Transcript book ppt - Castle High School

38
Circulatory Systems
Chapter 38 Circulatory Systems
Key Concepts
• 38.1 Circulatory Systems Can Be Open or
Closed
• 38.2 Circulatory Systems May Have
Separate Pulmonary and Systemic Circuits
• 38.3 A Beating Heart Propels the Blood
• 38.4 Blood Consists of Cells Suspended in
Plasma
Chapter 38 Circulatory Systems
Key Concepts
• 38.5 Blood Circulates through Arteries,
Capillaries, and Veins
• 38.6 Circulation Is Regulated by
Autoregulation, Nerves, and Hormones
Chapter 38 Opening Question
What are the critical factors that
determine whether a person recovers
from a heart attack?
Concept 38.1 Circulatory Systems Can Be Open or Closed
The function of a circulatory system is to
transport substances around the body.
It consists of:
• Muscular pump—the heart
• Fluid—blood
• Series of conduits—blood vessels
Concept 38.1 Circulatory Systems Can Be Open or Closed
Some animals do not need circulatory
systems:
• Single-celled organisms exchange directly
with the environment
• Structures and body shapes allow
exchange between cells and the
environment
• Gastrovascular systems bring the external
environment inside the animal
Concept 38.1 Circulatory Systems Can Be Open or Closed
Open circulatory system:
• The circulatory fluid—hemolymph—leaves
circulatory system and moves between
cells and tissues
• Flows back into heart or circulatory
vessels
Open circulatory systems are found in
arthropods and mollusks.
Figure 38.1 Circulatory Systems (Part 1)
Concept 38.1 Circulatory Systems Can Be Open or Closed
Closed circulatory system—blood vessels
keep circulatory fluid (blood) separate from
the fluid around cells (interstitial fluid).
Blood consists of liquid blood plasma and
blood cells.
Water and small molecules leak out through
capillaries—blood plasma and interstitial
fluid make up extracellular fluid.
Figure 38.1 Circulatory Systems (Part 2)
Concept 38.1 Circulatory Systems Can Be Open or Closed
The closed vascular system contains:
• Arteries—carry blood away from the heart
and branch into arterioles that feed the
capillary beds
• Capillaries—the site of exchange
between blood and interstitial fluid
• Venules—drain the capillary beds and
form veins, which deliver blood back to
the heart
Concept 38.1 Circulatory Systems Can Be Open or Closed
Advantages of closed circulatory systems:
• Circulatory fluid can flow more rapidly
• Blood flow to specific tissues can be
controlled by varying resistance
• Specialized cells and molecules that
transport oxygen, hormones, and nutrients
can be kept in the vessels
Concept 38.2 Circulatory Systems May Have Separate Pulmonary
and Systemic Circuits
In fish, there is a single circuit; in birds,
crocodiles and mammals, there are
separate circuits:
• Pulmonary circuit—blood is pumped
from the heart to the lungs and back again
• Systemic circuit—blood travels from the
heart to the rest of the body and back to
the heart
Concept 38.2 Circulatory Systems May Have Separate Pulmonary
and Systemic Circuits
Fish hearts have two chambers:
• Atrium—receives blood from the body
• Ventricle—receives pumped blood from
the atrium and sends it to the gills,
arranged on gill arches
Blood flows through afferent arterioles into
the gill arch.
Blood leaves in efferent arterioles, which
join together in the aorta.
In-Text Art, Ch. 38, p. 748
Concept 38.2 Circulatory Systems May Have Separate Pulmonary
and Systemic Circuits
Lungfish have adapted to breathe in air as
well as in water.
A lung formed from the gut functions in air.
A divided atrium separates blood into
pulmonary and systemic circuits—it can
receive blood from either the lung or other
tissues.
In-Text Art, Ch. 38, p. 749 (1)
Concept 38.2 Circulatory Systems May Have Separate Pulmonary
and Systemic Circuits
Amphibians have three-chambered hearts.
A ventricle pumps blood to the lungs and
body.
One atrium receives oxygenated blood from
the lungs, a second atrium receives blood
from the body.
The ventricle directs the flow to the
pulmonary or systemic circuit.
In-Text Art, Ch. 38, p. 749 (2)
Concept 38.2 Circulatory Systems May Have Separate Pulmonary
and Systemic Circuits
Reptiles have three- or four-chambered
hearts and two aortas:
• The left aorta receives oxygenated blood
from the left side of the ventricle and
delivers it to the body
• The right aorta can receive blood from
either side of the ventricle
In-Text Art, Ch. 38, p. 749 (3)
Concept 38.2 Circulatory Systems May Have Separate Pulmonary
and Systemic Circuits
The reptilian ventricle is partly divided by a
septum.
When the animal is breathing, blood flows to
the pulmonary circuit.
When the animal is not breathing, blood
flows to the systemic circuit.
