Human Endocrine System Overview

Thyroid and Metabolism

• Thyroid gland regulates metabolism by controlling calorie burning rate.
• Key hormones: triiodothyronine (T3) and thyroxine (T4).
• These hormones stimulate nutrient breakdown and increase energy production.

Adrenal Glands and Stress Response

• Adrenal glands respond to stress.
• Hormones released in response to stress: cortisol, adrenaline (epinephrine), and noradrenaline (norepinephrine).
• Cortisol regulates blood sugar.
• Adrenaline and noradrenaline prepare the body for "fight or flight" (increased heart rate, blood pressure, energy).

Female Reproductive System

• Internal Parts: Ovaries (egg and hormone production), fallopian tubes (egg transport), uterus (fetal development), cervix (connects uterus to vagina).
• Fertilization: Occurs in the fallopian tubes.
• Menstrual Cycle and Pain: Uterine contractions during menstruation cause abdominal pain. Hormonal changes (progesterone drop) also contribute.
• Follicle Development: Follicle-stimulating hormone (FSH) stimulates follicle growth and maturation in the ovaries.

Homeostasis and Feedback Mechanisms

• Homeostasis: maintaining a stable internal environment.
• Feedback mechanisms (like negative feedback loops) regulate various bodily functions (e.g., temperature, blood sugar, hormone production).

Nervous System in Homeostasis

• Nervous system plays a critical role in maintaining homeostasis and regulating feedback mechanisms.
• It integrates sensory information and sends signals to effectors to maintain stability.

  • Blood Pressure: Baroreceptors detect blood pressure changes, and the brain adjusts the sympathetic/parasympathetic nervous system to maintain balance. -Effectors: blood vessels constrict/dilate, and heart rate changes.

  • Fluid Balance: Osmoreceptors detect blood osmolarity changes, and the brain stimulates ADH release for water homeostasis. -Effectors: kidneys adjust water reabsorption.

DNA Replication Enzymes

• Helicase: unwinds DNA.
• Primase: synthesizes RNA primers.
• DNA Polymerase: synthesizes new DNA strands.
• Ligase: seals gaps between DNA segments (Okazaki fragments).

Types of RNA

• mRNA (messenger RNA): Carries genetic information from DNA to ribosomes for protein synthesis.
• tRNA (transfer RNA): Brings amino acids to ribosomes.
• rRNA (ribosomal RNA): Forms ribosomes and plays a structural role in protein synthesis.

DNA Replication Errors

• Point mutations: single nucleotide changes (substitutions, insertions, deletions).
• Frameshift mutations: insertions or deletions changing the reading frame.
• Chromosomal mutations: changes in chromosome structure or number.

Central Dogma of Molecular Biology

• DNA → RNA → Protein

Types of Mutations and Effects

• Point mutations: silent, missense, or nonsense; affects protein function.
• Frameshift mutations: often result in nonfunctional proteins.
• Chromosomal mutations: can alter gene expression, cause cancer, or lead to birth defects.

UV Radiation and Mutations

• UV radiation damages DNA by forming pyrimidine dimers.
• Damaged DNA can trigger error-prone repair mechanisms during DNA repair, causing mutations.
• UV radiation directly alters DNA bases, leading to mutations.

Antibiotic Resistance

• Antibiotic resistance develops when bacteria mutate to resist antibiotics' effect.
• Mutations can alter the antibiotic's target, reducing its effectiveness (e.g., beta-lactamase resistance).

Fossils and Evolution

• Fossils document the chronology of life on Earth.
• Transitional fossils show characteristics of both ancestral and descendant species (e.g., Tiktaalik: fish to tetrapod).

Homologous vs. Analogous Structures

• Homologous structures: shared ancestry (e.g., vertebrate forelimbs - human arms, bird wings, whale flippers).
• Analogous structures: similar function evolved independently (e.g., bird wings and insect wings).

DNA/Amino Acid Sequence

• DNA sequence determines the amino acid sequence of proteins.
• Amino acid sequence forms the primary structure and subsequently determines protein shape and function.

Embryological Development

• Fertilized egg develops into a mature organism through cell division, differentiation, and morphogenesis.
• Comparative embryology unveils shared evolutionary history evidenced by similar embryonic structures in various vertebrate species (e.g., notochord, somites, pharyngeal arches).

Male Puberty Hormones

1. Testosterone: Produced by testes, responsible for secondary sexual characteristics (hair, voice, muscle mass, genitals growth).
2. Luteinizing Hormone (LH): Produced by pituitary gland, stimulates testosterone production.
3. Follicle-Stimulating Hormone (FSH): Produced by pituitary gland, stimulates sperm development.

Pregnancy Hormones

1. Human Chorionic Gonadotropin (hCG): Maintains pregnancy by stimulating progesterone production.
2. Progesterone: Prepares uterus and supports embryonic development.
3. Estrogen: Maintains pregnancy, stimulates uterine and breast growth, and prepares cervix for labor.
4. Oxytocin: Stimulates uterine contractions and milk letdown.

Lactation Hormones

1. Prolactin: Stimulates milk production.
2. Oxytocin: Stimulates milk release.

Pancreas and Diabetes

• Pancreas: produces digestive enzymes and hormones (insulin, glucagon).
• Insulin: lowers blood sugar by facilitating glucose uptake.
• Glucagon: raises blood sugar by stimulating glycogen breakdown.
• Diabetes: occurs when the body cannot produce or use insulin effectively, resulting in high blood sugar.

Menstrual Cycle Stages

1. Menstruation: Uterine lining shedding (Days 1-5).
2. Follicular phase: Follicle growth (Days 6-14).
3. Ovulation: Egg release (Day 14).
4. Luteal phase: Uterine lining preparation (Days 15-28).

Ovulation Trigger

• Luteinizing hormone (LH) triggers ovulation.

Progesterone Function

• Progesterone: Thickens uterine lining for implantation and maintains pregnancy.

Irregular Menstrual Periods

• Causes: Hormonal imbalances, stress, weight changes, PCOS, thyroid disorders.

Complementary Base Pairing

• Nucleotides (A-T, G-C) pair to form DNA's double helix.

Mutations and Complementary Base Pairing

• Mutations (point, frameshift, chromosomal) occur during DNA replication or repair.
• Complementary base pairing safeguards the genetic code during DNA replication. DNA polymerase ensures accurate base pairing.

DNA Structure and Evolution

• DNA structure (universal genetic code, sequence similarities, vestigial genes) reflects evolutionary history.

Evidences of Evolution

• Fossil record, comparative anatomy, molecular biology (DNA/protein similarities), biogeography all support the theory of evolution.