Week 1 Flashcards
1
Q
Describe the Fascia of the neck?
A
- Neck is composed of columns surrounded by fascia.
- Create potential spaces between muscles in different columns which allows movement without effecting underlying structures.
2
Q
What is Prevertebral Fascia?
A
- Neuro-musulo-skeletal
- A deep layer of deep cervical fascia surrounds vertebral column and associated muscles.
- Extends from base of skull to coccyx.
3
Q
What is Pretracheal fascia?
A
- Surrounds the visceral compartment of the neck
- Fascial membrane enclosing the esophagus, trachea and thyroid gland.
- Along with buccopharyngeal fascia is known as the visceral fascia
4
Q
What is Buccopharyngeal fascia?
A
- Posterior part of the pretracheal layer of the deep cervical fascia that separates the pharynx and esophagus.
- Allows sliding of the Pharynx when we swallow.
5
Q
What is the Carotid sheath?
A
- Fascial membrane enclosing the internal jugular vein, vagus nerve and common carotid artery.
- Carotid neurovascular bundle with carotid sheath on each side.
- Extends from base of skull to root of neck.
6
Q
What is investing fascia?
A
Most superficial layer of deep cervical fascia surrounding the entire neck
7
Q
What are the 3 Potential spaces?
A
- Exist between muscles on floor of the mouth.
- Retropharyngeal space between prevertebral and pretracheal surrounding anterior column.
- Pretracheal space from neck to superior mediastinum.
8
Q
What is the Retropharyngeal space?
A
- Potential space between the buccopharyngeal and prevertebra fascia.
- Potential for infections of face and neck, especially teeth (abcesses).
- Extends all the way up to base of skull and down to diaphragm.
- Passes behind left atrium in mediastinum, risk of infection to heart.
9
Q
What is the Pretracheal space?
A
- Between investing and pretracheal fascia
- This space is continuous with the anterior mediastinum of the thorax
10
Q
Sternocleidomastoid separates the neck into what 2 Neck triangles?
A
- anterior
2. posterior.
11
Q
Describe the Posterior triangle?
A
- The External jugular vein, Subclavian artery, and the brachial plexus are structures within this triangle.
- Borders: sternomastoid muscle (clavicular head), trapezius, clavicle
- Winds around the neck as it ascends from clavicle to lie behind the mastoid process.
- Landmark deep within is the scalenus anterior
12
Q
Describe the Anterior Triangle?
A
- Lies in front, between the sternocleidomastoid and the midline of the body
- Its base up along lower border of the mandible and its apex down at the suprasternal notch
13
Q
What is the Position of transverse process of atlas?
A
- Half way between mandible angle and the mastoid.
- This space also filled with parotid gland
14
Q
What is the Hyoid bone?
A
The bone located in the neck between the mandible and the larynx, which supports the tongue and provides attachment for some of its muscles
15
Q
What does the Sternocleidomastoid do?
A
Rotates head to opposite side and tilts ear to same shoulder
16
Q
What does the Trapezius do?
A
Shrugs shoulders and extends neck
17
Q
What are the 3 Major arteries passing from thorax?
A
- Right and left common carotid
- Brachiocephalic trunk
- Aortic arch
18
Q
List the different head and neck veins?
A
- Internal jugular vein
- External jugular vein
- Occipital vein
- Retromandibular vein
- Posterior external jugular vein
19
Q
Common carotid
A
- Landmark at lower end is sternoclavicular joint, line goes to transverse process of Atlas midway between mandible and mastoid.
- Common bifurcates at C3/4 or upper edge of thyroid cartilage.
20
Q
How to Palpate the Pulse of Carotid?
A
- Line of common carotid
- At or deep to anterior border of sternocleidomastoid, just above thyroid cartilage and below hyloid bone - picking up the common carotid bifurcation and the origins of both the internal and external carotids.
21
Q
What are the Additional pulses of the head and neck?
A
Branches of the external carotid
- Superficial temporal, anterior to the ear
- Facial, crossing the mandible
22
Q
What is the Jugular Venous Pulse Wave?
A
Increased atrial pressure due to filling against closed tricuspid valve
23
Q
Describe the Internal jugular vein?
