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MD1 - Foundations of Biomedical Science > Folder 1 - Media (22) > Flashcards

Folder 1 - Media (22) Flashcards

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Biology 101 flashcards
1
Q

Why did the amoeba not need complex homeostatic mechanisms?

A

Diffusion was efficient for its size.

The ocean it lived in was stable in temperature and chemical concentration.

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2
Q

Name the three control systems.

A

Cellular
Organ
Body

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3
Q

What is required for cellular level control systems? What happens when operating conditions fall outside tolerable levels?

A

Enzymes and proteins, certain conditions are needed, or it is too inefficient, and wont work.

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4
Q

What type of feedback are control systems?

A

Mostly negative feedback.

Limited positive feedback.

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5
Q

Why are positive feedback mechanisms rare in humans?

A

They have the danger of being an exponential uncontrolled process.

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6
Q

Name the 5 elements of control?

A 
Regulated variable
Sensor
Set point
Comparator
Effector
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7
Q

What is a regulated variable?

A

Variable that will be controlled/maintained.

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8
Q

What is a sensor?

A

The means of measuring the regulated variable.

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9
Q

What is a set point?

A

Value the regulated variable should ideally be.

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10
Q

What is a comparator?

A

Means of comparing the regulated variable with the set point.

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11
Q

What is an effector?

A

Means of returning the regulated variable to the set point.

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12
Q

What is osmolarity and osmolality? Are they the same in humans? Why/Why not?

A

Osmolarity is expressed in kg, while osmolality is expressed in litres.
They are the same thing in humans as 1 litre of water weighs 1kg.

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13
Q

How do stretch receptors work?

A

Stretching changes the diffusion characteristics of the cell, allowing a given ion permeability, and creating a signal.

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14
Q

Do ventricles stretch due to volume or pressure? What about veins, arteries, and atria? What consequence does this have for veins and atria?

A

Ventricles/arteries - stretch due to pressure.

Veins/atria - stretch due to volume. They are therefore also volume receptors.

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15
Q

Name two effector types.

A

Electrical - chemical impulse

Chemical - hormonal

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16
Q

Between electrical and chemical effectors, which is more targetted? What is a consequence of how chemical effectors are delivered to the target? How is specificity achieved here?

A

Hormonal isnt as targetted.
Hormones enter the bloodstream, and the whole body is exposed as a result.
Specificity is achieved using receptors.

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17
Q

Between chemical and electrical effectors, which takes quicker to act?

A

Chemical takes longer as hormones must be made, and time is taken to reach the target (bloodstream).

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18
Q

Name the controlled variable(s) for the following effectors:

  • Heart/blood vessels
  • Muscles, sweat glands, cutaneous circulation
  • Respiratory muscles
  • Renal collecting ducts
  • Liver, muscle, adipose
A
  • Heart/blood vessels - pressure
  • Muscles, sweat glands, cutaneous circulation - shivering, temperature, vasodilation/constriction
  • Respiratory muscles - O2/CO2 levels, pH
  • Renal collecting ducts - K/Na levels, pressure, osmolarity, pH
  • Liver, muscle, adipose - glucose levels
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19
Q

What two organs are the main regulators of pH? How do they integrate into the Henderson-Hasselbalch equation?

A

Lungs and kidneys.

Lungs are represented in the equation by pCO2, and kidney by bicarbonate ion concentration.

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20
Q

What happens if bicarbonate cant be excreted?

A

Blood becomes acidic - acidosis.

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21
Q

What are surrogate variables, and why are they used? Give an example with blood pressure.

A

The body cant always directly measure the regulated variable. The indirect measurement is the surrogate variable. Blood pressure is the surrogate variable of blood flow, which the body cant measure directly.

22
Q

Blood flow receptors dont exist. What is a consequence of this?

A

The body needs measurements on blood flow. It is not the goal to maintain a certain blood pressure, but achieve a certain blood flow. This is done indirectly by regulating blood pressure.

23
Q

Describe what happens to TPR and blood pressure during exercise, and how the body accounts for this.

A

Muscles need more nutrients, so vessels vasodilate. TPR drops, which drops blood pressure.
The drop is detected, so cardiac output is increased to counteract the blood pressure drop, accounting for the TPR drop as well.

24
Q

What is a key indicator of kidney function?

A

Glomerular filtration rate.

25
Q

Can glomerular filtration rate be measured? What surrogate variable is used, if any?

