circulation Flashcards
what are the components of the the circulatory system? (3)
pumps, vessels and circulatory fluid
What are the functions of the circulatory system?
maintenance of homeostasis
mass transport of solutes and cells
transport of heat
transmission of force
What is the cardiac cycle?
one complete sequence of pumping and filling
inherent activity of the heart can be modified by outside influences
What is systolic
?
heart muscles contracts, chambers pump blood
What is the diastole?
heart muscle is relaxed, chambers fill with blood
Regulation of the cardiac cycle four steps?
1) signal from SA node spread through atria
2) signal is delayed at AV node
3) bundle branches pass signals to heart apex
4) signals spread throughout ventricles
blood returns to the heart via what?
due to contractions of skeletal muscles
what do one way valves do?
ensure direction of blood flow towards heart
Hoe does blood return back to the heart?
due to contractions of skeletal muscles
one way valves in veins ensure direction of blood flow towards heart
regulation of blood flow:
blood volume < systemic volume
blood flow is directed at active tissues
what are the control mechanisms of blood flow?
relaxing/ contracting of precapillary sphincters
constriction/ dilation of arteriols
The lymphatic system:
functions of lymph system?
fluid balance- there is a net leakage of fluid and proteins from blood capillaries
-lymph capillaries collect lost fluid and return it to blood
Defence: lymph nodes have efence cells
Lymph capillaries pick up fat absorbed by the small intestine, transfer it to blood
The lymphatic system:
How does movement work?
one way valves, contraction of skeletal muscles
lymph does not circulate in a closed circuit
The lymphatic system:
what is thymus?
the site of maturation of T lymphocytes (immune system)
The lymphatic system:
what are tonsils, what do they do?
handle infections in the mouth
The lymphatic system:
what does the spleen do?
defence
red blood cell destruction
blood reservoir
Blood:
composition?
cellular elements
plasma: blood minus the cells
blood:
Volume?
heart rate (approx. 70 beats/min) x stroke volume (75mn) –> 5.25 L/min
Blood:
Hematocrit?
packed cell volume
the normal value 45% is regulated
departures are either adaptive or pathological
What is the origin of cellular elements in the blood?
from pluripotent stem cells in bone marrow
What are leukocytes?
defense and immunity 5000-10000/mm3
what are erythrocytes?
O2 and Co2 transport5-6 millionmm3
What are platelets?
blood clotters 250000-400000/mm3
Erythrocytes:
shape?
biconcave disk
small size
large surface area
Erythrocytes:
content?
Hemoglobin
spectrin
glycolytic enzyme
carbonic anhydrase
no organelles or ribosomes
mammals: no nucleaus
Erythrocytes
what is spectrin?
predominant component of the membrane skeleton
Erythrocytes
what is glycolytic enzyme?
active carb metabolism
Erythrocytes
what is carbonic anhydrase?
catalyzes CO2 bicarbonate
what is the process of the formation of erythrocytes?
takes four days, from stem cell to erythrocyte
begins in bone marrow, completed in circulating blood
initiated when not enough O2 reaches tissue
What is the rate of formation of erythrocytes?
100 million cells per minute
normally balanced with erythrocyte destruction
can exceed destruction under conditions of tissue oxygen deficiency
Destruction of erythrocytes
break apart in capillaries due to mechanical stress
eaten by macrophages in spleen and liver
Human red blood cells:
life time?
life of 120 days
lack mitochondria and nucleus
Blood loss protection:
in severe blood loss
decrease in blood pressure will result in decrease blood flow from damaged area
constriction of blood vessels –> decrease blood flow
coagulation
Blood loss can be halted by what?
platelet plugs(form first)
fibrin clots (form later)
What are platelets activated by?
exposed collagen fibers in damaged tissue of vessel wall
foreign surfaces
thrombin
What do platelets do upon activation?
form platelet plug
release clotting factors
change shape
what do platelets contain?
actin and myosin to help contract
chmicals that help the coagulation process to begin
chemicals that attract other platelets
chemicals that stimulate blood vessel repair
chmicalls that stabalize blood clot
What is stage 1 of clot formation?
sensing of damage
clotting factors released from platelets are injured tissue
plasma protein sythesized in liver circulate in inactive form
What is stage two of clot formation?
Thrombin Activation
- thrombin is enzyme absent from circulating blood
- prothrombin circulates in plasma
thrombin –> fibrinogen –> fibrin
Stage three of clot formation
clot formation
platelets
-release substance that cause contraction of blood vessels
- sticky platlets form plug
- initiate formation of fibrin clot
Fibrinogen - soluble protein in plasma
fibrin- insoluble, fibrous protein
clot seals wound intil vessel wall heals
clotting dynamic:
opposing clotting
heparin
- anticlotting agent
clotting dynamic
favoring clotting
activated platlets, activated blood factors, thrombin, fibrin
Clot dissolution is caused by what?
Fibrinolysis causes dissolution of fibrin and thrombus
What is plasmin?
main enzyme of fibrinolysis
cleaves fibrin in multiple locations
acts to dissolve a fibrin clot
produced in inactive form in the liver
What is plasminogen?
cannot cleave fibrin, but has an affinity for it
incorporated into the clot when it is formed
Clot lysis is what?
complex process involving protocolytic enzymes, activators and inhibitors of plasmin and other proteases
Cardiovascular disease:
LDL
HDL
LDL dilivers cholesterol to cells for membrane production
HDH scavanges excess cholesterol for return to the liver
When is there a risk of heart risk?
high LDL to HDL ratio
als inflammation
What are atherosclerosis caused by
the buildup of fatty deposits within arteries
What is heart attack or myocardial infraction?
damage or death of cardiac muscle tissue resulting from blockage of one or more coronary arteries, whcih supply O2 rich blood to heart muscles
What is angina pecoris
chest pain caused by partial blockage of the coronary artery
What is a stroke?
death of nervous tissue in the brain, usually resulting from rupture or blockage or arteries in the head
effect of stroke depends on the extent and location of damaged brain tissue
