1. Cardiac Cycle, Blood Pressure, Blood velocity, and Blood Vessel cross-sectional area

2. 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 HIS

3. 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

4. Animation of cardiac cycle
Watch video at 1:30

5. 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

6. 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 heartbeat/increased b.p.

7. 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

8. 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/ stronger heartbeat/increase blood pressure

9. Blood Pressure, Velocity, Blood vessel cross-sectional 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

10. Blood velocity -decreases and reaches lowest level in capillaries
-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

11. 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 and lowest in arteries and veins.

12. 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.

13. 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 heard
first sounds heard are systolic b.p.
reduce pressure on cuff until no sounds heard = diastolic
average = 120/80 mm
varies depending on activity/anxiety

14. Homeostatic mechanisms
homeostasis is maintained by
vasodilation of peripheral blood vessels, increases heat loss, , cools body, decreases b.p.
vasoconstriction reduces heat loss, aids in maintaining core temp. and raises b.p.
increase heart rate= more Oxygen to cells= increase in b.p.

15. Hypertension- what is it? how does body respond?
abnormally high b.p.
contributing factors:
excessive saturated fat/ cholesterol leads to artherosclerosis (fatty deposits in the arteries restrict blood flow)

16. 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

18. Hypotension: what is it?
Abnormally prolonged low b.p.
Contributing factors:
excessive blood loss-> decreases b.p.
decreased cardiac output = less blood forced through the system
leaky heart valves-> backflow-> less blood through system

19. Modification of normal heartbeat