Homeostasis Flashcards
Define homeostasis
Maintenance of a constant internal environment
What factors must be kept constant and why?
Temperature: for enzymes in body to function effectively
Blood glucose concentration: affect water potential of blood and tissue fluid, respiratory substrate
Water potential: cells burst / crenate
What is negative feedback?
Mechanism that counteracts changes in internal environment and restores it towards the set norm
What receptors detect changes in what factors?
Temperature: thermorecepters in skin, hypothalamus
Pancreas: blood glucose
Hypothalamus: water potential of blood
Function of sweat glands and what they look like
Secrete sweat onto surface of the skin, evaporates and removes latent heat of vaporisation, cooling body
Knot in dermis
Function of thermoreceptors and what they look like
Sense/detect the temperatures of the surrounding skin, and generate nerve impulses to be sent to the nervous system
Comb branches at epidermis
Function of blood vessels and what they look like
Arterioles and venules located in fatty layer of skin, capable of vasoconstriction and vasodilation to control amount of blood flowing near skin surface (and amount of heat loss through radiation)
A U-turn at the epidermis
Function of fat tissue and what they look like
Provides insulation and padding
Not part of the skin
Below the dermis
Function of the skin
Mechanical protection: prevent entry of bacteria, separates internal body from environment
Thermoregulation: enables body temperature to be around 37
Definition of thermoregulation
The maintenance of a constant internal body temperature at 37°C
What happens when body temperature rises above the norm?
Stimulus: high air temperature or exercise
Receptors: thermoreceptors in the skin / hypothalamus
Negative feedback mechanisms:
- vasodilation of arteriole, increased blood flow to capillaries in skin surface to increase heat loss via conduction, convection, radiation
- more active sweat glands, increasing sweat production and secretion onto surface of skin, more evaporation and heat loss via latent heat of vaporisation
- decreased metabolic activity
Result: body temperature fall towards norm
What happens when body temperature falls below the norm?
Stimulus: low air temperature or drinking cold drinks
Receptors: thermoreceptors of skin / hypothalamus
Negative feedback mechanisms:
- vasoconstriction of arteriole, decreased blood flow to capillaries in skin surface, less heat loss via conduction, convection, radiation
- less active sweat glands, less sweat secreted onto surface of the skin and less heat loss via latent heat of vaporisation
- shivering, involuntary muscle contractions release heat
- increased metabolic activity
Result: body temperature rises towards norm
Definition of blood glucose concentration regulation
The maintenance of a constant blood glucose concentration
What happens when blood glucose level rises above the norm?
Stimulus: eating a meal high in carbohydrates
Receptors: pancreas
Negative feedback: insulin released by pancreas’ islets of Langerhans, targeting liver and muscle
- cell membranes become more permeable to glucose to take more in
- enzyme activated to speed up rate of conversion of glucose to glycogen
- cells absorb and remove glucose
Result: blood glucose concentration falls towards norm
What happens when blood glucose concentration falls below norm
Stimulus: exercising, fasting
Receptors: pancreas
Negative feedback: glucagon released by pancreas’ islets of Langerhans, targets liver
- enzyme activated to speed up glycogen to glucose conversion
- cells release glucose into blood
Results: blood glucose concentration rises towards norm
