Chapter 14 Cardiac Output

Regulation of blood volume

- ADH hormone - aldosterone

Mean Arterial Pressure

- Average pressure driving blood forward into tissues throughout cardiac cycle - diastolic + 1/3(systolic-diastolic) - CO X total peripheral resistance

- Short term control of mean arterial pressure

- Baroreceptors -JUST IN ARTERIES

Sympathetic activity

- Contractility -Ejecting blood forcefully out of the ventricles. What symp does= increases contraction of ventricles - Symps increase the amount of Ca in the SR so can increase cross bridge which increases the force

How does Movement of substances across capillary endothelium occur??

- Diffusion-pores in endothelium: gases, fluids or electrolytes - vesicular transport - active transport: ions glucose and amino acids - bulk flow

factors that enhance venous return

- Driving pressure from cardiac contraction -sympathetically induced venous vasoconstriction: constrict the veins= increase venous return= CO goes up - Skeletal muscle activity -effects of venous valves

What is stroke volume determined by?

- End diastolic volume (EDV): volume of blood in ventricles before contraction - venous return: where do ventricles get blood? veins just saying how much blood is in each ventricle before beat - Afterload: what heart sees that it has to pump against - and sympathetic activity

Ejection fraction of Cardiac output

- Fraction of blood pumped out with each heart beat - SV/ EDV X 100 -Normal fraction 50-65%

What is cardiac output determined by?

- Heart rate and stroke volume - CO= HR X SV

Systolic pressure

- Maximal arterial pressure - averages= 120 Systolic= higher number

diastolic pressure

- Minimum pressure in arteries when blood is draining off into vessels downstream - Averages= 80 -Diastole= relaxed

Long term control of mean arterial pressure

- Minutes to days - involve adjusting total blood volume: restoring normal salt and water balance through mechanisms that regulate urine output

Cardiac tissue and optimal resting length

- NOT at optimal resting length at rest - muscle that accepts blood and stretches -blood stretches ventricles out

Extrinsic control

- Sympathetic nervous system's main affect on arterioles are vasoconstriction - epinephrine -hormones: Angiotensin II( increase vasoconstrict and vasodiolate) and Vasopressin ( antidiaretic hormone..effect on BP? INCREASES BP)

- functions of lymphatic

- aids in immune system - removal of interstitial fluid and return unidirectionally to heart - absorbs and transports fatty acids

What is heart rate determined by?

- altering balance of parasympathetic and sympathetic influence on SA node - Symp= fight or flight so increases HR -para= decreases HR - Para dominate at rest bc PNS influences the atria slowing down the intrinsic rate

Trained effects

- at rest trained has high stroke volume -at rest no dif in CO bt trained and untrained - resting hr decreases w/ more trained

Stroke volume

- blood pumped per beat - measured in ml/beat

Determinants of resistance

- blood viscosity - vessel length: EX. ppl who become obese, there vessel length has to increase in length - vessel radias: MAIN determinant

define Mean Arteriol pressure

- bp that is monitored and regulated in the body

What alters the radius of vessels?

- changes within other organs -Thus blood flow to organ

- What are changes w/in an organ that change the blood flow to that organ?

- chemical influences on radius: local metabolic changes - Physical influences on radius: application of heat or cold EX: put heat on arm in 10 min arm turns red Vessel wall stretch: when you stretch smooth muscle, it rebounds and contracts

Complications of hypertension

- congestive heart failure: harder to pump bc needs to generate more pressure to overcome all the blood...gets tired of working hard - Stroke -Heart attack -Spontaneous hemorrhage -Renal failure: kidney failure= dialysis 2-3 times a week - retinal damage: eye damage v sensitive

Contractions/ relaxation of sphincters

- contract= reduces blood flow to organ -Relax= increase flood flow

Venous return: skeletal muscle activity

- contraction acts to "pump" veins - increases venous return w increased activity

potential causes for etiology

- defects in salt management by the kidneys - excessive salt intake: someone is "salty"= sensitive - diets low in K and Ca -Excess vasopressrin (ADH which increases BP)

Pulse pressure

- difference bt systolic and diastolic pressure

Types of passive exchanges in capillaries

- diffusion -bulk flow

Blood pressure

- force exerted by blood against a vessel wall: water balloon full= more pressure - depends on: Volume of blood contained w/ in vessel and Compliance of vessel walls= stretchability

Cardiovascular system consists of..