A
- Sternoclavicular joint to TP atlas. Exits the skull from the jugular foramen, it lies posterior to the internal carotid artery.
- Lateral to the artery for most of its course.
- But is anterior to the artery at its termination.
- Lies close to brachial plexus, phrenic nerves and vagus.
- Can be accessed lateral to carotid artery but risky due to important structures nearby.
24
Q
Describe the External Jugular vein?
A
- Just below and behind angle of mandible to mid clavicle.
- Verticle, superificial to sternocleidomastoid.
- May be used for venous access, particularly in babies.
- Pierces investing fasica and may be held open by it meaning theres a risk of air emboli.
- Joins the subclavian vein
- Carries blood returning to heart from head & neck
25
What are the Nerves of the neck?
- Branches of the cervical plexus emerge posterior to sternocleidomastoid and pass adjacent to the external jugular
- Accessory nerve passes across the posterior triangle to supply trapezius and sternocleidomastoid
26
What are the Lymph nodes of the neck?
- Accompany external and internal jugular veins.
- Drain the scalp, forehead, face, cheeks etc.
- Superficial nodes drain to deep cervical nodes aligned with external jugular vein.
27
What does an Opthalmoscope do?
- Study the retinal blood vessels.
| - Very important in CVS examination.
28
What is another name for the coronary sulcus?
Atrioventricular groove
29
What are the only branches of the ascending aorta?
Coronary arteries
30
What is another name for the main stem artery?
Left coronary artery
31
What structures does the right coronary artery pass between?
Right auricle and pulmonary trunk
32
What branches does the right coronary artery give off?
1. Marginal branch
2. Posterior inter ventricular
3. Nodal branch (suppling SA node)
33
What does the right coronary artery usually supply?
- Walls of right atrium and right ventricle
- Sinuatrial and atrioventricular nodes
- Posterior interventricular septum
- Proximal bundle of His
- Small areas of left atrium and left ventricle
34
Which coronary artery is usually dominant?
Right coronary artery
35
What is an obstruction of the right coronary artery usually referred to as?
Inferior infarct- likely to case arrythmias
36
What structures does the left coronary artey pass between?
Arises between left auricle and Pulmonary trunk
37
What branches does left coronary artery give off?
1. Circumflex branch, which divides to give the left marginal branch
2. Anterior interventricular branch / LAD (left anterior descending)
38
What does the left coronary artery supply
- Walls of the left atrium and left ventricle.
- Most of the inter ventricular septum
- Lower part of atrioventricular bundle.
39
Which artery is most commmonly affected by atherosclerosis?
LAD (artery of sudden death)
40
What vessel does an anterior infarct refer to?
Left anterior descending (LAD)
41
What vessel does a lateral infarct refer to?
Circumflex lateral
42
What does "CABG" stand for?
Coronary artery bypass grafting
43
What vessels are usually used in a coronary artery bypass?
- left internal thoracic
- internal mammary artery
- great saphenous veins
44
What does "PTCA" stand for?
Percutaneous transluminal coronary angioplasty
45
Name the four cardiac veins going from right to left
Small cardiac vein --> anterior cardiac vein --> middle cardiac vein --> great cardiac vein
46
Which vein becomes the coronary sinus?
Great cardiac vein
47
What is the name of the veins draining directly into the chambers?
Venae cordis minimi
48
Where is the coronary sinus situated?
Between the left atrium and left ventricle, which empties into the right atrium
49
Where does the cardiac plexus lie?
- Inferior to the arch of the aorta, adjascent to the bifurcation of the trachea.
- Sends both afferent and efferent branches to the sinoatrial node, cardiac muscle and coronary arteries.
50
Which autonomic NS contribute to cardiac plexus?
Both sympathetic and parasympathetic
51
What type of tissue covers the endothelium of foetal capillaries in the placenta?
Syncytiotrophoblast
52
Which vessel brings oxygenated blood from the placenta?
Umbilical vein
53
Which vessels bring deoxygenated blood from the foetus?
2 Umbilical arteries
54
Which Vessels do the umbilical arteries branch from?
Internal iliac
55
What allows bypass of blood from right atrium to left? What circulation is being skipped?
