final Flashcards
primary reproductive organs
ovaries
accessory reproductive organs
uterine tubes, uterus, vagina, external genitalia, mammary glands
gametes are made using
mitotic division
what is the site of oocyte production
ovarian follicles
what is the site of sex hormone release
ovarian follicles (estrogen and progesterone)
mature follicle forms from
secondary follicle
mature follicle components
- secondary oocyte surrounded by zona pellucida
- then corona radiata
- antrum
when ovulation occurs corona radiata goes
with the egg as it goes into uterine tube so in order to fertilize the egg it has to make it through both of these layers (corona radiata, zona pellucida) to reach the egg
what cells are sources of estrogen?
granulosa cells
what part of the mature follicle gets bigger during follicular development
fluid-filled antrum
how often is a mature follicle formed
one per month
division of mature follicle
divides mitoticly and divides into secondary oocyte with 23 chromosomes, it begins but stops in metaphase
doesn’t occur unless oocyte is fertilized
corpus luteum formation
remanants of follicle
after mature follicle ruptures and oocyte expelled
corpus luteum secretes
sex hormones progesterone and estrogen to stimulate buildup of uterine lining (endometrium) and prepare uterus for possible implantation of fertilized oocyte
what structure releases GnRH
hypothalamus
GnRH release stimulates release of
FSH and LH
FSH and LH play a major role in
events in ovarian cycle
phases of ovarian cycle
- follicular phase (days 1-13)
- ovulation (day 14)
- luteal phase (days 15-38)
ovulation
- release of secondary oocyte from mature follicle
- occurs on day 14 of 28 day cycle
- antrum increases in size and swells with increased fluid
- expands until ovarian surface thins, eventually rupturing and expelling secondary oocyte
ovulation is induced with increased
LH secretion
order of oocyte release on ovaries
- infundibulum (has to catch oocyte, contains fimbriae)
- ampulla (where fertilization occurs)
- isthmus
- uterine part
uterine wall is mostly
smooth muscle
contains
- endometrium
- myometrium
- perimetrium (thin connective tissue covering on outside)
from deep to superficial
uterine cycle
changes in endometrial lining
uterine cycle is influenced by
estrogen and progesterone - secreted by follicle and then corpus luteum
uterine cycle phases
menstrual phase (1-5)
proliferative phase (6-14)
secretory phase (15-28)
menstrual phase
1-5
sloughing off of functional layer
lasts through period of menstrual bleeding
proliferative phase
days 6-14
development of new functional layer of endometrium
overlaps time of follicle growth and ovarian estrogen secretion
secretory phase
days 15-28
increased progesterone secretion from corpus luteum
results in increased vascularization and uterine gland development
estrogen secretion happens in
proliferative phase of uterine cycle
progesterone secretion happens in
secretory phase of uterine cycle
if fertilization doesn’t occur in secretory phase
- corpus luteum degenerates
- drop in levels of progesterone (causing functional layer to slough off)
levels of hormones during follicular phase of ovarian cycle
high FSH and estrogen levels
low LH and progesterone
mammary glands
exocrine glands
divided into lobes and then into lobules composed of alveoli
lactiferous ducts
bring materials to the nipple
breast milk release
- occurs in response to internal and external stimuli
- starts to produce after giving birth
prolactin
produced in anterior pituitary gland
stimulates milk production, with increase mammary gland forms more and larger alveoli
oxytocin
produced by hypothalamus and released from posterior pituitary gland
responsible for milk ejection
primary male reproductive organs
testes
accessory reproductive organs of male reproductive system
ducts and tubules lead from testes to penis
male accessory glands
penis
epididymis
responsible for storage of sperm
where are gametes produced in MRS
inside seminiferous tubules
internal components of testes are organized into
lobules divided by septum
components of seminiferous tubules
within tubule lumen of seminiferous tubules sperm or germ cells are found
seminiferous tubules are making haploid gametes so meiosis is going to start dividing toward lumen
sperm within lumen
spermatids line the lumen
spermatagonia on outside border of seminiferous tubule
sustentacular cells
provide strength to germ cells, support them, provide nutritional support, and influence rate of sperm cell production
maturation of sperm cells
