1
Q
What do striations reflect in cardiac myocytes?
A
they reflect the repeated sarcomeres in series
2
Q
What do sarcomeres enable?
A
efficient, forceful and co-ordinated contraction via the sliding filament mechanism
3
Q
What do sarcomere mutation lead to?
A
hypertrophic or dilated cardiomyopathies
4
Q
What is released from damaged sarcomeres and what is it a key biomarker of?
A
troponin - MI
5
Q
What is contraction initiated by? What type of control is this?
A
pacemaker cells - involuntary control
6
Q
What can damage to intercalated discs or gap junction lead to?
A
arrhythmias
7
Q
What are intercalated discs?
A
specialised cell-cell junctions containing desmosomes and gap junctions
8
Q
What do gap junctions allow? Where are they found?
A
rapid electrical conduction between cells - ensures co-ordinated contraction
intercalated discs
9
Q
What is the function of desmosomes and where are they found?
A
prevent cells from pulling apart during forceful contraction
10
Q
What are the specialised features of cardiac myocytes?
A
- striated and branched (striation reflects repeated sarcomeres)
- involuntary control (contraction initiated by pacemaker cells)
- intercalated discs (contain gap junctions and desmosomes)
- abundant mitochondria
11
Q
What do cardiac myocytes have a lot of? What does this ensure?
A
abundant mitochondria - ensures high ATP production needed for continuous aerobic activity
12
Q
What is a cardiac syncytium?
What two syncytium are there?
A
group of cells that function as a single co-ordinated unit
atrial and ventricular
(all atrial muscle cells contract together, all ventricular muscle cells contract together)
13
Q
What are atrioventricular cells anchored to?
A
fibrous skeleton which sits between atria and ventricles
14
Q
What prevents ‘free’ conduction of electrical impulse from atria to ventricles?
A
fibrous tissue
15
Q
What does fibrous tissue do?
A
prevents ‘free’ conduction of electrical impulse from atria to ventricles
16
Q
What enables the heart to be as one?
A
the syncytium
17
Q
What is defibrillation used for?
A
used to shock the heart to depolarise all cells and resent synchronous activity
18
Q
What is the fibrous skeleton of the heart made of?
What are its functions?
A
dense connective tissue
- structural support (solid base for attachment of the heart valves)
- electrical insulation (separates the atria from the ventricles so impulse must pass through the AV node/ Bundle of His - stops atria and ventricles from contracting simultaneously)
- attachment for myocardium
- maintains valve patency
19
Q
Where does the heart beat originate from?
Where are these found?
A
pacemaker cells
SA node
20
Q
What is the definition of myogenic rhythm?
A
heart’s ability to generate rhythmic contractions from within the cardiac muscle itself, independent of external nervous input
21
Q
What is the SA node? Where is the SA node located?
What does it do?
A
small, specialised cluster of pacemaker cells - right atrium
sets the pace for the entire heart
22
Q
What is the role of the atrioventricular valves?
Where is the tricuspid valve located?
Where is the mitral valve located?
A
ensure blood flows in only one direction
between right atrium and right ventricle
between left atrium and left ventricle
23
Q
What prevents valve cusps blowing into the atrium during contraction?
A
papillary muscles
24
Q
What can papillary muscle damage lead to?
A
valve incompetence and an audible murmur
25
What occurs in the following:
1. Atrial systole
2. Ventricular systole
3. Diastole
1. contraction of atria
2. contraction of the ventricles
3. relaxation of both atria and ventricles
26
What are the stages of the cardiac cycle?
27
What is an indirect measure of Central Venous Pressure and why?
JVP - no valves between internal jugular vein and right atrium so there is a continuous column of blood
28
What is the difference between systole and diastole?
systole: when the heart muscle contracts and pumps blood from the chambers into the arteries
diastole: when the heart muscle relaxes and the chambers fill with blood
29
1. What does 'End-Diastolic Point' mean? What is the volume (roughly)?
2. What does 'End-Systolic Point' mean? What is the volume (roughly)?
1. volume of blood in ventricle when it is fully/mostly relaxed at the end of diastole - about 120ml
2. volume of blood in ventricle when it is fully/mostly contracted at the end of systole - about 50ml
30
What is the stroke volume?
