cardiovascular and respiratory system Flashcards
why are drugs prescribed
treatment for chronic conditions eg. diabetes
prevention of medical problems i.e. primary prevention of heart disease or vaccinations
short term management of acute problems i.e. antibiotics for infections
prescriptions of non-pharmaceuticals eg. urinary catheters
describe pharmacodynamics
what the drug does to us
involves the study of how a drug interacts with its target
pharmacokinetics
what our bodies do to the drug
study of how we maintain the concentration of drug in the body in the correct range
common targets for drugs
receptors
enzyme systems
transporters
phases of drug development
pre-clinical development - basic scientific understanding of disease process, molecule screening, pre-clinical testing
clinical development - initial studies in humans, initial studies in the diseased, efficacy studies, post-marketing surveillance
describe the phases of clinical trials
phase 1 studies: healthy volunteers, low doses and. short duration, strictly monitors toxicity and appropriate does - only provides indication of whether drug is safe
phase 2: affected patients , assessment of whether drug behaves as expected, additional monitoring of safety profile - only tests whether the drug does what it is supposed to
phase 3: typically assesses long-term outcomes such as mortality, heart attacks and disease progression
phase 4: after drug has been licensed - observation for unexpected problems associated with use of the drug
describe the diaphragm
the major inspiratory dome shaped skeletal muscle
muscles on inspiration
diaphragm, external intercostals, parasternal intercartilaginous muscles, scalenus, sternocleidomastoid
muscle of expiration
internal intercostals (except parasternal intercarilaginous muscles), abdominal muscles
what kind of muscles are the following:
rectus abdominis, external oblique, internal oblique and transversus abdominis
abdominal muscles
describe inspiration and expiration at rest
inspiration is active - diaphragm contracts downwards pushing abdominal contents outwards - external intercostals pull ribs outwards and upwards
expiration is passive - elastic recoil
describe pressure changes during breathing at rest
ribs and sternum elevate and diaphragm contracts
pressure outside and inside are equal then pressure inside falls so air flows in
pressure inside rises and air flows out
describe inspiration and expiration during strenuous breathing
inspiration is active - greater contraction of diaphragm and intercostals - inspiratory accessory muscles active
expiration is active - internal intercostal muscles oppose external intercostals by pushing ribs down and inwards
describe the pressure and volume changes during a breath
when no flow - Pa = 0 Pb = 0
inspiratory muscles contract, pleural pressure becomes more negative, increase in Pl, lungs expand and alveolar volume increases
Pa becomes negative allowing air to flow into alveoli
expiration begins and thoracic volume decreases
Pp and Pl return to pre-inspiration values
thorax and lungs recoil
air in alveoli compressed
Pa becomes greater than Pb and so air flows out of the lungs
what is pleural pressure
the pressure surrounding the lung, within the pleural space
function of pharynx
conducts air to larynx (chamber shared with digestive tract)
function of larynx
protects opening to trachea and contains vocal cords
function of trachea and bronchi
filters air, traps particles in mucus, cartilages keep airway open
function of alveoli
act as sites of gas exchange between air and blood
major functions of the upper airway
humidify air by saturating it with water, warm air to body temp, filters air
describe the filtering process of air
Upper airways to bronchioles are lined by pseudo-stratified, ciliated, columnar epithelium
Inhaled particles of dust/debris stick to mucus which is produced by goblet cells – mucus traps it
Mucus moves towards mouth by beating cilia
Cilia move up towards nose and mouth to cough out the debris preventing debris from entering the lung
what is the trachealis
smooth muscle in the posterior aspect of the trachea
difference between the left and right main bronchus
Right main bronchus is wider, shorter and runs more vertically than the left main bronchus
what are RARs
rapidly adapting pulmonary stretch receptors
found in epithelium of respiratory tract
cough reflex process
stimulation of RARs by an irritant
afferent info sent via vagus nerve to brain
brain sends info to diaphragm and external intercostals to induce strong contraction
air rushes into lungs
abdominal muscles contract to induce expiration
glottis opens to forcefully release air are irritants
describe the respiratory tree
made of the conducting airways and respiratory airways
airways branch into smaller and more numerous bronchioles until terminating in a group of alveoli
trachea -> bronchi -> non-respiratory bronchioles -> respiratory bronchioles -> alveolar ducts
what are the conducting airways and what do they do
trachea, bronchi and non-respiratory bronchioles
involved in conducting air into body but not involved in gas exchange
what are the respiratory airways and what do they do
from terminal bronchioles to alveoli
bronchioles with alveoli is where gas exchange occurs