spermatogonia (2n) - primary spermatocyte - secondary spermatocyte - spermatids - spermatogonia (sperm) (n)
hormone regulation on spermatogenesis and androgen production
- GnRH stimulates anterior pituitary gland to secrete FSH and LH
- LH stimulates interstitial cells to secrete testosterone, FSH stimulates sustentacular cells to secrete androgen-binding protein (ABP)
- Testosterone stimulates spermatogenesis but inhibits GnRH secretion and reduces the anterior pituitary glands sensitivity to GnRH
- Rising sperm count levels causes sustentacular cells to secrete inhibin, further inhibiting FSH secretion
- testosterone stimulates libido and development of secondary sex characteristics
androgen binding protein keeps
testosterone levels high in testes
seminal fluid
- alkaline secretion need to neutralize vaginal acidity
- gives nutrients to sperm traveling in female reproductive tract
- produced by accessory glands
a) seminal vesicles
b) prostate gland
c) bulbourethral glands
semen
- formed from seminal fluid and sperm
- called ejaculate when released during intercourse
- contain 200-500 million spermatozoa
- transit time from seminiferous tubules to ejaculate is about 2 weeks
puberty
- period in adolescence where reproductive organs become fully functional
- external sex characteristics become more prominent
timing of puberty affected by
genetics, health, environmental factors
puberty initiation
- hypothalamus secretes GnRH
- stimulates anterior pituitary gland to secrete FSH and LH
- sex hormone levels increase starting the process of gamete and sexual maturation
menarche
about 2 years after first signs of puberty
first period
gender differences of puberty
girls 2 years prior to boys
8-12 for girls
9-14 for boys
racial differences of puberty
african american girls about 1 year earlier than caucasions
onset of puberty has decreased with better nutrition and health care
precocious puberty
- signs of puberty developing much earlier than normal
- may be without known cause
- may be due to pituitary or gonad tumor
perimenopause
time near menopause
irregular or skipped periods
menopause
women stop monthly menstrual cycles for a year
45-55
- atrophy of reproductive organs and breasts with reduced hormones
- decrease vaginal wall thickness
- hot flashes
- thinning hair
- increased risk of osteoporosis and heart disease
- sometimes treated with hormone replacement therapy
fertilization
- 2 gametes fuse to form diploid cell (containing genetic material from both parents)
- restores diploid number of chromosomes
- determines sex of organism
- initiates cleavage
oocyte viable for how long after ovulation
24 hrs
sperm remains viable for
3-4 days
corona radiata penetration
1st phase of fertilization of mature oocyte
when sperm reaches secondary oocyte, it is initially prevented by corona radiata and zona pellucida
sperm can push through these layers
zona pellucide penetration
Acrosome reaction:
- release of digestive enzymes from acrosomes
- allows sperm to penetrate zona pellucida
After penetration of secondary oocyte:
- immediate hardening of zona pellucida
- prevents other sperm from entering this layer
- ensures only one sperm fertilizes the oocyte
labor
physical expulsion of fetus and placenta from uterus
usually 38 weeks
increased levels of estrogen during labor
- increases myometrium sensitivity
- stimulate production of oxytocin receptors on uterine myometrium
contractions become more intense and more frequent with increasing
estrogen and oxytocin
premature labor
prior to 38 wks
undesirable because infant body systems are not fully develop (especially lungs, insufficient surfactant)
initiation of true labor (uterine contractions)
- mothers hypothalamus secretes increasing levels of oxytocin
- fetus’s hypothalamus also secreting oxytocin
- combined maternal and fetal oxytocin initiates true labor
both fetal and maternal release of oxytocin stimulate placenta to secrete
prostaglandins
- help stimulate uterine muscle contraction and soften and dilate the cervix
true labor is a
positive feedback mechanism
positive feedback mechanism of true labor
- oxytocin is released from mother and fetus hypothalamus
- stimulates uterus to contract and placenta to make prostaglandins
- prostaglandings stimulate more frequent and intense contractions of uterus
- uterine contractions cause fetal head to push against cervix, causing it to stretch and dilate
- dilating cervix initiates nerve signals to hypothalamus which causes more oxytocin release from mother and fetus
blood
- regenerated CT
- moves gases nutrients, wastes, and hormones
