Physiological Homeostatis

Question 1

What is homeostasis?

Answer 1

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

Question 2

What does dynamic mean?

Answer 2

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

Question 3

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

Answer 3

A given variable

Question 4

What is the short term purpose of homeostatis?

Answer 4

Immediate survival

Question 5

What is the medium-long term purpose of homeostatis?

Answer 5

Health and well-being

Reproductive capability

Question 6

What is the hierarchy of importance of physiological variables?

Answer 6

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

Question 7

What do Homeostatic control mechanisms ensure?

Answer 7

That changes in the physiological variables are normalised

Question 8

What is negative feedback also known as?

Answer 8

Reflex arc

Question 9

What is negative feedback?

Answer 9

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

Question 10

What happens to the set point when physiological circumstances change?

Answer 10

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

Question 11

What are the types of negative feedback?

Answer 11

Neuronal
Endocrine (hormonal)
Local (chemical/ physical)

Question 12

What is a feed forward mechanism?

Answer 12

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

Question 13

What is positive feedback?

Answer 13

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

Question 14

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

Answer 14

Sensors
Afferent Pathway
Integrating Centre
Efferent Pathway
Effectors

Question 15

What do sensors do?

Answer 15

They detect changes in the physiological variable

Question 16

What does the afferent pathway do?

Answer 16

Carries signal from the sensors to the integrating centre

Question 17

What does the integrating centre do?

Answer 17

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

Question 18

What does the efferent pathway do?

Answer 18

Carries signals from integrating centre to effectors

Question 19

What do effectors do?

Answer 19

Produces a response that tends to normalise the physiological variable

Question 20

Where are neuronal integrating centres for physiological control located?

Answer 20

Mid-brain

Brainstem

Question 21

What is the mid-brain and brainstem comprised of?

Answer 21

Hypothalamus
Pons
Medulla

Question 22

What is an example of a parasympathetic neurotransmitter?

Answer 22

Acetylcholine

Question 23

What is an example of a sympathetic neurotransmitter?

Answer 23

Noradrenaline

Question 24

What are the human endocrine organs?

Answer 24

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

Question 25

What are neuroendocrine cells?

Answer 25

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

Question 26

What are some examples of inhibitory hormones?

Answer 26

Somatostatin | Dopamine

Question 27

What are some examples of releasing hormones?

Answer 27

GHRH CRH TRH GnRH

Question 28

What are the times of hormones?

Answer 28

Peptides Polypeptides Glycopeptides

Question 29

What are some examples of peptide hormones?

Answer 29

ADH | Oxytocin

Question 30

What are some examples of polypeptide hormones?

Answer 30

Growth Hormone | Insulin (pancreas)

Question 31

What are some examples of glycoprotein hormones?

Answer 31

Luteinising hormone Follicle Stimulating hormone Thyroid stimulating hormone

Question 32

What are adrenaline and thyroxine (T4) derivatives of?

Answer 32

Tyrosine

Question 33

What are some examples of hormones derived from cholesterol?

Answer 33

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

Question 34

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

Answer 34

Plasma membrane

Question 35

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

Answer 35

Second messengers | Rapid, transient response

Question 36

What is the receptor location for steroids and thyroid hormones?

Answer 36

Cytoplasm | Nucleus

Question 37

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

Answer 37

Alter gene transcription | Slow, prolonged response

Question 38

What is a feature of local homeostatic responses?

Answer 38

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

Question 39

How is blood flow controlled locally?

Answer 39

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

Question 40

How is blood volume controlled locally?

Answer 40

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

Question 41

What usually controls feed forward control mechanisms?

Answer 41

Neuronal

Question 42

What happens in anticipation of physical exertion?

Answer 42

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

Question 43

What usually controls Positive Feedback?

Answer 43

Hormones: steroids

Question 44

What are some examples of Positive Feedback?

Answer 44

Menstrual Cycle | Parturition