Homeostasis Flashcards
What is homeostasis ?
The maintenance of a constant internal environment, ensuring that the internal conditions of an organism are kept within narrow limits at all times
What are the internal conditions that should be kept constant?
Blood temperature and pH
Blood water potential
Blood glucose concentration
What is negative feedback?
A regulatory corrective mechanism whereby a stimulus ( a change) causes an opposite “output” in order to maintain an ideal level of regulation to the norm. Negative feedback loop consists of a stimulus
What ar the components of a negative feedback loop?
A stimulus (change from the normal condition in the internal environment) , a receptor to detect the stimulus -> a corrective mechanism to bring about a reverse effect of the stimulus Feedback to the receptors that the condition has been restored back to its normal state. This results in a decrease in the corrective mechanism
What happens when a condition rises above normal?
Stimulus(increases above the norm)->receptor detects the stimulus -> self regulatory corrective mechanism -> condition decreases-> normal condition or set point
> -ve feedback to the receptor
Stimulus receptor corrective mechanism and effects for regulating blood glucose concentration when it rises above the norm?
Stimulus: concentration of blood glucose increases above the norm
Receptor : islets of Langerhans in the pancreas is stimulated
Corrective mechanism: islet of langerhans secretes more insulin which is transported by the blood to the liver
Permeability of the cell surface membrane to glucose increases
Insulin stimulates the liver to convert excess glucose to glycogen
Glycogen is stored in the liver and muscles
Effects: concentration of blood glucose decrease back to the norm
Feedback sent to the pancreas and the insulin production falls due to negative feedback
What is the stimulus, receptor, corrective mechanism and effects to regulate blood water potential when it rises above the norm?
Stimulus: blood water potential increases above the norm
Receptor: hypothalamus in the brain detects the stimulus
Corrective mechanism: pituitary gland releases less anti diuretic hormone (ADH)
:cells in the walls of the collecting duct becomes less permeable to water
:less water is reabsorbed by the kidney tubules back into the bloodstream
Effects: more water is excreted
: urine produced is more diluted
: water potential of the blood decreases back to the norm
:feedback is sent to the hypothalamus and ADH production increases
What are the functions of the skin?
- protection from injury
- protection from water loss
- detection of changes in the environment
- production of sweat
- temperature regulation
What is the skin composed of?
Epidermis layer consisting of the cornified layer(dead dry cells with keratin deposits) , the granular layer (moving cells that moves upwards) and the innermost malpighian layer that consists of actively dividing cells that contain melanin
Dermis layer
What leads to heat gain in the body?
Metabolic activities lie cellular respiration (especially in muscles and liver)
Vigorous muscular exercise
Consumption of hot food
Being in warm environments
How is heat lost by the body?
Through the skin surface via convection, conduction and radiation
Evaporation of water in swear
Expired or exhaled air from the lungs
Faeces and urine
What is the stimulus receptor , corrective mechanism and effects of thermoregulation when the body temperature rises above the norm?
Stimulus: blood and skin temperature rises above the norm
Receptor: thermoreceptors in skin sends information about temperature changes in the external environment to the hypothalamus in the brain
: brain also detects the change in temperature of the blood flowing through it
Corrective mechanism: (vasodilation)arterioles dilate. Shunt vessels constrict. More blood flows to the capillaries in the skin.
: sweat glands becomes more active. Production of sweat increases
: rate of metabolic activities in the body decreases
: increased rate of breathing
: hair erector muscles relax and more air is allowed to circulate over the skin
Effects: more heat is lost from the surface of the skin and the body
: more latent heat of vaporisation is lost through the evaporation of water in sweat
: less heat is released within the body
What is the function of blood capillaries in the skin?
Supply blood to the skin
What is the function of the hair erector muscle?
Contracts and causes hair to stand, trapping a layer of air above the skin surface
What is the sweat gland and its function?
A coiled tube richly surrounded by blood capillaries
Secretes sweat which flows through the sweat duct and sweat pore at the surface of the skin
