Homeostasis

Question 1

Definition

Answer 1

the relative constancy of the body = the maintenance of constant conditions in the body’s environment

COMPENSATION
the return to homeostasis after being challenged

DECOMPENSATION
the failure to compensate, adapt, heal

Question 2

Automatic Nervous system

Answer 2

• primary function
• involuntary control
• collaboration between ANS and endocrine system

Not subject to voluntary control, innervates smooth muscle, cardiac muscle and glands, two nerve fibres connected by a synapse.

Stimulates or inhibits a target cell and regulates the internal environment.

Question 3

Positive and Negative feedback

Answer 3

1) Positive Feedback
oxytocin during parturition triggering contractions.
Digestion of proteins; AAs sensed, CCK produced, proteins broken down to produce more AAs so more CCK then produced.

2) Negative Feedback
Temperature control, water balance, pH of the blood.

Question 4

Homeostasis and Temperature

Answer 4

Normal BT -> BT rises above normal -> Nervous system signals dermal blood vessels to dilate and sweat glands to secrete -> Body heat is lost to its surroundings -> BT drops toward normal.

Normal BT -> BT drops below normal -> Nervous system signals dermal blood vessels to constrict and sweat glands to remain inactive -> Body heat is conserved -> BT drops toward normal.
+ if BT continues to drop, nervous system signals muscles to contract involuntary -> muscle activity generates body heat.

Question 5

Homeostasis and water

Answer 5

Some stimulus disrupts homeostasis by increasing osmolarity of plasma and interstitial fluid (arterial baroreceptors -> cardiac out put).
Receptors = Osmoreceptors in hypothalamus (thirst).
Control Center = Salivary gland and stickier saliva.
Effectors = principal cells become more permeable to water, which increase facultative water absorption.
-> Decrease in plasma osmolarity.
-> Return to homeostasis when responses brings plasma osmolarity back to normal.

Question 6

Homeostasis and calcium

Answer 6

STIMULUS = rising blood Ca2+ level (imbalance)
-> Thyroid gland releases calcitonin -> stimulates Ca2+ deposition in bones and reduces Ca2+ uptake in kidneys -> normal blood calcium level = HOMEOSTASIS

STIMULUS = falling blood Ca2+ level -> Parathyroid glands release parathyroid hormone -> increases Ca2+ uptake in intestines, increases Ca2+ uptake in kidneys, stimulates Ca2+ release from bones -> normal blood calcium level = HOMEOSTASIS

Question 7

Homeostasis and protein misfolding

Answer 7

Misfolding of disease-causing proteins results in the disruption of protein homeostasis when misfolded monomers accumulate and begin to form intermediate soluble oligomers or fibrils, and eventually form mature insoluble aggregates:

• Chaperone proteins assist in the correct folding of proteins and prevent the formation of toxic oligomeric species.
• Increasing the expression of chaperone proteins enhances the ability of cells to maintain protein homeostasis even in the presence of aggregation-prone proteins