Foramen ovale, pulmonary (SVC>RA>(FO)>LA)
56
Why in prenatal circulation is left atrial pressure very low?
Low pulmonary venous return, thus blood pulled in through foramen ovale
57
What vessel allows blood from the right ventricle to pass to the aorta? What circulation does this allow the blood to skip?
Ductus arteriosus, pulmonary (SVC>RA>RV>PY>Aorta)
58
How much blood bypasses the pulmonary circulation via ductus arteriosus?
90%
59
Where in the aorta does the ductus arteriosus join?
After the 3 branches to head/limbs
60
What is the purpose of the 10% of blood passing from the pulmonary trunk and entering the lungs?
(rather than passing through the ductus arteriosus)
Supplies developing foetal lungs
61
What compound is responsible for the patency of the ductus arteriosus?
Prostaglandins
62
Which vessel allows foetal blood to bypass the liver?
Ductus venosus
63
How much blood bypasses the liver?
50%
64
Where does the ductus venosus insert?
Inferior vena cava
65
Which blood is the most highly oxygenated?
Blood in IVC, so passes through foramen ovale to left ventrical and systemic circulation
66
What causes the foramen ovale to close?
First breath pulls blood into lungs, venous return to LA increases intratrial pressure, which equalizes with right atria and causes the foramen ovale to close
67
How is the ductus arteriosus obliterated?
- Initial smooth muscle constriction, 02 tension increases, 02 potent constrictor of DA.
- Placenta stops producing prostaglandins, which are removed from circulation by the functioning lungs.
- Later anatomical closure through thickening of tunica intima
68
What is the postnatal remenant of the ductus arteriosus?
Ligamentum arteriosum
69
What happens in patent ductus arteriosus?
Aortic pressure is greater than in the pulmonary trunk, so blood will flow back into the pulmonary trunk causing pulmonary hypertension and congestive cardiac failure.
70
How is the ductus venosus obliterated?
- Umbilical vessels contract with the delivery of the placenta, postnatal hepatic circulation is established and the ductus venosum becomes the ligamentum venosum.
- The umbilical vein becomes ligamentum teres
71
What is the name for the formation of a trilaminar disk?
Gastrulation
72
What are the three layers of the trilaminar disc?
1. ectoderm
2. mesoderm
3. endoderm
73
Which embryonic tissue does the heart tube form from?
- Mesoderm
| - Forming angiogenetic clusters
74
Where does the heart tube form?
In a horse shoe shape at the cephalic end of the trilaminar disk
75
When does cephalo-caudal folding start?
18th day (end of 3rd week)
76
What development of the heart tube results from the folding?
Lateral folding swings the two limbs of the horseshoe medially, so they fuse as a single heart tube
77
When does looping and folding occur?
22 days (early week 4)
78
Which way do the two ends of the heart tube fold towards?
- To the right, so pushing the apex to the left.
| - Rotating slightly so that the right side of the heart tends to be more anterior
79
What are the two main causes of heart defects?
1. Genetic causes
| 2. Teratogenic causes
80
Why are craniofacial abnormalities linked to heart defects?
Also use neural crest cells for development
81
Why can early embryonic development be sustained without a heart?
Diffusion is sufficient due to surface area:volume ratio
82
What additional embryonic tissue is formed in week three during gastrulation?
Mesoderm- will go on to form heart tissue
83
What is Dextrocardia?
Cardiac folds to the left, resulting in the heart being pushed to the right
84
What developments occur at 28 days?
Developing heart pushes into the pericardial sac, ventricles begin to trabeculate
85
What does the bulbus cordia form?
Mid portion forms the conus cordia which will form the conus portion which will from outflow tracts. The proximal part will form the right ventricle, the distal part will from the trunks of the great vessels
86
What vessels does the venous end of the heart tube receive?
Cardinal, umbilical and vitelline veins.
87
Where are the veins flowing into the heart tube in relation to the arteries running out?
Posterior- opposite to postnatal heart
88
What cells are endocardial cushions derived from?
Neural crest cells
89
What structures in the heart are derived from the endocardial cushion cells?
Interatrial septum, the membranous part of the interventricular septum, the atrioventricular valves, the formation of the aorta and pulmonary trunk from the truncus arteriosus
90
Which chambers are divided first?
