The Heart Beat Pages 222-224. stethoscope Cardiac Cycle The heart pumps in a cycle of filling,...
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Transcript of The Heart Beat Pages 222-224. stethoscope Cardiac Cycle The heart pumps in a cycle of filling,...
The Heart Beat
Pages 222-224
stethoscope
Cardiac Cycle
• The heart pumps in a cycle of filling, contracting and relaxing
• Systole: when the cardiac muscle contracts
• Diastole: when the cardiac muscle relaxes
• Makes the sound Lub-Dup
• 1 complete cycle takes about 0.80 - 0.85 seconds
1 Cardiac Cycle
Time Atria Ventricles
0.15 sec (atrial systole)
Systole Diastole
0.30 sec(ventricle systole)
Diastole Systole
0.40 sec Diastole Diastole
When the atria contract, the ventricles are relaxed and filling with blood.
When the ventricles contract, the AV valves close, preventing blood from flowing back into the atria.
After the ventricles contract, the cardiac muscle relaxes.
Lub-Dup
• Lub: vibration caused by the atrioventricular valves closing (ventricle closing)
• Dup: vibration caused by the semilunar valves closing
1 Cardiac Cycle
Time Atria Ventricles
0.15 sec(atrial systole)
Systole Diastole
0.30 sec(ventricle systole)
Diastole Systole (LUB)
0.40 sec Diastole Diastole (DUP)
When the atria contract, the ventricles are relaxed and filling with blood.
When the ventricles contract, the AV valves close (LUB), preventing blood from flowing back into the atria.
After the ventricles contract, the cardiac muscle relaxes (DUp).
Heart Mur-mur
• A slight slush sound after the “lub”– Ineffective valves:
allows blood to pass back into the atria after the AV valve closed
What controls the heartbeats?
• Intrinsic Control (internal)– Uses nodal tissue which possess muscular
and nervous characteristics– Beats independent of
outside nervous stimulation
• Sinoatrial (SA) node• Atrioventricular (AV) node
Sinoatrial (SA) node “Pacemaker”
• Located in the upper dorsal (back) wall of the R. atrium
• Initiates heart beats• Sends out excitation
impulses every 0.85 sec• Result: Atria contract• When it fails, heart still
works via AV node, butslower
Atrioventricular (AV) Valves
• The impulse from the SA node will reach the AV node
• Sends message to contractthe ventricles via AV bundle andpurkinje fibers
What controls the heartbeats?
• Extrinsic Control (external)– Heart rate control center = Medulla Oblongata
in the brain
• Uses the Autonomic System to alter heart beat
Sympathetic Parasympathetic
(not under conscious control)
Sympathetic Division
• Increases heart rate (heart rate > 100 beats/min)
• Increases activity or stress– “fight or flight” response
• Increases nodes’ activity when we are active or excited
What increases heart rate?
• Hormones like adrenalin / epinephrine
• Increased body temperature
• Exercise
• Drugs (caffeine, nicotine)
Parasympathetic System
• Decreases heart rate
• Promotes functions at resting state, normal activities– “rest and digest”
response
The Electrocardiogram
• Listen the heart beat (audio)
The Electrocardiogram (ECG)
• A recording of the electrical changes that occur in 1 cardiac cycle
• SA node starts
the cycle
The Electrocardiogram (ECG)
• P wave (0.15s)– occurs
just before atrial systole
• QRS complex (0.3s)– Occurs just before
ventricle systole
• T wave (0.4s)– When the ventricles
recover from contraction
The Electrocardiogram (ECG)
• ECG can be used to detect any abnormalities of the heart (irregular heart beats)– Example: Heart mur-mur
• Play audio of heart murmur
Blood&
Blood Pressure
Sphygmomanometer
How is blood pressure (BP) measured?
• Measured on the brachial artery in the upper arm
• Expressed in millimeters of mercury (mmHg)
• BP reading consists of 2 numbers– Systolic and diastolic pressures respectively– Example: 120/80
Ventricles contractBlood into arteries
Ventricles relax bw heart beats
• Systolic pressure– Blood being forced into the arteries during
ventricular systole
• Diastolic pressure– The pressure in the arteries during ventricular
diastole
Blood Pressure (BP)
• Pressure is created by the force with which the left ventricle contracts – blood leaves and enters the aorta then into
the systemic arteries under pressure– in general, as blood
moves away from the heart, its pressure decreases
High and Low BP
• Hypotension (Low blood pressure)– Reduces your capacity to transport blood– Causes: dehydration, heart failure,
anaphylaxis (life-threatening allergic reaction)
• Hypertension (High Blood pressure)– Can weaken an artery and eventually lead to
the rupturing of the vessel– BP 140/90– Causes: smoking, drugs, increase stress, diet
Blood
Pages 226 - 231
Blood
• Is a connective tissue (like bone and cartilage) because cells work together to provide critical links of – Supply– Defense– Communication
Function of Blood
• Transport – (nutrients, wastes, hormones)
• Regulatory – (body temp, BP, pH ~7.4)
• Protective – (against invasion of pathogens, blood loss)
4 Components
• To accomplish the functions, blood requires 4 components:
1. Plasma (55%)
2. Red blood cells (RBCs 45%)
3. White blood cells (WBCs)
4. Platelets (<1%)Formed elements
plasma
red blood cell
white blood cell
platelets
Plasma
• A straw-coloured liquid• Contains
– Water (90-92%)– Plasma Proteins (7-8%)– Salts (<1%)– Gases– Nutrients– Nitrogenous wastes– Hormones, vitamins
RBCs (Erthrocytes)
• Life span: 4 months• Made in bone marrow of the
– Skull, ribs, vertebrae and ends of long bones
• Mature RBCs lack nucleus• Shape: biconcave disk
– Increases flexibility for moving through capillaries
– Increases surface area for gas diffusion
• ~ 4-6million RBCs per mm3 of bloodText: figure 12.12Capillary + RBC
Why are RBCs Red?
