Homeostasis • Physiological state of the body• Internal physical and chemical conditions are

maintained within a tolerable range (balance)– Internal temperature, hormone levels, pH, pressure,

concentrations of glucose and other solutes in the blood, water balance (osmoregulation)

Extracellular Fluid• Interstitial fluid – Surrounds fills the spaces

between cells and tissues– Approx 10L– Consists of water, sugars, salts,

FA, AA, coenzymes, hormones, neurotransmitters, waste products

– Regulates flow of chemicals and allows cells to function properly

• Blood plasma– Helps movement of water and

electrolytes throughout the body

– Approx 3L

Internal Environments• Changes in Extracellular

Fluid has negative effects on cellular function

• Body uses organ systems to regulate internal conditions

– Nervous system– Endocrine system – Muscular system – Integumentary system – Excretory system – Reproductive system

Nervous System (Communication) • Brain, spinal cord, peripheral nerves, sensory organs • Receives sensory data from the environment• Informs body of external conditions• Transmits signals throughout the body

Endocrine System (Communication) • Pituitary, thyroid, pancreas, adrenal (glands)• Regulates levels of hormones and other chemicals

Excretory System (Protect the Body)• Kidneys, bladder, urethra, ureters• Rids the body of waste • Maintains clean internal environment

Integumentary System (Protect the Body) • Skin, sweat glands, hair, nails• Maintains a constant body temperature

Immune System (Protect the Body) • White blood cells• Protects/fights infection

Digestive System (Acquire Energy)• Liver• Breaks down amino

acids• Detoxifies harmful

chemicals (alcohol)• Manufactures

important proteins• Stores glucose

Circulatory System (Acquire Energy)• Transports important substances, including food

molecules, oxygen, carbon dioxide, hormones throughout the body

Respiratory System (Acquire Energy)• Exchanges oxygen and

carbon dioxide between the lungs and the atmosphere.

• Oxygen is needed to release energy from food molecules

• Carbon dioxide is a waste gas

Skeletal System (Support and Move Body)• Includes bones,

ligaments, cartilage• Bones protect

organs and are points of attachment for muscles

Muscular System (Support and Move Body)• Provide movement

for the body• 3 types– Skeletal muscle –

move skeleton– Smooth muscle –

organs – Cardiac muscle –

heart

Reproductive System (Produces Next Generation)

• Includes organs that produce and transport sperm and eggs

• Enables female to give birth

Mechanisms used in Homeostasis • Respond to internal

and external conditions

• Feedback systems– Positive/Negative

• Help bring the body back into balance

• Breathing rate, heart rate, internal temperature, blood glucose levels

Negative Feedback• Reduces the output or activity of an organ or system back to its normal range • Include 3 elements1. Sensor

– tissues or organs - detects change

2. Integrator - hypothalamus – control centre – compares conditions from environment with to optimal conditions

in the body – Set points – ranges of values which need to be maintained

3. Effector – returns measured condition back to set point – response – Antagnositc effectors – produce opposite effect of change detected

Positive Feedback Mechanisms• Increases change in

environmental condition• Does not result in

homeostasis • Cause system to become

unstable• “fight or flight” response• reproduction• fever • Positive feedback

mechanisms operate within negative feedback mechanisms

• Allows body to be brought back into balance

Thermoregulation• Internal temperature

regulation• Negative feedback

mechanism• Thermoreceptors

– compare external temp with internal set point

– Found throughout integumentary system

• Trigger responses (2)– Rate of exothermic

reactions in body (metabolism)

– Rate of thermal energy exchange through surface of body

Hypothalamus• Body’s thermostat• Maintains body

temperature• Optimal body

temperature – 35⁰ - 37.8⁰

• Signals from hypothalamus make us aware of our own temperature

• Body temp rises above hypothalamus set point → blood vessels dilate/induce vasodilation/sweating → increase blood flow→ increase thermal energy loss to environment (radiation)→ sweat glands activated → body temp decreases

