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Physiology 1 > Heart (2) > Flashcards

Heart (2) Flashcards

1
Q

What type of action potential happens in Myocytes?

A

Fast-response AP

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2
Q

Phases of a Fast-response action potential

A

0) Upstroke
1) Partial repolarization
2) Plateau
3) Complete Repolarization
4) Em

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3
Q

Duration of a Fast response AP

A

200 ms

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4
Q

What type of action potential happens in Nodal cells?

A

Slow-response AP

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5
Q

Duration of a Slow-response AP

A

400 ms

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6
Q

Slow vs Fast-response AP

A
  • Slow does not have Phase 1&2, partial repol. & plateau
  • More negative Em in fast AP
  • Much greater slope&amplitude in fast
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7
Q

Automaticity

A

Spontaneous depolarization and generation of an AP
(SA, AV nodes)

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8
Q

(I)f

A
  • HCN4 (non-selective cation ch.)
  • Na+ in
  • Pre/pacemaker potential generation
    (<-50 hyperpol, cAMP)
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9
Q

(I)Ca T

A
  • T-type VDCC
  • Na+ & Ca2+ in
  • Initial depol.
    (Transient= temporary/short-lived)
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10
Q

(I)Ca L

A
  • L-type VDCC
  • Ca2+ in
  • Depolarization
  • ~ -30mV
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11
Q

(I)k

A
  • VG types (several)
  • K+ out
  • Repolarization
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12
Q

(I)k,ach

A
  • GIRK1 / GIRK4
  • K+ out
  • Hyperpolarization
    (Ach, Vagus n, m2-R)
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13
Q

Does HCN channel inactivate?

A

No

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14
Q

HCN channel Inhibitor

A

Ivabradine

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15
Q

T-type VDCC Inhibitor

A

Verapamil

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16
Q

Chronotropic effect

A

Effect on the Heart Rate

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17
Q

Dromotropic effect

A

Effect on the Speed of conduction

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18
Q

Role of Gβγ in M2-R

A

Activation of GIRK channels

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19
Q

Sympathetic heart regulation

A
  • NE on B1-AR
  • Gs, more cAMP
    Threshold is reached faster with (I)f, so faster AP rate
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20
Q

Parasympathetic heart regulation

A
  • Right Vagus: SA
  • Left Vagus: AV
  • Ach on M2-R
  • Gi, less cAMP
  • Gγβ, hyperpol.
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21
Q

Does the Vagus nerve innervate the ventricles in Humans?

A

No

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22
Q

Hormone effects on HR (Epi, and TH)

A
  • Epineph: similar to NE
  • Hyperthyroidism: Tachycardia
  • Hypothyroidism: Bradycardia
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23
Q

B1-R blocker

A

Propranolol
Blocks sympathetic effect

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24
Q

M2-R blocker

A

Atropine
Blocks parasymp. effect
Much stronger effect on parasymp. compared to B1-R blockers

