cardiovascular physiology part 1

Question 1

Cardiac output when stroke volume is normal and heart rate is 100b/m

Answer 1

70ml x 100b/m = 7000mL/m = 7L/m

Question 2

Blood pressure is determined by:

Answer 2

1. Blood volume
2. Effectiveness of the heart as a pump
3. Resistance of the circulatory system to blood flow (viscocity, vessel length and vessel diameter)
4. Relative distribution of blood within the circulation

Question 3

what does Increased diameter of arterioles do to bp?

Answer 3

BP decreases as resistance decreases

Question 4

what does Physical training do to bp?

Answer 4

4 BP decreases as resistance decreases
Physical training: If resting 2. No change or a decrease. Stroke volume increases with cardiac hypertrophy but compensatory decrease HR. Probably less resistance in blood vessels.
If training using large muscle groups, 2 3 & 4. BP will increase. Systolic BP will increase but diastolic BP may decrease. Sympathetic N.S. increases rate and force of contraction but blood vessels in muscles will dilate. If this occurs in many muscles, reduced peripheral resistance will reduce diastolic B.P. Dehydration may contribute to increase BP also.

Question 5

what will a Haemorrhage do to bp?

Answer 5

1. BP decreases as loss of plasma reduces blood volume

Question 6

what will Dehydration which will increased blood viscosity do to bp?

Answer 6

Increased B.P due to increased blood viscosity

Question 7

what will Fear do to bp?

Answer 7

Increased B.P due to Sympathetic stimulation increasing rate & force of contraction & vasoconstriction

Question 8

what will Angiotensin II does

Answer 8

• Increase B.P due to retention of NaCl and water also vasoconstriction .
• acts on cortex of adrenal gland and stimulats secretion of aldosterone. which causes retention of NaCl- leading to water retention and +bp.
• stimulates osmorecptors in hypothalamus- thirst
• acts on hypothalamus to release anti-diuretic hormne

Question 9

what will Arteriosclerosis which narrows blood vessels do to bp?

Answer 9

Increased B.P due to MAP = C.O x resistance

Question 10

how body lowers bp?

Answer 10

An increase in blood pressure is detected by arterial baroreceptors, located in the aorta and carotid artery. These stimulate (1) the cardio inhibitory centre in the medulla, triggering an increase/decrease in sympathetic stimulation and an increase in parasympathetic stimulation causing the heart rate to decrease which reduces cardiac output and therefore lowers BP. Also, an decrease in MAP will elevate ventricular after-load, reducing SV by increasing ESV – this will lower cardiac output.
They also stimulate (2) the vasomotor centre triggering an decrease in sympathetic stimulation to blood vessels, vasodilation and an decrease in systemic vascular resistance. This will lower blood pressure

Question 11

how body increases bp?

Answer 11

A decrease in blood pressure is detected by arterial baroreceptors, located in the aorta and carotid artery. These stimulate (1) the acceleratory centre in the medulla, triggering an increase in sympathetic stimulation and an decrease in parasympathetic stimulation causing the heart rate to increase which increases cardiac output and therefore increases BP. They also stimulate (2) the vasomotor centre triggering an decrease in sympathetic stimulation to blood vessels, vasoconstriction and an increase in systemic vascular resistance. This will increase blood pressure.

Question 12

direct renal mechanism

Answer 12

independently alter blood volume. Only helps decrease fluid volume. Does this by increasing how much fluid glomular cappillaries filter, then this exits body in urine.

Question 13

indirect renal mechanism- juxtamedullary nephrons

Answer 13

Juxtaglomerular apparatus of the kidney monitors blood pressure. Renin is released into circulation in response to lower BP, this converts angiotensinogen into Angiotensin 1 – this is converted into Angiotensin 2 by the ACE found in most capillary endothelial cells, notably in the vascular endothelium of the lungs. Angiotensin 2 triggers
1. vasoconstriction (increasing /decreasing BP),
2. release of aldosterone from adrenal cortex – this promotes tubular Na+ reabsorption and water retention, increasing plasma volume.
3. release of ADH form posterior pituitary – this acts on collecting ducts of the kidney to increase/decrease
water absorption from the remaining filtrate (which also increases plasma volume).

