Heart Flashcards
What are the main functions of the heart and blood?
Mechanical pump
Transport of cellular components and dissolved substances
What are the main functions of arteries and veins?
Arteries = transport blood away from the heart
Veins = Transport blood to the heart
What is the main function of capillaries?
Site of exchange of substances
What is the main function of the lymphatic system?
Return tissue fluid to systematic circulation
What species do these 3 circulatory systems match to and what type of systems are they?
- Fish = single closed circulation
- Mammal = double closed circulation
- Amphibian = incomplete double circulatory system
Fill in the blanks:
- The right atrium receives a. blood from around the body via the b.
- The left atrium receives c. blood from the lungs via the d.
a. deoxygenated
b. vena cava
c. oxygenated
d. pulmonary vein
What is the tunica interna, tunica media and tunica externa/adventitia?
Endothelial lining of the blood vessel
Concentric sheets of smooth muscle in the lining of the blood vessel
Connective tissue sheath around the blood vessel
What is the lumen of a blood vessel?
Cavity of that organ
Describe elastic and muscular arteries:
Elastic = Conducting artery, expand during systole and recoil during diastole
Muscular = Medium sized, changes (vasoconstriction/vasodilation) affect blood pressure
Describe arterioles:
Small diameter, which changes in response to local conditions e.g. O2 levels
Describe the appearance of a capillary:
Small diameter, endothelial layer only
Fill in the missing labels:
Describe the following valves (type and side of heart):
Tricuspid
Mitral
Pulmonic
Aortic
Tricuspid - atrioventricular valve, right side
Mitral - atrioventricular valve, left side
Pulmonic - semilunar valve, right side
Aortic - semilunar valve, left side
During systole, the heart muscle…
During diastole, the heart muscle…
…contracts!
…relaxes!
What is a cardiac cycle?
What are the names given to the two main parts of the cardiac cycle?
Complete contraction and relaxation of the heart
Systole and Diastole
Fill in the following blanks on the cardiac cycle:
How many chambers are in the mammalian heart?
How does the heart allow blood in, and how does it expel the blood (very basic answer)?
Which chambers collect blood and which expel blood?
4 - 2 atria, 2 ventricles
Relaxes to take blood in and contracts to expel the blood
Atrium collects blood, ventricles expel blood
Why has the left side of the heart got thicker muscle?
Which species has the tickets muscle on the left side of their heart?
It is the side that the blood is pumped out of
Birds* (left ventricular wall 3x thicker than right)
*see photos
What in the blood is transferred to and from metabolising tissues?
- oxygen and CO2
- Nutrients
- Waste
- Heat
- Hormones
What is the most common issue with the heart seen in practice and what is not?
Most common = heart disease
Least common = heart attack (usually genetic issues not lifestyle issues)
What does heart disease usually involve?
Does heart disease lead to/result in heart failure?
Valve degeneration, causes valve to become incompetent OR the heart muscle becomes diseased causing the heart to have issues with contacting or filling
No, not always
What is heart failure?
Syndrome where the heart fails to deliver blood effectively to metabolising tissues so cannot reach their requirements
In mammals what does the double circulatory system mean?
Oxygenated blood and deoxygenated blood cannot mix
What is ventricular systole and what does it result in?
What is ventricular diastole and what does it result in?
Contraction of the ventricles = cardiac output (blood leaving) and the atrioventricular valve closing
Relaxation of the ventricles = ventricular filling (blood entering) and the semi-lunar valve closing
What are the names given to the first heard sound of the heart and then the second?
First = “Lub”
Second = “Dub”
What controls the strength and rate of cardiac function?
What’s another factor that can impact the strength?
Electrical activity/Electrophysiology
Another is how much blood enter the heart as it will have to stretch more and resultantly contract with more force (hormones can also have a small impact)
How is the electrical activity of the heart measured?
What controls increases in electrical activity?
Where do the electrical currents start and finish?
With and ECG
The Autonomic Nervous System
Run from atrium to ventricle
How can blood vessels control where in the body the blood travels to?
They can constrict and dilate to let or prevent blood from passing
What is autoregulation?
