MCAT BIO

what is the cell

• a compartmentalized, organized, and well-oiled machine that can undergo various life processes

  • compartmentalized: split into organelles (eukaryotes)

    • prokaryotes are a soupy mix of genetic information and life-producing capacity

  • organized: each process occurs in a controlled manner (positive & negative feed backs)

  • well-oiled: processes are fluid, flows from one to the next

what is the cell theory

1. all living things are made up of cells

2. cells are the basic functional unit of life

3. cells form from pre-existing cells

4. cells carry genetic info (DNA!) that they pass onto daughter cells

what makes a virus not living?

• it breaks rules 3 and 4 of the cell theory

  • a virus cant reproduce on their own and need a cell host

  • a virus cant pass on genetic code to their daughters; but rather, must inject the code into cell hosts which are naturally programmed to run it through the cell cycle

    • the injected genetic material then either lays dormant within the cell (lysogenic) or spreads throughout the body (lytic)

why do cells only pass on DNA to daughter cells and not RNA

1. RNA is meta-stable

   • it closes in on itself by folding and is unable to be used after a while

2. RNA is unable to be passed on

   • only viruses can pass it on, not eukaryotes or prokaryotes

what are the main differences between eukaryotes and prokaryotes

• EUK (eukarya)

  • has membrane-bound organelles

  • can be single (yeast) and multi-cellular (humans)

• PRO (bacteria & archaea)

  • essentially one big organelle

  • no nucleus

  • only single celled

what is the nucleus

• control center (HQ) of the entire cell

• contained inside a semi-permeable double membrane

  • sign of importance; protection

  • has nuclear pores which allow for communication and travelling in and out of the cell

• has tightly wound DNA inside (negative charged)

  • this is wrapped around histone proteins

    • made up of amino acids (basic building blocks of proteins) that have +1 charged R groups

what is the difference between heterochromatin and euchromatin

• Heterochromatin

  • compact/tight form of DNA

• Euchromatin

  • loose/relaxed form of DNA

• Histone Acetylation

  • the act of neutralizing a positive histone protein by attaching an acetyl group to each of its terminals

  • this undoes the tightly wound DNA which needs to happen before replication of the cell

    • hetero → eu

what is the mitochondria

• the powerhouse of the cell where almost all the effective energy of the cell (ATP) is produced by the electron transport chain (ETC)

• has its own genes and is able to self-replicate

• has an outer and inner membrane (double protected)

• contains cristae

  • grooved folds of the inner membrane that increase surface area for ETC to work with

  • each groove fits more proteins for energy (cellular respiration)

    • coastline paradox

• is able to kickstart apoptosis

  • the controlled programming of cell death when something goes wrong

  • different from necrosis which is uncontrolled

what are lysosomes

• organelles that contain many hydrolytic enzymes used to break down material

  • lysozymes~ recycling centers

  • these enzymes are different from vesicles which are like boxes used to transport materials

• derived from “lysis” meaning to break

what are the smooth and rough endoplasmic reticulums (SER & RER)

• ROUGH

  • studded with ribosomes

    • factory machines for protein synthesis

    • necessary for EVERYTHING

• SMOOTH

  • lacks ribosomes

  • helps transport proteins from RER to Golgi

  • synthesizes lipids (fats/oils/waxes/etc.)

  • detoxes drugs by making them hydrophilic (attracted to water)

    • primary site for first pass metabolism which is the processes of allowing toxins to be dissolved in the blood in order to be excreted through the kidneys as urine

      • liver’s job

what is the golgi apparatus

• stack of membrane-bound “sacs”

• modify proteins to make them more efficient in their roles

  • “cellular surgery”

• packages molecules into vesicles which later merge with the cell membrane during exocytosis

what is the peroxisome

• organelle filled with hydrogen peroxide (H2O2) in order to break down material

• similar to lysosomes but it doesn’t use enzymes

• a natural antibiotic/antiviral/anti-toxin

  • H2O2 is often used as a disinfectant, antiseptic, or bleaching agent

what is the endomembrane transport

• well-oiled, fluid process of the cell:

  • mitochondria and nucleus work together to give the cell energy and instructions necessary for producing life →

  • MRNA produced from transcription in the nucleus is send to the RER →

  • RER translates MRNA into proteins and sends them through SER →

  • SER transports proteins to the golgi →

  • Golgi modifies and packages proteins into membrane-bound vesicles →

  • sacked vesicles fuse into cell membrane and proteins go through exocytosis

• Exocytosis

  • the process by which something inside the cell will leave the cell

• Endocytosis

  • the process by which something outside the cell will come into the cell

what is the difference between microfilaments, microtubules, and intermediate filaments

• microfilaments

  • made of actin whose primary job is to interact with myosin to induce muscle contraction

  • help with cell movement, contraction, and shape changes

  • make the cleavage furrow during cytokinesis

    • the separation of daughter cells during mitosis/meiosis

• microtubules

  • made of tubulin

  • involved in the synthesis of cilia and flagella

    • ex: respiratory tract and sperm cells

  • make up the centrioles and help them move to opposite sides of the cell during cell division

    • separation creates the mitotic spindle

• intermediate filaments

  • rope-like protein fibers that absorb tension and help anchor organelles

what are tissues

• organized sheets of cells

• listed in order of increasing regenerative ability:

  1. epithelial

  2. muscle

  3. connective

  4. nervous (neuron)

what are epithelial tissues

• covers the body and lines its cavities

  • cavities= holes (inner ear, nose, etc.)