How do you calculate stroke volume?
volume of blood left ventricle ejects per heartbeat
31
What is Ejection Fraction and how do you calculate it?
32
What is a normal ejection fraction?
50-65%
33
What is an echocardiogram? What can it help us determine?
ultrasound of the heart - ejection fraction
(allows us to view structure, view blood flow, measures SV and EF)
34
What does each wave/letter represent?
a wave: contraction of right atrium
x descent: relaxation of RA causes a drop in pressure
c wave: tricuspid valve closing and RV contracts
x descent: end of RV contraction, RA begins filling with blood
v wave: RA fills up against closed tricuspid valve
y descent: tricuspid valve opens and blood from RA fills ventricles
35
What does the v wave represent?
What would large v waves indicate?
filling of RA against a closed tricuspid valve
tricuspid regurgitation
36
What factors affect Stroke Volume?
pre-load - "stretch"
- how much ventricle fills with blood before it contracts (how much ventricle is stretched before squeezing)
contractility - "power"
- strength of ventricular contraction
after-load - "squeeze"
- resistance (pressure) that must be overcome for ventricle to eject blood
37
How do you calculate cardiac output?
HR X SV
e.g in HR 70bpm and SV 70ml =
70 x 70 = 4900ml/min = 4.9L/min
38
What is the total blood volume?
around 5L
39
What happens to cardiac output in pregnancy?
increases by 30-50%
40
What is the definition of Stroke Volume?
amount of blood ejected by one ventricle during a single heart beat
41
Fill in the gaps:
Vasoconstriction leads to an __1__ afterload which leads to a __2__ TPR.
Vasodilation leads to a __3__ afterload which leads to a __4__ TPR.
1. increased
2. high
3. decreased
4. low
42
1. What would happen if TPR rises?
2. What would happen if TPR falls?
1. venous pressure = falls
arterial pressure = rise
2. venous pressure = rise
arterial pressure = falls
43
What does this graph indicate?
shows the relationship between venous pressure and ventricular volume known as - ventricular compliance curve
the higher the venous pressure -> the more the heart will fill during diastole
44
What is Starling's Law?
SV increases in response to an increase in the volume of blood in the ventricles
45
What does the graph show?
What does the slope represent?
Starling's Curve - the more the ventricle is filled (end-diastolic volume/pre-load), the stronger the contraction (stroke volume rises)
contractility of the ventricle
46
What does the purple slope indicate?
- with increased contractility, the heart can pump out more blood (higher stroke volume) because heart muscle is squeezing more strongly
- lower afterload also causes higher stroke volume because there is less resistance (ventricles can eject blood more easily)
47
What does the pink slope indicate?
- with decreased contractility (inotropy), there is a lower stroke volume because heart muscle is not squeezing very strongly
- high after load also causes lower stroke volume due to more resistance
48
What are the divisions of the Nervous System?
What are the main two?
CNS: includes brain and spinal cord
PNS: all nerves outside CNS
somatic: voluntary control
autonomic: involuntary
49
1. What does the ANS do?
2. What type of motor pathway does the somatic nervous system use?
3. What type of motor pathway does the autonomic nervous system use?
1. regulates essential non-voluntary, visceral functions, SANS and PANS essentially act in opposition to each other constantly working to maintain homeostasis - balance of their activity gives autonomic tone
2. single motor neuron from spinal cord to skeletal muscle
3. two-neuron chain: preganglionic neuron (CNS -> ganglion) and postganglionic neuron (ganglion -> effector)
50
What are the 3 divisions of the autonomic nervous system?
- sympathetic (fight or flight)
- parasympathetic (rest and digest)
- enteric (GI tract control)
51
How many neurons are involved in an autonomic motor pathway?