Local blood flow regulation, the ability for an organ to maintain a constant blood flow despite changes in perfusion pressure
Define the definitions for the following terms:
Cardiac output
Stroke volume
Cardiac output: volume delivered into the circulation per minute
Stroke volume: volume delivered by the ventricle per beat
What is the very basic vascular system that blood follows in the mammalian body?
Leaves the heart - to the arteries - then to the capillaries which is a site of diffusion - then to portal veins lying between 2 capillary beds - then to the veins returning back to the heart
Why do birds have such efficient cardiovascular systems?
To cope with high metabolic demands, for oxygen delivery and for thermoregulation
What makes the bird and mammalian heart different when they both have 4 chambers?
(not essential to know)
The AV valves are different in structure
What does the term coelom mean when referring to birds and amphibians?
It means they don’t have a diaphragm
Where in the bird is the heart located?
Located within the cranial ventral coelom and is surrounded by air sacs
Birds empty their heart almost completely on each cardiac cycle, what does this cause?
Low end-systolic volume (pressure in left ventricle less that the pressure in the aorta causing the aortic valve to close)
What are the 5 zones of the primitive tube?
T - arterial trunk
B - bulbs cordis
V- (B and V) primitive ventricles
A - Atrium
SV - Sinous Venous
(this is similar to primitive fish and some amphibians)
How many chambers are in the fish’s heart?
How does the blood flow and how is some of it vascularised?
2 (technically 6 like primitive tube)
Flows in 1 direction through a single atrium and ventricle, some of it vascularised by gills
Where in the fish is the heart positioned?
Ventral and caudal to the gills
How many heart chambers do amphibians have?
How do they oxygenise their blood?
3 in total (frogs are beginning to develop 2 atria)
Lungs, skin and buccal cavity
Where is the heart in amphibians?
Mid cranial coelom
How many chambers do most reptiles have?
What is an example of an exception?
3 - 2 atria, 1 ventricle split into 3 by folds in muscles wall
Crocodiles have 4 (not like mammals) with 2 aortas
Where in most reptiles can the heart be found?
Where in snakes can the heart be found?
Mid cranial coelom, some very cranial (base of neck)
Cranial third of body
How does the cardio-respiratory system help fight infection?
The blood delivers white blood cells to the area of infection
How does cardio-respiratory system help maintain homeostasis in the body?
Helps maintain blood acidity, maintain electrolyte levels, helps fight infection etc.
Where is the heart located in mammals?
Ventral and centre of the thorax
How is the heart protected in mammals?
What is the heart closest associated with?
Where on the image is the diaphragm, which rib does it stop at?
If on 4 legs by the ribs and musculature for the front leg
The cranial abdomen (sometimes when imaging liver gets in the way)
Rib 6
What are some important controlling factors for venous return?
- Sympathetic nervous system
- Blood volume
- Muscle pumps
What species is the renal portal system found in?
Reptiles, birds, amphibians, most fish
What are the names of the two circuits?
How is blood distributed between the two?
Pulmonary goes to the lungs, systemic goes to the rest of the body
Volume of blood is distributed equally
In which size of species is the heart proportionally larger?
What is the heart’s approximate mass of an animals body?
Smaller animals
0.75% (increases with training)
In position to the heart, where are these features (mammal)?
Lungs
Diaphragm
Thymus
Ventral lung border
Phrenic nerve
Lungs = lateral
Diaphragm = caudal
Thymus = cranial (only present in young animals)
Ventral lung border = cardiac notch (see image)
Phrenic nerve = along top of heart on both sides
What is the area in the chest where the heart is found called and what is its other purpose?
Does it lie equally along the median plane?
Mediastinum - divides left and right pleural cavities (where lungs are found)
60% of it lies left of the median plane
Where in mammals does the right ventricle sit in relation to the left?
Is the base of a mammalian heart more ventral or dorsal?
Where does the apex of the heart sit (the pointy bit)?
Cranial!
Dorsal!
Sits in the sternum
In the mammalian heart which is larger, the ventricles or atria?
What are auricles?
Ventricles significantly larger
Earlobe shaped appendages on the atria
What side of the heart is the pulmonary artery on?
