Chapter 5

A Question of Pressure

Pressure: Its different with solids liquids and gasses

GravityThe Major problem of circulation which is made worse because we walk up-right

Water Compresses Gas

Gravity is Pressure on gas, it compresses it

Cardiovascular System

• Heart: A 4 chambered muscular bump

• Blood Vessels: Paths through which blood can flow

• Blood: Water, molecules, ions, and Cells

• Purpose: To distribute resources around the body

Heart (left side)

Arteries

Capillaries

VeinsHeart (Right side)

Lungs Capillaries

(O2 in) (CO2) out

O2

O2

O2

O2OUT

CO2

CO2

IN

CO2

CO2

Heart: a pump that contracts and relaxes rhythmically

Relaxed: Blood enters the heart

Contraction: Pushes blood out of the heart

Heart Cells have an intrinsic rhythm

Atrial cells ~70 beats/min

Ventrical cells~ 30 beats/min

Left atria: The pace maker

The Rhythm of the Heart

Heart: Pressurized water pump that delivers ions, molecules and heat around the body

Very important in gas exchange: eg flow of CO2 and O2 around the body

Control of the Heart

• Without any input from the brain the heart will contract to the rhythm of the pacemaker

• The autonomic nervous system can alter the rate and strength of contraction– Parasympathetic: slower, weaker– Sympathetic: faster, stronger

Blood Pressure

• Eg. 120/60

• For Blood to move, the pressure generated by the heart must exceed the back Pressure in the system.

• The difference between the “top” and “bottom” numbers is the pressure to do the work of moving the blood

Measuring Blood Pressure

Blood Flow

As a artery gets larger resistance goes down and flow goes up

The rule also applies to forks in the road

Resistance is how open/closed an artery is

Local Volume control

• By opening and closing arteries the brain can change the volume of blood going to different places in the body– Acute stress– Temperature regulation– Digestion– Immune/Inflammatory reactions: volume can

leave circulation (swelling , congestion)

General Volume Control

• The amount of Water in the body can change

• The concentrations of ions must be maintained “just right”

• Na+ : The most important ion for volume control

• Low salt diets

A Balance

Kidney

• Kidney: Filters out water, ions and small molecules from circulation and returns the “right amount of each to circulation

• Generally all small molecules such as sugars and amino acids are returned (not Urea)

• Return of water and ions must be balances

Control of the Kidney

• Blood flow to the kidney: how much blood is filtered (autonomic nervous system)

• Antidiuretic hormone (ADH) from the pituitary: increases the recovery of water (low blood pressure high Na+ concentration

• Mineralocorticoids a steroid from the adrenal gland: increases the recovery of Na+ ( low Na+

concentration)

Problems with Blood Pressure

• Prehypertension: >140/90– Volume– Resistance– Congestive heart failure

Hyoptension: harder to define (athletes)

gravity

shock

Back to the Problem of Blood Distribution

The Sinuses Prevent Blood from Falling out of the Head

Returning Blood from the Feet: Push and Suck

Push Suck

The expanding chest when you breath

The expanding heart when it relaxes

Skeletal Muscles

Water Environments of the Body

With out circulation the large water environments inside and outside cells starve and become stagnant

Control of circulation

• Heart: How often, how strong

• Arteries: How open

• Capillaries: exchange permeability

• Veins: Push and suck

• Kidney: General volume control

Metabolic Syndrome

• Diabetes

• Hypertension

• Athrosclerosis

• Blindness

• Kidney failure

• Impotance

• stroke