chapter 12: homeostasis Flashcards
what is homeostasis?
- the maintenance of a constant internal environment
with a stable environment, homeostasis allows…
an organism to be independent from changes in the external environment
why do body temperatures have to be kept constant?
- enzymes in our body may only work in a certain range of temperature
> changes in temp can cause enzymes to be inactive or denatured
> high fevers can be fatal
why must tissue fluid be kept at a constant pH and water potential?
- drastic changes in the pH value may affect enzymes reactions in cells and harm your body
- water potential also affects cells
describe the negative feedback process.
- if the system is disturbed
- your body reacts to bring about an opposite effect to the changes detected
>it sets in motion a sequence of events that tends to restore the system to its original state
in a negative feedback loop, there must be:
- a norm to be mantained
- a stimulus: a change in the internal environment
- a receptor: to detect the stimulus and sends signal to the control centre
- a corrective mechanism: bring about the reverse effect of the stimulus
- a feedback to the receptor when the set point is reached which causes the corrective mechanism to stop
what are the examples of homeostasis in humans?
(pg 244-246)
- regulating body temperature
-regulating blood glucose concentration
-regulating water potential
what happens when blood glucose level rises above the normal level?
(pg 244)
blood transports insulin to the liver and muscles
- stimulus- the blood glucose conc rises above normal
- receptor- the islets of Langerhans in the pancreas are stimulated
- corrective mechanism: islets of Langerhans secrete insulin into the bloodstream
- blood transports insulin to liver and muscles
* insulin increases the permeability of the cell surface membrane to glucose
> glucose absorbed into the cells more quickly
*insulin causes liver and muscles to convert excess glucose into glycogen and is stored in the liver and muscles - blood glucose conc decreases
> provides a feedback to the receptor to
> reduce insulin production (corrective mechanism stops)
> back to the normal set point
what happens when blood glucose level fall below normal level?
- stimulus: the blood glucose conc falls below normal level
- receptor: the islets of langerhans (in pancreas) are stimulated
- corrective mechanism: the islets of langerhans secrete glucagon into the bloodstream
- blood transfers glucagon to the liver and muscles
>converts stored glucagon back into glucose
- from the liver, glucose enters the bloodstream - blood glucose conc increases
> provides feedback to the receptor to decrease the glucagon production
> back to normal
what happens when the water potential of blood is higher than normal?/
- stimulus: water potential of blood increases
- receptor: the hypothalamus is stimulated
- corrective mechanism:
- less ADH is released by the pituitary gland into the bloodstream
- less ADH is transported to the kidneys
- the cells in the walls of the collecting ducts becomes less permeable to water
- less water reabsorbed into the bloodstream
- more water excreted
- urine is more diluted
- more urine produced - water potential decreases
> feedback to the recepter
> back to normal!
describe what the blood vessels ( capillaries and arterioles) do.
( structures involved in temperature regulation)
- blood vessels are present in the dermis
- CONSTRICTION and DILATION of arterioles is caused by the contraction muscles in the arteriole walls
> which help to regulate body temp - dilation of arterioles > VASODILATION
> more blood is sent to the capillaries in your skin
[ more heat is loss from convection, conduction and radiation] - constriction of arterioles> VASOCONSTRICTION
> reduces the amount of blood flowing through the capillaries in the skin
describe the formation of hair.
( structures involved in temperature regulation)
- hairs are produced by the epidermis and are embedded in the dermis
- the malpighian layer of the epidermis sinks into the dermis to form a hollow tube called the HAIR FOLLICLE
> each hair grows inside the hair follicle - at the base of the hair follicle is the mass of tissue called
> HAIR PAPILLA
> which contains blood capillaries and nerves
> it is covered with epidermal cells that constantly divide, pushing new cells outwards
> cells pushed outwards gradually die and harden to form hair
-hair erector muscles are attached to the hair follicles and when the muscles contract
> hairs stand on their ends
what are sweat glands?
( structures involved in temperature regulation)
- each sweat gland is a coiled tube formed by the downgrowth of the epidermis
> forms a tight knot in the dermis and is surrounded by many blood capillaries - secreted sweat flows through the sweat DUCT to a sweat PORE that opens at the skin surface
> secreted sweat is made up of water and contains dissolved salts and small amounts of urea
> skin considered an excretory organ
what are sensory receptors?
( structures involved in temperature regulation)
- the structure in the body that detect changes in the environment
- nerve endings in the skin are sensory receptors
> enable us to sense pain, pressure and temperature changes in the external environment - receptors that detect temperature changes are called
> THERMORECEPTORS
how does your body produce and gain heat?
(temperature regulation)
- metabolic activities (eg. cellular respiration) produces heat
- high levels of cellular respiration takes place in liver and muscles
> a large amount of heat is released in these organs
> heat distributed around the body via the bloodstream
body can gain extra heat through:
- vigorous muscular exercise
- the consumption of hot food
- being in warm environments
