Homeostatis And Response Flashcards
What is homeostasis?
The regulation of internal conditions to maintain a stable environment for cells to function.
Examples of controlled conditions
- Blood glucose levels.
- Body temperature.
- Water levels.
What are the components of control systems?
Receptors: Detect changes (stimuli).
2. Coordination centres: Process information (e.g., brain, spinal cord, pancreas).
3. Effectors: Muscles or glands that respond.
What is negative feedback?
A process that restores a system to its optimum level when conditions change.
Example: Blood glucose regulation.
What is the nervous system?
A system that uses electrical signals to respond to stimuli.
Key parts:
1. Central Nervous System (CNS): Brain and spinal cord.
2. Peripheral Nervous System: Nerves.
What is a reflex action?
An automatic, rapid response to a stimulus, bypassing the brain to protect the body.
Pathway of nervous system
Stimulus → Receptor → Sensory neuron → Relay neuron → Motor neuron → Effector → Response.
How do synapses work?
Electrical signals are transmitted across gaps between neurons (synapses) by chemicals (neurotransmitters).
What is the endocrine system?
A system of glands that secrete hormones into the bloodstream to regulate body processes.
Key glands
- Pituitary gland: Master gland, controls other glands.
- Pancreas: Controls blood glucose.
- Thyroid: Regulates metabolism.
- Adrenal glands: Produces adrenaline.
How is blood glucose regulated?
• High glucose: Pancreas releases insulin, causing cells to absorb glucose or store it as glycogen in the liver.
• Low glucose: Pancreas releases glucagon, converting glycogen back to glucose.
What is diabetes?
• Type 1: Pancreas doesn’t produce insulin. Treated with insulin injections.
• Type 2: Cells stop responding to insulin. Treated with diet, exercise, or medication.
How is body temperature controlled?
By the thermoregulatory centre in the brain.
Responses to heat:
- Sweat (evaporation cools skin).
- Vasodilation (more blood flow near skin).
Responses to cold:
- Shivering (muscle contractions generate heat).
- Vasoconstriction (less blood flow near skin).
What is the role of the kidneys?
Filter the blood to:
1. Remove waste (e.g., urea).
2. Control water levels.
Key process:
• Selective reabsorption: Useful substances like glucose are reabsorbed, while excess water, ions, and urea form urine.
What is ADH and its role?
Antidiuretic hormone (ADH) regulates water levels by controlling the permeability of kidney tubules.
• Low water levels: More ADH → More water reabsorbed.
• High water levels: Less ADH → Less water reabsorbed.
What is osmosis and why is it important in homeostasis?
Osmosis is the movement of water from a dilute solution to a concentrated solution across a semi-permeable membrane. It helps balance water levels in cells.
What are the stages of the menstrual cycle?
- Day 1-4: Uterus lining breaks down (period).
- Day 5-14: Lining thickens to prepare for an egg.
- Day 14: Ovulation (egg released).
- Day 15-28: If no fertilisation, lining breaks down again.
What hormones control the menstrual cycle?
- FSH (Follicle-Stimulating Hormone): Matures the egg.
- LH (Luteinising Hormone): Triggers ovulation.
- Oestrogen: Repairs uterus lining.
- Progesterone: Maintains uterus lining.
What are hormonal contraceptives?
Methods like the pill or implant that use hormones to prevent ovulation.
Non-hormonal methods: Condoms, diaphragms, sterilisation.
What are plant hormones and their uses?
• Auxins: Control growth.
• Used in rooting powders and weed killers.
• Gibberellins: Stimulate germination.
• Ethene: Ripens fruit.