What side of the heart does the aorta come from?
The left even though it comes from the right side
The middle of the base
What are the receptors for the following neurotransmitters:
- Acetylcholine
- Noradrenaline
- Adrenaline
Acetylcholine = nicotinic arch r
Noradrenaline = a and/or β
Adrenaline = Muscarinic Arch R
Match the nerve fibre with the neurotransmitter:
Pre-G SNS Acetylcholine
Post-G SNS Adrenaline (Epinephrine)
Pre-G PSNS Noradrenaline (Norepinephrine)
Post-G PSNS Acetylcholine
Adrenal medulla Acetylcholine
Pre-G SNS Acetylcholine
Post-G SNS Noradrenaline (Norepinephrine)
Pre-G PSNS Acetylcholine
Post-G PSNS Acetylcholine
Adrenal medulla Adrenaline (Epinephrine)
What is the name given to the reflexes that regulate the ANS?
How do they work, what part of the nervous system is used?
Autonomic reflexes
They work through feedback mechanisms, which involve the afferent nervous system.
What 4 functions of homeostasis are controlled by autonomic reflexes?
- Regulation of cardiovascular
- Respiratory
- Immune
- Digestive
The SNS has 2 effects on the heart, what are they?
Acceleration of the heart rate and an increase in cardiac contractility
What are baroreceptors involved in?
Where can they be found?
Regulation of homeostasis
Carotid sinuses and Aortic arch
What are chemoreceptors involved in?
What processes do they control?
Where can they be found?
Involved in homeostasis
Detect changes in blood and environmental levels (like O2 and CO2, pH) which therefore impacts the cardio-respiratory system
Peripherally in Aorta and Carotid bodies and Centrally in the Brainstem
How do baroreceptors lower BP when there is blood loss?
Blood Loss
Baroreceptors activated (sensory cell)
Firing frequency falls along the sensory nerve fibres
BP lowered
Alters impulse frequency in motor nerve fibres
Compensatory systems/Effectors activated (increase in heart rate, vasoconstriction etc.)
Where are the sympathetic cardiac nerves found?
Within the cardiac plexus
Post-G fibres from the SNS go directly to the heat, where are the two places in the heart that they go to and how does this have an effect?
—-> All the effects have special terms, what are they?
SA Node and AV Node - controls rate and rhythm
= +ve chronotropic effect
Myocardium - controls the force of contraction
= +ve inotropic effect
How does activation of the PSNS change the +ve chronotropic and inotropic effects?
+ve chronotropic effect = decreases heart rate and rhythm
+ve inotropic effect = decreases the contractile force of the heart
What is a heart murmur?
What causes a heart murmur?
When blood flows abnormally through the heart’s valves
Heart disease, infection, illness, anaemia, pregnancy, valve deformation/birth defects
What is the difference between a systolic and diastolic heart murmur?
Systolic = during heart muscle contraction
Diastolic = during heart muscle relaxation, between the beats
What is an endotherm?
What is an ectotherm?
Endotherm: An animal that depends on its own generation of heat and is capable of doing so
Ectotherm: An animal that depends on an external source for body heat
What is a homeotherm?
What is a poikilotherm?
Is it true that all homeotherms are also endotherms and all ectotherms are also poikilotherms?
Homeotherm: An animal that can keep its body temperature at a constant (usually above environmental temp.) through metabolic activity
Poikilotherm: An animal that cannot maintain and regulate its own body temperature so through seeks this through behavioural means such as basking and burrowing
No, they can be the same but they aren’t always
What are the four physical processes of heat exchange?
Conduction
Convection (heat is transferred by movement of a heated fluid such as air or water)
Radiation
Evaporation
What are veterinary example to illustrate potential welfare implications of each of the four physical processes of heat exchange?
Conduction: paws burning, (important for heat dissipation)
Convection: (important for heat dissipation)
Radiation: heat stroke, sunburn, flies and parasites, stress (eg. milk yield production could be impacted)
Evaporation: dehydration
Where is the thermoregulatory centre located – how does it operate? (in endotherms)
The hypothalamus – has receptors that are sensitive to the temperature of the blood
List mechanisms by which endotherms respond to cold:
List mechanisms by which endotherms respond to heat:
What special adaptations do some animals have to tolerate hot / cold climates?