2:
preganglionic neuron (CNS → ganglion) and a postganglionic neuron (ganglion → effector)
52
1. Where are sympathetic preganglionic neurons located?
2. Where are parasympathetic preganglionic neurons located?
1. in the thoracolumbar spinal cord (T1-L2/3) = thoraco-lumbar outflow
2. in the brain stem and sacral spinal cord (S2-S4) = cranio-sacral outflow
53
What is unique about the adrenal medulla in the sympathetic system?
it is innervated directly by preganglionic fibers which synapse onto chromaffin cells, these act like postganglionic neurons and release hormones into the blood
(whereas most sympathetic pathways use postganglionic neurons to innervate target organs:
- Preganglionic neuron (cell body in the spinal cord) → axon (preganglionic fiber)
- Synapses in sympathetic ganglion onto a postganglionic neuron
- Postganglionic neuron → target organ)
54
Which neurotransmitter is released by all preganglionic neurons in the ANS?
acetylcholine (ACh), acting on nicotinic receptors on postganglionic neurons in the ganglion
55
Which neurotransmitter is usually released by sympathetic postganglionic neurons? What does it act on?
norepinephrine / NA - acts on b-adrenoreceptors
56
Which neurotransmitter is released by parasympathetic postganglion neurons? What does it act on?
ACh - acts on muscarinic receptors on the effector cell
57
Where do the preganglionic neurons of the sympathetic nervous system originate from?
What does "thoracolumbar outflow" mean?
in the intermediolateral cell column of the thoracic and lumbar spinal cord (T1-L2/L3)
means that the sympathetic signals exit the spinal cord from the thoracic and lumbar regions
58
What is the main difference in spinal origin between sympathetic and parasympathetic systems?
sympathetic = thoracolumbar
parasympathetic = craniosacral
59
Axons leave the spinal cord via what?
ventral root
60
How many synapses are there in SANS and PANS?
2:
- pre-ganglionic to post-ganglionic
- post-ganglionic to effector organ
61
1. What is the effect of sympathetic activation of the heart and blood vessels?
2. What is the effect of parasympathetic activation of the heart and blood vessels?
1.
- heart: increased HR and force of contraction
- blood vessels: mainly vasoconstriction but vasodilation in smooth muscles
2.
- heart: decreased HR
- blood vessels: no effect except for vasodilation of certain exocrine glands and external genitalia
62
Label the image of this neuron in the Parasympathetic Nervous System.
Explain what is happening.
(Parasympathetic (Craniosacral)
1. Preganglionic neuron → releases ACh → acts on nicotinic receptors on postganglionic neuron.
2. Postganglionic neuron → releases ACh → acts on muscarinic receptors on target organs.)
- Triggers: decreased HR, increased Gi motility and secretion, increased salivation, lacrimination and urination, bronchoconstriction = overall rest and digest response
63
Label the image of this neuron in the Sympathetic Nervous System.
Explain what is happening.
Sympathetic (Thoracolumbar)
1. Preganglionic neuron → releases acetylcholine (ACh) → acts on nicotinic receptors on the postganglionic neuron.
2. Postganglionic neuron usually → releases norepinephrine (NE) → acts on adrenergic receptors (α or β) on target organs.
* Exception: sweat glands, which get ACh from sympathetic postganglionic neurons.
64
1. Where does choline come from?
2. What two molecules are combined to make ACh?
3. Which enzymes catalyses the synthesis of ACh?
4. Where is ACh stored?
5. How is ACh released into the synapse?
6. What breaks down ACh to stop its action?
1. from the diet
2. choline + acetyl-CoA
3. choline acetyltransferase
4. in the neuron in the synaptic vesicle
5. via Ca2+ mediated exocytosis when the neuron fires
6. synaptic acetylcholinesterase
65
What are the two main types of cholinergic receptors?
nicotinic (fast, usually on postganglionic neurons or muscles)
muscarinic (slower, usually on target organs)
66
What is a cholinergic receptor?
receptor which uses acetylcholine as its neurotransmitter
(cholinergic neuron releases ACh, cholinergic receptor responds to ACh)
67
1. What is a muscarinic receptor?
2. Where is it found?
3. What is it innervated by?
4. What does it mediate?
1. type of cholinergic receptor that responds to ACh, it is a G-protein couple receptor
2. target organs
3. parasympathetic postganglionic neeurons
4. effects of PANS -e.g slowing HR
68
How many types of muscarinic receptors are there? Which one is found in the heart and what does it do?
