Download Cardiac Cycle, Blood Pressure, Blood velocity, and Blood Vessel

Cardiac Cycle, Blood
Pressure, Blood velocity,
and Blood Vessel crosssectional area
Heartbeat Control: Intrinsic
- nodal tissue within the heart controls
normal heartbeat
- Sino atrial node initiates
- impulse conducted into both atria
simultaneously, they contract = atrial
systole, blood forced into ventricles.
- ventricles are relaxed (diastole) and fill
with blood.
- Impulse moves to atrioventricular node
(AVN) (location?)
- conducted through septum to Bundle of
-
impulse carried from Bundle of
HIs through the walls of
ventricles by Purkinje fibers
-
causes ventricular systole,
forcing blood out of ventricles
into the pulmonary trunk and
aorta.
-
Atria are in diastole and filling
with blood
-
Complete 1st page notes
Animation of cardiac cycle
Watch video at 1:30
Modification of the Normal Heartbeat
-modification =speeding up or
slowing down
-stimulation by nerve impulses or
hormones
-autonomic nervous system or
endocrine system = extrinsic control
of heartbeat
Autonomic regulation of heartbeat: Nervous system
-
two divisions: sympathetic and
parasympathetic
-
Stimulus: hypotension (low blood
pressure)
-
Receptor: cardiovascular centre
of the medulla oblongata
-
Effector: sympathetic division of
autonomic nervous system
-
Response: increase heart
rate/stronger
Autonomic regulation of heartbeat: Nervous system
-
Stimulus:Hypertension/ high
blood
-
Receptor: cardiovascular center
of medulla oblongata
-
Effector:parasympathetic division
of autonomic nervous system
-
Response: decreased heart rate/
weaker heartbeat/decrease in
blood pressure
Hormonal Regulation of Heartbeat/endocrine system
-
Stimulus: low blood pressure/
hypotension
-
Receptor: cardiovascular center
of the medulla oblongata
-
Effector: sympathetic division of
autonomic nervous system
signals adrenal medulla to
release adrenaline and
noradrenaline
-
Heart: increase heart rate/
Blood Pressure, Velocity, Blood vessel crosssectional area
-
Blood pressure= force of blood
on walls of blood vessels
-
b.p. highest in arteries and
lowest in veins
-
b.p.in arteries oscillates in
response to ventricular systole
and diastole
Blood velocity
-blood
velocity= speed at which blood
moves through the blood vessels
blood velocity oscillates in arteries
in response to systole and diastole of
ventricles
-
-decreases and reaches lowest level
in capillaries
-increases once again in venules and
veins
Blood vessel cross-sectional area
-
total cross-sectional area of all
blood vessels of a particular type
-
arteries and veins, individually,
have a large cross-sectional
area but low total c.s.area due to
relatively small number
-
capillaries have small c.s. area
individually but a high total due
to large numbers.
-
c.s. area highest in capillaries
So what?
-blood pressure and blood velocity
oscillate in arteries due to systole and
diastole
- b.p and b.v. decrease due to
increasing c.s area and increasing
friction btwn. blood vessel walls and
blood.
-low b.v allows time for exchange
btwn. blood and tissues/cells
-blood
pressure in venules and veins
is low due to distance from heart
-blood velocity increase in venules
and veins due to:
*contraction of skeletal muscles
*decrease in cross-sectional area
*expansion of thoracic
cavity/decreases pressure on vessels
going back to heart.
How is blood pressure measured?
-
Measured using a
sphygmomanometer in mm of
Hg
-
systolic=ventricle walls
contracting
-
diastolic=ventricle walls relaxing
-
measured at brachial artery
above elbow, stethoscope on
inner arm
-
pump cuff until no sounds are
-
first sounds heard are systolic
b.p.
-
reduce pressure on cuff until no
sounds heard = diastolic
-
average = 120/80 mm
-
varies depending on
Homeostatic mechanisms
-
homeostasis is maintained by
1. vasodilation of peripheral blood
vessels, increases heat loss, ,
cools body, decreases b.p.
2. vasoconstriction reduces heat
loss, aids in maintaining core
temp. and raises b.p.
3. increase heart rate= more
Oxygen to cells= increase in b.p.
Hypertension- what is it? how does body respond?
-
abnormally high b.p.
-
contributing factors:
1. excessive saturated fat/
cholesterol leads to
artherosclerosis
(fatty deposits in the
arteries restrict blood flow)
Hypertension factors
2. excessive salt in diet, increases
blood osmotic pressure draws water
into blood and increases b.p.
3. Nicotine causes vasoconstriction
and increases b.p.
4. genetic factors predispose people
to high b.p.
5. diabetes and kidney disease may
lead to hypertension
#1-4 = life-style choices
Hypotension: what is it?
-
Abnormally prolonged low b.p.
Contributing factors:
1. excessive blood loss->
decreases b.p.
2. decreased cardiac output = less
blood forced through the system
3. leaky heart valves-> backflow->
less blood through system
Modification of normal heartbeat