• involved in absorption, secretion, transportation, and sensation

  • most organs are lined with epithelial tissue

• make up the parenchyma

  • the functional parts of any organ/gland

what are connective tissues

• create the framework for other things to rest and function on

• most cells here produce and secrete materials like collagen (strength) and elastin (flexibility) which help make up the extracellular matrix (ECM)

  • complex 3D network of proteins that provides structural support for cells and tissues

• ECM lies within connective tissues and gives it the strength and flexibility it needs to do its job

  • lots of ECM = proper connective tissue

• examples: bone/cartilage/tendons, small intestines, blood

  • even though it transports, blood is made of fluid connective tissue and not epithelial because it’s made of an ECM → plasma

    • blood vessels (arteries/veins), however, are lined with epithelial tissue

bacteria classifications

1. cocci

   • sphere shaped

     • s. aureus

   • gram neg or pos

2. bacilli

   • rod shaped

     • myobacterium tuberculosis

   • mostly gram pos

3. spirilli

   • spiral shaped

     • treponema palidum (syphillus)

   • only gram neg

what are the kinds of cell walls in prokaryotic cells

1. thick peptidoglycan layered

   • gram positive bacteria

   • stain purple or blue

     • staphylococcus pneumonae

2. thin peptidoglycan layered

   • gram negative bacteria

     • contains lipopolysaccharide (LPS) which causes much harsher infections in the body due to being immunogenic (activates and flares up the immune system)

   • stains red or pink

     • salmonella

key facts about prokaryotic cells

• have a cell wall NOT a membrane

• often have flagella that operate as motors for transportation

  • filament at the tip of the flagella rotates from the base and generates torque

• have a nucleoid region for compartmentalization

  • NOT a nucleus

• can transfer and acquire DNA through plasmids

  • small rings of DNA (separate from actual DNA) that hold information in nucleoid region

  • episomes are autonomous plasmids capable of inserting themselves directly into main bacterial DNA

• reproduce asexually

what are the ways prokaryotes can reproduce

1. Binary Fission

   • splitting into clones of themselves (SpongeBob)

2. Horizontal Gene Transfer

   • the process of bacteria acquiring new genetic material

   • Genetic Recombination is essential for HGT

     • cells break down, exchange, and rejoin DNA segments to increase genetic variation and repair damage

     • crucial for adaptation and evolution

   • Types of HGT:

     1. Transformation

        • bacteria picks up elements of another bacteria when it dies and releases its insides

     2. Transduction

        • when a virus (bacteriophage) accidentally transfers the genetic material from one bacteria to another

     3. Conjugation

        • bacteria passes on genetic material via a mating bridge which enables the acquirement of new traits like antibiotic resistance

        • bacteria with fertility factor plasmids (F+ bacteria) can form the conjugation bridge while those without (F-) cannot

          • this conjugation bridge is a “sex pilus” that allows the transfer of copied plasmids to other bacteria so an F- bacteria can become F+ and continue the cycle!

          • F+ cannot mate with F+ because it would be ineffective

            • EVERYTHING has a purpose!!

explain the life cycle of bacteria

• bacteria have lag, exponential, plateau, and death phases

  • they are born into an environment with limited resources (lag)

  • they must build up their resources (exponential), then eat through them (plateau) until there isn’t any more to consume (death)

• the rate of growth = the rate of death in this cycle

  • example of biological equilibrium

  • reason for plateau phase

what are the parts of viruses and sub-viral particles

• Protein Capsid

  • protective outer coat made of proteins

  • encloses and transports viral nucleic acid (DNA/RNA)

  • can be helical or polyhedral shaped

• Genome

  • either DNA or RNA

    • if virus has DNA, host cell does all the work and replicates, transcribes, and translates viral genome through cell cycle

    • if virus has RNA, it must bring its own enzymes:

      • RNA-dependent RNA polymerase used to help a virus make its own RNA copies for host ribosomes to make into proteins

      • Reverse transcriptase used by retroviruses to turn their RNA into DNA host can work with

  • lytic or lysogenic reproduction

• Spike Proteins

  • glycoproteins that facilitate host entry and infection through penetration

  • determine tropism: method by which a virus recognizes a host cell to infect with the specificity of a key to a lock

  • help virus evade host immune system

• SOME have a lipid envelope

  • a phospholipid bilayered membrane stolen from host cells

  • able to enter host cells through fusion

what are viruses and what are the “special” viruses

• intracellular parasites that obligate (force) a living host cell for reproduction

1. Bacteriophages

   • viruses that only target bacteria

   • can perform transduction

2. Retroviruses

   • use reverse transcriptase to change and integrate themselves into a host cell’s genome

   • famous retrovirus is HIV

3. Viroids

   • tiny viruses that infect plants

   • lack a protein coat

what is a superinfection

• a second, overlapping infection that’s often caused by

  • microorganisms resistant to treatment given to combat the first infection

  • antibiotic treatment killing off protective microflora, allowing new pathogens to strengthen

• example:

  • s. aureus is commonly caused by a post influenza infection and extremely dangerous due to immune impairment and lung damage that allows pneumonia to develop quickly

what is endocrinology

• study of the endocrine system

  • a series of glands, hormones, effectors, and pathways that mainly regulate long-distance and long-term communication within the body

  • essentially acts as a carrier pigeon: gland → circulatory system (bloodstream) → target

  • the goal is homeostasis: resisting changes to maintain a stable environment

1. glands

   • secretory tissues or organs within the body that respond to various stimuli

     • adrenal glands, pituitary glands, etc.