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25
What happens if we use both B1-R and M2-R blockers?
Propranolol & Atropine Produce the intrinsic pacemaker frequency of the SA node = 100 bpm
26
SA Node Intrinsic pacemaker freq.
100 bpm
27
AV Node/Bundle of His Intrinsic pacemaker freq.
40-60 bmp
28
Purkinje fibers Intrinsic pacemaker freq.
20-40 bpm
29
Myocytes Intrinsic pacemaker freq.
None Under physiological conditions (may happen in path.)
30
What affects conduction velocity?
- Size of current: higher current = faster conduction - Resistance: Low R in gap junctions, thicker branches conduct faster
31
Why does AV node have slowest conduction?
Very thin fibers, slower cond. To delay ventricular contraction
32
Effective / Absolute refractory period
Unresponsive after activation due to inactivated ion channels
33
Relative refractory period
Additional stimulus produces another AP, but needs stronger stimulus
34
ECG Depolarization and Inflection
- Positive direction= Positive inflection - Negative direction= Negative inflection
35
ECG Repolarization and Inflection
- Positive direction= Negative inflection - Negative direction= Positive inflection
36
Segment vs Interval on ECG
- Segment: Between waves where line is isoelectric - Interval: Includes waves
37
PR (PQ) interval
- Conduction from atria to ventricles - 0.12 - 0.20 s
38
QRS interval
- Ventricular depol. - 0.06 - 0.1 s
39
QT interval
- Ventricular depol. and repol. - 0.36 s
40
Unipolar lead
Measures the electric impulse of a point relative to a reference point
41
Bipolar lead
Measures electrical difference between 2 electrodes (+ & -)
42
Augmented limb leads (Goldberger)
- Unipolar lead: active/exploring electrode & indifferent/reference electrode - In Eindhoven's Triangle
43
Angles of Leads on Hexaxial system
- I: 0° - II: 60° - III: 120°
44
3 bipolar leads in Eindhoven Triangle
- AVR: R.Arm -150° - AVL: L.Arm -30° - AVF: Left leg +90°
45
1st Heart Sound
- AV valve closure - Longer, louder, lower frequency
46
2nd Heart Sound
- AO valve closure - Shorter, weaker, higher pitch
47
Length of Cardiac cycle
0.8 s
48
Systole time vs electrical
- Time: Bw First and second heart sounds - Electrical: Beginning of Q wave till end of T wave
49
Diastole time vs electrical
- Time: After 2nd heart sound till right before 1st heart sound - Electrical: Isoelectric interval after T and right before P
50
Rules for construction of Cardiac cycle
- Liquid is incompressible - Pressure gradient determines flow - Valves open with blood flow - No back-flow through closed valves
51
Stroke Volume (SV)
Amount of blood transported to Aorta in Systole EDV - ESV 140 - 60 = 80ml
52
Ejection Fraction (EF)
Fraction of ventricular blood ejected SV / EDV 0.5 < EF < 0.75
53
EDV
140 ml
54
ESV
60 ml
55
Atrium pressure
4 - 8 mmHg
56
Ventricle pressure
4 - 120 mmHg
57
Aortic pressure
80 - 120 mmHg
58
Systole duration
0.27 s
59
Diastole duration
0.53 s
60
Incisure/Dicrotic Notch
Small rise in pressure during diastole representing closure of AO valve
61
Cardiac Output (CO)
Volume of blood being pumped by L.Ventricle into Aorta / min = 5.6 L/m (rest) HR x SV (70 x 80)
62
Total Peripheral Resistance (TPR)
Total resistance that must be overcome to push the blood through the circulatory system and create flow (P.art. - P.ven.) / CO 1/tpr = 1/Parm + 1/Pleg + 1/Pbrain
63
Mean arterial B.P
93 mmHg CO x TPR (Psys * 2xPdia) / 3
64
Why when calculating MABP we use 2x the Pdiastolic
Because since Diastole (0.53s) lasts almost 2x longer than Systole (0.27s), we give it a larger weighing by doing this
65
Regulation of CO
- Heterometric Reg. - Homometric Reg.
66
Heterometric Regulation
How different initial fiber lengths impact contraction force