Concept 38.2 Circulatory Systems May Have Separate Pulmonary
and Systemic Circuits
Crocodilians, birds, and mammals have
four-chambered hearts and separate
pulmonary and systemic circuits.
Deoxygenated blood from the body arrives
at the right atrium and flows into the right
ventricle.
Right ventricle pumps blood through
pulmonary arteries to lungs to pick up
oxygen—then back to the left atrium of the
heart through pulmonary arteries.
Concept 38.2 Circulatory Systems May Have Separate Pulmonary
and Systemic Circuits
Oxygenated blood flows from the left atrium
into the left ventricle—it contracts and
sends blood through the aorta to the rest
of the body.
Oxygen-depleted blood returns to the right
atrium through the vena cavae, large
veins.
In-Text Art, Ch. 38, p. 750
Concept 38.2 Circulatory Systems May Have Separate Pulmonary
and Systemic Circuits
Separate circuits have advantages:
• Oxygenated blood can be distributed at
higher pressure and flow than is possible
in fishes.
• Blood in each system cannot mix—
systemic circuit always receives blood with
higher O2 content.
• Circuits can operate at different pressures.
Concept 38.3 A Beating Heart Propels the Blood
The human heart has four chambers—two
atria and two ventricles.
The right atrium receives oxygen-depleted
blood—it then flows through an
atrioventricular (AV) valve into the right
ventricle.
When the right ventricle contracts, the flaps
of the AV valve close, to prevent backflow.
Blood is pumped through pulmonary artery
to the lungs and pulmonary valve closes.
Figure 38.2 The Human Heart and Circulation (Part 1)
Figure 38.2 The Human Heart and Circulation (Part 2)
Figure 38.2 The Human Heart and Circulation (Part 3)
Concept 38.3 A Beating Heart Propels the Blood
Oxygenated blood returns via pulmonary
veins to the left atrium.
Blood flows into left ventricle through
another AV valve.
Left ventricle contracts forcefully to send
blood through the aorta—then relaxes.
The aortic valve at base of aorta then
closes, to prevent backflow.
Concept 38.3 A Beating Heart Propels the Blood
The ventricles can adjust the force of their
contractions to meet demands of exercise.
The Frank-Starling law is a property of
cardiac muscle cells:
• When they are stretched, as occurs when
returning blood volume increases, they
contract more forcefully.
Concept 38.3 A Beating Heart Propels the Blood
The cycle of cardiac contraction and
relaxation is the cardiac cycle.
Two phases:
Systole—when ventricles contract
Diastole—when ventricles relax
The atria contract just before the ventricles,
to add blood volume to the ventricles.
Heart murmurs are sounds made by valves
that do not close completely.
Figure 38.3 The Cardiac Cycle
Concept 38.3 A Beating Heart Propels the Blood
Cardiac muscle functions as a pump:
Cells are in electrical contact with each
other through gap junctions—spread of
action potentials stimulates contraction in
unison.
Some cells are pacemaker cells and can
initiate action potentials without input from
the nervous system.
The primary pacemaker cells are in the
sinoatrial node.
Concept 38.3 A Beating Heart Propels the Blood
Action potentials in pacemaker cells are
generated by voltage-gated Ca2+
channels.
The resting membrane potential of these
cells is not stable and gradually drifts
upward.
Concept 38.3 A Beating Heart Propels the Blood
Ion channels in pacemaker cells are
different from other cardiac cells:
• Na+ channels are more permeable to
sodium influx, so resting potential is
higher.
• K+ channels that open after action
potential to repolarize cell eventually
close—K+ inside cell causes membrane
potential to drift upwards toward threshold
Concept 38.3 A Beating Heart Propels the Blood
Pacemaker cells initiate contractions—the
heart does not need nerve signals to beat.
The nervous system controls heart rate by
influencing resting potential:
• Norepinephrine from sympathetic nerves
increases permeability of Na+/K+ and Ca2+
channels.
The resting potential rises more quickly and
action potentials are closer together.
Concept 38.3 A Beating Heart Propels the Blood
Opposite effect from parasympathetic
nerves:
• Acetylcholine increases permeability of K+
and decreases that of Ca2+ channels.
The resting potential rises more slowly and
action potentials are farther apart.
Figure 38.4 The Autonomic Nervous System Controls Heart Rate (Part 1)
Figure 38.4 The Autonomic Nervous System Controls Heart Rate (Part 2)
Concept 38.3 A Beating Heart Propels the Blood
Heart muscle contraction is coordinated.
An action potential is generated in the
sinoatrial node.
The action potential spreads through gap
junctions in the atria and they contract
together, but it does not spread to the
ventricles.
Concept 38.3 A Beating Heart Propels the Blood
The action potential in the atria stimulates
the atrioventricular node.
