Lecture 3 - Homeostasis and physiological control Flashcards Preview

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Flashcards in Lecture 3 - Homeostasis and physiological control Deck (35):
1

What is homeostasis?

 

The dynamic maintenance of physiological variables within a predictable range

 

2

What is the purpose of homeostasis in short term?

Immediate survival

3

What is the purpose of homeostasis in the medium-long term?

Health and well-being, reproductive capability

4

What are some physiological variables that are important for immediate survival?

 
 

 

 

The hierarchy of importance of physiological variables is such that a variable that is of greater immediate importance may be maintained at the expense of other variables that are of importance in the long term 

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5

What are some physiological variables that are important for medium/long term survival?

 

 

The hierarchy of importance of physiological variables is such that a variable that is of greater immediate importance may be maintained at the expense of other variables that are of importance in the long term 

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6

What is negative feedback ?

 

Negative feedback (also known as reflex arcs)

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 (normalization)

 

When physiological circumstances change, set-points may be changed (e.g. during fever) or over-ridden (such as during exercise)

 

7

What are the types of negative feedback?

 

Neuronal

Endocrine (hormonal)

Local (chemical/physical)

 

 

8

What is feed-forward?

 

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

 

9

What is positive feedback?

 

Change in a variable triggers a response that causes further change in that variable (Note: amplification rather that normalization)

 

10

Where are the neuronal integrating centres for physiological control located?

 

the midbrain and brain-stem

 

11

Parasympathetic neurotransmitter?

Acetylcholine

 

12

Sympathetic neurotransmitter?

 

Noradrenaline

 

13

Common features of endocrine control mechanims?

 

 

 

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14

What are the human endocrine organs?

 

Hypothalamus

Pituitary

Thyroid

Parathyroid

Adrenal cortex and medulla

Pancreas

Ovaries

Testes

 

 

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15

What are the releasing hormones in the hypothalamus?

 

GHRH, CRH, TRH, GnRH

 

16

What are the inhibitory hormones in the hypothalamus?

 

somatostatin, dopamine

 

17

Which hormones are secreted by the anterior pituitary?

 

GH, prolactin, FSH, LH, TSH, ACTH

 

18

Which hormones are released by the posterior pituitary?

 

oxytocin, ADH

 

19

What type of hormone is insulin ?

Polypeptide

 

20

Name some examples of hypothalamic/pituitary hormones that are peptides

 

Peptides:

ADH

Oxytocin

Anti-diuretic hormone

 

 

21

Name some examples of hypothalamic/pituitary hormones that are polypeptides

 

Growth Hormone

 

22

Name some examples of hypothalamic/pituitary hormones that are glycoproteins

 

Luteinizing Hormone

Follicle-stimulating hormone

Thyroid-stimulating hormone

 

23

Which amino acid are Adrenaline and Thyroxine derived from ?

 

Tyrosine

 

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24

What type of hormones are sex hormones?

Steroids

 

25

Where is the receptor location for steroids and thyroid hormones? And what are their mechanism of action and rate of response? 

 

Receptor location: intracellular: cytoplasm or nucleus

Mechanism of action: Alter gene transcription. slow, prolonged response

 

26

Where is the receptor location for peptides, proteins, glycoproteins and catecholamines?

And what are their mechanism and rate of action?

 

Receptor location: plasma membrane

Mechanism of action: second messenger to change enzyme activity. Rapid, often transient response

 

27

How does the control of blood [glucose] work?

 

Glucose absorbed and blood glucose rises -> sensed by pancreatic ß-cells -> compared against physiological set-point for blood [glucose] -> Insulin secreted. Insulin promotes uptake of glucose by tissues -> blood glucose returns to normal 

 

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28

What are anticipation of a meal and anticipation of physical exertion examples of ? and how do they work?

 

They are examples of feed-forward controls.

 

 

 

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29

Example of positive feedback?

 

Childbirth.

 

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30

what is parturition ?

 

the action of giving birth to young; childbirth.

 

31

What is the hierarchy of importance of physiological control??

The hierarchy of importance of physiological variables is such that a variable that is of greater immediate importance may be maintained at the expense of other variables that are of importance in the long term 

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32

Common components of negative feedback reflex arcs ??

Sensors: detect changes in the physiological variable

Afferent pathway: carry signals from sensors to integrating centre

Integrating centre: compare inputs from sensors against physiological set-point and elicit a response

Efferent pathway: carry signals from integrating centre to effectors

Effectors: produce a response that tends to normalise the physiological variable 

33

The Sympathetic and para-sympathetic nervous systems tend to have opposing actions on various bodily functions.

what does this result in ?

This results in a fine- tuning of physiological variables

Examples:

Heart rate
Blood vessel diameter

GI tract motility

Salivary secretion

Sweat gland secretion

Endocrine secretions 

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34

Example of a neuronal negative feedback reflex ??

Control of body temperature 

 

Lightly clad man in room at 20°C. Body temp maintained at 37°C:

System is in steady state

If room temp is lowered further, body temp also begins to drop

However, rapid mechanisms are triggered that help return body temp back to the ‘set- point’ (37°C) 

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35

Local homeostatic responses ??

Negative feedback reflexes operating locally

Sensors, integrating centres and effectors located in the same region or tissue 

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