Wk 4 - Intro to Physiology Flashcards
What is physiology?
The study of how things work in a living organism
Define homeostasis
Holds the body at a constant level/magnitude even throughout external and internal disturbances
What is the function of homeostasis in the body
- Mechanisms to regulate control variables that are key to being kept “normalized” for homeostasis
- Stay in control using negative feedback loops – maintains dynamic constancy in normal functioning range
Overview of the respiratory system
- Take in O2 for respiration and release CO2
- Monitor partial pressures of gases and modify through ventilation
Overview of the urinary system
- Regulate extracellular fluid balance (and BP)
- Regulate blood plasma composition (pH, electrolytes, water, salts)
- Osmoreceptors in hypothalamus
… Secrete ADH
Increased ADH? Increase water reabsorption
Overview of gastrointestinal system
- Digest, absorb, secrete: enzymes, fluids, nutrients
- Motility/speed through system
- Regulation: parasympathetic from CNS (acetylcholine) –> comes from long reflexes
- Short reflexes from cephalic brain
Overview of reproductive system
- Produce gametes/support development of fetus and infant (lactation)
- Hormone production and control (mainly from hypothalamus – LH hormone)
Overview of endocrine system
- Regulation/coordination of growth, metabolism, reproduction, BP, electrolyte balances
Mechanistic effect
- Cause and effect
- Starts at beginning and looks at how events happen
Ex: body temperature drops below normal and so a reflex pathway causes involuntary oscillating skeletal muscle contractions to produce heat
Teleological effect
- Starts at the end
- Looks at why things happen and explains the purpose of an action
Ex: Shivering elevates a low body temperature
Body temperature negative feedback process
Sweating
- Dilation of blood vessels helps radiate heat
- Fluids become more concentrated
- Concentrated fluids detected by osmo-receptors in hypothalamus – leads to increase in thirst
- Drink more water!
Shivering
- Muscles contracting – requires energy – told to do so by the hypothalamus
- Heat is released from skeletal muscles
- Blood vessels constrict to make them go deeper into tissues and not release a lot of heat
Overview of cardiovascular system (example from powerpoint)
Flow = Pressure/Resistance
Blood pressure = cardiac output * total peripheral resistance
BP = CO * TPR
What is controlled variable? – BP!
How is cardiac flow determined?
CO = Heart rate * Stroke volume
What is the sensor? – Baroreceptors!
What transmits the efferent signal?
- Vasodilation
- Decrease HR (Decreases CO too)
- Decrease stroke volume (decreases CO too)
- NERVES: sympathetic response (norepinephrine)
What is the effect of an increase in blood pressure??
- Decrease in resistance and cardiac output
What’s the equation for controlling blood flow through a blood vessel?
FLOW = PRESSURE/RESISTANCE!!
What’s the primary controlled variable to make sure that the CV system meets its homeostatic role?
Blood pressure!
BP = CO * TPR
What are the 2 factors that control mean arterial pressure?
CARDIAC OUTPUT
TOTAL PERIPHERAL RESISTANCE
Increase either one and cause increase in pressure
What are the 2 factors that influence cardiac output??
Pressure difference
Resistance
Where is the greatest effect on the total peripheral resistance??
Artery, arteriole, capillary, venous areas
Describe negative feedback role of arterial baroreceptors that regulate arterial pressure
Ex: stimulus causes increase in blood vessels
- Baroreceptors stimulate cardioinhibitory center
- Cardioinhibitory center INHIBITS vasomotor center
- Vasomotor center DECREASES sympathetic impulses: HR, contractility, CO, resistance
