Test 4 Flashcards
Homeostasis
- maintaining an internal cellular environment that is conducive to cellular function
- exchanging with the environment
2 Approaches to Homeostasis/Exchanging with the environment
- direct
- indirecr
Direct exchange with the environment
- cell uses diffusion/osmosis/carrier mediated transport to exchange with environment
- requires the cell to be close to environment (near body surfaces)
- usually small or have a large surface area
- porifera, platyhelminth, cnidaria
Indirect exchange with the environment
- involves some mechanism for circulating stuff around body
- 2 approaches
What are the two approaches to indirect exchange with environment?
- coelomic circulation
- circulatory system
Coelomic circulation
- use of coelomic fluid to distribute stuff within the body
- negative is that there is no control
- nematodes and echinodermata
Circulatory system
- hearts, vessels, blood
- more control
- 2 approaches
What are the two approaches to a circulatory system?
- open
- closed
Open circulatory system
- fluid leaves the system
- fluid goes into heart through ostia, but cannot leave through ostia
- circulating the coelomic fluid
- arthropoda and mollusca
- direction speed and control (heart rate and which artery)
Artery
- blood vessel that carries oxygenated blood away from the heart to the body’s tissues and organs
Ostia
Small one-way openings in the heart that allow coelomic fluid to enter the heart
Closed circulatory system
- fluid/blood never leaves system unless damaged
- more control
Explain how a closed circulatory system works
- heart pumps oxygenated blood into arteries, creates a high blood pressure/hydrostatic pressure, and arteries carrie blood away from heart
- Arteries branch into arterioles that contain circular smooth muscles
- arterioles lead the blood into the capillary beds, which allows for exchange of gas, nutrients, and waste
- the deoxygenated blood then goes through the venules
- blood then goes through veins and back to the heart
What do the smooth circular muscles do within the arterioles?
- allows the arteriole to constrict or dilate
What is the function of arterioles?
- regulate blood pressure and controls blood flow
What is the function of venules?
- collects deoxygenated blood from capillary beds and transports it to larger veins
Capillaries
- sit of exchange
- small and dense
- near well vascularized tissue
- thin celled; lined with simple squamous epithelia
Vein function
- carries deoxygenated blood back to the heart
What direction does blood flow?
- from high pressure to low pressure
Which has a higher blood pressure: arteries or veins?
- arteries
- arteries are closed to heart, so strong hydrostatic force
Where does water and dissolved molecules move out of blood at?
- in the capillary bed closest to artery through hydrostatic force
Where does water and dissolved molecules move into blood at?
- in the capillary bed closest to vein through osmosis
- blood is hypertonic to fluid in tissues
What are the two forces acting on blood/water?
- hydrostatic force
- osmosis
Hydrostatic force vs blood/water
- from the heart
- pushes water and dissolved molec out of blood
Osmosis vs blood/water
- blood is hypertonic to fluid in tissues
- pulls water from tissues into blood
Hydrostatic pressure vs volume
- as blood volume decreases, hydrostatic pressure decreases
Osmosis vs colume
- osmosis increases as volume decreases
Capillary bed and water movement
- as blood enters capillary bed, water is pulled out
- as blood leaves capillary bed, water is drawn in
Why is blood pressure higher in arteries than veins?
- veins are larger, so less volume in larger area = lower pressure
- veins are elastic
- not all water is recovered
What is the secondary mechanism for pumping blood through veins?
- peristaltic pump
Peristaltic pump function
- moves fluids using a series of contractions/compressions and relaxations
Peristaltic pump process
- vein is surrounded by muscles
- vein contains unidirectional valve
- muscle contraction/movement squeezes vein and forces blood to move upward
- when muscle rests, blood cannot flow backwards because the valves shut
Double circuit circulation
- involves two circuits:
1. pulmonary circuit
2. systematic circuit - blood passes through the heart twice per circuit
- ensures that oxygenated blood is pumped to the body tissues at high pressures
Pulmonary circuit
- deoxygenated blood is pumped from the right atrium to the right ventricle (or ventricle if 3 chambered) then to the pulmonary artery
- once in pulmonary artery it goes through the pulmonary capillary beds where it picks up oxygen and released co2
- returns to the heart through pulmonary veins
Systematic circuit
- oxygenated blood is pumped from the left atrium to the left ventricle (or ventricle if 3 chambered) then to the aorta
- blood moves from aorta to the systemic capillary where it delivers the oxygen to the body tissues
- the now deoxygenated blood goes through the vena cava back to the heart
What are the two versions of double circuit circulation?
