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Principles of Physiology and Pharmacology > Physiological Homeostatis > Flashcards

Physiological Homeostatis Flashcards

1
Q

What is homeostasis?

A

‘The dynamic maintenance of physiological variables within a predictable range’

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2
Q

What does dynamic mean?

A

The variable may fluctuate, but still within a ‘normal’ range and the average value will be predictable over longer periods of time

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3
Q

What does the size and frequency of the fluctuation depend on?

A

A given variable

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4
Q

What is the short term purpose of homeostatis?

A

Immediate survival

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5
Q

What is the medium-long term purpose of homeostatis?

A

Health and well-being

Reproductive capability

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6
Q

What is the hierarchy of importance of physiological variables?

A

A variable that is of greater immediate importance may be maintained at the expense of other variables that are important in the long term

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7
Q

What do Homeostatic control mechanisms ensure?

A

That changes in the physiological variables are normalised

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8
Q

What is negative feedback also known as?

A

Reflex arc

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9
Q

What is negative feedback?

A

A change in the variable being regulated is compared against a set-point, causing a response that tends to move the variable back to the set-point

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10
Q

What happens to the set point when physiological circumstances change?

A

Changed (e.g. fever) or over-ridden (e.g. exercise)

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11
Q

What are the types of negative feedback?

A

Neuronal
Endocrine (hormonal)
Local (chemical/ physical)

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12
Q

What is a feed forward mechanism?

A

Anticipation of a change brings about the response to that change before the change can be detected by negative feedback sensors

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13
Q

What is positive feedback?

A

Change in a variable triggers a response that causes further change in that variable (amplification rather than normalisation)

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14
Q

What are the common components of a negative feedback reflex arc?

A 
Sensors
Afferent Pathway
Integrating Centre
Efferent Pathway
Effectors
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15
Q

What do sensors do?

A

They detect changes in the physiological variable

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16
Q

What does the afferent pathway do?

A

Carries signal from the sensors to the integrating centre

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17
Q

What does the integrating centre do?

A

It compares inputs from sensors against physiological set-point and elicit a response

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18
Q

What does the efferent pathway do?

A

Carries signals from integrating centre to effectors

19
Q

What do effectors do?

A

Produces a response that tends to normalise the physiological variable

20
Q

Where are neuronal integrating centres for physiological control located?

A

Mid-brain

Brainstem

21
Q

What is the mid-brain and brainstem comprised of?

A

Hypothalamus
Pons
Medulla

22
Q

What is an example of a parasympathetic neurotransmitter?

A

Acetylcholine

23
Q

What is an example of a sympathetic neurotransmitter?

A

Noradrenaline

24
Q

What are the human endocrine organs?

A

Hypothalamus, Pituitary, thyroid, Adrenal, Pancreas, Ovaries, Testes

25
Q

What are neuroendocrine cells?

A

Cells that receive neuronal input and as a consequence release of hormones

26
Q

What are some examples of inhibitory hormones?

A

Somatostatin

Dopamine

27
Q

What are some examples of releasing hormones?

A

GHRH
CRH
TRH
GnRH

28
Q

What are the times of hormones?

A

Peptides
Polypeptides
Glycopeptides

29
Q

What are some examples of peptide hormones?

A

ADH

Oxytocin

30
Q

What are some examples of polypeptide hormones?

A

Growth Hormone

Insulin (pancreas)

31
Q

What are some examples of glycoprotein hormones?

A

Luteinising hormone
Follicle Stimulating hormone
Thyroid stimulating hormone

32
Q

What are adrenaline and thyroxine (T4) derivatives of?

A

Tyrosine

33
Q

What are some examples of hormones derived from cholesterol?

A

Ovaries:Progesterone, Oestrogen
Testes: Androgen
Adrenal Cortex: Glucocorticoids, Mineralocorticoids

34
Q

What is the receptor location for peptides, proteins, glycoprotein, catecholamines?

A

Plasma membrane

35
Q

What is the mechanism of action for peptides, proteins, glycoprotein, catecholamines?

A

Second messengers

Rapid, transient response

36
Q

What is the receptor location for steroids and thyroid hormones?

A

Cytoplasm

Nucleus

37
Q

What is the mechanism of action for steroids and thyroid hormones?

A

Alter gene transcription

Slow, prolonged response

38
Q

What is a feature of local homeostatic responses?

A

Negative feedback reflexes operating locally, within tissues (does not require brainstem or release of hormones)

39
Q

How is blood flow controlled locally?

A 
Muscles work harder
Increased pO2 and lactic acid (drop in pH)
Sensed by arterioles suppling the muscle
Arterioles dilate
Increasing O2 supply/CO2 removal
40
Q

How is blood volume controlled locally?

A

Increased plasma volume
Macula dense sense increased renal filtration
Juxtaglomerular cells secrete less renin
Less Angiotensin II and Aldosterone
Plasma Volume Falls

41
Q

What usually controls feed forward control mechanisms?

A

Neuronal

42
Q

What happens in anticipation of physical exertion?

A

Anticipation of physical exertion (fight or flight)
Sympathetic Activation
Noradrenaline and Adrenaline Release
Increased Heart Rate and Increased Blood flow in muscles
Preparation for increased demand for O2 and fuel by muscles

43
Q

What usually controls Positive Feedback?

A

Hormones: steroids

44
Q

What are some examples of Positive Feedback?

A

Menstrual Cycle

Parturition

Principles of Physiology and Pharmacology (7 decks)

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