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Circulation
Circulatory Plans
Regulation of heart &
cardiac output (CO)
Circulatory adjustments
to stress, including
Exam II
-week from today
-format as on Exam 1
Review Session – Thursday Oct 27, 5:00-6:00,
Cushing 001
Q: Why does blood pressure not fall to
zero when the heart relaxes?
elastic recoil
capillaries
precapillary
sphincter
D) Circulatory plans
single-circuit circulation
divided circulation
single-circuit circulation
divided circulation
pulmonary
circuit
systemic
circuit
Q: Why have a divided circulation? Advantage?
QQ: Could it ever be advantageous to
have an incompletely divided
circulation?
crocodilians
Q: Is there ever incomplete separation in mammals??
E) Regulation of Heartbeat
and Cardiac Output
myogenic
…not neurogenic
SA node
pacemaker
S-A node (mammals; similar
tissue in birds & most
reptiles)
sinus venosus
(fish, amphibians, turtles)
A-V node
Myogenic!
autonomic innervation
of the heart
-alters rate & force of contraction
(rest and digest)
vs
(flight or fight)
nerve fibers
in smooth muscle
-vasoconstriction vs.
vasodilation
autonomic innervation
of the heart
acetylcholine
(neurotransmitter)
smooth muscle relaxes
heart slows, beats less
forcefully
norepinephrine
epinephrine
smooth muscle contracts
heart speeds up, beats more
forcefully
norepinephrine
epinephrine
smooth muscle contracts
heart speeds up, beats more
forcefully
autonomic nervous system allows
adjustments in:
1) distribution of blood flow
2) cardiac output (CO)
Q: what parameters determine CO?
CO (ml/min) = HR (beats/min) X SV (ml/beat)
heart rate
stroke volume
parasympathetic activation
HR
SV
sympathetic activation
HR
SV
Circulatory Adjustments to Stress
homeostasis
-an integrated compensatory
response to a ‘challenge’,
that in turn helps to maintain
a balance In some physiological
parameter
exercise…
sensory receptors à brain à effectors
(neural/endocrine)
1. standing up
baroreceptors
carotid sinus
aortic arch
postural hypotension
vasomotor center
increase HR
vasoconstriction in large arteries
peripheral venoconstriction below
heart
2. exercise
Q: Could the concentration of O2 in the blood be increased?
HR
during exercise
capillaries in skeletal muscle
vasodilation of arterioles
supplying muscle
precapillary sphincter
precapillary
sphincter
autoregulation, using
precapillary sphincters &
nitric oxide (NO)