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Physio 2 exam 3 > Homeostasis > Flashcards

Flashcards in Homeostasis Deck (28):
1

4 things homeostasis imbalance can result from:

Aging
Genetic mutations
Pathogens
Environment

2

Definition of homeostasis

The ability of an organism to maintain its internal environment despite change to its internal and external environment

3

5 sensory receptors in external environment:

Mechanoreceptors
Thermoreceptors
Electromagnetic receptors
Nociceptors
Chemoreceptors

4

Internal environment

Helps efficient cell/organ/system function

5

What's included in the internal environment?

EC fluid, IF, intravascular fluid

6

T/F internal environment is controlled within a narrow range:

T

7

What does the internal environment detect?

Level of chemicals in blood/tissues

8

Examples of chemicals in blood/tissues:

Glucose, O2, CO2, H2O, ions

9

What is the stimulus to response pathway?

Stimulus --> receptor --> control center --> effector --> response

10

Can the stimulus to receptor response be nervous system or endocrine?

Both!

11

Characteristics of nervous system response:

APs, transported by neurons, fast, short, voluntary/involuntary, local

12

Characteristics of endocrine response:

Hormones, transport by blood, slow, short or long, always involuntary, distant, many cells effected

13

Definition of neurohormones:

Chemicals released by neurons into blood for action at a distant target organ / tissue

14

Example of neurohormone pathway:

1 hypothalamic neurons make oxytocin/ADH
2 oxy/ADH transported down axons of hypothalamus (hypophyseal tract) to PP
3 stored in PP
4 hypothalamic neurons fire, AP arrives at terminals
5 oxy/ADH released into blood

15

Autocrine:

Acts on same cell

16

Paracrine

Acts on adjacent cell

17

Characteristics of lipid-soluble hormones:

Lipophilic
Ex: steroids, calcitriol
DO transport proteins
Long plasma half life
Intracellular receptors
Mediator: receptor-hormone complex

18

Characteristics of water soluble hormones:

Hydrophilic
Ex: polypeptides, glycoproteins, catecholemines
DONT transport proteins
Short plasma 1/2 life
Uses plasma membrane receptors
Mediators: cAMP, cGMP, Ca, kinase cascades

19

Hormone response model:

Receptor --> integrator (brain) --> effector (muscle/gland) --> response ---> feedback

20

Negative feedback definition:

Body senses change = stimulation = feeds back to reverse the change. MOST COMMON kind of feedback

21

Ex of negative feedback

Body temp changing, negative feedback brings it back to homeostasis

22

Mechanism of negative feedback:

Stimulus that homeostasis is not in balance --> integration of signal at hypothalamus (TRH) --> AP releases TSH (effector) --> thyroid gland releases hormones into blood --> NEGATIVE FEEDBACK and homeostasis restored

23

Definition of positive feedback:

Self-amplifying physiological change that leads to even greater change and builds off of itself. Can be detrimental unless corrected by cessation. LEAST COMMON kind of feedback

24

Ex of positive feedback

Parturition

25

Mechanism of parturition as an example of positive feedback:

Stretch receptors in uterus --> signal to brain to release oxytocin into blood --> POSITIVE feedback to uterus to contract more forcefully -->cycle keeps going until cessation

26

Moderate homeostatic imbalance:

Disorder/abnormality of structure/function disease with specific signs / symptoms, signs and symptoms are subjective (ex fever)

27

Severe homeostatic imbalance:

Results in death

28

How is heart failure an example of both negative and positive feedback?

System tries to correct imbalance = negative feedback, but then becomes overwhelmed and destructive positive feedback takes over