Homeostasis & Life Processes Flashcards
7 Life Processes (list)
- Sensitivity (respond to stimulus)
- Growth
- Respiration
- Nutrition
- Excretion
- Movement
- 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
Respiration
- 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
-elimination
- 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
Growth
Movement
- Is an ongoing increase in size of the organisms
- Process of moving
Reproduction
-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”
- Parameters;
- 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
- Nervous system preseves ‘fitness’ of internal environment
- fitness = conditions that provide normal function by co-ordinating activities across body)
- Tonic level of activity (slight adjustments made)
- Antagonistic control (for systems not under tonic control)
- endocrine system = insulin vs glucagon for blood gluocse lvl
- 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
- Internal failure of physiological processes
- e.g. abnormal cell growth, auto-immune disease, inherited disorders
- 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
- Local control: cell/tissue sense a change and responds by paracrine or autocrine mechanism (paracrines relax muscles in blood vessels = dilation)
- Reflex control pathway: where control of reaction lies outside the organ that carries out the response (more systemic in nature)
- Local control: cell/tissue sense a change and responds by paracrine or autocrine mechanism (paracrines relax muscles in blood vessels = dilation)
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
- definition
- e.g.
- 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
- e.g. salivation
