MCAT-Biology & physiology

Respiratory System

Respiratory tract:
Mnemonic: No, Cap. Please Ehh... Lick Those Big Beautiful Asses

Nose/oral cavity, Pharynx (3), epiglottis, Larynx, Trachea, Bronchi, bronchioles, Alveoli sac - gas exchange.

Conduction Zone: (Mouth to terminal bronchioles)
-No gas exchange as walls is too thick. Epithelial Cilia and mucus protect against pathogens.

Respiratory zone: (Respiratory Bronchioles to Alveolar Sacs)

-No cilia and mucus as it interferes with gas exchange with bloodstream. Use Alveolar macrophages instead.

Henry's law:

To find concentration of O2 dissolved in liquid-

[O2]=(PartialP)O2+(Solubility)O2

Lung volume and Capacity:

TLC=RV+VC

VC=ERV+IRV+TV

circulatory system/blood pressure/conduction/output

Circulation
Deoxygenate blood into Superior Vena Cava (SVC)->Right atrium--Tricuspid AV-->Right Ventricle--Pulmonary SV-->Pulmonary artery-->lungs.

Oxygenated blood into Pulmonary vein->Left atrium--Bicuspid AV-->Left ventricle--Aortic SV-->Aorta-->Body.

Pulmonary: Right ventricle->lungs->left atrium

Systematic: Left ventricle->body->right atrium

Pressure

Left ventricle is stronger than right ventricle, because systemic circulation push blood to rest of body.

Systolic Blood Pressure: Ventricles are contracted while atrioventricular valves (AV) are closed. Blood pumped out of ventricles. This pressure is greater than diastolic because heart contracts.

Diastolic Blood Pressure: Ventricles are at rest and semilunar valves (SV) are closed. Blood flow into ventricles

Conduction: Nodes: (Mnemonic: Suck A Big Penis)

SA (Sinoatrial) node, AV (atrioventricular) node, Bundle of His, Purkinje fibers.

Cardiac Output (Blood volume/min): Heartrate (beat/min) x stroke volume (Blood volume/beat)

Neurotransmitters

Acetylcholine-excitatory, open Na+ channels, motor and cognition.

Norepinephrine-excitatory, fight/flight and reduce digestion.

Dopamine-excitatory, satisfaction/motivation.

Serotonin-inhibitory, sleep and arousal

Endorphins-inhibitory, pain reliever

GABA-inhibitory, opens Cl- channels, calms brain.

Glycine-inhibitory

Glutamate-excitatory, close K+ channels, memory and learning

Mnemonic:ANDSEGGG

AND-both CNS/PNS

SEGGG-CNS only

Membrane transport

1.      Passive Transport

a.      Simple Diffusion- Direct movement through the lipid bilayer without proteins.

b.      Facilitated Diffusion

• Channels: Voltage-gated (Ions), Ligand-gated (Ions; small molecules, Mechanosensitive (Ions; small molecules)

•  Carriers: Uniporters (only) (small molecules) Changes confirmation when ligand-bound.

2.      Active Transport

a.      Energy source

• Primary Active Transport - Uses direct energy input (e.g., ATP) to move molecules against their concentration gradient.

• Secondary Active Transport (Cotransport)-Dependent on the energy stored in an electrochemical gradient from primary active transport to move molecules against gradient.

b.      Movement

• Symporters (Active): Two different molecules in the same direction.

• Antiporters (Active): Two different molecules in opposite directions. Ex: Sodium/Potassium Pump (Moves 3 NA+ out and 2K+ into the cell.

c.      Proteins

• Pumps always do primary active transport, in which carriers can depend on.

• Carriers can fill out all classifications.
  

endomembrane system (environment, path, PTM, lysing)

Components: Mnemonic: PLEG

Plasma membrane, lysosome, ER, ang Golgi are phospholipid bilayers.

Environment:

Cytoplasm is reducing environment of ph 7.2; has high ratio of GSH to scavenge ROS. Endomembrane is oxidizing environment of ph 3.5-7.2; required for protein molding and modifications.

Secretory pathway: ER->Golgi->plasma membrane->ECS

• Golgi: Vesicles are tagged by peptides to be directed to ECS or become lysosomes.

