Lab Final

Question 1

Chordates

+ Phylogenetic tree

Answer 1

Chordates: phylum Chordata that includes true vertebrates → vertebrates: distinguished by possession of a backbone or a spinal column

Phylogenetic tree of chordates: evolutionary history; reaching back into the past
Mammals: one class of vertebrates
Amniotes: vertebrates adapted for terrestrial existence
Descended from jawed fishes

Question 2

Characteristics of Chordates (5)

Answer 2

1. Post anal tail: muscular; source of locomotion in aquatic species; signals and helps maintain balance in terrestrial species
   - - In humans, will be vestigial tail bone at the base of our spinal cord; non functional
2. Dorsal hollow nerve cord: develops into the brain and spinal cord; composes the central nervous system
3. Notochord: fluid filled; predates the spinal cord by providing some aspect of rigidity
   - - In humans, only exist in the embryo – will become the gelatinous regions in the vertebrae
4. Pharyngeal gill slits: openings in pharynx that extend to outer environment, allowing for filter feeding and O2 extraction
5. Endostyle / thyroid gland: located at base of throat; involved in iodine metabolism
   In humans, will become thyroid gland (endocrine) that secretes growth hormones

Question 3

“Idealized” Vertebrate Characteristics (8)

Answer 3

1. Cephalization facilitates mobility: front end moves with the environment, allowing for perception / response
2. Aerobic BUT can be anaerobic; however, vital organs are aerobic only (ie brain)
3. Homeostasis: higher internal temperature regulated, thus allowing for the fastest / most advanced nervous systems; found in homeotherms
4. Closed circulatory system: blood enCLOSED in system at all times within vessels of different sizes and wall thickness; more efficient at delivering blood and nutrients to tissues
   - - Versus open circulatory system: blood and interstitial fluid mix
5. Complex digestive system: food in one end, waste out the other
   - - Versus incomplete digestive system: one opening for both
6. Osmoregulatory systems: maintenance of homeostasis water content, specifically fluid balance and concentration of electrolytes; promotes optimal osmotic pressure; rids the body of toxins
7. Adaptive immune system: from the ancestral JAWED VERTEBRATES, thus all organisms have some form of immunity
8. Reproduce sexually (in most cases)

Question 4

Types of Tissue (4)

Answer 4

composed of cells; make up organs (which make up organ systems)

1. Connective: derived from mesoderm; bulk of the body; acts as the padding holding you together → incl adipose, bone, cartilage, blood
   - - Ground substance has extracellular matrix with embedded fibers
   - - Cells secretes extracellular matrix
2. Epithelial: “epi” = top or outermost lining
   - - Cells stitched together into sheets via protein junctions
   - - Free surface exhibits polarity (apical vs basal)
3. Muscle: allows for movement bc irritable and contractible
   - - Skeletal: banded and striated; voluntary movement
   - - Smooth: non striated; involuntary → muscle of the organs via vasoconstriction / dilution
   - - Cardiac: of the heart; slightly striated; involuntary
4. Nervous: coordination center of the body bc irritable and conductive
   - - Neurons: always working and conducting signals
   - - Glial cells: support cells of neurons; act as a blood brain barrier; can contract cancer

Question 5

Categories of Cells (2)

+ Types of Glands (2)

Answer 5

for epithelial cells

Shape:

1. Squamous: flat → ie skin
2. Cuboidal: cube shaped → ie. lining of tubes in kidney
3. Columnar: rectangular; used for absorption and secretion → ie. intestine, respiratory tract

Number of layers:

1. Simple: single later; good for diffusion
2. Stratified: many layers; good for protection

used for secretion

Exocrine: has a duct; reaches surface of lining

Endocrine: no duct; released into interstitial fluid and affects cells with appropriate receptors that respond → ie. hormones

Question 6

Body Plan of Typical Mammal – Problem, solution, extra tidbit

Answer 6

Problem: most cells are too distant from surface to enable diffusion to exchange materials with environment

Solution: have exchange surfaces with large surface areas and thin / permeable barriers + convective transport mechanism to get gases / nutrients / wastes to sites where diffusion can occur → basically another way to maintain homeostasis

• • Lungs SA = 180 m squared
• • Digestive tract SA = 300 m squared

Consider this: tube within a tube – any material inside the alimentary / digestive tract is still considered “outside” the body

Question 7

Covering and Lining Membranes (3)

Answer 7

Continuous multicellular sheets composed of EPITHELIUM bound to an underlying layer of CONNECTIVE tissue

1. Cutaneous: dry membrane (exposed to air) consisting of keratin (protein), stratified squamous epithelium (epidermis); derived from ECTODERM → ie skin
2. Mucous: moist membranes that line all open body cavities (in contact with environment), consisting of either stratified squamous OR simple columnar; also derived from ectoderm → ie lining of mouth
3. Serous: moist membranes that line all closed body cavities, consisting of simple squamous epithelium (specifically, mesothelium) resting on a thin layer of connective tissue; derived from mesoderm

Question 8

Body Cavities

+ Specific naming of serous membranes in regards to the cavity / organ (5)

Answer 8

lubricated sacs that hold a organs and allow for movement within them

1. DORSAL: cranial and vertebral
   - - Cranial: brain, cerebral spinal fluid
   - - Vertebral: spinal cord
2. VENTRAL: thoracic and abdominopelvic (separated by smooth muscle called DIAPHRAGM, involved in negative pressure breathing)
   - - Thoracic: circulatory system, respiratory system
   - - Abdominopelvic: digestive system, excretory system, reproductive system

1. Serosa: aka serise fluid; thin, double layered membrane that covers the walls of VENTRAL cavities and outer surfaces of organs
2. Parietal serosa: lines cavity walls → contrast to Visceral serosa, which folds in on itself to cover organs WITHIN the cavity walls
3. Parietal peritoneum: associated with lining of abdominopelvic cavities → contrast to visceral peritoneum, which covers the organs in the abdominopelvic cavities
4. Parietal pericardium: lines the pericardial cavity → contrast to visceral pericardium, which covers the heart
5. Parietal pleurae: line the walls of the thoracic cavity → contrast to visceral pericardium, which covers the lungs

Question 9

Superficial glands and nodes of the neck (4)

Answer 9

Submaxillary glands: aka salivary glands; secrete a solution of salts, water, mucus, and amylase (enzyme that begins sugar digestion in the mouth)

Parotids: also salivary glands; secretes salt, water, and amylase BUT less mucus than submaxillary

Lacrimal glands: secrete tears that both lubricate the eye and prevent bacterial infections; tears are made of salts, water, mucus, lipids, antibodies, enzymes, etc

Lymph nodes: secondary immune organs that filter lymph (leaked blood plasma); populated by B- and T- lymphocytes, macrophages, and circulating antigen presenting cells (aka APC or dendritic cells)

Question 10

Digestive system pathway + parts (5)