Left and right side of the heart separate into 2 atrioventricular canals (left=mitral, right =tricuspid)
91
What is the first septum to form between the atria?
The septum primum growing in the interatrial ostium primum, this grows towards the developing endocardial cushion which has just separated the two atrioventricular canals
92
What is the 2nd septum to form between the atria?
Septum secundum grows, as tiny holes develop in the developing septum primum, which allow blood flow, the holes are called the ostium secundum. A hole forms in the developed septum secundum called the foramen ovale
93
When does atrial septation occur?
Weeks 5 & 6
94
When is the formation of the interventricular septum complete?
By the end of week 7
95
What are the 4 components of the ventricular septum?
Endocardial cushions form left and right endocardial ridges,
extension of inf. endocardial cushion produced the membranous part of the interventricular septum,
Proliferation of ventricular muscle forms the muscular part of the septum,
left and right truncal ridges from the conotruncal spetum
96
What is Fallots tetralogy?
Truncal septum deviates to the right and does not meet the interventricular septum
97
How are the mitral and tricuspid valves formed?
Endocardial cushion growth and cavitation to form papillary muscles and chordae tendinae
98
Which dorsal arch forms the maxillary arteries?
1st arch (left and right)
99
Which dorsal artery forms the common carotid arteries?
3rd arch (with dorsal aorta)
100
Which dorsal arch from the arch of the aorta?
Left 4th arch
101
Which dorsal arch forms the right subclavian?
Right 4th arch
102
Which dorsal arch forms the pulmonary trunk?
Left 6th arch (right 6th also contributed)
103
What is Coarctation of the aorta?
Narrowing after the origin of the left subclavian dues to abnormality in the aortic media and intima proliferation
104
What happens as result of coarctation of the aorta?
Blood travels in subclavian to the internal thoracic arteries, to intercostal vessels and back to the thoracic aorta (FEMORAL PULSES WILL BE WEAK)
105
What nerve do recurrent laryngeal nerves originate from?
Vagus nerve
106
Where and why does recurrent laryngeal nerve sit on the left?
6th arch, so hooks under aorta and is held by ductus arteriosus
107
Where and why does the recurrent laryngeal nerve sit on the right?
5th and 6th arches regress on the right, so hooks under 4th arch- the right subclavian artery
108
Functional Syncitium
- Cells of atrial myocardium are all electrically connected
- Depolarise and contract synchronously
- Ventricles are similar but are a separate functional unit
109
Cardiac skeleton
- Connective tissue between atria and ventricles, prevent flow of electrical current between the two.
- Atria and ventricles electrically separate except at AV node
110
Conduction Network
1% of cardiac fibres dont contract, but form the excitatory and conductive muscle fibres
111
Pacemaker activity
- SAN is the intrinsic pacemaker
| - Other areas have pacemaker ability
112
Autonomic innervation
- Sympathetic nerves INCREASE the rate of SAN depolarisation
| - Parasympathetic nerves DECREASE the rate of SAN depolarisation
113
What is the Plateau phase?
- 2nd phase
- Balance of K+ ions flowing out of the cell against the influx of Ca2+ flowing in.
- When the intracellular calcium concentration reaches a certain level, more K+ channels open and the L-type Ca2+ channels close to cause phase 3.
- Prevents tetany from occuring.
114
Describe the phases in Atrial/ventricular depolarisation?
PHASE 0 -Rapid depolarisation due to increase in Na permeability as fast Na channels open up
PHASE 1 -Once reach 20mV Na channels close causing drop in Na permeability. Start of repolarisation
PHASE 2 -Effect of Ca entry via L-type channels. Keeps cell in depolarised state - plateau region.
PHASE 3 -Rapid repolarisation as increase in Ca stimualtes K channels to open and K permeability to increase. Ca L-type channels close
PHASE 4 -Stable resting membrane potential where gK exceeds gNa by 50:1
115
Describe the phases in SA node depolarisation?
PHASE 1 - Gradual increase in resting potential due to 'funny' F-type Na channels open and K channels slowly close. Transient (T) Ca channels help with the final push
PHASE 2 - Moderately rapid depolarisation due to Ca entry via slow L channels.
