Homeostasis & Life Processes

Question 1

7 Life Processes (list)

Answer 1

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

Question 2

Sensitivity - what is it

Answer 2

• Is an awareness of changes in enviro

- animals need to respond quickly to stimuli such as heat, light, touch and chemicals

Question 3

Respiration

• what is it
• where it occurs
• 2 types

Answer 3

-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

Question 4

Nutrition -basic (animals vs plants)

Answer 4

• 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

Question 5

Excretion - what it is

-elimination

Answer 5

• 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

Question 6

Growth

Movement

Answer 6

• Is an ongoing increase in size of the organisms

- Process of moving

Question 7

Reproduction

Answer 7

-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

Question 8

Conformers vs Regulators

Answer 8

• 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)

Question 9

Homeostasis (defn)

• 3 parameters
• 2 essential systems

Answer 9

• 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

Question 10

Cannon’s 4 Postulates of homeostasis

Answer 10

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

Question 11

Domino Effect

Answer 11

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

Question 12

Failure of Homeostasis - diseases

-2 types

Answer 12

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

Question 13

Homeostatic Response time

Homeostatic regulation of blood pressure

Answer 13

-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)

Question 14

Response loops of Homeostasis

• 3 components
• 7 step sequence

Answer 14

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

Question 15

Homeostatic receptors

Answer 15

• 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)

Question 16

Negative feedback

Answer 16

• 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)

Question 17

Set point and error signal definition

-Varying a set point (2 types)

Answer 17

• 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

Question 18

Types of control pathways (3)

Answer 18

• 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

Question 19

Positive Feedback

• definition
• e.g.

Answer 19

• 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

Question 20

Feed-forward Information

Answer 20

• 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