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Roles of Hormones

• Estrogen:  There are several types of estrogen (estrone, estradiol, estriol).  Estradiol is the most potent during reproductive years.  Beyond the menstrual cycle and reproductive development, estrogen influences bone density, cholesterol levels, cognitive function, and cardiovascular health.  Estrogen's impact on the menstrual cycle includes thickening the uterine lining, regulating the release of LH and FSH (follicle-stimulating hormone), and contributing to the development of secondary sexual characteristics.

• Progesterone:  This hormone works synergistically with estrogen.  Its key roles include preparing the endometrium (uterine lining) for implantation of a fertilized egg, maintaining pregnancy by suppressing uterine contractions, and contributing to breast development.  During the menstrual cycle, progesterone levels rise after ovulation, supporting the potential for pregnancy.  If pregnancy doesn't occur, progesterone levels drop, leading to menstruation.

• Testosterone:  While primarily known for its role in male development, testosterone also plays a role in women, albeit at much lower levels.  It influences muscle mass, bone density, libido, and energy levels in both sexes.  In men, testosterone is crucial for sperm production, development of secondary sexual characteristics (facial hair, deeper voice), and maintaining muscle mass and strength.

• Adrenaline (Epinephrine):  This is a key player in the "fight-or-flight" response, part of the sympathetic nervous system.  Its release leads to increased heart rate, blood pressure, respiration, and glucose mobilization, preparing the body for immediate action.  It's crucial for survival in stressful situations.

• Thyroxine (T4): This is the primary thyroid hormone. It regulates metabolism, affecting nearly every cell in the body.  It controls the rate at which the body uses energy (basal metabolic rate), influencing growth, development, and body temperature.  Deficiencies lead to hypothyroidism, while overproduction leads to hyperthyroidism.

• Insulin: This hormone, produced by the pancreas, regulates blood glucose levels.  After meals, insulin facilitates the uptake of glucose from the blood into cells for energy storage or use.  Without sufficient insulin, glucose accumulates in the blood, leading to hyperglycemia, a hallmark of diabetes.

• Cortisol:  The primary stress hormone, produced by the adrenal glands.  Cortisol regulates metabolism, blood pressure, immune response, and inflammation.  It plays a vital role in the body's response to stress, but chronic high levels can negatively impact health.

• Oxytocin:  Often called the "love hormone," it's involved in social bonding, trust, and empathy.  It also plays a crucial role in childbirth (stimulating uterine contractions) and lactation (milk ejection).

• LH (Luteinizing Hormone):  This gonadotropin is crucial for reproductive function in both sexes.  In females, it triggers ovulation and the formation of the corpus luteum, which produces progesterone. In males, LH stimulates the Leydig cells in the testes to produce testosterone.

Female Reproductive System Diseases

• PMS (Premenstrual Syndrome):  Symptoms can vary widely, but common ones include mood swings, irritability, bloating, breast tenderness, fatigue, and headaches.  The exact cause is unclear, but hormonal fluctuations likely play a significant role. Treatment focuses on managing symptoms, often with lifestyle changes (diet, exercise, stress reduction) and sometimes medication.

• PCOS (Polycystic Ovary Syndrome):  Characterized by hormonal imbalances leading to irregular periods, cysts on the ovaries, and elevated androgen levels.  This can lead to infertility, weight gain, acne, and hirsutism (excess hair growth).  Treatment involves managing symptoms, promoting ovulation (for those wishing to conceive), and addressing related health issues.

• Endometriosis:  This condition involves the growth of endometrial tissue (uterine lining) outside the uterus.  This tissue responds to hormonal changes, causing inflammation, pain, and potentially infertility.  Treatment options include pain management, hormonal therapy, and sometimes surgery.

• Gonorrhea:  A bacterial STI that can infect the genitals, rectum, and throat.  Early stages might be asymptomatic, but untreated gonorrhea can lead to serious complications, including PID (pelvic inflammatory disease) in women and infertility.  Treatment involves antibiotics.

• HPV (Human Papillomavirus):  A common viral STI with many strains.  Most infections clear on their own, but some high-risk strains can cause genital warts and cervical cancer.  Vaccination is available to prevent infection.  Regular Pap smears are crucial for early detection of cervical cancer.

• Syphilis:  A bacterial STI that progresses through stages if untreated.  Early stages may involve painless sores, but later stages can cause serious damage to the heart, brain, and nervous system.  Treatment involves antibiotics.

Homeostasis & Feedback Mechanism

• Negative feedback: Maintaining body temperature is a prime example. If body temperature rises, the hypothalamus signals for sweating and vasodilation (widening of blood vessels) to cool the body.  If temperature falls, shivering and vasoconstriction (narrowing of blood vessels) occur to generate and conserve heat.  Blood glucose regulation (through insulin and glucagon) is another key example.

• Positive feedback: Childbirth is a classic example.  The baby's head pushing against the cervix stimulates oxytocin release, causing more uterine contractions, leading to further pressure on the cervix and intensifying the cycle until birth.  Blood clotting is another example where the initial clot formation triggers further clotting until the bleeding stops.

Parts of the Brain

• Cerebrum: This is further divided into lobes (frontal, parietal, temporal, occipital) each with specialized functions.  The frontal lobe is associated with higher-level cognitive functions, planning, decision-making, and personality. The parietal lobe processes sensory information (touch, temperature, pain). The temporal lobe is involved in hearing, memory, and language comprehension. The occipital lobe processes visual information.