PHASE 3 - Rapid repolarisation as elevated internal Ca stimulates opening of K channels. As potential becomes more negative F-type Na channels start to open, preventing return to resting potential and starting gradual creep towards threshold potential.
116
What is a Pacemaker potential?
- A self-induced slow depolarization to threshold occurring in a pacemaker cell as a result of shifts in passive ionic fluxes across the membrane accompanying automatic changes in channel permeability.
- Gradual creep caused by the F-type Na+ channels.
117
What are F-type ("funny" type) voltage-gated Na channels?
"Funny" because they open as the membrane voltage becomes more negative, which is different from normal voltage- gated Na+ channels which open when the membrane potential becomes more positive.
118
Describe the Autonomic nervous system?
- Sympathetic controls whole heart (myocardial tissue). Can act as accelerator of heart through muscle fibres themselves. Effect on speed and force of contraction
- Parasympathetic controls node tissue only. Only going to affect nodal tissue so can only affect speed of contraction.
119
Describe Sympathetic stimulation?
- Noradrenaline acts on B1 receptors to increase cAMP production
- This increases the rate of SAN phase 1 depolarsation by increasing gCa through slow channels and increasing gNa via funny channels
120
Describe Parasymapthetic stimulation?
- Acetylcholine on M2 receptors which decreases cAMP production
- Reduces rate of phase 1 depolarisation
- Hyperpolarises membrane potential to lower starting level by increasing the extent and duration of opening of the K channels and therefore increasing gK.
121
What is Positive chronotropic effect?
- Increased heart rate
| - Shown by sympathetic stimulation
122
What is Negative chronotropic effect?
- Slowed heartbeat
| - Shown by parasympathetic stimulation
123
Describe the SA node?
- Located in the top of the right atrium just below superior vena cava
- Starts the heart beat by sending an electrical impulse through the atria.
- Has the fastest rate of the heart elements so is the intrinsic pacemaker.
- Depolarisation spreads from SAN throughout the heart before other regions spontaneously depolarise.
- If conduction blocked, downstream tissues assume their intrinsic rate.
124
Describe the AV node?
- Located at the posterior septal wall at the right atrium just above the tricuspid valve
- Atrioventricular region of the heart between the right atrium and right ventricle from which electrical impulses spread to the ventricles during a heartbeat
125
What is "Bundle of His"?
A collection of heart muscle cells specialized for electrical conduction that transmits the electrical impulses from the AV node (located between the atria and the ventricles) to the point of the apex of the fascicular branches via the purkinje fibres
126
What is "Purkinje fibres"?
- Fastest path of conduction in heart
- Divisions of the Bundle of His that reach deep into the endocardium and produce a simultaneous contraction of the ventricles from the bottom up.
127
What are the 5 different Intrinsic rates of the heart?
```
SAN - 90/min
AV node - 60/min
Bundle of his - 50/min
Purkinje fibers - 40/min
Ventricles - 30/min
```
128
What is Einthoven's triangle?
- The placement of electrodes (in an ECG) on the body forms a triangle.
- Measure electrical activity between points on the triangle
Size of electircal signals from the heart is determined by:
-current (proportional to tissue mass)
-Direction of signal
129
What is the equation for the Actual electrical signal?
Observed signal = E x cosO
- Smallest angle gets biggest observed signal
- The more parallel you are to the activity the closer you are to signal
130
What does the Electrocardiogram (ECG) do?
Takes a recording of the electrical activity of the heart
131
What is the reason of the different waves in an Electrocardiogram graph?
P wave- atrial depolarisation
QRS wave- ventricular depolarisation
T wave- Ventricular repolarisation
132
What ion channel is responsible for propagating the AP in cardiac muscle?
Voltage gated sodium
133
What channels open as a result of the AP propogating down in the T Tubules?
L-type dihydropyridine calcium channels
134
Where does calcium move from through L type channels?
Outside the cell
135
What percent of the calcium moving through the L type calcium channels contributes to cardiac contraction?
10%
136
What is responsible for the high concentration of calcium in the T Tubules?
Mucopolysaccharides that sequester Ca2+
137
How many times greater is the cardiac T-tubule volume compared to skeletal?
