contractions
  • Estrogen Surge Prior to Ovulation
  • Prolactin Production During Breastfeeding
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27
Q

Which organ systems assist with body temperature control?

A
  • Nervous System
  • Cardiovascular System
  • Integumentary System
  • Endocrine System
  • Muscular System
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28
Q

Homeostatic Regulation: Elevated Body Temperature

A
  • Vasodilation: Heat Dissipation via Perfusion
  • Perspiration: Heat Dissipation via Evaporation
  • Behavioral Response: Shade Seeking
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29
Q

Homeostatic Regulation: Lowered Body Temperature

A
  • Vasoconstriction: Decreased Heat Dissipation
  • Shivering Thermogenesis: Muscle Contractions Produce Heat
  • Non-Shivering Thermogenesis: Brown Fat Cell Stimulation Produces Heat
  • Behavioral Response: Shelter Seeking
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30
Q

Control Center: Temperature Regulation

A

Hypothalamus

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31
Q

Why do people often shiver at the start of a fever?

A

The current body temperature (37°C) is below the body temperature set point (>37°C).

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32
Q

Why do people often sweat when a fever breaks/ends?

A

The current body temperature (>37°C) is above the body temperature set point (37°C).

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33
Q

Flow

A

The movement of molecules/substances from one point (of a system) to another point (of the system).

  • Particles (e.g. Molecules, Ions)
  • Fluids (e.g. Air, Blood, Chyme)
  • Heat (e.g. Dissipation through Blood Vessels)
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34
Q

Why does flow occur?

A

Footnote

The existence of an energy gradient between two points (of a system)

  • Particle flow results from a chemical/electrical gradient.
  • Fluid flow results from a pressure gradient
  • Heat flow results from a thermal gradient.
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35
Q

What is the driving force of flow?

A

An Energetic Gradient

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36
Q

Relationship: Flow vs. Gradient

A

The flow rate is directly proportional to the magnitude of the gradient.

I.e. The larger the gradient, the greater the flow rate.

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37
Q

Relationship: Flow vs. Resistance

A

The flow rate is inversely proportional to the magnitude of resistance.

I.e. The larger the resistance, the lower the flow rate.

38
Q

Relationship: Flow vs. Gradient vs. Resistance

A
39
Q

Equation: Fick’s Law

A

  • J = Net Diffusion Rate (of Particle Crossing Membrane)
  • D = Diffusion Coefficient (of Particle)
  • A = Membrane Surface Area
  • ΔC = Concentration Gradient (of Particle)
  • ΔX = Membrane Thickness
40
Q

Definition: Fick’s Law of Diffusion

A

A mathematical relationship that expresses the various factors determining the rate of diffusion of a particle across a membrane (from one region to another region).

41
Q

Chart: Simple Diffusion

A
  • Energy Source: Movement Along Concentration Gradient
  • Other Molecules Involved: None
  • Direction: Along/Down Concentration Gradient

E.g. Diffusion of Oxygen (O2)

42
Q

Chart: Facilitated Diffusion

A
  • Energy Source: Movement Along Concentration Gradient
  • Other Molecules Involved: Channel/Carrier Protein
  • Direction: Along/Down Concentration Gradient

E.g. Transport of Na+ Into Cell

43
Q

Chart: Primary Active Transport

A
  • Energy Source: Cellular Energy (ATP)
  • Other Molecules Involved: Protein Pump
  • Direction: Against Concentration Gradient

E.g. Transport of Na+ Out of Cell; Transport of K+ Into Cell (Na+/K+ ATPase)

44
Q

Chart: Secondary Active Transport

A
  • Energy Source: Coupling to Favorable EC Gradient Movement
  • Other Molecules Involved: Protein Carriers (Symporters/Antiporters)
  • Direction: Against Concentration Gradient

E.g. Transport of Na+ Into Cell + Transport of Glucose Into Cell (Na+/Glucose Symporter)

45
Q

Symporter

A
46
Q

Antiporter

A
47
Q

Osmosis

A

Diffusion of Water

  • Osmosis can occur via simple diffusion or facilitated diffusion.
  • Osmosis always occurs toward the region of higher solute concentration.
48
Q

Active Transport: Primary vs. Secondary

A
  • Primary: A direct cellular energy source (e.g. ATP) is used to pump a compound against its concentration gradient.
  • Secondary: The coupling of energetically favorable EC movement (i.e. the indirect usage of ATP) with energetically unfavorable EC movement to transport a compound against its concentration gradient.
49
Q

Relationship: [H2O] vs. [Solute]

A

Inverse Relationship

The higher the solute concentration, the lower the H2O concentration.