- 3 chambered
- 4 chambered
3 chambered heart
- one ventricle
- some fish and reptiles
- amphibians
- delivers moderately oxygenated blood to tissues
- ectothermic
4 chambered heart
- 2 ventricles
- some reptiles
- birds
- mammals
- delivers fully oxygenated blood to tissue
- requires a lot of energy
- endothermic
Ectothermic
- organism uses the environment to regulate temperature
Endothermic
- organism uses metabolism to regulate temperature
Lymphatic System
- system of glands (lymph nodes), ducts, and lacteals
functions: - returns excess fluid from capillary bed to circulatory system
- defense against bacteria and infections
- transports fats from digestive system to the liver
What is known as the supplemental circulatory system?
the lymphatic system
Lymph nodes function
- filters lymph fluid and fights off bacteria and viruses with its storage of white blood cells
Lymph ducts function
- return filtered lymph fluid back into the blood stream to help regulate fluid levels and support immune function
- carries lymph to the heart
Lacteal function
- absorbs lipids from the intestine and helps transport them into the bloodstream
How does lymph go back into the bloodstream?
the lymph is dumped into the large veins near the heart and circulates the body again
Simple Process of the Lymphatic System
- fluid leaks out of blood capillaries into surrounding tissues and become interstitial fluid
- lymphatic capillaries absorb the fluid, and it is now called lymph; in the small intestine, lacteals absorb fats
- lymph moves through larger lymphatic vessels
- lymph nodes filter the lymph and fight against bacteria and viruses with white blood cells
- lymph ducts carry lymph to the veins
- lymph is transferred to large veins near the heart where it rejoins the blood
Digestive system functions
- digestion
- absorption
- movement of food
Digestion
the breaking down of organic molecules
Absorption
- passage from digestive system to circulatory system
What occurs in the mouth (buccal cavity)?
- ingestion
- mastication
- saliva secretion
- absorption of monosaccharides
- bolus is formed and passed to pharynx then to esophagus
Saliva Secretion
- amylase
- mucins
- lingual lipase
Amylase
- digestive enzyme
- carbohydrate dessication
Mucins
- makes things slimy for easy transportation
Lingual Lipase
- lipid digestion
What keeps food from going down trachea?
- when we swallow, the epiglottis closes
Esophagus
- surrounded by circular smooth muscles
- lumen is lined with stratified squamous epithelia
- bolus is pass through by peristalsis
Peristalsis
- wave of circular smooth muscle contractions passing down a tube
- all or none phenomenon (peristalsis and action potential)
Stomach
- contains cardiac sphincter and pyloric sphincter
- secretes gastrin
- some absorption
- forms chyme
How does the bolus drop into the stomach?
- a peristaltic wave causes cardiac sphincter to relax and bolus drops into stomach
What does the bolus in the stomach do?
- it causes the cell linings to mesh and secrete gastrin
What does gastrin do?
- causes secretion of HCL from stomach lining and denatures proteins
- causes secretion of pepsin
- causes peristaltic waves to pass over stomach (mixes stuff together which later turns into chyme)
- mucus secretion
Chyme
acidic mixture of gastric juices and partially digested food
What does the stomach absorb?
- small non-polar molecules
- ethanol
- NSAIDS
Pyloric Sphincter
- valve that regulates the passage of chyme out of the stomach into the small intestine
Cardiac Sphincter
- valve between esophagus and stomach
- allows bolus to go into stomach
What is the 3/4 life of food in stomach?
3 hours
Small Intestine
- where most digestion occurs
- where most absorption occurs
How does chyme flow from stomach to small intestine?
- peristaltic waves gradually push small amounts of chyme through the pyloric sphincter into the small intestine
What does the arrival of chyme in the small intestine cause?
- causes endocrine cells to secrete secretin and cholecystokinins
How does adrenaline affect the digestive system?
- causes the pyloric sphincter to relax and empty the digestive system
Secretin
- causes pancreas to secrete HCO3- (bicarbonate) and neutralizes chyme
- slows down gastrin secretion
Cholecystokinins
- causes secretion of pancreatic enzymes
- causes gall bladder to secret bile
Bile
- fluid that contains bile salts and bile pigments
How does digestion occur in the small intestine?
