Gas exchange and homeostasis

upcoming biology test

gas exchange surfaces must be…

• permeable

• thin

• moist

• large surface area

alveoli

• the sight of gas exchange in the lungs

• small branching chambers that increase surface area

• have extensive capillary beds

Alveolar epithelium cells have two types

• Type 1 Pneumocytes- very thin to facilitate gas exchange

• Type 2 Pneumocytes- secrete fluid for gas exchange and surfactant to prevent collapse due to cohesion of water

ventilation

• a concentration gradient of gases must be maintained by moving air in and out of the lungs

airways

• Trachea branches into two large tubes (bronchi)

• Bronchi branch into little bronchioles

• bronchioles go to little alveoli

can you name:

• the arteriole and venule blood flow directions

• Type 1 and 2 Alveolar epithelium cells

• where o2 and co2 enter and exit

• capilaries

inspiration (breathing in)

• diaphragm contracts

• external intercostal muscles contract pulling the rib cage up and outwards

• internal intercostal muscles relax and are pulled back into their elongated state

• all of these movements increase volume and decrease pressure think a syringe

Expiration (exhale)

• the diaphragm relaxes

• ab muscles contract

• internal intercostal muscles contract pulling ribcage in and down

• external intercostal muscles relax and are pulled back into their elongated state

antagonistic pair

• work in pairs to preform related but opposite movements (intercostal muscles)

hemologbin

• oxygen binding protein in red blood cells

• composed of 4 polypeptide chains each with an iron containing heme group that reversibly binds oxygen

prosethetic group

• non protein molecule that is tightly bound to a protein and helps it function

• and example of this is the heme group

as each O2 binds…

• it alters the confirmation (shape) of hemoglobin (very slight change)

• the altered confirmation makes subsequent binding easier this is called cooperative binding (this means hemoglobin has a higher affinity for O2 in oxygen rich areas like the lungs )

• this results in sigmoid curve

oxygen loading

• is promoted in oxygen starved areas like muscles

• where hemoglobin has a lower affinity for O2

fetal arteries have a lower pressure hence hemoglobin….

must have a higher affinity at lower pressures

myoglobin

• oxygen bonding molecule found in skeletal muscles

• not capable of cooperative (therefore not a sigmoid curve)

• holds onto O2 longer than hemoglobin

• slows the onset of anaerobic respiration

CO2 in the picture

• tissue with high metabolic rate release more CO2

• hemoglobin has an allosteric site for CO2

• when co2 binds hemoglobin changes it shape thus the O2 affinity is lowered

• red blood cells release O2 in the presence of CO2

• muscle cells have high metabolic activity means more co2 and Bhor shift

6.4 homeostasis

kidney plays a role in

osmoregulation and excretion in humans

Osmoregulation

• maintenance of internal solute concentration (water and solute concentration)

• regulation of osmotic concentration

• units= osmoles per liter (OsmolL-1)

excretion

• removal of waste

Renal artery

brings blood to the kidney

renal vein

carries blood away from the kidney

where does filtration occur?

the nephrons

• about 1 million per kidney

• functional unit of the kidney

• only the plasma is filtered through the kidneys

ultrafiltration

• occurs in the glomerulus

• blood flowing in the capillaries of the glomerulus is under very high pressure

• the glomerulus has fenestrated capillaries which allows fluid (non-blood cells) no escape

filtrate

• is the fluid forced through the capillary walls

• anything that goes through the three barriers of the glomerulus becomes a part of the glomerular filtrate

after the glomerulus, filtration flows through….

• the proximal convoluted tubule

• the PCT selectively reabsorbs glucose, amino acids, and salts by active transport (microvilli increases its surface area)

the loop of Henle

• allows the reabsorption of water

• starts in the cortex of the kidney then dips down into the medulla (medulla must be hypertonic)

what allows a high solute concentration in the ascending part of the loop of Henle?

the active pumping of salts

the water that is reabsorbed in the loop does one of two things…..

• the water from the loop is reabsorbed back into the blood

• water that stays in the loop becomes urine

DIstal convoluted tubule

• ions are exchanged (more active transport)

• there is less absorption than the PCT due to no microvilli being present

Finally the filtration enters….

• the collecting duct for final water adjustments

• the collecting ducts permeability to water varies

• the hormone ADH controls this permeability

ADH

• promotes the formation of aquaporins in the walls of the collecting duct

• the aquaporins are membrane channels that are permeable to water

if ADH is present…

more water is reabsorbed into the blood creating a small volume of concentrated urine

if ADH is not present …..

a large volume of urine is produced

Finished urine

• leaves the kidneys through the ureters

• stored in the bladder

• and exits the body through the urethra

Homeostasis

• maintenance of the internal environment of an organism, variables are kept within preset limits, despite fluctuations in the external environment

• an example of this is Osmoregulation and blood sugar regulation

the inner workings of homeostasis are

• control centers receive inputs from receptors and generate outputs to send to effectors

homeostasis relies on

• a negative feedback cycle to maintain set conditions

• the feedback loop reduces the effects of change and helps maintain balance

Blood Sugar regulation

• two hormones regulate blood glucose levels (insulin and glucagon)

• glucose is regulated by building up or breaking down glycogen

Alpha cells

• synthesize and secrete glucagon when glucose levels in the blood are too low

• glycogen is hydrolyzed to glucose in the liver and released into the bloodstream

• blood sugar rises as a result

Beta cells

• synthesize and secrete insulin when glucose levels in the blood are too high

• stimulated uptake of gluecose by skeletal muscle and liver tissues

• stimulates formation of glycogen from gluecose in the liver

type 2 diabetes (late onset)

• deficiency in glucose receptors or glucose transporters on target cells

• the body may not produce or respond to insulin

• the cause in unknown but is associated with sugary, fatty diets, prolonged obesity, lack of exercise and genetic factors

Treatments

• diet must be adjusted to avoid “peaks and throughs” in blood glucose levels

• small frequent meals with low sugar content

• exercise increases insulin uptake and action

Thermoregulation

• peripheral thermoreceptors detect temperature changes and send signals to the brain

• the brain initiates several different reponses

Potential responses for thermoregulation

• shivers- small muscle twitches generate warmth

• vasodilation/ vasoconstriction- increased blood flow for heat retention (heat lost through the skin)

• sweating for cooling

• goosebumps for warmth (rising hair traps)

Brown adipose tissue

• specialized “fat cells”

• more in infants but also found in adults

• metabolized for heat production

• uncoupled respiration- where energy produced by respiration is dissipated instead of being used to perform work

Thyroxin

• regulates metabolic rate and therefore body temperature; secreted by thyroid gland

osmoregulation

• the maintenance of constant osmotic pressure in the fluids of an organism by the control of water and salt concentrations

Osmo regulators

• maintain a constant internal solute concentration

• ex: most terrestrial animals, freshwater animals and some marine organisms

Osmo conformers

• tend to have internal solute concentrations that are isotonic to their external environment

• (many marine invertebrates)