25x more volume (5 times greater diameter)
138
What channels in the sarcoplasmic reticulum allow the calcium spark?
Ryanodine release channels (calcium induced calcium release)
139
Which pump affected by sympathetic Stimulation?
Calcium ATP pump on sarcoplasmic reticulum membrane= pumps more Ca++ into sarcoplasmic R. so more is ready to be released on the next stimulation. Thus more powerful contraction
140
What is Preload?
Venous pressure and venous return to the heart (end diastolic pressure)
(ALWAYS THE SAME, REGARDLESS OF CARDAIC OUTPUT)
141
What is cause of the refractory period?
Inactivation of voltage gated sodium channels
142
What is the cause of repolarisation?
Closure of L-type calcium channels, and sudden opening of potassium channels
143
Length of AP in Cardiac muscle?
245ms
144
What is the Period of contraction of cardiac muscle?
250ms
145
What is SNP?
- Supranormal period of excitability
| - Requires less than normal sized stimulus to activate
146
How much of ventricular filling is passive?
80%
147
how quickly is the first 70% ejected from ventricles
- RAPID
| - First 1/3
148
Isovolumic
No change in blood volume in chambers, valves closed
149
How do you calculate the Stroke volume (SV)?
end diastolic volume - end systolic volume
| EDV - ESV
150
What is the end systolic volume (ESV)?
Volume in ventricle at end of sytole
151
What is the End diastolic volume (EDV)?
Volume in ventricle at the end of diastolic
152
What is the range in stroke volume that the heart can achieve?
70-140ml
153
What is the range in heart rate the heart can achieve?
70-200bpm
154
What is the range in cardiac output that the heart can achieve?
5-30 (L/min)
155
What is Afterload?
Force exerted by pulmonary artery/aorta (needs to be overcome in order to expel blood from ventricles)
156
What is the main intrinsic mechanism regulating stroke volume?
Frank Starling mechanism
157
What is the main extrinsic mechanism regulating stroke volume?
Sympathetic innervation
158
Which mechanism allows for automatic adjustment for small imbalances between left and right ventricular stroke volume?
Frank Starling mechanism
159
Does the Frank Starling Mechanism work in addition to inotropic stimulation of heart?
YES
160
Cardiac output=
Stroke volume (SV) x heart rate (HR)
161
Arterioles have a ___ capacity
Low
162
Arterioles have a ____ resistance
High
163
Venous system has a ____ capacity
High
164
Venous system has a ___ resistance
Low
165
What is Compliance?
Degree to which a vessel can expand on the onset of pressure
166
High compliance
Small change in pressure results in large change in diameter
167
Compliance can be reduced by what 2 things?
1. Vasoconstriction
| 2. Age
168
What does "MABP" Stand for?
Mean arterial blood pressure
169
MABP=
Diastolic pressure + 1/3 pulse pressure
170
Poiseulle equation flow =
Flow= change in pressure/ resistance
171
Arterial pressure=
cardiac output x total peripheral resistance
172
What 3 Factors determining magnitude of pulse pressure?
1. Stroke volume
2. speed of ejection
3. arterial compliance
173
What shape does the velocity profile of blood take in a vessel during lamina flow?
Parabolic (due to friction between endothelial blood vessel cells and blood cells)
174
What happens in Reynold's number is exceeded?
Experience turbulence
175
Reynolds number (Re)=
(Velocity of flow) x (radius of vessel)/viscosity
176
name 4 factors increasing turbulence
1. High velocity flow
2. large diameter vessels
3. increased viscosity blood
4. abnormal vessel wall
177
Thixotropic
- Flow affects viscosity of fluid
| - static blood solidifies
178
What is LaPlace's law?
Distending pressure(P) produces an opposing force or tension (T) in the vessel wall, proportional to the radius of the vessel (R)
T= PR
179
How does Laplace's law affect aneurysms?
Weakening causes increase in radius of vessel, which in turn results in an increased tension in the vessel, which will further the vessel wall weakening and so further the distention
180
What are Metarterioles?
Links arterioles to venules, made of discontinuous smooth muscle, capillaries branch off.
181
What are Arterioles job?
Control regional distribution (local and extrinsic controls)
182
What are Precapillary sphincters?
