Biology 3700: Exam 2 Study Set- Dr. Nicholas Blay

Structure of a muscle fiber

1. Myofilaments -Thick-Myosin -Thin- Actin 2. Myofibril (cluster of myofilaments) - Endomysium wraps fiber Bundled into: 3. Muscle Fascicles - Perimysium wraps up a bunch of fibers 4. Muscle -Epimysium wraps up perimysium

Phase 1 of Muscle Excitation

1. Nerve Signal arrives at axon terminal -opens voltage gated calcium channels - Ca2+ enters terminal 2a. Synaptic vesicles docked on membrane- 3 snare proteins 3a. Synaptotagmin -Vesicle Receptor protein that senses calcium 4a. Ca2+ complex interacts with SNARE- vesicle fuses and forms a pore to release acetylcholine(ACh).

Control of the Posterior Pituitary Gland

1. Neuroendocrine relfexes 1a. Release of hormones in response to nerve signals 2. ADH 2a. Dehydration- increases osmolarity of blood - Triggers hypothalamic neurons (osmoreceptors) -ADH release- water conservation 2b. High BP- triggers baroreceptors -Inhibiting release-increases urine output- lowers BP 3. Oxytocin 3a. Suckling

Cardiac Muscle

1. Only in heart 2. Involuntary control (auto-rhythmic) 3. Short branched cells 4. Striated 4a. Intercalated discs- cells attach 4b. Desmosomes- make a really strong connection. Prevent mechanical pulling 4c. Gap Junctions- electrical synapses -single functional unit 5. Not reliant on nervous system

Blood Flow in the Heart (O2 Poor)

1. Oxygen Poor blood enters heart through S/I vena cava 2. Flows into Right atrium 3. Flows through Right AV valve 4. Into Right ventricle 5. Through Pulmonary Valve 6. Into Pulmonary Trunk 7. Through pulmonary arteries 8. To lungs for gas exchange

Posterior Pituitary Hormones

1. Oxytocin (OT): 1a. Stimulates uterine smooth muscle- contractions -Contractions during labor and delivery -Induction- Pitocin (synthetic) -Contractions within mammary glands -Causes milk to flow 1b. Increase during sexual arousal -Sperm Transport 1c. Emotional Bonding (partners; parent-offspring) 2. Antidiuretic Hormone (ADH): 2a. Regulates fluid balance -Stimulates kidneys to retain H2O and reduce urine output -Contraction of blood vessels (increase BP)

control of posterior pituitary (cont.)

1. Positive feedback control 2. EX. Chain of signals in oxytocin release 2a. Oxytocin stimulating labor contractions 2b. Stretch receptors in uterus -Signal back to hypothalamus- send more oxytocin!! 2c. Hypothalamus commands posterior pituitary -Releases more oxytocin 2d. Cycle broken at birth

Mineralocorticoids

1. Primary : Aldosterone - "Salt-retaining Hormone" 2. Zona Glomerulosa (only) 3. Responds to falling BP 3a. Renin-angiotensin-aldosterone (RAA) system -Baroreceptors detect falling blood pressure -activate sympathetic reflex -Renin splits Angiotensinogen to angiotensin 1 -ACE enzymes clean angiotensin 1 -Produces angiotensin 2 -Aldosterone secreted from adrenal cortex -Targets kidney cells -Retention/reabsorption of Na+ in DCT

Glucocorticoids

1. Primary: Cortisol(hydrocortisone) 2. Zona fasciculata and zona reticularis 3. Secreted in response to 3a. Corticotropin- releasing hormone(CRH)(Hypothalamus) 3b. Adrenocorticotropic Hormone(ACTH)(Anterior Pituitary) 3c. Cortisol from adrenal cortex -Increases blood glucose and other fuels -Stress/hypoglycemia (fats, amino acids -> glucose) -Increase in fatty acid concentration 4. Adapt to stress and repair damaged tissues 4a. Anti-inflammatory properties (hydrocortisone cream)

Ligand-Gated Ion Channels

1. Receptor also ion channel 1a. Ligand binds -> conformational change in protein (receptor)-> Ion channel opens. 1b. Diffusion across membrane- change in membrane potential.