67
Otto Frank's Experiment
- Proves Heterometric regulation. - Higher preload, stronger contraction - Greater fiber length, more forceful contraction
68
Starling's Experiment
- Proves Heterometric regulation. - Increased venous return, increasing EDV, led to greater stroke volume
69
Frank-Starling Law
Stroke Volume increases in response to increased ventricular blood volume (EDV), when all other factors remain constant
70
Preload
Increased venous return and Ventricular filling (EDV)
71
Afterload
Aortic pressure against which the heart pumps
72
Effects of increased afterload on BP
Systolic and Diastolic pressures both increase, but with a constant difference bw them Arterial pressure increases
73
Homometric Regulation
Force of contraction is changed independently of fiber length
74
Sympathetic Homometric Reg.
B1-AR = PKA 1) L-VGCC & RyR act. (Ca release) 2) TnI inhibits Ca binding to tropomyosin, Faster relaxation 3) Phospholamban act, regulates SERCA (in bw beats)
75
What Drug can achieve same results as Sympathetic Homometric Regulation
Isoproterenol (B-AR agonist)
76
Parasympathetic Homometric Reg.
M2-AR = Less PKA 1) No phosph. & activation of Ryr, VGCC, TnI 2) GIRKs activated = K+ 3) Atria and conducting system effected ONLY
77
Other factors that influence contractility
- Temperature - Ion concentrations - Hypoxia, Ischemia
78
Vessel ramification
Aorta (10^4) Small Arteries (10^7) Arterioles (4x10^10) Capillaries
79
Blood Volume in A, C, V, H
- A: 13% - C: 7% - V: 64% - H: 7%
80
Bernoulli's Law
Increase in speed of slow (dynamic pressure) occurs simultaneously with a decrease in hydrostatic pressure (side pressure)
81
Reynold's Number
Tendency of a flow to be Turbulent or Laminar <2000 : Laminar >3000 : Turbulent = (dens*D*v) / n (visc)
82
Laplace's Law
Tension within the wall of a sphere filled with a particular pressure depends on the thickness of the blood vessel wall
83
What vessels are Veins and Arterioles called?
- Veins: Capacitance vessels - Arterioles: Resistance vessels
84
Windkessel Effect
Converts intermittent pulsatile flow from heartbeat to steady flow. In Aorta & Large arteries (elastic)
85
What forms resting/Basal tone of Arterioles
- Myogenic tone (SMC) - Sympathetic tone
86
Lung type vessels
- Contain elastic fibers - Works under Passive mech. - Very Compliant - When Diameter increases, Resistance decreases
87
Kidney type vessels
- Contain smooth muscles - Work under Active mech. - Maintain BF in certain range via autoreg. - Pressure increase, Resistance increase (due to tension)
88
Why does resistance increase in Kidney type vessels with larger pressure?
1) SMC contains stretch activated non-spec. cation channels 2) Depol. activates VGCC 3) Vasoconstriction (Bayliss)
89
Non-invasive BP measurement
Sphygmomanometry Cuff inflated to P greater that Psys then slowly releases
90
Pulse pressure
Psys - Pdia = 120 - 80 = 40 mmHg
91
Effects of Increasing CO
- Overall Pressure increase - Psys more affected - Ppulse increases
92
Effects of Increasing TPR
- Changes Psys & Pdia equally - No change in Ppulse due to equal change
93
Effects of Lower compliance
- Psys Increases - Pdia decreases - Higher Ppulse
94
1 cmH2O in mmHg
0.7 mmHg
95
Effects of Hormones on TPR
- Estrogen: Vasodilator, lower TPR - Testosterone: Vasoconstrictor, higher TPR
96
Mean Pressure in Systemic Vessels (Aorta, Arteries, Arterioles, Capillaries, Veins)
100, 85, 35, 15, 0
97
Mean Pressure in Pulmonary Vessels (Arteries, Veins)
15, 5
98
Terminal Arterioles
- Smallest arterioles - 10-50 um - Highest in number - Single layer of SM (symp. inn)
99
Metarterioles
- Smaller than terminal arterioles - Discontinuous SM layer (not inn) - Origin of Capillaries - Material exchange
