Lecture Four Flashcards
What keeps a muscle cell happy?
- Oxygen
- Nutrients (C6, H12,O6)
- ATP (Energy)
- CO2
- H2O
Whats the primary function of a muscle cell?
- Without O2 and nutrients, cells will rapidly die, therefore constant circulation of O2 and nutrients to all cells within the body is necessary to sustain life.
- The blood provides a medium for transporting O2, and nutrients and the removal of waste products.
What are the functions of blood as a dynamic tissue?
- Transport: of substances from one area of the body to another
- Immunity: body’s defence against disease
- Haemostasis: processes to stop bleeding
- Homeostasis: process of maintaining a stable internal environment
- Transport of regulatory molecules
- Regulation of pH
- Maintenance of body temperature
- Immunity
- Total blood volume 4-6 L (depending on body size)
What are the components of blood and describe them?
-Plasma o Composed of water with some dissolved solutes including proteins, lipids (fats), carbohydrates, amino acids, vitamins, minerals hormones, wastes, gases and electrolytes. -Platelets (Thrombocytes) o Cell-like particles, assist in blood clotting -WBCs (Leukocytes) o Primary defence against infection o Ratio of WBC: RBC = 1:700 -RBCs (Erythrocytes) o Main component is haemoglobin
What is haemoglobin composed of?
-Protein substance with 4 subunits:
o 4 x Globins
o 4 x Heme groups
What is the function of haemoglobin and how does it do this?
-Transport of O2 and CO2
o Oxygen binds to the heme group
o 1 O2 molecule to 1 heme group
o Thus 1 haemoglobin molecule carries 4 O2 molecules
-280 million haemoglobin molecules per red blood cell
What does haemoglobin give to red blood cells?
-Haemoglobin gives the red blood cell its colour
o Oxyhemoglobin is bright red
o Deoxyhemoglobin is darker red
What does carbon dioxide bind to and what are the %s?
-Carbon dioxide binds to the globin portion
o 23% of CO2 is transported by haemoglobin
o 7% in plasma
o 70% in the form of bicarb ions
Describe the production of red blood cells.
-25 trillion RBC’s in circulation
-Every second 2.5 million are destroyed
o 1% replaced each day
o Lifespan = 120 days
-Production of new red blood cells = Erythropoiesis
What is the circulatory system comprised of?
-Cardiovascular System (vascular system)
o Transports blood which contains gasses, hormones, nutrients and cells around the body.
-Lymphatic System
o Circulates Lymph which primarily assists in defending the body against foreign substances.
What are the functions of the cardiovascular system?
- Blood
o From the heart to the tissues and back to the heart again.
2.Exchange nutrients, waste products and gases with tissues
o Nutrients and Oxygen move from the vessels to the tissues.
o Waste products and Carbon dioxide move from the tissue to the vessel.
3.Transport substances
o Hormones, enzymes, nutrients, gasses, waste products are all transported in blood.
4.Assists with regulation of blood pressure
o Heart and blood vessels work together.
5.Directs blood flow to tissue
o In order to maintain homeostasis, the circulatory system can direct to tissues in need.
Describe the circulations of the the circulatory system
-Systemic Circulation:
o Heart (Left ventricle) to body tissues
-Pulmonary Circulation:
o Heart (Right Ventricle) to lungs (alveolus)
-Coronary Circulation:
o Myocardium
What are the components of the cardiovascular system?
-Heart
-Blood Vessels
o Arteries
o Capillaries
o Veins
Describe what the pulmonary artery & vein do?
Pulmonary Artery- To the lungs, only artery that contains deoxygenated blood (usually arteries contain oxygenated blood).
Pulmonary Vein-Coming from the lungs, only vein that contains oxygenated blood.
Describe how the heart functions as two seperate pumps.
-The heart functions as two separate pumps:
-One pump (right side) receives blood from body and pumps it to lungs for oxygenation.
o Pulmonary Circulation
-The other pump (left side) receives blood from lungs and circulates it around the body and back to heart.
o Systemic Circulation
Describe the cardiac muscle structure and what are the specialised junctions?
-Striated, branching chains of cells that uni- or binucleate
-Fibres connected mechanically and electrically
-Functional syncytium
-Adjacent cardiac muscle cells are joined end to end by intercalated discs, which contain two types of specialized junctions:
o Desmosomes
-Mechanically holding the cells together
o Gap Junctions
-Permit action potentials to propagate from cell to cell
What is the cardiac function, what is diastole & systole?
-Cardiac Cycle
o All mechanical and electrical events that occur during one heartbeat
-Diastole – Relaxation Phase
o Chambers fill with blood Twice as long as systole
o Ventricle untwists, lengthens, unthickens
-Systole - Contraction Phase
o Chambers eject blood
o High pressure
o Ventricle twists, shortens, thickens
o ‘Wet Towel’
What is the electrical activity of the heart?