Question 14

2 types of cells comprising juxtamedullar complex

Answer 14

Macula densa cell- chemoreceptors that monitors NaCL content

granular cells-within afferent arteriole wall as a mechanoreceptor and detect bp in arterioles.

Question 15

sinus rhythm

Answer 15

60-100

Question 16

sinus bradycardia

Answer 16

less than 60

Question 17

sinus tachycardia

Answer 17

+100 - 150-180

Question 18

supra-ventrricular tachycardia

Answer 18

+150

Question 19

atrial fibrillation

Answer 19

irregularly irregular from 50-150

Question 20

ventricular fibrillation

Answer 20

grater than 150

Question 21

heart block

Answer 21

40-60.

Question 22

what part of brain controls heart

Answer 22

medulla oblongata.

Question 23

sympathetic nervous system control is initiated from…..

Answer 23

cardiacacceleratory center within medulla oblongata.It sends message to release Norepinephrine (NE) onto β1 adrenergic receptors (β1) shaped like ꓴ.

Question 24

parathympathetic ns control initiated from….

Answer 24

cardioinhibitory center. sends message to Short parasympathetic fibres to release acetylcholine (ACh) to act on cholinergic (muscarinic type) receptors (ꓴ) in the:
SA node
AV node
Heart muscle
Heart rate slowed through action of acetylcholine (ACh)

Question 25

preload

Answer 25

exercise increases filling time of ventricles which means hr is slower so more blood goes into muscles with each heart beat

Question 26

contractility

Answer 26

increases in sympathetic ns activity increases contractility due to the action of norepinphrine encouraging more ca+ ions to enter myocardial cells. so more blood is ejected from heart.

Question 27

afterload

Answer 27

in healthy people sv and constant afterload is not a problem.
however people with high bp, as afterload decreases the less blood is ejected by ventrices. This means blood stays in heart after systole so esv and sv increases.

Question 28

baroreceptors

Answer 28

• located in aortic arch, carotid sinuses (within internal carotid arteries).
• action- stretched in response to raised arterial bp
• inhibits vasomotor and cardio-accelratory center
• vasodilation and decreased hr, contractile force and bp.

Question 29

Coronary circulation

Answer 29

Oxygenated blood supplied to heart muscle
Delivered when heart relaxed in diastole
L) ventricle receives most of the coronary blood supply
L) and R) coronary arteries are located at the base of the aorta and above the aortic valve
Coronary arteries branch and become coronary capillaries then coronary veins
Coronary veins merge on posterior into the coronary sinus
Coronary sinus empties into R) atrium
Some anterior cardiac veins empty anteriorly into R) atrium

Question 30

Relevance of the intrinsic conducting system

Answer 30

Contains non-contractile cardiac cells that are:
autorhythmic cardiac pacemaker cells
pacemaker cells spontaneously depolarise and initiate heart rate
pacemaker potentials spread via the intrinsic conducting system throughout the heart triggering rhythmic contractions of typically 75 bpm (normal range 60 - 100 bpm)

Question 31

Pacemaker and action potentials of cardiac pacemaker cells

Answer 31

1. Pacemaker potential – K+ ion channels close and Na+ ion channels open. The interior of pacemaker cells becomes more positive.
2. Depolarisation – threshold -40 mV achieved, and Ca2+ ions rush into the SA node, and action potential initiated. Depolarisation of the action potential across both atria occurs, before both atria contract. Impulse delayed briefly at the AV node. Ventricular depolarisation begins at the apex and sweeps upward before ventricular contraction.
3. Repolarisation - Ca2+ channels become inactive, and K+ channels open with efflux of K+ ions. The membrane potential of the pacemaker cells returns to resting voltage of approximately -60 mV. (Atrial repolarisation occurring during ventricular depolarisation). Ventricular repolarisation begins at the apex and travels upward across both ventricles.