The node consists of non-contracting cells
that send action potentials to the ventricles
via the bundle of His.
The bundle divides into right and left bundle
branches that run to the tips of the
ventricles and then spread throughout—
called Purkinje fibers.
A contraction spreads rapidly and evenly
throughout the ventricles.
Figure 38.5 The Heartbeat (Part 1)
Figure 38.5 The Heartbeat (Part 2)
Figure 38.5 The Heartbeat (Part 3)
Concept 38.3 A Beating Heart Propels the Blood
Ventricular muscle fibers contract for much
longer than skeletal muscle fibers.
Their extended action potential is due to a
longer opening of voltage-gated Ca2+
channels and increased availability of Ca2+
to stimulate contraction.
Concept 38.3 A Beating Heart Propels the Blood
An electrocardiogram (ECG or EKG) uses
electrodes to record events in the cardiac
cycle.
Large action potentials in the heart cause
electrical current to flow outward to all
parts of the body.
Electrodes register the voltage difference at
different times.
Wave patterns of an ECG are labeled by
letters P, Q, R, S, and T—each
representing an event
Figure 38.6 The Electrocardiogram (Part 1)
Figure 38.6 The Electrocardiogram (Part 2)
Concept 38.4 Blood Consists of Cells Suspended in Plasma
Blood is a connective tissue made of cells in
a liquid extracellular matrix, called plasma.
Most of the cells are erythrocytes, or red
blood cells, that transport gases.
Blood also contains leukocytes (white
blood cells) as well as platelets (pinchedoff fragments of cells).
Figure 38.7 The Composition of Blood
Concept 38.4 Blood Consists of Cells Suspended in Plasma
Red blood cells are generated by stem cells
in the bone marrow—their function is to
transport respiratory gases.
Erythropoietin, a hormone released in the
kidney in response to insufficient oxygen,
or hypoxia, controls red blood cell
production.
New blood cells contain mostly hemoglobin
and circulate for about 120 days in
humans.
Concept 38.4 Blood Consists of Cells Suspended in Plasma
Blood cells are broken down in the spleen,
and the iron is recycled to make more
hemoglobin.
A blood sample can be spun down to
assess content—plasma will remain on
top.
Hematocrit is the percentage of the blood
made up by cells.
A low number may indicate anemia.
Concept 38.4 Blood Consists of Cells Suspended in Plasma
Bone marrow also produces
megakaryocytes that release platelets.
Platelets initiate blood clotting when
activated by collagen exposed in damaged
blood vessels.
They release chemical clotting factors,
which activate other platelets.
Concept 38.4 Blood Consists of Cells Suspended in Plasma
Steps in blood clotting:
• Cell damage and platelet activation
• Inactive enzyme prothrombin converts to
active form, thrombin
• Thrombin cleaves fibrinogen and forms
fibrin
• Fibrin threads form mesh that clots blood
and seals vessel
Hemophilia is a genetic inability to form one
clotting factor.
Figure 38.8 Blood Clotting (Part 1)
Figure 38.8 Blood Clotting (Part 2)
Figure 38.8 Blood Clotting (Part 3)
Concept 38.5 Blood Circulates through Arteries, Capillaries,
and Veins
Different types of blood vessels help control
blood flow.
Arteries must withstand greater pressure
than veins—walls have elastin and
collagen that allow them to stretch and
recoil and move blood forward.
Smooth muscle cells in the walls allow them
to dilate or constrict, which changes
volume of blood flow.
Figure 38.9 Anatomy of Blood Vessels (Part 1)
Concept 38.5 Blood Circulates through Arteries, Capillaries,
and Veins
Blood pressure and flow is lower through
the capillaries—each artery supplies many
capillaries, which have an enormous
surface area.
Capillary walls are a single layer of
endothelial cells and have tiny holes called
fenestrations.
Capillary beds are permeable to water, ions,
and small molecules, but not to large
proteins.
Figure 38.9 Anatomy of Blood Vessels (Part 2)
Concept 38.5 Blood Circulates through Arteries, Capillaries,
and Veins
Capillary beds are variable in their
permeability to large ions.
In tissues other than brain, most molecules
can pass through—brain capillaries have
no fenestrations.
The blood-brain barrier is due to this low
permeability of brain capillaries, which
helps protect the brain from toxins.
Figure 38.10 A Narrow Lane
Concept 38.5 Blood Circulates through Arteries, Capillaries,
and Veins
Starling’s forces are two opposing forces
that maintain water balance in the
capillaries:
• Blood pressure—forces water and small
solutes out
• Osmotic pressure—pulls water back into
the capillaries
Concept 38.5 Blood Circulates through Arteries, Capillaries,
and Veins
Blood pressure is higher at the arterial end
of the capillary bed and drops at the
venous end.
Osmotic pressure is constant along the
capillary.