what is the respiratory unit
= gas exchanging unit
consists of respiratory bronchioles, alveolar ducts and alveoli
it is the basic physiological unit of the lung
structure of alveoli
polygonal in shape, composed of type 1 and type 2 epithelial cells, have a mesh of capillaries
alevolar macrophages clean up deris
perfectly designed for gas exchange: large SA, very thin walls and good diffusion characterisitic
what is the hilum
area of lung where blood vessels and brochus enter
functions of the type 1 and type 2 epithelial cells on alveoli
type 1 - occupy 97% of the surface area - primary site of gas exchange
type 2 - produce pulmonary surfactant to reduce surface tension
blood supply to lungs
two blood supplies:
pulmonary circulation - brings deoxygenated blood from heart to lung and oxygenated blood from lung to heart
bronchial circulation - brings oxygenated blood to lung parenchyma
describe the structure of arteries
thin walled
highly compliant
larger diameter
low resistance
the alveolar-capillary network
gas exchange occurs here through the dense mesh-like network of capillaries and alveoli
distance between alveoli and RBC is only 1-2µm making it ideal for gas exchange
RBCs pass through capillaries in less than one second
which direction do gases move
down their pressure gradients - from high to low
pulmonary circulation
Oxygen depleted blood
Passes from heart to lungs
Returns oxygenated blood to heart
systemic circulation
Oxygen rich blood
Passes from heart to rest of body
Returns deoxygenated blood to heart
describe the mediastinum
chest not including lungs
superior mediastinum boundaries - T1 posteriorly to sternal angle
inferior mediastinum is has an anterior (fat and thymus), middle (heart) and posterior (aorta and oesophagus) part - boundaries are from sternal angle to skeletal muscle of diaphragm
layers of the heart
endocardium (inner), myocardium, pericardium
what are trabeculae (heart)
ridges which increase flow of blood by causing turbulence
layers of the pericardium
fibrous layer - tough outer layer which anchors heart to diaphragm - Prevents rapid overfilling of the heart but can also restrict if there is an accumulation of fluid (pericardial effusion) compressing the heart, especially its right side and reducing the cardiac output serous layer - has two layers: an outer parietal layer and an inner visceral layer Pericardial space (pericardial cavity) is between these two serous layers – has a small amount of lubricating serous fluid which reduces friction of the layers during heart beats
function of the two vena cava
superior VC - takes deoxygenated blood from head and neck and upper limb to heart
inferior VC - takes deoxygenated blood from below level of heart to heart
main layers of the aorta
tunica intima, media and adventitia
first branch of the aorta
left and right coronary arteries which supply blood to heart
describe the brachiocephalic trunk
splits into the right common carotid artery (goes to head and neck) and the right subclavian artery (upper limb)
describe the last two branches of the aorta
left common carotid artery goes to head and neck
left subclavian artery gos into the axillary artery and supplies upper limb and armpit
function of ductus venosus
allows blood to bypass liver to the IVC - at birth this closes and becomes the ligamentum venosum
function of the foramen ovale
allows blood to flow from RA to LA in foetus
function of ductus arteriosus
links pulmonary trunk with the aorta allowing blood to flow into the systemic circulation of the foetus
how are nutrients and oxygen delivered to foetus
umbilical cord connects placenta to foetus so umbilical vein can deliver
difference between foetal RBCs and maternal RBCs
foetal RBCs have more haemoglobin and this haemoglobin has a higher affinity for O2
what is the fossa ovalis
embryological remnant of the formamen ovale
what are aortic sinuses
dilations just above the aortic valve - 3 of them - 2 arise from the left and right coronary arteries
crista terminalis
at the opening of the right atrial appendage and is the site of origin of the pectinati muscles
coronary sinus
collection of veins joined together to form a large vessel that collects blood from the myocardium - opening of coronary sinus is where the venous blood from the heart enters
pulmonary veins
4 in total - left and right inferior and left and right superior
carry oxygenated blood to the LA
which ventricles is thicker and why
LV is 3x thicker as it has to pump blood to the whole body
describe atrial septal and ventricular septal defects
present at birth
small holes sometimes close themselves and larger ones will compromise the lungs and heart due to increased bp
describe atrioventricular septal defects
large holes between atria and between ventricles - requires surgery as it will compromise the patient leading to breathing problems, weak pulse, racing heart beat and tiring easily
four heart valves and their locations
tricuspid - RA and RV
bicuspid (mitral) - LA and LV
aortic semilunar - LV and aorta
pulmonary semilunar - RV and pulmonary artery
structure of semilunar valves
half moon shaped structure
no chordae tendineae
how the atrioventricular valves work
