Cardiac physiology

EMSP 2544 Cardiology
Lesson Two
1
Cardiac Physiology
Galveston College ParamedicGalveston College Paramedic
ClassClass
2015
by Rory Prue

Lesson Two
2
Topics
Nervous Control of the Heart
Hormonal Regulation
Electrolytes
Conductive System

Lesson Two
3
Objectives
Identify the structures of the autonomic nervous
system and their effect on heart rate, rhythm,
and contractility
Identify the structure and course of all divisions
and subdivisions of the cardiac conduction
system
Identify & describe how the heart’s pacemaking
control, rate, and rhythm are determined
List the most important ions involved in
myocardial action potential and their primary
function in this process

Lesson Two
4
Nervous Control

Lesson Two
5
Nervous Control
 Nervous Control
of the Heart
Sympathetic
Parasympathetic
Autonomic Control
of the Heart
Chronotropy
Inotropy
Dromotropy
Role of
Electrolytes

Lesson Two
6
Nervous Control

Lesson Two
7
Nervous Control
Sympathetic and parasympathetic nerve
fibers in atria
Ventricles mainly have sympathetic
nerves

Lesson Two
8
Sympathetic Control
Postganglionic sympathetic fibers release
norepinephrine; have effects on
myocardium:
Inotropic
Dromotropic
Chronotropic

Lesson Two
9
Sympathetic Control
Sympathetic stimulation of the heart
Dilation of coronary blood vessels
Constriction of peripheral vessels
Increased oxygen demands of the heart met
by increase in blood and oxygen supply

Lesson Two
10
Sympathetic Control
Norepinephrine release results from
stimulation of alpha- and beta-adrenergic
receptors in the heart
Sympathetic stimulation increases the
heart rate

Lesson Two
11
Parasympathetic Control
Parasympathetic innervation of the heart
by vagus nerve
Continuous inhibitory influence on the heart
by decreasing heart rate and contractility

Lesson Two
12
Hormonal Regulation
Sympathetic impulses are transmitted to
adrenal medulla and blood vessels
Adrenal medulla secretes epinephrine and
norepinephrine

Lesson Two
13
Epinephrine
Epinephrine increases rate and force of
contraction
Epinephrine also:
Constricts blood vessels in skin, kidneys, GI
tract, and other organs
Dilates skeletal and coronary vessels

Lesson Two
14
Norepinephrine
Causes constriction of peripheral blood
vessels in most areas of the body
Stimulates cardiac muscle

Lesson Two
15
Electrolytes

Lesson Two
16
Electrolytes
Substances that separate into electrically
charged particles called ions.
Cations have a positive charge.
Anions have a negative charge.

Lesson Two
17
Cations

Lesson Two
18
Sodium (Na+
)
Most prevalent cation in extracellular fluid.
“Water follows sodium.”
Important in transmission of nervous
impulses.
Hypernatremia is an abnormal increase in
sodium.
Hyponatremia is an abnormal decrease in
sodium.

Lesson Two
19
Potassium (K+
)
Most prevalent cation in the intracellular
fluid.
Important in transmission of electrical
impulses.
Hyperkalemia is an abnormally high
potassium level.
Hypokalemia is an abnormally low
potassium level.

Lesson Two
20
Calcium (Ca++
)
Plays a major role in muscle contraction
as well as nervous impulse transmission.
Hypercalcemia is an abnormally increased
calcium level.
Hypocalcemia is an abnormally low
calcium level.

Lesson Two
21
Magnesium (Mg++
)
Necessary for several biochemical
processes.
Closely associated with phosphate.
Hypermagnesemia is an abnormally
increased level of magnesium.
Hypomagnesemia is an abnormally
decreased level of magnesium.

Lesson Two
22
Anions

Lesson Two
23
Chloride (Cl-
)
Negative charge balances the positive
charge of cations.
Major role in fluid balance and renal
function.
Associated with sodium.

Lesson Two
24
Bicarbonate (HCO3
-
)
Principal buffer of the body
Neutralizes the hydrogen ion and other
organic acids

Lesson Two
25
Phosphate (HPO4
-
)
Important in body energy stores
Closely associated with magnesium in
renal function
Acts as a buffer, primarily in the
intracellular space

Lesson Two
26
Role of Electrolytes
Myocardial cells bathed in electrolyte
solution
Electrolytes that influence cardiac
function:
Calcium
Potassium
Sodium26
Magnesium

Lesson Two
27
Conductive System
Cardiac conductive system properties:
Excitability
 Ability of the cells to respond to an electrical stimulus
Conductivity
 Ability of the cells to propagate the electrical impulse from
one cell to another
Automaticity
 Pacemaker cells’ capability of self-depolarization
Contractility
 Ability of muscle cells to contract, or shorten

Lesson Two
28
Conduction System
Sinoatrial Node
Internodal Atrial
Pathways
Atrioventricular Node
Atrioventricular
Junction
Bundle of His
Left and Right Bundle
Branches
Purkinje Fibers

Lesson Two
29
Intrinsic Rates
SA node
60-100/min
AV junctional tissue
40-60/min
Ventricles (bundle
branches and Purkinje
fibers)
10-40/min

Lesson Two
30
Pacemaker Rule
Pacemaker site with the fastest rate will
generally control the heart.

Lesson Two
31
Summary
Nervous Control of the Heart
Hormonal Regulation
Electrolytes
Conductive System

Lesson Two
32

Cardiac physiology

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