Fish Phys. CIRCULATION

sinus venosus

the 1st chamber blood flows thru. in the heart, received from the veins

• thin walled receptacle

• stretches when blood fills

• stretching activates cardiocytes

atrium

1st acceleration point, relatively thin walls with some musculature

• collects blood from the sinus venosus

• accelerates blood via relaxing/contracting

ventricle

main pump w/ the most acceleration, heavy walls of cardiac muscle

• contracting pumps blood

• relaxing refills the heart

• 2 layers

outer layer of the ventricle

• cortex — neural connection

• needs its own O2

• dense muscle fibers

inner layer of the ventricle

spongy myocardium

• myocardium = the heart’s muscular wall

bulbus arteriosus

elastic chamber that dampens blood flow, which reduces pressure

conus arteriosus

similar to the bulbus arteriosus, but for primitive fishes

cardiac output (Q) is determined by ______ & _______

• heart rate

• stroke volume

cardiac output (Q) units

ml per minute

cardiocyte

cell(s) in the sinus venosus that set the pace of heartbeat

adrenergic

stimulation that increases heartbeat

• causes tachycardia

tachycardia

increased heartbeat

• adrenergic

cholinergic

stimulation that usually decreases heartbeat

• causes bradycardia

bradycardia

decreased heartbeat

• cholinergic

stroke volume is based on?

• contractility — increases with respiration (exercise), stress (O2 demand), temperature

• filling time — impacted by pressure change in chambers & valves

• preload — volume of blood left after contraction

• afterload — pressure of the arteries that the ventricle must overcome

• elasmobranch VS teleost

burst swimming

fast acceleration in a short duration

• white muscle fibers

• anaerobic

• initial reduction of heart rate (Q)

• Q increases during recovery

sustained swimming

long-term slow movement

• aerobic

• red muscle

• heart rate (Q) is steady and constant

difference between teleosts and elasmobranchs regarding stroke volume

• Teleosts — heart rate increases with stroke volume

• Elasmobranchs — heart rate remains constant

how does temperature impact heart rate?

lower temp. = higher viscosity of blood

• higher viscosity = needs more pressure to pump blood

• results in decreased Q

how does oxygen impact heart rate?

low / no oxygen (hypoxia) = cholinergic

• decreased Q

diastolic pressure

force of blood pushing out against walls between contractions

resistance

increases with friction (against walls)

systolic pressure

force generated by the heart

systole

the heart contracting after getting blood

diastole

the heart relaxing when refilling with blood

true / false — if you move a fluid from a smaller container to a larger one, its pressure decreases

true

blood flow formula

afferent

coming to

efferent

going away