Homeostasis and Control Systems Flashcards
What is homeostasis?
The maintenance of a relatively constant or stable internal environment
How is the intracellular environment controlled ?
- Membrane transporters
- Protein expression
- Control of the cell cycle
What will stress activate? (External stimulus)
Intracellular adaptive response
What internal environment is made up of?
The extra cellular fluid
What are the internal factors that must be homeostatically maintained ?
- Concentration of nutrient molecules
- Concentration of O2 and CO2
- Concentration of waste products
- pH
- Concentration of water, salt and electrolytes
- Temperature
- Volume and pressure
What will CO2 in solution form?
Carbonic acid which will reduce the pH of body fluids if CO2 accumulates
How does the body adjust to exercise ?
- Increases breathing frequency
- Increases heart rate
- Adjustments in skin physiology
- Thirst mechanism and urine output is altered
- Metabolism is altered
What is the intrinsic control system?
The local control system
How is regulation accomplished by the intrinsic control system ?
By the release of chemicals such as paracrines and autocrines
What are paracrines?
Chemical messengers that are released from one cell, and they defuse a very short distance to a neighbouring cell and this is the target cells
What are autocrines ?
Chemical messengers that are released from the same cell in which they work on
Give an example of an intrinsic control system
Hypoxic vasodilation of blood vessels
What is hypoxia ?
Low O2 levels within tissues
What is extrinsic / reflex control system ?
Long distance control
How is the extrinsic / reflex control system accomplished ?
Nervous and endocrine systems
Give an example of when the long distance control system is used.
Blood pressure regulation
What is a change is blood pressure sensed by?
Baroreceptors
Where is the cardiovascular control centre in the brain?
In the medulla oblongata
What is negative feedback?
Negative feedback consists of pathways where the response opposes or removes the stimulus
Where are signals sent during temperature regulation ?
Anterior hypothalamus
What does the hypothalamus cause to happen due to high temperatures?
Dilation of blood vessels in the skin to increase the SA over which the heat can be lost by radiation
And activate sweat glands
Flatten hair on skin
What type of feedback can occur during a fever?
Positive feedback - continual increase in body temperature
What happens during positive feedback?
It inhances the initial change and does not maintain homeostasis
What is needed to shut off the feedback loop during positive feedback ?
An outside factor
What causes an increase in temperature during a fever?
Infections (bacterial/virus)
What are pyrogens and what produces them ?
They are produced by immune cells and they are chemicals that increase the setpoint for temperature in the hypothalamus
What else can increase the set point in the hypothalamus?
The component parts of the bacterium or virus
What does the hypothalamus release ?
PGE2
What can limit homeostasis ?
Age
Presence of pathological condition
What mechanisms are altered by age?
Fluid balance
Thermoregulation
What happens usual negative feedback mechanisms during pathological states ?
They become overwhelmed
When does homeostatic imbalance occur?
When a factor in the internal environment is controlled inadequately, it’s level falls outside of the normal range
Give examples of homeostatic imbalance in the cardiovascular system
Chronic hypertension
Atherosclerosis
Congestive heart failure
Give examples of homeostatic imbalance in the endocrine system
Type 1 diabetes
What cells in the pancreas have glucose receptors ?
Beta cells