- transported through CV system
arteries
transport blood away from heart
veins
transport blood toward heart
capillaries
allow exchange between blood and body tissues
components of blood
formed elements and plasma
formed elements of blood
erythrocytes (RBCs)
leuokocytes (white blood cells)
platelets (thrombocytes)
erythrocytes function in blood
transports respiratory gases in the blood
leukocytes function in the blood
defend against pathogens
platelets function in the blood
form clots to prevent blood loss
plasma of blood
fluid portion of blood
contains plasma proteins and dissolved solutes
functions of blood
- transportation
- protection
- regulation of body conditions (maintaining homeostasis)
blood helps transport…
formed elements, dissolved molecules, and ions
- carries oxygen to and from carbon dioxide to the lungs
- transports nutrients, hormones, heat, and waste products
leukocytes, plasma proteins, and other molecules (of immune system) protect against
pathogens
platelets and plasma proteins within blood protect against
blood loss
blood and body temperature
blood absorbs heat from body cells (especially muscle)
heat is released at skin blood vessels
blood and pH
blood absorbs acid and base from body cells
blood contains chemical buffers (e.g., bicarbonate, proteins)
blood and fluid balance
water is added to blood from GI tract
water is lost through urine, skin, and respiration
fluid is constantly being exchanged between blood and interstitial fluid
- blood contains proteins and ions helping maintain osmotic balance
oxygen-rich blood is
bright red
oxygen poor blood is
dark red
volume of blood in body
about 5 L
males have slightly more than females
viscosity of blood
blood is thicker than water (4-5x)
depends on amount of dissolved and suspended substances
viscosity increases if
erythrocyte number increases
amount of fluid decreases
plasma concentration of solutes (e.g., proteins, ions) within blood
typically .09%
determines direction of osmosis across capillary walls
temperature of blood
1 degree high than measured body temperature
pH of blood
between 7.35 and 7.45
crucial for normal plasma protein shape
percentages of blood
Plasma:
- 55% of whole blood
- contains water, proteins, and other solutes
Buffy Coat:
- <1% of whole blood
- contains platelets and leukocytes
Erythrocytes:
- 44% of whole blood
- contains erythrocytes
what type of fluid is plasma
extracellular fluid
has higher protein concentration to interstitial fluid
blood is a
colloid mixture
contains dispersed proteins
plasma proteins examples
albumin
globulins
fibrinogen
other clotting proteins, enzymes, and some hormones
most plasma proteins are produced in
the liver
some may be produced by leukocytes or other organs
colloid osmotic pressure
prevents loss of fluid from blood as it moves through capillaries
- helps maintain blood volume and blood pressure
colloid osmotic pressure can be
decreased with certain diseases resulting in fluid loss from blood and tissue swelling
- liver disease
- kidney diseases
albumins
most abundant
exert greatest colloid osmotic pressure
act as transport proteins for some lipids, hormones, and ions
globulins
- second largest group
- smaller alpha-globulins and larger beta-globulins that transport water insoluble molecules, hormones, metals, ions
- gamma-globulins (immunoglobulins or antibodies) - body defense
fibrinogen
- 4% of plasma proteins
- blood clot formation
serum
plasma with clotting proteins removed
hemopoiesis
production of formed elements
where does hemopoiesis occur
red bone marrow of certain bones
hemocytoblasts
stem cells/pluriopotent - can differentiate into many types of cells
produces myeloid and lymphoid line
myeloid line
forms erythrocytes, all leukocytes except lymphocytes, and megakaryocytes (platelet producing cells)
lymphoid line
only produce lymphocytes
erythrocytes are formed by
erythropoiesis
platelets are formed by
thrombopoiesis
leukocytes are formed by
leukopoesis
platelet formation
megakaryocytes line blood vessels where appendages on megakaryocytes fall into called proplatelets
as blood pushes through proplaets break off forming platelets within blood
erythrocytes
- contain hemoglobin
- biconcave disc structure
- contain spectrin for support and flexibility
- can stack and line up in single file (roleau)
- transport oxygen and CO2 between tissues and lungs
hemoglobin
red pigmented protein
- oxygenated when maximally loaded with oxygen
- termed deoxygenated when some oxygen is lost
- composed of 4 globin proteins with 2 alpha chains and 2 beta chains each containing a heme group with iron in its center