100
Precapillary Sphincter
- One smooth muscle cell that surrounds the capillary - Determines Open/Closed state of capillary - Modulation of blood flow
101
True Capillaries
- Smallest vessel - Exchange site - 5-7 um - Only endothelial cells (no SM) - Have pores
102
Postcapillary Venules
- Carry blood back to veins - Discontinuous SM - May exchange across wall
103
ArterioVenous Shunt (AV-shunt)
- Bypass bw Arterial & Venous systems - Direct link bw arteriole and venule - NOT part of microcirculation - Found in skin for thermoregulation (symp. control)
104
Continuous Capillaries (Tight Capillary)
- Most abundant (muscle, skin, lung) - Tight junctions - 100-200nm - Pinocytotic Vesicles
105
Fenestrated Capillaries
- For huge substance exchange - Larger pore diameter - Decreased wall thickness
106
Sinusoid (Discontinuous) Capillaries
- Pore is 1um range (even rbcs cells can cross) - Liver, spleen, bone marrow
107
3 Types of Diffusion through Capillary wall
- Diffusion (ions) - Pinocytosis (large molecules) - Hydrodynamic fluid exchange (pores)
108
Capillary Hydrostatic Pressure Art & Venous
- Arteriolar: 30 - 35 mmHg - Venous: 10 - 15 mmHg
109
Interstital Hydrostatic Pressure
Usually Negative, but 1mmHg in organs with a Capsule
110
Capillary & Interstitial Oncotic pressure (colloid osmotic)
- C: 25 mmHg - I: 5 mmHg (Proteins)
111
Total filtration Volume in Microcirculation
- 20 ml/min Filtrated - 18 ml/min Absorbed - 2 ml/min in interstitium goes to Lymph
112
Vasomotion
Vascular SM in periphery undergo cyclic contraction and relaxation to improve flow
113
Local vs Systematic Arteriolar resistance
- Local: P = Q * R - Systematic: P = CO & TPR
114
How does cAMP relate to muscle contraction
1) Adenlyly Cyclase makes cAMP 2) cAMP activates PKA 3) PKA phosphorylates & inh. MLCK 4) No phosphorylation of Myosin LC 5) No contraction
115
How does cGMP relate to muscle contraction
1) Guanylyl Cyclase makes cGMP 2) cGMP activates PKG 3) PKG inh. IP3-R 4) PKG act. MLCP 5) K+ channel opening
116
Physiological Vasoconstrictors
- NE (a1-AR) - Angiotensin II - Endothelin I - TXA2 - ADH / Vasopressin
117
Physiological Vasodilators
- Adenosine - PGE2 - PGI2 - NO - ANP (cGMP)
118
Starling Forces
Forces that control movement of Fluid in and out of Capillaries (Hydrostatic and Oncotic Pressures)
119
Effective Filtration Pressure
- Positive: Filtration - Negative: Absorption θ = Reflection coefficient describes how permeable membrane is. (0=H2O, 1= Albumin)
120
What makes up Lymphatic System
- Lymphatic Capillaries - Collecting Lymphatics - Lymph Node - Central Lymphatics
121
Lymphatic Capillaries
- Blind ended - Uptake of fluid & Large molecules - Button-like junctions functioning as primary valves to stop back-flow to interstitial valves
122
Collecting Lymphatics
- Zipper like junctions - Lymphatic valves - SMC coverage - Maintains forward flow
123
Lymph Node
- Efferent/Afferent Lymph vessels - Sampling and filtering in peripheral structures
124
Central Lymphatics
- Thoracic/Right lymphatic Duct - Lymphovenous valve separates blood and Lymph components
125
Interstital Fluid makeup
- Gel Phase (99%): Hydrate coat of matrix proteins, PG, GAG, Hy. acid - Soluble Phase (1%): Free fluid
126
What factor induce Lymphatic growth in Development?
VEGFC Vasculoendothelial GF C
127
Central Venous Pressure (CVP)
0 - 2 mmHg Pressure of Vena Cava and Right Atrium
128
Mean systemic filling pressure (MSFP)
Average pressure in Veins and Arteries when heart isnt pumping = 7 mmHg in Cardiac arrest
129
Factors influencing Venous P changes
- Retrograde effect of Heart function - Respiration - Foot veins (Skeletal M) - Walking
130