PTM: mnemonic: GHASPLUM

Glycosylation, hydroxylation (ox) , Acetylation, Sulfonation, Phosphorylation, Lipidation, Ubiquitination (ox), Methylation (reducing Rxn)

Lysosomes: mnemonic: GL(N)UPP- all the hydrolases

Glycosylase, lipase, phosphatases, nuclease, protease (peptidase)

Signal transduction cascade

G-coupled protein receptor (GCPR) is a transmembrane receptor bound to G-protein with alpha, beta, gamma subunits.

Upon dephosphorylation of GDP on the alpha-subunit, the activated alpha unit dissociates and stimulates Adenyl Cyclase (AC), converting ATP to cAMP. This cAMP then displaces the PKI inhibitor from PKA, enabling PKA to phosphorylate proteins and transcription factors. In this cascade, the extracellular signal acts as the primary messenger, AC serves as the effector, and cAMP acts as the secondary messenger.

Another instance occurs when the alpha-unit binds phospholipase C (PLC), leading to the hydrolysis of PiP2 into DAG and IP3. DAG activates Protein Kinase C (PKC), while IP3 opens Ca2+ channels, releasing calcium from the endoplasmic reticulum (ER) into the cytoplasm, thereby activating calmodulin.

Here, PLC acts as the effector, and IP3 functions as the secondary messenger.

apoptosis and autophagy

Apoptosis: Programmed cell death, followed by macrophages and neutrophils cleaning up (efferocytosis) amino-acids, carbohydrates and lipids.

Regulation of Apoptosis

-BAX/BAKs proteins: binds mitochondria making it for permeable to release cytochrome into cytoplasm. Cytochrome C then complex with proteins forming apoptosome.
Apoptosomes activates caspase enzymes responsible for apoptosis.

Regulation of BAXs/BAKs:

Pro apoptosis -

• Extrinsic

  • Activated plasma-membrane (PM) death receptors.

  • Cytotoxic T-lymphocytes (CTL) release perforin, which form pores in PM for entry of Granzyme Bs.

• Intrinsic

  • DNA damage and oxidative stress.

Anti apoptosis - BCL2 proteins block caspase activation

Autophagy: Involve lysosomal hydrolases such as glycosidases, lipases, nucleases, proteases to recycle components for energy production or building materials (typical list minus phosphatase)

• Macroautophagy - Phagophore expands into autophagosomes and fuse with lysosome to form autolysosome for bulk recycling.

• Microautophagy - (Direct lysosomal engulfment) Basic lysosomal action in which cellular component is degraded with hydrolases.

• Chaperones-mediated autophagy (CMA) - Chaperones/HSPs deliver KFERQ motif (mnemonic KEFIR) containing proteins to lysosomes.

Transcription (gene expression)

Transcription Regulation and Gene Expression
Transcription factors bind the TATA-box within the promoter, located approximately -25 bp upstream of the transcription start site (TSS), recruiting RNA polymerase. Activators binding to response elements within enhancer region up-regulate transcription by facilitating the assembly of RNA polymerase complexes. Conversely, repressors bound to silencer elements in the repressor region down-regulate transcription. When a repressor binds to the operator adjacent to the promoter within the repressor region, transcription is inhibited due to RNA polymerase blockage.

mRNA Transcription and Processing

Template (negative/anti-sense) strand 3' to 5' is used to transcribe pre-mRNA which is 5' to 3' which reflects coding strand DNA.

mRNA processing-Alternative splicing yields different mRNA combinations through pattern of introns removal.

Post-Translational Modifications

5' end cap is added to mRNA for ribosomal binding. 3' end poly-A tail is to prevent endonuclease from degrading coding region during translation in cytoplasm.

Cell cycle and mitosis

G1-G2 is interphase. At G1, cell grows larger, organelles are doubled, and protein expressed. There is a checkpoint between G1 and S phase. DNA is replicated at S phase. By G2, DNA and organelles are doubled. More cell growth occurs here to prep for mitosis (another checkpoint before mitosis). Mitosis occurs after in which cells are split in two. In case where cells don't divided more such as muscles and neurons, then cells goes into G0 phase.

Throughout G1 and G2 phases, cyclins are generated to activate CDK (cyclin dependent kinase) to phosphorylate TFs needed to pass checkpoints.

