C3.11 - Circulation and Homeostasis

Homeostasis

• homeostasis: state of internal stability maintained by body
  • normal pH state of blood
  • goal of circulatory system

Hypertension

• hypertension: high blood pressure
• Occurs when BP > 140/90 for ext. period of time
• Increases risk of heart disease
• Diets high in salt and cholesterol increase BP
• BP increases with:
  • age
  • lack of exercise
  • obesity
  • certain ethnicities
    • African
    • Aboriginal
    • South Asian
  • stress
  • excess alcohol
  • smoking
• High cholesterol diets may lead to arteriosclerosis
• arteriosclerosis: disease where plaques are deposited in arteries
  • leads to obstructions
  • ⚠ possible heart attacks
  • see more in Disorders

Blood Pressure (BP)

Device to measure BP

• BP and heart rate increase from increased O₂ demand
• systolic pressure: highest pressure resulting from contraction of l. ventricle
• diastolic pressure: lowest pressure before another ventricular contraction
• sphygmomanometer: pressure cuff used to measure blood pressure
• average: 120/80 mm Hg (120 systolic / 80 diastolic)

Lymphatic System

• Vascular transport system incl. spleen
• Network of glands and valved vessels
• Contains lymph
  • usually clear, colourless, oily fluid
• Helps maintain fluid balance in mammals
• Collects blood plasma that has leaked out of capillaries
• interstitial fluid: leaked plasma
• Lymph returned to blood stream through ducts opening onto l. and r. subclavian veins
• Flow of lymph dictated by movement of gut and skeletal muscle
• Involved in immune response
• Lymphocytes produced in lymph nodes
• Lymph glands swell when body fights infection

Lymphatic System — PART II

• ~3-4 L of fluid / day leave blood to surround your cells
• lymphatic system: organ system that collects fluid leaving capillaries
  • screens them for microorganisms
  • then returns them to the circ. system
• lymph: fluid leaked out of circ. system, collected by lymphatic vessels
  • clear, watery fluid made up of
    • protein molecules
    • salt
    • gluocose
    • others
• Lymph collects in system of lymph vessels
  • Have valves to prevent lymph from flowing back toward capillaries
  • Muscle contractions + vessel squeezing + valves → help move lymph
  • Eventually drains into circ. system near heart
• spleen: organ that helps remove old / damaged blood cells, stores platelets and
  • helps control amount of blood and blood cells in body
• Lymph vessels alongside small intest. pick up fats and fat-soluble vits. and transports to blood
• Helps provide immunity
• thymus: organ where WBCs mature
• lymph node: small, bean-shaped enlargements that filter out harmful organisms and abnormal cells

Temperature Regulation

• homeotherm: body temp. does not fluctuate
  • i.e. lion
• poikilotherm: body temp. fluctuates according to environ. factors
  • i.e. tortoise
• Body temp. of 37.5 °C maintained via behavioural and physiological mechanisms
  • Ex. behavioural
    • sitting in shade
    • putting on clothing
  • Ex. physiological
    • Heat loss from skin surface regulated by…
      • vasoconstriction; or
      • vasodilation of blood vessels
    • countercurrent heat exchange system in arms and legs

Health of Circulatory System

Plaque

plaque: patchwork of cholesterol, calcium, and fat deposits that stick to interior vessel walls

Dangers

• atherosclerosis: narrowing of arteries resulting from plaque buildup
  • pathway narrows → BP increases
  • angina pectoris: chest pains felt from partial blockages
  • occurs when deposits on artery wall harden
  • weakens arterial elasticity
• heart attack: stoppage / severe slowdown of blood supply to heart tissue
  • majority cause: atherosclerosis
• sudden cardiac arrest: heart suddenly stops functioning
  • most common cause: coronary heart disease

Disorders

• arrhythmia: heart beats irregularly (too slow, too quick)
• hypertension
  • above
• heart failure: condition where heart cannot pump blood efficiently
  • because it can’t fill with enough blood
  • or send blood w/ enough force
• aneurysm: bulge in wall of artery
• stroke: blood clot forming in artery going to brain

Choices Helping Cardiovascular Health

• Foods high in fiber
• Low in salt and cholesterol
• cholesterol: fat part of cell membranes used to synthesize hormones, bile, and vit. D
  • made by liver
• high-density lipoprotein (HDL)
  • “good cholesterol”
  • removes excess cholesterol from tissues and arteries
• low-density lipoprotein (LDL)
  • “bad cholesterol”
  • becomes part of plaque in arteries
• Maintain healthy weight
• Exercise regularly
• Avoid smoking and inhaling smoke
• Regular health check ups