Unit 3: circulation Flashcards
Structure of blood vessels Artery and Veins
Tunica media is thicker in the artery because of high blood pressure
Elastic fibers: found in the tunica media
Tunica media: simple squamous cell
Endothelium: lines the inside of the heart
Arteries function
-Carry blood away from the heart
-Usually carries oxygenated blood
-Arteriole = small artery
-Have thicker muscle (tunica media) as they need to withstand the pressure coming from heart
Veins function
-Carry blood to the heart
Usually carries deoxygenated blood
-Venule = small vein
-Have thinner muscle walls as the blood in veins is under lower pressure Contain valves (one-way doors) to prevent backflow of blood
Capillaries
-Also made up of tunica intima
-Very thin
-Composed of the tunica intima only (endothelium and basement membrane)
-Site of exchange between blood plasma and cells
-Vary in diameter and permeability depending on location
-Simple diffusion and cellular respiration
conduction system of the heart
The heart is special because it contains specialized muscle tissue that can repeatedly and rhythmically generate an action potential to control the flow of blood through the heart
conduction of an electrical impulse= one heart beat
it contracts on its own
in one heart beat (steps)
- Blood flows into the atria
- An impulse starts at the SA node and sends signals to both atria to contract
- Both atria contract
- Atrioventricular valves open (tricuspid and bicuspid valves) and blood flows into the ventricles
- Impulse travels to the AV node with a slight delay to allow full emptying
of the atria - Impulse continues to the AV bundle and to the Purkinje fibers
- Both ventricles contract (atria relax)
- Atrioventricular valves close (“lub”) (tricuspid and bicuspid)
- Semilunar valves open and blood flows into the aorta and pulmonary trunk
- semilunar valves close (“dub”) (ventricles relax)
Electrocardiogram (ECG)
The small P wave represents the depolarization of the atria. Atria begins contracting approximately at the middle of P wave.
The large QRS complex represents the depolarization of the
ventricles, which requires a much stronger electrical signal because of the larger size of the ventricular cardiac muscle. Ventricles begin to contract as the QRS reaches the peak of the R wave
The T wave represents the repolarization of the ventricles. Repolarization of the atria occurs during the QRS complex, which masks it on an ECG
systole vs diastole
Systole= contraction
Diastole= relaxation
Heart rate
Left alone, the SA node will maintain a constant heart rate However, other factors also affect heart rate:
- Autonomic Nervous System
-Sympathetic: increase HR, increase HC
-Parasympathetic: decrease HR - Hormones
– Epinephrine, norepinephrine: increased HR, increased HC - Ions in blood (can affect conduction system)
-Na+, K+: decrease HR, decrease HC
-Ca2+: increase HR, increase HC - Body Temperature
– High Temp: increase HR
-Low temp: decrease HR, decrease HC
regulation of heart rate: automatic nervous system
Regulated by cardiovascular Centre (group of cells that controls heart rate)
Sympathetic nerves increase HR and HC
Parasympathetic (VAGUS) nerves decrease HR
Medulla to the heart
Blood pressure
Pressure exerted by blood on the inside wall of arteries due to ventricular contraction
Systolic pressure: the increased pressure that results from blood leaving heart (ventricle contraction)
Diastolic pressure: the resultant lower pressure that is still exerted when the ventricles relax
blood pressure values
Normal Blood Pressure Values
Systolic Blood Pressure ≈ 120 mm Hg
Diastolic Blood Pressure ≈ 80 mm Hg
Hypotension
Blood pressure that is lower
than the average
Systolic < 100 mm Hg
Hypertension
Blood pressure that is higher than the
average
Systolic/Diastolic > 140/90 mm Hg
regulation of blood pressure
- Autonomic Nervous System: affects blood pressure by changing heart rate or diameter of blood vessels
- Autoregulation: active tissue cells and also cells in blood change blood pressure indirectly by releasing chemicals that change the diameter of blood vessels
- vasodilating substances
-vasoconstricting sunstances O2 - Endocrine system: hormones that can be produced that can change blood viscosity
or ion levels
* Aldosterone → Water retention → high BP
* Epinephrine → Vasoconstriction → high BP
Arterial pulse
Where the alternate expansion and recoil of an arterial muscle wall can be felt with each contraction of the left ventricle (no other muscles are in the way)
-Used to measure heart rate
-Most common locations include:
* Wrist → radial artery
* Neck → carotid artery
