Unit 5 - Communication and Homeostasis Flashcards
The need for communication systems
Respond to changes in the internal and external environment
Coordinate the activities of different organs
How we respond to changes
Hormonal
Neuronal
Cell communication
Process by which a cell detects and responds to signals in its environment. It is the way in which cells interact w/ their environment and other cells around them
Properties of a good communication system
Covers entire body
Be v. spp in the communication
Rapid
Enable both long and short-term responses
Methods of cell signalling
Chemical or neuronal
Affecting distant or nearby cells
Types of cell signalling
Autocrine Gap Junction Synaptic Paracrine Endocrine Contact - dependent
Ending communication
Reuptake by cells
Broken down by neurotransmitters
Messenger removed from liver e.g. hormone
Response
A change in behaviour or physiology as a result of a change in the environment
Stimulus
Any change in the environment that causes a response
Effector
An organ or cell that acts in response to a stimulus
Receptors
An organ or cell able to detect and respond to environmental stimuli and transmit an impulse to a sensory nerve
Homeostasis
The maintenance of a constant or near constant internal environment within a narrow limit even though the environment’s changing
Homeostatic control and principle
Stimulus Receptor Communication pathway Effector Response
Negative feedback
Varying physiological value is returned to its mean value by the controlling mechanism
Positive feedback
Varying physiological value is pushed above its mean value by the controlling mechanism
Why should body temp be kept constant
To keep enzymes working at their optimum and so that they don’t denature at higher temps
Why should blood glucose conc. be kept constant
To supply sufficient glucose to tissues for respiration without decreasing the water potential of the blood too much
Contributes to oncotic pressure (forming tissue fluid)
Why should blood salt levels be kept constant
To maintain water potential and blood pressure
Why should the water potential of blood be kept constant
To maintain blood pressure and to ensure cells are in the correct conditions
Why should the blood pressure be kept constant
To ensure it is high enough to deliver blood efficiently but without damaging blood vessels
Why should the carbon dioxide levels be kept constant
CO2 reacts w/ water to form an acid - change in pH can alter protein structure and effect enzymes activity
Behavioural adaptations of ectotherms when its too hot
Finding shade
Reduce contact/decrease SA exposed to the sun
Burrow underground
Behavioural adaptations of ectotherms when its too cold
Basking in the sun
Finding a hot surface to lie on
Increase SA exposed to sun
Adaptations of endotherms when its too hot
Sweat Vasodilation Hairs and feathers lie down Panting Decrease respiration rate No shivering
How does panting cool down endotherms
Lose heat through water vapour
How does decreased respiration rate cool down endotherm
Respiration is an exothermic reaction
Vasodilation
Sphincters open
Increase in diameter of lumen of arteriole to increase blood flow
Heat is lost through radiation
Vasoconstriction
Sphincters closed
Decrease in diameter of lumen of arteriole to decrease blood flow
Heat is conserved through radiation
Thermoregulatory centre
Located in hypothalamus concerned mainly w/ the regulation of heat production, inhibition and conservation to maintain a normal body temp
Periphery temp receptors
Receptors monitor temp of extremities (early detection for hypothalamus)
Adaptations of endotherms when its too cold
Vasoconstriction
Contraction of erector pilli attached to base hairs
Increase respiration
Involuntary muscle contraction
Neuronal signalling
Uses interconnected networks of neurons that signal to each other across synapse junctions
Conduct a signal v. quickly and enable rapid response to stimuli that may be changing quickly
Hormonal signalling
Glands secrete hormones into the bloodstream which bind to receptors on spp cells so the desired response in produced
Enables longer term responses
Endocrine Signalling
Signals are transmitted over longer distances e.g. gland to brain through the blood (insulin)
Paracrine Signalling
Cytokines diffuse through tissue fluid and act locally on nearby cells
No involvement of blood
Signal conc. gradient determines how cells act
Taken up by cells or degraded by enzymes (short lived)
Autocrine Signalling
Hormonal/ chemical messenger (autocrine)
Binds to autocrine receptors on that same cell, leading to changes to cells
Can promote proliferation and therefore cause a tumour
Contact dependent signalling
Signalling molecule is not secreted but bound to plasma membrane
Interacts w/ receptor
Particularly important between immune cells (APCs)
Synaptic Signalling
Electrical signalling
Presynaptic terminal, synaptic terminal, postsynaptic membrane
Gap Junction Signalling
Communicate directly w/ immediate neighbour through gap junctions
Gap junctions connect the cytoplasm via protein channel
Allow the passage of ions and small molecules and coordinated contraction of cardiac muscle
Endotherms
Birds and mammals
Control temp within strict limits
Variety of mechanisms to control temp
Largely independent of external temp
Ectotherms
Reptiles, fish, amphibians
Body temp fluctuate w/ fluctuations in the external temp
Relies on behavioural mechanism
Advantages of endothermy
Largely independent of external temp
Activity still possible when external temp is cold
Ability to inhabit warmer and colder parts of the world
Disadvantages of endothermy
Significant part of the energy intake is used in maintaining body temp when cold
More food required to be able to respire
Advantages of ectothermy
Can survive long periods of time w/ out eating
Greater proportion of energy can be used for growth
Disadvantages of ectothermy
Unable to generate internal heat through respiration
Incapable of activity during winter
Have to warm up in the day (risk of predators)