• RBCs are red because they contain hemoglobin (Hb)
Hemoglobin (Figure 12.12)
• Respiratory pigment, red in colour
• Each molecule has 4 polypeptide chains– Each chain has a heme, a complex iron group– Picks up oxygen from lungs – Release oxygen in tissues– Carries carbon dioxide from tissues back to
lungs
RBC Degradation
• RBCs are destroyed in the liver and spleen
• iron in hemoglobin (Hb) is recycled
• Heme is excreted as bile
RBC Reproduction
• Happens in the bone marrow
Stem cell(with nucleus)
- Divide (mitosis)& Shrinks- Take up Hb(can be re-used from old destroyed RBCs)
Nucleusdisappears
Discharge RBCs
into bloodIf O2 levels decrease:
- RBC reproduction
- a result of hemorrhaging, blood transfusion, high altitude
Anemia
• A deficiency in hemoglobin (the iron) or RBCs
• Less oxygen delivered to tissues results in lack of energy
• Always feel tired• Kidney produces erythropoietin (hormone)
to speed up maturation of RBCs in bone marrow
WBCs (Leukocytes)
• Many different types• Larger than RBC• Has nucleus• Lack hemoglobin• Produced in bone marrow• 700RBC : 1WBC• 4,000-11,000 WBCs per mm3
• Fight infections• Develops immunity of body• Resist pathogens
WBCs (Leukocytes)
• We identify different types of WBCs based on:– Shape, size of nucleus, cytoplasm granules
(granular vs agranular)
Focus on 2 Types of WBCs
• Phagocytes (Macrophages)– Engulf and destroy invaders,
dead cells
• Lymphocytes (T-cells & B-cells)– Create antibodies
produce immunity to disease
Antibodies and Antigens
• Antigens – any molecule, usually a protein or carb, that stimulates the immune system
• Antibody – prevents antigens from binding onto cells
Comparing RBCs and WBCS
RBCs WBCs
Both develop from identical
stem cells in bone marrow
Look identical Different types
Mature, has no nucleus Mature, has nucleus
Smaller Bigger
Carry O2/CO2 Fights diseases
Platelets (Thrombocytes)
• Make 200 billion/day
• No nucleus
• Very tiny in size
• Irregular in shape
• Made from nucleated cells in bone marrow
• Essential for blood clotting (coagulation)
Blood Clotting (Figure 12.14)
Damaged tissue
Platelets gather at wound to seal leak
Tissue and platelets release prothrombin activator(converts plasma protein prothrombin to thrombin)
Fibrinogen activated
Ca2+
Fibrin forms – forms a net around Platelet and plug the leak
Capillary Exchange (in the systemic circuit)
Capillary Exchange (in the systemic circuit)
• Exchange of fluid is control by 2 forces– Osmotic pressure (OP)
• Created by salts and plasma proteins• Causes water to move from tissue fluid (fluid bw the
tissue cells) to the blood
– Blood pressure (BP)• Causes water to move from blood to tissue fluid• At the atrial end: BP is higher, OP is lower
– Water leaves from blood
• At the venous end: BP is lower, OP is high– Water enters into blood
• Midway of capillary: no net movement bc the 2 forces cancel each other out – DIFFUSION takes over
Midway of Capillary(for the systemic circuit)
• DIFFUSION takes over because OP and BP cancels each other out:– Nutrients and O2 diffuse out of capillary (for
absorption into tissue)– Wastes (CO2) diffuse into capillary (for
transport to the lungs)
Movement is reversed in the pulmonary circuit.
Excess Tissue Fluid
• Collected by lymphatic capillaries
• Tissue fluid contained in lymphatic vessels are called lymph
Returned to the systemic venous blood when the vessels enter subclavian vein (shoulder region)
Lymphatic System
• Closely associated with the Circulatory System
• 3 functions– Lymphatic capillaries take up excess tissue
fluid and return it to the blood– Small lymphatic capillaries absorb fats from
the digestive tracts (lacteals in villi)– Helps defend body against pathogens
Lymph Capillaries & Nodes
• Lymph capillaries– Take up excess tissue fluid from the
capillaries in the circulatory system
• Lymph nodes– Small, oviod– Cleanses lymph– Contains lots of – B and T cells