Exam 1: Homeostasis Flashcards
What is homeostasis?
Conditions in the body that are maintained at near-constant conditions
Who coined the term “homeostasis” in 1929?
Walter Cannon
Schmidt says when we give anesthesia we do what to the body?
Anesthesia takes a lot of control systems offline; us as CRNAs need to take over the work that the nervous system normally does
What goes ___ must come ___?
In; Out
What is input?
Food
What is output?
Output energy and “waste products”
Energy = work, heat, and potential energy
Waste products = CO2, H+, H2O, Urea, solid waste
What is the internal environment?
Everything under the skin
How many cells does the body have?
35 trillion
How does anatomy relate to physiology?
Form fits function
What is the main homeostasis example? Explain what occurs.
Peripheral circulatory beds
Blood flows into the artery –> arteriole; fluid comes in from the vascular system and delivers nutrients; byproducts are removed through the veins and venules.
T/F. The amount of blood flow depends on the metabolic demands of tissues.
True
T/F If the blood flow picks up in the arteriole end, it will slow down in the venule end.
False. When blood picks up in the artery, it is also picked up in the vein because the metabolic demands have increased and byproducts need to be removed faster d/t the metabolic demands
What are 4 other examples of homeostasis?
Kidneys - maintaining blood pressure, ensuring pH is normal
GI - replacing nutrients in the blood
Lungs - blood gas regulation
2 heart pumps - sharing a wall and making sure we have gas exchange in the lungs and at the peripheral part of the cardiovascular system
What are negative feedback loops?
A major control system in the body that “senses” a positive or negative change in the system and the body reacts and has the opposite effect.
What is an example of a negative feedback loop with inc. CO2?
Inc. CO2 causes increased ventilation which leads to a decrease in CO2
What are 4 examples of a negative feedback loop with dec. MAP?
- Increased sympathetic output
- Decreased parasympathetic output
- Increased AVP/ADH released from pituitary gland
- Decreased ANP
What are positive feedback loops?
A major control system in the body “senses” a change and the body responds by AMPLIFYING this change; can be good or bad and detrimental
What are 2 examples of positive feedback loops?
- When a woman is in labor, the uterus contracts and pushes the baby towards the cervix causing the fetus to stretch the cervix. Oxytocin is released from the brain and causes the smooth muscle to relax and cause more contractions which lead to more stretching of the cervix until the baby is born.
- When a blood vessel gets injured there is going to bleeding. Endothelial cells will expose coagulation factors and promote plt plug formation and activation of the coagulation cascade. This leads to increased coagulation and normally the body would stop this when the bleeding stops. If bleeding doesn’t stop, we can have blocked vessels
If positive feedback loops don’t stop, what can they lead to?
Vicious cycles
Name and explain 4 main examples of vicious positive feedback cycles:
- Sepsis/Necrosis
- widespread infection
-cells dying and things in cells are released and killing other cells - Severe acidosis
- CNS is affected so much that our respiratory drive gets worse and we become more acidotic - Severe hemorrhage
- Dec. in MAP leads to decreased coronary blood flow and decreased CO and even further decrease in MAP - Renal Inflammation/Hyperfiltration
- nephrons die and create a larger workload on the remaining nephrons leading to more death
What is compensated shock?
When negative feedback is working well
What is decompensated shock?
When positive feedback leads back to death and negative feedback is insufficient
How much blood can someone lose and still recover?
20%
