(SBI4U1) Homeostasis Flashcards
Define homeostasis (3)
The maintenance of a relatively constant internal environment, despite changes in the external environment
Ensures that cells/tissues/organs function within their normal limits
Based on a feedback system
What is homeostasis based on?
Based on a feedback system
What is a stimulus?
A change that is detected
In a feedback mechanism:
What is detected?
Stimulus
In a feedback mechanism:
What comes after the stimulus?
Receptor
In a feedback mechanism:
What comes after receptor?
Integrator
In a feedback mechanism:
What comes after integrator?
Effector
In a feedback mechanism:
What comes after effector?
Response
What are the two types of feedback?
Negative Feedback
Positive Feedback
Which type of feedback is less common?
Positive Feedback
Define negative feedback
The feedback response lessens or diminishes the original stimulus
Give an example of negative feedback
Blood pressure regulation
Body temperature regulation
Define positive feedback
The feedback response increases the original stimulus
Give an example of positive feedback
Child birth
In blood pressure regulation, what is the stimulus?
Change of blood pressure (increase/decrease)
In blood pressure regulation, what is the receptor?
Receptors in the blood vessels
In blood pressure regulation, what is the integrator?
The brain
In blood pressure regulation, what is the effector?
The heart and blood vessels
In blood pressure regulation, what is the response?
Heart rate increases/decreases and blood vessel diameter increases/decreases to make blood pressure a normal level
In child birth, what is the stimulus?
The baby’s head pushing on the uterus opening
In child birth, what is the receptors?
The receptors at the uterus opening
In child birth, what is the integrator?
The hypothalamus
In child birth, what is the effector?
The hormone oxytocin
In child birth, what is the response?
Increase strength of subsequent contractions, helping to push the baby out
What is the functions of the kidney? (2)
Filters blood and removes waste
Controls water balance, pH, and ion concentrations in blood
Each kidney contains ~1 million -_______ that filter the blood, controlling water and ion concentrations
Nephrons
Functioning of the Nephron:
What is the first part of the nephron?
Bowman’s capsule
Functioning of the Nephron:
What is the bed of capillaries found in each Bowman’s capsule known as?
Glomerulus
Functioning of the Nephron:
The blood pressure in the glomerulus forces ______ and small molecules (____, ______, _______/_____ _____) out of the glomerulus and into the Bowman’s Capsule
Plasma Ions Water Glucose Amino acids
Functioning of the Nephron:
What is the fluid in the Bowman’s capsule called?
Filtrate
Functioning of the Nephron:
What is the second part of the nephron called?
Proximal Tubule (PCT)(1st Convoluted Tubule)
Functioning of the Nephron:
What happens in the proximal tubule?
Re-absorption of materials needed by the body
Functioning of the Nephron:
Define re-absorption in the kidney
Movement from nephron to blood
Functioning of the Nephron:
What is re-absorbed in the proximal tubule?
Glucose, amino acids, ions, water
Functioning of the Nephron:
In the proximal tubule, glucose, amino acids, and ions are ________ ___________ back into the blood
Actively transported
Functioning of the Nephron:
What is secreted from blood into the nephron in the proximal tubule?
Toxins from protein digestion
Functioning of the Nephron:
What is the third part of the nephron called?
Loop of Henle
Functioning of the Nephron:
What happens in the Loop of Henle? Why?
Regulates fluid balance in the blood by moving water and ions out of the loop of Henle
Concentrates urine, prevents you peeing out valuable fluids
Functioning of the Nephron:
What happens in the descending limb of the loop of Henle?
Water is passively re-absorbed as the fluid travels down the descending limb (as the fluid around the loop of Henle is hypertonic)
Functioning of the Nephron:
What is the water that is taken out in the descending limb of the loop of Henle used for?
Taken into the blood steam to maintain blood pressure/ion concentrations
Functioning of the Nephron:
At the bottom of the loop of Henle, the ________ becomes very concentrated
Filtrate
Functioning of the Nephron:
Is the ascending limb of the loop of Henle permeable to water?
No
Functioning of the Nephron:
What happens in the ascending limb of the loop of Henle?
As fluid/filtrate travels up the ascending loop of Henle, ions are moved into the fluid surrounding the loop of Henle
Functioning of the Nephron:
What ions are moved in the fluid surrounding the ascending limb of the loop of Henle? Why?
Na and Cl ions
Keeps concentration of solute in the fluid surrounding the loop of Henle higher, draws more water out of the collecting duct which concentrates the urine
Functioning of the Nephron:
What is the fourth part of the nephron?
Distal Tubule (DCT)(2nd convoluted tubule)
Functioning of the Nephron:
What is the function of the distal tubule?
Maintains blood pH and electrolyte balance by reabsorption of ions or secretion of ions
Functioning of the Nephron:
What is the last part of the nephron?
The collecting duct
Functioning of the Nephron:
What is carried to the collecting duct?
Water, ions, and waste products
Functioning of the Nephron:
Why will water move out of the collecting duct?
Water will move out due to the high solute concentration in the surrounding solution to concentrate the urine
Functioning of the Nephron:
Urine is collected and delivered to the ________
Bladder
How the brain control the urine output?
The brain signals the pituitary gland to produce more ADH (Anti-Diuretic Hormone) which allows the collecting duct more permeable to water, and in turns decreases urine production