week 4: Flashcards by daisy barnwell

what is exercise a challenge to

homeostasis

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muscle blood flow and exercise intensity relationship

directly proportional until saturation point has been hit

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reasons for saturation point

opened up as many blood vessels as you can
can’t increase exercise intensity anymore

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cardiac output= (litres per minute)

heart rate x stroke volume

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stroke volume

volume ejected by ventricle per beat

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bradycardic

less than 60bpm

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tachycardic

over 90bpm

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fox’s formula

max heart rate = 220-age

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more recent max heart rate formula

211- (0.64) x age

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relationship between heart rate and the amount of work being performed

very positive correlation
r=0.99

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peak heart rate often hit when

peak oxygen transport hit (V02 max)

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Karvonen heart rate reserve method

max hr- resting hr = HRR
moderate = 60-70% HRR

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how much can cardiac output increase by during exercise

normally 4-6 fold
( from 4-8 litres per min- 20-25)

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stroke volume increase during exericse

30% increase compared to at rest
80ml per beat - 120/140ml per beat

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heart rate increase during exercise

2-3 fold
60 bpm- 180bpm

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what does exercise anticipation activate

sympathetic neurons in hypothalamus

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what nerve switches off during exercise and what nerve becomes activated

vagal (parasympathetic) nerves switches off
sympathetic nerve becomes activated

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what does sympathetic nerve becoming activated cause

SA nodes intrinsic firing frequency accelerates
faster heart rate
gets stronger until peak HR reached

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what does sympathetic nervous stimulation of adrenal medulla release

epinephrine

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effects of epinephrine

delivered by blood
accelerates SA nod discharge
dilates coronary vessels
increases myocardial metabolism

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what do efferent sympathetic fibers increase

heart rate
myocardial contractility
dilate coronary arteries

changes in muscle during exercise

elevated temp
decreased local O2
elevated local CO2
falling local pH
increasing local adenosine
increased nitric oxide
elevated local K+

what do all of these local factors do

open up blood vessels

why does pH fall

H+ is accumulated as a product of elevated metabolism due to producing and breaking lots of ATP
more acidotic
relaxes blood vessel walls

why does adenosine increase

lots of ATP breakdown releases adenosine

effect of nitric oxide

smooth muscle in blood vessels relax

why does blood prefer to go to places which are more metabolically active

blood vessels a these places have been triggered to relax

effect of adrenaline on alpha receptors

vasoconstriction

exercise increases adrenaline however more blood flows to muscles needed as adrenaline goes up it restricts blood flow competition between metabolically active tissue and adrenaline

what happens when muscle is activated by a somatomotor nerve

releases vasodilator stimuli

what does active sympathetic nerve cause

vasoconstrictor stimuli

why is good blood flow important

ensure active muscle is getting oxygen and nutrients

sympatholytic effect

vasodilator stimuli overpowers sympathetic input blood will get to where required where muscle isn't active, blood flow shut down to these areas (diversion of blood to where its required)

group III and group IV nerves embedded in skeletal muscles

directly responsive to temp, muscle tension, acidosis send signal back to medulla (to say how well muscles are coping?) perception of effort

effect of signals from group III and group IV nerves

increase sympathetic output to encourage greater diversion shutting off splanchnic blood vessels diverting blood away from guts/ kidneys/ liver enhanced capacity to supply muscle blood

syncope

fainting/ passing out

affect of higher blood pressure during exercise

bigger pressure gradient between arteriole side and venule side greater rate of flow maintained through skeletal muscle

effect of exercise on diastolic and systolic blood pressure

systolic: increases diastolic: remains same

why does diastolic pressure stay same

if it was too fall, it would mean arteries were relaxing during exercise if it was to rise, not beneficial as heart would be doing a lot more work

VO2 max=

cardiac output max x a-v O2 difference

why is VO2 max one one legged exercise 75%-80% of two legged- exercise

higher blood flow can be achieved to activate muscles in one-legged exercise if both legs were dilated to the same extent as in one-legged exercise, blood pressure would fall

what is responsible for making sure pressure goes up and demnads are met

ensuring enough blood goes into heart to maintain good stroke volume must also ensure not to elevate the resistance to which the heart is working, if diastolic pressure increases it would oppose blood flow out of heart increase contractility of heart to ensure as much blood as possible leaves per beat

how to ensure heart is filling with blood to allow efficient stroke volume during exercise

increase blood volume increase return

how to increase blood volume

contract spleen constrict splanchnic supply constrict capacitance veins

how to increase return

constrict veins constrict supply to other tissues

muscle pump

deep veins sit within skeletal muscle when skeletal muscles activated they contract, pressure around skeletal muscle increases, skeletal muscles push on veins reducing their volume and elevating the pressure within the veins, helps pump blood back towrds heart

what is muscle pump facilitated by

valves within the large veins prevents backflow blood can only go towards heart

what does negative pressure in thorax increase

venous return

what creates negative pressure in thorax

breathing

exercise presser reflex

baroreceptor input inhibited allowing bp to increase