Physiology Flashcards
(101 cards)
1
Q
What hormones control the extracellular fluid?
A
RAAS, ANP, ADH
2
Q
What is ECF Volume?
A
Interstitial fluid + plasma volume
3
Q
Describe the RAAS pathway
A
Renin–Angiotensin 1- Angiotensin 11-Aldersterone
4
Q
What does RAAS do to the arteries?
A
vasoconstriction
5
Q
What does RAAS do to Blood pressure and plasma volume?
A
Increases them
6
Q
What does ANP do to the arteries?
A
vasodilation
7
Q
What does ANP do to blood pressure and renin production
A
Decreases them
8
Q
What does ADH do to blood vessels?
A
Vasoconstriction
9
Q
What regulates ADH?
A
Hypothalamus
10
Q
What does ADH do to blood vessels, TPR and BP
A
Vasoconstriction and increases TPR and blood pressure
11
Q
How is MAP regulated in the short term?
A
Baroreceptor complex
12
Q
How is MAP regulated in the long term?
A
Blood volume by hormones, RAAS
13
Q
What are the major resistance blood vessels?
A
Arterioles
14
Q
When adrenaline acts on alpha receptors, what happens?
A
Vasoconstriction
15
Q
When adrenaline acts on beta receptors what happens?
A
Vasodilatation
16
Q
What are the chemical metabolites which stimulate vasodilatation to occur?
A
decreased Po2, PCO2, increased [H]
17
Q
What is the main intrinsic dilator?
A
NO
18
Q
What is the main intrinsic vasoconstrictor?
A
Endothelin
19
Q
What are the intrinsic physical factors?
A
temperature, myogenic response to stretch (MAP), sheer stress
20
Q
Where is NO synthesised?
A
Endothelium
21
Q
What controls venous return?
A
increased: blood volume, atrial pressure, EDV, SV, respiratory pumps, skeletal muscle action
22
Q
What is vasomotor control controlled by?
A
increased: venous return, TPR and MAP, venous return
23
Q
What happens during acute exercise?
A
Hyperanaemia overrides
24
Q
Describe the course of the pacemaker potential
A
There is a slow Na influx and a and a K efflux until threshold is reached. Ca channels then open during the rising phase (depolarisation) and during falling phase depolarisation occurs.
25
What are the 2 gap junctions that allow cell to cell conduction to flow?
Intercalated discs and desmosomes
26
What is the resting membrane potential of a Ventricular muscle action potential cell?
-90mV
27
What is the new ventricular muscle membrane potential following fast Na influx?
+30mV
28
Describe the 4 phases of the ventricular muscle action potential
```
0= fast rising Na influx
1= cells start to repolarise due to K efflux
2= plateau phase
3= closure of Ca, K efflux
4= -90mV
```
29
What is the plateau phase?
It is unique to contractile cardiac muscle and is a Ca influx
30
What does sympathetic stimulation supply?
SAN, AVN and myocardium
31
What effect does the sympathetic stimulation on pacemaker potential slope and what is the name?
Slope increases, chronotrophic effect
32
Name an active inhibitor of Ach and what does it do?
Atropine speeds up HR
33
What effect does the parasympathetic stimulation effect have?
Negative chronotrophic
34
What is an ECG?
A record of depolarisation and hyper polarisation as it moves across the heart from skin cells
35
State what occurs at the PQRS wave
```
P= atrial depolarisation
QRS= ventricular depolarisation
T= ventricular depolarisation
PR= AVN delay
TP= diastole
```
36
Where are intracellular stores of Ca found?
Sarcoplasmic Reticulum
37
What is a sarcomere?
The smallest functional unit capable of carrying out function
38
What complex exposes the myosin binding site and is stimulated by Ca?
Tropomyosin
39
What is the Refractory period?
A period following an action potential in which it is not possible to produce another action potential
40
What does the Refractory Period do?
It protects the heart by preventing generation of tetanic conditions
41
How is stroke volume calculated?
EDV-ESV
42
What is SV?
The volume of blood ejected by each ventricle per heart beat
43
What are the 3 factors that affect SV?
1. Preload/venous return
2. Afterload/resistance
3. Contractility
44
What is the Frank Starling Law?
Increased Venous return= increased EDV= increased SV
45
What is the name of the effect where stimulation of sympathetic nerves and increased force of contraction takes place?
Positive Inotropic effect
46
What do parasympathetic nerves do to SV?
Nothing, they do not affect force of contraction
47
What is Cardiac Output?
The volume of blood pumped by each ventricle per minute
48
What is the CO relationship?
CO= SVxHR
49
What is a healthy CO
5L
50
What is the cardiac cycle?
A sequence of depolarisation and reploarisation
51
What is depolarisation and depolarisation in terms of systole and diastole?
```
Depolarisation= systole
Repolarisation= diastole
```
52
What are the events during the cardiac cycle?
1. Passive filling
2. Atrial contraction
3. Isometric Ventricular Contraction-- LUB
4. Ventricular Ejection (EDV of 70ml is left)
5. Isovolumetric Ventricular Relaxation (cycle starts again)
53
Why does the atrial pressure not fall to zero during diastole?
Due to recoil of the arteries
54
How does blood flow in a normal artery?
In laminar fashion
55
What happens when cuff pressure>BP
the artery is occluded and no sound is heard
56
What happens when BP>cuff pressure?
