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HUBS > Lecture 2 > Flashcards

Lecture 2 Flashcards

1
Q

Unicellular organisms depend on the immediate ______ environment to provide conditions conducive to survival.

What is the limit of being unicellular?

What environment conditions unicellular organisms depend on?

A

External

Limits the type of environments which organisms can successfully inhabit because their immediate surroundings must supply the appropriate nutrients and conditions.

  • Nutrients
  • Solute concentration
  • Temperature
  • pH
  • Toxins
  • Predators
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2
Q

Multicellular organisms, cells specialise and then combine to form tissues, organs and organ systems in order to……

The external environment in multicellular organisms is less critical and allows them to……..

The parameters of the internal environment (extracellular fluid) which surrounds individual cells must be………

A

Provide individual cells with a stable environment inside the body.

Thrive in a wide variety of conditions.

Maintained within acceptable limits.

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3
Q

The cells immediate environment:

A

Extracellular Fluid (ECF)

Supplies:

  • Correct temperature
  • and pH
  • Route for nutrient delivery
  • Waster disposal
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4
Q

How much of our body water does the ECF contribute to?

A

1/3 total body water

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5
Q

The intracellular fluid is…..

A

The fluid inside the cell.

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6
Q

How much of our body water does the ICF contribute to?

A

2/3 total body water

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7
Q

What does homeostasis mean?

A

The maintenance of relatively constant conditions in the internal environment (ECF) in the face of external (or internal) change

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8
Q

Maintaining the constancy of the ECF allows multicellular organisms to……

A

Explore and function in a diverse range of environments

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9
Q

What are the four ‘facts’ about homeostasis that define it?

A
  1. Our bodies contain mechanisms that act to maintain constancy.
  2. Any tendency towards change is automatically met with factors that resist change.
  3. There are co-operating mechanisms which act simultaneously or successively to maintain homeostasis.
  4. Homeostasis does not occur by chance, but by the result of organised self-government.
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10
Q

ECF variable that needs to be controlled: SODIUM

A
  • Main extracellular cation
  • Largely determines extracellular fluid
  • Important in action potential generation in nerve and muscle tissue
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11
Q

Normal concentration of sodium in ECF is……

A

135 - 145 mmol/L

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12
Q

ECF variable that needs to be controlled: CALCIUM

A
  • Important structural component of bone and teeth
  • Involved in neurotransmission and muscle contraction
  • Essential for coagulation
  • Regulates enzyme function
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13
Q

Normal total plasma concentration of calcium is……

A

2.2 - 2.6 mmol/L

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14
Q

ECF variable that needs to be controlled: GLUCOSE

A
  • Used by cells (neurons) to produce ATP
    > neutrons particularly affected by low glucose level
  • High blood glucose causes other problems
    > (both acute and chronic)
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15
Q

Normal fasting glucose concentration is….

Normal non-fasting glucose concentration is….

A
  1. 5 - 6 mmol/L

3. 5 - 8 mmol/L

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16
Q

ECF variable that needs to be controlled: POTASSIUM

A
  • Most abundant intracellular cation
  • Main determinant of the resting membrane potential
    > excitable tissue (nerve and muscle)
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17
Q

Normal concentration of potassium in ECF is…….

A

3.5 - 5 mmol/L

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18
Q

The normal pH for a human body is between:

A

7.35 - 7.45

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19
Q

What is acidosis and its effects?

A

When the body’s pH goes below its set point value.

Decreased neuronal function
Decreased levels of consciousness

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20
Q

What is alkalosis and its effects?

A

When the body’s pH goes above its set point value.

Over-excitability of nerve and muscle tissue, leading to pins and needles, muscle spasms, and/or convulsions.

21
Q

The normal core temperature of a human body is:

What does this allow for?

A

36˚C to 37.5˚C

Allows for optimal metallic and physiological functioning.

22
Q

What is peripheral temperature?

A

The places around the body that are likely to have a slightly different temperature to the core temperature.
e.g. ears, oral or rectal areas.

23
Q

Why is core body temperature so important?

A

At higher temperatures
> proteins/enzymes start to denature.

At lower temperatures
> chemical reactions slow down, preventing normal cell function.

Nerve cells cells are particularly sensitive to this effect, as many control centres (for homeostatic functions) and processes underlying consciousness are affected first.
This can lead to escalation of heat loss, starting a ‘vicious cycle’ (a sequence of reciprocal cause and effect in which two or more elements intensify and aggravate each other, leading inexorably to a worsening of the situation), that rapidly becomes lethal.

24
Q

What is diffusion?

A

Diffusion results from the random movement of individual molecules as a consequence of their thermal energy.

