Unit 5: Cardiovasular Physiology Flashcards
1
Q
preclampsia can lead to …
A
speech and language delays
2
Q
1 cause of death
A
cardiovascular disease
3
Q
what % of cardiovascular disease is preventable
A
80
4
Q
why is there a delay in the av node
A
to allow time for atrial contraction to complete filling of the ventricles
5
Q
cardiac conductance
A
- SA node (pacemaker cells)
- AV node
- bundle of Hiss
- Purkinje cells/fibers
6
Q
generation of pacemaker action potentials
A
7
Q
PQRS complex what does everything stand for
A
8
Q
what does a shortened PR segment in a PQRS complex signify
A
fast heart rate (arrythmia)
9
Q
what could disrupt the TP interval in a PQRS complex
A
potassium or electrical abnormalities
10
Q
risk of a small or large ST segment in a PQRS complex
A
- small = heart attack risk
- big = myocardial disruption
11
Q
systolic definition
A
when muscles are contracting
12
Q
diastolic definition
A
when muscles are relaxing
13
Q
can any of the heart functions be felt
A
yes, ventricular ejection
14
Q
parasympathetic and sympathetic heart rate control centers
A
- parasympathetic: vagus nerve (medulla)
- sympathetic: cardiac nerve (T1-T4)
15
Q
behavioral factors of ideal cardiovascular health
A
- no smoking
- good diet
- being active
- losing weight
- managing blood pressure
- controlling cholesterol
- reducing blood sugar
16
Q
what affects cardiovascular health
A
- genetics
- familial (trauma, finance, education)
- preemies
- behavior
17
Q
acute cardiovascular response to exercise
A
- bone marrow and EPO stimulation to make more rbcs
- vagal tone and function increase
- ATP, glucose, and O2 used to meet metabolic demand
-angiogenesis (blood vessel creation)
18
Q
hypotension
A
low blood pressure (<90/60)
19
Q
hypertension
A
- high blood pressure (>130/80)
- usually silent (unless hypertensive crisis)
- 12.8% of all deaths
- risk factor for heart disease, heart failure, peripheral vascular disease, renal impairment, retinal hemorrhage, visual impairment and stroke
20
Q
hypoperfusion
A
reduced amount of blood flow
21
Q
most important hormonal system involved in Na+ and blood pressure regulation
A
renin-angiotensin-aldosterone system
22
Q
hypovolemia
A
a state of low extracellular fluid volume, generally secondary to combined sodium and water loss
23
Q
cardiovacular disease includes
A
- sudden cardiac death
- atherosclerosis
- atrial fibrillation
- stroke
- heart failure
24
Q
sudden cardiac death cause
A
- arrythmia, errors of conduction
- long qt 1, long qt 2, long qt 3, cpvt, brugada syndrome
25
hypertrophic cardiomyopathy
- walls of the heart chamber are too thick
- reduces the heart's ability to do its job
- obstructs flow of blood from the heart to the rest of the body (thickened heart muscle is too stiff to pump effectively)
26
hypertrophic cardiomyopathy symptoms
usually during exertion:
- shortness of breath
- chest pressure
- fainting or fatigue
- heart palpitations
27
hypertrophic cardiomyopathy cause
complex inherited genetic mutation
28
hypertrophic cardiomyopathy treatment
- medication (2/3)
- lifestyle changes (1/3)
- septal myectomy (open heart surgery): a portion of the thickened heart wall is surgically removed to improve blood flow
- septal ablation: a small portion of the thickened heart wall is intentionally scarred using a long thin tibe
29
atherosclerosis
narrowing or hardening of arteries due to plaque build up
- deposits of fat, cholesterol, and other substance block normal blood flow or cause a clot
