Human physiology exam 3

cardiovascular physiology

the cardio vascular system, is a series of tubes ___ filled with fluid ____ and connected to a pump ____.

vessels, blood, heart

materials entering the body

oxygen, nutrients, and water

materials moved from cell to cell

wastes, immune cell, antibodies, clotting proteins, hormones, stored nutrients

materials leaving the body

metabolic wastes, heat, and carbon dioxide

Heart

one way closed circuit

gas, nutrients, waste

pump

pressure goes high to low

aorta, arteries, arterioles, capillaries, venules, veins, venae cavae

pressure

the force exerted by the fluid on its container. friction causes a pressure drop.

hydrostatic pressure

pressure exerted with no fluid movement. proportional to the height of the water column.

as the radius of a tube decreases

the resistance to flow increases

pericardium

heart encased within a membranous fluid-filled sac called the

atrial ventricular (AV) valves

tricuspid- right

Mitral/ bicuspid- left

semilunar valves

pulmonary artery

aorta

• main purpose is to prevent back flow

ventricular contraction

AV valves remain closed to prevent blood flow backward into the atria

ventricular relaxation

semilunar valves prevent blood that has entered the arteries from flowing back into the ventricles.

where does the electrical signal come from to initiate contraction in the heart? (myocardial contraction)

autorhythmic cells the medulla controls

cardiac muscles vs skeletal muscles

• smaller and have single nucleus per fiber

• have intercalated disks

• desmosomes allow force to be transferred (strong connections that tie cell together)

• gap junctions provide electrical connection ( allows depolarization to spread rapidly from cell- cell)

• T- tubules are larger and branch

• sarcoplasmic reticulum is smaller

• mitochondria occupy one-third of cell volume (very high energy demand, consumes roughly 70-80% of oxygen delivered)

cardiac muscle contraction

• can be graded by calcium concentration

• sarcomere length affects force of contraction

• action potentials vary according to cell type

• a lot of calcium stronger contraction

• bridges between actin and myosin affects contraction

skeletal muscle

• stable at -70 mv

• net na+ entry through ACh-operated channels

• rising phase of action potential: Na+ entry

• Rapid; caused by K+ efflux

• hyperpolarization; leak of K+ and Na+ restores potential to resting state

• duration of action potential; 1-2 msec

• refractory period; brief

contractile myocardium

• stable at -90 mv

• depolarization enters via gap junction

• rising phase of action potential: Na+ entry

• repolarization phase; extended plateau caused by ca2+ entry; rapid phase caused by K+ efflux

• hyperpolarization; non

• duration of action potential; extend 200+ msec

• refractory period; long

autorhythmic myocardium

• unstable pacemaker potential starts at -60 mv

• net Na+ entry through If channels; reinforced by ca2+ entry

• rising phase of action potential; ca2+ entry

• repolarization phase; normally none

• duration of action potential; variable generally 150+ msec

• refractory period; none

electrical conduction in the heart

SA node, internodal pathways, AV node, Av bundle, bundle branches, purkinje fibers

AV node

• routes the direction of electrical signals

• delays the transmission of action potentials

SA nodes

• sets the pace of the heartbeat at 70 bpm

• AV node (50 bpm) and purkinje fibers (25-40 bpm) can act as pacemakers under some conditions

p wave

atrial depolarization

QRS

ventricular depolarization; also includes atrial repolarization (relaxation)

T wave

ventricular repolarization

Heart rate normal

60-100 bpm

• train atheletes may have a slower rate

abnormal heart rate

• tachycardia - fast

• bradycardia- slow

• arrhythmia- irregular

mechanical events

1. late diastole- both sets of chambers are relaxed and ventricles fill passively (heart at rest)

2. atrial systole- atrial contraction forces a small amount of additional blood into ventricles

3. isovolumic ventricular contraction- first phase of ventricular contraction pushes AV valves closed but does not create enough pressure to open semilunar valves (lub)

4. ventricular ejection- as ventricular pressure rises and exceeds pressure in the arteries, the semilunar valves open and blood is ejected

5. isovolumic ventricular relaxation- as ventricles relax, pressure in ventricles fall, blood flows back into cusps of semilunar valves and snaps them closed. (dub)

stroke volume

• amount of blood pumped out by one ventricle during a contraction

• EDV( 135) - ESV (65) = stroke volume (70)

• Frank- starling law states - stroke volume increases as EDV increases

• EDV is affected by venous return

• venous return affected by- skeletal muscle pump, respiratory pump, and sympathetic innervation ( change force of contraction changes volume)