• Body temp falls below hypothalamus set point → vasoconstriction in skin/ skeletal muscles start shivering→ reduced blood flow→ less thermal energy lost to environment → body temp increases

Mechanism

Mechanisms of Thermal Energy Exchange• Occurs at the surface

where body comes into contact with the external environment

• Exchange of thermal energy occurs through 1 of 4 mechanisms– Conduction– Convection– Radiation– Evaporation

• All of these mechanisms act simultaneously

Thermal Energy• Conduction

– Flow of thermal energy between molecules that are in direct contact

• Convection– Transfer of thermal

energy within a fluid (liquid or gas)

• Radiation– Thermal energy is

transferred electromagnetically

• Evaporation– Absorbs thermal energy

from skin via water/sweat

Homeotherms• Animals that maintain a stable internal

temperature regardless of external conditions• Includes – Poikilotherms– Endotherms – Ectotherms

Poikilotherms• Fish, amphibians, reptiles, and most

invertebrates• Body temperature varies with and often matches

the temperature of the external environment

Endotherms • Warm blooded animals

(mammals, birds)• Homeotherms that use

internal physiological mechanisms (metabolism) to generate thermal energy and maintain body temp

• Remain fully active over a wide range of temperatures

• Need a constant supply of energy

Ectotherms • Cold blooded animals

(reptiles, amphibians, fish)• Homeotherms that use

external sources of energy to absorb thermal energy and regulate body temperature

• Temperature fluctuates with environmental temperature

• Inactive when temp are too low

• Undergo thermal acclimatization– Gradual adjustment to seasonal

temp

Torphor, Hibernation, Estivation • Adaptations to survive

extreme climates by conserving energy

• Torphor – Sleeplike state – Metabolic rate and body

temperature drop in response to daily temp (nocturnal animals, hummingbird)

• Hibernation – State of inactivity over an

extended period of time • Estivation

– Seasonal torphor – environment is hot and water is scarce

Water Balance • Extracellular fluid needs to maintain a constant

volume (~15L) of water and balance of solute within the body

• Mechanism – Osmosis

Osmosis • Water molecules move

from a high concentration to a region of lower concentration across a selectively permeable membrane

• Osmotic pressure – Results from a difference

in water concentration gradient between the two sides of the selectively permeable membrane

• Hyperosmotic• Hypoosmotic • Isoosmotic

• Hyperosmotic– Solution with higher

concentration of solute molecules than water molecules

– Water tends to move to this side

• Hypoosmotic– Solution with lower

concentration of solute molecules than water molecules

– Water tends to move from this solution

• Isoosmotic– Solution with equal solute

and water concentrations on both sides of cellular membrane

Osmotic Environments (Cell)

Osmoregulation • Process of actively

regulating the osmotic pressure of bodily fluids

• Osmole (osmol)– Contributes to osmotic

pressure of solution • Extracellular fluid =

intracellular fluid (isoosmotic)– [solute] remains the

same across cellular membrane

– [water] remains the same across cellular membrane

The Excretory System• Main functions (with the help of osmoregulation)– Concentrate wastes and expel them from the body– Regulate fluids and water within the body

• Organs included– Kidney – Adrenal gland – Ureter– Urinary bladder– Urethra

Removal of Metabolic Waste Waste Origin of Waste Organ of Excretion

Ammonia Breakdown of amino acids in the liver kidneys

Urea Conversion of ammonia in the liver kidneys, skin

Uric Acid Breakdown of purines in food and drink kidneys

Carbon Dioxide Cellular respiration (breakdown of glucose) lungs, intestines, skin

Bile Pigments Breakdown of porphyrin ring (hemoglobin) intestines

Lactic Acid Cellular respiration (breakdown of glucose) kidney

Solid Waste Breakdown of food intestine

Mechanism• Thirst

– Physiological sensation to drink water • Stimuli to Thrist

– Hypertonicity – cellular dehydration is monitored by the hypothalamus via osmoreceptors

