Communcation And Homeostasis Flashcards
What two communication systems do animals have
Nervous system: produces rapid responses
Endocrine system: tends to carry-out longer-lasting communication.
What is cell signalling
Both nerves and hormones are examples of cell signalling. This is how individual cells communicate with others in a different location in the body, but the method by which hormones transmit those signals is different to nerves.
How endocrine gland send signals
They secrete hormones to target cells. These cells have receptors on their membrane which have a complimentary shape to the hormone.
The two types of cell signalling
Paracrine signalling: occurs between cells that are close together
Endocrine signalling: involves sending signals over longer distances, with the signalling molecule transported in the circulatory system.
What can cell signalling molecules be
These signalling molecules can be proteins, amino acids, lipids, glycoproteins and phospholipids.
In endocrine glands, these signalling molecules are hormones which can also be proteins.
What are the receptor molecules normally made of
These are generally proteins or glycoproteins. Some, steroid hormones such as oestrogen can diffuse through the membrane. Because of this, some receptors may be found in the cytoplasm.
Example of cell signalling (neurotransmitters)
Chemicals that transfer an impulse from one nerve cell across a small gap(the synapse) to another nerve cell.
Another example of cell signalling
The production of histamine in response to a chemical signal, an antibody called immunoglobulin E.
Example of cell signalling in plants
Plant hormones act as signalling molecules; for example, ethylene, which promotes fruit ripening, is detected y protein receptors, resulting in the activation of genes that cause ripening.
What is negative feedback
In these mechanisms, a change initiates a series of events which then reverses the change.
Example of negative feedback (metabolic rate)
If the metabolic rate drops, then the hormone, thyrotopin-releasing hormone, is released by the hypothalamus in the brain. This triggers the secretion of thyroid-stimulating hormone by the pituitary gland. This hormone is turn causes thyroid hormones to be secreted by the thyroid gland.
When the metabolic rate has returned to normal, the TSH ‘switches off’ the release f TRH from the hypothalamus.
What is positive feedback
This causes proliferation rather than control, and so is not involved in maintaining a steady state in the body.
An example of positive feedback (pregnancy)
The hormone, oxytocin, in secreted during contractions in childbirth. This hormone is responsible for intensifying uterine contractions. Contractions actually stimulate the release of oxytocin, so the increase it causes results in more oxytocin being released. Birth stops the release of this hormone.
Thermoregulation
Control of temperature
What is the optimum body temperature
37 degrees centigrade
Definition of endotherms
They have physiological mechanisms to control their body temperature.
These are animals that maintain its body temperature using heat generated within its body tissues.
Examples are mammals and birds
What are ecototherms
These animals rely on their behavioural adaptations to maintain their internal body temperature
So, they absorb heat from its environment to help regulate its body temperature.p
How can heat be lost from the body through radiation
This is the loss of heat in the form of electromagnetic radiation from hot objects into cooler surroundings. This is also how we can gain heat from the Sun, or a fire.
Heat loss through convection
This is the movement of currents or warm air upwards because the density of air decreases when it is warm.
Heat loss through conduction
This is the transfer of heat energy from a warmer material to a cooler one. The body can lose heat o the air by conduction, but air is a good insulator. If a layer of air can be trapped around the body it will reduce further heat loss by radiation.
Heat loss through evaporation
Water evaporates off the surface of the skin. This is because heat necessary to change the water into water vapour is extracted from the skin.
Why does water temperature not fluctuate
It has a high heat capacity.
What does ectothermic animals do to avoid overheating themselves
They do not expose themselves to extremes of temperature, and must warm their bodies rapidly if they get cold (which is unavoidable at night).
Low body temperature effects on ectothermic animals
Sluggish and slow movements; difficult to catch prey or to escape from predator.