Answer 10

Part of abdominal cavity

Pathway: mouth, esophagus, stomach, small intestine (with accessory glands and cecum), large intestine, rectum, anus

1. Mouth: ingestion point with chemical (hydrolytic enzymes) and mechanical (chewing) digestion
2. Esophagus: moves bolus (chewed food); extends through the diaphragm and into the stomach
3. Stomach: large pouch-like expansion of the gut that stores and mixes the food and also begins the digestion of proteins by secreting proteases that convert proteins into manageable polypeptides
4. Small intestine: divided into three smaller region on the basis of functions and internal differences (duodenum, jejunum, ileum) → three main functions
   - - Neutralize the HCl secreted by the stomach
   - - Digest the carbohydrates, proteins, and fats into smaller macromolecules
   - - Absorb these monosaccharides, amino acids, and small peptides and fatty acids and diacylglycerol along with other nutrients (ie vitamins), salts and water into the blood → simple sugars, amino acids, nucleotide breakdown products into capillaries + fats into lymph vessels
5. Large intestine: recovers water from unabsorbed foodstuffs, which are then processed into fecal matter; bacteria here help with chemical breakdown of refractory compounds and synthesize some vitamins

Question 11

Helpers of the GI tract (4 ; 3sub2)

Answer 11

1. Mesenteries
2. Salivary glands
3. Accessory glands: inside small intestine; supply digestive enzymes, emulsifiers, and hormones that assist in digestion and absorption
   - - Liver: large and dark in color; detoxification, glycogen storage; also secretes bile (bile acids and pigments to help solubilize fat) and water, which are then stored in the gallbladder
   - - Pancreas: small and pinkish / grayish
   - —- Exocrine: digestive enzymes that hydrolyze proteins, carbohydrates, and fats and large quantities of bicarbonate ion HCO3- that neutralize the acidic chyme
   - —- Endocrine: glucagon and insulin; secreted into the blood to help regulate blood sugar levels
4. Cecum: located at junction of small intestine and large intestine; large diverticulum that stores bacteria that assist in enzymatic digestion of refractory carbohydrates (ie cellulose)

Question 12

Excretory system pathway + functions (5)

Answer 12

Also part of abdominal cavity

Pathway: arterial blood, kidneys, ureters, bladder, urethra → arterial blood is carried to the kidneys, which filter for liquid waste that is transported for storage via the ureters into the bladder until the excretion via the urethra

1. Homeostasis: control solute concentrations and balance water gain and loss
2. Excretion of metabolic wastes and toxins
3. Maintain pH of blood via recovery of HCO3- and excretion of H+
4. Stimulate red blood cell production in bone marrow by secreting erythropoietin
5. Activate vitamin D into calcitriol, thereby promoting Ca2+ absorption in the small intestine

Question 13

Reproductive structures of females (4) and males (6 + 4sub4)

Answer 13

Females

1. Ovaries: germ tissues where eggs are produced via meiosis
2. Oviduct: aka fallopian tubes; site of fertilization; provides the egg that is transported to the uterus
3. Uterus: site of implantation for a fertilized egg → humans are simplex (one large cavity); rats are duplex (aka horn of uterus; extend in a v shape towards the ovaries; allows for implantation of many eggs)
4. Vagina: birth canal that connects to the uterus at the cervix
5. Perovarial sac

Males:
1. Testes: germ tissues where sperm are produced via meiosis; located within the scrotum (pocket of skin)
2. Epididymis: coiled tubing where sperm mature and are stored until ejaculation
– Caput epididymis
– Cauda epididymis
3. Vas deferens: tube through which sperm are propelled during ejaculation on their way to the urethra (dual functions in male as excretion for sperm and urine)
4. Accessory glands
– Prostate: secretes most of the fluid of semen
Seminal vesicles: secrete a fluid high in fructose → accompanied by coagulating gland: secretes fluids that form a copulatory plug (can prevent backflow / interfere with the ejaculates of other males)
– Cowper’s gland: aka bulbourethral; secretes pre ejaculatory fluid to cleanse urethra
– Preputial gland: secretes smegma (acts as a moisturizer)
5. Seminiferous tubules
6. Penis

Question 14

Circulatory system (2) + functions (3) + defining attribute

Answer 14

Within thoracic cavity

1. Heart: pumps blood throughout the body; left side (to body) has more muscle than the right (to lungs); surrounded by pericardium
2. Thymus gland: located superior to the heart; primary immune organ where T-cell lymphocytes mature

Functions:

1. Transport nutrients, wastes, respiratory gases, hormones, lymphocytes
2. Stabilize internal pH
3. Regulate body temperatures

Defining attributes: transport of oxygen is most pressing / urgent, therefore minute to minute changes in tissue demand for O2 will drive changes in the rate of blood flow

Question 15

Respiratory System (2) + types of airways (2 both sub2) + negative pressure explained (3) + Tracheotomy

Answer 15

Within thoracic cavity

Lungs: convective air flow in and out of the body
Diaphragm: smooth muscle that participates in negative pressure breathing

1. Conducting airways: trachea and bronchi
   - - Trachea: windpipe; has cartilaginous rings to remain structurally open during negative pressure breathing
   - - Bronchi: branching of trachea into each lung
2. Respiratory airway: alveolar ducts and sacs
   - - 300 million alveoli provides total area of 120 to 140 m squared
   - - Gas exchange occurs with the blood in pulmonary capillaries

Negative pressure breathing explained:

1. Diaphragm and intercostal rib muscles contract, expanding the cavity and causing a drop in pressure within the lungs (negative pressure)
2. Air from the environment (positive pressure) rushes inwards to equilibrate pressure
3. Tidal ventilation mixes fresh inhalation with remaining air, allowing for the diffusion of CO2 and O2 to occur

Tracheotomy: within rat lab; reinflation of the lungs via manual introduction of air into the trachea (which has been incised to allow for the insertion of a pipette)

Question 16

Skeleton (3 ; 3sub2)

Answer 16

Axial skeleton: includes cranium, vertebral column, ribs, and sternum

Appendicular skeleton: includes pelvic girdles, pectoral girdles, and appendages

Vertebrate skeleton: composed of Ca3(PO4)2 (aka hydroxyapatite crystals) that are embedded in cartilaginous matrix, creating the bone; insoluble at acidic pH

• • Contrast to invertebrate skeleton: composed of CaCO3; soluble at acidic pH
• • Important bc vertebrates undergo intense / high bursts of activity that are often powered anaerobically → metabolic by-product of anaerobic metabolism is LACTIC ACID, which can reduce the pH of the blood

Question 17

Anatomical Position and Directional Terms (7)

Answer 17

use standard body position as reference point; for humans, just standing with feet apart and palms facing forward; for rats, on all four feet with head facing forward; right and left respective to organism being viewed (not viewer) → directional language streamlines meaning

