Topic 5: Homeostasis and Response Flashcards
(28 cards)
What is homeostasis?
Homeostasis is the regulation of internal conditions of an organism to maintain optimum conditions for function, even when external conditions change.
What three parts are involved in control systems in the body?
Receptors detect stimuli → Coordination centres process the info (e.g. brain, spinal cord, pancreas) → Effectors produce a response (e.g. muscles that contract or glands that release hormones).
What is the role of the nervous system?
The nervous system enables humans to react to their surroundings and is coordinated by the central nervous system (CNS), made up of the brain and spinal cord.
What is the pathway of information through the nervous system?
Stimulus → Receptor → Coordinator (CNS) → Effector → Response
What is a reflex action?
A rapid, automatic response to a stimulus that doesn’t involve conscious thought.
What is the structure of the reflex arc?
Stimulus → Receptor → Sensory neurone → Relay neurone (in spinal cord) → Motor neurone → Effector → Response
What are synapses?
Gaps between neurones where chemicals (neurotransmitters) are released to pass the signal across.
How do you investigate the effect of caffeine on reaction times?
Use a ruler drop test to measure how quickly a person catches a falling ruler before and after drinking caffeine.
What are the variables for the caffeine reaction time experiment?
Independent - Whether or not caffeine is consumed.
Dependent - The reaction time (distance the ruler falls).
Control - Same person, same hand, same ruler, same conditions, time of day, etc.
How does caffeine affect the reaction time?
Caffeine speeds up reaction time by increasing the speed of nervous impulses.
What is the endocrine system?
A system made up of glands that secrete hormones into the blood to regulate body processes.
How do hormones travel in the body?
Hormones are carried in the bloodstream to target organs where they cause specific effects.
Where is the pituitary gland and what does it do? What is the example of negative feedback (thyroid)?
In the brain; it’s the “master gland” that controls other glands and releases several hormones.
If it detects low level of thyroxine, it releases TSH (thyroid stimulating hormone), which stimulates the thyroid to produce more thyroxine.
Where is the pancreas and what does it do?
Below the stomach; it regulates blood glucose by releasing insulin and glucagon.
Where is the thyroid gland and what does it do?
In the neck; it regulates the rate of metabolism by releasing thyroxine. This hormone plays an important role in growth and development.
Where are the adrenal glands and what do they do?
On top of the kidneys; they release adrenaline in response to stress. It increases our heart rate (blood bumps faster).
Where are the ovaries and what do they do?
In the female reproductive system; they release oestrogen and control the menstrual cycle.
Where are the testes and what do they do?
In the male reproductive system; they release testosterone (hormone) which controls puberty and sperm production.
How do insulin and glucagon work together?
They form a negative feedback cycle: insulin lowers blood glucose and glucagon raises it, maintaining balance.
What is Type 1 diabetes?
A condition where the pancreas produces little or no insulin. It’s usually genetic and treated with insulin injections.
What is Type 2 diabetes?
A condition where the body’s cells no longer respond properly to insulin. It’s often linked to lifestyle and treated with diet, exercise, and medication.
What is negative feedback in the context of homeostasis?
Negative feedback is a process where a change in a condition triggers a response that reverses the change, keeping conditions stable (e.g. blood glucose levels).
What happens when the blood glucose levels rise too high?
• The pancreas detects the increase and releases insulin.
• Insulin makes body cells take in glucose from the blood.
• It also causes the liver to convert glucose into glycogen for storage.
• This lowers blood glucose back to normal — completing the negative feedback loop.
What happens when blood glucose levels fall too low?
• The pancreas detects the fall and releases glucagon.
• Glucagon tells the liver to break down glycogen into glucose and release it into the blood.
• This raises the blood glucose level — again, completing the negative feedback loop.
