Cardiovascuar System Flashcards
1
Q
what are the functions of the cardiovascular system
A
- carry oxygen, nutrients( proteins, fats and carbs) and hormones to tissues and ograns
- carry metabolic waste to lungs and kidneys
- thermoregulation
2
Q
what is path of blood flow
A
lungs - pulmonary veins - left atrium- left ventricle - aorta - body to cranial and caulal vena cava - right ventricle - pulmonary artery - lungs
3
Q
what is the pulmonary circuit
A
- right ventricle to pulmonary artery to pulmonary veins to left atrium
4
Q
what is the systemic circuit
A
- left ventricle to aorta to body to cranial and caudal vena cavae to right atrium
5
Q
what is the heart beat
A
- S1 (lub) beginning of ventricle systole (contraction of cardiac muscles) = tricuspid and mitral (bicuspid valves)
- S2 (Dub): end of ventricular systole (aortic and pulmonary valves close )
- normal rate at rest is 25-30 beats per minute, average is 35 beats per minute
- variations represent differences in the size of the horse, the size of the horses heart, breed, temperament,age gender and fitness level
6
Q
what is blood pressure
A
- measured as systolic pressure/ diastolic pressure
- noaml systolic blood pressure (SBP ) ranges from 110-160 mm Hg for a horse at rest
- normal diastolic pressure (DBP) ranges from 90-110 mm Hg for a horse at rest
- mean arterial pressure (MAP) ranges from 110-120 mm Hg for a horse at rest
7
Q
what are a horses blood parameters
A
- horse has about 80ml of blood per kg of body weight ( the weight of a horses blood is about 10% of its body weight)
- total blood volume as a ratio of body weight provides a measurement to the horses fitness
8
Q
how many RBCs do horses have
A
- horse has 7-11 million red blood cells per microliter of blood
- ## compared to a humans of 4.2-5.4 million
9
Q
how many haemoglobin do horses have
A
11-19 gm haemoglobin per decilitre blood
10
Q
what is the PCV of a healthy horse
A
- 37-42%
11
Q
how many erthrocytes does a horse store and where are they stored
A
- 30% of the horses erythrocytes are stored in the spleen and released when needed to meet higher oxygen demands
- the maturation of red blood cells normally take 5-7 days during times of high demand this time is reduced to two days
- erythropoietin stimulates the production and matureation of red blood cells
12
Q
what is cardiac output
A
- heart rate X stroke volume (stroke volume is 900-1300ml)
- cardia output is measured in volume of blood pumped per minute
13
Q
what is stroke volume determined by
A
- structural integrity of the heart
- myocardial contractibility
- flow resistance
- ventricle fillability
- size of the heart ( a function of muscularity)
14
Q
what is the heart size of the horse
A
- average horse heart is 0.6% of body weight
- average thoroughbred horse heart is 0.85 to 1.0% of body weight
- suggests that selection for faster racing speed indirectly selects for larger heart size
15
Q
what are the effects of exercise
A
- increases heart rate = when exercise begins, the horses blood vessels dilate and blood pressure drops. Drop in blood pressure detected by baroreceptors that signals heart to beat faster
- increases packed cell volume by releasing erythrocytes from the spleen = exercise stimulates the adrenal glands to release epinephrine which induces splenic contractions (packed cell volume will rise from a resting level of about 40% to as much as 65%
- stroke volume increases
- repartitions blood flow from organs to skeletal muscles
16
Q
what does cardiovascular conditioning do to the horse
A
- reduces resting heart rate
- reduces heart rate at a specific level of exercise
- decreases heart rate recovery time (time it takes for heart rate to return to resting level after strenuous exercise)
- increase capillarity of lungs and muscle tissue
- increase heart size
- increases haemoglobin oxygen affinity
17
Q
what is the respiratory system
A
- carries air from the atmosphere to gas exchange regions of the lungs and back
- the lungs are responsible for gas exchange
18
Q
what type of breather is the horse
A
- obligate nasal breather
19
Q
how does air pass through the respiratory system
A
- air passes through the horses respiratory system through the nostriles and then proceeds through the nasal cavities, pharynx, larynx and trachea before entering the lungs
20
Q
what happens when air gets to the lungs
A
- within the lungs (contained within the thoracic region), air moves through bronchial trees, bronchioles, alveolar ducts and finally to the alveoli, where gas exchange takes place
- air passes easily between the alveoli of the horse
21
Q
what is the devision of the respiratory tract
A
- the division of airways within the lungs is monopodial with symmetric irregulat branching and a decrease in the diameter of the passages with each division
- there are 38-42 divisions of the airways from the trachae to the alveolar ducts resulting in a total of 1010 to 1011 alveoli with a total surface area that can reach 2500 m2
22
Q
what is the 4 phase breathing pattern
A
- forcible inhalation
- passive exhalation
- forcible exhalation
- passive inhalation
23
Q
what is minute ventilation
A
- function of tidal volume (Vt) and respiratory frequency (fR)
- at rest Vt ranges from 5 to 6 litres for a 500 kg thoroughbred
24
Q
what is the rate of air movement
A
- ( atmospheric pressure - alveolar pressure)/airway resistance
- sources of airway resistance for horse at rest
- nasal passage 50%
- remaining upper airway 30%
- intrathoracic airways 20%
- minute volume increases both respiratory rate and tidal volume increases
- lung complience increases because surfactant secretion is induced by increased tidal volume
- proportion of dead space ventilation is reduced
25
Q
how does turbulence increase mitigated
A
- flaring of nostrils
- dilation of larynx
- aligning pharynx-larynx - trachea
26
Q
what is LRC
A
- locomotor respiratory coupling
- phase relationship between the horses stride and respiratory rate that occurs at the canter and at the gallop
- at a gallop, the average respiratory rate is 110-130 breaths per minute and tidal volume is 10 leters
27
Q
conditioning and respiration
A
- the horses lung capacity is fixed
- conditioning acts to strengthen muscles associated with respiration
- facilitates alveolar recruitment
28
Q
what is the goal of conditioning
A
- improve horses ability to produce energy via the metabolic pathway appropriate to the dicipline
29
Q
factors contributing to arterial hypoxaemia during intense exercise
A
- shunting of pulmonary arterial circulation to pulmonary venous circulation occurs; unoxygenated blood mixes with reoxygenated blood and lowers arterial oxygen pressure
- improveed pulmonary perfusion and high rates of blood through pulmonary circulation in conditioned horses reduces fusion time
- high pulmonary pressure causes plasma to leak from capillaries and increases the thickness of the diffusion area
30
Q
horse notes
A
- horses to not breath through their mouths
- because of the LRC, respiratory rate = stride rate at canter and gallop
- the amount of air passing into and out of lungs is directly proportional to speed of horse
- air resistance is 90% in upper proportion during inhalation and 55% in lungs during exhalation
- overtightening girth/cinch limits performace by decreasing effectiveness of muscles that move forelegs not by limiting lung expansion
- horses expand and contract chest when breathing at rest, walk or trot and when blowing hard after workout; during canter and gallop all air movement is affected by movement of diaphragm
- horses hold their breath when they clear a jump and exhale on their landing
- conditioning has little effect on changing airway function
- pulmonary blood vessels pressure rises 4-5 fold during intense exercise; the very thin walls of pulmonary blood vessels can easily leak or rupture during this time