1. Anterior: leading portion of body / faces the world first; for humans, ventral and anterior are the same → contrast to posterior
2. Ventral: belly side → contrast to dorsal
3. Lateral: towards the extremities → contrast to medial
4. Superior: towards the top of the body → contrast to inferior
5. Distal: away from point of reference → contrast to proximal
6. Cranial / Caudal: towards the head → contrast to cephalic
7. Superficial: on or near the surface → contrast to deep

Question 18

Body Symmetry – Body Axes (3) and Body planes (3)

Answer 18

Bilaterally symmetrical organisms can be divided in half BUT BY ONLY ONE PLANE

1. Anteroposterior / longitudinal axis: line extending from anterior to posterior directions (in humans, cranial to caudal)
2. Dorsoventral axis: line extending from the dorsal to ventral side
3. Transverse axis: line running laterally across the body (ie side to side)
4. Sagittal: vertical plane that divides body into left and right parts
5. Frontal / Coronal: vertical plane that divides body into anterior and posterior parts
6. Transverse: horizontal plane from RIGHT to LEFT that divides the body into superior and inferior parts

Question 19

Commonly misunderstood terms (4 ; 4sub1)

+ terms to just know

Answer 19

1. Alimentary canal: aka gastrointestinal tract; inner tube of digestive tract
2. Integumentary system: skin of outer tubing of digestive tract
3. Coelem: cavity in between alimentary canal and integumentary system bc space btwn the tubes are not solidly packed with cells
4. Peritoneum: lining of coelem; surface area therefore primarily epithelial tissue; sometimes divided by parietal / visceral peritoneum
   - - Mesentery: layers of peritoneum (connective tissure) that suspend and anchor the GI tract in the abdominal cavity; can support the vascular and nerve innervations

Terms to just know:

1. Cutaneous nerves: small, white strand-like structures that innervate the skin
2. Fat: padding for warmth and energy storage
3. Falciform ligament: attaches part of the liver and diaphragm to the abdominal wall
4. Facial nerve: white strand similar to the parotid duct but more dorsal; somatic motor nerve; innervates some of the facial muscles

Question 20

Superficial glands

• • near neck
• • near genitalia

Answer 20

Salivary glands: two parotids and two submaxillary glands; controlled by autonomic nervous system

• • Submaxillary glands: aka salivary glands, medial on ventral surface; secrete a solution of salts, water, mucus, and amylase
• • Parotids: on sides of submax; secretes salt, water, and amylase BUT less mucus than submaxillary; has a white duct
• • Amylase: enzyme that begins sugar digestion in the mouth
• • Mucus: glycoprotein that facilitates mastication and movement of food through the esophagus and the rest of the GI tract

Lymph nodes: four, anterior to submax (look like mung beans); secondary immune organs that filter lymph (leaked blood plasma); populated by B- and T- lymphocytes, macrophages, and circulating antigen presenting cells (aka APC or dendritic cells)

Lacrimal (tear) glands: lateral and anterior to the parotids (large, in charge, and dark); connects to the eyes via lacrimal duct; secrete tears that both lubricate the eye and prevent bacterial infections; tears are made of salts, water, mucus, lipids, antibodies (immunoglobulins), enzymes (ie lysozymes)

–
NEAR GENITALIA
Preputial gland: found in both male and female rats; paired structures found lateral and anterior of the external genital opening; exocrine glands that produce pheromones involved in communication

Question 21

Histology of the Kidney

• info
• pathway
• functions (3)
• extras (4)

Answer 21

Part of the excretory system → Inner medulla and outer cortex that are packed with ~1 million nephrons, including blood vessels, two capillary beds, and a “portal system”
Nephrons: composed of glomeruli; three tasks when processing blood → aka the “portal system”; 2 capillary system process of the blood before it returns to the heart

Pathway: Bowman’s capsule > proximal convoluted tube (partly in cortical) > loop of Henle (connection; located in medulla) > distal convoluted tube (partly in cortical) > collecting duct (make the final adjustments to filtrate compositions, in response to the hormones secreted from the brain)

1. FILTRATION of plasma from glomerulus into nephron tube
2. REABSORPTION of valuable solutes by cells in the walls of the nephron tubules
3. Active SECRETION of toxins, urea, and H+ ions into filtrate (urine) by cells in the walls of nephron tubules

• • Ureter: duct transporting urine from the kidneys to the bladder
• • Urinary bladder: hollow muscular organ that stores urine from the kidneys before disposal
• • Urethra: duct transporting urine from the bladder out of the body
• • Adrenal glands: aka suprarenal; located above the kidneys; endocrine glands that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol

Question 22

Histology of Duodenum (3)

Answer 22

Villi: folds that increase the surface area of the intestine

Mucosa (innermost) with three sublayers:

1. Submucosa: areolar connective tissue; vascularized and innervated with lymphoid follicles and exocrine glands
2. Muscularis externa: inner layer of circular muscles and outer layer of longitudinal muscles; segmentation and peristalsis (involuntary, wavelike motions that propel contents within an organ forward)
3. Serosa: visceral peritoneum

Question 23

History of skeletal muscle

Answer 23

Derived from mesoderm; use Ca2+ to trigger contractions; more than one nucleus

Striations: represent the orderly arrangement of actin and myosin in sarcomeres (functional units of skeletal muscles)

Skeletal: striated and voluntary; multinucleated; cells are electrically isolated from each other → Ca2+ ions bind to troponin to allow myosin and actin binding

Smooth: non striated and involuntary; uninucleate (one nucleus per cell); cells electrically coupled together via gap junctions → Ca2+ ions bind to calmodulin to allow for myosin and actin binding

Cardiac: striated and involuntary; at most 2 nuclei per cell; cells are also electrically coupled via gap junctions → Ca2+ ions also bind to troponin to allow myosin and actin binding

Question 24

Taste

+ Pathway

Answer 24

Aka modalities; help determine the nutritional value of what we eat and prevent the consumption of toxins → flavors: combination of the perception of taste, smell, and feel of the food in the mouth

Five categories: sweet, savory (umami), salty, sour, bitter

• • GPCR: aka G protein-coupled receptors; for sweet, savory, or bitter
• • TAS2R: family of GPCRs that are activated by bitter compounds

Pathway of Tasting

1. Compound enters mouth and comes in contact with the papillae (tongue bumps).
   - - Papillae: bumps of the tongue; contains multiple taste buds, filled with gustatory cells (~80; modified epithelial) arranged around a central taste pore
2. Partial breakdown by enzymes in saliva will allow food particles to reach the microvilli within taste pores.
   - - Microvilli: basically the tip of each taste bud; membrane of which will have thousands of membrane-bound taste receptor proteins exposed to food molecules dissolved in saliva
3. Activation of GPCRs will stimulate afferent neurons that will travel to the gustatory cortex in the temporal lobe of the brain.

