Vodcasts Flashcards
What are intercalated disks?
connects branched cardiac muscle fibers
What is the benefit of intercalated disks in cardiac muscles?
improves conduction of electrical pulses
What is the biggest difference between cardiac and skeletal muscles?
cardiac are branched
Are cardiac muscles smaller or larger than skeletal muscles?
smaller
Are cardiac muscles mono or multinucleated?
mononucleated
Do cardiac muscles or skeletal muscles have NO motor units?
cardiac
What are demosomes?
connections between muscle cells that aid in contraction
what are gap junctions?
allows for ion flow in muscles (spread of action potential)
Cardiac muscles contain sacroplasmic reticulum just like skeletal muscles, but hold more/less Ca2+
less Ca2+
Why is it important cardiac muscles have less Ca2+ in the sarcoplasmic reticulum?
strength of contraction depends on influx of Ca2+
What is a consequence of cardiac muscles having to bring in Ca2+ from outside of cell for contracts (since it has less Ca in SR than skeletal muscles)?
longer depolarization phase
Do cardiac muscles have a longer or shorter refractory period than skeletal muscles? And why?
longer
prevents tetany
What is tetany?
sustained contraction of muscle
What makes the refractory period longer in cardiac muscles?
tension in muscle peaks during refractory period NOT during action potential to prevent tetany
Longer refractory period in cardiac muscles aids in contraction _________
delays
Where does the heart muscles get most of its energy?
fatty acid oxidation from mitochondria
What is the second place the heart muscles get thier energy from?
glucose
Is there a change in [ATP] in cardiac muscles?
NO
hydrolysis = synthesis
What are the 3 other system that are used to regulate blood pressure?
- RAS (Renin-Angiotensin system)
- chemoreceptors
- low pressure baroreceptors
What is RAS (Renin-Angiotensin system)?
regulates BP by regulating blood volume via the kidneys
What are the steps to RAS (Renin-Angiotensin system) regulating a drop in BP?
- drop in BP
- drop in blood level in kidneys
- renin (protease) is proiduced and cleaves AN (angiotensinogen) into AT I
- AT I circulates to lungs where its converted into AT II
- AT II causes release of aldosterone (steroid hormone)
- aldosterone increases Na2+ reabsorption whch increases H2O in ECF
- increased fluid volume
- increased BP
What is the protease in the RAS (Renin-Angiotensin system)?
renin
What is released in the RAS (Renin-Angiotensin system) that causes increased Na2+ reabsorption to increase blood volume?
aldosterone
How does angiotensinogen II aid in resitance?
vasoconstrictor = increased resistance
How does aldosterone work in the RAS?
enters kidney cells where receptor is located and enters nucleus to increase transcription of Na and K channels so Na and H2O can increase fluid volume
What in the RAS increases Na+ and H2O absorption?
aldosterone
What is the actual main role of chemoreceptors?
stimulate breathing
Where are chemoreceptors located?
carotid and aortic bodies
What specialized nerves do chemoreceptors have?
type I glomus cells
What do type I glomus cells do?
sensory receptors for O2, CO2 and pH
If arterial PO2 is low…
vasocontrstriction or vasodilation of gut, kidneys and muscles and why?
vasoconstriction to redirect oxygen in blood to brain/heart/lungs
What is ischemia?
cut off blood flow to brain
If brain becomes ischemic, chemoreceptors will cause increased/decreased resistance and why?
increased
redirects blood to brain
What do low pressure baroreceptors respond to?
stretch in right atria (low pressure side)
change in blood volume
What does low pressure baroreceptors release when right atrium stretches? What about right ventricle?
ANP
BNP
If atrium stretches more than normal Na2+ and H2O is excreted or uptaken to bring BP back to normal?
excreted
If atrium stretches more than normal blood volume increases/decreased to bring BP back to normal?
decreased
When BP is low and its sensed by a regular baroreceptor, what is the affect on…
resistance –
HR –
stroke volume –
vasodilation/constriction
resistance – increases
HR – increases
stroke volume – increases
vasoconstriction
**sympathetic response
When there is an increase in pressure at the atrial receptors, what is the affect on HR to get BP back to normal and why?
increase HR to increase CO so there is an increase in renal excretion of salt and H2O do decrease volume
When BP is high and its sensed by a regular baroreceptor, what is the affect on…
resistance –
HR –
stroke volume –
vasodilation/constriction
resistance – decrease
HR – decrease
stroke volume – decrease
vasodilation
** parasympathetic response
When pressure is high at the low pressure baroreceptors, is blood volume going to try and be reduced or increased?
reduced
How does the low pressure baroreceptor decrease blood volume in regards to HR to decrease BP?
increase HR—> increase CO so there is an increase in renal excretion of salt and H2O in urine
How does the low pressure baroreceptor affect pre-load to increase blood volume to increase BP?
increase pre-load
*sympathetic response
What happens when you have orthostatic hypertension?
after standing up, upper body BP drops and body raises BP to compensate
What physiological affects happen when you have orthostatic hypertension and you stand up?