makeup of hemoglobin
oxygen binds to iron in center of hemoglobin, so each hemoglobin can bind to 4 oxygen molecule
oxygen binds to iron
binding is weak
rapid attachment in lungs and rapid detachment in body tissues
carbon dioxide binds to globin protein
binding is weak
attachment in body tissue and detachment in lungs
EPO regulation of erythrocyte production
- decreased blood oxygen levels
- kidney detects decreased blood O2
- kidney cells release EPO into blood
- EPO stimulates red bone marrow to increase the rate of production of erythrocytes
- increased numbers of erythrocytes enter the circulation, during which time the lungs oxygenate erythrocytes and blood O2 levels increase
- increased O2 levels are detected by kidney, stopping EPO release (negative feedback)
erythrocyte recycling
- eryhtrocytes form in red bone marrow
- they circulate in blood for about 120 days
- aged erythrocytes are phagocytized by macrophages in the liver and spleen. the three components of hemoglobin are separated (globin, heme, iron)
- each of separated coponents of hemoglobin have different fate
- globin proteins: broken down into amino acids and enter the blood (potential use to make new erythrocytes)
- iron: small amounts of iron are lost in sweat, urine, and feces daily; also lost during injury or mestruation
- heme: converted to biliverdin then bilirubin which is transported to liver by albumin and released as bile into small intestine. then bilirubin is converted to urobilinogen in small intestine (some urobilinogen absorbed back into blood and converted into urobilin and excreted in urine, most continues in large intense and is converted into stercobilin and expelled in feces)
type A
surface antigen A
anti B antibodies
type B
surface antigen B
anti A antibodies
type AB
surface antigens A and B
no anti A or anti B
type O
no surface antigens
anti A and anti B
Rh blood type
presence or absence of Rh factor (antigen D) deterines if blood is + or -
antibodies to Rh are not usually there (only appear after Rh exposure to Rh+ blood)
agglutination in transfusion reaction
if patient is type B and is given type A blood…
- anti A antibodies in plasma will attach to type A erythrocytes and cause a clumping of erythrocytes creating a blockage in small vessels
leukocytes
defend against pathogen
motile and flexible - most not in blood but in tissues
leukocytes have ability to perform
diapedesis and chemotaxis
diapedesis
process of squeezing through blood vessel wall
chemotaxis
attraction of leukocytes to chemical at an infection site
neutrophils
phagocytize pathogens
most abundant leukocyte
eospinophils
phagocytize antigen-antibody complexes and allergens
present in cases of parasitic infection
basophils
release histamines (vasodilator increasing capillary permeability) and heparin (anticoagulant)
granulocytes
neutrophils
basophils
eosinophils
agranulocytes
lymphocytes
monocytes
lymphocytes
coordinate immune cell acitivty
attack pathogens and abnormal infected cells
produce antibodies
monocytes
exit blood vessels and become macrophages
phagocytize pathogens
Most abundant to least abundant leukocytes
neutrophils
lymphocytes
monocytes
eosinophils
basophils
platelets are stored in
spleen
circulation of platelets
circulate for 8-10 days and then broken down and recycled
platelets play a major role in
blood clotting
hemostasis
stoppage of bleeding
phases of hemostasis
vascular spasm
platelet plug formation
coagulation phase
hemostasis steps
- Vascular spasm
- blood vessel constricts to limit blood escaping - Platelet plug formation
- platelets arrive at site of injury and stick to exposed collagen fibers - Coagulation
- coagulation cascade converts inactive proteins to active forms, leading to production of fibrin strands of a blood clot
vascular spasm
- 1st phase
- lasts from few to many minutes
- greater vasoconstriction with greater vessel damage
platelet plug formation
when blood vessel is damaged collagen fibers are exposed causing platelets to stick to collagen with help of von Willebrand factor where they develop long processes allowing for better adhesion where platelets continue to aggregate there
when blood vessel is uninjured platelet activation is
inhibited as a result of prostacyclin which repels platelets and causes endothelial cells and platelets to make cAMP which inhibits platelet activation
platelet activation
platelets cytosol degranulates and releases chemicals causing
- prolonged vascular spasms
- attraction of other platelets
- coagulation stimulation