30
what diseases can atherosclerosis cause
- carotid artery disease (in the arteries that supply blood to the brain, can cause stroke)
- coronary artery/heart disease (in the arteries to the heart, can cause heart attack)
- chronic kidney disease (in the renal arteries, can cause loss of kidney function)
- peripheral artery disease (in the arteries in the legs, can cause amputation and ulcers)
31
most common type of heart disease
coronary artery/heart disease
32
atrial fibrillation
- abnormal electrical impulses suddenly start firing in the atria
- most common arrythmia
33
stroke
- an interruption of blood flow to the brain
- without oxygenated blood, brain cells die
34
stroke types
- ischemic
- hemorrhagic
35
ischemic stroke
- clot or mass blocks a blood vessel cutting off blood flow to a part of the brain
- most common
- 1/4 of cases have no known cause
36
hemorrhagic stroke
weakened blood vessel like an aneurysm ruptures and spills blood into the brain
37
possible hidden causes of a stroke
- irregular heartbeat
- heart structure problems
- artery hardening
- blood clotting disorder
38
why is it important to find the cause of a stroke
to implement prevention strategies
39
heart failure
- a condition in which your heart does not pump blood efficiently around the body
- makes it difficult for the body to get oxygen and blood
40
heart failure symptoms
- breathlessness
- fluid build up on the lungs
- swollen legs, ankles, and abdomen
- persistent cough
- tiredness
- palpitations
- fainting
- dizziness
41
heart failure causes
- high blood pressure
- coronary heart disease
- cardiomyopathy
- heart valve damage
- arrhythmia
- congenital heart disease
- myocarditis
- some drugs used in cancer treatment
- excessive alcohol consumption
42
effective heart properties
- regular contractions at an appropriate rate for metabolism
- guaranteed time for ventricular filling after atrial and ventricular contractions
- contraction duration long enough for physical movement of fluid
- contractile strength sufficient to generate appropriate pressures
- ventricular pressure directed towards exit valves
- coordination of left and right atrial/ventricular contractions
- matched volumes for emptying and filling
43
location of the heart
- in the mediastinum
- enclosed by the pericardium
- medial
44
size of the heart
- 250-350 grams
- size of a human fist
45
adipose tissue around the heart function
insulate and protect
46
pericardium function
attaches heart to surrounding tissues
- tough double layered membraneous sac
47
pericardium components
- visceral layer (attaches to heart surface)
- parietal layer (outer pericardial layer)
- lubricating fluid between layers reduces friction during movement of heart surface with contraction
48
myocardium
- heart muscle
- elastic, lubrication for movement
- fibers branch and are connected with intercalated discs (connect cells, gap junctions allow for action potential conduction)
- striated appearance
- ordered sarcomere arrangement
- irregular shaped cells
- single centralized nuclei
- sarcoplasmic reticulum and T-system present
49
what characteristic is unique to cardiac muscle
no requirement for external neural input
50
all cardiac cells display ?
pacemaker activity
51
cardiac muscle acts as a __________
syncytium
52
syncytium
network of cardiac muscle cells connected by gap junctions that allows coordinate contraction of the ventricles
53
heart activity controlled by...
