Download Blood Pressure - TangHua2012-2013

Human Biology: Circulatory System
Lesson 3: Structure and Function of the Heart
(Inquiry into Life pg. 220-226)
Today’s Objectives

Describe the inter-relationships of the structures of the heart,
including:



Identify and give functions (including direction of blood flow) for the major
structures of the heart
Recognize heart structures using both internal and extrenal diagram views
Analyse the relationship between heart rate and blood
pressure, including:





Describe the location and functions of the sinoatrial (SA) node,
atrioventricular (AV) node, and Purkinje fibres
Describe how the autonomic nervous system increases and
decreases heart rate and blood pressure
Differentiate between systolic and diastolic pressures
Describe hypertension and hypotension and their causes
Demonstrate the measurement of blood pressure
Heart Quiz
Parts of the Heart (video)

Left and Right Atria –
Collecting Chambers



Right: collects blood from
Venae Cavae
Left: Collects blood from
Pulmonary Veins
Left and Right Ventricles –
Pumps


Right: Sends blood to the lungs
via the Pulmonary Trunk
Left: Sends blood to the body
via the Aorta
Parts of the Heart

Atrioventricular Valves



Valves between the atria and ventricles
Prevent backflow of blood
Right side valve called “Tricuspid Valve”



Left side valve called “Bicuspid Valve”



Has three cusps, or flaps
Also called right atrioventricular valve
Has two cusps, or flaps
Also know as the mitral valve or left atrioventricular valve
Chordae Tendonae


Strong, fibrous strings that support the A.V. valves
Keep the flaps from inverting with the force of blood flow
Heart Valves
Parts of the Heart

Semi-lunar Valves (no chordae tendonae)



Pulmonary Trunk



Between ventricles and the Aorta (Aortic Valve)
Between the ventricles and the Pulmonary Trunk (Pulmonary
Valve)
Branches off to form the Pulmonary Artery
Receives blood from the right ventricle
Septum (Ventricular Septum)


The wall of the Heart
Separates the left and right sides of the Heart
Diagram
Cardiac Cycle and Intrinsic Beat

Contraction of the Heart is a two step process:


Systole – Contraction of the Heart
Diastole – Relaxation of the Heart
Each heart beat (Cardiac Cycle) consists of:
TIME
ATRIA
VENTRICLES

0.15 Sec
Systole
Diastole
0.30 Sec
Diastole
Systole
0.40 Sec
Diastole
Diastole
0.85 Sec
 Average time of 70 beats per minute
Cardiac Cycle



The ventricles have a stronger and longer contraction
because blood must be pumped throughout the body
The “lub-dup” sound of the heart is due to the closing of
the valves: first the atrioventricular, then the semi-lunar
The beat of the heart is said to be intrinsic, meaning it
will beat without any nervous system stimulation


It can be removed from the body and still continue beating!)
The beat is controlled by a special type of tissue called
Nodal Tissue, which has both muscular and nervous
tissue characteristics
Nodal Tissue


There are two locations of Nodal Tissue in the Heart:
1) SA Node (Sinoatrial Node)


2) AV Node (Atrioventricular Node)




Found in the upper wall of the right atrium
Found at the bottom of the right atrium near the Septum
The SA Node (also called the pacemaker) initiates the
heartbeat and sends out an excitation impulses every 0.85
seconds.
The impulse causes both Atria to contract. The impulses are
sent to the AV Node Via the bundle of His.
When the impulse reaches the AV Node, an impulse is sent
from the AV Node, down the Purkinje Fibers causing both
ventricles to contract.
Electrocardiograms (EKG)





An electrocardiogram registers the voltage change
across the surface of the heart as it beats.
The letters PQRST are the standard labels used to
identify the parts of the EKG
The P curve records the simultaneous contraction of
the atria as they drive the blood out into their ventricles
The QRS is the contraction of the ventricles as they
drive the blood out into their respective arteries
The T marks the recovery of the Ventricles (restoration
of the normal electrical condition, preparing them for the
next contraction)
Autonomic Control of the Heart





The rate of the heart can also be controlled by the nervous
system
The heart rate center is located in the Medulla Oblongata
of the brain.
The SA Node is connected to the brain by the vagus nerve
(cranial nerve #10)
This nerve pathway is called the Autonomic Nervous
System (not under conscious control)
Has two systems that affect the Heart Rate:


Parasympathetic System – causes the heart beat to slow down
Sympathetic System – causes the heart beat to increase during
times of stress
Autonomic Nervous System


Factors such as a need for oxygen or the blood
pressure level determine which of those systems
become active
When the brain perceives that the blood is getting
delivered to the tissues too slowly, or if blood
pressure is low,
the brain will
signal the SA
Node to speed
up its contraction.
Blood Pressure






Ventricles pump a volume of blood (approx 70 ml) each
time they contract
Must have elastic, expandable walls
The force of blood against the blood vessel walls is
known as Blood Pressure
Blood Pressure is not constant
The term Systolic pressure (or Systole) refers to the
blood pressure when the ventricles contract
The term Diastolic pressure (Diastole) refers to the
blood pressure when the heart is at rest
Pulse




As blood is pumped through the arteries, the arterial
walls swell, then relax
This swelling can be felt in any artery that runs close to
the surface
Blood pressure is normally measured along the brachial
artery of the arm
A reading of 120/80 is quite normal


120 - Systolic reading as ventricles contract
80 – Diastolic reading as the heart relaxes
Blood Pressure Changes


A number of things can affect the blood pressure:
Hypertension: High Blood Pressure



Example: 140/90 or 125/90
Diet and Lifestyle are often to blame for elevated blood
pressure
Reasons for Hypertension:



Stress
Plaques – formed by fatty acid deposits from digested foods;
line the walls of the arteries, making the radius smaller, thereby
raising blood pressure, (Arteriosclerosis, Stroke, Heart Attack)
High Salt Intake – retains water – greater fluid volume leads
to greater volume of blood
Blood Pressure Changes

Hypertension continued..






Smoking
Stimulants
Lack of Exercise
Diet – amount of food and type
Working too hard
Age, Sex, Race
Hypotension

Low Blood Pressure



Blood does not reach all organs
Example: 110/70
Reasons for Hypotension:



Cuts or amputated limbs
Drugs
Hormones
Effects of Blood Pressure Change



Proper Kidney function can only be maintained if there is
a sufficient pressure for filtration
Luckily, the body can adjust blood pressure
Monitored by the Hypothalmus (part of the brain), the
body can dilate (widen) arterioles thus lower blood
pressure in them, or constrict (narrow) them to raise
the blood pressure