- reparation of blood vessels
platelet plug is formed typically within
1 minute
prevented from getting to large by prostacyclin
serotonin and thromboxane A2 causes
prolonged vascular spasms in platelet activation
adenosine triphosphate (ADP) and thromboxane causes
attraction of other platelets and facilitate their degranulation (positive feedback)
procoagulants stimulate
coagulation
mitosis stimulating substances trigger
repair of blood vessel
coagulation
blood clotting
network of fibrin (insoluble protein that comes from fibrinogen) forms a mesh that traps erythrocytes, leukocytes, platelets, and plasma proteins to form a clot
subsances involved in coagulation
- calcium, clotting factors, vitamin K
clotting factors
most inactive enzymes
most produced in liver within hepatocytes
vitamin K
fat soluble coenzyme required for synthesiss of clotting factors II, VII, IX, X
intrinsic coagulation pathway
initiated by damage to inside of blood vessel
extrinsic coagulation pathway
initiated by damage to tissue outside of vessel
clot elimination includes
clot retraction and fibrinolysis
clot retraction
actinomyosin (protein with platelets) contracts and squeezes serum out of developing clot making it smaller
fibrinolysis
degradation of fibrin strands by plasmin
begins within 2 days after clot formation
occurs slowly over a number of days
four chambers of the heart
left atrium and right atrium
left ventricles and right ventricles
left atrium and right atrium are superior chambers that
receive blood and send it to ventricles
left ventricle and right ventricles are inferior chambers that pump blood
away
left side of the heart has
oxygenated blood
right side of the heart has
deoxygenated blood
right side
receives deoxygenated blood from body and pumps it to the lungs
left side
receives oxygenated blood from the lungs and pumps it into the body
atrioventricular valves are between
atria and ventricles
semilunar valves are between
ventricle and an arteriole trunk
pulmonary semilunar valve and aortic semilunar valve
right AV is sometimes called
tricuspid
left AV valve sometimes called
bicuspid
mitral
flow of blood through heart and lungs
- deoxygenated blood enters the atrium through IVC and SVC
- blood within right atrium enters right ventricle through right atrioventricular valve (tricuspid)
- blood enters ventricle is pumped through pulmonary semilunar valve into the lungs
- deoxygenated blood enters lungs where it flows through capillaries and becomes oxygenated and enters back into the heart in the left atrium
- blood within left atrium is pumped into ventricles via left atrioventricular valve (mitral, bicuspid)
- blood within ventricles is then pumped out via the aortic semilunar valve throughout the body where further gas exchange occurs as blood is delievered to body systems and deoxygenated blood is then brought back to the heart
pericardium
refers to 3 layers of the heart
outer layer of heart
fibrous periardium
serous pericardium
contains visceral and parietal layer containing with pericardial cavity with serous fluid
layers of the heart wall (from deep to superficial
epicardium
myocardium
endocardium
ventricles have thicker walls than
atria
left ventricle has thicker wall than
right ventricle
left ventricle must generate higher pressure to force blood through systemic circulation; right just pumps to nearby lungs
cardiac muscle contains
striated muscle due to arrangement of contractile proteins and overlapping nature of thin and thick filaments
sarcolemma
plasma membrane containing openings called T-tubules which are infolds of plasma membrane
cardiac muscle contains intercellular junctions that include
desmosomes
gap junctions
desmosomes
proteins that serve to connect two adjacent cells
become embedded in cell membrane
gap junctions
proteins with opening in center that functionally pass ions through
gap junctions are important in
contraction and activation of muscle
stimulate electrical current needed for contraction
storage site for Ca2+
sarcoplasmic T tubules
cardiac muscle contains
intercalated discs
metabolism of cardiac muscle
high demand for energy
- extensive blood supply
- numerous mitochondria
- myoglobin and creatine kinase
creatine + ATP —->
CK – creatine phosphate + ADP
cardiac muscle is able to use
different kinds of fuel molecules like:
fatty acids, glucose, lactic acid, amino acids, and ketone bodies
cardiac muscle metabolism relies mostly on
aerobic metabolism which makes it susceptible to failure when oxygen is low
fibrous skeleton is made up of
dense irregular connective tissue