- ANS (sympathetic and parasympathetic)
- control of rate and contractile strength
54
hypertrophy types
- physiological
- pathological
55
physiological hypertrophy (cause, outcome)
- pregnancy
- exercise
- physiological stimulus
- enhanced function
- improved metabolism
56
hypertrophy definition
when heart muscles enlarge
57
pathological hypertrophy
- hypertension/high afterload (fibrotic lesions)
- infarction (fibrotic lesions, impaired electrical function)
- diabetes (fatty and fibrotic lesions, increased ventricular mass, diastolic dysfunction)
58
heart valves function
- one-way valve that prevents the backward flow of blood
- when pressure is greater behind the valve, it opens
- when pressure is greater in front of the valve, it closes
59
heart valves labeled
- tricuspid valve: located between the right atrium and the right ventricle
- pulmonary valve: located between the right ventricle and the pulmonary artery
- mitral valve: located between the left atrium and the left ventricle
- aortic valve: located between the left ventricle and the aorta
60
chordae tendinae function
prevent opening of valve in the wrong direction
61
bicuspid aortic valve
- untreated bicuspid aortic valve can eventually lead to symptoms of heart failure (shortness of breath, fatigue, and swelling)
- aortic aneurysm might develop downstream from the aortic valve, can lead to bleeding or rupture
- may eventually leak (aortic regurgitation) and/or narrow (aortic stenosis)
62
aortic regurgitation
allows some of the blood that was pumped out of the left ventricle to leak back in
63
av stenosis
- occurs when the aortic valve narrows and blood cannot flow normally
- higher longevity is harder to repair
- tightened fibrous valves impair function
64
myocardium progression to heart failure
65
coronary arteries
- aortic arch
- superior vena cava
- inferior vena cava
- right coronary artery
- left coronary artery
- right coronary artery
- great cardiac vein
- left pulmonary veins
- right pulmonary veins
66
sinoatrial (SA) node
- cardiac pacemaker
- located within the right atrial wall at junction with superior vena cava
- 80-100 action potentials per minute
67
atrioventricular (AV) node
- located above cardiac septum at junction of atria and ventricles
- 40-60 action potentials per minute
68
bundle of his
- located down ventricular septum to apex
- 20-40 action potentials per minute
69
purkinje fibers
- located throughout ventricular myocardium from apex to base
- 15-40 action potentials per minute
70
what limits the rate of production of action potentials by the SA node
how fast Na+ leaks in through funny channels (HCN channels)
71
electrical conduction in the heart
72
cardiac action potential
- exhibit prolonged plateau phase (due to activation of slow L-type Ca2+ channels) accompanied by prolonged period of contraction (ensures adequate ejection time)
73
refractory period means ? is impossible
tetanus
74
relationship of action potentials and contractile response in cardiac muscle
75
action potential in cardiac contractile cells steps
76
phases of ventricular action potential
- phase 0: rapid depolarization
- phase 1: early repolarization
- phase 2: action potential plateau
- phase 3: final rapid repolarization
- phase 4: resting membrane depolarization and diastolic depolarization
77
phase 0: rapid depolarization
- excitatory stimulus or pacemaker potential depolarizes cell membrane beyond -70 mV
- at -70 mV, Na+ channels are activated and allow inward current
- current is brief but enormous, peaking at +47 mM membrane potential
78
phase 1: early repolarization
- potential increase results in opening of outward K+ channels and inward Ca2+ channels
- repolarization from +47 mM to +10 mV due to rapid closure of Na+ channels and activation of transient outward K+ current
79
phase 2: action potential plateau
- membrane potential remains depolarized near 0 mV
- maintained by 2 inward Ca2+ currents and 4 outward K+ currents
80
phase 3: final rapid repolarization
outward K+ current dominate and cause rapid repolarization
81
phase 4: resting membrane depolarization and diastolic depolarization
- outward K+ channels in phase 3 deactivate, membrane is repolarized to -40 mV
- voltage-dependent Na+ channel that causes phase 0 remains inactivated until this happens
82
sinoatrial versus ventricular myocyte action potentials
83
(sinoatrial action potential) the membrane is leaky to ? most of the time, but is much leakier when ...
K+; voltage dependent potassium channels open in response to depolarization
84
(sinoatrial action potential) membrane potential determined by
potassium (K+)
85
(sinoatrial action potential) if depolarization occurs, what will drive membrane potential back down
increased K+ potential
86
(sinoatrial action potential) funny current definition and reason behind the name
- current that allows Na+ to leak into SA nodal cells
- an odd
(funny) channel because it is voltage-dependent but opens during membrane hyperpolarisation rather than depolarisation
87
(sinoatrial action potential) key to automaticity
slow, depolarising baseline drift
88
(sinoatrial action potential) SA nodal cells constantly depolarise slowly, except during ?