DNA mutations

Transition: purine to purine, pyrimidine to pyrimidine.

Transverse: purine to pyrimidine, pyrimidine to purine

Point mutations:

Silent- mutation of 3rd (wobble) nucleotide in codon doesn't affect translated amino acid.

Nonsense- STOP codon.

Missense- conservative, diff aa with similar characteristics

Nonconservative, diff aa with diff chemical characteristics

Cancer - metastasis, and treatment

Mnemonic: Don't Ramble To Anyone My Mate

1)DNA mutation

2) Resist apoptosis

3) telomerase extension

4) angiogenesis

5) metastasis started by metalloproteinase (chops up ECM so circulatory system can be accessed)

Treatment: Chemotherapy (stops division of epithelial cells, hair, blood cells, other mitotic cells), surgery- however cant remove ex hematopoietic stem cells,

ionizing radiation, immunotherapy.

Cancer - oncogenes and tumor suppressor genes

1 hit hypothesis: One protooncogene (genes affecting cell growth/proliferation) mutation is enough for all growth factor receptors to be activated constantly leading to proliferation of cancer cells.

2 hit hypothesis: p53 gene from both mom and dad must be mutated as one functional p53 protein TF (p53 protein functions as TF) can activate p21 to inhibit CDK which stops cell division checkpoints.

B-cells (B lymphocytes)

Extracellular process

All antibodies/receptors are unique through VDJ recombination of genes. Typical B-cell process: Antibody happens to match antigen->antigen precented on MPC2 complex while chopping pathogen. It further differentiates to memory and effector cells.

1) If non-peptide, multiply-secrete antibodies-attack pathogen

2) However, if antigen is peptide, then follow this pathway: APC (Antigen presenting cell-dendritic) follows similar process as B-cell but phagocytose nonspecifically and present antigen on MHC2. Helper T/CD4+ cells then bind their TCR (receptor) onto the APC. An APC/CD4+ complex allows for differentiation of the T-cells into effectors and memory cells. The effector cells can bind MHC2 of the B cell for multiplication and follow path 1).

Finally, pathogen can either be destroyed through (NOC) neutralization (blocking function), opsonization-antigen tagging (intruder) complement system in which proteins will burst pathogen. Agglutination (clumps the antigens together to make it easier for something like a macrophage to devour

This extracellular process is called humoral immunity.

Memory is for long term, while effector (plasma cells) brings short term antibody secretion. This is most energy efficient.

T-cells (T lymphocytes)

Intracellular process

All nucleated cells are constantly taking samples and displaying them on MPC1 complexes. They also do this at MHC2. CD8 will bind MHC1 while CD4 will bind MHC2. CD4 cells will then release cytokines to activate CD8 which will then multiply into memory and cytotoxic (killer) cells. These cytotoxic CD8 cells will bind other antigen infected cells and induce apoptosis to prevent replication of virus. This process is also called cell mediated immunity.

Autotrophs vs. Heterotrophs

Source of energy

Chemotroph-Redox

Phototroph-sunlight

Carbon source:

CO2- autotroph

Organic molecules-heterotroph

A type of chemotroph than doesn’t use O2 (anaerobic) are called lithotrophs.

As water has low oxidation potential, it requires sunlight to make oxygen. ETC is otherwise similar in chloroplasts.

bacteria vs. human cells

Human have membrane bound organelles. Both have plasma membrane (phospholipid bilayer). Gram negative: inner, thin cell wall (peptidoglycan), and outer membrane.

Gram positive: inner, thick outer cell wall.

Bacteria have 30 and 50 ribosome subunits; Humans have 40 and 60 ribosome subunits.

3 types of antibiotics, ex: Tetracycline inhibit bacterial ribosome, penicillin inhibit cell wall synthesis, Rifaximin inhibit RNA polymerase.

Virus Life Cycle

Class1: DsDNA

Class2: ssDNA+, ssDNA-

Class3:DsRNA

Class4:ssRNA+

Class5:ssRNA-

Class6:HIV Class

7:gapped DNA

Class 1-2 takes advantage of existing human DdDp and DdRp. For Class 2, you can make complementary DNA strand to form DsDNA, then process is the same.

