Homeostasis Flashcards
What is the definition of homeostasis?
when the body maintains a stable dynamic equilibrium, (stable internal environment)
What is the response pathway what are the different stages?
stimulus response pathway = change in the environment
1. receptors
2. sensory nervous pathway
3. CNS (spinal cord + brain)
4. motor nervous pathway
5. effector
6. response (to the stimulus)
What is the definition of a stimulus?
change in internal/external environment (environmental stress)
What is the definition of a response?
a change in behaviour/physiology as a result of the change in the environment
How does a negative feedback loop work?
reversal of any change in the internal environment to return to an optimum steady state
How does the negative feedback loop work?
- change away from the optimum (either an increase or decrease)
- sensory receptors detect change
- communication system informs effector
- effector reacts to reverse change
- return to optimum conditions
What are the structures required for a negative feedback loop to work?
- sensory receptors (to detect change)
- communication system = CNS
- effector cells (to create change back to optimum)
How does a positive feedback loop work?
increase in any change away from the optimum, does NOT lead to homeostasis
How does the positive feedback loop work?
- change from the optimum (increase or decrease)
- receptors detect change
- communication systems inform effectors
- effectors react to increase change
- levels return to normal
What is the definition of thermoregulation?
maintenance of relatively constant core body temperature to maintain optimum enzyme activity
What is meant by radiation?
the transmission of electromagnetic waves to and from the air, water and ground
What is meant by convection?
the heating and cooling by currents of air/water to set up convection currents within the organism
What is meant by conduction?
heating up as a result of the collision of molecules
What is the definition of an ectotherm?
their body temperature fluctuates with external temperature (cold blooded)
What are the adaptations of ectotherms? (behavioural)
- expose body to the sun (basking)
- hid/ avoid sun or they burrow underground to cool down
- alter body shape to up or down S.A
- increase breathing movements = pants
What is the advantages of being an ectotherm?
- use less food in respiration
- grows quickly (greater proportion of energy used for growth)
What are the disadvantages of being an ectotherm?
- locations in the globe are minimised
- less active during the cooling temps, not capable of activity during winter
What is the definition of an endotherm?
maintain body temp within strict limits using energy, warm blooded
- independent of external body temp
What are the adaptations of endotherms?
- sweat gland
- blood vessels
- panting
- skeletal muscles shivering
What are the advantage’s of being an endotherm?
- constant body temp
- activity people even when cool
- inhabit colder parts of the planet
What are the disadvantages of being an endotherm?
- energy used up to maintain constant body temp
- more food required
- less energy used in growth
What is the heat loss centre?
activated when the temp of blood flowing through hypothalamus increases
What is the heat gain centre?
activated when the temp of blood flowing through the hypothalamus decreases
How is the blood pressure returned to normal when there is an increase in the blood temperature, detected by the skin?
impulse is sent via the motor neurones, detected by thermoregulators in the heat loss centre of hypothalamus
- vasodilation, increased blood flow
- increased sweating
- skin hairs lowered
- decrease in metabolic rate