hyperpolarisation – such as when K+ leaves the cell abruptly
89
(sinoatrial action potential) two sets of voltage-gated Ca2+ channels that contribute to the action potential
- T-type (transient) Ca2+ channels
- L-type (long-lasting) Ca2+ channels
90
(sinoatrial action potential) T-type Ca2+ channels
- opens at a specific level of membrane depolarization
- open transiently (T-type), providing the initial depolarising to fire the action potential
91
(sinoatrial action potential) L-type Ca2+ channels
- mediate the initial depolarising to fire the action potential
- in non-pacemaker atrial myocytes this entry of Ca2+ causes
contraction
92
(sinoatrial action potential) resetting membrane potential
- after a brief delay the L-type calcium channels close and the voltage-gated K+ channels open
- hyperpolarisation opens the Na+ leak channels, starting the process again
93
(ventricular action potential) resting membrane potential rests at a stable level until ...
an action potential arrives from the bundle of His
94
(ventricular action potential) bundle of His action potential arrives which leads to ...
an increase in Ca2+ entry and contraction of the myocyte
95
(ventricular action potential) does the action potential in a ventricle look similar to an atrium?
no, more closely resembles the action
potential in skeletal muscle
96
(ventricular action potential) rapid cell depolarization to contractions
- fast Na+ channels open
- opens L-type Ca2+ channels (SA node cells)
- Ca2+ entry initiates contraction
97
(ventricular action potential) contraction to resting membrane potential
- voltage-gated K+ channels open as the Na+ and Ca2+ begin to close, causing hyperpolarisation
- membrane potential back to its resting level
98
(ventricular action potential) refractory period
- similar to skeletal muscle but the period is quite long so that tetanic contraction is impossible to allow ventricle filling
- ventricular myocytes cannot sustain an action potential due to the inactivation of Na+ channels
99
what are ECGs useful for
- assess heart orientation
- localize areas that do not conduct electrical activity normally
- assess myocardial hypertrophy or atrophy
- accurate heart rate measurement
100
prolonged PR interval meaning
heart block/delay
101
short PR interval meaning
AP at risk of cascading on each other (can lead to ventricular tachycardia)
102
by how many seconds does atrial contraction precede ventricular contraction
160 msec
103
(PQRS complex) P wave
atrial depolarization
104
(PQRS complex) PR segment
AV nodal delay
105
(PQRS complex) QRS complex
ventricular depolarization (atria repolarizes simultaneous)
106
(PQRS complex) ST segment
time during which ventricles are contracting and emptying
107
(PQRS complex) T wave
ventricular repolarization
108
(PQRS complex) TP interval
time during which ventricles are relaxing and filling
109
different ECG abnormalities
- rate abnormalities
- rhythm abnormalities
- cardiac myopathy
110
ECG rate abnormalities
111
ECG rhythm abnormalities
112
ECG cardiac myopathy
113
where are ion channels are related proteins responsible for de/repolarizing found
- on the cell surface
- in T-tubules
114
cardiac cycle definition
all the events associated with the flow of blood thru the heart during a single complete heartbeat
115
two phases of a heart beat
- systole
- diastole
116
does myocardium contract and repolarize faster at low or high heart rates
high
117
cardiac cycle sequence of events
atrial diastole -> ventricular diastole -> atrial systole -> ventricular systole
118
why do valves open passively
pressure gradients
119
mechanical phases of cardiac cycle
120
end diastolic volume (EDV)
volume of blood in ventricle at end of diastole
121
end systolic volume (ESV)
volume of blood in ventricle the end of systole
122
stroke volume (SV)
volume of blood ejected from ventricle in each cycle
123
ejection fraction definition and range
- EDV% ejected per stroke
- ranges 50%-75%
124
what does one pressure volume loop represent
one cardiac cycle
125
cardiac output
volume of blood ejected by each ventricle each minute
126
venous return
volume of blood returning to atrium each minute
127
venous return must be __________ cardiac output
equal to
128
factors that influence cardiac output
- metabolism (ca varies with activity level)
- age (metabolic activity declines with age)
- body size (co increases proportionately to body surface area)
129
cardiac output controlled by
- heart rate
- stroke volume
130
heart rate
the number of times the heart beats per minute
131
what controls heart rate
- SA node
- parasympathetic (vagus) cholinergic input K+ permeability
- sympathetic activity and epinephrine
- exercise
132
what controls stroke volume
- end diastolic volume (controlled by venous return)
- sympathetic activity and epinephrine
- preload
- contractility (extrinsic and intrinsic influences)
133
exercises reduced heart rate to >110 bpm via...