Vasoconstriction, hair erector muscles contracting, shivering
Vasodilation, increase sweat, decrease metabolic rate
Thickness and type of fur/feathers, type of pads, size of body and limbs, blubber, colouring, surface area to volume ratio
What is the definition of the following terms:
Thermoneutral zone
Lower and upper critical temperatures
Zone of thermal comfort
Thermal set-point
Thermoneutral zone - range of surrounding temperatures that allow the body to maintain its core temperature through just the control of dry heat loss
Lower critical temp. - the minimum temperature of the thermoneutral zone, below this the body has to bring in other mechanisms to maintain its core temperature
Upper critical temp. - maximum temperature of the thermoneutral zone, after this the bodies core temperature must be maintained through sweating
Zone of thermal comfort - when the mind expresses satisfaction towards the thermal environment
Thermal set-point - the temperature that the body is always working to be at
What happens to your thermal set-point when you have the flu?
Thermal set-point increases
What is laid down during the last six weeks of pregnancy that protects new-born lambs from hypothermia?
Brown fat around heart and kidneys (energy source)
When might cooling (in the absence of hyperthermia) be used medically?
Why might use of a Bair Hugger sometimes be necessary?
For cardiac injuries
Non-inavise way of accurately and continuously measuring core body temperature, needed in severe cases, can also assist with warming
What is the Rate of heat Storage calculation?
HS = HM - (±HCD ±HC ±HR - HE)
M = Metabolic rate*
CD = Conduction
C = Convection
R = Radiation
E = Evaporation
*Increases for every +10ºC (the Q10 effect)
Falls 10% for each ºC in temperature loss
What common congenital heart diseases develop from:
1. Failure of normal valve and great vessel (aorta/pulmonary artery) development?
2. Failure of changes to circulation at birth?
3. Failure of normal septum development?
- Mitral and tricupsid valve dysplasia: leaky heart valve
- Aortic and pulmonic stenosis: narrower outflow tract out of left or right ventricle
2. - Patent Ductus Arteriosus (PDA): Ductus arteriosus remains open, blood moves directly between aorta and pulmonary artery
- Atrial Septal Defect, Patent Foramen Ovale: blood continues to move between left and right atrium
3. - Ventricular Septal Defect (VSD): a hole between the left and right ventricle
- Atrial Septal Defect (ASD): like a patent foramen ovale potentially leads to blood flow between left and right atrium
What are the most common congenital heart diseases (in dogs, cats, horses, cows and sheep) and is there much species variation?
Mammals hearts form in a similar way to our main veterinary species so have the potential for the same issues but how common these issues are varies;
Dogs: PDA, aortic and pulmonic stenosis
Cats: VSD, PDA and mitral valve dysplasia
Horses: VSD
Cows and Sheep: VSD
Can animals have multiple congenital heart diseases at once?
Yes, but although this is rare it presents significant clinical challenges
What is aortic stenosis?
Narrowing of ventricular outflow tract between left ventricle and aorta, harder for blood to pass and increased pressure in LV so left side has to work harder resulting in its walls thickening leading to irregular beats, heart failure or even death
What is pulmonic stenosis?
The valve between the pulmonary artery and the right ventricle is too narrow, the blood pumped from here goes to the lungs. The right side therefore becomes too thick as it has to work hard dues to pressure also increasing in the RV, this causes inefficiency in the heart and can lead to a backup of blood. It can cause fainting, heart failure or even death.
What is Patent Ductus Arteriosus (PDA)?
The ductus arteriosus connects the aorta to the pulmonic artery. Blood flows from high pressure to low pressure. In mammals after birth the left side of the heart is under higher pressure than the right so blood will flow from the aorta to the pulmonary artery. This means a lot of the blood will return back to the pulmonary artery go through the lungs and straight back to the left side of the heart leading to increased volume on the left side and ultimately this will make the left atrium and left ventricle dilate. So, if left open after birth the heart has to work harder when pumping blood ultimately leading to heart failure.
