practice essay exam 1 Flashcards
hormonal regulation of male and female reproduction
Hormonal regulation in males start by hypothalamus releasing gonadotropin releasing hormone (GnRH). GnRH then stimulates the anterior pituitary to secrete FSH and LH. FSH binds to sustentacular cells causing them to release androgen binding hormone (ABP) which makes spermatogenic cells receptive to testosterone. LH binds with interstitial cells to release testosterone. Testosterone is the final trigger for spermatogenesis. Feedback on the hypothalamus and pituitary results from rising level of testosterone and inhibin.
Hormone interaction in female reproduction like males begins by hypothalamus releasing GnRH causing pituitary gland to release FSH and LH. Which triggers follicle growth and estrogen release. Estrogen release causes negative feedback lowering FSH and LH enhancing further estrogen output. Around day 14 LH surge causes ovulation to happen transforming ruptured follicle into corpus luteum. Which produces some inhibin, estrogen and progesterone decreasing LH and FSH inhibiting follicle development. If egg is not fertilized corpus luteum degenerates and ovarian hormone levels drop. The cycle starts anew.
action potential including ion movement, changes in Polarization, refractory periods
Action potential is a wave of depolarization that moves down the axon, triggering the release of neurotransmitters. This occurs when the Threshold Potential is reached. That happens when acetylcholine comes and binds with chemically gated sodium channel. Allowing sodium into the cell, down its concentration gradient, making inside the cell less negative. When the cell reaches –55mV the threshold is reached. All voltage-gated sodium channels open. Sodium rushes in bringing all neighboring channels to threshold. All the way down the axon to the axon terminal. Once the voltage inside the cell reaches +30mV sodium channels will close and potassium voltage gated channels will open. Allowing potassium into the cell, making it more negative and repolarizing it. As potassium channels slowly close allowing access potassium to leave the cell. The sodium/potassium pump works to move the ions to their original positions restoring the charge inside the cell to -70mV. After an action potential where it is impossible or hard to fire another action potential is called refractory period. An absolute refractory period is when no stimulus can initiate another action potential. The relative refractory period which happens after absolute refractory period can cause another action potential, but the stimulus must overcome hyperpolarization.
DNA replication
DNA replication happens in the nucleus of a cell. Inside, DNA is made up of a helix strand with a five-prime end and a three-prime end. They run in opposite directions. The enzyme helicase comes and unzips the original helix and splits it into two strands. DNA polymerase then makes a complimentary strand called the leading strand from the five-prime end to the three-prime end. Which only moves in one direction and continues to grow as the helix unzips. The other strand going in the opposite direction is called the lagging strand. It can only be made in small fragments called Okazaki fragments. The enzyme ligase then comes and connects the splices together.
protein synthesis
Protein synthesis is the creation of proteins. It involves two parts called transcription and translation. In transcription a copy of DNA is being made. DNA, which is a double stranded helix in the nucleus. Gets unzipped by an enzyme called RNA polymerase. DNA is now split into two strands called the template strand and coding strand. RNA polymerase then assembles RNA nucleotides complementary to the template strand making mRNA or messenger RNA. These nucleotides are read in sets of three called codon carrying the specific code for an amino acid. Once the stop codon is reached, mRNA gets sent out into the cytoplasm where it meets a ribosome and translation happens. In translation, mRNA attracts the complimentary anticodon of a tRNA carrying the appropriate amino acid binds together and adds its amino acid to the forming chain of protein until the stop codon is reached.
cell division
In cell division there are two steps called mitosis and cytokinesis. In mitosis there are four phases called prophase, metaphase, anaphase, and telophase. In prophase, the first step of mitosis. Chromatin is super coiled into chromosomes with sister chromatids, and the nucleolus is broken down. The spindle fibers grow from centrioles and dissolution of nuclear envelope occurs. In metaphase, the second part of mitosis. Chromosomes are aligned on the equator of the cell. Spindle fibers extend and attach to the centromere of each chromosome. In anaphase, the third step in mitosis spindle fibers pull DNA away. In the final stage of mitosis called telophase, DNA is put back as chromatin, reforming the nuclear envelope, and mitotic spindle is broken up. Cytokinesis then comes and divides the cytoplasm between the two newly formed cells, but not always.
