week 8 Flashcards
(47 cards)
1
Q
What are the two circulations controlled by the heart?
A
- Pulmonary circulation: sends blood to lungs
- Systemic circulation: sends blood to the rest of the body
2
Q
Describe the location of the heart in the body.
A
- In the chest cavity
- Slightly left and posterior to the sternum
- Base: upper part (vessels attached)
- Apex: lower pointed part
- Lies in the pericardial cavity
3
Q
What are the names and characteristics of the heart’s four chambers?
A
- Atria (left & right): upper, thin-walled
- Ventricles (left & right): lower, thick-walled (left is thickest)
4
Q
What is the main difference between arteries and veins?
A
- Arteries carry blood away from the heart
- Veins carry blood toward the heart
5
Q
What structures are involved on the right side of the heart?
A
- Superior/inferior vena cava →
- Right atrium →
- Tricuspid valve →
- Right ventricle →
- Pulmonary valve →
- Pulmonary arteries (to lungs)
6
Q
What structures are involved on the left side of the heart?
A
- Pulmonary veins →
- Left atrium →
- Bicuspid (mitral) valve →
- Left ventricle →
- Aortic valve →
- Aorta (to body)
7
Q
Define systole and diastole.
A
- Systole = Contraction (blood pushed out)
- Diastole = Relaxation (chambers fill with blood)
8
Q
What are the main phases of the cardiac cycle?
A
- Atrial systole
- Atrial diastole
- Ventricular systole
- Ventricular diastole
9
Q
What valves prevent backflow in the heart?
A
- Tricuspid: right AV valve
- Bicuspid (mitral): left AV valve
- Pulmonary valve: RV to pulmonary artery
- Aortic valve: LV to aorta
10
Q
Name the key parts of the heart’s conducting system.
A
- SA node (right atrium): pacemaker
- AV node (between atria and ventricles)
- Conducting cells: distribute signal through ventricles
11
Q
Trace the electrical pathway through the heart.
A
SA node → AV node → AV bundle → Bundle branches → Purkinje fibers
12
Q
What is shown in an electrocardiogram (ECG)?
A
- P wave: atrial contraction
- QRS complex: ventricular contraction
- T wave: ventricular relaxation
13
Q
What produces the “lub-dub” sounds of the heart?
A
- Lub (S1): AV valves closing
- Dub (S2): Semilunar valves closing
14
Q
How is cardiac output (CO) defined and calculated?
A
- CO = HR × SV
- Measured in L/min
- E.g., HR = 75 bpm, SV = 80 mL/beat → CO = 6 L/min
15
Q
What factors increase or decrease heart rate?
A
- ↑ HR: Sympathetic NS, adrenaline, increased venous return
- ↓ HR: Parasympathetic NS
16
Q
What factors affect stroke volume?
A
- ↑ SV: Sympathetic NS, adrenaline, increased preload (filling)
- ↓ SV: Anti-hypertensives, increased afterload (BP)
17
Q
Define preload and afterload.
A
- Preload: Stretch of ventricles from filling (↑ SV)
- Afterload: Resistance to ejection (↑ BP = ↓ SV)
18
Q
Where is most of the blood in the body located at any one time?
A
- Venous system: 65–70% (approx. 3.5L)
- Heart, arteries & capillaries: 30–35% (approx. 1.5L)
19
Q
What are the five main types of blood vessels in order of blood flow?
A
- Arteries
- Arterioles
- Capillaries
- Venules
- Veins
20
Q
What are the three layers of a blood vessel wall?
A
- Tunica intima – inner layer; endothelium + connective tissue
- Tunica media – middle; smooth muscle + connective tissue
- Tunica externa – outer; connective tissue sheath
21
Q
What are elastic arteries and what is their role?
A
- Conduct blood away from heart
- Contain elastic fibres in tunica media
- Under autonomic control (vasodilation/vasoconstriction)
22
Q
What are muscular arteries and what is their role?
A
- Deliver blood to skeletal muscles and organs
- Have thick smooth muscle layer in tunica media
23
Q
What makes arterioles different from arteries?
A
- Smaller, thinner smooth muscle layer
- Respond to autonomic and hormonal signals
- Known as resistance vessels – control blood flow to tissues
24
Q
What are the key features of capillaries?
A
- Smallest blood vessels
- Wall = one cell layer (endothelium only)
- Allow exchange between blood and interstitial fluid
- Blood flows slowly; diameter = ~1 RBC
25
26
How do continuous and fenestrated capillaries differ?