Found where a true capillary branches from a metarteriole, vasodilate according to build up of local factors which results in increased blood flow to that capillary bed
183
What is the arteriole response to an increase in pressure in flow auto regulation?
Constriction to reduce flow
184
What is the arteriole response to a decrease in pressure in flow auto regulation?
Dilate to increase flow
185
What is the myogenic response in blood vessels to an increased pressure (part of autoregulation)
- Stretch activates Ca"+ channels open, resulting in a depolarization and contraction on the smooth muscle in arterioles.
- resulting in constriction
186
What potent vasoconstriction factor is released upon tissue injury?
Endothelin-1
187
What is Active hyperemia?
Rate of flow increasing due to active tissue (up to 20s increase in skeletal muscle)
188
What is Reactive hyperemia?
Blood supply blocked, resulting in build up of factors, resulting in a signal to increase blood flow (4-7x increase)
189
Which autonomic nervous system is responsible for vasoconstriction?
Sympathetic
190
Which 3 hormones bring about vasoconstriction?
1. adrenaline
2. Angiotensin II
3. vasopressin
191
Which 2 local responses bring about vasoconstriction?
1. Myogenic response
| 2. endothelin-1
192
Which 2 hormones bring about vasodilation?
1. Adrenaline (skeletal muscle)
| 2. Atrial-Natriuetic peptide
193
What controls the vasodilation of the sexual organs?
NO releasing parasympathetic nerves
194
Which local factors affect vasodilation?
Mainly Adenosine, also increased K+, CO2, H+, NO, Histamine, and decreased O2
195
At rest, what percent of cardiac output is in capillaries?
~5%
196
What changes are described as long term regulation of blood flow?
Change in size or number of blood vessels
197
Which vessels have slowest velocity blood?
Capillaries- allow time for diffusion
198
What are Viruses?
- Small infective agents consisting of nucelic acid (RNA or DNA) enclosed in a protein coat.
- Not cells as have no metabolic machinery of their own, are obligate intracellular parasites
199
What is an Obligate?
An organism that requires oxygen for cellular respiration and cannot live without it
200
What is a Capsid?
- The protein shell that encloses a viral genome.
| - It may be rod-shaped, polyhedral, or more complex in shape
201
What is SS RNA?
- Single stranded RNA viruses are classified as positive or negative depending on the sense or polarity of the RNA.
202
2 Examples of DS DNA?
- Herpes virus
| - Adenovirus
203
Example of SS DNA?
Parovirus
204
Example of +SS RNA?
HIV
205
2 Examples of -SS RNA?
- Arenavirus
| - Rhabdovir
206
Describe Virus Replication?
- In order to replicate they have to attach to and enter a living host cell and use its metabolic processes.
- The binding sites on the virus are polypeptides on the envelope or capsid
- The receptors on the host cells, to which the virus attaches, are normal membrane constituents
- With many viruses, the receptor virus complex enters the cell by receptor-mediated endocytosis during which the virus coat may be removed. Some bypass this route.
- Once in the host cell, the nucleic acid of the virus then uses the cells machinery for synthesising nucleic acid and protein and the manufacture of new virus particle
207
List the 8 different Types of antiviral drugs?
1. Entry inhibitor
2. Viral Uncoating
3. Nucleoside analogue chain termination
4. NNRTIs (non-nuceloside reverse transcriptase inhibitors)
5. Protease inhibitors
6. Integrase Inhibitors
7. Virus Release Inhibitors
8. Immunomodulator
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What is the Virus Life Cycle?
1. Recognition
2. Attachment
3. Penetration
4. Uncoating
5. Transcription
6. Protein synthesis
7. Replication
8. Assembly
9. Lysis and release
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Nucleoside analogues
- Inhibit replication of HIV virus by inhibiting the transcription of RNA and DNA.
- Inhibit synthesis of nucleic acids (binding to the viral DNA polymerase and preventing viral DNA replication)
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Protease inhibitors
Prevent viral replication by selectively binding to viral proteases and blocking proteolytic cleavage of protein precursors that are necessary for the production of infectious viral particles.
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DNA viruses
Eg. HSV, HPV
There is generally entry of the viral DNA into the host cell nucleus
Transcription of this viral DNA into mRNA by host cell RNA polymerase followed by translation of the mRNA into virus-specific proteins
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How do you treat Cytomegalovirus (CMV)?
