Communication and Homeostasis Flashcards
What conditions does a cell need to maintain in their cells
-A suitable temperature
-A suitable pH
-An aqueous environment that keeps substrates in a solution
-Freedom from toxins and excess inhibitors
Stimulus/response
Stimulus - Change in environment
Response - The way in which an organism changes its behaviour or physiology
Example of an organism reacting to a change in the environment
The arctic fox has a thicker white coat in the winter and a thinner grey/brown coat in the summer
Whitecoat - insulation and camouflage
Example of a multicellular organism reacting to a change within its internal environment
Build up of waste may act directly on the cells which respond by reducing activity so less waste is produced - response may not be good for the organism
What is the composition of the tissue fluid maintained by
The blood - takes waste products away
Why is a multicellular organism more efficient than a unicellular organism
Its cells are differentiated- cells are specialised to perform particular functions
What makes a good communication system
-Covers the whole body
-Cell communication
-Specific communication
-Rapid communication
- Short term and long term repsonses
Two major systems that work by cell signaling:
Neuronal
Hormonal
Homeostasis
Maintaining a constant internal environment despite changes in the external and internal factors
Aspects maintained by homeostasis
-Body temperature
-Blood glucose concentration
-Blood salt concentration
-Water potential of the blood
-Blood pressure
-Carbon dioxide concentration
Input and output of negative feedback
Change away from optimum - Receptor detects change - Communication system informs effector - Effector reacts to reverse change -returns to optimum
For negative feedback a number of processes must occur:
-A change in the internal environment must be detected
-The change must be signaled to other cells
-There must be an effective response that reverses the change in conditions
Endotherms
An organism that uses heat from metabolic reactions to maintain body temperature
-Controls body temperature within strict limits
Endotherms are exogenic
Release energy in the form of heat
-increasing respiration
-Directing blood towards or away from the skin
Endotherms - Skin response if the body is too hot
-Sweat glands secrete fluid onto the skin surface as this evaporates it uses heat from blood as latent heat of vaporisation
-Hairs and feathers lie flat to reduce insulation and allow greater heat loss
-Vasodilation of arterioles direct blood to the skin surface so more heat can be radiated away from the body
Endotherms - Skin response if the body is too cold
-Less sweat is secreted so less evaporation means less heat loss
-Hairs and feathers stand erect to trap air which insulates the body
-Vasoconstriction of arterioles leading to skin surface direct blood away from the skin and less heat is lost
Endotherms - gaseous exchange response if the body is too hot
Some animals pant increasing evaporation from the surface of lungs and airways
Evaporation uses heat from blood
Endotherms - gaseous exchange response if the body is too cold
Less panting so less heat is lost
Endotherms - liver response if the body is too hot/cold
Less respiration / increases respiration so more energy from food is converted to heat
Endotherms - skeletal muscle response if the body is too hot/cold
Fewer contractions/spontaneous muscle contractions (shivering)
Endotherms - blood vessel response if the body is too hot/cold
Dilation / constriction
Behavioral responses if the body is too hot - endotherms
Hide away from the sun
Orientate body to reduce surface area exposed to sun
Remain inactive
Wet skin uses evaporation to help cool the body
Advantages of endotherms
-Maintain a fairly constant body temperature
- Remain active when external temperatures are low which means can escape predators
-inhabit colder parts of the planet
Disadvantages of endotherms
-Use a significant part of their energy to maintain body temperature if cold
-Need more food
-Use for growth a lower proportion of energy and nutrients gained from food
-May overheat in hot weather
What detects a change in the body’s core temperature
Temperature receptors (thermoregulatory centre) in the hypothalamus - then send out impulses to cause different responses which will reverse this change
Neurons - quick responses
Hormones - Long term
If core body temperature is too low the hypothalamus will bring about:
-Changes in the skin to reduce heat loss
-Release of heat through extra muscular contraction
-Increased metabolism in order to release more heat from exergonic reactions
What detects a change in temperature in extreme cases
Periphral temperature receptors in the skin
Ectotherms
An organism that relies on external sources of heat to maintain body temperatures
-Cannot control body temperatures as effectively as endotherms
-Body temperature fluctuates with external temperature
If ectotherms are too hot/cold
Behavioral responses
Too hot:
-Move into a sunny area
-Lie on a warm surface
-Expose a larger SA to the sun
opp/if too hot
Snake behavioral adaption and benefit
Basks in the sun - absorbs heat directly from the sun
Locust behavioral adaption and benefit
Early morning locusts sit side in exposing a larger SA to the sun but at midday head n exposing a smaller SA
Increase breathing rate and depth of breathing movements - more water evaporates from the tracheal system cooling the body
Lizard behavioral adaption and benefit
Hide in a burrow when hot and coolest parts of the day - underground has more stable temperatures
Horned lizard behavioral adaption and benefit
Can change shape by expanding/contracting ribcage - expanding increases SA exposed to the sun
Advantages of ectotherms
-Less food used in respiration
-More energy and nutrients from food for growth
-Need less food
-Survive long periods without food
disadvantages of ectotherms
Less active at cooler temperatures means more at risk with predators and cannot take advantage of available food
Mammals response to external environment - EQ-
1) peripheral / skin , thermoreceptors / (heat) receptors ,
stimulated (by decrease in external temp) ;
2) (impulses sent to / blood temperature monitored in )
hypothalamus / sensory cortex ;
3) vasoconstriction of , arterioles / small arteries , to reduce heat loss ;
4) (prevents heat loss by) radiation / conduction / convection ;
5) increased , metabolic rate / metabolism / respiration ,
to generate heat (energy) ;
6)(release of) adrenaline / thyroxine ;
7) shivering / (involuntary) muscle spasms , to generate heat (energy) ;
8) erector / hair , muscles raise , (skin) hair / fur , to trap , air / heat ;