symapthetic stimulation of:
- SA node (decreases K+ permeability, depolarizing effect)
- AV node (reduced delay via increase Ca2+)
134
frank-starling law
relationship between edv, contraction strength, and sv
135
frank-starling curve
show how changes in ventricular preload lead to changes in stroke volume
136
frank-starling curve
show how changes in ventricular preload lead to changes in stroke volume
137
frank-starling mechanism
Length Tension Relationship
– Varying Degree of
Stretching of Myocardium by
EDV
138
preload
- wall stress (force applied to unit
cross-sectional area) in resting myocardium
- depends on the end-diastolic pressure, chamber radius, and wall thickness
139
Laplace's Law
- in a hollow sphere
- internal pressure is proportional to the wall tension and inversely proportional to the internal radius
140
tension
a force equal to wall stress time wall thickness
141
contractility
the force of a contraction achieved from a given initial fiber length
142
how can contractility force be increased
- increased contractility
- increasing resting fiber length through end-diastolic stretch
143
positive inotropic agents
factors that increase contractility
144
factors that increae contractility
- sympathetic neurotransmitters
- noradrenaline
- circulating adrenaline
- beta agonists
- digoxin
- reduced beat interval
145
negative inotropes
- ischemia
- acidosis
- heart failure
- anesthetics
- parasympathetic fiber activity
- beta antagonists
- calcium channel blockers
146
afterload
force per unit cross-sectional area (stress) that opposes the shortening of an isotonically contracting muscle
147
what does after load depend on
- arterial pressure
- chamber radius
- wall thickness
148
what is weakened in systolic heart failure
heart contractility
149
cardiogenic shock
150
steady state
151
acute myocardial infarction
152
is the circulatory system open or closed
closed
153
blood pressure
force exerted by blood
154
blood flow pattern
high to low pressure
155
circulatory system gradient function
maintain blood flow
156
why does the heart have a pressure gradient
for bulk blood flow
157
are pressures throughout vasculature constant
no
158
pressure gradient formula (pulmonary circuit)
pressure in pulmonary arteries - pressure in pulmonary veins
159
pulmonary arterial pressure
15 mmHg
160
pulmonary venous pressure
0 mmHg
161
total pulmonary circuit pressure gradient (#)
15 - 0 = 15 mmHg
162
pressure gradient formula (systemic circuit)
pressure in aorta - pressure in vena cava (before it empties into right artium)
163
mean arterial pressure (MAP) definition
pressure in aorta
164
central venous pressure (CVP) definition
pressure in vena cava
165
mean arterial pressure (#)
85 mmHg
166
central venous pressure (#)
0 mmHg
167
total systemic circuit pressure gradient (#)
15 - 0 = 15 mmHg
168
is mean arterial pressure (MAP) diastolic or systolic pressure
both (2/3 diastolic and 1/3 systolic)
169
what dictates blood flow
- pressure gradients in vasculature
- resistance in vasculature
170
blood flows from ______ pressure to ______ pressure
high; low
171
what does the heart create for the bulk flow of blood
pressure gradient
172
flow formula
pressure gradient/resistance
173
poiseuille's law
resistance = (length x viscosity)/radius^4
174
factors affecting resistance to flow
- length of vessel
- viscosity of fluid
- radius of vessel (most important)
175
volume flow rate formula
flow = volume/time
176
regulation of arteriole radius
- vasoconstriction
- vasodilation
177
vasoconstriction
decrease radius (by contracting smooth
muscle) --> increase resistance--> decrease
blood flow
178
vasodilation
increase radiation (relax smooth muscle) --> decrease resistance --> increase blood flow
179
arteriole radius depends on ?