• Cerebellum:  Besides coordination and balance, the cerebellum plays a role in motor learning and some cognitive functions.

• Brainstem: This includes the midbrain, pons, and medulla oblongata, controlling vital functions like breathing, heart rate, blood pressure, and sleep-wake cycles.

• Hypothalamus: This acts as a link between the nervous and endocrine systems, regulating the pituitary gland and influencing hormone release.

• Thalamus: This acts as a relay station for sensory information, filtering and directing it to appropriate areas of the cerebrum.  It's also involved in sleep regulation.  Other key structures include the hippocampus (memory), amygdala (emotions), and basal ganglia (movement).

Neurons (How Messages Travel in the Nervous System)

• Resting potential:  The neuron's membrane maintains a negative charge inside compared to the outside.  This is due to the unequal distribution of ions (sodium, potassium, chloride) across the membrane, maintained by ion pumps.

• Action potential:  A stimulus (chemical, electrical, or mechanical) causes depolarization.  Sodium channels open, allowing sodium ions to rush into the neuron, making the inside more positive.  This creates an electrical signal that propagates down the axon.

• Neurotransmitter release:  When the action potential reaches the axon terminal, it triggers the release of neurotransmitters into the synaptic cleft (gap) between neurons.

• Signal transmission:  Neurotransmitters bind to receptors on the postsynaptic neuron, triggering either excitation (depolarization) or inhibition (hyperpolarization) depending on the neurotransmitter and receptor type.  This process allows for complex integration of signals in the nervous system.  The process is crucial for all neural communication, forming the basis for sensory perception, motor control, and higher cognitive functions.

Sympathetic & Parasympathetic Nervous Systems 

The sympathetic and parasympathetic systems often work antagonistically to maintain balance:

• Sympathetic Nervous System:  The neurotransmitters involved are primarily norepinephrine and epinephrine.  Effects include: increased heart rate and force of contraction, increased blood pressure (vasoconstriction in most organs, vasodilation in skeletal muscles), bronchodilation (widening of airways), increased blood glucose, and pupil dilation.  The body is primed for action.

• Parasympathetic Nervous System:  The primary neurotransmitter is acetylcholine.  Effects include: decreased heart rate, decreased blood pressure (vasodilation), bronchoconstriction, increased digestive activity (peristalsis and secretions), and pupil constriction.  The body is in a relaxed state, focusing on digestion and rest.

DNA Replication, Transcription, and Translation 

• DNA Replication:  This semi-conservative process involves unwinding the DNA double helix, using each strand as a template to synthesize a new complementary strand.  Enzymes like DNA polymerase play a vital role in adding nucleotides to the new strand.  This ensures accurate duplication of the genetic information.

• Transcription:  RNA polymerase binds to a specific region of DNA (promoter) and synthesizes a complementary mRNA molecule.  The mRNA molecule then undergoes processing (splicing) to remove introns (non-coding regions) and retain exons (coding regions).

• Translation:  The mRNA molecule travels to a ribosome, where it's read in codons (three-nucleotide sequences).  tRNA (transfer RNA) molecules bring specific amino acids to the ribosome based on the mRNA codon sequence.  The ribosome links amino acids together to form a polypeptide chain, which folds into a functional protein.

Mutation & Types of Point Mutation

• Point mutations:  These are alterations affecting a single nucleotide.  They can have various effects:

• Silent mutation: The change in nucleotide doesn't alter the amino acid sequence (due to the redundancy of the genetic code).

• Missense mutation:  The change alters a single amino acid. The impact can vary widely depending on the amino acid replaced and its location in the protein. It can lead to a non-functional protein or have minimal effect.

• Nonsense mutation: The change introduces a premature stop codon, resulting in a truncated and usually non-functional protein.

• Frameshift mutation (insertion or deletion):  These mutations shift the reading frame of the codons, altering the amino acid sequence downstream from the mutation point.  The effect is usually substantial, leading to a non-functional protein.

Biodiversity & Evidence of Evolution

Biodiversity refers to the variety of life on Earth. Evidence for evolution includes:

• Fossil Record: The fossil record provides a chronological sequence of life forms, showing transitions and changes over millions of years. The discovery of transitional fossils (fossils that show intermediate forms between ancestral and descendant species) is strong evidence of evolution. For example, the fossil record documents the evolution of whales from land-dwelling mammals.

• Geologic Time Scale: Correlating the fossil record with the geologic time scale, which is based on the layering of rocks and radioactive dating, provides a framework for understanding the timing and sequence of evolutionary events. This allows scientists to estimate the age of fossils and understand the history of life on Earth.

• Comparative Anatomy: Homologous structures (similar structures in different organisms with a common ancestor, such as the forelimbs of vertebrates) and vestigial structures (remnants of structures that served a purpose in ancestors but are now reduced or functionless, such as the human appendix) provide strong evidence of common ancestry. Analogous structures (structures with similar functions but different evolutionary origins) highlight convergent evolution, where unrelated species develop similar traits due to similar environmental pressures.

• Embryonic Development: Comparing the embryonic development of different species reveals similarities that suggest common ancestry. Many vertebrates, for example, exhibit gill slits and tails during early embryonic stages, even if those structures don't fully develop in the adult forms.

• Amino Acid Sequences: Comparing the amino acid sequences of proteins in different species reveals similarities that indicate evolutionary relationships. The more similar the amino acid sequences, the more closely related the species are likely to be. This molecular evidence complements anatomical and fossil evidence.