• force of contraction is affected by stroke volume

• length of muscle fiver and contractility of heart

cardiac output

• volume of blood pumped by one ventricle in a given period of time

• CO = HR x SV

• average = 5 L/min

autonomic neurotransmitters alter heart rate

catecholamines modulate cardiac contraction

stroke volume and heart rate determine cardiac output

functional model of the cardio vascular system

capillaries

• smallest vessel

• site of exchange

• lack smooth muscle and elastic tissue reinforcement, which facilitates exchange through a layer of endothelium

• precapillary sphincters- constrict and prevent flow

elastic recoil in arteries

contraction

1. ventricle contracts

2. semilunar valve open

3. aorta and arteries expand and store pressure in elastic wall

relaxation

1. isovolumic ventricular relaxation

2. semilunar valves shut, preventing flow back into ventricle

3. elastic recoil of arteries sends blood forward into rest of circulatory system

hypertension

systolic >140 and diastolic >90

pre-hypertension

systolic-120-139 and diastolic- 80-89

blood pressure

pulse pressure= systolic p- diastolic p

MAP= diastolic P +1/3(systolic p-diastolic p)

• mean arterial pressure is a function of cardiac output and resistance in the arterioles

• blood pressure control includes rapid responses from the cardiovascular system and slower responses by the kidneys

factors that influence mean arterial pressure

arteriolar resistance

• arteriorlar resistance is influenced by both local and systemic control mechanisms

• local control- based on mediated by CNS

• hormones- control salt and water balance through kidney

chemicals mediating vasoconstriction

• norepinephrine; (alpha-receptors) ,baroreceptor reflex, sympathetic neurons, neurotransmitter

• endothelin; paracrine mediator, vascular endothelium, paracrine

• vasopressin; increases blood pressure in hemorrhage, posterior pituitary, neurohormone

• angiotensin II; increases blood pressure, plasma hormone, hormone

chemicals mediating vasodilation

• epinephrine (b2); increase blood flow to skeletal muscle, heart, liver, adrenal medulla, neurohormone

• acetylcholine; erection flex, parasympathetic neurons, neurotransmitter

• nitric oxide; paracrine mediator, endothelium, paracrine

• bradykinin (via NO); increases blood flow, multiple tissues, paracrine

• adenosine; increases blood flow to match metabolism; cell metabolism; paracrine

• histamine; increases blood flow, mast cells, paracrine

• natriuretic peptides; reduce blood pressure; atrial myocardium, brain, hormone, neurotransmitter

• vasoactive intestinal peptide; digestive secretion, relax smooth muscle, neurons, neurotransmitter, neurohormones

arteriorlar resistance

• myogenic autoregulation (sm. muscle contraction influenced by blood pressure)

• paracrines- active hyperemia ( low o and high co2; dialation, high blood flow) - reactive hyperemia ( period of low perfusion)

• sympathetic control- sns; norepinephrine, adrenal medulla; epinephrine

active hyperemia

• more activity more blood flow

• paracrine signal causes vasodilation

reactive hyperemia

reactive rebound

Reactive hyperemia is a temporary surge in blood flow after a blockage is removed

o2 drops and metabolites build up

distribution of blood

85% in the liver and digestive tract, kidneys, and skeletal muscle

continuous capillaries

• most common, continuous

• pass smaller molecules

• found in the muscle, con tissue, blood brain barrier

fenestrated capillaries

• associated with pores

• pass larger molecules and volumes

• found in the kidney and intestine

capillary exchange

• exchange between plasma and interstitial fluid occurs by paracellular pathway (between cells) or endothelial transport (through cells)

• small dissolved solutes and gasses move by diffusion

• larger solutes and proteins move by vesicular transport

• diffusion rate determined by concentration gradient

• bulk flow; mass movement as a result of hydrostatic or osmotic pressure gradients

• absorption; fluid movement into capillaries- net absorption on venous end

• filtration; fluid movement out of capillaries- caused by hydrostatic pressure, net filtration at arterial end

• net pressure= hydrostatic pressure- colloid osmotic pressure

lymphatic system

• returning fluid and proteins to circulatory system

• picking up fat absorbed and transferring it to circulatory system

• serving as filter for pathogens

edema

two causes

• inadequate drainage of lymph

• filtration far greater than absorption

disruption of balance between filtration and absorption

• increase in hydrostatic pressure

• decrease in plasma protein concentration

• increase in interstitial proteins

baroreceptors

BP goes down- less firing (carotid and aortic)

SA node change heart rate (parasympathetic)

BP goes up-more firing (carotid and aortic)

response to high blood pressure

response to low blood pressure

CVS; Risk factors

• not controllable

-sex

-age

-family history

• controllable

-smoking

-obesity

-sedentary lifestyle

-untreated hypertension