as pressure increases in ventricles, valve leaflets come tightly together, they are prevented from flapping back into atrium by chordae tendinae and papillary muscles anchoring the valve tightly in place
opening and closing of AV valves
blood fills atria, putting pressure on AV valve forcing it open
ventricles fill, AV valve flaps hang into ventricles
atria contract forcing additional blood into ventricles
ventricles contract, blood is forced agains AV valve cusps
AV valves close
papillary muscles contract and chordae tendineae tighten preventing valve flaps from everting into atria
opening and closing of semilunar valves
ventricles contract, intraventricular pressure rises, blood is pushed up against semilunar valves forcing them open
as ventricles relax and pressure falls, blood flows back from arteries filling the cusps of S valves forcing them to close
why is coronary artery disease so serious
CAs are end arteries meaning they are the only blood supply to the tissue they are supplying - if blocked, the tissue it is supplying will be killed
what does blockage of coronary arteries lead to
ischaemia - restriction in blood to tissue causing a shortage of O2 that is needed - results in collateral circulation developing
infarction- death of tissue
what is a coronary artery bypass graft
if there is a CA blockage there may be a cholesterol build up
saphenous vein is often used to bypass blockage
internal mammary or internal thoracic artery can be used and is sometimes preferred as it is an artery doing an artery’s job
function of the moderator band
it is a thickening of muscle present in the right ventricle and carries the right bundle branch to the anterior papillary muscle
allows for more rapid conduction across to the anterior papillary muscle and helps with conduction times
what are purkinje fibres
specialised conducting fibres, bigger than cardiac myocytes and create a synchronised contraction across the ventricles, thus maintaining our regular heart rate
components of the upper respiratory tract
nasal cavity, pharynx and larynx
components of the lower respiratory tract
trachea - splits into left and right bronchus
primary bronchi - superior and inferior lobe bronchus in both left and right lungs and in the right lung there is also the middle lobe bronchus
lungs
functions of the respiratory tract
conduction of air (warms and humidifies)
respiration (gas exchange)
protection against pathogens
main components of the pharynx
Nasopharynx – base of skull to soft palate
oropharynx – soft palate (uvula) to epiglottis (elastic cartilage)
laryngopharynx – epiglottis to where the bifurcation occurs to the oesophagus and the trachea
food passes through the oropharynx and laryngopharynx
what lines most of the respiratory pathways
pseudostratified ciliated columnar epithelium with goblet cells
how many lobes in each lung
left - 2
right - 3 lobes
functions of the CV system
Transport of nutrients, oxygen, waste products around the body
Transfer of heat – generally core to skin
Buffers body pH – when cells metabolise they release carbon dioxide altering pH – so CV system controls the pH
Transport of hormones eg. Adrenaline from adrenals
Assists in response to infection
Assists in formation of urine-filtration and circulation – takes blood to kidneys
diastole
phase of heartbeat when heart muscles relax and chambers fill with blood
which side of the heart has a higher pressure
left - if there is a hole in septum, blood go from an area of high to low pressure
what is ventricular hypertrophy
remodeling- increase in chamber size- caused by pressure overload
what are the different heart sounds
One sound is the sound of AV valves closing and the other sound is the sound of pulmonary and aortic valves closing
A third heart sound may be due to oscillation of blood flow into ventricle
systole
contraction
stroke volume
amount of blood ejected per beat
the more the heart fills up the harder it will contract therefore the bigger the stroke volume
what is a heart node
a specialised type of tissue that behaves as both muscle and nervous tissue
generates nerve impulses when in contracts
describe the sinoatrial node
located in the upper wall of RA
pacemaker cells are located here
impulses are generated here
electrical excitation pathway in the heart
impulse generated by pacemaker cells in SA node - spreads through atria walls via gap junctions causes atria walls to contract and so blood moves into ventricles
impulses converge at AV node in AV septum - AV node delays the impulses to ensure atria has time to fully eject blood into the ventricles before ventricle systole
impulse passes into AV bundle and is transmitted to the purkinje fibres of ventricles
what influences the rate at which the SA node generates impulses
the autonomic NS
SNS increases firing rate of SA node – increases heart rate
PSNS decreases firing rate of SA – decreases heart rate
describe the AV bundle
Right bundle branch – conducts the impulse to the purkinje fibres of the right ventricle
Left bundle branch – conducts impulse to the purkinje fibres of the LV – left ventricle is much larger so left bundle branch is much larger - Branches go on to activate the anterior and posterior papillary muscles, interventricular septum and walls of LV
describe purkinje fibres
abundant with glycogen and have extensive gap junctions