Pump functions on Venous system
- Peripheral musculovenous Pump - Thoraco-abdominal Pump
131
Fast-acting Baroreceptors (High P B.C)
- Stretch receptors in Aortic arch and carotid sinuses - Sensitive in range 50-200 mmHg (carotid), 100-200 mmHg (aortic) - Contain Elastic fibers
132
Slow-acting Baroreceptors (High P B.C)
- Renin-Angiotensin system - Detects P drop in Renal A. via mechanoreceptors in afferent arterioles of Kidney - Pressure drop = Renin secretion - Leads to ANGII (vasoconstrictor)
133
Low-Pressure Baroceptors
- Found within Venous system - Sense changes in Blood Volume - S/I Vena Cava & RA sinus venarum cavarum - Help by Na+ excretion
134
Brainbridge Reflex
- Increase in Atrial pressure stimulates baroreceptors that travel via Vagus N to NTS to Increase HR - Leads to more CO and increased GFR in kidney
135
Peripheral Chemoreceptors
- Near bifurcation of Common carotid and Aortic arch - pO2 sensitive (mostly)
136
Central Chemoreceptors
- In Medulla behind BBB - pCO2 sensitive
137
Cushing Reflex
Increased intracranial pressure compresses cerebral arteries and activates Central chemoreceptors and CVLM lowers HR BP still high cause no communication bw CVLM & RVLM
138
What carries Baroreceptor Information to Brain centers?
- Aortic: Vagus Nerve - Carotid: Glossopharyngeal N (both to NTS in Medulla)
139
What happens when NTS is stimulated
Depressor effect
140
Cardiopulmonary Baroreceptor
- Low-pressure Baroreceptor - Type A: Tension during atrial Systole - Type B: Tension during atrial Diastole (Info to Vagal center)
141
Respiratory sinus arrhythmia
- Inhalation causes Sympathetic stimulation - Exhalation causes Parasympathetic stimulation Affected mostly by Vagal stimulation since ACh acts quicker
142
Chemoreceptor Reflex
- Primary effect: Medullary Vagal center slows down HR to reduce O2 usage (hypercapnia) - Secondary effect: Inhibits medullary vagal center, increased HR (hypocapnia)
143
Local Hypoxia
1) Low intracellular ATP 2) ATP-act. K+ channels open 3) Hyperpolarization 4) L-VGCC decrease act 5) Vasodilation
144
Reactive Hyperemia /Hypoxia
Increase in perfusion due to a short period of Ischemia - Increase in BF is proportional to length of Ischemia
145
PGI2 effects
Can cause vasodilation by increasing cAMP through Gs coupled-R
146
AVDO2 Arterial
200 ml/L
147
AVDO2 Venous
150 ml/L
148
AVDO2 Body Average
50 ml/L
149
AVDO2 Heart
120 - 130 ml/L
150
pO2
95 mmHg
151
pCO2
40 mmHg
152
Flow to Heart Rest/Exercise
- Rest: 250 ml/min - Exercise: 1250 ml/min
153
O2 consumption of Heart
30 ml/min
154
Transmural Pressure in heart
= Extramural - Intramural P - Ex.M: Ventricle P - Intra. M: Aortic P
155
Blood flow to Skeletal Muscle Rest/Exercise
- Rest: 800 - 1000 ml/min - Exercise: 20x higher
156
AVDO2 Skeletal Muscle
60 ml/L
157
Flow to Splanchnic and O2 consumption
1000 - 1500 ml/min Uses 40 ml/min
158
AVDO2 Splanchnic
30 ml/L
159
What can Cholecystokinin and Gastrin cause in Splanchnic circulation
Vasodilation
160
Sympathetic effect on Splanchnic Circulation
Venoconstriction (a1-AR) Increased venous return and CO
161
Flow Cutaneous Circulation
100 - 300 ml/min
162
AVDO2 Cutaneous
20 - 30 ml/L
163
Where does Thermoregulation happen
Apical Skin (Palms, Face, Plantar) - Arteriovenous anastomosis
164
AVDO2 Brain
60 ml/L
165
Flow of Brain and O2 consumption
850 ml/min Consumes 30 ml/L
166
Main Blood supply of Brain
- ICA: 350 ml/min - Vertebral A: 75 ml/min
167
Perfusion P in brain when standing
15 mmHg less than MABP 93 - 15 = 78 mmHg
168
Total CSF
150 ml
169
Daily CSF production
500 ml/day and is equal to absorption cause amount is always constant

Physiology 1 (12 decks)

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