Week 23 Flashcards

Question

What are the different types of capillaries features?

Answer 1

Capillaries: small. High resistance, BP low Continuous Capillaries: - Most common - Continuous. Gaps only between endothelial cells (tight junctions) - CNS, lungs, muscle tissue, skin Fenestrated Capillaries: - Pores of 70-100nm in the capillary wall - Choroid plexus, kidneys, endocrine glands, villi and ciliary processes of the eye Sinusoid Capillaries: - Wider gaps in the vessel walls (Lets blood cells through) - Bone marrow, endocrine glands, placenta

Answer 2

Continuous Capillaries Fenestrated Capillaries Sinusoid Capillaries

Answer 3

Under less pressure Less smooth muscle (less resistance) Stretchy (high capacitance vessels) Larger veins have valves to prevent blood flowing backwards.

Answer 4

8-100µm in diameter, more porous than arterioles. Capillaries drain into venules Continued loss of BP, almost 0 by the time it gets to the vena cava. Resistance is key.

Answer 5

Veins and Venules

Answer 6

Vein = 65% Arteries = 13% Arterioles = 2% Capillaries = 5% Central blood volume = 15%

Answer 7

Vein = 54% Arteries = 10% Arterioles = 1% Capillaries = 5% Central volume = 30% * 12% in heart * 18% in lung In the supine position there is: - Less blood in peripheral veins - More blood in central volume

Answer 8

Pulmonary Circulation (RHS) Systemic Circulation (LHS) Coronary Circulation (from aorta)

Answer 9

Positioned towards back of the heart. Crescent shaped Blood in through Venae cavae Back out through pulmonary artery

Answer 10

At front and apex More circular (thicker walls) In through pulmonary veins Out through Aorta to aortic arch

Answer 11

L and R Coronary arteries from the base of the aorta. Shut during contraction Coronary arteries branch to supply the heart Arteries supply the capillaries for gas and nutrient transfer before draining into the veins

Answer 12

One complete heart beat

Answer 13

Contraction. (Generally taken to mean ventricular contraction and ejection

Answer 14

Relaxation. Or the rest of the cycle: ventricular relaxation and filling

Answer 15

- Atrial contraction (Atria at systole) - Isovolumetric contraction (Ventricles at systole) - Ventricular ejection (Ventricles at systole) - Isovolumetric relaxation - Ventricular filling

Answer 16

At a heart rate of 75bpm, each whole cardiac cycle lasts 0.8 second. The whole heart is in diastole for 0.4 seconds, atrial systole lasts 0.1 seconds and ventricular systole lasts 0.3 seconds

Answer 17

Diastole doesn't occur for long enough for the heart to fully fill with blood, therefore less is released into arteries after this.

Answer 18

4 sounds, only 2 are loud enough to be heard (auscultation) First heart sound ('LUBB')– turbulence caused by closure of the AV valves (happens when the ventricles contract) Second heart sound ('DUPP') – turbulence caused by semilunar valves closing (when the ventricles stop contracting) 3rd and 4th sounds from ventricular filling and atrial systole. 4th Sound audible when ventricles are stiff (helps with diagnosis of conditions)

Answer 19

Atria contract, squeezing blood into the ventricles, through the valves. AV valves open. Pulmonic and Aortic closed Slight increase in atrial pressures End Diastolic Volume = Ventricular Vol + Atrial Contribution (10% at rest) 105ml +25ml = 130ml

Answer 20

All valves closed. Beginning of systole. Increase in intraventricular pressure from contraction. Heart shape change but no blood is ejected. Pushes AV valves closed. First sound

Answer 21

AV valves closed , others open. When intraventricular P is higher than the aortic and Pulmonary P, the valves open and blood is ejected. Atria continue to fill.

Answer 22

L: LVP exceeds aortic P of 80mm/Hg for SL valves to open and ejection. P increase to 120mm/Hg R: RVP exceeds pulmonary P of 20mm/Hg for SL valves to open and ejection. P increases to 25-30mm/Hg

Answer 23

Aortic and pulmonary valves stay open and AV valves stay closed. No movement of blood Ventricular muscle relaxation. Ventricular P decreases slightly but blood still leaves the heart (kinetic energy). Atrial P increasing as atria continue to fill

Answer 24

Valves close ( Heart sound 2). Aortic first, then pulmonic valve. Ventricle volume remains the same as valves are closed (dicrotic wave). Atrial pressure and volume increase from venous return End Systolic Volume = volume remaining in the ventricles after ejection Ie ESV = (EDV)130ml – 70ml = 60ml

Answer 25

AV valves open. Aortic and pulmonary valves close. Ventricular filling. Relaxation phase (still.) Amount of filling decreases when HR increases. Atrial P falls Third sound (not usually audible without specialist equipment)

