Need for communication systems in multicellular organisms.
- Need to respond to external stimuli for increased survival chances.
- Need to respond to
... [Show More] internal stimuli for optimal metabolic conditions.
- Organ function must be co-ordinated to maintain relatively constant internal enviroment.
What is cell signalling?
Communication between two cells.
One cell releases chemical which affects another (target) cell.
Cell signalling between adjacent cells.
Cells in nervous systems communicate by sending neurotransmitters to adjacent cells (ie, muscle/nerve cell)
Cell signalling between distant cells.
Cells release hormones which travel to distant target cells via bloodstream
How do cells recognise chemicals involved in cell signalling?
Through cell surface receptors.
What is homeostasis?
Maintenance of stable equillibrium in internal body conditions.
What role do receptors play in homeostasis?
Detect when levels are too high/low and communicate information via nervous/hormonal system.
What role do effectors play in homeostasis?
Respond to counteract change/bring levels back to normal.
What is positive feedback?
Effectors respond to further increase level away from normal levels to amplify the change.
NOT involved in homeostasis as it doesnt maintain a constant internal enviroment.
What is negative feedback?
Mechanism that store levels back to normal.
Receptors detect when a level his too high/low and communicate this information to effectors via the hormonal/nervous system.
Effectors respond to counteract the change and restore levels to normal
Only works within certain limits, if change is too high then effectors may not be able to counteract the change.
List 4 features of ectotherms.
unable to control internal body temperature - controls temperaure through behavior
internal temperature depends on external temperatire of their surroundings.
More active at higher temperatures and less active at lower temperatures.
Variable metabolic rate - they genarate little heat themselves.
List 4 feaures of endotherms
Controls internal vody temperature via homeostasis and w/ behavioural responses.
Within limits, their internal temperature is less affected by external temperature.
Can be active at any temperature within certain limits.
high metabolic rate - generates lots of heat from metabolic reactions.
AD
List 3 mechanisms mammals use to reduce body temperature when it's too hot.
Sweating
Hairs lie flat
Vasodilation
Sweating
sweat glands release more sweat.
water in sweat evaporates and removes heat from skin surface so skin is cooled.
Hairs lie flat.
Erector pilli muscles relax so hair lies flat.
Less air is trapped between the hairs, so skin is less insulated so heat is lost more easily.
Vasodilation
Arterioles near skin surface dilate when it's too hot.
more blood flows through the capillaries in the surface layer of the dermis. [Show Less]