circulatory system #2 Flashcards
what are the three main types of blood vessels?
- arteries
- capillaries
- veins
what are arteries?
- Thick elastic tubes lined with smooth muscle
- carry oxygen rich blood away from the heart
what do arteries branch into?
arterioles
what are capillaries?
- tiny vessels that connect arterioles and venules
- they carry gases, nutrients, and wastes
what are veins?
- thinner, non-elastic tubes
- they carry deoxygenated blood to the heart
what do veins branch into?
venules
does the heart need external nerve stimulation to contract?
no
what type of working muscle is the heart?
myogenic muscle
what is tachycardia?
heart beating at 100bpm or more at rest
what type of stimulation slows the heart?
parasympathetic stimulation
where does electrical stimulation originate?
in the heart
is the heart dependent on the brain?
no
what does “SA” stand for?
sinoatrial
what does the Sinoatrial (SA) node do?
- “pacemaker”
- sends out an electrical signal that spreads over the two atria and they contract simultaneously
where is the SA node located?
in the wall of the right atrium
what do purkinje fibres do?
they cause the left and right ventricles to contract
what is the order of the transmission of contraction?
- SA node sends out electrical stimulus to cause atria to contract
- impulse reaches the AV node
- impulse pauses
- impulse then passes through the “Bundle of His”
- impulse reaches left and right bundle branches
- impulse continues through the purkinje fibres causing the ventricles to contract from the bottom up forcing blood to the pulmonary arteries and aorta
what causes the ventricles to contract?
impulse reaching the purkinje fibres
what is the flow of blood through the blood pathway?
heart -> aorta -> arterioles -> capillaries -> venules -> veins -> vena cava -> heart -> lungs
what is arterial flow?
- artery relaxing and contracting as blood is pumped out of the heart
what is pulse?
change in diameter of the arteries following heart contractions
what controls blood flow from arterioles to capillaries?
pre-capillary sphincters
when do arterioles open?
when cells in an area require blood
how many square km of capillaries are in our bodies?
6.3km squared
where is the flow of blood slowest?
in capillaries
how much of total blood volume can be found in veins?
about 65%
what happens to blood pressure when blood moves into veins?
blood pressure drops
what are venous valves?
- valves within a vein
- they open in one direction, preventing blood from falling back down
- blood pools on top of valve
when do venous valves open?
once blood pressure is great enough, the valves are forced open
what are the two nervous systems?
- sympathetic nervous system
2. parasympathetic nervous system
what does the sympathetic nervous system do?
- fight or flight
- increases heart rate
- increases blood flow to tissues, brain and leg muscles
- vasodilation/vasoconstriction
what is vasodilation?
the relaxation of blood vessels in order for blood to get through to other areas of the body
what is vasoconstriction?
the narrowing of a blood vessel in order to slow blood flow
what does the parasympathetic nervous system do?
- rest and digestion
- decreases heart rate
- conserves energy
what instrument is used to measure electrical activity in the heart?
electrocardiograph
what is the first wave in an ECG?
P wave
what is the second wave in an ECG?
QRS wave
what is the third wave in an ECG?
T wave
what is the P wave?
- first wave in an ECG
- atrial contraction
what is the QRS wave?
- second wave in an ECG
- ventricular contractions
what is the T wave?
- third wave in an ECG
- ventricular recovery (relaxation)
why does atrial recovery not show up on an ECG?
- because atria are such small chambers, they don’t have time to relax
what part of impulse does the P wave represent?
represents electrical impulse travelling from the SA node to the AV node
what part of impulse does the QRS wave represent?
represents impulse travelling down to the Bundle of His and ending up in the Purkinje Fibres
what part of impulse does the T wave represent?
represents the recovery of impulse
what is the average resting heart rate of an adult?
70-75bpm
what is the average resting heart rate of an adolescent?
80-100bpm
what is the formula to find maximum heart rate?
220 - (your age) = max HR
what happens to your maximum HR as you get older?
your maximum HR decreases
what is bradycardia?
- very slow heart rate
- less than 60bpm
- fit individuals with strong hearts may have a slower heart rate
what is blood pressure?
- blood exerts pressure on artery walls, as blood surges through arteries they vasodilate to accommodate the pressure and then vasoconstrict with decreased pressure/blood flow
what is systolic pressure?
pressure that blood exerts on vessel walls during ventricular contraction (top number in a blood pressure reading)
what is diastolic pressure?
pressure that blood exerts on vessel walls during ventricular relaxation (bottom number in a blood pressure reading)
what is blood pressure measured in?
mmHg (millimetres of mercury)
what is an average blood pressure reading?
120/80
what can cause systolic pressure to fall?
- when there is reduced filling of the ventricle (bleeding or hemorrhage)
what happens to blood pressure as you get further away from the heart?
blood pressure lowers
what is a normal range for blood pressure?
110/70 - 130/80
what is a low blood pressure reading?
<90/60
what are causes for low blood pressure?
low nutrients, low blood cell count, low iron
what is a high blood pressure reading?
140/90
what are causes for high blood pressure?
high salts, high hormones, high proteins, high H2O
what is hypertension?
chronic high blood pressure