Question 25

Sensory pathway basic functions

Answer 25

1. Sensory recognition: capture a form of energy (stimulus) that leads to a graded potential in receptor cells → Sensation: being aware of a stimulus
2. Transduction: converting the graded receptor potential into an action potential → basically, sensation is now transduced into a nerve impulse
3. Transmission: action potential travels to the central nervous system (brain and spinal cord)
4. Perception: interneurons provide the meaning of the stimulus → brain builds perception of the taste / molecular structure (can also extend to hearing, seeing, etc)

Overall: detection and processing of sensory information allows for generation of motor responses, which is the physiological basis of animal behavior.

Question 26

Taste transduction mechanisms for SALTY and SOUR

Answer 26

1. Ionotropic receptors: ion channel in the taste cell membrane that allow ions to flow into the cell via depolarization (opening voltage-gated Na+ in / K+ out / Ca2+ in channels in the ER membrane to open), changing the internal pH and composition of the cell → allows you to perceive sour and salty
   - - Sour = more H+ inside, lower pH
   - - Salty = more Na+ inside, therefore more positive inside the cell
2. Increased cytoplasmic [Ca2+] mobilized synaptic vesicles to fuse with cell membrane and release neurotransmitters into synaptic cleft btwn taste receptor and afferent sensory neuron
3. Once signal exceeds threshold in postsynaptic sensory neuron, action potential will travel to the gustatory centers of the brain
   - - More salt = more gates opened = more fusing of synaptic vesicles to cell membrane = more release of neurotransmitters = brain can tell btwn high and low salt content of the food

Question 27

Signal transduction mechanisms for SWEET, UMAMI, and BITTER (2)
+ Pathway

Answer 27

Umami: reflect the flavor of amino acids
GTP: important in translation; energy rich molecule that is not as widely used as ATP
– GDP acts as a switch; if nothing is attached, then considered off → if umami attaches, then GDP released as GTP

Pathway:
Use metabotropic receptors; membrane bound → GPCR, largest family of receptors; membrane bound; all members have 7 transmembrane helices

1. Taste substances bind to cytoplasmic domain → GPCR changes shape, triggering a response for the intracellular G protein to activate an effector molecule → increases [secondary messenger], thus single transduction signal amplified
   - - FOR SWEET: activated G protein gustducin activates adenylate cyclase → adenylate cyclase catalyzes conversion of ATP to cAMP → cAMP activates protein kinase that phosphorylate and closes K+ channel → depolarization causes Ca2+ channels in ER membrane to open
   - - FOR BITTER: activated G protein transducin activates phospholipase C (PLC) → PLC catalyzes conversions of PIP2 into secondary messenger IP3 → IP3 binds to Ca2+ channels in ER membrane, opening them
2. Influx of Ca2+ ions into cytoplasm mobilize synaptic vesicles to migrate to PM and release neurotransmitters, which trigger AP in afferent sensory neurons

Question 28

Tasting Lab (5)

Answer 28

Blue dye: allows for visualization of the quantity of papillae density bc density can affect taste sensitivity→ bumps without taste buds will stain blue; bumps with taste buds will stain light blue

Agonist: bind to receptor and mediate the typical ligand receptor response; promoter

Antagonist: bind to the receptor and lessen / block the typical ligand receptor response; blocker

Gymnema: brown liquid; herb from India used to treat diabetes; antagonist for sweet receptors, specifically T1R2 and T1R3

Miraculin: aka M-berry; protein extracted from a West African fruit; @ neutral pH, antagonist for sweet; @ acidic pH, antagonist for sour, agonist for sweet

Question 29

Journal Article Analysis

• ptc genetics
• haplotype (2)
• presense (2)
• prop vs ptc
• benefits to being taster / nontaster

Answer 29

PTC genetics: aka phenylthiocarbamide; coupled with the taste receptor TAS2R38 due of the bitter taste modality compounds with N-C=S moiety (part / functional group of a molecule)

Haplotype: particular set of genetic variations that are inherited together on one chromosome → most common: PAV are tasters (dominant), AVI are non tasters (recessive); heterozygotes were intermediate tasters; inherited in a Mendelian fashion

• • SNP: single nucleotide polymorphism;
• • Lesser common (intermediates) PVI, AAI, AAV activated 40% when compared to PAV → may be caused by membrane targeting or impaired coupling of receptor with signal transduction G proteins

Presence of Thymine @ position 785 of AVI prevents restriction Fnu4H1 from curring, thus the DNA remains intact as a 303 bp fragment; presence of Cytosine @ position 785 is the correct (think: C = correct) sequence for cutting and subsequent digestion of the PCR product, yielding 2 DNA fragments of 238 and 64 np.
Presence of Alanine @ position 49 and Valine @ position 262 diminishes receptor function but variation @ position 296 had little effect

PROP vs PTC: test proxy for PTC BUT not interchangeable; however, will be similar at low concentrations; former not as reliable because sensitivity can fluctuate due to genome of individual
– All alleles are expressed, therefore PTC insensibility must be due PTC not activating AVI (as opposed to not expressing the allele to not sense PTC)

Tasters good for rejecting possible poisons and therefore surviving (ie dislike smoking); non tasters good for being able to eat a larger range of compounds unbothered (ie can eat broccoli BUT over ingestion of isothiocyanates can lead to thyroid disease and goiter)

Question 30

Physiological responses to exercise – anaerobic (3)

Answer 30

During exercise, actively contracting muscles requires lots of ATP BUT have limited ATP stores

Phosphagen: creatine phosphate (in skeletal muscle) that can be converted into ADP (see manual)
– Together, creatine phosphate and stored ATP allow for prolonged excercise outside of aerobic capacity

Vigorously contracting muscles COMPRESS blood vessels, impairing blood flow and therefore oxygen exchange. Thus, ANAEROBIC processes provide additional ATP, which can prolong muscle action for about one minute.

• • Glycolysis (anaerobic) is 2.5x faster BUT is more inefficient than full blown aerobic resp (ie glycolysis > kreb > oxidative phos) → 2.5 ATP yield versus original XX amount
• • Anaerobic ATP production causes accumulation of lactic acid, contributing to muscle soreness

Question 31

Physiological responses to exercise – aerobic

Answer 31

Prolonged activities are powered aerobically → when full engaged (within 15 min), O2 is delivered to contracting muscles by combined actions of the cardiovascular and respiratory systems

Mitochondria use the O2 as a final electron acceptor, which generates the highest yield of ATP (~32 ATP / glucose)

Increased energy expenditures
– Both intrinsic and extrinsic factors can improve CO and ventilation rates

Arterioles (remember vasoconstriction and vasodilation) actively contracting muscles vasodilate in response to local chemical conditions (ie decreased [O2], pH and increased [H+], NO (nitric oxide), and prostaglandins)

Sympathetic nervous stimulation induces widespread vasoconstriction of arterioles to minimize blood flow to areas that can wait → want to increase stroke volume in the areas that are currently working (ie not digestive viscera and skin)
Total peripheral resistance: something about increasing blood viscosity / pressure as a result of vasoconstriction

Question 32

Basics of the cardiovascular system

Answer 32

1. Pulmonary and systemic circuits are in series, therefore both must pump equal volumes of blood BUT pulmonary is a LOW PRESSURE circuit (bc goes to lungs; keeps them dry)
   - - Pulmonary edema is dangerous bc gas will diffuse 200x more slowly if there is too much liquid → gas exchange will almost stop and you’ll basically suffocate to death
2. Human heart is MYOGENIC → electrical impulses originates in specialized conducting cells
   - - SA Node: aka pacemaker; has the fastest rate of depolarization
3. Impulses from SA node will spread through conducting fibers and from cell-to-cell through gap junctions
4. Depolarization from SA node spreads throughout the atrea, pumping blood into ventricles
5. Impulse arrives at AV node, pauses (allows atria to empty itself of blood before the ventricles contract) and then spreads to the ventricles via Bundle of His and Perkinje fibers.