Class 3-5 requires own RdRp.

RdRp can be used to duplicate any ssRNA+/-. Generally, ssRNA+ is used to express proteins.

HIV requires RdDp to form double stranded DNA which can integrate into human genome.

Mendelian genetics

Mendelian Laws, also known as Mendel's Laws of Inheritance, are fundamental principles in genetics discovered by Gregor Mendel. Here are the three laws along with mnemonics to help you remember them:

1. Law of Segregation:

Mnemonic: "Splitting Seeds" - Think of the letter "S" in "Segregation" and "Splitting Seeds" to remember that alleles (different forms of a gene) segregate or separate during gamete formation, so each gamete carries only one allele for each trait.

2. Law of Independent Assortment:

Mnemonic: "Allergy Apples" - Focus on the letter "A" in "Assortment" and "Allergy Apples" to remember that alleles for different traits are inherited independently of each other. Just like how apple allergies are unrelated to assorting different traits.

3. Law of Dominance:

Mnemonic: "King Dominates" - The letter "D" in "Dominance" and "King Dominates" can help you recall that in a heterozygous individual (having different alleles), the dominant allele will determine the appearance of the trait, masking the expression of the recessive allele.

Non-Mendelian Genetics

Hardy Weinberg:

In any population with two alleles for a gene, the allele frequencies obey the equation:

p + q = 1

In this population, three genotypes are possible. These frequencies are represented by the following terms:p2 represents the frequency of homozygous dominant genotypes2pq represents the frequency of heterozygous individualsq2 represents the frequency of homozygous recessive genotypes. Together, these terms must obey the following equation:

p2 + 2pq + q2 = 1

Mitosis

Mitosis is the process of cell division that results in two genetically identical daughter cells. Here are the steps of mitosis, along with a mnemonic to help you remember them:

1. Interphase (not part of mitosis, but an important preparation phase)

2. Prophase: Chromosomes condense and become visible. The nuclear envelope breaks down.

Mnemonic: "Pro phase" - think of the prefix "pro" meaning "before" to remember that this is the phase before mitosis really starts.

3. Metaphase: Chromosomes line up at the equatorial plane (the middle) of the cell.

Mnemonic: "Meet in the middle" - remember that the chromosomes meet in the middle during metaphase.

4. Anaphase: Sister chromatids separate and move towards opposite poles of the cell.

Mnemonic: "Apart" - both "anaphase" and "apart" start with "ap," which can remind you that the chromatids are pulled apart.

5. Telophase: Chromosomes reach the poles and decondense. The nuclear envelope reforms.

Mnemonic: "Two nuclei" - remember that during telophase, two nuclei are forming.

6. Cytokinesis: The division of the cytoplasm, resulting in two separate daughter cells.

Mnemonic: "Cytokinesis splits the cell" - think of "cytokinesis

DNA Repair

Direct reversal:

-photolyase in which MTHF use blue light to reduce FAD+ to break UV induced covalent bonds (typically pyrimidine dimers).

-MGMT use sulfur group to nucleuphillically break alkylation. Otherwise, G would bind T instead of C.

Can be more efficient and cost-effective for high frequency repair then BER.

Mismatch repair:

chops off mismatch and add correct nucleotide.

Nucleotide excision repair (broadly use):

Deal with bulky lesions created by UV radiations and certain chemical. Lesions that distort DNA. Endonucleases create nick and DNA polymerase replicate new DNA. Ligase seals the phosphodiester bonds.

NER usually recognized bulges from thymine dimers, pyrimidine dimers and polycyclic aromatic hydrocarbons (PAH)

mutations. Use this if 1) and 2) fails.

Base excision repair (broadly used)- Fix small, non-bulky lesions resulted from base damaged nucleotides in DNA (up to 6 nucleotides). Includes alkylation, oxidation, deamination, and depurination/depyrimidination.

Oxidation can lead to wrong can lead to distortion of base an eventual mismatch during replication.

Glycosylase excise damaged singular base. AP endonucleases sense the basic site and rest is similar to NER.

Homologous DNA repair ([HR]-homologous recombination):

DNA overhangs are created on each strand. If you have backup DNA from S phase, sister chromatids then open a bubble, and the nearest cut strand can bind with it. Correct DNA info is replicated and used to add info on the remaining strand. Ligase seals and complete repair. Non-homologous (non-homologous end-joining or NHEJ) is simply clean shaved, and ligased, and information is lost.

