SISTEMA CIRCULATORIO:

FUNCIONES PRINCIPALES

• Transporte y distribución de O2 y CO2,

sales, nutrientes, metabolitos, hormonas,

células inmunes y Acs.

• Producción de ultrafiltrado renal.

• Regulación de temperatura corporal.

• Comunicación humoral (hormonas, factores

inmunes).

Sistemas abiertos

- Corazón, arterias, válvulas

- Hemocele (30% vol. corporal)

- Baja presión (4-10 mmHg)

Sistemas cerrados

- Corazón, arterias, capilares, venas, válvulas

- Sangre (5-10% vol. corporal)

- Alta presión (100 mmHg)

PUMP

DISTRIBUTING

TUBULES THIN

VESSELS

COLLECTING

TUBULES

reservorio de PRESIÓN

reservorio de VOLUMEN

Sistemas cerrados

VEINS

CAPACITY

VESSELS

HEART

80 mmHg 120 mmHg

SYSTOLE

DIASTOLE

ARTERIES (LOW COMPLIANCE)

CAPILLARIES

Sistemas cerrados

Un sistema complicado

Que se puede simplificar

SERIES AND

PARALLEL CIRCUITS

PULMONARY

CIRCULATION

1. LOW RESISTANCE

2. LOW PRESSURE

(25/10 mmHg)

SYSTEMIC

CIRCULATION

1. HIGH RESISTANCE

2. HIGH PRESSURE

(120/80 mmHg)

PARALLEL

SUBCIRCUITS

UNIDIRECTIONAL

FLOW

Structure

of the

heart

SINCITIO

conexión mecánica

y eléctrica

Cardiac muscle

SINCITIO

conexión mecánica

y eléctrica

CÉLULAS MARCAPASO Y SUS FRECUENCIAS

Na+

K+ Na+

K+

-70 mV

RESTING

THRESHOLD

-0

Gradually increasing PNa

AUTOMATICITY

POTENCIAL MARCAPASOS

- Canales de fuga para Na+ (If) abiertos a Vm ~ -60 mV (PNa+ >> PK+)

- Vm ~ -40 mV, despolarización rápida por Ca+ (insensible a TTX)

- Canales de K+ retrasados open to start repolarization and close Ca2+ channels, then

close themselves to allow next pacemaker potential to start.

POTENCIAL DE ACCIÓN CARDÍACO

2 — PK and PCa

3a

3b

a slow K+ channels open b fast K+ channels reopen; Ca2+ channels close

PK and PCa

— PK/PNa ≈ 100 (higher than in axon, so Vm)

"delayed rectifier"

channels

Initial spike of PNa involves

fast Na+ channels (as in

axons). Late, low level of

PNa is because slow Ca2+

channels have a small

permeability to Na+.

(Initial PNa spike is shown

as lasting far too long on

this time scale; it should

be only a few msec.)

Changes in PK result from

depolarization's effects on

at least two types of K+

channels, one that closes

shortly after the PNa spike

and one that opens much

later and very slowly. Fast K closes Slow K opens

Fast K reopens

("Delayed rectifier")

In cardiac muscle, the action potential — and therefore

the refractory period — lasts almost as long as the

complete muscle contraction, so no tetanus, or even

summation, is possible. Sequential contractions are at

the same tension, though gradual increases and

decreases occur with autonomic nervous system input.

PACEMAKERS (in order of

their inherent velocity)

• Sino-atrial (SA) node (0.8 m/s)

• Atrio-ventricular (AV) node (0.05 m/s)

• Bundle of His (5 m/s)

• Bundle branches (5 m/s)

• Purkinje fibers (5 m/s)

Conduction of pacemaker potential from nodal tissue to adjacent

contractile cells and beyond, through gap junctions in intercalated disks.

Increased open probability

Acetylcholine

(muscarinic)

Gi protein –

Ca2+ signaling in cardiac muscle

DHPR

(DHPR)

Ca2+

Entry of Ca2+ during

action potential

1 Ca2+ out

for 3 Na+ in

Inhibited by digitalis & ouabain;

indirectly Na+/Ca2+ exchange

[Ca2+]in

Affected by epinephrine () and ACh ()

Electrocardiograma

Suma de la actividad

eléctrica en el corazón

AV NODE AND AV BLOCKS

FOCUS ON N REGION

NORMA

L

ECG

1ST DEGREE

PROLONGUED AV

CONDUCTION TIME

2ND DEGREE

1/2 ATRIAL IMPULSES

CONDUCTED TO VENTRICLES

3RD DEGREE

VAGAL MEDIATION

IN N REGION/COMPLETE

BLOCK

Systole — contraction of ventricles (systolic P = peak pressure

per heartbeat in major systemic arteries)

Diastole — relaxed filling of ventricles (diastolic P = lowest pressure

per heartbeat in major systemic arteries)

First heart sound (lub) — sound of atrioventricular valves closing

as ventricles start contracting

Second heart sound (dup) — sound of semilunar valves closing

as ventricles stop contracting and ventricular pressure

drops below pressure in the major arteries

Pulse pressure (PP) — systolic P - diastolic P

Mean arterial pressure (MAP) — diastolic P + 1/3 PP

Stroke volume (SV) — vol. at end of diastole - vol. at end of systole;

usually ~70 ml ( = ~130 ml - ~60 ml )

Cardiac output (CO) — heart rate (HR) x SV

CO can increase by a factor of 6 or more, initially due to

HR & SV; at higher CO, increase is mostly due to HR.

