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Flashcards in Homeostasis & Life Processes Deck (20):

7 Life Processes (list)

1. Sensitivity (respond to stimulus)
2. Growth
3. Respiration
4. Nutrition
5. Excretion
6. Movement
7. Reproduction


Sensitivity - what is it

-Is an awareness of changes in enviro
-animals need to respond quickly to stimuli such as heat, light, touch and chemicals



-what is it
-where it occurs
-2 types

-Process whereby energy in food is transferred to the organism
-occurs in mitochondria (controlled release of energy in a series of reactions)
2 types;
-Aerobic: Respiration that uses Oxygen and releases large amount of energy
-Anaerobic: Respiration that doesn't use oxygen and releases much less energy


Nutrition -basic (animals vs plants)

-Animals take in complex substances and break them down into simple, soluble molecules that can be used as source of energy
-Plants able to photosynthesis own food from simple substances


Excretion - what it is


-Is getting rid of metabolic waste that is produced by the body (e.g. water, urine and CO2)
*Getting rid of faeces or undigested food is ELIMINATIOn




-Is an ongoing increase in size of the organisms

-Process of moving



-Produce the next generation of offspring, thus carrying on their genes and ensuring continuation of species
2 types;
-Sexual: involves 2 parents and union of 2 gametes
-Asexual: One parent reproduces itself
-rarer; e.g. automixis in fish, sharks
-facultative parthenogenesis in reptiles and birds


Conformers vs Regulators

-Conformers: single-celled organisms and some small, simple multicellular animals that meet needs by direct exchange between their cells and an aqueous environment
-Regulators: larger, more complex animals that maintain a constant internal environment (need to maintain ECF)


Homeostasis (defn)

-3 parameters

-2 essential systems

-Homeostasis: The maintenance of constancy in the internal environment -> depends on ability to control and regulate organ and organ system function
-means "similar condition"
-Environmental factors (osmolarity, temp and pH)
-Materials for cell (nutrients, H2O, Na, Ca)
-Internal secretions (hormones, neurotransmitters)
*communication via nervous and endocrine system essential for homeostasis to occur


Cannon's 4 Postulates of homeostasis

1. Nervous system preseves 'fitness' of internal environment
-fitness = conditions that provide normal function by co-ordinating activities across body)
2. Tonic level of activity (slight adjustments made)
3. Antagonistic control (for systems not under tonic control)
-endocrine system = insulin vs glucagon for blood gluocse lvl
4. Chemical signals can have different effects in different tissues
-is receptor dependent


Domino Effect

-A change in internal or external enviro triggers response to correct change
-response may alter addition parameters, which must be readjusted = domino effect


Failure of Homeostasis - diseases

-2 types

1. Internal failure of physiological processes
-e.g. abnormal cell growth, auto-immune disease, inherited disorders
2. External causes
-e.g. toxins, trauma, bacteria

*pathophysiology: when body attempts to compensate when homeostasis is disturbed


Homeostatic Response time

Homeostatic regulation of blood pressure

-Are short term, medium term and long term

-1. Local control: cell/tissue sense a change and responds by paracrine or autocrine mechanism (paracrines relax muscles in blood vessels = dilation)
2. Reflex control pathway: where control of reaction lies outside the organ that carries out the response (more systemic in nature)


Response loops of Homeostasis

-3 components

-7 step sequence

3 components;
-An input signal
-Integration of signal
-An output signal
*reflex completed when response becomes part of stimulus and feeds back into system
Broken down sequence;
Stimulus -> receptor -> afferent pathway -> integrating centre -> efferent pathway -> effector -> response


Homeostatic receptors

-Stimulus is detected by appropriate receptors (specialised cells, parts of cell or complex multicellular receptors that respond to changes in enviro)
-e.g. notch is a ligand receptor)


Negative feedback

-Output of the system (response) opposes or removes the intensity of the original signal
-aim = to return it to its ideal value
-restore status quo but cannot prevent initial disturbance
-operate within a predetermined range (sensitivity depends)


Set point and error signal definition

-Varying a set point (2 types)

-Error signal: Difference between actual lvl and set point
-Set point: Desired level of regulated variable
-Acclimatisation: natural - adapting to natural conditions
-Acclimation: Artificial - when have short-term exposure


Types of control pathways (3)

-Biological reflex pathways are mediated by;
1. Nervous system
2. Endocrine system
3. A combination of both (neuroendocrine)
*signals usually pass through several different integration centers before reaching target tissue


Positive Feedback



-Positive Feedback: occurs when the response reinforces (enhances) the original stimulus so the output is accelerated
-causes variable to deviate further from its set point (is NOT homeostatic)
-usually control infrequent events that don't require continual adjustment (ovulation, parturition (birth))
e.g. Parturition
-pressure created by baby pushing against cervix = release of oxytocin that causes strong uterine contractions that push baby harder against cervix


Feed-forward Information

-Feed-forward regulation is to change the set point, which takes precedence over the initial set point and anticipate an event (or events)
-e.g. salivation
-caused by sight, smell or thought of food