Biology paper 2-Homeostasis

Homeostasis

• Definition: The regulation of internal conditions in cells or organisms to ensure optimal conditions for function.

• Responses: Adjusts to both internal and external changes in the environment.

• Maintains conditions for:

  • Enzyme action: Enzymes function within specific temperature and pH ranges.

  • Cellular activities.

Key Areas of Homeostasis in the Human Body

1. Blood glucose concentration: Maintains steady glucose supply for respiration, preventing high/low blood sugar levels.

2. Body temperature: Keeps optimal temperature (~37°C) for enzyme efficiency.

3. Water levels: Balances water intake and loss to avoid dehydration/overhydration.

Automatic Control Systems

• Mechanism: Homeostasis uses automatic control systems via:

  • Nervous responses (e.g., reflex actions).

  • Chemical responses (e.g., hormones like insulin).

Components of Control Systems

1. Receptors: Specialized cells detecting stimuli (changes in temperature, glucose, etc.).

2. Coordination centres: Structures (brain, spinal cord, pancreas) processing receptor info.

3. Effectors: Muscles or glands responding to restore optimal conditions (e.g., shivering to raise temperature).

Key Points

• Homeostasis is essential for efficient vital processes.

• The nervous and endocrine systems play crucial roles in maintaining balance.

Structure and Function of the Nervous System

1. Function: Enables reactions to surroundings and coordinates behavior.

2. Components:

• Receptors: Detect stimuli (light, temperature, pressure).

• CNS: Includes brain and spinal cord; processes info from receptors; coordinates response.

• Effectors: Muscles (movement) and glands (hormone secretion).

Flow of Information

• Pathway: Stimulus → Receptor → Coordinator → Effector → Response.

• Stimulus: Change in environment.

• Receptor: Detects change.

• Coordinator: CNS processes info.

• Effector: Performs response.

• Response: Action addressing stimulus.

Reflex Arc

• Definition: Pathway involved in rapid reflex actions, bypassing conscious thought.

  1. Sensory neurone: Transmits impulse from receptor to CNS.

  2. Relay neurone: Links sensory to motor neurone in the spinal cord.

  3. Motor neurone: Carries impulse from CNS to effector.

  4. Synapse: Gap between neurones for chemical signal transmission.

Importance of Reflex Actions

• Rapid: Protect body from harm (e.g., quick withdrawal from hot surfaces).

• Involuntary: Ensures faster responses without conscious thought.

Required Practical Activity 6: Investigating Reaction Time

1. Aim: Measure how a factor (e.g., caffeine, distraction) affects human reaction time.

2. Method: Use a ruler drop test or reaction time apps.

3. Variables:

• Independent: Investigated factor (e.g., caffeine).

• Dependent: Reaction time.

• Control: Conditions like hand used, ruler size, environment.

4. Data Analysis:

• Collect and average results to identify trends.

• Present data in numerical and graphical forms.

5. Conclusion: Determine factor influence on reaction time.

The Endocrine System

• Definition: Composed of glands secreting hormones into the bloodstream.

• Hormones: Chemical messengers affecting target organs.

• Compared to Nervous System: Slower acting, longer lasting effects.

Key Glands and Their Roles

1. Pituitary gland: The 'master gland'; regulates other glands & processes by releasing hormones.

2. Pancreas: Produces insulin for blood glucose regulation.

3. Thyroid: Releases thyroxine to control metabolic rate and temperature.

4. Adrenal glands: Produce adrenaline for 'fight or flight' response.

5. Ovaries (females): Produce oestrogen and progesterone regulating menstrual cycle/characteristics.

6. Testes (males): Produce testosterone for sperm production and male characteristics.

Hormonal Control by the Pituitary Gland

• Function: Monitors body conditions and releases hormones triggering other glands (e.g., TSH stimulates thyroid).

Locating Glands in the Human Body

• Pituitary gland: Base of brain.

• Pancreas: Below stomach.

• Thyroid: Neck, below larynx.

• Adrenal glands: Above kidneys.

• Ovaries: Lower abdomen in females.

• Testes: Scrotum in males.

Key Differences: Nervous vs. Endocrine Systems

Control of Blood Glucose Concentration

• Importance: Essential for energy balance.

• Role of Pancreas: Monitors and controls glucose concentration.

High Blood Glucose Levels

• Pancreas releases insulin to:

  • Increase glucose uptake by cells.

  • Convert excess glucose into glycogen.

Low Blood Glucose Levels (HT only)

• Pancreas releases glucagon to:

  • Break down glycogen into glucose.

• Negative feedback: Insulin and glucagon maintain stable glucose levels.

Diabetes

• Type 1 Diabetes: Pancreas lacks insulin production; high blood glucose levels; requires insulin injections.

• Type 2 Diabetes: Body cells do not effectively respond to insulin; managed through diet and exercise.

Key Concepts: Negative Feedback Cycle (HT only)

• Insulin and glucagon stabilize blood glucose.

• Graph Interpretation:

  • Analyze blood glucose changes and treatment effects.

Hormones in Human Reproduction

• Role: Hormones control puberty to menstrual cycle.

Puberty Changes

• Hormonal Changes influence secondary sexual characteristics:

  • Females: Breasts, wider hips, menstruation.

  • Males: Increased muscle mass, deeper voice, facial hair.

Female Reproductive Hormones

1. Oestrogen: Regulates reproductive system and egg maturation.

2. Progesterone: Prepares uterus for pregnancy and maintains uterine lining.

Male Reproductive Hormones

1. Testosterone: Stimulates sperm production and male characteristics.

The Menstrual Cycle

• Monthly cycle preparing for pregnancy (28 days).