A

Cant be measured directly, as it is a flow.

Surrogate needed - differential concentration/pressure along a nephron tubule.

26
Q

What creates the swings and overshoots/undershoots seen in regulating many variables (like glucose/temperature)?

A

Comparators have a margin of error.

27
Q

Set points can change over time. Name 4 set points with short term changes.

A

Temperature
Circadian rhythm
Blood pressure
Hormone levels

28
Q

What can cause set points to change over time? Give an example with blood pressure.

A

Persistent changes in ambient levels.
A drug can be given for a week, that raises blood pressure. Set point will increase, and baroreceptor activity will match a control despite the high blood pressure.

29
Q

Describe in detail homeostatic clash using cutaneous circulation and body temperature as an example.

A

Occurs often due to exercise. Cutaneous circulation plays a role in blood pressure/TPR, as well as thermoregulation.
When exercising, heavy breathing and sweating drop fluid levels, which drops cardiac output, dropping blood pressure.
The body responds by increasing TPR by restricting cutaneous circulation.
Cutaneous circulation being told to dilate/constrict at the same time.
Blood pressure wins as the brain favours it over higher temperature. Risk of hyperthermia.

30
Q

Blood pressure is regulated by controlling which 3 variables?

A

Heart rate
TPR
Stroke volume

31
Q

Blood pressure is regulated by controlling which 2 variables?

A

Pre/post glomerular tones

Mesangial cell contraction

32
Q

What hormone do mesangial cells respond to?

A

Angiotensin

33
Q

Where are the control centres for set points and comparators found?

A

Hypothalamus

34
Q

In the hypothalamus, what are central and peripheral temperature receptors responsible for? Where are these receptors found?

A

Central - mostly warmth
-Hypothalamus, spinal cord
Peripheral - cold and warmth
-Skin

35
Q

In terms of temperature, what does the skin do?

A

Provides early warning for changes in ambient temperature.

36
Q

What is the core temperature, and name 3 places it can be measured. Which of the 3 is least affected by ambient changes?

A

37*C
Measured sublingual, ear canal, rectal.
Rectal is least affected by ambient chnages.

37
Q

What is the normal variation of core temperature? Which individials is it greater in?

A

36-37.5*C

Greater in very young/very old

38
Q

What is the diurnal and menstrual variation of core temperature?

A

Diurnal - 0.6 higher in the afternoon.

Menstrual - 1 higher post-ovulation.

39
Q

If the body was in a neutral environment at 23*C, will it gain or lose heat? Why/why not?

A

It will lose heat. Heat is generated by metabolism, which isnt 100% efficient.
Heat is gained from the environment, but still a net loss.

40
Q

Name and describe the 4 methods of heat loss.

A

Conduction - lost by touch, moving from vessels, to skin, to air.
Convection - carried away, movement of air.
Radiation - infrared emission.
Evaporation - liquid water to water vapour is endothermic, absorbing heat from the body.

41
Q

Name 7 body responses to high temperature.

A 
No radiation
No conduction
Uses evaporation
Uses cutaneous circulation
Anorexia
Lethargy
Shallow breathing
42
Q

Name 7 body responses to low temperature.

A 
Constricted cutaneous circulation
Shivering
Urge to move
Curling
Hyperphagia
Piloerection
Sympathetically mediated chemical thermogenesis
43
Q

Does the thermoregulatory control centre regulate skin arterioles sympathetically or parasympathetically? What about sweat glands?

A

Both sympathetic.

44
Q

What are 3 consequences of climate adaptation to high temperatures?

A

Sweating occurs sooner
Sweat volume increases
Sweat [Na] decreases

45
Q

What happens to the temperature set point during fever?

A

Increases.

46
Q

What induces a higher temperature set point?

A

Pyrogens

47
Q

Name an exogenous and endogenous pyrogen.

A

Exo - Endotoxin from bacteria

Endo - Cytokines

48
Q

Aside from a shifted temperature set point, what else happens during a fever? What drug can inhibit this?

A

Synthesis of PGE3, inhibited by aspirin.

49
Q

Why do fever chills happen?

A

Heating mechanisms activate as the temperature set point rises - shivering induced.

50
Q

Why do fever crises happen?

A

Cooling mechanisms activate as the temperature set point decreases - sweating induced.

MD1 - Foundations of Biomedical Science (4 decks)

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