- All parts of the conducting system have specialised autorhythmic cells
- Rapid spread of electrical activity for initiating and conducting impulses
What do the Sinoatrial & Atrioventricular node do?
Sinoatrial Node
o Determines inherent rhythm i.e. primary pacemaker
Atrioventricular Node
o Delay impulse ensuring complete atrial systole prior to ventricular systole
-Controlled spread of electrical excitation ensures:
o Time to complete atrial contraction (0.12 s delay from SA to AV)
o Synchronised contraction of muscle fibres
o Each pair of chambers contracts simultaneously
How is the heart rate regulated (pacemaker, nervous system & hormonal influence)?
-Pacemaker (SA node)
o Impulse generated and travels across atria to AV node then to ventricles
o Intrinsic firing rate ~100bpm
-Influenced by Autonomic Nervous System (ANS)
o Sympathetic and parasympathetic branches
o At rest, parasympathetic stimulation decreases HR (~60-70 bpm)
o During exercise, withdrawal of vagal tone, concurrent increase in sympathetic nerve innervation to increase HR
-Hormonal Influence
o Sympathetic components increase HR by release of catecholamines: adrenaline & noradrenaline
What is an Electrocardiogram?
-Recording of hearts electrical activity
-Diagnostic tool
o 12-Lead ECG
-Different electrical ‘views of the heart
What is a P wave, QRS complex & T wave?
P wave
-Impulse arising from the SA node results in depolarization and contraction of the atria (the right atrium contracts slightly before the left atrium).
-This atrial depolarization = atrial systole.
QRS Complex
-Due to ventricular depolarization, marks the beginning of ventricular systole.
-Masks the underlying atrial repolarization signal.
T wave
-Ventricular repolarization
-End of T wave marks end of ventricular systole electrically
What is the Venous System?
- One-way valve system to prevent back flow
- Skeletal muscle pump assists against gravity
- ‘Capacitance’ vessels
- Most of blood volume contained in the veins
What is Systemic Circulation?
- Oxygenated blood carried away from heart to body tissues
- Pressure and velocity of blood decreases as total cross-sectional area increases
What is Pulmonary Circulation?
- Transporting oxygen-depleted blood away from the heart, to the lungs, and back to the heart
- De-oxygenated blood moves into the pulmonary arteries from the right ventricle, to the lungs
- Oxygenated blood moves from the lungs, via the pulmonary veins, into the left atrium
What is Coronary Circulation?
-The role of coronary circulation is to provide the heart muscle (myocardium) with oxygenated blood to enable function.
Coronary Arteries
-Right Coronary Artery (RCA)
o Right ventricle and right atrium
-Left Coronary Artery (LCA)
o Splits into Left Anterior Descending and Circumflex branches
o Left ventricle and left atrium
What are the cardiovascular functions?
1.Cardiac Cycle
o All mechanical and electrical events in one heartbeat
2.Stroke volume (SV)
o Volume of blood pumped out of the heart with each beat
3.Heart Rate (HR)
o The number of times the heart beats per minute
4.Cardiac Output
o Total volume of blood pumped out of the heart per minute
o CO = HR x SV
5.Ejection Fraction
o The fraction of blood pumped out of the left ventricle with each contraction.
Describe stroke volume and cardiac output
-Stroke volume (SV)
o During systole, most (but not all) blood ejected
o e.g. 100 mL – 40 mL = 60 mL
-Cardiac Output (Q)
o Resting HR ~80 beats/min, standing SV ~60 mL/beat
o 80 beats/min x 60 mL/beat = 4,800 mL/min
o Unit of measurement L/min (4.8 L/min)
-Resting Cardiac Output ~4.2 to 5.6 L/min
Describe cardiac output at rest.
-Cardiac output at rest varies considerably
o ~5 L.min-1 (average male)
-SV = ~70 mL
o ~ 4 L.min-1 (average female)
-SV = 50 – 60 mL
o Gender difference related to body size
-Affected by:
o Emotional conditions (cortical outflow altered; centre command factors, anticipation to exercise).
-During Exercise
o Cardiac output (CO = HR x SV) can increase up to 7 times
Describe systolic and diastolic blood pressure
-Systolic blood pressure (~120 mm Hg)
o Maximal pressure of blood against the arterial’s walls during systole (heart contraction; ventricle contraction).
o Estimate of how hard the heart is working and strain on arterial walls during ventricular contraction.
-Diastolic blood pressure (~70-80 mm Hg)
o Pressure exerted by blood against the arterial walls during diastole (heart relaxation; ventricle relaxation).
o During relaxation (diastolic) phase of cardiac cycle, arterial blood pressure decreases.
o Indicate peripheral resistance i.e. the ease with which blood flows from arterioles into capillaries.