located in ventricle walls and can rapidly transmit cardiac action potentials from the AV bundle to the myocardium of ventricles
having more gap junctions than the AV nodal cells and surrounding myocytes means they can transmit impulses 6x faster than ventricular muscles and 150x faster than AV nodal fibres
describe the SA nodal action potential
Conductive cells contain a series of sodium ion channels that allow a normal and slow influx of sodium ions – causes membrane potential to rise slowly from an initial value of -60mV to -40mV
movement of Na ions creates spontaneous depolarisation
Calcium ion channels open and Ca enters cell, further depolarising it until approx. 5mV
Calcium channels close and K channels open allowing outflux of K and resulting in repolarisation
Membrane potential reaches approx. -60mV - K channels close and Na channels open again to repeat
purkinje action potential
Rapid depolarisation period then there is the plateau phase in which membrane potential (MP) declines slowly due to the opening of the slow Ca channels, allowing Ca to enter while few K channels are open, allowing K to exit
When MP reaches approximately zero the Ca channels close and K channels open – repolarisation
MP drops until it reaches resting levels once more and then repeats
what are adrenoceptors
receptors that bind adrenergic agonists
exist in alpha and beta forms
which adrenoceptor is predominantly found in the heart
B1
activation of B1 receptor can lead to
Positive inotropy – increased strength of contraction
Positive chronotropy – increase heart rate
Positive lusitropy – increased rate of relaxation
Positive dromotropy – increases conduction velocity
where does the vagus nerve terminate
right vagus- SA node
left vagus- AV node
factors controlling flow within vessels
length and diameter of vessel
viscosity of liquid
pressure gradient across length of the vessel - increasing pressure gradient increases flow
how can blood viscosity be increased
Dehydration coupled with immobility increase risks of an increased blood viscosity and so decreased blood flow – can lead to deep vein thrombosis
importance of blood vessel radius
As the radius of the wall gets smaller, the proportion of the blood making contact with the wall will increase - the greater amount of contact with the wall will increase the total resistance against the blood flow
mechanisms that encourage blood flow in veins
Valves direct blood towards heart
Skeletal muscle pump – veins are often deep in muscles, when these muscles move they have a peristaltic effect in moving blood back to heart
Respiratory movements aid venous return – breathing changes pressure in thoracic cavity which aids the return
Sympathetic nerves - noradrenaline constricts veins - increased venous return to the heart – by creating pressure gradient
what is preload and why can it be a problem
Venous return to the right ventricle is termed PRELOAD
If PRELOAD increases the heart has to work harder to pump the blood out. This can be a problem in: heart failure and coronary artery disease - angina
nitrates reduce preload on the heart to reduce cardiac work
baroreceptors
receptors sensitive to change in pressure
how do baroreceptors regulate bp
present in carotid sinus & aortic arch - Carotid receptor more important as it is more sensitive
baroreceptors are stretch receptors and they generate action potentials at a particular frequency at all times
Fall of blood pressure reduces stretch which reduces the frequency of action potentials to neurons in the medulla
this frequency is increased when the baroreceptors receive a stretch stimulus secondary to increase in blood pressure
efferent impulses in the form of sympathetic and parasympathetic nerves arise. Impulses are carried to the heart via the parasympathetic Vagus nerve
ways to affect BP
Cardiac output
TPR (total peripheral resistance) by affecting radius of vessels
Local controls
Capillary fluid shift – changing hydrostatic or osmotic pressure
what cells line all vessels and the inside of the heart chambers
endothelial cells
role of vascular smooth muscle in vessels
Present in all vessels with the exception of the smallest capillaries
Determines vessel radius by contracting and relaxing
Secretes an extracellular matrix which gives the vessels their elastic properties
Can multiply in some diseases - eg hypertension
why is arterial elasticity important
Compliance is important to allow large arteries to act as a pressure reservoir
This prevents pressure falling to 0 as blood leaves the arteries during diastole
what is blood pressure
circulation of fluid contained within a space of definite volume
pressure falls as blood fills ventricles and in atrial systole
how do each vessels structure link to its function
aorta and arteries contain a small amount of blood at high pressure so are very thick walled/elastic
arterioles are a variable resistance system which distributes the blood - dissipate most of the pressyre
capillaries have a vast surface area where the interchange of substances with the extracellular fluid of the tissue occurs - as little as one cell thick to allow rapid exchange within tissues
venules, veins and vena cava - a collecting and reservoir system which contains most of the blood at low pressure - very distensible
