Communication and Homeostasis Flashcards
Internal conditions animals must respond to Blood glucose concentration
water potential
External conditions animals must respond to Humidity
light intensity
How do animals respond to changes in the environment? Using hormones or nerves
How do plants respond to changes in the environment? Using hormones
Why do animals and plants need communication systems? Presence of sets of different cells and systems with different functions that need to be coordinated
few systems can work in isolation
Example of plants using communication systems Light sensitive chemicals activated by increased light present in Spring and Summer
development of flower buds
Example of animals using communication systems Stem cells differentiate into red blood cells
red blood cells transport oxygen to respiring muscle tissue
Cell signalling When a cell releases a chemical which has an effect on a target cell
Can cell signalling work over short and long distances? Yes
Example of cell signalling over short distances Neurotransmitter over a synapse
Example of cell signalling over long distances ADH to the kidneys
Homeostasis Maintenance of a constant internal environment
Example of homeostasis Maintenance of a constant blood glucose concentration by the pancreas
duodenum
Role of receptors To detect changes in internal and external environment of an organism
Effectors Muscles or glands that react to a motor stimulus to bring about a change in response to a stimulus
Negative feedback Process bringing about reversal of change in conditions to ensure that an optimum steady state is maintained as the internal environment returns to the original set of conditions after a change
Positive feedback Process that increases any change detected by the receptors
Difference between negative and positive feedback Negative feedback leads to homeostasis
positive feedback doesn’t
Process of homeostasis Stimulus
change detected by receptors
Example of negative feedback Control of heart rate
controlled by medulla oblongata which is made up of two centres
Example of positive feedback Oxytocin in uterine contractions
the stretching of the cervix signals the anterior pituitary gland
Endotherms Organisms that can regulate their body temperature within a very narrow range in a wide variety of external conditions
How endotherms detect temperature changes Peripheral temperature receptors in the skin
temperature receptors in the hypothalamus
What do peripheral temperature receptors in the skin detect? Changes in the surface temperature
What do temperature receptors in the hypothalamus detect? Temperature of the blood deep in the skin
Behavioural responses by endotherms to temperature changes Basking
pressing against warm surfaces
Aestivation Period of prolonged or deep sleep during the Summer or dry seasons
Endoderm’s physiological responses to increasing temperature Vasodilation
increased sweating
Process of vasodilation Arterioles near the surface of the skin dilate
arteriovenous shunt vessels construct
How to reduce the insulating effect of hair or feathers Erector pili muscles in the skin relax
hair or feathers lie flat against the skin
Anatomical adaptations of endotherms (Depending on their environment) SA:V
colour of fur or feathers
Endoderm’s physiological response to decreasing temperature Vasoconstriction
decreased sweating
Process of vasoconstriction Arterioles near the surface of the skin constrict
arteriovenous shunt vessels dilate
Process of raising the body hair or feathers Erector pili muscles contract
hair or feathers go erect
How is temperature controlled? (Name of mechanism) Negative feedback from the hypothalamus
Control centres in the hypothalamus Heat loss centre
heat gain centre
Role of the heat loss centre Temperature of the blood flowing through the hypothalamus increases
impulses sent through autonomic motor neurones to effectors in the skin and muscles
Role of the heat gain centre Temperature of the blood flowing through the hypothalamus decreases
impulses sent through the autonomic nervous system to effectors in the skin and muscles
Thermoregulation Maintenance of a relatively constant core body temperature to maintain optimum enzyme activity
Ectotherms Organisms that use their surroundings to warm their bodies
Behavioural responses of ectotherms Basking
orientating their bodies so maximum surface area is exposed to the sun
Physiological responses of ectotherms Colours
altering heart rate to alter metabolic rate