- peristalsis pushes food and enzymes down the small intestine, mixes them, and causes digestion
What is the small intestine lined with?
- columnar epithelia
What are beneath the columnar epithelial cells in the small intestine?
- capillaries that transported the digested molec throughout the body
Efficiency of digestion
- time = length of small intestine
- diet: proteins and lipids digest easily; complex carbohydrates are hard to digest
What enzyme do herbivores have that allow for the digestion of cellulose?
cellulase
Why do rabbits have longer small intestines than carnivores?
- their diet is harder to digest, so they need more time to digest it = longer small intestine
Efficiency of absorption
- surface area
- greater the surface area = greater the absorption
- 3 types
a. plicae
b. villi
c. microvilli
Plicae
- circular folds within the small intestines lining
Villi
- small, finger-like projections that line the inner surface of the small intestine
Microvilli
- folds on membrane of columnar epithelia in the small intestine
How does waste move from the small intestine to the large intestine?
peristaltic waves gradually pushes the waste through the ileocecal sphincter into the large intestine
Ileocecal sphincter
- sphincter muscle that controls the flow of waste into the LI
Ceacum
- blind sack at the end of the LI
- absorbs water and salts and solidifies the waste
Appendix
- houses beneficial bacteria
- synthesizes vitamin K
What happens as blood leaves the digestive system?
- it goes to the liver through the hepatic portal system/vein
Liver
- detoxifies harmful compounds in blood
- turns ammonia into urea
- stores glycogen
- destroys worn out RBC and produces bile
Glycogen
intermediate energy source found in liver
Bile salts
- emulsifies and allows for the digestion of fats
Bile pigments
- toxic to the body
- bilirubin and biliverdin (yellow when combined)
What happens when the liver malfunctions?
- build up of bile = build up of bile pigments = jaundice
What are the three versions of the respiratory system?
- cutaneous
- gills
- lungs
Cutaneous Respiration
- gas exchange occurs through the skin
- aquatic animals with a thin epidermis and a high vascularized dermis
- supplement for fish
- some amphibians
Gills
- organs that extract oxygen from water and release carbon dioxide
- water goes through mouth and is pumped through gills
Parts of the gill respiratory system
- gill arch
- gill filament
- gill lamellae
Gill arch
series of bony arches behind the throat that support the gills
Gill filament/lamellae
- contains capillaries
- where gas exchange occurs
What are the four aspects that enhance gill efficiency?
- ram ventilation
- lamella surface area
- diffusion distance
- countercurrent exchange
Ram ventilation
- one way path of water into gills
- constant flow of oxygen
Lamellae surface area
- larger surface area = more gas exchange
- 2.5 square feet/lb
Diffusion distance
- as the lamellae gets thinner, gas exchange is faster
Countercurrent Exchange
- diffusive exchange between two fluids flowing in close proximity and opposite directions
- maintains a concentration gradient and prevents equilibrium
- 80% of oxygen from water
Lungs
- respiratory surface = alveoli
- each alveoli is surrounded by a capillary
- negatives:
a. half time inhaling half time exhaling
b. lungs are never fully emptied
O2 + Hemoglobin <–> oxyhemoglobin
- affected by pH
- Bohr effect
- keeps O2 concentration in body low, which allows for constant diffusion
- when pH=7.4, forward rxn occurs
- when pH=7.2 reverse rxn occurs
Bohr effect
hemoglobin loses its affinity to oxygen as pH decreases
CO2 + Hb <–> carbaminoHb (CHb)
- governed by equilibrium dynamics
- acts as a pH buffer
CO2 + H2O <–> HCO3- + H+
- catalyzed by carbonic anhydrase
- forward rxn lowers pH
- reverse rxn increase pH
Step of Gas Exchange of Tissues
- CO2 from tissue diffuses into RBC
- CO2 reacts with water and lowers pH
- OHb becomes O2 and Hb
- O2 diffuses out of RBC
- CO2 and Hb bind to form CHb and prevents pH from decreasing
Gas Exchange at the Lungs
- Chb breaks down into CO2 and Hb, and CO2 is released
- CO2 diffuses out of the RBC
- CO2 concentration decreases, so HCO3- and H+ react to form CO2 and H2O, which increases the pH
- Due to the higher pH, Hb and O2 bind to form OHb
- O2 diffuses into RBC
