chapter 5 a question of pressure. pressure: its different with solids liquids and gasses
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TRANSCRIPT
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