1. FSH: Stimulates egg maturation.

2. LH: Triggers ovulation.

3. Oestrogen/Progesterone: Maintains uterine lining after ovulation.

Menstrual Cycle Phases

1. Day 1-5 (Menstrual Phase): Shedding of uterine lining due to low hormones.

2. Day 6-14 (Follicular Phase): FSH increases oestrogen, thickening lining.

3. Day 14 (Ovulation): LH peak triggers egg release.

4. Day 15-28 (Luteal Phase): Corpus luteum secretes progesterone; drop indicates menstruation.

Hormonal Interactions** (HT only)

• Graphs: Analyze hormone levels throughout menstrual cycle:

  • FSH rises, peaks before ovulation; LH peaks sharply; oestrogen and progesterone fluctuate.

Contraception

• Definition: Methods controlling fertility and preventing pregnancy.

Hormonal Methods of Contraception

1. Oral Contraceptives: Inhibit FSH, preventing egg maturation.

2. Injection, Implant, Patch: Slow-release progesterone to inhibit egg maturation.

3. IUDs: Can prevent implantation or release hormones to inhibit ovulation.

Non-Hormonal Methods

1. Barrier Methods: Condoms, diaphragms preventing sperm entry.

2. Spermicidal Agents: Chemicals killing sperm.

3. Abstinence: Avoiding intercourse during ovulation.

4. Surgical Methods: Permanent sterilization (vasectomy/tubal ligation).

Evaluation of Contraceptive Methods

• Factors to consider:

  • Effectiveness, duration of protection, side effects, accessibility, cost, and impact on menstrual cycle.

Use of Hormones to Treat Infertility (HT only)

• Modern technologies use hormones for infertility treatment.

Hormonal Treatments for Infertility

1. Fertility Drugs: Use FSH and LH to stimulate egg maturation and ovulation.

2. IVF: Steps include hormonal stimulation, egg collection, fertilization, embryo development, and transfer.

Technological and Ethical Considerations

1. Advancements improve IVF success (imaging).

2. Social/Ethical Issues: Consider stress, low success rates, and accessibility.

Feedback Systems (HT Only)

• Adrenaline: Produced in stress, triggers fight or flight, increasing heart rate and blood flow.

• Thyroxine: Secreted by the thyroid, controlling metabolism; regulated by negative feedback for stable levels.

Interpreting Diagrams of Negative Feedback

• Components:

  • Sensors, control centers, and effectors; arrows indicating stimulation/inhibition.

Inheritance, Variation, and Evolution

Key Concepts

1. Meiosis: Reduces chromosome number for gametes, ensuring genetic diversity.

2. Mutations: Changes in DNA affecting fitness, driving variation in populations.

3. Natural Selection: Variation leads to survival and reproduction; significant evolutionary changes occur over time.

4. Selective Breeding: Enhances traits in plants and animals, influencing genetic diversity.

5. Cloning: Produces identical individuals; various methods used in plants and animals.

6. Genetic Engineering: Transfers genes for desired traits; raises ethical/environmental concerns.

Ethical and Social Implications

• Selective Breeding: Reduces genetic diversity; may lead to health problems.

• Cloning: Ethical concerns over genetic uniformity.

• Genetic Engineering: Debates around safety, ethics, and unintended effects.

Reproduction

Sexual vs Asexual Reproduction

1. Sexual: Combines genetic material, creating diversity; involves meiosis.

2. Asexual: Identical clones; fast and efficient.

Comparison of Meiosis and Mitosis

DNA and the Genome

1. Structure of DNA: Double helix, organized into chromosomes.

2. Genes: Segments of DNA coding for proteins.

3. Genome: Complete genetic material of an organism.

Real-World Applications

• Personalized medicine, gene therapy, ancestry tracing.

Genetic Inheritance

Key Terminology

1. Gamete: Sex cells with half chromosome number.

2. Allele: Different forms of the same gene.

3. Dominant/Recessive Alleles: Expressed traits; homozygous and heterozygous conditions.

4. Genotype/Phenotype: Genetic makeup vs physical traits.

Concepts

1. Single Gene Traits: Controlled by single genes.

2. Multiple Genes: Most traits result from interactions of multiple genes.

3. Punnett Squares: Predict genetic crosses and probabilities of traits.

Key Disorders

1. Polydactyly: Dominant allele condition.

2. Cystic Fibrosis: Recessive allele condition.

Ethical and Social Issues: Embryo Screening

1. Advantages: Prevention of inherited disorders.

2. Disadvantages: Ethical concerns and discrimination risks.

Sex Determination

Human Sex Chromosomes

• Chromosome combinations determine sex: XX (female), XY (male).

• Genetic cross example: Parents' sex chromosomes predict offspring sex ratios (1:1).

Variation and Evolution

1. Definition: Changes in inherited characteristics over time.

2. Natural Selection: Individuals with advantageous traits survive and reproduce.

Selective Breeding

1. Definition: Intentional breeding for specific traits; impacts agriculture and domestication.

2. Impacts: Both positive (improved productivity) and negative (increased disease susceptibility).

Genetic Engineering

1. Definition: Modifying an organism's genome for desired traits.

2. Applications: Agriculture (GM crops), medicine (insulin).

Evidence for Evolution

• Fossils provide historical life records; antibiotic resistance shows natural selection.

Fossils

• Ancient organisms in sedimentary rock; preservation methods; challenges in fossil record completion.

Extinction

• Causes include environmental changes and human activity.

Resistant Bacteria

• Rapid evolution of bacteria leading to antibiotic resistance; prevention strategies include appropriate prescribing practices and completing courses.