circualation

Regulation of Circulation”

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Regulation of circulation ensures tissues get the right amount of blood based on their needs.

1. Local Regulation (Intrinsic)

• Controlled within the tissue itself

• Adjusts blood flow according to metabolic activity

Mechanisms:

• Metabolic control:
  ↑ CO₂, ↓ O₂, ↑ H⁺ → vasodilation

• Myogenic response:
  Blood vessels constrict when stretched (helps maintain constant flow)

• Endothelial factors:

  • Nitric oxide → vasodilation

  • Endothelin → vasoconstriction

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2. Systemic Regulation (Extrinsic)A. Neural control

• Sympathetic nervous system:

  • Vasoconstriction (most vessels)

  • ↑ heart rate and contractility

• Parasympathetic:

  • Limited effect (mainly heart)

B. Hormonal control

• Adrenaline → ↑ cardiac output, vasodilation (muscle)

• Noradrenaline → vasoconstriction

• Angiotensin II → strong vasoconstrictor

• Vasopressin → vasoconstriction + water retention

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🔄 Autoregulation of Blood Flow

Autoregulation = ability of tissues to maintain constant blood flow despite changes in blood pressure.

Key Features:

• Works best in organs like:

  • Brain

  • Kidneys

  • Heart

Mechanisms:

1. Myogenic mechanism

   • Increased pressure → vessel constricts

   • Decreased pressure → vessel dilates

2. Metabolic mechanism

   • Active tissues release vasodilators (CO₂, adenosine)

👉 Example:
During exercise, skeletal muscles receive more blood due to local vasodilation.

Circulatory Shock

Shock = inadequate tissue perfusion, leading to cellular hypoxia and organ failure.

Stages of Shock:

1. Compensated (non-progressive)

   • Body maintains BP via reflexes

2. Progressive

   • Worsening perfusion and metabolic acidosis

3. Irreversible

   • Organ damage → death

Types of Shock

🚨 1. Hypovolemic Shock

• Cause: Loss of blood or fluids

• Examples:

  • Hemorrhage

  • Severe dehydration

👉 ↓ blood volume → ↓ cardiac output

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2. Cardiogenic Shock

• Cause: Heart failure to pump

Examples:

• Myocardial infarction

• Severe arrhythmias

👉 ↓ cardiac output despite normal volume

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3. Distributive Shock (vasodilation problem)A. Septic shock

• Due to severe infection

• Bacterial toxins → vasodilation

B. Anaphylactic shock

• Severe allergic reaction

• Histamine release → vasodilation + permeability

C. Neurogenic shock

• Loss of sympathetic tone (e.g., spinal injury)

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4. Obstructive Shock

• Physical obstruction of circulation

Examples:

• Pulmonary embolism

• Cardiac tamponade

What are the two main types of circulation regulation?

Local (intrinsic) and systemic (extrinsic)

What is local regulation?

A: Control of blood flow by the tissue itself based on metabolic needs

Name local regulatory mechanisms

Metabolic, myogenic, endothelial

.What causes vasodilation in metabolic control?.

↑ CO₂, ↑ H⁺, ↓ O₂

What is the myogenic mechanism?

Vessel constricts when stretched, dilates when pressure falls

Role of endothelium in circulation?

Releases vasodilators (NO) and vasoconstrictors (endothelin)

-What controls systemic regulation?

A: Nervous system and hormones

Effect of sympathetic stimulation?

.A: Vasoconstriction, ↑ heart rate, ↑ contractility

Name key hormones in circulation regulation

A: Adrenaline, Noradrenaline, Angiotensin II, Vasopressin

What is autoregulation?

A: Maintenance of constant blood flow despite BP changes

Q: Organs with strong autoregulation?

A: Brain, heart, kidneys

: Mechanisms of autoregulation?

Q
A: Myogenic and metabolic

:Q: Myogenic response to increased pressure?

“A: Vasoconstriction I

Metabolic response to high activity?

Vasodilation

Circulatory Shock – Flashcards

Q: Define shock

Inadequate tissue perfusion leading to hypoxia

.Stages of shock

.
A: Compensated, progressive, irreversible

.What happens in compensated shock?

A: Body maintains BP via reflexes

What characterizes progressive shock?

A: Worsening perfusion and acidosis

Q: What defines irreversible shock?

.A: Organ failure and death

Q: What is hypovolemic shock?

A: Shock due to loss of blood/fluid

Q: Causes of hypovolemic shock

A: Hemorrhage, dehydration

Q: What is cardiogenic shock?

A: Failure of heart to pump effectively

Q: Causes of cardiogenic shock

‘A: MI, arrhythmias

.Q: What is distributive shock?
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A: Shock due to widespread vasodilation

Q: Types of distributive shock

A: Septic, anaphylactic, neurogenic.

‘Q: What is septic shock?

A: Infection causing vasodilation via toxins

Q: What is anaphylactic shock?

A: Severe allergic reaction → histamine release

What is neurogenic shock?

A: Loss of sympathetic tone

-What is obstructive shock?

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A: Pulmonary embolism, cardiac tamponade

Q: Causes of obstructive shock

A: Pulmonary embolism, cardiac tamponade

4 types of shock?

Hypovolemic, cardiogenic, distributive, obstructive

.Main problem in shock?

A: ↓ Tissue perfusion

Left heart failure

Left ventricle failure

↓

↓ Cardiac output

↓

↑ Left atrial pressure

↓

↑ Pulmonary venous pressure

↓

Pulmonary congestion

↓

Pulmonary edema

↓

Dyspnea (breathlessness)

Right heart failure

Right ventricle failure

↓

↑ Right atrial pressure

↓

↑ Systemic venous pressure

↓

Venous congestion

↓

Peripheral edema

+ Hepatomegaly

+ Ascites

Howchart

Left Heart Failure

↓

Pulmonary congestion

↓

Pulmonary hypertension

↓

Right Heart Failure

↓

Congestive Heart Failure

Feature	Left Heart Failure	Right Heart Failure
Definition	Failure of left ventricle to pump blood into systemic circulation	Failure of right ventricle to pump blood into pulmonary circulation
Main effect	Blood backs up into lungs	Blood backs up into systemic veins
Common causes	Hypertension, IHD, aortic valve disease	Left heart failure (most common), lung disease
Pulmonary effect	Pulmonary congestion, edema	Usually no pulmonary congestion
Systemic effect	↓ organ perfusion	Venous congestion
Breathlessness	Severe (early symptom)	Mild/late
Edema	Rare (early)	Peripheral edema (legs)
JVP	Normal or slightly ↑	Markedly ↑
Liver	Usually normal	Congested hepatomegaly
Ascites	Rare	Common
Urine output	↓ (due to ↓ renal perfusion)	↓ (venous congestion)

1. Most common cause of right heart failure?

A. Pulmonary embolism
B. Left heart failure
C. Hypertension
D. Anemia

👉

B

2. Pulmonary edema occurs in:

A. Right heart failure
B. Left heart failure
C. Both equally
D. None

B

Raised JVP is seen in:

A. Left HF
B. Right HF
C. Both
D. None

B

Ascites is commonly seen in:

A. Left HF
B. Right HF
C. Early shock
D. MI

B

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5. Dyspnea is mainly due to:

A. Systemic congestion
B. Pulmonary congestion
C. Liver enlargement
D. Edema

B