• deoxygenated blood enters vena cava
• right atrium
• tricuspid valve
• right ventricle
• pulmonic valve
• pulmonary arteries
• lungs
• oxygenated blood to pulmonary veins 
• left atrium
• mitral valve
• left ventricle
• aortic valve
• aorta

Transportation

• perfusion(blood to tissue)
• provide oxygen to the tissue
• transport nutrients to the tissue
• remove wastes from the tissue

control flow into capillaries

contain smooth musc.

• alpha 1 receptors

sympathetic stimulation

  -receptors on precapillary arterioles

  -A1 stimulation causes peripheral vasoconstriction

Na+ channels open, Na+ rushes in.

Inside of cell becomes more positive

Plataeu Phase

-Slow channels remain open

-Ca^{2+ and} Na+ continue to move into cell

Na+ channels close, K+ channels open

K+ rushes out, leaving cell more negative

-Cardiac cells dont need nerves to tell them to depolarize

-Naturally leaky cells

-Na+ slowly leaks in ->cell slowly becomes more + until it depolarizes

Sinoatrial node (SA) (right atrium)

Atrial depolarization

-pace maker

atrioventricular Node (Delay)

Bundle branches ->Purkinje fibers in apex

ventricular depolarization

P Wave: atrial depolarization

QRS Complex: ventricular depolarization

T Wave: ventriclar repolarization

-Period when no matter how strong the stimulus, the cell cant depolarize again

-There is no resting potential

Period when cell may depolarize again is there is a strong enough stimulus

ex) rat vs mouse on a trap

provides neural and hormonal stimuli wheich speed or slow the heart from its normal automatic rate

sympathetic or parasympathetic

-Speeds the heart through hormones

-Epinephrine and Norepinephrine. Receptors for these are called adrenergic receptors

Slows the heart via neural influence

-vagus nerve

-neurotransmitter: ACh

Rest and restore system

Increases intestinal blood flow

Bronchi constriction

in the heart

increase rate

increase strength of contraction

-Located in smooth musc surrounding vessels in musc and terminal bronchioles in the lungs

-Causes smooth musc to relax. Vasodilation in musc. Bronchodilation

-In smooth musc surrounding vessels in skin and GI tract

-Stimulation causes contraction->vasoconstriction

-shunts blood away

-Selectivity (decreases side effects)

ex) nonselective ß agonists: used to dilate bronchioles, can cause tachycardia. Epinephrine

nonselective ß antagonists: used to slow the heart, side effect is bronchoconstriction. Propranolol

Adrenergic antagonists produce symptoms that look like parasympathetic signs

-slowing of the heart

-bronchoconstriction

Cholinergic antagonists produce symptoms that look like sympathetic signs

-speeds heart rate

-bronchodilation

Mitral insufficiency- most common

Tricuspid insufficiency

Pulmonary stenosis

Aortic stenosis

-Blood leaks back from left ventricle to the left atrium

-Leads to hypertrophy of the left ventricle

-Systolic murmur heard on the left side

-Fairly common in small dogs, 80% by mid-teens

coughing

exercise intolerance

weight loss

signs of right sided heart failure

Backlog of blood "upstream" from the right heart

-ascites: accumulation of fluid in the peritoneal cavity

-pleural effusion

-liver failure

"sick heart muscle"

thick=hypertrophic

thin=dilated, floppy

-Seen in giant breeds. boxers, dobermans

-Floppy heart ->decreaed contractility

-R or L heart failure signs

-cause unknown, exercise intolerance

-Floppy heart

-Thin ventricular walls

-D.T. taurine deficiency

-Breathing difficulty

-Gallop rhythm-fast

Hypertrophied L ventricle w/o a visable inciting cause

-small lumen. continues to shrink

Uncommon in dogs

Thick walled heart ->cant fill fully

^ heart rate, gallop rhythm

Primary- idiopathic

Secondary

-hyperthyroidism

-hypertension

-renal dz

Thromboemboli common

More common in cats vs dogs

Hardware Dz

Sharp metallic object injested ->rumen ->reticulum ->

penetrates into thorax ->penetrates pericardium ->

myocardium

Mostly dogs

Heart musc. bruised

May lead to ectopic focus or VPC

Clinical syndrome

Clinical signs result from excess fluid retention

L-sided CHF: pulmonary edema

R-sided CHF:ascites, liver failure, pleural effusion