Question 33

ECG/EKG – electrocardiogram (3)

Answer 33

Measures electric current through the heart → waves go P / QRS / T

P wave: 0.8 seconds – caused by spread of impulse through the atria; approximately 0.1sec after P wave, the atria will contract
Expelling of blood from the atria prior to ventricular systole (contrast to atrial systole)

QRS complex: results from rapid ventricular depolarization (0.08 sec) and precedes ventricular contraction; complicated shape results because the path of impulse waves changes continuously through ventricular (ie moves down AV node and then changes directions as weak signals move through interstitial fluid) → Bundle of His and Purkinje fibers
Overwhelms repolarization of atria

T wave: caused by ventricular repolarization (0.16 sec) → repolarization slower than depolarization, therefore T wave is more spread out

Question 34

Increase in cardiac output (mL/min) during exercise
+ influences of HR
+ influences of SV

Answer 34

CO = HR (bpm) * SV (ml/beat)
= Total blood volume passes through each side of the heart each minute

During exercise, CO can increase 4-5x in non athletes (20-25 ml/min) ; 7x in athletes (35 ml/min) ; 10x when skeletal muscles as arterioles vasoconstriction blood flow to non targets

HR influenced by intrinsic and extrinsic factors

• • Intrinsic: SA node sets pace; increases when atria stretched during venous return → think about the volume of blood that is returning to your heart. During exercise, the skeletal muscles are pushing large amounts of blood back, which will stretch the atria
• • Extrinsic: sympathetic stimulation of SA node by norepinephrine, epinephrine, thyroxine

SV influenced also by intrinsic and extrinsic factors

• • Intrinsic: stretching of cardiac muscles increases force of contraction (Frank-Starling law)
• • Extrinsic: sympathetic innervation of cardiac muscles increases contractility

Question 35

Blood pressure at rest (4)

Answer 35

Systolic blood pressure: larger number; determined by how strongly the left ventricle contracts during systole

Diastolic blood pressure: lower number; determined by the “stretchiness” of the aorta and large arteries that sustain the arterial pressure during diastole

Mean arterial pressure (MAP) has about one third difference between systolic and diastolic pressures (ie ventricular systole has a one third duration of cardiac cycle)
– During exercise, MAP increases only slightly due to vasodilation of arterioles servicing active skeletal muscles, thus reducing TPR (total peripheral resistance)

Biggest drop off at arterioles due to reduced diameter of arterioles (0.0037 cm) vs arteries (1.5 cm).

Question 36

Measuring blood pressure

+ Measuring ECG to determine heart rates

Answer 36

1. Blood pressure in brachial artery used to estimate systolic and diastolic blood pressure in arteries and aorta
2. Pressure cuff is inflated to obstruct blood flow through brachial artery
3. Cuff pressure is gradually lowered until it is just below systolic pressure → blood will now spurt through and turbulent blood flow (ie Korotkoff sounds) can be heard with a stethoscope
   - - First Korotkoff sounds indicates systolic pressure
   - - Korotkoff sounds disappear as cuff pressures falls below diastolic pressure

Measuring ECG

1. ECG are measured for student volunteers at rest and following exercise
2. Duration (in seconds) from R peak of QRS complex to the next R peak estimates duration of a single heartbeat → duration indicates systole
3. Exercise increases heart rate, therefore increases T to P and decreases R to R → BUT P to T is fairly consistent

Question 37

Pathway of Exercise

Answer 37

1. Inhale O2 rich air
2. O2 rich blood carried from lungs to body
3. Exercising muscles use O2 and ATP, producing CO2
4. CO2 enriched (O2 depleted) blood returns to the heart
5. O2 poor air returns to lungs
6. Exhale CO2

Question 38

Equations to know (7)

Answer 38

Calculation of Cardiac Output
CO = HR * SV
– Both left and right ventricles pump nearly identical volumes at the same rate

Calculation of Mean Arterial Pressure
MAP = CO * TPR = ⅓ (Ps - Pd) + Pd → TPR = MAP / CO

Calculation of SV from pulse pressure
SV = 1.7 (Ps and Pd)
– Close linear relationship

Calculation of heart rate:
HR = 60 * 1 / (RR time interval)

Calculation of TPR (total peripheral resistance)
TPR = MAP / CO
– Yield estimation of overall constriction or dilation of arterioles leading to tissues and organs of the systemic circulation

Calculation of lung ventilation rate
Lung ventilation = TV * breathing rate
– During excercise, TV and BR increase while IRV and ERV decrease

Calculation of vital capacity
VC = TV + IRV + ERV

Question 39

Cardiovascular system – terms to know

Answer 39

Electrocardiogram: measures electrical currents going through the heart via surface electrodes that are placed on the skin

Cardiac output: determinant of cardiovascular function; expected to increase with exercise due to increased HR and SV

Heart rate: number of times the blood is pumped out per minute

Stroke volume: volume of blood pumped out during each beat

TPR (total peripheral resistance): controlled by changing the size of systemic arterioles; the more dilated, the less resistance

Question 40

Respiratory system – terms to know

Answer 40

Tidal volume: volume of air that you breath in and out during normal breathing
Inspiratory reserve volumes (IRV): maximum volume attained during forced inhalation

Expiratory reserve volumes (ERV): maximum volume exhaled during forced exhalation

Vital Capacity: total volume of air that can be expired after a maximum inspiration

Residual Volume: small volume of air remaining in the lungs after the maximum expiration; used to keep the lungs open

Question 41

How are the heart, blood vessels, and breathing regulated to maintain homeostasis of O2 and CO2?

Answer 41

Sympathetic nervous system: “fight or flight” system

Activated during exercise to release norepinephrine and epinephrine (aka adrenaline) onto the sinoatrial node (pacemaker), inducing the sending of impulses more often, which increases the heart rate → more blood is thus sent to the ventricular cardiac muscle

Cause vasoconstriction (arterioles constrict), decreasing blood flow to parts of the body that are not exercising ;; causes vasodilation (arterioles expand), increasing blood flow to parts of the body that are exercising

Negative control feedback: controlled variable is sensed by the nerves; medulla oblongata (brain stem) receives signals; activate sympathetic nerves to the heart and blood vessels, in addition to nerves to the respiratory muscles to alter their activities → may have positive too?