• Mechanism – Hypothalamus sends a signal to pituaitry gland to release

ADH (anti-diuretic hormone/vasopressin)– ADH acts on collecting tubules in nephrons making them

more permeable to water– >1% of filtered water is excreted – Reabsorption of water reduces [Na⁺] – Osmoreceptors send signal to hypothalamus stopping

release of ADH

Kidneys

• Removes waste• Balances blood pH• Maintain body’s water

balance• Blood is supplied to

kidney via renal artery • Re-enters circulatory

system via renal vein

Nephrons• Functional unit of

the kidney • (1 000 000 per

kidney)• Regulate water

balance • Conduct excretion • Different sections of

the nephron have specialized functions in formation of urine and conservation of water

Urinary Bladder• Renal pelvis connects the kidney to the ureter

which fills the bladder • Holds ~300mL-400mL of urine before exiting the

urethra

Deamination • Occurs in the liver

– breakdown of protein • Removal of amino

group from amino acid• Creates ammonia NH₃

(toxic to body)• Urea Cycle

– Ammonia reacts with bicarbonate and 2 ATP molecules to form urea

– Transported to kidneys where excretion occurs via blood

Bicarbonate Buffer System (Kidneys) • Maintains pH of blood

(acid-base homeostasis) • Regulates the excretion of

H⁺ ions in the urine and reabsorption of bicarbonate into bloodstream – TOO ACIDIC – hydrogen

ions are excreted – TOO BASIC – less hydrogen

ions are excreted • CO₂ dissolved in blood

reacts with water to form carbonic acid (H₂CO₃)

Formation of Urine • Ultimate goal

– conserve water, balance salts, concentrate wastes

• Urine – hypoosmotic to surrounding body

fluids– water tends to move from urine into

the body fluids • 3 Feature of nephron interact to achieve

ultimate goal– Arrangement of loop of Henle– Difference in permeability – Concentration gradient of molecules

and ions • 3 processes interact to achieve formation

of urine– Filtration – Reabsorption – Secretion

Formation of Urine: Overall Process

Filtration • Begins at Bowman’s capsule

(selectively permeable membrane)

• Receives water, ions, glucose, AA and urea from glomerulus

• Difference of pressure allows for transfer of molecules and ions into capsule

• 1400L of blood pass through kidneys every day

• Bowman’s capsule filters ~180L from blood

• ~1.5L is excreted as urine daily

Reabsorption • Occurs as fluid from Bowman’s

capsule enters proximal convoluted tubule, Loop of Henle and distal convoluted tubule

• Water, ions and nutrients are transferred back into interstitial fluid and peritubular capillaries via passive and active transport

• Microvilli inside tubules increase surface area

• Difference in solute concentration allows water to move across the membrane and back into interstitial fluid via osmosis (aquaporins)

Secretion • Removal of waste products from the

blood and interstitial fluid and secreted into the nephron

• Include – detoxified poisons, water soluble drugs, metabolites, H⁺

• Secretion of H⁺ ions balances acidity in body

• Reabsorption of HCO₃⁻ occurs simultaneously

• Buffer system controls pH levels of blood– Increased acidity – H⁺ excreted as urine

• Urine reaches bottom of collecting ducts, flows into renal pelvis, through ureters, into urinary bladder and exits through urethra

Kidneys Regulate Blood Oxygen Levels

• Kidneys monitor blood oxygen levels (RBC’s)

• If too low – kidneys release erythropoetin (EPO) into the blood stream which stimulates the production of red blood cells

Kidney Diseases • Renal Failure • 2 types1. Acute – rapid progressive loss of

renal function– Injuries, accidents,

complications from surgery

2. Chronic – slow progressive with long

term consequences– Diabetes mellitus,

uncontrolled hypertension, polycystic kidney diseases

• Treatments– Dialysis– Kidney transplant