EDV

ESV

Gasto cardíaco = volumen sistólico x frecuencia cardíaca

Volumen Sistólico - presión venosa

- presión auricular

- distensión ventricular

- FC

Respuesta al ejercicio

- volumen sistólico constante

- estimulación simpática

FC, vel. llenado ventricular

Un poco de física

VELOCITY = DISTANCE / TIME

V = D / T

FLOW = VOLUME / TIME

Q = VL / T

VELOCITY -FLOW- AREA

V = Q / A

ÁREA SECCIONAL Y VELOCIDAD

Q=10ml/s

A= 2cm2 10cm2 1cm2

V= 5cm/s 1cm/s 10cm/s

V = Q / A

a b c

TIPOS DE CAPILARES

músculo, tejido nervioso, pulmones

riñón, intestinos, glándulas endócrinas

hígado, médula ósea, bazo, nódulos l.

CAPILLARIES

• Pressure inside is 35 to 15 mmHg

• 5% of the blood is in capillaries

• exchange of gases, nutrients, and wastes

• flow is slow and continuous

RETORNO VENOSO: BOMBA MUSCULOESQUELÉTICA

Distribution of Blood in the

Circulatory System

• 67% IN THE SYST. VEINS/VENULES

• 5% IN THE SYSTEMIC CAPILLARIES

• 11% IN THE SYSTEMIC ARTERIES

• 5% IN PULMONARY VEINS

• 3% IN PULMONARY ARTERIES

• 4% IN PULMONARY CAPILLARIES

• 5% IN HEART ATRIA/VENTRICLES

CARDIOVASCULAR

SYSTEM

HEART

(PUMP)

VESSELS

(DISTRIBUTION SYSTEM)

RE

GU

LA

TIO

N

AUTOREGULATION

NEURAL

HORMONAL

RENAL-BODY FLUID

CONTROL SYSTEM

INCREASING HEART RATE

INCREASES CONTRACTILITY

Normal

Heart Rate

Ca++ Ca++

Fast

Heart Rate Ca++ Ca++ Ca++ Ca++

Regulation of Cardiovascular System

Overview-

Regulation of Cardiovascular System

Overview-

HORMONAL REGULATION

• Epinephrine & Norepinephrine

– From the adrenal medulla

• Renin-angiotensin-aldosterone

– Renin from the kidney

– Angiotensin, a plasma protein

– Aldosterone from the adrenal cortex

• Vasopressin (Antidiuretic Hormone-ADH)

– ADH from the posterior pituitary

HYPERTENSION (140/90 mmHg)

Secondary Hypertension (10%) [e.g., Pheochromocytoma]

Essential Hypertension (90%) - Normal cardiac output - Cardiac hypertrophy [left ventricle] - “Resetting” of the baroreceptors - Thickening of vascular walls

ARTERIAL PRESSURE-URINARY OUTPUT THEORY Hypertension causes thickening of vascular walls NEUROGENIC THEORY Thickening of vascular walls causes hypertension

TREATMENT: Reduce stress Sympathetic blockers Low sodium diet Diuretics

RESPONSE TO HEMORRHAGE

• Sympathetic tone via baroreceptor reflex

– Heart rate and contractility

– Venoconstriction ( MCP)

– Vasoconstriction ( arterial BP & direct blood to

vital organs)

• Restore Blood Volume

– Capillary fluid shift ( BP favors reabsorption)

– Urinary output ( Arterial BP, ADH, Renin-

Angiotensin-Aldosterone)

• Restore plasma proteins & hematocrit

CARDIAC FAILURE CAUSES: Impairment of electrical activity Muscle damage Valvular defects Cardiomyopathies Result of drugs or toxins

PROBLEM: Maintaining circulation with a weak pump

( Cardiac output & cardiac reserve; RAP)

SOLUTIONS: Sympathetic tone via baroreceptor reflex - Heart rate and contractility

-Venoconstriction ( MCP) -Vasoconstriction ( Arterial BP) Fluid retention ( MCP) -Capillary fluid shift -ADH -Renin-angiotensin-aldosterone

MEASURING BLOOD PRESSURE

TURBULENT FLOW

1. Cuff pressure > systolic blood pressure--No sound.

2. The first sound is heard at peak systolic pressure.

3. Sounds are heard while cuff pressure < blood pressure.

4. Sound disappears when cuff pressure < diastolic pressure.

Blood pressures

and the vascular

system

Arterial

Pressure-

Venous Pressure-

MEASUREMENT OF CARDIAC OUTPUT

THE FICK METHOD:

VO2 = ([O2]a - [O2]v) x Flow

Flow = VO2

[O2]a - [O2]v

Spirometry (250 ml/min)

Arterial Blood (20 ml%) Pulmonary Artery Blood (15 ml%)

CARDIAC OUTPUT

PERIPHERAL

BLOOD FLOW

VENOUS RETURN

PULMONARY BLOOD FLOW

CARDIAC OUTPUT (Q) = VO2

[O2]a - [O2]v

250 ml/min

20 ml% - 15 ml% =

= 5 L/min

.

Q = HR x SV .

SV = Q

HR

.

= 5 L/min

70 beats/min

= 0.0714 L or 71.4 ml

CARDIAC INDEX = Q

m2 body surface

area

.

5 L/min

1.6 m2 =

= 3.1 L/min/m2