5 - M2 found in heart, slow the HR down to normal sinus rhythm by slowing down the speed of depolarisation
69
What are the 3 types of nicotinic receptors?
1. Muscular (skeletal muscle) - found at NMJ of skeletal muscles, cause excitation of muscle fibres which leads to contraction
2. Ganglionic (SANS and PANS) - found on postganglionic neurons in both sympathetic (SANS) and parasympathetic (PANS) ganglia - function is to transmit signal from preganglionic neurons to postganglionic neurone
3. CNS - found in brain and spinal cord
70
In regards to adrenergic and muscarinic receptors, answer the following:
1. What is their respective neurotransmitter?
2. What nervous system do each belong to?
3. What type of receptor are they?
4. Where are they located?
5. What is their function?
adrenergic
1. norepinephrine / NA
2. SANS
3. G-protein couple receptors
4. target organs
5. fight or flight response: increased HR, vasoconstriction, bronchodilation
muscarinic
1. Ach
3. PANS
3. G-protein couple receptors
4. target organs
5. rest and digest response: decreased HR, increased digestion and gland secretion
71
Explain how parasympathetic stimulation slows the heart, detailing the neurons, receptors, G-proteins, and downstream effect on cAMP.
1. Ach release
- parasympathetic preganglionic neuron releases ACh onto the postganglionic neuron - NICOTINIC RECEPTOR
- postganglionic neuron then releases Ach onto heart - MUSCARINIC RECEPTOR
2. Ach binds to muscarinic / M2
- receptors (GPCRs) on the heart (located in SA node and AV node)
3. G-protein activation
- M2 receptor -> activates G-protein in heart cell
4. Effector enzyme inhibited
- adenylate cyclase, enzyme that normally makes cAMP, is inhibited
5. cAMP levels drop
- less cAMP = less activation of protein kinase A (PKA)
- PKA normally phosphorylates ion channels to speed up depolarisation
6. HEART RESPONSE
- lower cAMP = SA node depolarises more slowly = HR decreases
72
Explain how sympathetic stimulation slows the heart, detailing the neurons, receptors, G-proteins, and downstream effect on cAMP.
1. Ach released
- from preganglionic sympathetic neuron originates in the thoraco-lumbar spinal cord (T1–L2) onto postganglionic neuron - NICOTINIC RECEPTOR
2. NA/NE released on heart (on b1 adrenergic receptors)
- from postganglionic sympathetic neuron
3. NE binds to b1 adrenergic receptors (GPCRs) on pacemaker cells in the SA and AV node and ventricular myocardium
4. b1 receptor activates G-protein
5. effector enzyme activation
- stimulatory G-protein activates adenylate cyclase = converts ATP -> cAMP
6. cAMP levels rise = activates PKA -> PKA phosphorylates ion channels, speeds up depolarisation and increasing contractility
7. HEART RESPONSE
- SA node depolarises faster -> HR increases (+ve chronotropy)
- stronger contractions (+ve inotropy)
73
Briefly summarise the effect of parasympathetic and sympathetic stimulation on the heart.
parasympathetic = M2 → Gi → ↓ cAMP → slow HR
sympathetic = β1 → Gs → ↑ cAMP → fast HR
74
What 3 things does the ANS regulate?
- HR
- force of contraction
- peripheral resistance of blood vessels
75
What 3 things are in the Central Control in the Medulla? What is involved in each?