This is called Turbulent flow and can be heard
57
What is the significance of the first and 5th Korotkoff sounds?
```
1st= systolic BP
5th= Disatolic
```
58
What is pressure gradient?
MAP- Central venous pressure
59
Define MAP
the average arterial BP during a single cardiac cycle
60
How do we calculate MAP (both ways)
[2xdiastolic BP] = systolic BP/3
OR
DBP+ 1/3 pulse pressure (difference between SBP & DBP)
61
What is the average MAP?
70-105mmHg
62
How is MAP calculated?
COx TPR
63
Describe the baroreceptor pathway
Pressure sensors--control centre--Effectors
| Baroreceptors--Medulla--HR,SV
64
What do stretch receptors do when BP increases in aortic arch and carotid sinus?
Stretch receptors increase firing through vagus and glossopharyngeal nerves
65
What is the significance of the baroreceptor in postural hypotension?
suddenly stand up--decreased: venous return, MAP, baroreceptor firing, vagal tone, increased: sympathetic, HR, SV, TPR
Failure of baroreceptor reflexes
66
What changes to baroreceptors respond to?
Acute changes
67
What is shock?
An abnormality of the circulatory system resulting in inadequate tissue perfusion and oxygenation
68
What is the primary cause of hypovolaemic shock and the subtypes?
Decreased preload
| haemorrhage and non haemorrhage
69
Primary cause of cariogenic shock and eg
Decreased cardiac contractility and acute MI
70
Primary cause of shock in tension pneumothorax and what type is it?
Rise in intrapleural pressure with pressure in atrium exceeding pressure in ventricle.
71
Name some obstructive types of shock
cardiac tamponade, tension pneumothorax, PE, severe aortic stenosis
72
What is the primary cause of neurogenic shock (e.g. spinal cord injury)?
loss of vasomotor control (sympathetic)
73
What is the primary cause of vasoactive distributive shock (e.g. septic shock or anaphylaxis)?
Release of vasoactive mediators (vasoconstrictors)
74
What stimulates the peripheral chemoreceptors to increase R.R?
Release of lactic acid
75
What should you look for in a patient who has gone into shock?
cold peripheries, inadequate capillary refill, tachycardia, decreased BP
76
How is shock managed?
ABCDE
High flow O2
Volume replacement
Inotropes for cardiogenic shock to increase contractility
Immediate chest drain for tension pneumothorax
adrenaline for anaphylaxis
vaspressor for septic shock
77
What is the CV response to hypovolaemic shock?
decreased: MABP, CO, BV
78
What is the range of shock classification?
```
class I- body can cop well without much physiological compensation
class IV- life threatening- no urine output, confused and lethargic
```
79
Where does the coronary circulation arise from
The base of the aorta
80
How can 02 be increased in the coronary circulation during demand?
By increasing coronary blood flow through intrinsic and extrinsic regulation
81
What special adaptations does the heart make to supply more 02 to the coronary circulation?
High capillary density and high basal blood flow
82
What are the intrinsic mechanisms which regulate coronary blood flow?
decreased 02--> vasodilation
Metabolic hyperaemia
Adenosine from ATP is a potent vasodilator
83
What are the extrinsic mechanisms which regulate coronary blood flow?
adrenaline acts on the beta2 receptors causing vasodilation
84
Describe the pathway of increasing coronary blood flow
sympathetic--> increased HR and SV--> increased Cardiac output--> incr Metabolism--> incr adenosine--> incr metabolites eh K,PCO2, H--> increased circulating adrenaline
85
When does the major of coronary blood flow take place?
During diastole
86
What happens if diastole is reduced?
decreased coronary blood flow, rapid incr in HR and tachycardia, chest pain
87
What 2 factors regulate the cerebral circulation and what is their combined name?
Internal carotid arteries, Basilar (vertebral bodies) = Circle of Willis
88
What happens when grey matter undergoes hypoxia?
Consciousness is lost after a few seconds of ischemia and the damage is irreversible therefore special adaptations take place
89
What are the two subtypes of stroke?
Ischaemia and hemorrhagic
90
What are the pressure values at which auto regulation kicks in when MAP changes in the cerebral circulation?
-60mmHg or 160mmHg
91
What happens when MAP value in the cerebral circulation falls below 50mmHg?
Auto regulation fails and the patient is confused, faints and suffers from brain damage
92
What happens when MAP is increased and decreased in the cerebral circulation?
MAP increased: constriction
| MAP decreased: dilation
93
What happens to cerebral MAP when PCO2 is increased and decreased?
PCO2 increased= vasodilation
| PCO2 decreased= vasoconstriction
94
What is normal intracranial pressure? (ICP)
8-13mmHg
95
What is the cerebral perfusion pressure? (CPP)
MAP-ICP
96
What happens when ICP is increased?
decr CPP, decr cerebral blood flow
97
What special adaption in the pulmonary circulation prevents oedema?
Absorptive forces. filtration
98
What happens to the arterioles in the pulmonary and systemic circulation when there is a decrease in 02?
Pulmonary: vasoconstriction
Systemic: vasodilation
99
Why does varicose veins not affect the cardiac output?
It is a chronic development and so the body can compensate and the blood volume will not fall
100
What happens during exercise that overcomes the sympathetic vasocontrictor activity?
Metabolic hyperaemia
101
What is retrograde conduction?
When the conduction comes from the ventricle or the AVN to the atria
