Module 5 - Communication, homeostasis and energy
Describe the need for communication To maintain a constant internal environment
systems in multicellular organisms in response to changes in the internal and
external environment and to coordinate the
activities of different organs
Describe the communication between The neuronal system uses
adjacent cells neurotransmitters, which act as chemical
signals, to send signals between neurones
at synapses
Describe the communication between The hormonal system secretes hormones in
distant cells the blood, which act as chemical signals,
acting only on target cells
Homeostasis The maintenance of a stable internal
environment within a narrow range about a
set point
Describe receptors Detects changes in the internal/external
environment of an organism
Describe effectors Muscles or glands that react to a stimuli to
bring about a change
Differences between positive and negative Positive - Effectors respond to further
feedback increase the level away from the normal
level
Negative - Effectors respond to counteract
the change bringing the level back to
normal
How do ectotherms control their By changing their behaviour as they can’t
temperature control their temperature independent of the
environment
How do endotherms control their By controlling their temperature internally by
temperature homeostasis, as well as altering their
behaviour as they can control their
temperature independent of the
environment
, List 3 mechanisms to reduce body 1. Sweating
temperature 2. Hairs lie flat
3. Vasodilation
List 5 mechanisms to increase body 1. Shivering
temperature 2. Hormones
3. Much less sweat
4. Hairs stand up
5. Vasoconstriction
Describe how sweating reduces body More sweat is secreted from sweat glands
temperature and water in sweat evaporates from the
surface of the skin which takes heat from
the body
Describe how hairs lying flat reduces body Erector pili muscles relax so hairs lie flat,
temperature less air is then trapped so the skin is less
insulated and heat can be lost more easily
Describe how vasodilation reduces body Arterioles near the surface of the skin dilate
temperature so more blood flows through the capillaries
in the surface layer of the dermis so more
heat is lost from the skin by radiation
Describe how shivering increases body Muscles contract in spasms making the
temperature body shiver so more heat is produced from
increased respiration
Describe how secreting hormones Adrenaline and thyroxine increase
increases body temperature metabolism so more heat is produced
Describe how vasoconstriction increases Arterioles near the surface of the skin
body temperature constrict so less blood flows through the
capillaries in the surface layer of the dermis
Describe how hairs standing up increases Erector pili muscles contract trapping more
body temperature air under a layer of hair to provide insulation
thus preventing heat loss
Describe how body temperature is 1. Thermoreceptors detect an increase
controlled when there is a rise in body in body temperature so generate
temperature impulses to the hypothalamus which
sends impulses to effectors via the
CNS
2. Effectors respond and increase heat
loss from the body
Describe how body temperature is 1. Thermoreceptors detect a decrease
controlled when there is a decrease in body in body temperature so generate
temperature impulses to the hypothalamus which
sends impulses to effectors via CNS
2. Effectors respond to produce more
heat and to conserve it
Define excretion The removal of metabolic waste products
Describe the need for communication To maintain a constant internal environment
systems in multicellular organisms in response to changes in the internal and
external environment and to coordinate the
activities of different organs
Describe the communication between The neuronal system uses
adjacent cells neurotransmitters, which act as chemical
signals, to send signals between neurones
at synapses
Describe the communication between The hormonal system secretes hormones in
distant cells the blood, which act as chemical signals,
acting only on target cells
Homeostasis The maintenance of a stable internal
environment within a narrow range about a
set point
Describe receptors Detects changes in the internal/external
environment of an organism
Describe effectors Muscles or glands that react to a stimuli to
bring about a change
Differences between positive and negative Positive - Effectors respond to further
feedback increase the level away from the normal
level
Negative - Effectors respond to counteract
the change bringing the level back to
normal
How do ectotherms control their By changing their behaviour as they can’t
temperature control their temperature independent of the
environment
How do endotherms control their By controlling their temperature internally by
temperature homeostasis, as well as altering their
behaviour as they can control their
temperature independent of the
environment
, List 3 mechanisms to reduce body 1. Sweating
temperature 2. Hairs lie flat
3. Vasodilation
List 5 mechanisms to increase body 1. Shivering
temperature 2. Hormones
3. Much less sweat
4. Hairs stand up
5. Vasoconstriction
Describe how sweating reduces body More sweat is secreted from sweat glands
temperature and water in sweat evaporates from the
surface of the skin which takes heat from
the body
Describe how hairs lying flat reduces body Erector pili muscles relax so hairs lie flat,
temperature less air is then trapped so the skin is less
insulated and heat can be lost more easily
Describe how vasodilation reduces body Arterioles near the surface of the skin dilate
temperature so more blood flows through the capillaries
in the surface layer of the dermis so more
heat is lost from the skin by radiation
Describe how shivering increases body Muscles contract in spasms making the
temperature body shiver so more heat is produced from
increased respiration
Describe how secreting hormones Adrenaline and thyroxine increase
increases body temperature metabolism so more heat is produced
Describe how vasoconstriction increases Arterioles near the surface of the skin
body temperature constrict so less blood flows through the
capillaries in the surface layer of the dermis
Describe how hairs standing up increases Erector pili muscles contract trapping more
body temperature air under a layer of hair to provide insulation
thus preventing heat loss
Describe how body temperature is 1. Thermoreceptors detect an increase
controlled when there is a rise in body in body temperature so generate
temperature impulses to the hypothalamus which
sends impulses to effectors via the
CNS
2. Effectors respond and increase heat
loss from the body
Describe how body temperature is 1. Thermoreceptors detect a decrease
controlled when there is a decrease in body in body temperature so generate
temperature impulses to the hypothalamus which
sends impulses to effectors via CNS
2. Effectors respond to produce more
heat and to conserve it
Define excretion The removal of metabolic waste products