If blood pressure is higher than the osmotic
pressure, fluid leaves the capillary—if
blood pressure is lower, fluid returns to the
capillary.
Figure 38.11 Starling’s Forces (Part 1)
Figure 38.11 Starling’s Forces (Part 2)
Concept 38.5 Blood Circulates through Arteries, Capillaries,
and Veins
Edema is accumulation of fluid in
extracellular space due to:
• Fall in blood protein levels from disease
• Histamine release—increases capillary
permeability, relaxes smooth muscle in
arterioles and raises blood pressure in the
capillaries
Concept 38.5 Blood Circulates through Arteries, Capillaries,
and Veins
Veins have a high capacity to stretch and
store blood.
Blood returning from below the heart is
assisted by skeletal muscle contractions
that squeeze the veins.
One-way valves in the veins prevent
backflow.
Both leg muscle contractions and breathing
actions help return venous blood to the
heart.
Figure 38.12 One-Way Flow
Concept 38.5 Blood Circulates through Arteries, Capillaries,
and Veins
The lymphatic system returns interstitial
fluid to the blood.
When the fluid enters the vessels it is called
lymph.
Lymph capillaries are blind-ended and
continually take up excess fluid.
They ultimately merge into two thoracic
ducts—these empty into veins in the neck.
Lymph nodes produce lymphocytes that
screen lymph fluid for pathogens.
Figure 38.13 The Human Lymphatic System
Concept 38.6 Circulation Is Regulated by Autoregulation, Nerves,
and Hormones
Blood flow depends on pressure.
Mean arterial pressure (MAP) is determined
by cardiac output (CO) and total peripheral
resistance (TPR).
MAP = CO x TPR
Heart rate (HR) and stroke volume (SV) are
also important.
MAP = HR x SV x TPR
Concept 38.6 Circulation Is Regulated by Autoregulation, Nerves,
and Hormones
Autoregulatory mechanisms are local
actions in the capillary bed that cause the
arterioles to constrict or dilate.
Smooth muscle “cuffs” or precapillary
sphincters can shut off blood flow from an
arteriole to a capillary bed.
Relaxation of the smooth muscle causes
increased blood flow.
Figure 38.14 Local Control of Blood Flow
Concept 38.6 Circulation Is Regulated by Autoregulation, Nerves,
and Hormones
Autoregulation depends on smooth muscle
being sensitive to its chemical
environment.
Low O2 and high CO2 levels cause smooth
muscle to relax, increasing blood supply
and bringing in O2 and decreasing CO2.
Other by-products of metabolism also cause
arterioles to dilate.
Concept 38.6 Circulation Is Regulated by Autoregulation, Nerves,
and Hormones
Arteries and arterioles are innervated by the
sympathetic division of the autonomic
nervous system.
The neurotransmitter norepinephrine causes
arterioles to constrict and elevates TPR.
Heart rate and stroke volume are also
raised by sympathetic activation, resulting
in elevated MAP.
This enables rapid delivery of oxygen and
fuel where needed.
Concept 38.6 Circulation Is Regulated by Autoregulation, Nerves,
and Hormones
Sympathetic activation is coordinated by the
medulla—receives information from
baroreceptors (stretch receptors) that
monitor blood pressure changes.
Chemoreceptors send information about
blood composition.
Figure 38.15 Regulating Cardiac Output
Concept 38.6 Circulation Is Regulated by Autoregulation, Nerves,
and Hormones
Increased activity of the stretch receptors
signals rising blood pressure.
Medulla issues two sets of commands:
• Inhibition of sympathetic nervous system,
causing arterioles to dilate
• Parasympathetic nerves slow pacemaker
cells
The result is lowered blood pressure.
Concept 38.6 Circulation Is Regulated by Autoregulation, Nerves,
and Hormones
Hormones regulate arterial pressure:
• Epinephrine—released from adrenal
medulla in response to a fall in arterial
pressure or the “fight-or-flight” response;
arterioles contract
• Angiotensin—produced when blood supply
to the kidneys falls; reduces flow to
peripheral tissues and directs it to
essential organs
Concept 38.6 Circulation Is Regulated by Autoregulation, Nerves,
and Hormones
Antidiuretic hormone (ADH), or vasopressin,
is released in response to low
baroreceptor activity:
• Causes the kidneys to absorb more water
and increases blood pressure
Figure 38.16 Influences of Local and Systemic Mechanisms on Blood Pressure
Answer to Opening Question
To survive a heart attack the brain must
have blood supply restored.
To recover from a heart attack, high cardiac
output must be sustained to the organs.
After a heart attack, sympathetic activity will
increase the rate and strength of
contractions—if the heart cannot pump the
returning blood, blood and fluids will
accumulate in the body, and oxygen levels
will be low.
It is essential that the kidneys function to
remove the excess fluid.