fibrous skeleton provides
structural support at boundary of atria and ventricles that froms fibrous rings to anchor valves
the fibrous skeleton acts as an
electrical insulator preventing ventricles from contracting at same time as atria
coronary circulation delivers blood to
heart wall
- coronary arteries transport oxygenated blood to heart wall
- coronary veins transport deoxygenated blood away from heart wall toward right atrium
conduction system
initiations and conducts electrical events to ensure proper timing of contractions
conduction system contains specialized cardiac
muscle cells that have action potentials but do not contract
conduction system activity is influenced by
autonomic nervous system
components of conduction system
SA node
AV node
AV bundle (bundle of His)
R and L bundle branches
Purkinje fibers
SA node
pacemaker
tissue in posterior wall of atrium that starts generating action potential
what part of the brain contains the cardiac center
medulla oblongata
the cardiac center of the medulla contains
- cardioacceleratory
- cardioinhibitory centers
the cardiac center of medulla receives signals from
baroreceptors and chemoreceptors in CV system
the cardiac center sends signals via
sympathetic and parasympathetic pathways
the cardiac center ______ cardiac activity
modifies
- influences rate and force of hearts contractions
what influences the rate and force of heart contractions
cardiac center
what kind of nerve innervation decreases heart rate
parasympathetic
what kind of nerve innervation increases heart rate and force of contraction
sympathetic
steps of heart contraction
Conduction system
1. initiation - SA node generates action potential
2. spread of action potential - action potential is propagated throughout the atria and the conduction system
Cardiac Muscle Cell
1. action potential - action potential is propagated across the sarcolemma of cardiac muscle cells
2. thin filaments slide past thick filaments and sarcomeres shorten within cardiac muscle cells
RMP of nodal cells
-60mV
the sodium concentration is great inside or outside of a nodal cell
greater concentration of Na+ outside of cell
SA Node Cellular Activity
- RMP @ -60mV
- increase (depolarization)
- MP reaches threshold (-40mV) - repolarization
- when cell becomes negative enough ation potential is generated
pacemaker potential
time it takes for SA node to go from -40mV to threshold voltage
steps of SA node generating action potential
- Reaching threshold
- slow voltage gated Na+ channels open
- inflow of Na+ changes membrane potential from -60mV to -40mV - Depolarization
- fast voltage gated Ca2+ channels open. inflow of Ca2+ changes membrane potential from -40mV to just above 0mV - Repolarization
- fast voltage gated Ca2+ close. voltage gated K+ channels open allowing K+ outflow. MP returns to -60mV and K+ channels close
RMP of cardiac muscle cell
-90mV
at RMP of cardiac muscle cell, all Na+ is
closed so concentration gradient for ions remains table so ions aren’t moving through creating action potential
electrical events of cardiac muscle cell
- Depolarization
- starts @ - 90mV and rapidly reaches +30mV - Plateau
- almost no change during period of time - Repolarization
why do cardiac muscle cells have a plateau
helps ensure heart is beating synchronously with all of its components so if stimulated, nothing will happen
steps of cardiac muscle cells
- Depolarization
- fast voltage gated Na+ channels open and Na+ flows into cell reversing polarity from -90mV to +30mV. Channels then close - Plateau
- voltage gated K+ channels open and K+ flow out of cardiac muscle cells. slow voltage gated Ca2+ channels open and Ca2+ moves into the cell with no electrical change and depolarized state is maintained - Repolarization
- voltage gated Ca2+ channels close, voltage gated K+ channels remain open and K+ moves out of cardiac muscle cell, and polarity is reversed from +30mV to -90mV
electrocardiogram (ECG/EKG)
- skin electrodes detect electrical signals of cardiac muscle cells
- common diagnostic tools
P wave
atrial depolarization
QRS complex
ventricular depolarization
during QRS complex the atria are
repolarizing
T wave
ventricular repolarization
P-Q segment
atrial cells’ plateau (atria are contracting)
S-T segment
ventricular plateau (ventricles contracting
P-R interval
time from beginning of P wave to beginning of QRS
from atrial depolarization to beginning of ventricular depolarization
P-R interval represents the time to transmit
action potential through entire conduction system
Q-T interval