Question 42

Human PTC Gene TAS2R38 (4)
2sub2
3sub2
4sub3

Answer 42

1. PTC Taster genes code for a GPCR membrane bound receptor (chromosome 7) which responds to compounds with N-C=S
2. Within coding region are three SNPs (inherited together to form HAPLOTYPE)
   - - SNPs: single nucleotide polymorphism; point mutation (substitution)
   - - When inherited together produce the NON TASTER haplotype known as AVI (three amino acids of a non taster; Ala-Val-Iso) → taster allele is known as PAV (Pro-Ala-Val)
3. PCR Primers designed to amplify a 303 bp amplicon containing the 2nd SNP can be used to genotype the allele following restriction digestion using Fnu4H1
   - - Cloning of a piece of DNA that has at least one SNP via PCR → lets you know whether individual is heterozygous or homozygous recessive
   - - Restriction digestion: bacterial immunity; can cut foreign DNA at recognition sequence
4. 2nd SNP @ position 785 is located within a recognition sequence of the restriction endonuclease Fnu451 → will be cut if you’re a taster (if not cut, then non taster)
   - - Sequence in question → 5’ - GXNGC - 3’ where X is the SNP
   - - Presence of Thymine @ position 785 of AVI prevents restriction Fnu4H1 from curring, thus the DNA remains intact as a 303 bp fragment
   - - Presence of Cytosine @ position 785 is the correct (think: C = correct) sequence for cutting and subsequent digestion of the PCR product, yielding 2 DNA fragments of 238 and 64 np.

Question 43

Some of the experimental procedures in Bufe et al. 2005

+ contrast

Answer 43

HEK293 cells transfected with PAC and AVI alleles (DNA)

Transfection: introduction of foreign gene into eukaryotic cell → contrast to transformation, introduction into bacterial cell (plasmids)

1. Receptors then expressed in cell membrane of human embryonic kidney cells, genetically engineered cells that are working appropriately.
2. Monitor via Fluo-4 Calcium Indicator → binding of calcium to Fluo4, which fluoresces (you can measure this, therefore quantitative)

–

Contrast to psycho genomic testing

1. Extract DNA of the individual you want to test
2. Perform restriction analysis (aka DNA fragmentation) to identify genotype
3. Provide individuals with the substance and they give their responses (more qualitative)

Question 44

RT-PCR

Answer 44

Reverse Transcriptase - PCR

1. mRNA extracted from human tongue tissue and amplified using RT-PCR to create cDNA
   - - Reverse transcriptase: RNA back into DNA; enzyme that retroviruses; yields complementary DNA strands
   - - mRNA extraction is super easy → wash with a poly U tail to catch mRNAs with long poly A tails (aka affinity chromatography)
   - - Extension of 3’ end to create a duplex (something) to yield cDNA yield
2. Levels of mRNA were determined using quantitative RT-PCR
   - - Lots of variability but want to measure expression → quantify how much cDNA was produced from different individuals
   - - Use TAQMAN PROBE: located in middle of amplicon, complementary to part of the template sequence; proportional to copy number of mRNA; has a fluorescent dye attached to it
   - —- Has a quencher at the 3’ end – probes lack OH at 3’ end → any fluorescence while the probe is intact will be absorbed by the quencher
   - —- Standards of known concentrations of cDNA generate standard curve to which fluorescence of unknown sample is compared
   - - Exonuclease: happens 3’ to 5’ ; degrades nucleotides starting at 5’ end though → degradation of probe nucleotides releases fluorescence
   - —- Contrast to DNA polymerase, which happens 5’ to 3’
   - —- Proofreading: allows DNA polymerase to back up in order to correct a mistake → 3’ to 5’ direction of the DNA polymerase in the presence of TAQMAN (exonuclease)
   - - Threshold of detection for fluorescence → aka Ct
   - —- The more DNA you start with, the sooner you will reach that threshold
   - —- Can compare DNA lengths and then plot that information → [DNA] horizontal; Ct vertical → linear slope downwards
3. in situ hybridization of circumvallate taste papillae with sense and antisense cRNA (bc cRNA is double stranded)
   - - In situ hybridization: taking a single strand DNA probe that will bind to an mRNA for expression – production of a spot that you can see
   - - Sense: same sequence as mRNA
   - - Antisense: complimentary to sense strand; template during transcription

Question 45

Negative feedback mechanisms to control heart rate during exercise (3)

Answer 45

Specifically SHORT TERM:

Baroreceptors: in carotid sinuses and aortic arch send impulses to cardiovascular center in the medulla oblongata

Chemoreceptors: in carotid and aorta relay information regarding [CO2] and pH to cardiovascular center in medulla

Hormonal controls: epinephrine (adrenal medulla), thyroxine (thyroid gland), and norepinephrine (sympathetic stimulation) accelerate CO thus increasing blood pressure

Question 46

Mammalian Respiratory System (4)
1sub1
2sub2

Answer 46

Convection alternating Diffusion

1. Convective motion of air ceases inside of alveoli; due to small diameter, diffusion is sufficient for exchange of O2 and CO2 with blood
   - - Tidal ventilation mixes fresh air with stale air in alveoli of the lungs → 12% fresh and 88% stale
2. Alveoli made from squamous epithelium (good bc thin diffusion barrier with large SA, allowing for rapid diffusion)
   - - Type 1: make up bulk of membrane → has a membrane responsible for gas exchange
   - - Type 2: secrete the surfactant (mixture of lipids and proteins) that reduce surface tension in water (reduces the H bonding of water to reduce the heavy presence of water in the alveoli) → no water film to prevent gas exchange
3. Gases are moving down their concentration gradient (ie CO2 diffuses back into the air from the blood and then O2 enters the blood again)
4. Ventilation rate and CO are well matched → harder you breathe, the faster your heart beats

Question 47

Respiratory centers in the brain stem (4)

Answer 47

1. Set basic ventilation rate and respond to chemosensors in the aorta and carotid arteries
   - - Eupnea: basic ventilation at rest → usually 10 - 12 breaths / min but if people know they’re being measured, can fluctuate
   - - Hyperpnea: increase of ventilation during exercise → increase by 10x to 20x
2. pH, P(CO2), and P(O2) sensors monitor blood in aorta and carotid arteries; afferent sensory input to respiratory centers in medulla
   - - Afferent: towards the brain
   - - Efferent: from the brain
   * * Increasing P(CO2) or falling pH (PO2 < 60 mmHG) increase ventilation
3. Exercise enhanced ventilation not prompted by rising P(CO2) or falling pH, P(O2) for two reasons:
   - - Ventilation increases abruptly as exercise begins
   - - Although venous levels change, arterial P(CO2) and P(O2) remain constant during exercise
4. Three neural factors involved
   - - Psychological stimuli (conscious anticipation)
   - - Cortical motor activation of respiratory centers in brain stem
   - - Excitatory impulses from proprioceptors in moving joints, muscles, and tendons