contraction state of smooth muscle
180
arteriole radius at rest
arteriolar tone (partially contracted)
181
arteriole radius during vasoconstriction
increased contraction (decreased radius)
182
arteriole radius during vasodilation
decreased contraction (increased radius)
183
functions of arteriole radius changes
- controlling blood flow to individual capillary beds
- regulating mean arterial pressure
184
types of factors that influence vasodilation and vasoconstriction
- extrinsic factors
- intrinsic factors
185
extrinsic factors that influence vasodilation and vasoconstriction
- autnomic nerves
- hormones
186
intrinsic factors that influence vasodilation and vasoconstriction
- metabolism (active hyperemia)
- changes in blood flow (reactive hyperemia)
- myogenic response
- locally secreted chemical messengers
187
active hyperemia
increases in metabolism decrease O2 and cause vasodilation
188
reactive hyperemia
reduction in blood flow cause vasodilation
189
myogenic response
- stretch of arteriolar smooth muscle
- high perfusion pressure causes vasoconstriction
190
myogenic response purpose
keep blood flow constant
191
chemical messengers that influence vasodilation
- nitric oxide
- prostacyclin
- adenosine
- bradykinin
192
chemical messengers that influence vasoconstriction
endothelin-1
193
local chemical influences for intrinsic regulation of vessel radius
- hypoxia
- increased CO2
- decreased pH
- increase in potassium ions
- adenosine
194
local physical influences for intrinsic regulation of vessel radius
- heat (increases blood flow by causing localized vasodilation)
- cold (decreases blood flow by causing localized vasoconstriction)
- myogenic response to stretch (autoregulation)
195
how does decreased pH influence intrinsic regulation of vessel radius
- carbonic acid is generated from high CO2 (metabolism waste)
- lactic acid is produced from anaerobic metabolism of ATP production
196
myogenic response to stretch (autoregulation)
- arteriolar smooth muscle responds to being stretched by myogenically increasing its tone (contracting), therefore
resisting the stretch
- conversely, a decrease in stretch results in decreased myogenic tone
197
factors affecting total peripheral resistance
- arteriolar radius
- blood viscosity
198
blood viscosity
number of red blood cells
199
central venous pressure
pressure in the large veins of the thoracic cavity that lead into the heart
200
what does the pressure gradient between central veins and atria do
drive blood back the the heart
201
decrease in venous pressure _________ driving force for venous return
decreases
202
factors that influence central venous pressure and venous return
- skeletal muscle pump
- respiratory pump
- blood volume
- venomotor tone favors venous return
203
respiratory pump
- inspiration
- expiration
204
how does blood volume influence central venous pressure and venous return
decreased blood volume decreases central venous pressure (bleeding, dehydration)
205
venomotor tone
sympathetic nerves constrict veins
206
mean arterial pressure determinants
- heart rate
- stroke volume
- total peripheral resistance
207
total peripheral resistance
combined resistance of all blood vessels
208
effects of cardiac output on mean arterial pressure
209
effects of total peripheral resistance on mean arterial pressure
210
mean arterial pressure
driving force for blood flow
211
MAP < normal
- hypotension
- inadequate blood flow to tissue
212
MAP > normal
- hypertension
- stress on heart and blood vessel walls
213
when does systolic pressure occur
ventricular contraction
214
systolic pressure in mmHg
120 mmHg
215
when does diastolic pressure occur
ventricular refilling
216
diastolic pressure in nnHg
80 mmHg
217
pulse pressure
difference between systolic and diastolic pressure
218
pulse pressure at rest
40 mmHg
219
high pulse pressure at rest is indicative of ?