Endocrine system

Peptide hormones:

Anterior Pituitary: (FLAT PEG)

FSH, LH, ACTH, TSH, Prolactin, Endorphins, GH

Posterior Pituitary: ADH, Oxytocin

Parathyroid: PTH->Osteoclast-consume bones, up Ca2+

Thyroid: Calcitonin->Osteoblast-consume Ca2+, build bones

Pancreas: Insulin, Glucagon

Steroid hormones:

Adrenal Cortex: (AC) Aldosterone, Cortisol

Gonads: (PET) Progesterone, estrogen, testosterone

Tyrosine derivatives:

Thyroid: T3 & T4

Adrenal Medulla: (AMEND) Epinephrine, norepinephrine, Dopamine.

HPA axis (Hypothalamic-Pituitary-Adrenal):

Stress->Hypothalamus release CRH (corticotrophin release hormone) ->Anterior Pituitary release ACTH->Adrenal Cortex release Cortisol stimulating gluconeogenesis and breakdown of protein->Cortisol produce negative feedback on CRH and ACTH and their respective glands.

Embryogenesis and stem cells

Mnemonic: My Baby Grows Nicely

1)After fertilization, diploid zygote (totipotent) divides into 16-cell morula.

2) Blastulation forms blastocyst consisting of placenta and inner mass cell (ICM) which is pluripotent.

3) Gastrulation of ICM forms gastrula (multipotent) consisting of 3 layers:

Ectoderm (forms skin and neurons), mesoderm, and endoderm (digestive and respiratory tracts).

Mesoderm gives rise to hematopoietic stem cells in bones which can become lymphoid or myeloid.

4) Neurulation occurs in which ectoderm differentiate into neural plates that folds into neural tube which becomes CNS

Reproduction and development

HPG axis (Hypothalamic-Pituitary-Gonad)

Hypothalamus release GnRH (Gonadotrophic releasing hormone) to anterior pituitary gland. Anterior Pituitary release FSH and LH to gonads.

FSH; In men, promotes spermatogenesis through sertori cells in seminiferous tubules and promotes follicle maturation in women.

LH; In men, promotes maturation of testis & production of testosterone in leydig cells in testis and promotes ovulation leading to progesterone and estrogen production.

Spermatogenesis

Sperm pathway: (SEVEN UP) Seminiferous tubule, epididymis, vas deferens, Ejaculatory duct. Urethra, Penis

(Gorilla Cages In the Zoo)

Diploid Spermatogonium--(mitosis)-->Diploid Primary Spermatocyte--meiosis1-->two haploid Secondary Spermatocytes--meiosis2-->4 haploid Spermatids--maturation-->Spermatozoans

Diploid Spermatogonium undergoes mitosis to form primary spermatocytes. It then goes through meiosis 1 to form two haploid secondary spermatocytes. These then go through meiosis 2 to form four haploid spermatids. Finally, these mature into spermatozoans.

Oogenesis

Diploid Oogonium proceed to through mitosis to become primary oocyte. It's then arrested in prophase 1 until puberty. Completion of meiosis 1 produce haploid secondary oocyte and polar body. Then proceeds through meiosis 2 and forms 1 Ovum and 3 polar bodies. These are all haploids until fertilization by sperm.

During fertilization, acrosome of sperm penetrates Zona pellucida to fuse with ovum (Egg)

Menstruation Cycle

Ovarian and uterine cycle:

1. Follicular phase: Starts with menstruation in which uterine lining - endometrium is being shed (last for 3-7 days). Maturation of follicle from d7-14 and the secretion of estrogen from ovaries. Initially, there is low levels of estradiol/estrogen which cause negative feedback on hypothalamus and keeps FSH and LH levels low. As the ovarian follicle grows more mature, estradiol levels increase. At the same time, the low estradiol level cause arteries in the uterine endometrium to constrict, leading to menstruation. Uterine cycle's proliferative phase happens after menstruation and ends at ovulation.