(drop in BP so body is trying to raise BP)
vasoconstriction (to increase resistance)
increase stroke volume and HR (to increase CO)
Why does the body think there is a sudden drop in BP when you stand up when you have orthostatic hypertension?
arterial pressure increases when laying down (since blood is not going to lower body) which tricks kidneys into thinking blood volume is higher than it actually is so when you stand up its seen as a sudden drop in pressure
What is autoregulation?
ability of some tissues/capillaries to regulate their own blood flow
What are 6 tissues that can autoregualte?
renal
cerebral
cornoary
skeletal
muscles
pulmonary
What is active hyperemia?
response to physical activity that causes blood to flow to an organ/tissue to meet the increased need for oxygen and nutrients
What is an example of active hyperemia?
working out; muscles are supplies with more O2 and blood
During active hyperemia, what happens to…
arterioles dilate/constrict
resistance increases/decreases
blood flow increases/decreases
arterioles dilate
resistance decreases
blood flow increases
What is reactive hyperemia?
temporary increase in blood flow to an organ after a brief period of ischemia, or when blood flow is temporarily restricted
What is an example of reactive hyperemia?
wrapping rubber band around a finger
In auto regulation, if more blood flow is needed locally the local arterioles will constrict/dilate and the resistance will increase/decrease?
local arterioles dilate
decreased resistance
What are 4 local vasodilators?
increased CO2
decreased O2
increased H+
increased K+
What is the most important local vasodilator?
CO2
When O2 in the coronary circulation decreases, coronary dilates/constricts and CO2 rises/drops?
coronary dilates
CO2 rises
In the coronary circulation, when vasodilation is not enough, ________ is released to cause local hyperemia?
adenosine
Do vasoactivitors have an affect on cerebral circulation? Why or why not?
no effect
cannot cross BBB
What 3 ways is heart rate controlled during exercise via neural control?
- proprioreceptors
- chemoreceptors
- baroreceptors
Cardiovascular adjustments during exercise are regulated by a combination of _______ and _______ factors
neural
local
How do proprioreceptors regulate HR during exercise?
pick up movement in muscles/joints and will signal to increase HR and stroke volume
How do chemoreceptors regulate HR during exercise?
pick up on chances in pH (lactate) and will signal to increase HR and stroke volume
During exercise, systemic vaso______ occurs except in the heart/lungs/muscles which is caused by local vaso________ overriding ___________ nervous system response
vasodilation
local vasodilators
sympathetic NS response
Is the cerebral circulation ever affected by exercise?
no
During exercise, skin has a biphasic response, why?
blood flow is initially restricted to the skin but as body temperature rises blood flow increases in skin so you can sweat
During exercise, the total peripheral resistance increases/decreases?
decreases
(less resistance in muscles so overall resistance decreases)
What is a local factor that happens during exercise?
active hyperemia (muscles)
During exercise, neural control is basically turning on the _________ nervous system
sympathetic
During exercise, local control is basically vasodilation/constriction of blood flow to muscles?
vasodilation
what 2 arteries does the blood flow to the brain come from?
basilar
carotid
The basilar and carotid artery merge in brain to for the…
circle of Willis
What are 3 methods of cerebral auto-regulation of circualtion?
- myogenic autoreg
- metabolic autoreg
- neurogenic autoreg
What is myogenic auto regulation of cerebral circulation?
arteries dilate/constrict based on changes in BP and inter-cranial pressure
What is metabolic auto regulation of cerebral circulation?
response to changes in CO2, pH or O2 levels
What is neurogenic auto regulation of cerebral circulation?
sympathetic NS will constrict large vessels to prevents high pressure reaching small vessels to prevent stroke
If CO2 levels in the blood decrease…
vasodilation/constriction
increased/decreased cerebral blood flow
good/bad cerebral circulation
vasoconstriction
decreased cerebral blood flow
bad cerebral circulation
** this is what happens when you hyperventilate
When pH is low..
vasodilation/constriction
increased/decreased cerebral blood flow
vasodilation
increased cerebral blood flow
** during exercise pH drops
What can easily pass the blood brain barrier?
gases and lipid soluble molecules (steroids)
What cannot pass blood brain barrier at all?
proteins, Ab, large molecules
What can sometimes pass the blood brain barrier?
ions and glucose
Is renin and aldosterone secreted when pressure are high or low?
low
Where in renin secreted from?
juxtaglomerular cells of the kidney
Renin is responsible for the increase/decrease of Na+ retention which leads to increase/decrease of blood volume thus increasing/decreasing blood pressure.
increasing Na+ retention
increase blood volume
increase BP
Is renin and aldosterone secreted when blood volume are high or low?
low
What enzyme cleaves angiotensin I into angiotensin II?
ACE
Where is ACE located?
lungs
