The cardiovascular system Flashcards
Role of the Peripheral Circulation
- Carry ….
- Exchange ……, ….. ……… and ……
Transport of ….., components of the immune system, molecules required for….., enzymes, nutrients, gases, waste products, etc
Regulate …… …………
Direct ……… ……..
Carry blood
Exchange nutrients, waste products, and gases
Transport of hormones, components of the immune system, molecules required for coagulation, enzymes, nutrients, gases, waste products, etc.
Regulate blood pressure
Direct blood flow
Blood pressure
The ….. exerted by the ….. volume of ….. on the walls of the arteries, the ….. and the …. of the heart
Normal blood pressure
- Aorta …..mmHg during systole
- .. mmHg during diastole
The pressure exerted by the circulating volume of blood on the walls of the arteries, the veins and the chambers of the heart Normal blood pressure Aorta 120 mmHg during systole 70 mmHg during diastole
Factors affecting blood pressure
Cardiac output (CO) - Calculated by stroke ...... x ......... rate
Blood volume
- Blood pressure increases linearly with an increase of ….. …….
Peripheral resistance (PR)
- This refers to the ….. of …… between the bood and the walls of the blood vessels
- Pr increases as blood ….. increases
- Pr increases as blood …… …….. decreases
Cardiac output (CO)
Calculated by stroke volume x heart rate
Blood pressure rises linearly with CO
Blood volume
Blood pressure increases linearly with an increase in blood volume
Peripheral resistance (PR)
This refers to the forces of friction between the blood and the walls of the blood vessels
PR increases as blood viscosity increases
PR increases as blood vessel diameter decreases
The possible range of cardiovascular adjustments
- Changes to cardiac output
- changes to peripheral resistance
- changes to capacitance
Changes to cardiac output
Changes to peripheral resistance
Changes to capacitance
Reasons for adjustments
- To increase blood …./….. to active …..
- To increase or decrease heat loss from the …..
- To maintain blood flow to the ….. and ….. e,g, in situations of blood loss
- To maintain blood flow to
v. …………… …… at the expense of all other areas (as seen in as severe challenge)
To increase blood flow/supply to active tissue
To increase or decrease heat loss from the body
To maintain blood flow to the heart and brain e.g. in situations of blood loss
To maintain blood flow to vital organs at the expense of all other areas (as seen in a severe challenge)
Changes to cardiac output
This is a function of heart rate and stroke volume
rate is controlled primarily by cardiac ………..
stroke volume is also determined mainly by c…… ……….
This is a function of heart rate and stroke volume
Rate is controlled primarily by cardiac innervation
Stroke volume is also determined mainly by cardiac innervation
Changes to peripheral resistance
Calibre of the arterioles (mainly) is adjusted in part by …………………. (intrinsic properties of smooth muscle)
The calibre is increased in active tissue by locally produced vasodilators e.g. rise in lactate
Calibre is affected by substances secreted by the ………….. e.g. nitric oxide (a powerful vasodilator)
Calibre is regulated by circulating ……………… substances (systemic circulation) e.g. natriuretic hormones and catecholamines
Calibre is affected by ………………. nerves (neural mechanisms)
Calibre of the arterioles (mainly) is adjusted in part by autoregulation (intrinsic properties of smooth muscle)
The calibre is increased in active tissues by locally produced vasodilators e.g. rise in lactate
Calibre is affected by substances secreted by the endothelium e.g. nitric oxide (a powerful vasodilator)
Calibre is regulated by circulating vasoactive substances (systemic circulation) e.g. natriuretic hormones and catecholamines
Calibre is affected by vasomotor nerves (neural mechanisms)
Changes to Capacitance
( the blood reservoir)
Venoconstriction and venodilation is controlled by ………. ………… e.g. cartoid sinus
Specific reservoirs include the …… (100 mL), the …… (200+) mL), the larger ………l veins (300 mL) and the venous ……. beneath the skin (200 mL)
The heart and lungs must also be considered blood reservoirs i.e. Hearts (50-100mL) and lungs (100-200mL)
Venoconstriction and venodilation is controlled by pressure reflexes e.g. carotid sinus
Specific blood reservoirs include the spleen (100 mL), the liver (200+ mL), the larger abdominal veins (300 mL) and the venous plexus beneath the skin (200 mL)
The heart and lungs must also be considered blood reservoirs i.e. Heart (50-100 mL) and lungs (100-200 mL)
Cardiovascular adjustments in Extreme envionments
Cardiovascular adjustments to … and ….. temperatures, ……changes, ….. and ……. G forces, zero…., alti….. and di…….
Cardiovascular adjustments to low and high temperatures, postural changes, positive and negative G forces, zero gravity, altitude and diving
Response to Low Temperatures
(a) Cutaneous vasoconstriction
- The primary response is c………….. vas…………..
- …..blood flow and convectional heat losses from the surface of the …..
- Vasoconstriction cooling results in periods of …………… thought to be a phenomenon that serves to …… ……. ……..