Question 48

Mechanisms of early embryonic development (4 ; 4sub1)

Answer 48

conserved among nearly all animals, especially early stages

1. Fertilization
2. Cleavage
3. Gastrulation: forming of three germ layers (endo, meso, ecto)
4. Neurulation (formation of a neural tube) and organ development
   - - Usually a result of interactions / release of chemical signals between the germ layers → Mesoderm produce neural cords to the ectoderm, which insulates it, creating the neural tube

Question 49

Bilateral animals divided into two groups

• • Protosomes
• • Deuterosomes

(3 ; 1sub2 ; 3sub2)

Answer 49

based on differences in early gastrulation and fate of blastopore (or functionally equivalent structure in humans is the primitive streak)

• • Proto: mostly invertebrates → “first mouth”
• • Deutero: includes chordates and echinoderms → “second mouth” (anus develops first)

1. In both bilaterian groups, fertilized egg divides repeatedly via cleavage until 8 cell stage, where differences in orientation can be seen
   - - Proto: offset division yields spiral cleavage → if splits at this stage, will die
   - - Deutero: stacked division yields radial cleavage → if splits at this stage, then have twins
2. Once the dividing cells rearrange into a round hollow ball, one wall begins to indent (via gastrulation) to form a blastopore (opening) where the indented cell walls will form the gut
3. As cells migrate within the embryo, they organize into three layers: ectoderm, endoderm, and mesoderm.
   - - Schizocoelom: typical of proto and higher vertebrates; formed by splitting of mesoderm to form the body cavity
   - - Enterocoelem: typical of deutero; mesoderm formed by punching of outpocketings of the archenteron (embryonic digestive gut)

Question 50

Fertilization lab with sea urchins (5)

Answer 50

Marine animals: traditional way to reproduce is to eject their gametes into the water and just let them have at it; usually released in a synchronized manner (in lab, will use CaCl as trigger)

1. Swimming sperm comes in contact egg molecules in jelly coat, triggering acrosomal reaction
   - - Jelly coat: maintain species to species recognition
2. Acrosome releases enzymes that digest a path through jelly coat.
   - - Acrosome: sac at the top of sperm head; derived from the golgi → when it recognizes the proteins in the jelly coat of the egg, it will burst to release the enzymes
3. Species-species recognition btwn acrosomal process of sperm and receptor proteins on egg triggers PM (plasma membrane) fusion when the sperm-binding receptors trigger
   - - Vitelline layer: surrounds the outer surface of PM of ovum
   - - Polyspermy: fertilization by more than one sperm; lethal for an egg
4. Entry of sperm nucleus causes an influx of Na+ (more positive inside) > egg rapidly depolarizes > prevents additional sperm from binding to PM → FAST BLOCK to polyspermy via electrical barrier
5. Depolarization of egg opens Ca2+ channels in the ER > creation of fertilization envelope → SLOW BLOCK to polyspermy via physical barrier (happens in humans)
   - - One of the cortical enzymes is a trypsin-digesting protease that cleaves proteins attaching vitelline layer to the PM layer of the egg.

Question 51

Ca2+ distribution correlates with formation of fertilization envelope (3)

Answer 51

Taken by chemically freezing the egg and tracking the progress of the egg with a calcium flux (by using something that fluoresces when calcium is present)

Ca2+ known to promote fusion of vesicles to PM; will release from ER and trigger cortical granule exocytosis and subsequent fusion with PM to begin forming fertilization envelope.

Cortical granules contain enzymes (specifically, rypsin-digesting protease) that cleave proteins attached vitelline layer to the PM layer of the egg and digested particles cause osmotic swelling beneath vitelline layer; finish forming fertilization envelope as vitelline is released from PM.

Question 52

Cleavage (3 ; 2sub3 ; 3sub2)

Answer 52

Defined as the repeated mitotic cell division of a zygote with little or no growth; cell cycle during cleavage is Synthesis > Mitosis > S > M … → With each division, cells (called blastomeres) will become smaller

Cleavage patterns reflect the amount of yolk stored in the zygote: three levels of yolk deposition

1. Microlecithal: slight amount → sea urchins, humans (primarily get nutrients from placenta)
2. Meso: moderate
3. Macro: enormous → reptiles

YOLK impedes cytokinesis

• • When the yolk is sparse, mitotic furrows pass successfully through entire zygote → HOLOBLASTIC CLEAVAGE (centered blastocoel)
• • When yolk is plentiful, mitotic furrow is slowed, only a portion of the cytoplasm is cleaved → MEROBLASTIC CLEAVAGE (off center blastocoel)

Question 53

Sea Urchin + Frog Example

Answer 53

Sea Urchin example: microlecithal yolk, holoblastic cleavage → blastocoel (fluid filled cavity) is centered inside the blastula

Frog example: also holoblastic BUT mesolecithal yolk

• • First two divisions along meridian between animal and vegetal pole; cleavage delayed in vegetal pole by mesolecithal yolk.
• • During third and subsequent divisions, yolk displaces towards cleavage furrow towards animal pole, resulting in more division and smaller blastomeres near animal pole → blastocoel forms entirely in animal hemisphere

Question 54

Gastrulation in frogs (3 ; all sub 1)

Answer 54

1. Gastrulation begins on the dorsal side (opposite where the sperm enters the egg) as cells involute over the dorsal lip into the interior, forming the blastopore
   - - Involusion: inward movement of an expanding outer layer of cells
2. Blastopore extends around embryo as more surface cells invaginate.
   - - When the ends meet, blastopore forms a circle that shrinks as ectoderm spreads downward. Continued involution expands endoderm and mesoderm inward as archenteron forms.
3. Circular blastopore (fated to become anus) surrounds a yolk-plug (remaining patch of endodermal cells on the vegetal side, created during the formation of the dorsal lip)
   - - Cells remaining on surface are ectoderm, endoderm is innermost, mesoderm is intermediate.