Answer 26

Difficult to distinguish these phases. When filling is nearly finished , ventricles at full stretch so P rises. P in large vessels drops as blood flows into circulation

Answer 27

SV = End-diastolic vol (EDV) – (ESV) End-systolic vol EDV: Amount of blood collecting in ventricle (~130ml) Related to filling time and rate of venous return ESV: amount remaining after contraction (~60ml) Preload, Contractility, Afterload

Answer 28

Stroke volume (mL/beat) x Heart rate (beats/min) = Cardiac Output (mL/min)

Answer 29

Neural control: physical or emotional stress Sympathetic nervous system stimulates heart rate (SA node). Up to 100-200% Parasympathetic nervous system steadies HR

Answer 30

ion levels: Calcium: too little: weak. Too much: long contractions Potassium: involved in muscle contraction and nerve conduction.

Answer 31

Frank Starlings law: bigger SV ejected if there is a larger degree of filling at the end of diastole.

Answer 32

When the rate at which blood flows into the heart from the veins changes, the heart automatically adjusts its output to match the inflow If an increase in end-diastolic volume occurs, the force of ventricular contraction rises, producing an increase in stroke volume and cardiac output Stretching of muscle fibres increases contraction force and ejection

Answer 33

The more the heart fills with blood, the more the muscle is stretched. Exercise increases venous return via: - Rapid breathing forcing reoxygenated blood into heart quicker - Skeletal muscle pump forcing venous return

Answer 34

The higher the arterial pressure, the lower the stroke volume Arteries are elastic to keep BP stable and absorb volume. If arteries are blocked it increases the amount of force (P) needed to move blood.

Answer 35

The more forcefully the muscle contracts, the more blood is expelled 1.Ions like Ca and K affect muscle activity. 2. Adrenalin and the sympathetic nervous system increase contractility 3. Increased stretch leads to increased contractility

Answer 36

Lack of muscle in veins limits the force of venous return. Contraction of the skeletal muscle in the tissue surrounding the veins compress them. Compression closes upstream valves and opens downstream valves. Compressed veins = increases pressure Venous return increases during exercise

Answer 37

Directly describes the pressure of blood on the wall of the Blood Vessels. It does not describe changes in cardiac pressure during the cardiac cycle

Answer 38

Cardiac Output X Total Peripheral Resistance

Answer 39

- “normal” BP is 120/80 - High is >130/ >85 BUT - Females have lower BP than men - BP increases (/decreases) with age - Children have low BP until adolescence (neonates could be 60/20)

Answer 40

the degree of friction encountered by blood ie the resistance to flow

Answer 41

Constriction or narrowing- initiated by action of the Sympathetic Nervous System or atherosclerosis, or stiffening Increased blood volume (eg increased retention from high NaCl) Viscosity (cold, increased red blood cells)

Answer 42

False! anything increasing CO or PR, increases BP

Answer 43

massively increases as arteries become less stretchy

Answer 44

PP = systolic BP – Diastolic BP ie = 120-80 = 40mm Hg

Answer 45

more useful to work out as this is the pressure at which blood is actually delivered to the tissues MAP = Diastolic Pressure + (Pulse Pressure/3)

Answer 46

Baroreceptors in the Arterial carotids and aortic arch detect pressure change. Each is sensitive to a different pressure. Small changes therefore increase firing frequency A decrease in pressure is also detected (via decreased frequency) due to triggering of the SNS or the PNS, pressure changes are 'fixed'.

Answer 47

1. Peripheral chemoreceptors : carotid bodies in carotid artery. No receptors in veins 2. Central chemoreceptors: medulla Detect changes in PO2, PCO2, pH Low PO2 is associated with changes in pulmonary pressure, so changes in lung stretch receptor activity will also respond to low O2 levels.

Answer 48

Contraction of smooth muscle in the vessel walls, also precapillary sphincters in arterioles Activation of Sympathetic Nervous activity Causes narrowing of the diameter of the blood vessel Increases the resistance of blood vessels to blood flow Increases Blood Pressure

Answer 49

Relaxation of smooth muscle in the vessel walls, also precapillary sphincters in arterioles Causes widening of the diameter of the blood vessel Caused by withdrawal of sympathetic nerve activity and locally released chemicals e.g. nitrous oxide and lactic acid Decreases the resistance of blood vessels to blood flow Decreases Blood Pressure

Answer 50

Counteract the pressure change from getting up too quickly (orthostatic hypotension) Haemorrhage: can cause problems medically Stress or exercise.

Answer 51

Low salt diet ( regulation of blood volume) Decrease stress and effects of sympathetic nervous system Therapeutically with ACE inhibitors- interacting with the Renin Angiotensin Aldosterone System (RAAS) that regulates blood volume and BV constriction.