Homeostasis Flashcards
Homeostasis
Keeping internal conditions stable within limits
Negative Feedback
When an organism does the opposite of a change to bring the organism’s conditions back to normal to maintain equilibrium
Receptors, Control Centers, and Effectors
Receptors: Detect stimuli
Control Centers: Transfer information between different parts of the body
Effector: The muscle and glands that bring out a response
Insulin and Lowering Blood Glucose
Beta cells in the pancreas produce insulin in response to high blood sugar to lower it
Insulin converts glucose into fatty acids for storage, stores glucose as glycogen, and increases respiration
Glucagon and Raising Blood Glucose
Alpha cells in the pancreas produce glucagon in response to low blood sugar to raise it
Glucagon prevents the conversion of glucose into fatty acids for storage, breaks down glycogen into glucose, and decreases respiration
Type 1 VS Type 2 Diabetes
Insulin is not being produced
Pancreas doesn’t respond to insulin
Genetic and environmental factors
Age and diet and genetics
During childhood
During adulthood
No proven cure
Lifestyle modifications such as diet and exercise
Requires insulin injections to regulate blood sugar
Medication and managing lifestyle
Thermoregulation Process
Thermoreceptors in skin detect change in temperature and send signal to hypothalamus, the brain’s thermostat
Hypothalamus interprets the signals and determines whether temperature is rising or falling, and decides if the body cools down or heats up
Thermoregulation Mechanisms when Hot
Sweating: Sweat glands produce sweat that evaporates from the skin thus removing heat through evaporation
Vasodilation: Blood vessels in the skin dilate, which allows for more blood to flow to remove heat
Hairs Relax: Hairs lie flat against the skin, minimizing trapped air and promoting heat loss
Metabolic Rate Decreases: Thyroid gland produces less thyroxin which reduces body’s metabolic activity
Thermoregulation Mechanisms when Cold
Shivering: Muscles contract to generate heat
Vasoconstriction: Blood vessels in the skin constrict which reduces blood flow to minimize heat loss
Hairs Contract: Hairs stand, trapping a layer of insulating air next to the skin (Goosebumps)
Metabolic Rate Increases: Thyroid gland produces more thyroxin which increases body’s metabolic activity
Osmoregulation
The process where the body regulates the solute concentration in its fluid by maintaining balance between water and electrolytes
Excretory Organs
Kidneys: Excrete excess water
Liver: Converts excess amino acids into urea
Lungs: Gets rid of carbon dioxide and water vapor
Sweat Glands: Excretes water, salts, and toxins
Kidney Structure
Blood enters through the renal artery and drained through the renal vein
Surrounded by a tough capsule, outer region is cortex and inner is medulla
Central region is the pelvis which leads to the ureter
Afferent and Efferent Arterioles
Blood arrives to the nephron in the afferent arterioles and delivers to network of capillaries called a glomerulus in a cup shaped structure called Bowman’s Capsule
Blood leaves the glomerulus in the efferent arteriole which is narrower than the afferent arteriole
What Separates Glomerulus and Lumen
Endothelium: 1 cell thick with more gaps than other capillaries
Basement Membrane: Made of network of collagen and glycoprotein
Podocytes: Cells with tiny finger like projections that make up the lining of the Bowman’s capsule that wrap around the blood vessels of the glomerulus
Process of Ultrafiltration
Since the afferent arteriole is much larger than the efferent, it builds up hydrostatic pressure inside the capillaries, forcing fluids to pass from the blood through the fenestrated capillaries in the glomerulus into the Bowman’s Capsule
The liquid then drains through the Bowman’s Capsule to the Proximal Convoluted Tubule
Large molecules like blood cells and proteins can’t pass through the Bowman’s Capsule, therefore have to return to the blood through the efferent arteriole
The liquid that passes through the Bowman’s Capsule is called Glomerular Filtrate, and includes water, salts and amino acids
Conditions for Ultrafiltration
Hydrostatic Pressure due to the difference in diameter between afferent and efferent arteriole
Basement Membrane to restrict the passage of large molecules such as blood cells and proteins
Selective Reabsorption
