Homeostasis and Osmoregulation

Homeostasis

the process of living organisms and systems trying to stay at a set point or set range

Negative feedback

output of a system counteracts the initial change, reverses the change

What does it mean that the body is in dynamic equilibrium?

It is stable, but constantly adjusting

Thermoregulation

Control of body temperature

What is osmoregulation?

Control of water and salt balance in the body

What is a set point?

The target value of a physiological condition maintained by homeostasis

What is a stimulus?

Any change that moves conditions away from the set point

What environments can a stimulus come from?

Internal environment (ex. rising blood sugar) or external environment (ex. cold weather)

What are the 4 parts of a feedback system?

Receptor, Control center, Effector, Response

What does a receptor (sensor) do?

Detects changes in the environment

What is the control center?

The part of the body (usually the brain or an endocrine gland) that receives information and decides what action to take and then sends instructions

What is an effector?

An organ or tissue that carries out the response

What is a response?

The change caused by the effector that moves the body back toward the set point

What are ectotherms?

Animals that rely mainly on environmental heat sources to regulate body temperature

How do ectotherms regulate temperature?

Through behavior (ex. basking in the sun or moving underground)

What are endotherms?

Animals that rely on internal heat production to maintain body temperature

How do endotherms generate heat?

Shivering, increasing metabolism, and burning stored energy

What is shivering?

Involuntary muscle contractions that produce heat

What causes goosebumps?

Arrector pili muscles pulling hairs upright

How does fat help with temperature regulation?

Fat under the skin reduces heat loss

How do both ectoderms and endotherms help regulate temperature internally?

By adjusting blood flow through the circulatory system

What is vasodilation?

Blood vessels widen, more warm blood moves to skin allowing heat to escape to skin

What is the result of vasodilation?

Cooling of body

What is vasoconstriction?

Blood vessels narrow to conserve heat

What is vasoconstriction?

Blood vessels narrow to conserve heat, less blood reaches skin, keeps heat in core organs

What is the hypothalamus in relation to temperature?

The brain’s temperature control center

What does the hypothalamus do during a fever?

Raises the body’d temperature set point

Why is fever helpful?

Higher temperature slows bacteria and boosts immune fuction

What are electrolytes?

Salts that form ions in water (Na+, K+)

What are nonelectrolytes?

Substances that do not form ions (ex. glucose)

Why are electrolytes important?

They control nerve signals, muscle contraction, blood pressure, and fluid movement

What is interstitial fluid?

Fluid between cells similar to blood plasma but with fewer proteins

What is a semipermeable membrane?

A membrane that allows some substances to pass but blocks others

What can move across semipermeable membranes?

Water and some substances

What cannot freely pass semipermeable membranes?

Many solutes (like certain ions)

How does the body gain water?

Drinking and eating

How does the body lose water?

Sweating, urinating, breathing, and feces

Why must osmoregulation constantly occur?

Because the body continuously gains and loses water

What happens if you don’t drink enough water?

The kidneys conserve water and produce concentrated urine to reduce water loss

What happens if you drink too much?

Kidneys remove extra water and urine becomes more diluted

What is the function of the excretory system?

To remove metabolic waste and maintain internal balance

What are the main functions of the kidneys?

Filter blood and regulate water and salt balance

What structures inside kidneys filter blood?

Nephrons

What is a nephron?

The functional filtering unit of the kidney

What is a nephron?

The functional filtering unit of the kidney

What do nephrons produce?

Urine

Where does the urine go after it forms in the kidneys?

It travels through ureters, is stored in the bladder, and exits via the urethra

What is the renal cortex?

The outer kidney layer where blood filtering begins and nephrons are located

What is the renal medulla?

The middle layer of kidney containing tubes that help concentrate urine

What is the renal pelvis?

A funnel-shaped area that collects urine and connects to the ureter (last kidney layer)

What is a ureter?

A tube that carries urine from the kidney to the bladder

What is the urinary bladder?

The organ that stores urine before excretion

What is the blood flow pathway to the kidneys?

Heart → aorta → renal artery → smaller vessels → nephrons

What is the renal artery?

The artery that delivers blood to the kidney

Why do kidneys constantly receive blood?

To continuously filter and clean

How many major steps are involved in nephron filtration?

Three steps: filtration, reabsorption, and secretion

Where does filtration occur in the nephron?

At the glomerulus

What is the glomerulus?

A bundle of tiny capillaries where blood filtration begins

What leaves the blood during filtration?

Water, ions, and wastes

Do useful substances leave the blood during filtration?

Yes, useful substances temporarily leave as well

Where do filtered substances go after leaving the blood?

Into the nephron tubule

What is reabsorption?

The process of returning useful substances from the tubule back into the blood

What substances are reabsorbed?

Most water, needed ions, glucose, and nutrients

Why is reabsorption important?

It prevents loss of useful materials

Does reabsorption require energy?

Some reabsorption uses ATP

What is secretion in the nephron?

The active movement of additional wastes from blood into the tubule

What is the purpose of secretion?

To add more waste to urine

What happens after blood is filtered?

Clean blood leaves the kidney

What is the pathway of cleaned blood leaving the kidney?

Kidney → renal vein → inferior vena cava → heart

What is the renal vein?

The vein that drains filtered blood from the kidney

What becomes urine?

Remaining fluid in the tubules after filtration, reabsorption, and secretion

What does urine contain?

Water, wastes, and excess ions

What do stretch receptors in the bladder do?

Detect fullness

What happens when the bladder becomes full?

Nerves send signals to the brain, creating the urge to urinate

Why doesn’t urine leak out constantly?

Sphincter muscles stay closed

What happens when you decide to urinate?

The brain signals sphincters to relax

What are sphincters?

Muscle rings that control urine release

What is the urethra?

The tube that carries urine from the bladder to the outside of the body

What are blood vessels?

Tubes that transport blood and dissolved substances throughout the body

What do arteries do?

Carry blood away from the heart

What do veins do?

Carry blood toward the heart

What happens when body temperature drops too low?

Blood vessels constrict, sweating stops, and shivering begins

What happens when body temperature rises too high?

Blood vessels dilate and sweat production increases

Where is the body’s temperature “thermostat” located?

The hypothalamus in the brain

What is an example of a solute?

Salt

What is an example of a solvent?

Water

What is an example of a solution?

Salt-water (mixed together)

What is the intracellular compartment?

Fluid inside cells

What is the interstitial compartment?

Fluid between cells

What is blood plasma?

The watery fluid portion circulating in blood vessels

What systems are part of the excretory system?

Urinary system, skin (sweat), and respiratory system

Which sphincter is involuntary?

Internal urethral sphincter

Which sphincter is voluntary and conscious?

External urethral sphincter

What triggers the urge to urinate?

Stretch receptors in the bladder wall sending signals to the brain and spinal cord