time from beginning of QRS to end of T wave
reflects time of ventricular depolarization and repolarization
the length of Q-T interval depends upon
heart rate
cardiac cycle
all events in heart from the start of one beat to the start of the next
the cardiac cycle includes both
systole (contraction) and diastole (relaxation)
relationship of contraction and pressure
contraction increases pressure
relaxation decreases it
blood moves ____ its pressure gradient
down (high to low)
valves ensure that
flow of blood is forward (closure of valves prevents backflow)
what is the most important driving force of cardiac cycle
ventricular activity
ventricular contraction raises
ventricular pressure
AV valves pushed closed, semilunar valves pushed open and blood pushed out
ventricular relaxation lowers
ventricular pressure
semilunar valves closed
AV valves open (no pressure pushing them closed)
phases of cardiac cycle
- atrial contraction and ventricular filling
- isovolumetric contraction
- ventricular ejection
- isovolumetric relaxation
- atrial relaxation and ventricular filling
atrial contraction and ventricular filling
- atria contract, ventricle relax
- ventricular pressure is LESS than atrial and arterial pressure
- AV valves open, semilunar valves closed
isovolumetric contraction
- atria relax, ventricles closed
- ventricular pressure is greater than atrial pressure but less than arterial trunk pressure
- AV valves and semilunar valves closed
ventricular ejection
- atria relax, ventricles contract
- ventricular pressure is GREATER than both atrial pressure and arterial trunk pressure
- AV valves closed, semilunar valve open
isovolumetric relaxation
- atria and ventricles are relaxed
- ventricular pressure is greater than atrial pressure but less than arterial pressure
- both valves closed
atrial relaxation and ventricular filling
- atria relax, ventricles relax
- ventricular pressure is less than BOTH arterial and atrial pressure
- AV valves open, semilunar valves closed
cardiac output
amount of blood pumped by single ventricle in one minute
cardiac output is a measure of
effectiveness of CV system
CO increases in
healthy individuals during exercise
formula for cardiac output (CO)
heart rate (BPM) x stroke volume (SV) = cardiac output (CO)
patient HR 75 BPM, stroke volume is 70ml/beat. what is CO
75 beats/min x 70 ml/beat = 5250 ml/min = 5.25 L/min
stroke volume
amount of blood ejected in one beat from one ventricle
what influences stroke volume
venous return
inotropic agents
afterload
venous return
volume of blood returned to the heart
venous return is directly related to
stroke volume
venous return determines amount of
ventricular blood prior to contraction (EDV)
volume of blood determines
preload (pressure stretching heart wall before shortening)
Frank-Starling law (Starling’s Law)
as EDV increases, the greater stretch of heart wall, results in more optimal overlap of thick and thin filaments
starling’s law suggests that the heart
contracts more forcefully when filled with more blood so SV increases
what factors increase venous return
increased venous pressure
increased time to fill
venous pressure increases during
exercise as muscles squeeze veins
slower heart rates impact on venous return
time available to fill increases with slower heart rate (high-caliber athletes with strong hearts)
steps of venous return
- increased venous return (occurs with greater venous pressure or slower heart rate
- increases stretch of heart wall (preload) which results in greater overlap of thick and thin filaments within sarcomeres of myocardium
- additional crossbridges form and ventricles contract with greater force
- stroke volume increases
inotropic agents effect on stroke volume
- positive inotropic agents
- increased Ca2+ levels in sarcoplasm results in greater binding of Ca2+ to troponin of thin filaments within sarcomeres of myocardium
- additional crossbridges form, and ventricles contract with greater force
- stroke volume increases
inotropic agents
substances that act on the myocardium to alter contractility
positive inotropic agents
e.g., stimulation by sympathetic nervous system
venous returns ____ stroke volume
increases SV
inotropic agents _____ stroke volume
positive inotropic agents increases SV
afterload
resistance in arteries to ejection of blood
afterloads effect on stroke volume
- artherosclerosis, deposition of plaque on inner lining of arteries is typically only a factor as we age
- arteries become more narrow in diameter
- increases the resistance to pump blood into arteries
- stroke volume decreases