The Proximal Convoluted Tubule is the longest part of the nephron, and over 80% of the filtrate is reabsorbed into the tissue fluid and then to the blood thus leaving the kidney
Structure of the Cells of the Tubules Adapted for Reabsorption
Microvilli: Increase the surface area of the inner surface
Pumps: Actively transport glucose and amino acids against their concentration gradient
Mitochondria: Provides ATP needed for Selective Reabsorption
Differences in Blood Concentrations between Renal Artery and Vein
Wastes: High in artery and low in vein as it’s excreted in urine
Oxygen: High in artery and low in vein as it’s used in cell respiration by kidney tissue
Glucose: High in artery and low in vein as it’s used in cell respiration by kidney tissue
Drugs / Toxins: High in artery and low in vein as it’s excreted in urine
Carbon Dioxide: Low in artery and high in vein as it’s produced by cell respiration and excretion of kidney cells
Ions: Vary in both as it depends on amount of water reabsorbed in the collecting duct in response to ADH
Loop of Henle
Has an ascending and descending limb
Ascending limb transports NaCl by diffusion and active transport out of the loop into the tissue fluid which increases solute concentration in tissue fluid and decreases solute concentration of the fluid in ascending limb itself
Descending limb has water move into the tissue fluid by osmosis, and NaCl diffuse from the tissue fluid into the loop
Fluid becomes more concentrated at the bottom of the loop, and animals that need to conserve water have very long loops of Henle to allow for more water to be reabsorbed
Collecting Duct
After loop of Henle, the fluid moves to the collecting duct where the high solute concentration establishes an osmotic gradient. Water in the filtrate can passively diffuse out into the blood thus making the urine more concentrated
The water leaves through aquaporins which are controlled by ADH, which allows for the amount of water in urine to be controlled
Components of Urine of a Healthy Person
Salts
Water
Uric Acids
Urea
If Urine Contains ___?
Glucose, diabetes
Proteins, kidney disease or damage
Blood Cells, bacterial infection
Response to Thirst
Osmoreceptor cells in the hypothalamus detect the high osmolarity in the blood plasma and produce ADH, which gets released from the posterior pituitary
The ADH binds to receptors in the plasma membrane of cells in the collecting ducts which causes the cell to transport vesicles containing aquaporins towards the membrane and fuse with it, thus inserting aquaporins into the membrane
With more aquaporins embedded, more aquaporin channels open and increases the amount of water to passively diffuse by osmosis into the medulla, which produces small columns of concentrated urine
Response to Hydrated
ADH levels decrease, thus the walls of the collecting ducts allow less water to pass into the blood thus less water is conserved by the body, which produces dilute urine
Importance of Osmoregulation in Animals
If water uptake is excessive, hydrostatic pressure can stretch the plasma membrane to the point of bursting
If water loss is excessive, the cell will shrink and die as water is an essential for the cell’s cytoplasm
Factors that Affect Volume and Concentration of Urine
Water intake
Temperature
Sugar or Salt Intake
Environmental Conditions
Degree / Amount of Exercise
Skeletal Muscles in Sleep, Vigorous Exercise, and Wakeful Rest
Sleep: Low due to inactivity
Vigorous Exercise: High to meet the increased demand for oxygen and nutrients required for muscle contraction
Wakeful Rest: Moderate, reflecting lower activity level compared to exercise
Gut in Sleep, Vigorous Exercise, and Wakeful Rest
Sleep: Low as body’s metabolic activity decreases
Vigorous Exercise: Low as blood is redirected to other vital organs involved in exercise
Wakeful Rest: Moderate to support ongoing digestive processes and nutrient absorption from food intake
Brain in Sleep, Vigorous Exercise, and Wakeful Rest
Sleep: High to support essential functions such as memory
Vigorous Exercise: High to meet the high metabolic demands and maintain cognitive function and coordination
Wakeful Rest: High to sustain cognitive function and consciousness while the body is awake and alert
Kidney in Sleep, Vigorous Exercise, and Wakeful Rest
Sleep: Moderate to maintain renal function
Vigorous Exercise: Moderate and decreased slightly as blood is redirected to active tissues
Wakeful Rest: Moderate to ensure filtration and regulation of blood composition
