Cardiovascular System -Heart AND Blood Vessels function together -Bulk Transport vs. Diffusion -Laws of Chemistry and Physics set limits -The way evolution builds it is NOT the way an engineer would build it

Cardiovascular Essential Questions What are the functions of the CV system? What are the different types of CV systems (open; closed)? Why are there 2, 3 and 4 chambered hearts? How does the body monitor and adjust CV function?

Surface area to volume ratio (Large surface area needed wherever diffusion is utilized) Heart, bronchi and some of the arteries

Arteries of the systemic circulatory system (torso)

Arteries of the neck and brain

Functions of the Cardiovascular System There is much more blood flowing to the rabbit’s ears than is needed to support that amount of tissue. Whenever you see a disproportionately large amount of blood flowing to a region you know there must be more going on than just delivery of nutrients.

Functions of the Cardiovascular System Deliver Nutrients (O2, glucose, fatty acids, water*) Remove Wastes (CO2, nitrogen compounds, water*) Heat/Cool (deliver or remove heat) Deliver Hormones (epinephrine, cortisol) Movement (spider jump) Certain aspects of reproduction (erection)

Open vs. Closed

Spider Jump Leg extension in spiders involves pumping of fluid into legs to “inflate” them They do have muscles to flex their legs.

Types of Closed CV Systems Two chambers (one ventricle*) Three chambers (one ventricle*) Four chambers (two ventricles*) *Ventricles are responsible for doing all the work

Dual Circulation Dual Pump Systemic. to body Dual Circulation Dual Pump Systemic *to body *high oxygen in arteries Pulmonary *to lungs *low Oxygen in arteries

Left more muscular Does more work

Electrical Activity Coordinates Heart Beat Pacemaker cells set Heart Rate Sympathetic Activation Speeds up rate Strengthens contraction of muscle Parasympathetic Activation Slows rate Weakens contraction

Physics of Blood Flow BUT… CV system must provide blood flow BUT… It must also provide pressure Pressure is monitored for the purposes of homeostasis.

Blood Pressures and Posture Density of blood is similar to density of H2O therefore similar changes in pressure with posture 1 mmHg = 13.5 mm H2O (0.53 inches H2O) 44mmHg = 594mm H2O (23 inches H2O) ~23in

What about other creatures?

100 mmHg 260 mmHg 420 mmHg What is the blood pressure in the head of a giraffe? 14 ft

What about creatures that lie flat?

Ohm’s Law (relationship between pressure, flow and resistance) V=IR (equation for flow of electricity) Pressure = Flow x Resistance (equation for the flow of fluid) P = Cardiac Output x Total Peripheral Resistance C.O. = (Heart Rate x Stroke Volume) (ml/min) = (beats/min) x (ml/beat) P = (H.R. x S.V.) x TPR (mmHg) = (ml/min) x (mmHg/ml/min)

Blood Vessels

Blood Vessels

Blood Pressure in CV system

Need pressure for filtration

Where is the blood?

Where is the blood?

Do we have more blood than we need? Veins of the systemic circulation act as a reservoir where blood is allowed to pool under resting conditions. When more Pressure and C.O. is needed, not only does the heart beat faster and stronger, the veins squeeze on this reservoir to push more blood back to the heart. Veins are now aqueducts rather than reservoir

Nervous System Control of Cardiovascular System HEART 1. Heart Rate Symp↑; Parasymp ↓ 2. Strength of Heart contraction Symp↑; Parasymp ↓ (Both 1 & 2 ↑ ↓ cardiac output – more/less flow) Blood Vessels 1. Resistance in arterioles Symp↑ (↑ Pressure & shunt blood away from some tissues & towards other tissues) 2. “Squeezing” of veins Symp↑ (↑ cardiac output by ↑ effective blood volume by pushing more blood back to heart)

Symp also innervates arterioles and veins

How does the brain monitor Cardiovascular System Function? Pressure sensing neurons in the walls of the carotid artery) monitor pressure in this blood vessel and send signals to the brainstem which controls heart and blood vessels There are other pressure sensing neurons in upper chest (aortic arch) as well Key point - pressure is measured in vessels feeding the brain.

CV System Design