It is very rapid and over the short distances within cells and between cells and capillaries.

25
Q

What substances that as a result of simple diffusion, are able to diffuse directly through the lipid bilayer of cells from high to low concentration?

A
  • Oxygen
  • Steroid Hormones
  • Anaesthetic agents
26
Q

Why is diffusion passive (meaning no energy is required)?

A

Because the net direction of movement is from an area of high concentration to low concentration. Such movement is ‘downhill’ and thus no energy from the cell is required.

27
Q

When does simple diffusion via membrane channels occur?

A

When a substance, due to its size or physiochemical properties is not able to ‘dissolve’ through the lipid bilayer and thus needs a channel or carrier protein to allow it to cross.

28
Q

What is the name of the channels water molecules cross through?

A

Aquaporins

29
Q

What are some other ions that need channels?

A

Potassium
Calcium
Sodium

30
Q

Channels are usually specific.
What is the name of those that open and close in response to various stimuli?
What are some examples of these stimuli?

A

Leak Channels.

  • Chemicals (ligand gated channels)
  • Change in membrane potential (voltage gated channels)
31
Q

What is another name for Facilitated Diffusion?

A

Carrier Mediated Passive Transport

32
Q

What is the basic process of Carrier Mediated Passive Transport?
An example?

A

A substance binds to a carrier on one side of the membrane. This induces the carrier to change shape and release the substance to the other side.

Glucose entry into cells when insulin present.

33
Q

Is facilitated diffusion Passive or Active transport?

Why?

A

It is PASSIVE because the molecules or ions move down the concentration gradient.

34
Q

What is active transport?

A

The movement of ions or molecules across a membrane from a region of low concentration to high concentration. This is assisted by enzymes and requires energy.

35
Q

What is primary active transport?

A

When the energy from the hydrolysis of ATP is used to move substances against their concentration gradient.

36
Q

Define Endocytosis and Exocytosis

A

Substances transported into or out of the cell in membranous bilayer vesicles.

37
Q

What is Endocytosis? Give an example.

A

When the cell ‘traps’ some extracellular material and brings it into the cell. The cell’s cytoskeleton pulls part of the plasma membrane inwards, and at the same time pushes the membrane at the edges of the depression so that it forms a vesicle.

Endocytosis of microbes by neutrophils.

38
Q

What are the two subdivisions of Endocytosis?

A

Phagocytosis (cell ‘eating’)

Pinocytosis (cell ‘drinking’).

39
Q

What is Exocytosis? Give an example.

A

The process by which large molecules (notably proteins), can leave the cell after being enclosed in a vesicle by the Golgi apparatus. The vesicle is then pulled by the cytoskeleton to the plasma membrane, with which it fuses and releases its contents.

Exocytosis of insulin by Beta cells of the pancreas

40
Q

Describe Phagocytosis.

A

In phagocytosis, the vesicle will fuse with a lysosome which will continue to release digestive enzymes and digest the particles into their component molecules.
These products may subsequently diffuse through the vesicle’s membranous wall into the cytoplasm.

41
Q

Describe Pinocytosis.

A

Pinocytosis allows fluids and solutes to be brought into the cell and also provides a way for the removal of material, including membrane receptors and transporters from the plasma membrane.
A cell can thus regulate the function of its plasma membrane.

42
Q

What is osmosis?

A

The net movement of water across a membrane from a region of high solute concentration to low solute conc.

Note: Differences in solute concentration across cell membranes can cause fluid shifts and create pressure that can damage cells.

The required to just stop this osmosis is the osmotic pressure.

43
Q

Define osmolarity and units.

A

The measure of the total number of solute particles per litre of solution.
Property of a particular solution (independent of any membrane)

osmol/L or mosmol/L

44
Q

What is the normal osmolarity in the human body in ECF and ICF?

A

275-300 mosmol/L

45
Q

What is tonicity?

HYPERtonic solutions will cause cells to:

HYPOtonic solutions will cause cells to:

ISOtonic solutions will cause cells to:

A

The effect that a solution has on cell volume.
Property of a solution with reference to a membrane.

cells shrink

cells swell

Have no change in cell volume.

46
Q

How does tonicity differ from osmolarity?

A

Tonicity is influenced by the type of solute particles, particularly whether or not they can easily cross the cell membrane.

47
Q

If osmolarity of one of the compartments of the ICF, the ISF or plasma membrane changes then:

A

Water will diffuse by osmosis until equilibrium has been restored.

48
Q

If intravenous distilled water diffused into the plasma membrane, this would cause the water to:

A

Firstly move into the ISF

Then ICF in order to balance out the imbalance until equilibrium has been reached

HUBS (14 decks)

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