2. Ovulatory phase- When ovarian follicle is mature, estradiol level has become so high that an increase in FSH and a spike in LH cause ovulation a day after. At the same time, the high estrogen level cause endometrium to thicken.

3. Luteal phase- Following ovulation, LH stimulate growth of Corpus Luteum from the follicular tissue left after ovulation. Corpus Luteum starts producing progesterone and estrogen. These cause a negative feedback loop on both Hypothalamus and Pituitary gland which keeps LH and FSH levels low. At the same time, endometrium continues to develop from stimulation of estrogen and progesterone (Uterine cycle-secretory phase). By day 28, if there is no fertilization/pregnancy, this uterine lining (endometrium) will shed through menstruation.

Basic Digestive System

In Stomach, Pepsin and HCL are responsible for breakdown of protein and making an acidic environment that also kills bacteria.

Pepsinogen from chief cells is the inactive zymogen that get activated by H+ from parietal cell's bicarbonate. HCL also promote this activation. Mucus from goblet cells protect stomach lining from this acidity.

In small intestine, chyme goes through duodenum, jejunum, and ileum.

Bulk of digestion happens in duodenum from enzymes secreted by accessory organs. Afterwards, the chyme pass through jejunum and ileum. These are characterized by having microvilli that increase surface area.

Non hydrophobic small molecules such as water, sugars, and most vitamins are absorbed to faciliated simple diffusion and secondary active transport. Hydrophobic vitamins K,A,D,E moves to lymphatic system by lacteals.

Large intestine: responsible for absorbing water and leftover salt; also contain gut flora. Fecal matter is stored in the last segment.

Accessory organs of the digestive system

Liver, produce bile that emulsify fat. It also produces albumin which is responsible for hormone transport in blood.

Gallbladder is located beneath liver and stores and secrets bile to small intestine when signaled by cholecystokinin (CCK).

Pancreas is both an endo/exocrine organ that produce (PAL) peptidase, amylases, and lipases when promoted by acinar cells. These enzymes enter duodenum through the pancreatic ducts signaled by secretin.

Activators/regulation: Enteropeptidase is responsible for cleaving inactive trypsinogen into Trypsin. Trypsin is responsible for activation of these pancreatic enzymes.

Excratory system

Glomerulus within Bowman's capsule filters protein from filtrate that enters nephron. At proximal convoluted tubule (PCT), salt and water are reabsorbed into efferent arteriole.

Moving down descending loop of Henle (DLOH), water gets reabsorbed as blood osmolarity/salinity increase. Loop of Henle is the saltiest point. Moving upward ascending loop of Henle (ALOH), salt is being pumped out creating this salty gradient around the loop using ATP.

Moving through distal convoluted tubule (DCT), sodium and water are being reabsorbed. At the same time, nearby blood excretes waste to DCT (H+, Urea, NH3+, and K+ -- mnemonic: Dump the HUNK). As filtrate move through collecting duct, some more water reabsorbing happens before the urine accumulate in the bladder.

Antidiuretic hormone acts on DLH and collecting duct, promoting available aquaporins.

Aldosterone acts on DCT, increasing (sodium) Na+ reabsorption which makes water follow as a result.

Muscle contraction

1) High energy state in which myosin in bound with ADP+Pi and is in cocked/rested position

2)Ca2+ bound to troponin create conformational change in which tropomyosin no longer block myosin-binding site, thus allowing for actin-myosin crossbridge.

3) Binding of actin-myosin release ADP+Pi, allowing for power stroke in which actin is brought closer to M-line, shortening the sarcomere.

4) ATP binds myosin and release it from actin, Ca2+ also disassociate.

5) Hydrolysis of ATP resets/cocks the myosin into resting state.

Bone structure

Long bones:

Characterized by wider epiphysis ends and shaft called diaphysis. Epiphysis is composed of spongy bone containing red bone marrow-site of hematopoiesis.

Yellow bone marrow is found in diaphysis cavities and stores adipose.

Compact bones make the walls of diaphysis and is characterized by its bone matrix made of osteons. Haversian canals run each osteon which is surrounded by concentric lamellae. Perpendicular to haversian canals are Volkmann's canals. Spaces between lamellae are called lacunae which stores osteocytes. Microscopic canals called canaliculi provide nutrients to osteocytes.