50
Q

Why is it beneficial for liver cells to convert glucose to glycogen?

A

The conversion of glucose to glycogen reduces the compound’s contribution to intracellular osmolarity.

51
Q

Should intravenous distilled H2O be administered to a dehydrated patient?

A

No: Distilled H2O is extremely hypotonic relative to human body cells.

The extreme hypoteonicity of distilled H2O will cause body cells to burst.

52
Q

Why is coconut water a better alternative than distilled H2O for treating a dehydrated patient?

A

The tonicity of coconut water is closer (than that of distilled H2O) to the tonicity of blood plasma.

Since coconut water is more isotonic (relative to blood plasma) than distilled H2O, it will result in mild/minimal swelling of body cells.

53
Q

Sodium-Potassium Pump

Na+/K+ ATPase

A

A transmembrane protein that pumps 3 Na+ ions out of the cell and 2 K+ ions into the cell.

  • The Sodium-Potassium Pump uses about one-third of all ATP in the human body. (In neurons, the Na+/K+ Pump uses about 70% of available ATP.)
  • The Na+/K+ Pump establishes large Na+ and K+ concentration gradients across the cell membrane.
54
Q

Typical Intracellular/Extracellular Ion Concentrations

A
  • Na+: Low Intracellular [Na+]; High Extracellular [Na+]
  • K+: High Intracellular [K+]; Low Extracellular [K+]
  • Ca2+: Low Intracellular [Ca2+]; High Extracellular [Ca2+]
  • Cl–: Low Intracellular [Cl–]; High Extracellular [Cl–]
55
Q

Relative Charge of Cell

A

Negative (Membrane Potential)

I.e. The intracellular environment of a typical cell is more negative than the extracellular environment.

56
Q

How do you determine the net direction of ion flow for a cell with a membrane potential of 0 mV?

A

You must determine the direction of the ion’s chemical gradient.

57
Q

Equilibrium Potential

Eion

A

The membrane potential at which an ion’s concentration gradient and electrical gradient are equal in magnitude and opposite in direction.

At equilibrium potential, there is no net movement of the ion across the plasma membrane.

58
Q

Nernst Equation

A

  • z = Charge of Ion
59
Q

Cell Permeability: Na+ vs. K+

A

The typical cell is significantly more permeable to K+ ions than to Na+ ions.

I.e. There is greater resistance to flow of Na+ ions into the cell. (For the Na+ flow rate to equal the K+ flow rate, Na+ must experience a stronger electrochemical gradient to compensate for the higher resistance.

60
Q

Goldman-Hodgkin-Katz (GHK) Equation

A
61
Q

Nernst Equation vs. GHK Equation

A
  • Nernst: Used to calculate an ion’s equilibrium potential (given the intracellular/extracellular concentrations of the ion).
  • GHK: Used to calculate a neuron’s resting membrane potential.
62
Q

Membrane Channels: Selectivity

A

The characteristic of only letting certain ions pass through the cell membrane.

E.g. K+ Leak Channels

63
Q

Membrane Channels: Gating

A

The characteristic of only letting certain ions pass through the cell membrane at certain times.

64
Q

K+ Leak Channel

A

A selective transmembrane ion channel with a negatively charged internal domain.

  • The K+ leak channel possesses negative internal residues that mimic the spacing of H2O molecules around a solvated K+ ion.
  • It is equally favorable for the K+ ion to be dissolved in water or within the K+ ion leak channel.
65
Q

Why do dissolved ions become hydrated?

A

The solvation of ions by H2O (i.e. the interaction of ionic charges with H2O’s partial charges) creates a more energetically favorable state.

66
Q

Why is the K+ Leak Channel unselective for Na+ ions?

A

The internal diameter of the K+ leak channel is too wide to adequately “hydrate” the Na+ ion.

It is less energetically favorable for the Na+ ion to be within the K+ leak channel. (It is more energetically favorable for the Na+ ion to be dissolved in water.)

67
Q

What determines the selectivity of membrane channels?

A

Structure

68
Q

Stimuli: Gated Ion Channels

A
  • Chemical (Ligand): Ligand-gated membrane channels open in response to a chemical stimulus.
  • Mechanical (Pressure): Mechanical-gated membrane channels open in responses to a mechanical/pressure stimulus.
  • Voltage (Membrane Potential): Voltage-gated membrane channels open in response to a change in cell membrane potential.
69
Q

How does VMem impact the conformation of voltage-gated channels with positively charged transmembrane domains?

