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5.1.1 Communication and Homeostasis (Need for Communication (good…
5.1.1 Communication and Homeostasis
Need for Communication
respond to changes in internal and external environment
coordinate activities of different organs
enzymes need a specific set of conditions to work efficiently
temperature
pH
aqueous environment (water)
no toxins or excess inhibitors
changes in external environment e.g. temperature, predator
changes in internal environments e.g. pH, buildup of waste toxic products
good communication system:
cover whole body
cells communicate with each other
specific communication
rapid communication
short term and long term responses
Neuronal system: rapid responses, short term
Hormonal system: slower responses, long term
Cell Signalling
adjacent cells
distant cells
the way in which cells communicate with each other, by releasing chemicals that are detected by other cells, and bringing about a response from the stimuli
stimulus: change in environment
response: way in which organism changes behaviour of physiology
Homeostasis
sensory receptors: cells/sensory nerve endings that respond to a stimulus in the internal or external environment of an organism and can create action potentials
effectors: cell, tissue, or organ that brings about a response
positive feedback: mechanism that increases a change, taking it further away from the optimum
negative feedback: mechanism that reverses a change; brings a system back to the optimum
maintaining a constant internal environment despite changes in internal and external factors (always some fluctuation)
body temperature
blood glucose concentration
blood salt concentration
water potential of blood
blood pressure
carbon dioxide concentration
stimulus --> receptor--> communication pathway --> effector --> response
Ecotherms
if too hot:
move out of sun
move underground
reduce body surface exposed to sun
if too cold:
move to sunny area
lie on warm surface
large surface area exposed
muscle contractions generate heat through respiration
an organism that relies on external sources of heat to maintain body temperature
use mostly behavioural mechanisms to control body temperature
Advantages:
can eat less, as less food used in respiration
energy from food converted to growth
can survive long periods without food
Disadvantages:
less active in cooler temperatures
can't live in varied environments
Endotherms
if too hot:
sweating; water evaporates and cools down body; water has a high latent heat of vaporisation
vasodilation of arterioles and precapillary sphincters; more blood to skin so heat can be directed away from body
panting; water evaporation
if too cold:
hairs stand erect to trap air for insulation
vasoconstriction of arterioles and precapillary sphincters; blood away from skin surface so less heat loss
shivering; muscle contractions; need to respire more; release more heat to warm up body
an organism that uses heat from metabolic reactions to maintain body temperature, within strict limits
Advantages:
can live in a variety of different environments at different temperatures
remain active when temperature is low
Disadvantages:
need to eat a lot
less energy from food used for growth
How:
1) temperature too high or low (stimulus)
2) thermoreceptors in hypothalamus or brain detect change in blood temperature
3) brain coordinates response, and signals sent to effectors (response)
4) temperature returns to optimum
negative feedback
peripheral temperature receptors: located in skin, and can signal to thermoregulatory centre (hypothalamus) early on
Control of Body Temperature
temperature increase:
molecules have more kinetic energy and collide faster and more often
rate of reactions increases
enzymes denatured as tertiary structure changes shape and substrate can't bind to active site
temperature decrease
rate of reactions decreases
molecules have less kinetic energy so don't have enough energy to react
reactions release heat; less reaction = less heat = body cools down further; positive feedback
core temperature is more important to maintain that peripheral temperature as all the vital organs are located
Sammer Sheikh