Question 55

Organogenesis and neurulation in frog embryos (4)

+ different structures formed

Answer 55

1. Cells from 2 or 3 germ layers interact in organ formation via induction (molecular signals that make receiving cells differentiate into a specific cell type)
2. Mesodermal notochord induces ectodermal cells thicken and flatten to form a neural plate
   Notochord: flexible, gelatinous rod that acted as a rudimentary spinal cord for muscle contraction / movement BUT had an inability to telescope
3. As neural plate sinks, will roll into neural tube, forming the basis of the central nervous system
4. Neural crest (vertebrates only) break lost from neural folds and ultimately migrate throughout the embryo to differentiate into different structures:
   a. ganglia of PNS
   b. hormone producing cells in the medulla
   c. schwann cells in the CNS
   d. most of the cartilage and bone of lower jaw
   e. odontoblasts (embryonic / immature cells that create teeth)
   f. pigment cells
   g. connective tissue and smooth muscle of heart → ultimately derived from ectoderm

Question 56

Cell migration from mesodermal somites (3)

+ notochord, redefined

Answer 56

1. Strips of mesoderm lateral to notochord separate into blocks (aka somites)
2. Mesenchyme cells dissociate from somites and migrate to form vertebrae, rib cage, parts of occipital plate of skull, skeletal muscles, cartilage, tendons, and skin of back
3. Somites reveal segmented nature of vertebrates –> the more you have, the older the organism

Notochord: flexible, gelatinous rod that acted as a rudimentary spinal cord for muscle contraction / movement BUT had an inability to telescope

Question 57

Gastrulation in the chick (5)

Answer 57

1. Due to extensive yolk deposits in eggs of reptiles, birds, and monotremes, DISCOIDAL CLEAVAGE is restricted to a cap of dividing cells at an animal pole
2. Flattened blastula is two layered: upper EPIBLAST (future embryo) and lower HYPOBLAST (future yolk sac and stalk that connects yolk to embryo), with a blastocoel in between
3. Primitive streak is functionally equivalent to blastopore; will be grey in color
4. Surface cells of epiblast migrate towards primitive streak and involute inside, forming endoderm (displaces hypoblast) and mesoderm
5. Cells remaining on surface become ectoderm

Question 58

25 to 38 hour embryos (6)

Answer 58

1. At anterior end of primitive streak is a concentration of cells known as Hensen’s node
2. Cells entering the node migrate anteriorly and contribute to the developing brain
3. As development continues, primitive streak with Hensen’s node regresses posteriorly
4. Anterior to the Hensen’s node, notochord forms repeating blocks of mesoderm (somites), which reveal the segmented nature of vertebrates
5. Mesenchyme cells dissociate from somites and migrate to form vertebrae, rib cage, parts of occipital plate of skull, skeletal muscles, cartilage, tendons, and skin of back
6. Posterior to the somites, the broad neural plate occurs, followed by the Hensen’s node and the remains of the primitive streak

Question 59

Spermatogenesis + N/C

Answer 59

creation of sperms

2n, 2c (mitosis yields spermatogonia B )
> 2n, 4c (mitosis yields primary spermatocytes)
> > 1n, 2c (meiosis 1 yields secondary spermatocytes)
> > > 1n, 1c (meiosis 2 yields spermatids)

Spermatogonia stem cells divide mitotically into two daughter cells A and B

• • A remains at basal lamina surface as stem cell
• • B cell (spermatogonia 2n, 2c) replicates becoming primary spermatocytes (2n, 4c)

Cytoplasmic bridges between spermatocytes enables molecular exchange and synchronization
– In humans, the X chromosome is one of the most genetically rich ones. Uniquely X chromosomes (versus Y chromosomes), therefore have lots of X linked diseases expressed in males (ie color blindness, muscle dystrophy)

Sertoli cells (sustentocytes) seal around developing sperm cells (blood testis barrier; sealed with tight junctions); provide nutrients, secrete androgen / binding proteins / inhibin
-- Inhibin: enzyme that travels to brain that stop testosterone production; allows for controlled production of testosterone

Question 60

Oogenesis (6) + N/C

Answer 60

creation of ovum

2n, 2c (Oogonium goes through mitosis)
> 2n, 4c [DNA replication then goes through meiosis 1 (stalled at prophase 1), yields primary oocyte]
> > 1n, 2c [meiosis 1 (completion), yields secondary oocyte]
> > > 1n, 1c [ovulation and fertilization yields fertilized egg ; meiosis 2 completed]

1. Each oogonium becomes surrounded by a single layer of squamous cells (now a PRIMORDIAL FOLLICLE) → oogonium replicates DNA and enters into meiosis 1, where it stalls at prophase 1 (now a PRIMARY OOCYTE) – occurs before you’re born
2. About a year before its possible ovulation, surrounding squamous cells become cuboidal (now a PRIMARY FOLLICLE) and oocyte enlarges
3. At beginning of ovarian cycle, 14 to 20 primary follicles begin developing due to FSH. Follicle cells become stratified (now a SECONDARY FOLLICLE); these cells convert androgens into estradiol and provide it and nutrients to growing oocyte
4. By day 9, only one secondary follicle (usually) remains
5. LH surge on day 14 triggers primary oocyte to complete meiosis 1 (stalls at meiosis 2) becoming a secondary oocyte, soon followed by ovulation
6. Meiosis 2 completed only at fertilization

Question 61

Follicular phase (5)
+ ovulation
+ luteal phase

Answer 61

1. Cohort of primary follicles (each with primary oocyte stalled at prophase 1) begin to grow stimulated by FSH.
2. When >1 layer of follicle cells (granulosa cells), now called secondary follicle
3. Mid-phase, one dominant secondary follicle survives dip in [FSH]
4. Connective tissue layer forms around follicle (theca = source of androgens in response to LH); also, glycoprotein-rich layter, zona pellucida, forms around primary oocyte
5. Graafian (mature) follicle forms, and primary oocyte completes meiosis 1 (now a secondary oocyte)

Ovulation: LH surge triggers expulsion of secondary oocyte from ovary

Luteal Phase: ruptured follicle secretes progesterone (steroid hormone that stimulates uterus in preparation for pregnancy)

Question 62

Sea Urchin Lab (2)

Answer 62

Trypsin inhibitor: soybean derivative; will result in partial or abnormal fertilization envelopes surrounding the sea urchin eggs

Calcium ionophore: A23187; will bind to calcium ions and transport them across the cell membrane, causing an artificial influx of calcium → kickstarts formation of envelope membrane (remember the pathway?)

Question 63

Structures to know about Testes (5)

Answer 63

Seminiferous: location of sperm production

Spermatogenic cells: production of mature sperm cells; outer cells are stem cells (least developed) and will mature as they are pushed into the lumen

Spermatids (mature): immature male sex cell that lacks a flagellum → once added, will be called spermatozoa

Leydig cells: aka interstitial cells; small clumps of cells lying between seminiferous tubules; produce testosterone

Sertoli cells: aka sustentocytes; nourish sperm development by producing antigen binding protein for testosterone; provide fluid for sperm to migrate to epididymis; also provide testes blood barrier (keeps toxins out; nice environment)

Question 64

Structures to know about Ovaries (7)

Answer 64

Primary follicle: jacket of cells within which is a developing egg; as it develops, it secretes nutrients to the ovum; also secretes estrogen

Growing follicle: diff sizes within diff stages of oogenesis

Mature follicles: large follicles that bulge from the surface; contains large fluid filled area called “antrum”

Zona pellucida: thick transparent membrane surrounding a mammalian ovum before implantation

Ovum: mature egg

Corpus luteum: large mass of cells formed from the follicle after ovulation that secretes estrogen and progesterone

Granulosa cells: aka zona radiata that surround the ovum; line the antrum and secrete estrogen