2. hormones

   • a molecule or protein that has the capacity to bind receptors and influence responses on the cellular/tissue/organ level

   • the thing that is released from glands into the bloodstream

     • dopamine, cortisol, insulin, etc.

3. effectors

   • structures that act in response to stimuli

     • liver responds to insulin and increases glucose uptake

4. pathways

   • complex, interconnected, signalling networks in which glands release hormones into the bloodstream to function

     • HPT axis, HPG, HPA, etc.

why does the endocrine system exist

• we are not single-celled and need a way to communicate between the furthest of cells

• the system allows us to:

  • hijack communication pathways

  • relay signals to specific places and get them there in time

  • have the signaled message stay long enough to maintain a response/effect

• the body is very needy!

  • it wants what it wants, when it wants, and in the amounts it wants it in

what is the tropic effect

• when a hormone is unable to perform a job on its own and employs a secondary messenger to regulate the response

• example:

  • the growth hormone (GH) exhibits its effects through linear growth (height) and is released from the anterior pituitary gland (APG). In order to release it, the APG is stimulated by the growth hormone releasing hormone (GHRH)

    • A → B → response

    • A is tropic, B is direct

what is the hypothalamus

• the control center (HQ) of the endocrine system

• the pituitary gland serves the hypothalamus as a henchman

  • split into two main sections: anterior and posterior

• posterior:

  • the hypothalamus produces oxytocin and ADH and sends them via long nerve fibers

• anterior:

  • the hypothalamus produces releasing and inhibiting hormones as signals

  • anterior hormones are its own!

describe the anterior pituitary gland

• front lobe of the pituitary gland that is identified as endocrine acting

  • this is because it secretes hormones directly into the bloodstream

• connects to the hypothalamus through a network of blood vessels

  • hypophyseal portal system

    • made up by the hypophyseal portal vein

    • supplies releasing and inhibiting signals from the hypothalamus and blood to the APG

• nicknamed the “master gland”

  • produces 7 key hormones (GH, FSH, LH, etc.)

describe the posterior pituitary gland

• back lobe of the pituitary gland that is identified as neuroendocrine acting

  • a.k.a neurosecretory~ essentially “one giant neuron”

• routinely shocked by the hypothalamus with nerve endings that cross over and drop electric signals

  • shocks cause hormone secretion

• only releases 2 hormones

  • oxytocin and ADH

what are the types of blood vessels and their functions

1. Veins

   • carry oxygen-poor blood toward the heart

2. Arteries

   • carry oxygen-rich blood away from the heart

3. Capillaries

   • connect veins and arteries

   • facilitate nutrient and waste exchanges

what is a portal vein

• a vein that circulates between two organ systems or tissue beds

• helps identify toxins before they enter the bloodstream

  • carries to the liver for detoxing

• contains little hormone molecules

what are the different categories for identifying hormones

1. By Effect

   • Direct

     • does the deed

       • ex: T4 accelerates cellular metabolism

   • Tropic

     • gets a guy (usually an organ) to do the deed

       • ex: TSH smacks the thyroid to make T4 accelerates cellular metabolism

   • Double-Tropic

     • gets a guy to get a guy to do the deed

       • ex: GnRH stimulates the APG into producing FSH and LH which act on endocrine gonads to produce estrogen, progesterone, and testosterone (1° sex hormones)

2. By Structure

   • Steroid Hormones

     • a derivative of cholesterol via reaction

       • ex: -one, -ol, -oid family (cortisol, progesterone)

     • mainly non polar hormones

       • allows them entrance into cell through membrane so they bind to an intracellular steroid receptor, forming a complex that travels into the nucleus and changes transcription (DNA → RNA) of DNA

         • complex is a transcription factor

   • Amino Acid Hormones

     • very polar and unable to enter through the cell membrane

       • must bind a receptor from outside, leading to a signal transduction cascade which leads to a hormonal effect

         • cascade modifies transcription in a similar way to steroid hormones

       • ex: T3, T4

   • Peptide Hormones

     • polypeptides (amino acid chains)

       • protein-derived

       • MUST be polar and MUST bind to a receptor

       • ex: insulin, ghrelin

describe the mitosis cell cycle

• a series of phases that eukaryotic cells undergo in order to reproduce

  • DNA is replicated and split, and the cell divides into 2 identical daughter cells

