CTR - 10 - Homeostasis

Question 1

What is a set point?

Answer 1

The desired value of a variable

Question 2

What is a stimulus?

Answer 2

Deviation from a set point

Question 3

What is negative feedback?

Answer 3

To reduce or correct a deviation from the set point (negate the stimulus)

Question 4

Why is there oscillation?

Answer 4

Due to large between receptor and response (slight overcorrections)

Question 5

What happens to oscillations in a more efficient homeostatic system?

Answer 5

Less oscillation (but this requires energy = costly)

Question 6

Homesotasis is concerned with the ______ but changes are often detected ________.

Answer 6

ECF, but changes are often detected in the blood

Question 7

Who said this:
Organ systems create and control composition of the internal milieu, and constantly is required for body cells to operate

Answer 7

Claude Bernard

Question 8

Who said this:

Numerous agents/processes act together to control particular variables

Answer 8

Walter Cannon

Question 9

Gain = ?

Answer 9

correction / error

Question 10

What is the importance of maintaining body temperature?

Answer 10

Enzymatic reaction rates are temperature dependent.

Question 11

T or F? Shell temperature and rectal temperature are accurate representations of core temperature.

Answer 11

Shell = NO
Retal = YES

Question 12

A fever results in ____________

Answer 12

A shift (increase) in the hypothalamic set point (greater than 37 degrees celsius)

Question 13

How do you know when a fever is broken? What does this mean?

Answer 13

Set point returns to normal. Sweating to cool the body back down to regular set point.

Question 14

What temperatures does heat stress occur at? What is another name for heat stress? Symptoms

Answer 14

Heat exhaustion. 37.5 - 39

Elevated core body temp
Mental confusion
Fainting
Dehydration
Headache
Heat loss mechanisms ARE functional

Corrective responses

Question 15

What temperatures does heat stroke occur at? What is another name for heat stress? Symptoms

Answer 15

Hyperpyrexia. Greater than 40

Brain and hypothalamic activity is depressed - thermoregulatory mechanisms work less effectively –> POSITIVE FEEDBACK

Elevated core body temp
Behave/speak inappropriately
Confused
Clammy/dry skin
Not request shade or fluids

Question 16

What is positive feedback? 2 physiological examples

Answer 16

Error in signalling - acceleration into catastrophe.

Blood clotting
Childbirth (oxytcoin)

Question 17

What is the primary excretory organ?

Answer 17

Kidneys

Question 18

What % of blood flow goes to the kidneys?

Answer 18

25%

Question 19

The nephrons filter a total of _____

Answer 19

180 L of blood per day

Question 20

How many nephrons?

Answer 20

2 million (1 million per kidney)

Question 21

How much of the filtered blood is reabsorbed?

Answer 21

99%

Question 22

What is reabsorbed in the PCT?

Answer 22

Glucose, water, Na+, Cl-, amino acids

Question 23

How is glucose reabsorbed in the PCT?

Answer 23

secondary active transport

Question 24

How are amino acids reabsorbed in the PCT?

Answer 24

secondary active transport

Question 25

What is the osmolarity of the medulla?

Answer 25

1200 mOsm

Question 26

How does ADH affect the kidney?

Answer 26

Inserts aquaporins into the collecting duct --> increases water reabsorption

Question 27

What are eryhtrocytes?

Answer 27

Red blood cells

Question 28

How many red blood cells are produced?

Answer 28

2 million per second (and removed)

Question 29

How many haemoglobin molecules per RBC?

Answer 29

300 million

Question 30

What is a hypoxic tissue?

Answer 30

Tissue getting insufficient oxygen

Question 31

What is an anoxic tissue>

Answer 31

Tissue getting NO Oyxgen

Question 32

What is another name for a RBC?

Answer 32

Erythrocyte

Question 33

What does the ________ release to regulate RBC concentration?

Answer 33

Kidney, releases erythropoietin (EPO)

Question 34

What does EPO do (broadly)?

Answer 34

Increases RBC count

Question 35

Where does EPO act?

Answer 35

On red bone barrow - releasing RBC

Question 36

What is acclimatisation?

Answer 36

Change in set point instigated by environmental change

Question 37

Change in set point instigated by environmental change. What is this?

Answer 37

Acclimatisation

Question 38

What happens if there is too little/much calcium?

Answer 38

``` Too little: Heart and muscle contraction Nerve action (APs) Blood coagulation Cell division ``` Too much - precipitates out in blood (with phosphate) forming clots

Question 39

Why is blood glucose regulation important?

Answer 39

``` Too high (diabetes) Too low (decreased CNS activity) ```

Question 40

What are the roles of insulin?

Answer 40

Conversion of glucose to glycogen in liver (if stores filled up, sorted as fat) Uptake of glucose into tissue cells (by binding to receptors, increasing facilitated diffusion of glucose into cells)

Question 41

Stimulus for insulin release?

Answer 41

High blood glucose (amino aids, and fatty acids too)!

Question 42

glucose enters beta cells via ________?

Answer 42

GLUT (glucose transporters)

Question 43

How does glucose affect beta cells?

Answer 43

eneters via GLUT, increases ATP production, causes K+ channels to close, depolarisation, opens Ca2+ channels, insulin released from vesicles via exostosis

Question 44

How is glucose reabsorbed from the kidney (BG)? Structures?

Answer 44

lumen of nephron --> tubular cell - secondary active transport against concentration gradient (with sodium) - via co-transport carrier - facilitated diffusion out of tubular cell to interstitial fluid via glucose carrier

Question 45

What are signs of diabetes mellitus?

Answer 45

Sweet urine | Wake up many times to urinate (osmosis)

Question 46

What is the real threshold?

Answer 46

300 mg / 100 mL | Greater than this, glucose is excreted, as transporters are maxed out.

Question 47

What does diabetes mellitus mean?

Answer 47

Sweet urine

Question 48

Type II accounts for _____

Answer 48

90%

Question 49

Type II accounts for _____

Answer 49

10%

Question 50

What are some consequences of diabetes mellitus?

Answer 50

``` Blindness Amputation of lower limbs Kind failure Impotence Cardiovascular disease Acidosis Metabolic anomalies ```

Question 51

What are the first and second actions of glucagon?

Answer 51

Firstly - glycogenolysis (glucogen --> glucose in liver) Gluconeogenesis - formation of new glucose from fat cells

Question 52

Why is chronic stress diabetogenic?

Answer 52

Chornic stress -> increases cartels levels Which is a stimulus for glucagon release Increases blood glucose --> can lead to diabetes mellitus

Question 53

What is diabetes insipidus?

Answer 53

Inability to concentrate urine | Diuresis can be 3-15 L per day

Question 54

What are the causes of diabetes insipidus?

Answer 54

Neurogenic (insufficient production or release of ADH from posterior pituitary - tumours) Nephrogenic (end stage kidney disease - no receptors for ADH = cannot retain water) Pscyhogenic = vastly increase water intake

Question 55

What is cardiac output?

Answer 55

Volume of blood pumped from heart per minute CO = SV x HR

Question 56

What three factors maintain blood pressure? Structures?

Answer 56

Adequate Cardiac output - heart Sufficient peripheral resistance = smooth muscle in small arteries Adequate blood volume = kidneys

Question 57

Baroreceptors are _______ receptors

Answer 57

Stretch Falling BP = less stretch Rising BP = more stretch

Question 58

Baroreceptors signal the ___________

Answer 58

Sympathetic nervous system

Question 59

What does angiotensin II do?

Answer 59

Vasocontrstion Increase ADH release from post pituitary Increase aldosterone from adrenal cortex