Homeostasis Flashcards
Term homestasis
Is the maintaince of a constant internal environment
Examples of conditions that must be kept constant include
Blood glucose
Core body temp
Blood solute potential
Why is homeostasis important
So that even if cells can function efficiently even if
External conditions fluctuate
The body has different levels of activity
Where does control centre send impulses to
An effector
What is an effector
Muscle or gland
Negative feedback
Is a system that restores conditions to a set point when it detects a deviation. This results in narrow fluctuations around the set point
Positive feedback
A fluctuation which triggers changes that result in an even greater deviations from the normal level
What is set point
A desired value or range of values determined by a coordinator
Describe effectors
Muscles or glands which enable a physical response to a stimulus
Describe receptors
A specialised cells located in dense organs that detect a specific stimulus
Role or coordinator
Coordinates info from the receptors and sends instructions to the effectors
State components of a negative feedback system
Set point
Receptors
Coordinator
Effectors
Mammalian kidney
One of a pair of organs in the abdomen that has a role in osmoregulation and nitrogenous excretion
What is osmoregulation
The regulation of water potential of body fluids (eg blood tissue glue and lymph
By the Kinsey
Define excretion
The process of removing metabolic waster from an organism
Describe how excess amino acids are excreted
Amino acids deaminated in the liver (removal of amino group) to form ammonia
Ammonia is converted to urea less toxic
Urea is transported into the blood plasma and eliminated by the kidneys
Structures of the excretory system
Kidney
Renal vein
Renal artery
Ureter
Urethra
Bladder
Function of renal artery
Supplies oxygen and glucose and has a high concentration of urea
Supplies blood to kidneys
Function of renal vein
Removes carbon dioxide and has a lower concentration of urea
Function of ureter
Transfers urine to the bladder
Function of urethra
Urine is released through the urethra out of body
Renal vein
Drains blood from kidneys
What is nephron
The functional unit of the mammalian kidney
Where are the nephrons found
Part of nephron in medulla other part in cortex
Structures of nephron
Glomerulus
Bowman’s capsule
Proximal convulated tubule
Collecting duct
Affererent arteriole
Efferent arteriole
Loop of Henle
Distal convoluted tubule
Define ultrafiltration
The removal of small molecules, water and ions from the blood in the glomerulus of the kidney at high pressure
Describe process of ultrafiltration
Occurs in bowman’s capsule
High hydrostatic pressure in glomerulus forces small molecules out of capillary against osmotic gradient
Basement membrane acts as a filter. Blood cells and large molecules remain in capillary
Why is there a buildup of pressure in the glomerulus
Affecting arteriole leading into the glomerulus is wider than the efferent arteriole taking blood from the glomerulus
What happens in selective re absorption
Useful molecules from glomerular filtrate are reabsorbed into the blood
Glucose, some water, some ions
Involves membrane transport proteins
Where does selective re absorption occur
Proximal convoluted tubule
How are cells in the proximal convoluted tubule adapted for selective reabsorption
Microvilli provide large surface area
Many mitochondria produce ATP for active transport of glucose
Folded basal membrane provides large surface area
Tight junctions stop reabsorbed materials leaking back into the filtrate
By what mechanism are amino acids and glucose selectively reabsorbed into the blood
Secondary active transport
Uses a co transport mechanism involving Na+
By what mechanism are mineral ions selectively reabsorbed into the blood
Active transport
Mechanism water selectively reabsorbed into blood
Osmosis
How are cultured proteins selectively reabsorbed into blood
Via diffusion
Describe loop of henle
Loop consisting of a descending limb and ascending limb surrounded by blood capillaries
Function of loop of Henle
It creates a low water potential in the medulla enabling re absorption of water