• mitosis only happens to somatic, diploid cells

  • somatic ~ also called autosomal; body cells with uninheritable mutations

  • diploid~ have 2 of the necessary genetic material to code for the genome (2n; n=23)

• split into 4 phases:

  1. Mitosis

     • cell is actively dividing

     • everything else is interphase (preparation for mitosis; G₁, S, G₂)

       • individual chromosomes are not visible during interphase due to DNA being in a less condensed state (loose/unwound) to get ready for replication

  2. G₁ (pre-synthetic gap)

     • growth/bulking stage where the cell size increases in preparation for replication

     • includes a checkpoint before S phase

       • ensures cell has proper amounts of, type of, and accommodations for the DNA

  3. S (synthesis)

     • cell replicates genetic material so that each daughter has identical DNA

     • after replication, each chromosome consists of 2 sister chromatids bound by a centromere

       • still 1 chromosome

     • checkpoint occurs before G₂ phase to make sure replication is correct

  4. G₂ (post-synthetic gap)

     • another bulking stage with more cell growth, copying of organelles, and protein synthesis

     • this is the time for any damaged DNA to be repaired before mitosis

       • another checkpoint

  5. G₀

     • where cells that are not dividing go to carry out functions (chill)

what are the stages of mitosis

1. Prophase

   • nuclear envelope dissolves to break the barrier between nucleus and cytoplasm

   • genetic material condenses again and chromosomes become visible

   • centrioles form and start to move away

2. Metaphase

   • chromosomes line up at the center of the cell (metaphase plate)

   • centrioles are now at opposite poles of the cell

3. Anaphase

   • centrioles begin throwing spindle fibers made of microtubules at the chromosomes, causing sister chromatids to separate from each other

4. Telophase

   • spindle apparatus disappears

   • nuclear membrane reforms

   • chromosomes uncoil

   • cleavage furrow begins to form

• Cytokinesis

  • usually begins as mitosis is ending (may have a little overlap)

  • cleavage of the cytoplasm into 2 daughter cells

what is the evolution of chromosomes during mitosis

• chromosomes are counted by centromeres so you can have 1 chromosome with 2 chromatids

  • chromatid~ 2n, single stranded

  • sister chromatids~ 2n, double stranded

1 cell with 1 chromosome, 1 chromatid → copying of DNA in synthesis of interphase →

1 cell with 1 chromosome, 2 sister chromatids → chromosome separation in anaphase of mitosis →

2 cells with 1 chromosome, 1 chromatid each after cytokinesis

describe the meiosis cell cycle

• a series of phases that non-somatic, eukaryotic cells undergo to reproduce

• occurs only in and produces haploid cells

  • gamete cells (1n; n=23)

    • sperm or egg (sex) cells

  • single stranded

  • enough to code for another genome (23 from mother (XX), 23 from father (XY))

    • 2 haploids = 1 diploid which sustains its life through mitosis

    • involves crossing over

• follows the same general formula as mitosis

what are the stages of meiosis

1. Meiosis I

   • starts with prophase I which is the same as mitosis prophase but it involves crossing over/ recombination

     • the exchange of genetic material between non-sister chromatids of homologous chromosomes by way of touching and fusing with each other

     • outside of spontaneous mutations, this process is responsible for all the genetic variation in humans

   • metaphase I is the same as mitosis metaphase

   • anaphase I is the same as mitosis anaphase but the homologous chromosomes are pulled apart

   • telophase I is the same as mitosis telophase but the end product is 2 haploid cells with their chromosomes still condensed

2. Meiosis II

   • happens right after meiosis I

   • the exact same as the mitosis cycle but with 1 single chromosome

what is the evolution of chromosomes during meiosis

• chromosomes are counted by centromeres so you can have 1 chromosome with 2 chromatids

  • chromatid~ 2n, single stranded

  • sister chromatids~ 2n, double stranded

46 double stranded chromosomes, 92 chromatid → pulling apart of homologous chromosomes

23 double stranded chromosomes, 46 chromatid after telophase I → meiosis II

23 single stranded chromosomes having 1 chromatid each as end products

what are non-disjunction errors

• problems that arise from incorrect meiosis and lead to of several diseases

  • create specific changes in sex chromosomes (23rd pair)

• typically only affect females

  • women have all the ova they will ever create at birth (frozen in time since fetuses)

• happen primarily during meiosis I when homologous chromosomes fail to separate correctly

  • leaves a haploid cell with an abnormal # of chromosomes after meiosis is completed

    • 1 extra~ trisomy

    • missing~ monosomy

what happens in cases of trisomy or monosomy of the 23rd chromosome

• Trisomy

  • when a sperm cell fertilizes an egg with a 3 pairs of the 23rd chromosome, it usually forms a zygote that cannot develop normally

    • ex: Klinefelter syndrome (XXY) is characterized by tall stature, more breast tissue resulting in a larger chest, sparse hair, small penises and testes resulting in low testosterone and low fertility

• Monosomy

  • when a sperm cell fertilizes an egg with an emply 23rd chromosome, only 22 pairs will form and the zygote will be XO

    • ex: Turner syndrome is characterized by short stature, low-functioning ovaries, broad chests, puffy hands and feet at birth, webbed necks, and infertility due to rapid loss of eggs within the ovaries

describe the male reproductive system

SEVEN UP ACRONYM:

• S

  • Seminiferous Tubules

    • specific location of meiosis where spermatozoa (sperm) are created in the testes

• E

  • Epididymus

    • where sperm are stored until matured, or gain motility

    • palpable through the skin

• V

  • Vas Deferens

    • transports sperm from epididymus to ejaculatory ducts before ejaculation occurs

• E

  • Ejaculatory Duct

    • transports sperm through prostate gland into the urethra during ejaculation

    • sperm becomes semen as it mixes with seminal fluid from the seminal vesicles, prostate gland, and cowper’s gland during ejaculation

• N

  • N/A

• U

  • Urethra

    • formed from merged ejaculatory ducts

    • transports urine and semen to outside of the body

• P

  • Penis

    • external sex organ that connects to the urethra

    • enables urination and reproduction

what is seminal fluid

• fluid that mixes with sperm to nourish it and help transport it out of the body during ejaculation

• produced by the seminal vesicles, prostate gland, and cowper’s gland

  • this also produces pre-seminal fluid (precum) to clear out the urethral pathway of urine which is a hostile (acidic) environment for incoming sperm

• semen is

  • the mix of seminal fluid and sperm

explain the onset of puberty in men

• the sex-determining region in the Y chromosome (SRY) activates in development and stimulates testes formation as well as the formation of other sex organs

  • acts as a “master switch” during gestation: pregnancy stage

• at the onset of puberty, the hypothalamus releases GnRH to stimulate the APG into releasing FSH and LH

  • FSH enters the testes and helps facilitate spermatogenesis

    • the production of semen from the primordial germ cells (diploid → haploid)

    • FSH provides the structural and nutritional needs for sperm development

  • LH enters the testes to make and release testosterone into the testes and blood

    • hormone responsible for 2° sex characteristics (body hair, voice, etc.)

    • testosterone helps mature sperm and has positive feedback on cells that facilitate spermatogenesis

describe the female reproductive system

• Ovaries

  • main reproductive organ that contains thousands of follicles

  • derived of the same tissue as testes but respond differently to hormones due to differences in development

    • SRY prevents development of female parts during pregnancy

• Follicles

  • sacs that nourish and protect ova

• Ova

  • plural of ovum

    • a single egg cell (largest in human body)

One ovum is expelled per month in response to hormonal activity. It is put into the abdominal cavity and sucked by the fimbrae of the fallopian tube

• highest point in the fallopian tube is the most common site of fertilization

explain the onset of puberty in women

• before puberty, the hypothalamus restricts the synthesis of GnRH

  • when it finally triggers, GnRH stimulates APG into releasing FSH and LH

• FSH

  • stimulates ovaries to secrete estrogen

    • forms 2° sex characteristics (body hair, breast development, etc.)

    • thickens the endometrium

      • uterine lining designed perfectly to sustain life

• LH

  • stimulates corpus luteum to secrete progesterone

    • protects and maintains the endometrium in preparation for fertilization

      • when fertilization doesn’t occur, the super thick endometrium layer (continual estrogen exposure) sheds

        • this shedding is menses: bleeding

explain the menstrual cycle

1. Follicular Phase (Days 1-13)

   • begins with menstrual shedding (flow) in response to the sudden loss of hormones from luteal phase (cycle)

     • causes stimulation of hypothalamus to release GnRH → APG → FSH & LH

   • release of FSH leads to the stimulation of follicles

     1. matures 1 egg cell in preparation for the next cycle

     2. secretes estrogen which in turn has a negative feedback effect on GnRH release from the hypothalamus

        • secreted estrogen stimulates the growth of endometrial lining, glands, and decidua

          • thick layer of mucus that lines the endometrium; reason for discharge

   • late into this phase, estrogen levels hit their peak and turn off their negative feedback effect on GnRH

     • results in a huge influx of FSH and LH release

2. Ovulation (Day 14)

   • caused by the spike in LH caused by the turning off of estrogen’s negative feedback

   • characterized by mittelshmertz

     • sharp pain in the right abdomen

     • leads to the release of mature ovum

       • ovum breaks out of the follicle it resides in, turning it into the corpus luteum: ruptured follicle

   • the corpus luteum stays behind in the ovary responding to the LH

3. Luteal Phase (Day 15-28)

   • preparation of the uterus for fertilization

   • LH stimulates the corpus luteum to secrete progesterone which:

     • leads to further development of endometrium layer

     • has a negative feedback on GnRH production

   
   

   • NO FERTILIZATION:

     • corpus luteum eventually desensitizes to LH, breaking off the chain of command

       1. sudden loss of progesterone leads to endometrium shedding → menses

       2. negative feedback turns off, restarting the cycle by releasing GnRH again → follicular phase

          • endometrium is rebuilding as it sheds! fast-healing wound to prevent infections

   
   

   • FERTILIZATION:

     • formation of a zygote which burrows into the endometrium leading to the production of β-hCG (beta human chorionic gonadotropin)

       • looks exactly like LH but the corpus luteum cant get tired of it due to shear amounts of progesterone it demands

         • happens until the placenta is matured and makes the progesterone itself until the end of pregnancy