1. cardioaccelerator centre (SANS)
- increases HR (+ve chronotropy) and SV (+ve inotropy)
- NA/NE acting on b1 receptors → ↑ cAMP → faster, stronger heartbeat
2. cardioinhibitor centre (PANS)
- decreases HR and reduces SV
- via vagus nerve (CN X) → ACh acting on M2 receptors → Gi → ↓ cAMP → slower heart rate
3. Vasomotor centre
- mainly sympathetic control over blood vessels
- regulates BP by adjusting vasoconstriction or vasodilation
- sends sympathetic signals to smooth muscle in arteries and arterioles → α1 receptors → vasoconstriction → increased BP
76
When a person's HR increases from 60bpm to 120bpm, which part of the cardiac cycle shortens the most?
diastole
77
A patient's ECG shows the P wave immediately before the QRS complex. This corresponds to which phase of the cardiac cycle?
atrial systole
P wave: atrial depolarisation
QRS complex: ventricular depolarisation
if P wave is immediately before QRS, it means that the atria are contraction (atrial systole) just before the ventricles depolarise and contract
78
1. The first heart sound (S1) is caused by the closure of which valves?
2. The second heart sound (S2) is caused by the closure of which valves?
1. AV valves: mitral and tricuspid
2. semilunar valves: aortic and pulmonary
79
What does Isovolumetric contraction mean?
During isovolumetric contraction, which of the following is true?
1. All valves are open
2. AV and semilunar valves are closed
3. AV and semilunar valves are open
4. Blood is flowing into the aorta
5. Ventricular volume is increasing
isovolumetric contraction: ventricles contract but volume doesn’t change yet because blood has nowhere to go
AV and semilunar valves are closed
80
What immediately follows closure of the aortic valve?
isovolumetric relaxation
81
In the Wiggers diagram, when does ventricular pressure first excess atrial pressure?
start of ventricular systole
82
A soft "lub-dub" sound is heard in a healthy young adult. What does the "dub" correspond to?
closing of semilunar valves
83
Which phase of the cardiac cycle has no change in ventricular volume but rapidly increasing ventricular pressure?
isovolumetric contraction
84
In AF, which part of the cardiac cycle is lost?
atrial systole
- the atria don’t contract in a coordinated way — they just quiver
- in AF, ventricular filling relies almost entirely on passive filling during diastole
85
Which pressure change causes the mitral valve to close?
ventricular pressure exceeding atrial pressure
86
In the Starling Curve, increase preload leads to what?
increased SV
87
Which phase occurs between S2 and S1?
diastole
88
A newborn is diagnosed with a large ventricular septal defect. Where is this defect most commonly located?
membranous part of the interventricular septum
89
In a patient with an ASD, which change in heart sound is most likely?
fixed splitting of S2
90
A 3-year-old presents with cyanosis that worsens during play but improves when squatting. Which congenital defect is most likely?
tetralogy of fallot
Med Term 3
flashcards
Decks in class (44)
# Cards
-
HPD 154
-
HPD 272
-
HPD 343
-
HDP 4 and 5101
-
HPD 6 and 7100
-
HDP 8 and 970
-
HSD 10 and 1184
-
HSD 11.265
-
Urinary System 1140
-
Urinary 2112
-
Urinary 368
-
Urinary 463
-
Urinary 551
-
Urinary 697
-
Urinary 789
-
Urinary 8137
-
Urinary 963
-
Urinary 1066
-
CVS 1129
-
CVS 294
-
CVS 390
-
CVS 465
-
CVS 589
-
CVS 6141
-
CVS 7112
-
CVS 8106
-
CVS 986
-
CVS 1063
-
CVS 1181
-
Respiratory 1132
-
Respiratory 2135
-
Respiratory 3115
-
Respiratory 480
-
Respiratory 5156
-
Respiratory 672
-
Respiratory 771
-
Respiratory 876
-
Respiratory 9112
-
Respiratory 10103
-
Respiratory 11117
-
OSCE practise15
-
ECGs117
-
PASSMED10
-
TERM 3 REVISION737