A
  • The voltage-gated channels opens as the intracellular environment becomes more positive (>VMem).

The positively charged intracellular environment repulses the voltage-gated channel’s positively charged transmembrane domain such that the channel opens to the extracellular environment.

70
Q

ENa+

A

+60 mV

71
Q

EK+

A

–90 mV

72
Q

VMem of Typical Cell

A

–70 mV

73
Q

Which ions are typically more concentrated in the extracellular environment?

A
  • Na+
  • Cl–
  • Ca2+
74
Q

Which ions are typically more concentrated in the intracellular environment?

A
  • K+
75
Q

Graded Potential

A

A localized small deviation from the membrane potential that makes the membrane less/more polarized.

  • Depolarizing Graded Potential: A graded potential that makes the membrane less polarized (i.e. less negatively charged inside).
  • Hyperpolarizing Graded Potential: A graded potential that makes the membrane more polarized (i.e. more negatively charged inside).
76
Q

Hyperpolarization

A
  • Increasing Cell Polarization
  • Decreasing Intracellular Charge
  • Decreasing VMem Value
77
Q

Depolarization

A
  • Decreasing Cell Polarization
  • Increasing Intracellular Charge
  • Increasing VMem Value
78
Q

Stages: Action Potential

A
  1. Depolarization
  2. Repolarization
  3. Hyperpolarization
79
Q

The size of a graded potential is proportional to ____________________.

A

the strength of the stimulus

80
Q

How does a larger stimulus cause a larger graded potential?

A
  • A larger stimulus opens voltage-gated channels for longer.
  • A larger stimulus opens more voltage-gated channels at once.
  • A larger stimulus can re-open voltage-gated channels before the initial graded potential dissipates.
81
Q

Summation

A

A larger graded potential is created through the combined effect of multiple smaller/consecutive graded potentials.

82
Q

The summed activity of many ion channels can change ____________________.

A

the membrane potential (VMem) at the axon hillock.

83
Q

What allows the axon hillock to be the initiation point of action potentials?

A

The axon hillock possesses a high density of voltage-gated Na+ channels, which rapidly open (to cause an action potential) when VMem) is increased to threshold.

Threshold = –55 mV

84
Q

What do the activation gates of voltage-gated Na+ channels respond to?

A

Depolarization

I.e. Voltage-gated Na+ channels rapidly open in response to neuronal depolarization.

85
Q

Voltage-gated Na+ channels in the axon hillock will open if ____________________.

Action Potential

A

the localized region is depolarized to the threshold potential.

Depolarization to threshold potential causes:
1. Depolarization (to threshold potential) at adjacent localized regions.
2. Nearby voltage-gated Na+ channels to open.
3. Depolarization (to threshold potential) at localized regions further from the initial depolarization.
4. The eventualy formation of a complete action potential.

86
Q

How do action potentials demonstrate positive feedback?

A

An initial change in VMem (at one localized region) is continuously amplified (at adjacent localized regions).

I.e. Depolarization (from resting membrane potential to threshold potential) at one localized region leads to massive depolarization at adjacent regions.

87
Q

Why are action potentials described as “all-or-nothing”?

A

Once an action potential is initiated, it will not stop until the axon terminal is reached.

It is not possible to open some voltage-gated Na+ channels (in the axon hillock) to achieve only partial depolarization. (If some voltage-gated Na+ channels open, then adjacent voltage-gated Na+ channels will open to propogate the action potential.)

88
Q

What is the result of rapid opening of voltage-gated Na+ channels in the axon hillock?

Action Potential Initiation

A
  • Increased Membrane Permeability to Na+ Ions.
  • Membrane Potential is Closer to E</sub>Na+</sub>
  • Increased Flow Rate Na+ Ions into Cell
89
Q

Why does V<Mem> stop increasing *well before* ENa+ is reached?</Mem>

Action Potential

A

Voltage-gated Na+ channels inactivate (via the closing of the inactivation gate) shortly after they activate/open.

The rapid inactivation of voltage-gated Na+ channels quickly stops the influx of Na+ ions into the cell.

90
Q

What event does the voltage-gated Na+ channel inactivation gate close in response to?

A

Depolarization

91
Q

When does the voltage-gated Na+ channel inactivation gate reset?

A

The inactivation gates do not reset until the VMem returns to a negative value (i.e. close to the resting membrane potential).

92
Q
A

Human Physiology (5 decks)

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