COMMUNICATION + HOMEOSTASIS

Internal conditions animals must respond to

Blood glucose concentration, water potential, internal temperature, cell pH

External conditions animals must respond to

Humidity, light intensity, external temperature, sound

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, maintaining conditions for enzymes

Example of plants using communication systems

Light sensitive chemicals activated by increased light present in Spring and Summer, development of flower buds, attract pollinators

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, ileum and liver

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, communication system sends message by cell signalling, message detected by an effector, return to optimum conditions

Example of negative feedback

Control of heart rate, controlled by medulla oblongata which is made up of two centres, one increases heart rate by sending impulses towards the sympathetic nervous system in the accelerator nerve, other decreases heart rate through the parasympathetic nervous system via the vagus nerve

Example of positive feedback

Oxytocin in uterine contractions, the stretching of the cervix signals the anterior pituitary gland, it secretes oxytocin, oxytocin increases uterine contractions, increasing stretching more

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, wallowing in water and mud, digging burrows, hibernation, aestivation

Aestivation

Period of prolonged or deep sleep during the Summer or dry seasons

Endoderm's physiological responses to increasing temperature

Vasodilation, increased sweating, reducing insulating effect of hair or feathers

Process of vasodilation

Arterioles near the surface of the skin dilate, arteriovenous shunt vessels construct, forces blood through capillary networks close to the surface of the skin, skin cools due to radiation

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, prevents trapping of layers of air

Anatomical adaptations of endotherms (Depending on their environment)

SA:V, colour of fur or feathers, insulation

Endoderm's physiological response to decreasing temperature

Vasoconstriction, decreased sweating, raising body hair or feathers, shivering

Process of vasoconstriction

Arterioles near the surface of the skin constrict, arteriovenous shunt vessels dilate, little blood flows through the capillary networks close to the surface of the skin, little radiation

Process of raising the body hair or feathers

Erector pili muscles contract, hair or feathers go erect, traps insulating layer of air

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, responses occur that lower the temperature

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, responses occur that raise the temperature

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, extending parts of their body to increase surface area, pressing bodies against ground

Physiological responses of ectotherms

Colours, altering heart rate to alter metabolic rate