Lecture 2 Flashcards by Olivia Faulkner

What do unicellular organisms need from the immediate external environment? (X6)

nutrients
solute concentrations
temperature
pH
removal of toxins (waste)
protection of predators

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What do unicellular organisms depend on to provide the conditions to aid their survival?

The immediate external environment

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How do multicellular organisms provide their stable environment?

Specialised cells form tissues/organs/organ systems which are capable of providing a stable internal environment

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Why can multicellular organisms thrive in a wide variety of conditions?

They don’t rely fully on the external environment to provide a stable environment.

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The ECF (internal environment) has to do what to survive?

Stay within specific parameters

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How does the external environment (outside body) affect the cells?

source of nutrients
site for waste disposal
changeable
has pathogens

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What processes does the ECF help with?

nutrient delivery route

- waste disposal route

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What part of the total body water does the ECF make up?

1/3

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What part of the total body water does the intra cellular fluid make up (ICF)?

2/3

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What is the definition of homeostasis?

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

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Canons homeostasis idea 1

In our bodies there are mechanisms that act to maintain constancy (to resist or assists change).

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Canons homeostasis ideas 2

Any tendency toward change automatically meets with factors that resist change

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Canons homeostasis idea 3

There are cooperating mechanisms which act simultaneously or successively to maintain homeostasis

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Canons homeostasis idea 4

Homeostasis does not occur by chance, but is the result of organised self-government

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Specific ECF variables that need to be controlled

Na+
Ca+
glucose
potassium
pH
core body temp

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What is the main ECF cation?

Na+

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What largely determines the ECF fluid volume?

Na+

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What else does the Na+ influence?

Blood pressure

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What is Na important for in terms of nerves and muscle?

Action potential generation

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What is the normal Na+ concentration?

135-145mmol/L

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What is the structural component of teeth and bones?

Ca+

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Is Ca+ involved in nerve function?

Yes

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What is Ca+ essential for?

Coagulation (stopping bleeding)

What helps regulate enzyme function?

Ca+

What is the normal concentration for Ca+?

2.1-2.6mmol/L

What is glucose used for by cells?

To create ATP for energy

What does high glucose levels cause?

Chronic and acute problems

What does low glucose affect?

Brain function

What is the normal fasting glucose concentration (before breakfast)?

3.5-6mmol/L

What is the normal non-fasting glucose concentration?

3.5-8mmol/L

What is the most common ICF cation?

K+

What is the main determinant of the resting brand potential?

K+ especially in excitable tissue (nerve/muscle)

What is the normal K+ concentration?

3.5-5mmol/L

What happens when pH is too low?

Acidosis Nerve/brain function Consciousness

What happens when pH is too high?

Alkalosis Over excitability nerve/muscles Muscle spasms/convulsions

What is the normal pH?

7.35-7.45

What is the optimal core body temp?

37 degrees

What does the best core body temp allow?

Optimal metabolic and physiological functioning

What temp is more variable?

Peripheral temp Arms/legs Oral/armpit Rectal

What does diffusion result from?

The random movement of molecules as a consequence of their thermal energy

Is diffusion fast?

Yes rapid over short distances

What substances don't need a channel to diffuse through a membrane?

- oxygen/carbon dioxide - steroid hormones - anaesthetic agents

What substances need specific channels to travel through the membrane?

- water | - ions

What is Osmosis?

The net movement of water across a membrane, down its own conc gradient (or towards the region with the higher solute conc).

What is osmotic pressure?

The pressure required to just stop osmosis.

How are fluid shifts damaging?

Create pressure that can damage cells

How do fluid shifts occur?

Differences in solute concentration across a membrane

What is osmolarity?

The measure of total number of solute particles per litre solution (regardless of what they are).

What units are used for osmolarity?

- osmol/L | - mosmol/L

What is the osmolarity normally in the ECF and ICF?

275-300mosmol/L

What is tonicity?

The effect a solution has on cell volume

What are the different things the tonicity can be?

- hypertonic - hypotonic - isotonic

What is hypertonic?

The cell shrinks

What is hypotonic?

The cell swells

What is isotonic?

No change in the cell

How is tonality different from osmolarity?

Tonality is influenced by the type of solute particle, particularly whether it can pass across the membrane or not.

What happens if the osmolarity of one compartment changes?

Water will diffuse by osmosis until equilibrium is restored.