       • β-hCG can be detected 2 weeks after implantation of the zygote

         • determination of pregnancy tests

explain the cause for the negative feedback effect estrogen has on GnRH if it leads to FSH which leads to more estrogen

• the negative effect is proportional to ovum maturity in the body

  • prevents the expulsion of more than 1 ova at the same time

• this effect is a homeostatic, fine-tuned dial

  • balance

• happens until only one egg cell is left responding to GnRH

  • perfect for fertilization or the expulsion of the egg in the next cycle

• prevents an early surge of LH which would release the egg before fully maturing

explain menopause

• ovaries become less sensitive to FSH and LH with age and eventually atrophy (shrink and lose function), leading to:

  • less production of estrogen and progesterone

  • end of menstruation

  • abundant levels of FSH and LH in the blood

    • continually trying to stimulate follicles that are no longer responding → menopause

• characterized by:

  • vaginal dryness

  • hot flashes

  • sleep problems

  • mood changes

  • risk of cardiovascular disease

what is p53

• gene modulates DNA sequences so they don’t go haywire and cause cancer

• natural tumor suppressor

  • people who do not properly inherit this gene are predisposed to cancer and usually experience several tumors of various tissues in early adulthood

describe the heart’s role in the cardiovascular system

• main player that acts as a glorified pump (among other things)

• takes in blood and shoots it back out

• main goals:

  1. transfer oxygenated blood throughout the body

  2. maintain adequate perfusion pressure

     • amount of pressure necessary to maintain blood flow to the body

     • perfusion~ process by which blood enters the place it needs to go

• the pump (heart) accomplishes these goals through pipes (vessels)

  1. Arteries~ away; most carry oxygenated blood

  2. Veins~ toward; most carry de-oxygenated blood

     • ex: pulmonary artery travels away from the heart and towards the lungs but carries de-oxygenated blood to be later oxygenated in the lungs

what are the general compartments of the heart

1. Right Atrium

   • connects to the vena cava

     • largest vein in the body

     • divides into 2 parts: superior and inferior (SVC & IVC)

       • SVC carries blood from upper body (head, neck, arms, chest)

       • IVC carries blood from lower body (abdomen, pelvis, legs)

     • carries all blood returning to the heart and lungs for re-oxygenation (venous blood)

       • this blood drains into the right atrium which then empties into the right ventricle through a valve

2. Right Ventricle

   • connects to the pulmonary artery

     • this artery carries the venous blood that’s just drained into the right ventricle to the lungs to be re-oxygenated

     • it parts into left and right pulmonary arteries to send the blood to each lung

3. Left Atrium

   • connects to the pulmonary veins (4 of them)

     • these carry oxygenated blood from the lungs into the other side of the heart

     • veins plug into the left atrium, allowing blood to be drained into the left ventricle through a valve

4. Left Ventricle

   • connects to the aorta

     • largest artery in the body

     • handles all the oxygenated blood volume that comes out of the heart through the left ventricle and transmits it to the part of the body it needs to go

• the right and left sides of the heart are separated by septa~ vertical barriers

  • interatrial septum separates the left and right atria

  • interventricular septum separates the left and right ventricles

• ventricles are more muscular/beefy than atria

  • the left ventricle is much bulkier than the right ventricle

• atria are low pressure environments, contrary to ventricles which need to generate high pressure to pump out blood through vessels

explain each valve of the heart

• valves prevent back flow of blood and open when it is time

  • act as one-way gates that are triggered by pressure changes

  • situated at ventricle and atria exits

1. Tricuspid Valve

   • a 3-leaf valve that acts as a trap door situated at the bottom of the right atrium

   • prevents back flow of blood into the right atrium as it drains into the right ventricle

   • this valve opens passively

2. Bicuspid Valve

   • a 2-leaf valve that acts as a trap door situated at the bottom of the left atrium

   • most commonly called the mitral valve

   • prevents back flow of blood into the left atrium as it drains into the left ventricle

   • this valve opens passively

3. Pulmonary Valve

   • situated at the bottom of the right ventricle

   • acts as a gate that restricts de-oxygenated blood into only flowing towards the lungs and not back flowing into the right ventricle

   • this valve swings open with pressure changes in the ventricle associated with contraction

4. Aortic Valve

   • situated at the bottom of the left ventricle

   • acts as a gate that restricts oxygenated blood into only flowing out of the heart and not back flowing into the left ventricle

   • this valve swings open with pressure changes in the ventricle associated with contraction

• the sound of the heart beat is each valve opening and closing

  • the tricuspid and bicuspid valves open and close together and are known as the atrioventricular valves because of where they are located

    • when these shut it is the first heartbeat

  • the pulmonary and aortic valves open and close together and are known as the semilunar valves because they are shaped like a half moon

    • when these shut it is the second heartbeat

explain the cardiovascular cycle

• the blood involved in this cycle DOES NOT perfuse (sustain) the heart

• this details the pulmonary cycle not the systemic cycle (blood → tissues/organs)

1. All the venous blood in the body comes back to the heart through the vena cava to be reoxygenated and empties into the right atrium