* Continuous: tight junctions, common, form blood-brain barrier
* Fenestrated: pores for rapid exchange, found in kidneys & GI tract
27
How is blood flow through capillary beds controlled?
* Supplied by collaterals (multiple arteries)
* Flow controlled by pre-capillary sphincters
* Arteriovenous anastomoses connect directly to venules
28
What are venules and what’s unique about them?
* Formed from merged capillaries
* Lack tunica media
* Lead into veins
29
How do veins differ from arteries?
* Thinner walls
* Larger lumen
* Valves to prevent backflow
* Lower pressure (~10% of aortic pressure)
30
What helps blood return to the heart through veins?
* Valves (prevent backflow)
* Skeletal muscle contraction
* Respiration
* Blood pressure (minimal)
31
How do arteries and veins compare structurally and functionally?
* Arteries: thick walls, elastic recoil, no valves, smaller lumen
* Veins: thin walls, no recoil, valves present, larger lumen
32
How do gases, water, and nutrients move through capillaries?
* Gases: O₂ & CO₂ via diffusion
* Water: via osmosis (e.g., kidneys)
* Electrolytes: via concentration gradient
* Glucose/amino acids: via membrane transporters (esp. muscle & GI tract)
33
What are the three main mechanisms of exchange at capillaries?
1. Diffusion – gases, water, electrolytes, steroids
2. Filtration – driven by hydrostatic pressure, pushes fluid out
3. Reabsorption – driven by BCOP, pulls fluid in due to plasma proteins
34
How do water, electrolytes, glucose, amino acids, and steroids diffuse through capillaries?
* Water & electrolytes: through pores or between endothelial cells
* Glucose & amino acids: via transporters/channels
* Steroids: through endothelial cell membranes (lipid-soluble)
35
How much fluid is filtered and reabsorbed at capillaries per day?
* Filtration: ~24 L/day
* Reabsorption: ~20.4 L/day
* Remaining fluid returns via the lymphatic system
36
What equation describes blood flow and what do its variables mean?
F ∝ ΔP / R
* F = blood flow
* ΔP = pressure gradient
* R = resistance (affected mainly by vessel diameter)
37
What determines vascular resistance?
* Vessel diameter (main factor – smaller = more resistance)
* Viscosity of blood
* Vessel length
38
What is autoregulation and what causes vasodilation?
* Maintains appropriate blood flow to tissues
Vasodilators include: ↓O₂, ↑CO₂, ↑lactic acid, ↑NO, ↑K⁺, ↑temp
39
What substances cause local vasoconstriction in blood vessels?
* Endothelin (from endothelial cells)
* Prostaglandins & thromboxane (from platelets)
* ↓ metabolic signals (e.g. ↓CO₂, ↑O₂)
40
How do precapillary sphincters influence blood flow?
* Relax = increased blood flow
* Constrict = reduced blood flow
* Controlled by local metabolic conditions and signals
41
What are hypertension and hypotension?
* Hypertension: abnormally high BP, increases cardiac workload
* Hypotension: abnormally low BP, may reduce perfusion of tissues
42
What is the formula for Mean Arterial Pressure (MAP)?
MAP = Diastolic + (1/3 × Pulse Pressure)
* Pulse Pressure = Systolic – Diastolic
* Normal BP = 120/80 mmHg
43
How is MAP (Mean Arterial Pressure) determined?
MAP = CO × TPR
* CO = Cardiac Output = HR × SV
* TPR = Total Peripheral Resistance (mainly arteriolar diameter)
44
What are baroreceptors and how do they regulate BP?
* Stretch-sensitive receptors in aorta and carotid arteries
* ↑BP → ↑baroreceptor firing → ↑parasymp (↓HR), ↓symp (vasodilation)
↓BP → ↓baroreceptor firing → ↑symp (↑HR, vasoconstriction)
45
What are the roles of the cardioacceleratory and cardioinhibitory centers?
* Cardioacceleratory: ↑HR and contractility via sympathetic NS
* Cardioinhibitory: ↓HR via parasympathetic NS
* Both are part of the medulla oblongata
46
How do ADH and Angiotensin II regulate blood pressure?
* ADH: Released due to ↓blood volume; causes vasoconstriction & ↓water loss at kidneys
* Angiotensin II: Stimulates thirst, vasoconstriction, aldosterone, and ADH release
47
What are the effects of erythropoietin (EPO) and atrial natriuretic peptide (ANP)?
* EPO: ↑RBC production in response to ↓O₂ or ↓renal blood flow
* ANP: ↓BP by promoting Na⁺ and water excretion, inhibiting ADH/aldosterone, and vasodilation