It results primarily from a direct cold-induced paralysis of the ………. blood vessels which lose their ability to respond to …………. at low temperatures
Cutaneous vasoconstriction
The primary response is cutaneous vasoconstriction
↓ blood flow and convectional heat losses from the surface of the skin
Vasoconstriction is the result of sympathetic activity to the blood vessels of the skin
Prolonged cooling results in periods of vasodilation thought to be a phenomenon that serves to prevent tissue damage
It results primarily from a direct cold-induced paralysis of the peripheral blood vessels which lose their ability to respond to noradrenalin at low temperatures
Response to Low Temperatures
(b) Vascular acclimatisation and adaption
Some indication for local acclimatisation to cold in the ………, in that the initial ……. response to cold is less …. and the onset of subsequent ……. more rapid than in …… subjects
Eskimos also exhibit a …….. than normal rate of ………. blood flow to their extremities when expose to the c……
Immersion of the face in cold water usually causes reflex……… and vasoconstriction of the hands (this response is reduced or absent in Eskimos)
b) Vascular acclimatisation and adaptation
Some indication for local acclimatisation to cold in the extremities e.g. fingers, in that the initial vasoconstrictor response to cold is less severe and the onset of subsequent vasodilation more rapid than in unacclimatised subjects
Eskimos also exhibit a higher than normal rate of peripheral blood flow to their extremities when expose to the cold
Immersion of the face in cold water usually causes a reflex bradycardia and vasoconstriction of the hands (this response is reduced or absent in Eskimos)
Response to low Temperatures
(c) Hypothermia
- At core temperature below 28*c cardiac ………. occur and ventricular ………. is often responsible for fatalities at these temperatures
Prolonged cooling of the feet and legs in cold water results in peripheral …….. - arises as a consequence of reduced blood flow
Recovery from hypothermia can be rapid and complete - but does depend on a high level of ……………….. ……..
Certain groups are at greater risk e,g, neonates do not have fully developed temp. regulating mechanisms; the elderly have impaired ……………. control
Hypothermia
At core temperatures below 28oC cardiac arrhythmias occur and ventricular fibrillation is often responsible for fatalities at these temperatures
Prolonged cooling of the feet and legs in cold water results in peripheral neuropathy – arises as a consequence of reduced blood flow
Recovery from hypothermia can be rapid and complete – but does depend on a high level of physical fitness
Certain groups are at greater risk e.g. neonates do not have fully developed temp. regulating mechanisms; the elderly have impaired hypothalamic control
Response to High Temperatures
(a) Cutaneous vasodilation
- Rapid cutaneous and vasodialtion occurs as ambient temperature rises
- This transfers heat from deep to superficial body tissues
- If …………………responses are not effective in the heat then body temperature core starts to rise
(B) Cardiac Output
This will be directly influenced by temperature i.e the …….. node will fire more rapidly as temp rises
Despite an increase cardiac output, blood ……… is not usually affected because of the fall in peripheral resistance (caused by vasodilation)
) Cutaneous vasodilation
Rapid cutaneous vasodilation occurs as ambient temperature rises
This transfers heat from deep to superficial body tissues
If thermoregulatory responses are not effective in the heat then body temperature (core) starts to rise
(b) Cardiac Output
This will be directly influenced by temperature i.e. the sinoatrial node will fire more rapidly as temp.↑
Despite an ↑ cardiac output, blood pressure is not usually affected because of the fall in peripheral resistance (caused by vasodilation)
Response to High Temperatures
C) Acclimatisation
- If core temperature is normalised by ……., the heart rate will fall
- Cardiac output will then return …………
d) heat collapse
- Characterised by fatigue, dizziness and a temporary loss of consciousness in the heat
- Caused by a ….. of blood in dilated b…… vessels of skeletal muscles and the skin in the lower limbs
- Fainting causes and increase in venous
c) acclimatisation
If core temperature is normalised by sweating, the heart rate will fall
Cardiac output will then return to normal
(d) heat collapse
Characterised by fatigue, dizziness and a temporary loss of consciousness in the heat
Caused by a pooling of blood in dilated blood vessels of skeletal muscles and the skin in the lower limbs
Fainting causes an increase in venous return and the re-establishment of cerebral circulation
Response to Postural changes
Sudden standing
- In a standing position …… causes blood to pool in the ……… capacitance vessels of the lower extremities and fluid begins to accumulate in the interstitial spaces (subject not moving)
This due to increased …….. pressure in the capillaries
Cardiac stroke volume is decreased by up to 40%
Eventually decrease cerebral blood flow would lead to loss of consciousness
A drop in blood pressure in the carotid ….. and aortic arch triggers an increase in heart rate
Arterioles constrict in response to Increase levels of re…and aldo……..
In some individual, sudden standing causes a fall in blood pressure
It also occurs in disease where the …….. nervous system is compromised e,g, diabetes or in primary autonomic insufficiency diseases
In a standing position gravity causes blood to pool in the venous capacitance vessels of the lower extremities and fluid begins to accumulate in the interstitial spaces (subject not moving)
This is due to increased hydrostatic pressure in the capillaries
Cardiac stroke volume is decreased by up to 40%
Eventually ↓ cerebral blood flow would lead to loss of consciousness
A drop in blood pressure in the carotid sinus and aortic arch triggers an increase in heart rate
Arterioles constrict in response to ↑ levels of renin and aldosterone
In some individuals, sudden standing causes a fall in blood pressure
It also occurs in diseases where the sympathetic nervous system is compromised e.g. diabetes or in primary autonomic insufficiency diseases