2. From the right atrium, it drains through the tricuspid valve to go into the right ventricle

3. The blood then moves through the slightly beefy right ventricle and exits through the pulmonary valve

   • valve leads to pulmonary artery which transports blood to lungs for oxygenation

4. Once blood picks up O2 at the lungs, it enters back into the heart through the pulmonary veins to be distributed to the part of the body it belongs

   • from here on out, all the blood is oxygenated to its greatest capacity unless there is a heart or blood issue

5. Blood flows into the left atrium and then drains into the very beefy left ventricle via the bicuspid or mitral valve

6. Left ventricle pumps out blood through the aortic valve which leads to the aorta

7. Oxygenated blood is distributed from the aorta to the rest of the body until it becomes de-oxygenated again

   • whole cycle restarts

explain electrical conduction in the heart

• the heart also acts as a battery

• cardiac myocites (heart muscle cells) have action potentials

  • only neurons and muscle cells are capable of this

• everything the action potential touches contracts!!

  • except SA and AV nodes

• Sinoatrial Node

  • the heart’s internal pacemaker located at the junction between atria and cardiac sinus

    • vein complex at the back of the heart (behind the right atrium)

  • made up of a bundle of cardiac myocites that fires off electrical potentials for the rest of the heart to pick up on

  • shoots off an an action potential anywhere from 60-100 BPM (beats per minute) = heart rate

  • the SA node acts solely as a messenger

• Atrial Ventricular Node

  • located at the junction between the atria and ventricles (touches all 4)

  • in charge of a roughly 0.1 second delay depending on lifestyle habits

  • this delay is of action potentials or electrical impulse from the atria to the ventricles

    • gives atria time to empty and ventricles time to fill before contraction is triggered

• Process:

  1. SA node fires action potential across both atria causing them to depolarize which leads to them “contracting” in what’s called an atrial kick

  2. Signal reaches the AV node which slows down the electrical impulse, causing a delay

  3. Action potential then swiftly travels down the interventricular septum after the delay using the Bundle of His (BOH) and wraps around the ventricle walls using the Purkinje fibers

     • ventricle walls contract

     • BOH and Purkinje fibers together make up the His-Purkinje system

• action potential travels fast across atria, then slow at the AV nodes, then super fast down the septum and around the ventricles

explain how the cardiovascular cycle and electrical conduction of the heart happen simultaneously

1. Tricuspid and bicuspid valves open passively as the heart relaxes after contracting (pulmonary and aortic valves shut)

   • as this happens, blood is entering the heart following the last pump of the ventricles and drains from the atria into the ventricles due to the agape atrioventricular valves

2. As the blood is filling up the ventricles after entering the atria, the SA node fires off action potential leading to the atrial kick

   • depolarized atria “contracts”/shocks and kicks any remaining blood down the trap doors of the atrioventricular valves

3. Action potential signal hits the AV nodes leading to the delay

   • delay gives enough time for the atrial kick to get every last drop of blood to the right and left ventricles

4. Signal then travels down the left and right BOH and is distributed through the Purkinje fibers to the ventricles

   • this causes ventricles to depolarized and contract, forcing open the semilunar valves and pushing blood out of the heart through them

   • as the semilunar valves open, the atrioventricular valves shut making first heart beat

5. Left and right ventricles repolarize, causing the heart to relax and the semilunar valves to close

   • shutting of semilunar valves produces the second heart beat

   • heart relaxation and shutting of semilunar valves opens the atrioventricular valves passively

     • cycle restarts

what does it mean that veins and arteries are umbrella terms

• Veins

  • compliant; “pushed around”

  • carry de-oxygenated blood back to the heart in systemic circulation and oxygenated blood back to the heart in pulmonary circulation

  • systemic veins are much further from the heart than the arteriole system = they have much lower pressure than arteries

  • types:

    • venules~ smallest levels of veins which receive de-oxygenated blood from capillaries

      • lead back to larger veins → vena cava

    • larger veins~ have their own valves to prevent backflow

      • ex: keeps blood going to the heart instead of gravity → legs

• Arteries

  • elastic and muscular

  • resist change by “pushing back” which generates pressure

    • arteriole system has the highest pressure in the body

  • types:

    1. large arteries~ closest to the heart; have high elastic tissue to withstand high heart pressure

    2. medium arteries~ very muscular; distribute blood to specific body organs/tissues

    3. arterioles (small)~ main source of systemic vascular resistance (SVR) which is majority of the resistance in the body

    4. capillaries (very small)~ final step of arteriole system; lead directly to venules

       • only 1 cell layer thick- red blood cells travel in a single file

         • best scenario for RBC picking up O2 and transferring it

explain systemic vascular resistance (SVR)

• SVR is the resistance that must be overcome for blood flow to circulate throughout the body

• sourced in the arterioles → medium arteries → large arteries → aorta

  • pressure translates up the arteriole system and to the aortic valve, keeping it pushed closed until the LV contracts enough to force it open (SA/AV nodes)

    • when action potential shoots down to the ventricles and depolarizes them, they contract until the pressure inside the ventricle is greater than the pressure of the SVR keeping the aortic valve closed