vascular disease
220
auscultation
- blood pressure measurement
- recorded at heart level via brachial artery
221
korotkoff sounds
sounds heard during auscultation
222
auscultation process
- inflate cuff above expected systolic pressure
- slowly deflate cuff (blood flows when BP > cuff pressure)
- korotokoff sounds indicate systolic pressure
- diastolic pressure indicated at disappearance of muffled sound
223
sphygmomanometer
an instrument for measuring blood pressure
224
sphygomanometry
225
how long is short term regulation of MAP
seconds to minutes
226
how long is long term regulation of MAP
minutes to days
227
short term regulation of MAP
- regulates cardiac output and total peripheral resistance
- heart and blood vessels
- primarily neural control
228
long term regulation of MAP
- regulates blood volume
- involves kidneys
- primarily hormonal control
229
most important hormonal system involved in regulating Na+
renin-angiotensin-aldosterone system
230
neural control of MAP
negative feedback loops
231
negative feedback loop of MAP neural control
- detector = baroreceptors
- integration center = cardiovascular centers in the brainstem
- controllers = autonomic nervous system
- effectors = heart and blood vessels
232
baroreceptor definition
- stretch receptors
- specialized nerve endings that respond to a vessel wall stretch
233
arterial baroreceptors
- high pressure baroreceptors
- sinoaortic baroreceptors
234
location of arterial baroreceptors
- carotid sinus
- aortic arch
235
cardiovascular control center
- medulla oblongata
- sympathetic nervous system
- parasympathetic nervous system
236
location of cardiac and venous baroreceptors
- walls of large systemic veins
- walls of atria
237
low pressure baroreceptors
volume receptors
238
autonomic output to cardiovascular effectors, parasympathetic input to ?
- SA node (decrease heart rate)
- AV node
239
autonomic output to cardiovascular effectors, sympathetic input to ?
- SA node (increase heart rate)
- AV node
- ventricular myocardium (increase contractility)
- arterioles (increase resistance)
- veins (increase venomotor tone)
240
baroreceptor reflex
negative feedback loop to maintain blood pressure at normal level
241
components of baroreceptor reflex
- detector = baroreceptors
- afferents = nerves
- integration center = cardiovascular control center
- efferents = autonomic nervous system
- effectors = heart, arterioles, veins
242
types of baroreceptors
- A fibers (myelinated)
- C fibers (unmyelinated)
243
A fiber baroreceptors
- low pressure (30-90 mmHg)
- important at rest
244
C fiber baroreceptors
- high pressure (70-140 mmHg)
- increasingly active at higher pressures
245
baroreceptor reflex - a person who had been lying down stands up too quickly
- gravity causes venous pooling in the legs
- decreases in venous resistance = decrease in cardiac output
- decrease in blood pressure
- baroreceptors sense the decrease and reflex occurs
- reflex causes increased sympathetic and decreased parasympathetic activity
- cardiac output and total peripheral resistance increase
- blood pressure is increased to normal
246
extra inputs to cardiovascular system control
- bainbridge reflex
- atrial stretch receptors
247
bainbridge reflex
- vena cava stretch receptors --> neural mediated increase heart rate
- avoids venous congestion
248
atrial stretch receptors
- myelinated vagal afferents sensitive to blood volume
- located at junction of great veins and atria
- influence endocrine regulation regulation of blood volume
249
hemorrhage causes
- baroreceptor reflex
- increase in sympathetic activity
- decreases in parasympathetic activity
250
response to hemorrhage
- reflex compensation
- MAP compensated only to near-normal level
251
baroreceptor reflex in the GI tract
- increased resistance
- decreased blood flow
252
baroreceptor reflex in the brain
- vasculature not subject of extrinsic control
- no change in resistance
- blood diverted from GI tract to brain
253
hormones that control mean arterial pressure
- epinephrine
- vasopressin
- angiotensin II
254
epinephrine control of mean arterial pressure
- released by adrenal medulla in response to sympathetic activity
- increases mean arterial pressure
- increases heart rate and stroke volume
- increases total periphery resistance on arterial smooth muscle
- increases venomotor tone on smooth muscle of veins
255
vasopressin and angiotension II control of mean arterial pressure
- vasoconstrictors
- increases total periphery resistance
- increase mean arterial pressure
