Chapter 1- RP

Definition of Physiology: The study of how the body functions at various organizational levels (e.g., cellular to organismal).
Key Areas for Reproductive Physiologists:
- Mechanisms of Mate Association: Investigates the physiological processes that help animals choose their mates.
- Control of the Annual Cycle of Reproduction: Examines the physiological mechanisms that induce animals to breed at specific times.
- Mechanisms of Function of Reproductive Cells and Organs: Analyzes how reproductive cells (sperm and egg) and organs (ovaries and testes) operate.
- Coordination of Reproductive Organs: Explores how reproductive cells and tissues are controlled by the endocrine and nervous systems.
- Delivery of Resources to Offspring: Looks at the physiological mechanisms regulating feeding and care provided to offspring.
- Physiology of the Young: Studies how offspring grow and develop to achieve sexual maturity.

Focus: Quantity and quality of offspring concerning parental energy investment.
r-selected Species:
- Characteristics: Short lifespans, early reproduction, single reproductive episode per lifetime.
- Energy Investment: High energy expended to produce many offspring.
- Parental Care: Minimal parental care results in high mortality rates for offspring.
K-selected Species:
- Characteristics: Longer lifespans, early reproduction, multiple reproductive episodes throughout life.
- Energy Investment: Significant energy devoted to nurturing a small number of offspring.
- Parental Care: Higher parental care reduces offspring mortality rates.

Focus: How gametes come together and how offspring develop and emerge.
Types of Reproduction:
- Oviparous: Fertilization occurs either internally or externally; offspring develop in eggs and subsequently hatch.
- Ovoviviparous: Fertilization is internal. Offspring develop in eggs that are retained within the mother, obtaining nutrition from the egg yolk.
- Viviparous: Fertilization occurs internally, and offspring develop inside the mother, receiving nutrients directly from her.
- Offspring Types:
- Precocial: Relatively self-sufficient shortly after birth.
- Altricial: Completely dependent on parents for survival.

Asexual Reproduction:
- Definition: Joining of gametes is not required; offspring are clones (genetically identical to each other and to the parent).
Sexual Reproduction:
- Definition: Gametes meet during fertilization; offspring are genetically distinct from both parents.

Concept: Enforces the idea that reproductive capability can last several years of an individual's lifetime.
Key Stages:
- Birth: Children are born sexually immature.
- Puberty: Marked by the achievement of sexual maturity.
- Adulthood: Individuals are reproductively fertile for a significant portion of their adult lives.
- Reproductive Senescence: Men and women experience gonadal failure (reproductive decline) in late middle age.

Definition: Describes the origin of germ cells.
Process:
- A fertilized egg develops into a zygote.
- Cell cleavages result in the production of embryonic stem cells.
Types of Stem Cells:
- Totipotent Stem Cells: Have the highest developmental potential; they can develop into any cell type.
- Significance: Isolation and culture of these cells offer potential therapeutic and research opportunities.
- Pluripotent Stem Cells: Derived from totipotent cells and capable of giving rise to germ layers (endoderm, ectoderm, and mesoderm). A subset of these becomes primordial germ cells, which are precursors to sperm and eggs.
- Multipotent Stem Cells: Found in mature tissues, their fate is typically committed to one cell type (e.g., a stem cell in bone marrow can only differentiate into a blood cell).

Influencing Factors: Gene expression cannot only be altered by changing nucleotide sequences; epigenetic modifications also play a significant role.
- Epigenetic Modifications: Changes that lead to differentiation of germ cells from other cell types.
- Methylation: The addition of methyl groups to DNA which silences gene expression.
- Euchromatin Structure: A tightly compacted state that also results in silenced gene expression.
- Histone Modifications: Acetylation and methylation of histones may either silence or enhance gene expression.

Purpose: The reproductive body facilitates the creation and fusion of gametes.
Components of the Reproductive Body:
- Genitalia and Copulatory Organs: Structures (e.g., penis or vagina) that enable physical transfer of gametes.
- Gonads: Organs (i.e., ovaries and testes) responsible for gamete production.
- Accessory Organs and Tissues: Support processes related to gamete production, pregnancy, childbirth, and lactation.

Definition of Hormones: Chemical substances released into the bloodstream that facilitate cell-to-cell communication.
Characteristics:
- Slower acting than neurotransmitters but often result in longer-lasting effects.
- Target cells possess specific receptors that hormones bind to for effect.
- Produced by endocrine cells or glands.
Functions: Regulate all aspects of reproduction, including:
- Sexual dimorphism (differences between male and female bodies).
- Production of gametes.
- Regulation of fertility and reproductive cycles.
- Processes of fertilization, gestation, birth, and lactation.

Hypothalamus and Pituitary Gland: These glands work in a coordinated manner to regulate many elements of the endocrine system.

Nature:
- Encoded by genes; stored in endocrine cells until release is necessary.
- Water-soluble, allowing them to circulate in blood plasma.
Mechanism of Action:
- Bind to surface receptors on target cells, activating rapid intracellular signaling pathways resulting in changes in cellular behavior.

Synthesis: All steroid hormones are derived from cholesterol.
Production and Release: Endocrine glands synthesize these hormones on demand and promptly release them into the bloodstream.
Mechanism of Action:
- Bind to intracellular receptors; their binding affects gene transcription.
- The resultant protein products alter the behavior of target cells.