• Chapter 42 ~ Circulation and Gas Exchange

I. 2 Types of systems• A. Open circ system

– 1. Blood not confined to vessels

– 2. blood pumped into internal cavity called hemocoel

• Or cavities called sinuses

– 3. blood = hemolymph

– 4. found in most mollusks

& insects

B. Closed circ system• 1. blood confined to vessels• 2. found in vertebrates, squid

C. Blood• 1. erythrocytes = red blood cells (rbc’s)

– a.transport O2

– b. contain hemoglobin– c. no nucleus, disc-shaped– d. produced in red bone marrow– e. live appx 120 days

• 2. leukocytes = white blood cells (wbc’s)– a. large in comparison to rbc– b. 1wbc:800 rbc’s– c. 5 major types

• 3. platelets – cell fragments

– a. used in blood clotting aka coagulation

– b. release factors to change fibrinogen to its active form fibrin

– c. fibrin protein forms a network of threads to stop blood flow

• 4. plasma – liquid part of blood that contains much dissolved stuff

– makes up 55% of blood

II. Circulation• A. Fish:

– 1. 2-chambered heart

– 2. single circuit of blood flow• B. Amphibians:

– 1. 3-chambered heart

– 2. 2 circuits of blood flow-

• pulmocutaneous (lungs and skin)

• systemic (some mixing of oxygenated & deox’d blood)

• C. Mammals: 4-chambered heart– 1. double circulation- complete separation between

oxygen-rich and oxygen poor blood• a. pulmonary – heart to lungs & back to heart• b. systemic – heart to body & back to heart

Double circulation

D. Vessels

1.. Arteries carry blood away from the heart

– a. arterioles – smaller branches off of the arteries

– b. largest artery = aorta

– c carry oxygenated blood ----exception is pulmonary artery

• 2. veins carry blood back to the heart

– a.venules – smaller branches off of the veins

– b. carries deoxygenated blood – exception is pulmonary vein

• 3. Capillaries are the vessels connecting the venules & arterioles

– a. site of gas exchange with the cells

Blood vessel structural differences

E. Pathway of blood• Inf/sup vena cava RA R atrioventricular valve RV • R semilunar valve pulmonary artery lungs LA LAV

LV LSL valve aorta arteries arterioles capillaries• [cells] venules veins Inferior/superior vena cave

F. Cardiac cycle

• 1. rhythmic contraction & relaxation of heart muscle

• 2. controlled by

– a. sinoatrial node aka pacemaker

• located in upper wall of RA

• initiates cycle by contracting both atria at the same time AND sending a delayed signal to the AV node

• b. AV node located in lower wall of RA

– sends impulse through Bundle of His in septum then through the Purkinje fibers in the ventricles to cause the ventricles to contract

• 3. systole – ventricles contracting & forcing AV valves closed

• 4. diastole – ventricles relaxing

• 3. systole – ventricles contracting & forcing AV valves closed

• 4. diastole – ventricles relaxing

III. Gas Exchange• A. methods

– 1. direct exchange with envr. through cell membrane, skin, etc..

– 2. gills – outgrowths (evaginations) from body

• a. they create a large surface area

• countercurrent exchange – water traveling 1 direction over gills & blood traveling the other direction maximizes gas exchange

• 3. tracheae – chitin-lined tubes throughout body -- insects

– O2 enters through moist tracheae & out spiracles

Gas exchange• CO2 <---> O2

• Aquatic: •gills •ventilation •countercurrent exchange

• Terrestrial: •tracheal systems •lungs

• 4. book lungs – stacks/flattened internal membranes--- spiders

• 5. lungs – cavities within body (invaginated)

B. Mammalian Respiratory System

• 1. terms

– a. respiration – movement of gases into & out of organism (not to be confused with cellular respiration – process of using food to produce ATP)

– b. KNOW the anatomy of the respiratory system!!!

– c. KNOW the pathway air takes into the body (from nose to capillary)

• 2. pathway of air– a. air enter through nose

• contains hairs to filter air• lined w/ capillaries to warm air• lined w/ mucus to moisten air

– b. pharynx – back of throat where nose & mouth meet• allows breathing when nose is clogged• mouth, nostrils, trachea, esophagus &

eustachian all open into phayrnx

• c. glottis – opening to larynx

– covered by epiglottis that closes during the swallowing process to keep food from larynx

• d. larynx – voice box

– top part of trachea

– contains vocal cords• e. trachea – wind pipe

– extends from larynx into lungs in thoracic cavity

– protected by “c-shaped” cartilage

• f. bronchi – 2 branches off of the trachea

– 1 branch goes to L lung & one to the R lung• g. bronchioli – consecutively smaller branches off

of the bronchi

– each bronchiole ends in a cluster of alveoli called alveolar sacs

• h. alveolus – small air sac coated with capillaries

– site of gas exchange

– alveoli sacs are 1 cell layer thick!• ** bronchi, bronchioli, & alveoli together make

of the lungs**

Mammalian respiratory systems

3. process• a. oxygen diffuses by osmosis from the lungs into

the blood through the moist lining of the alveoli (CO2 diffuses from the blood to the alveoli)

• b. O2 moves from blood into cells again through simple osmosis

• c. CO2 diffuses into plasma then most is catalyzed to form the acid H2CO3 (carbonic acid)

– chemoreceptors in carotid artery monitor the acidity level of the blood• when the blood becomes more acidic it sends a

message to the muscles to increase respiratory rate

IV.Thermoregulation

Heat Production

• Conduction (surface to environment)

• Convection (air past surface)• Radiation (emission of waves)• Evaporation (heat loss from liquid)

Obj. 8

Endotherms & Ectotherms

• Endotherms warm themselves by metabolism

• Advantages

– Can live in a range of environments

– Can remain seasonally active

Endothermy

• Calorically expensive

– Human male require at least 1800 kcal/day

– Alligator of same size – only 60 kcal/day

Heat production can be increased by:

Increased muscle contraction– Shivering

– Movement

• Hormonal increase of metabolic rate– Nonshivering thermogenesis

Constant body temperature maintained by

• Rate of metabolic heat production• Rate of heat exchange

(vasodilation/constriction)• Rate of evaporative heat loss• Behavioral response; basking,

burrowing, migrating

Thermostat

• Hypothalamus is primarily responsible

• Bulbs of Krause and organs of Ruffini monitor temperature

Adaptations

• Birds (pouch flutter, feathers)• Marine mammals (vasodilation, blubber)• Amphibians (evaporative cooling, bask)• Fish (ectothermic, rete mirabile)• Invertebrates (some social warming)

• Acclimation

Acclimation

• Period of adjustment to new environmental temperature

Torpor – physiological state of metabolism decrease

• Hibernation - winter• estivation - summer• Diurnation - daily