- heart -blood -Vessels: tubing carry blood

Frank- starling law of the heart

- heart pumps what it gets. Increase of diastolic volume= increases stroke volume

What does sump nervous system do to stroke volume?

- increases it

Hypotenstion

- low BP -occurs when too little blood to fill vessels or heart is too weak to drive the blood - orthostatic (postural) hypotensiont

Bulk flow

- mainly used for fluid exchange bt the capillary and tissue -Components: Hydrostatic pressure (force exerted by blood), and Osmotic pressure (due to solute concentration) - osmotic pressure stays the same throughout bc proteins can't get out -arteriole end= net filtration of fluid from blood out - Venous end= net absorption

Baroreceptors

- mechanoreceptors sensing stretch. -Signals sent to medulla - response sent out via ANS - Symp increases heart rate, vasoconstriction - Parasympathetic Decreases heart rate, vasodilatation

Elephantiasis

- mosquito born parasitic worm -invades lymph vessles -BLOCKS lymphatics, so no lymph to pick up excess fluids - interference w/ lymph drainage

Hypertension

- most common - silent killer: bc no symptoms leads to other diseases that can kill you EX: stroke - etiology: primary v secondary

Circulatory shock w/ hypotension

- occurs when BP drops so low that adequate blood flows to the tissues can no longer be maintained

What are capillaries surrounded by?

- precapillary sphincters: they push blood where it wants to go.

Venous Return: venous valves

- prevent back flow of blood

Firing rate of baroreceptors

- proportional to MAP

Causes of edema

- reduces concentration of plasma proteins -increases permeability of capillary wall: gaps get big and let more in -blockage of lymph vessels

Velocity of blood flow in capillaries

- relatively slow for time of good exchange

Afterload

- resistance that heart has to pump against - if after load increases Stroke volume decreases - if tubing is small, heart has to do more work! -

ADH

- secreted by posterior pituitary. - Increases water retention in kidneys - responds to low blood volume and/ or increased blood osmolarity

Aldosterone

- secreted by the adrenal gland: in response to low bp and low blood flow to kidneys - RASS -increases reabsorption of Na

Vessel's radius

- slight change in radius produces significant change in blood flow - R is proportional to 1/R^4

What type of muscle are in arterioles?

- smooth muscle

Edema

- swelling of tissues - accumulation of interstitial fluid

What do arterioles determine?

- the radius of blood vessels -Vasoconstriction= constriction BV to make it smaller -vasodilation: make blood vessels bigger

What is the only steady blood flow?

- to brain

What influences venous return?

- venous return= easier lying down than standing up bc not working against gravity (blood in legs) -So VR higher when lying down bc end product is the same - the CO is the same regardless so one needs to compromise

Cardiac output

- volume of blood ejected by each ventricle each minute

Problems w/ veins?

- when standing= gravity. Faint when knees locked bc flood flow to heart is less, so less blood return to heart. Cardiact output goes down, so blood flow to brain is less. -Veins have increase hydropressure to overcome

Acute Effects of exercise on cardiovascular system

-CO goes up w/ increase in exercise -y? EDV goes up bc increase venous return (which goes up bc skeletal reaction forces blood back) - stroke volume: symp increase stroke volume bc increase venous return - heart rate: goes up bc parasyms dominate at rest...take AWAY para HR goes up

How to measure the flow of blood

-F= P/R -F= flow rate of blood through a vessel - P= pressure gradient - R= resistance of blood vessels (how difficult it is for blood to flow) -EX: Blood flow is proportional to pressure, but reverse of resistance

BP abnormalities

-Hypertension: bp above 140/90 2 broad classes: primary (more common), secondary(EX: kidneys make too much renin, too much blood volume= BP goes up - hypotension

Etiology

-Primary hypertension (vs secondary) - Catchall category for blood pressure elevated by variety of unknown causes rather than by a single diseases entity - potential causes being investigated...

Arteries

-V stretchy - Function: low resistance bc large radius -act as pressure reservoir providing driving force for blood when heart is relaxing

Primary determinants of map

-cardiac output -total peripheral resistance

Lymphatic system

-series of vessels that pick up that extra interstitial fluid. -look like veins - low pressure system -dump back to the blood -distribution of water -carries lymph

What is the determination of MAP?

Arterioles