Circulation: Systemic Regulation

Front 1

Neural control

Back 1

- BF normally controlled locally
- controls global fx:
1. resdistribution of the BF to different areas of the whole body
2. adjustment of CO
3. rapid control of arterial BP

Front 2

sympathetic nerve

Back 2

-Norepi
1. alpha 1 and 2: vasoconstriction: all organs, arterioles, abdominal organs, vv
2. beta 1: increases activity: heart, all cardiac mm cells

Front 3

circulating cathecholamines

Back 3

- Norepi, Epi
- beta 2
- vasodilation:
1. heart, coronary, arterioles
2. skeletal mm, arterioles

Front 4

parasympathetic nerve

Back 4

-acteylcholine
1. M2: decreases HR: heart, SA, AV, atrial cells
2. M3: vasodilation: heart, coronary, arterioles

Front 5

humoral stimulation of vascular tone

Back 5

1. circulating Epi/ Norepi:
2. beta 2 receptors
3. vasodilation
- can overpower neural alpha 1 stimulation, resulting in vasodilation in the coronary circulation and skeletal mm

Front 6

neural stimulation of vascular tone

Back 6

1. Norepi from the sympathetic n
2. alpha 1 receptors
3. vasoconstriction

Front 7

neural and humoral control of the vasomotor tone

Back 7

1. normal: vasomotor tone: sympathetic nerve maintains level via vasoconstrictor center
2. spinal anesthesia: blocks sympathatic nerve resulting in a loss of vasomotor tone (=innervated vessels dilate)
3. injection of Norepi: vasoconstriction and BP increase as long as Norepi is present

Front 8

arterial baroreceptor reflex gen

Back 8

1. receptors: respond to P changes by sensing stretch or distortion of the vessel wall
2. location: carotid aa and aortic arch
3. nerves:
-carotid sinus: glossopharyngeal n
- aortic arch: vagus n

Front 9

atrial volume receptor reflex gen

Back 9

1. respond to volume changes by sensing stretch or distortion of the atrial wall
2. location: LA and RA walls
3. nerve: vagus n

Front 10

arterial baroreceptor reflex different conditions

Back 10

1. normally keeps arterial mean P within small range
2. long term adjustment: if BP rises or falls for longer period of time, set point is shifted and P is regulated
close to this new point
3. inhibiting refex: wide variations in arterial BP because there's no long term adjustment

Front 11

arterial baroreceptor reflex: standing up quickly

Back 11

- causes drop of BP because of blood distribution change
- baroreceptor reflex responds almost immediately, returning BP to normal

Front 12

arterial baroreceptor reflex details

Back 12

- afferent fibers of PS nerve
- receptors in carotid and aortic arch respond to stretch of wall
- high speed response: mirrors P changes during each cardiac cycle ( beat by beat information)
- frequency of APs proportional to arterial BP
- slow adaptation (days to weeks) to long term changes in BP

Front 13

immediate effects of atrial volume receptor reflex

Back 13

1. use of reserve volumes of venous (volume vessels)
2. decrease of systemic volume
3. vasoconstriction, increase of cardiac activity

Front 14

long term effects of atrial volume receptor reflex

Back 14

securing resources and replacing losses:
-reduced Na excretion
- reduced urine production
- increased thirst /water intake

Front 15

atrial volume receptor reflex details

Back 15

- afferent fibers of PS nerve
- receptors in atrium respond to stretch of the atrial wall (more volume= more stretch)
- high speed response: mirrors P changes during each cardiac cycle (beat by beat info)
- frequency of APs proportional to filling of atria: low volume =low P= low frequency
- immediate adaptation via S and PS activity (like baroreflex)
- long term adjustment: kidneys save resources, water intake

Front 16

response to decrease in blood volume

Back 16

1. blood is shifted from venous to arterial side in order to maintain required arterial BP
2. decrease in atrial P: atrial volume receptors respond
3. arterial side: BP maintained as long as possible
4. if systemic BP cannot be maintained: arterial baroreceptors respond

Front 17

defense reaction

Back 17

-conscious perceptions and emotional reactions influence the nervous and humoral control of whole circulation

Front 18

defense reaction example

Back 18

-activates S and reduces PS activity:
1. increased cardiac: increased BP, vasoconstriction, pale skin, mydriasis
2. hormones: ADH, angiotensin II, corticotropin
3. central control: overpowers non-central control mechanisms
- baroreceptor reflex set to elevated level

Front 19

muscle pump and exercise

Back 19

1. each m contraction increases BP in vv
2. proximal valves open and blood is pushed towards the heart
3. relaxation: proximal vv close, preventing reflux
4. distal valve opens and v refills

Front 20

respiratory pump and exercise

Back 20

1. inspiration:
a. decreases P in thorax, distending the central vv and pulling blood from abdomen
b. lung expands and better fills with blood
2. expiration:
a. increases P in thorax and moves blood to the heart
b. supports BF from lungs to left heart

Front 21

CO and exercise

Back 21

- CO can increase 4-5x resting level (reserve capacity of the heart)
- normal: max exercise limited by CO, not respiratory system or metabolism of skeletal mm
- heart failure: CO increase is limited so patients exhibit exercise intolerance