If Ca2+ is high, Thyroid secrete calcitonin to signal Osteoblasts to consume Ca2+ and build bones.

If Ca2+ is low, Parathyroid secrete PTH to signal Osteoclasts to consume bones to increase calcium in blood.

Tendons connect muscles to bone.

Ligaments connects bone to bone.

Cartilage: reduce friction in joints, becomes hardened bone; common type is hyelin cartilage.

Skin layers

Epidermis:

Mnemonic: Come, Let's Get Sun-Burned Pretty Red

Stratum Corneum: Outer layer that consist of flattened dead corneocytes.

Stratum Lucidum: Only exist in hairless skin.

Stratum Granulosum: Contains dead keratinocytes.

Stratum Spinosum: Contains Langerhans cells (immune) and

live keratinocytes (make keratin)

Stratum Basale: Contain proliferating keratinocytes, Melanocytes, and Stem Cells

Dermis:

Papillary Dermis: Contains Meissner and Merkel cells responsible for sensation of light/low frequency touch.

Reticular Dermis:

Bulbous Corpuscle: Stretching of skin.

Pacinian Corpuscle: Pressure and vibrations.

Hypodermis:

Connects muscle to bone/muscle. Contain adipose tissue.

Homeostasis: sweat and vasodilation (bring blood vessels closer to surface to cooldown when hot)

Blood composition

55% plasma, 45% erythrocytes, 1% leukocytes and platelets.

All made from bone marrow.

Circulatory Regulation

Bohr's effect:

As blood pH goes down due to increase of H+ and pCO2 (Bicarbonate buffer), more H+ are bound to heme and decrease its' affinity to O2. As a result, O2 is released from blood to deoxygenated tissues.

Increase in temp and increase in pH lowers the oxygen affinity of hemoglobin.

Endocrine:

Atrial natriuretic peptide (ANP) is a diuretic that decrease sodium absorption, thus water absorption.

As such, urine volume increase while thirst is increased. Aldosterone and ADH are antidiuretics that increased fluid retention and increase blood pressure. Pressure is increased because blood current is increased.

Related to Ohm's law.

Pressure=Blood flow (current) x Resistance (vessel friction).

R is modeled on poiseuille's law.

Length increase resistance, while radius decrease resistance.

However, going from arteries to capillaries, pressure and resistance is decreased as there are significantly more capillaries than arteries.

nervous system

PNS's Afferent sensory receptors send signal to CNS. Efferent signals go down from brain to involuntary autonomic nervous system or somatic nervous system that control skeletal muscles.

Autonomic nervous system can be further divided into sympathetic and parasympathetic nervous system.

Sympathetic-Fight/flight, stress response, increase HR, lower digestion, glycogenolysis, dilation of pupils and airways

Parasympathetic-rest/digest, lower HR, glycogenesis, constriction of pupils and airways.

Glial cells

Glial Cells:

CNS: Mnemonic: AMEO - sounds like Ammo.

1)Astrocytes: Forms blood brain barrier. Provide nutrients for neurons.

2)Microglia: Phagocytose pathogens and waste products

3)Ependymal cells: In lining of brain ventricles in which they produce cerebral spinal fluid.

4)Oligodendrocytes makes myelin in CNS.

PNS:

1)Satellite cells- structural support in PNS

2)Schwann cells make myelin in PNS.

Action Potential

Sodium potassium transporter use ATP to pump 3 Na+ out of cell and 2K+ into cell.

Resting potential is -70mV, while action potential is triggered at -55mV.

Excitatory/depolarizing channels: Acetylcholine regulated Na+ channels (chain reaction triggered at -55mV throughout neuron), Glutamate regulated K+ channels, terminal axon Ca+ channel at +40mV (influx of Ca2+) which releases neurotransmitters from presynaptic neuron to next post synaptic neuron.

Inhibiting/polarizing: GABA regulated Cl- channel, 50mV K+ regulated channel.

Brain regions

Mnemonic: Freud Tore Pants Off.

Frontal lobe-Executive function, motor, and speech (broca)

Temporal lobe-Auditory, learning/memory, speech perception

Parietal lobe-spatial perception, proprioception (kinesthesia), somatosensation (TPP-touch, pressure, pain)

Occipital lobe-visual processing