Cardiovascular System: Structure, Function, and Regulation, Lecture notes of Physiology

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CARDIAC FUNCTIONSCARDIAC FUNCTIONS

LEARNING OBJECTIVES

OVERVIEW OF THE FUNCTIONS OF THE CVS

ILLUSTRATE THE OVERALL STRUCTURE OF THE HEART & THE CIRCULATORY SYSTEM

THE CARDIAC MYOCYTE, EXCITATION & CONTRACTION

MODALITY OF INITIATION & NERVOUS CONTROL OF THE HAERT

ELECTROCARDIOGRAPHY AND ARRHYTHMIAS

THE CARDIAC CYCLE: DESCRIPTION OF THE EVENTS THAT OCCUR IN ONE CARDIAC CYCLE

THE HEART AND

ITS SYSTEM OF

VESSELS :

INTO WHICH AND

THROUGH WHICH

THE HEART PUMPS

BLOOD WHICH

CIRCULATES

ROUND THE BODY

THE HEART: CENTRE OF THE SOUL

FUNCTIONS OF THE CVS

 Transportation is by bulk flow system, transporting

 respiratory gases i.e. O 2

and CO 2

 Nutrients (digested food),vitamins, water,

drugs & electrolytes absorbed from the

GIT into the blood stream to tissues.

Metabolites such as urea, creatinine,

excess water & ammonium salts from

tissues to the various excretory organs

Distribution of Hormones from Edg

2tissue

Distribution of heat btw the body core

temperature and its surfaces.

Immune substances

Clotting factors

FUNCTIONS

Generation of adequate pressure to deliver flow

throughout the body under different

circumstances, (rest, exercise & haemorrhage)

Production of hormones. Eg. Atria Natriuretic Peptide

(ANP).

Aids in regulating the water and ionic concentrations

of the tissues.

Key organ of vital autoregulatory homeostatic reflexes

of the body such as baroreceptor & chemoreceptor

feedback reflexes.

Provides the hydraulic mechanism for penile erection

& subsequent ejaculation during reproduction

REVIEW

The Heart is a hollow muscular pump.

Made up of 4 chambers

Its primary function is to pump blood ( a fluid medium).

One heart BEAT consists of one contraction & one

relaxation of the heart.

The Circulatory system is a closed circuit system

with pumps arranged in series & parallel vascular

beds.

Blood pressure & flow are largely controlled by

the Autonomic Nervous System

Structure of the CVS

• (^) Introducing the concepts of
  • in series vs in parallel
  • pressure, resistance and

capacitance

• regional redirection of blood
• fractional distribution of blood

between venules/veins & the rest

The Circulatory System.

WHAT ARE BLOOD VESSELS?

Blood vessels are the tubes through which the

heart pumps blood which circulates round the

tissues of the body & back to the heart.

There are 3 major types of blood vessels:

arteries , capillaries , and veins.

Arteries carry blood away from the heart.

As they move away from the heart, they

branch repeatedly, forming smaller and

smaller arteries and eventually the smallest

arteries – the arterioles

Arteries typically carry oxygenated blood

(except – the pulmonary arteries).

STRUCTURE OF BLOOD VESSELS

3 basic layers or tunics that surround a central

blood-containing space, the lumen.

Capillaries contain only the tunica interna.

Classification of blood vessels

• (^) Elastic arteries eg aorta
  • (^) wide lumen, elastic wall
  • damp pressure variations
• Muscular arteries eg other arteries
  • (^) wide lumen, strong non-elastic wall
  • (^) low resistance conduit
• (^) Resistance vessels eg arterioles
  • (^) narrow lumen, thick contractile wall
  • (^) control resistance & therefore flow
  • (^) allows regional redirection of blood
• (^) Exchange vessels eg capillaries
  • (^) narrow lumen, thin wall
• (^) Capacitance vessels eg venules & veins
  • (^) wide lumen, distendable wall
  • low resistance conduit, & reservoir
  • (^) allows fractional distribution of blood

arteries

arterioles

capillaries

venules

veins

aorta

THE HEART

THE HEART

 The heart is a hollow muscular pump that propels blood

which contains oxygen, nutrients, wastes and other

chemicals to the body through the blood vessels

Weight--about 250-350g.

Size about the size of your clinched fist.

Location – mediastinum from 2nd to 5

th

LT

intercostal space, in-between the lungs, anterior

to vertebral column and posterior to sternum.

Base - broad superior portion of heart

Apex –Inferior end tilts to the left & tapers to

point