      • this is how blood pressure is generated in the body

• when SVR is overcome by LV, the valve shoots open and blood pumps out the aorta to the rest of the body, leaving pulmonary circulation and entering systemic circulation

what is blood pressure

• the amount of force your blood uses to get through your arteries

• needs to 2 things to generate BP:

  1. adequate blood volume outside the heart to pump against

  2. adequate blood volume inside the LV for the heart to pump against

• measured by systolic pressure / diastolic pressure~

  • normal range is 100/65 < x < 120/80

  • systolic pressure

    • peak pressure of LV contraction against aortic valve to force it open

  • diastolic pressure

    • pressure in the arteriole system when heart rests in between beats

    • lowest pressure in the aorta as the ventricle is refilling after contraction

• equation: MAP = HR · SV · SVR

  • MAP is reflective of average blood pressure (1/3 SP + 2/3 DP)

  • HR is heart rate

  • SV is stroke volume or blood volume

    • HR · SV = CO or cardiac output~ the amount of blood that exists in the heart at any given time

  • SVR is systemic vascular resistance

describe the arteriole system (systemic circulation)

1. Oxygen-rich blood leaves the LV and goes through the aorta

2. Aorta → large arteries → medium arteries → arterioles

3. Arterioles lead blood to the capillary beds where waste exchange happens

   • capillaries exchange O2 for CO2 with the cells

   • O2 and nutrients pass through capillary walls into tissues whole CO2 and waste enters blood

   • anything to large to pass through capillary walls (like proteins) is not being exchanged

4. After waste exchange, de-oxygenated blood moves to the venules from the capillaries

5. Venules → larger veins → vena cava → RA → RV → lungs

** after de-oxygenated blood leaves the capillaries and enters the venous system, it can take a secondary pathway to the vena cava via portal veins where it drops by another organ/tissue bed first

• this is the Hepatic Portal System

• these portal system veins ensure blood containing toxins and nutrients is filtered, detoxed, and metabolized (nutrients) by the liver before reaching the heart

  • portal veins are not considered “true veins” because they do not lead to the heart but the liver

describe blood composition

• blood is 55% fluid (plasma) and 45% cells:

  • erythrocytes

    • red blood cells

    • job is to carry and drop off O2; return with CO2 and drop that off

    • biconcave (side profile teaaa) which increases surface area

      • this allows them to hold more hemoglobin and improve gas exchange

    • each RBC has 250 million molecules of Hb that each hold 4 O2 molecules

      • a single RBC carries 1 billion O2 molecules

    • they lose organelles during maturation which means NO MITOCHONDRIA

      • mitochondria require O2 for energy which limits efficiency

    • unable to divide~ life span is 90-120 days

      • travel to the spleen to die after circulation

  • leukocytes

    • white blood cells

  • platelets

    • cell fragments

    • aid in coagulation

      • blood clotting, or thickening, that prevents excessive bleeding after an injury

describe how blood types work

• blood types are determined by alleles (genetics)

  • ABO Gene (3 alleles)

    • A (I_A) - equally dominant with B

    • B (I_B) - equally dominant with A

    • O (i) - recessive (need 2)

  • RH Factor (2 alleles) ~ protein found on the surface of RBC

    • Rh⁺ - dominant

      • can receive Rh⁺ or Rh^- blood

    • Rh^- - recessive (need 2)

      • Rh^- can only receive likewise blood

      • Hemolytic Disease of a baby is caused by an Rh^- mother developing anti-D antibodies against her Rh⁺ fetus during pregnancy

• a person’s immune system attacks whatever blood it doesn’t have (except O^-)

• AB⁺ is the universal recipient and O^- is the universal donor

what are the all the blood type options

1. I_AI_A ~ type A

2. I_BI_B ~ type B

3. I_AI_B ~ type AB (both show because equally dominant)

4. I_Ai ~ type A with a carrier for O

5. I_Bi ~ type B with a carrier for O

6. ii ~ type O

• each with ± for Rh

what is the interstitium

• spaces that exist outside of capillaries and act as storage sites for interstitial fluid

  • hold tons of fluid that is made of plasma (55% of blood)

  • help move nutrients/waste and anchor structures

  • exert pressure on capillary walls and vice versa

describe hydrostatic and oncotic pressures of the capillaries and interstitium

• P_c

  • hydrostatic pressure of the capillary

  • the force plasma exerts on capillary walls as it travels through

• π_c

  • oncotic pressure of the capillary

  • “sucking” pressure of the capillary from the interstitium

• P_i

  • hydrostatic pressure of the interstitium

  • the force interstitial fluid exerts on capillary walls

• π_i

  • oncotic pressure of the interstitium

  • “sucking” pressure of the interstitium from the capillary

• P_c and π_c both originate from the capillary while P_i and π_i originate from interstitium

• equilibrium is when P_c = P_i and π_{c =} π_i

  • fluid balance

  • this does NOT mean there is no fluid entering or exiting the capillary but that it is happening at the same rate

equation: π = iMRT

• π = oncotic pressure

  • more salt in the bloodstream = more oncotic pressure because the salt absorbs or “sucks” water from around it

• i = van’t hoff factor

• M = molarity of the substance present

• RT = constant