- Acyclovir not as active
| - Treat with ganciclovir and valganciclovir
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RNA viruses
Eg. Influenza (flu), Hep C (HCV)
RNA viruses classified according to the sense or polarity of their RNA
Positive-sense viral RNA is similar to mRNA and can be immediately translated by the host cell
Negative-sense RNA is complementary to mRNA and must be converted to positive-sense by RNA polymerase before translation
RNA polymerase directs the synthesis of more viral genomic RNA
Typically virus replication occurs in the host cell cytoplasm not the nucleus
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Retroviruses
Eg. HIV, Human T cell Leukemia Virus (HTLV)
Virus contains reverse transcriptase an RNA-dependent DNA polymerase, which makes a DNA copy of the viral RNA.
This DNA copy is integrated into the genome of the host cell and it is then termed a provirus
The provirus DNA is transcribed into both new genomic RNA and mRNA for translation into viral proteins using host cell machinary.
Some RNA retroviruses can transform normal cells into malignant cells.
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HIV structure
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GP-120 is a grabber for the HIV. Grabs onto the Macrophages/t cells. Conformation happens and then its allowed to bind to a coreceptor- either CCR5 or CXCR4 = tropism- important for therapy. Dual tropism = HIV that can bind to either CCR5 or CXCR
Nucleic acid (RNA) surrounded by core proteins, which in turn are surrounded by a capsid (protein shell), which in turn is surrounded by a lipid bilayer envelope
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Approved Antiretroviral Drugs
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Reverse Transcriptase Inhibitors
Protease Inhibitors
Early Inhibitors
Fusion Inhibitors
Integrase Inhibitors
>25 different drugs, 6 different mechanistic classes
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Reverse transcriptase inhibitor
When HIV infects a cell, reverse transcriptase copies the viral single stranded RNA genome into a double-stranded viral DNA. The viral DNA is then integrated into the host chromosomal DNA, which then allows host cellular processes, such as transcription and translation, to reproduce the virus. RTIs block reverse transcriptase's enzymatic function and prevent completion of synthesis of the double-stranded viral DNA, thus preventing HIV from multiplying.
A similar process occurs with other types of viruses. The hepatitis B virus, for example, carries its genetic material in the form of DNA, and employs a RNA-dependent DNA polymerase to replicate.
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Nucleoside/nucelotide analogues
Compete with the natural substrate (dNTPs for DNA synthesis or NTPs for RNA synthesis) in DNA or RNA polymerization, therefore virus specific selectivity
Act as chain terminators by not offering the 3′-hydroxyl function at the (2′-deoxy)riboside moiety, which is required for attachment of the incoming nucleotide.
Or nucleotide analogues possessing an hydroxyl function at a position
equivalent to the 3′-hydroxyl position act as chain terminator if this hydroxyl group
is conformationally constrained and therefore hinders attachment of the incoming nucleotide.
They are prodrugs and require intracellular phosphorylation by viral and/or cellular kinases to convert them from the 5'-monophosphate form to 5'-triphosphates.
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Protease Inhibitors
Host mRNAs code directly for functional proteins
In HIV, mRNA is translated into biochemically inert proteins
A virus-specific protease then converts them into various functional proteins
Since the protease does not occur in the host, it is a good selective-toxicity target
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Integrase
HIV integrase mediates 2 critical reactions:
1. 3' end processing of the double stranded viral DNA ends
2. Strand transfer which joins the viral DNA to the host chromosomal DNA forming a functionally integrated provirus
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Integrase Inhibitors
For HIV resistant to other HAART regimanes
Medications that interrupt the viral replication cycle by inhibiting integrase enzymes that allow the transcribed viral DNA to integrate into the host cell DNA
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Fusion inhibitors
Entry of HIV into a new cell is mediated by the Env glycoprotein spike a trimer of pg120 and gp41. Entry requires the receptor CD4 plus on eof 2 receptors, CCR5 or CXCR4
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Neuraminidase
Functions in influenza infection by cleaving sialic acid from the cell surface so that newly made viruses are released and able to spread to uninfected cells