Hypothalamus

1. Regulates "fundamental functions" 1a. Water balance and thermoregulation 1b. Libido and childbirth 1c. Hunger 1d. Circadian rhythm 2. Functions through the pituitary gland

Hypothalamus and Pituitary Gland

1. Regulates more functions than any other gland 1a. Size of a kidney bean 2. Function of other endocrine glands dependent on signal from hypothalamus/ pituitary. 3. Important link in neural and hormonal regulation

Hypothalalmus-pituitary gland relationships (Ex. Hypothalamo-pituitary-thyroid axis)

1. Relationship between the hypothalamus, anterior. pituitary, and the target tissue is call an axis 2. Hypothalamus secretes releasing hormone 2a. Secretes thyrotopin-releasing hormone (TRH) 3. Induces anterior pituitary to secrete appropriate hormone 3a. TSH secreted 4. Anterior pituitary hormone targets another endocrine gland elsewhere 4a. Thyroid gland 5. Endocrine gland issues response( own hormone secretion or metabolic process) 5a. Releases thyroid hormone (TH) -Metabolic response

Cardiac Regulation

1. Rhythm and contraction- modified by ANS (Medulla oblongata). 1a. Cardioacceleratory- sympathetic via cardiac nerves 1b. Cardioinhibitory- parasympathetic via vagus nerve 2. Intrinsic firing rate of 100 BPM 2a. Vagal tone- holds down the heart rate to 70 to 80 BPM at rest -Steady background firing rate 3. Receives input from several sources. 3a. Cerebral cortex, hypothalamus, limbic system, sensory inputs. -Emotions affect autonomic functions -Other autonomic responses originate in brainstem.

Pacemaker Physiology

1. SA Node Cells- no stable RMP (not waiting for stimuli) 1a. Starts at approx. -60mV and drifts upward due to slow Na+ inflow -No compensatory K+ outflow -Pacemaker potential- gradual depolarization of the SA node. 1b. Threshold: -40mV; voltage-gated fast calcium channels open. -Faster depolarization occurs peaking at 0mV- calcium channels close. 1c. K+ channels open; K+ leaves the cell -Causes repolarization -K+ channels close, pacemaker potential starts over 2. When SA node fires it sets off heartbeat 2a. Internal Pacemaker: fires approximately every .8s -Resting rate approximately 75 BPM

Impulse Conduction to Myocardium

1. SA node stimulates atria to contract simultaneously 1a. Reaches AC node in 50 ms 2. Signal slows down through AV node 2a. Thin cardiomyocytes w/ fewer gap junctions 2b. Delays signal 100 ms- allows ventricles time to fill

Skeletal Muscle Fiber: Structure

1. Sarcolemma: -Plasma membrane of muscle fiber 2. Sarcoplasm- Cytoplasm of muscle fiber 3. Myofibril- Thick bundles of contractile proteins -Myofilaments, actin and myosin 4.Packed Between myofibrils: 4a. Mitochondria, Smooth ER(sarcoplasmic) 4b. Glycogen 4c. Myoglobin- oxygen storing pigment - Both used to produce ATP during activity 5. Transverse (T) Tubules: 5a. Infoldings of sarcolemma 5b. Penetrate Muscle Fiber 5c. Carry electrical current from surface to interior deep inside muscle. 6. Sarcoplasmic Reticulum (SR): 6a. ER of muscle fiber 6b. Forms web around myofibrils 7. Terminal Cisternae: 7a. Dilated sacs around T-tubules 8. Triad: 8a. T-tubule + two terminal cisterns Contraction requires Ca2+, SR releases that into cytosol. calcium stored in SR

Contractile Proteins

1. Shorten Muscle Fiber 1a. Myofilaments- myosin an actin 1b. Occur in nearly all cells 1c. Abundant in skeletal and cardiac msucle 1d. Organization accounts for striations in fiber

Signal Transduction

1. Signal Transduction Pathways: Sequences of events that link receptor activation to cellular responses. 1a. Signal -> receptor activation 1b. Transduction- process for transforming stimulus to response 2. Receptors: Required to receive signal= physiological response 2a. Messenger (ligand) binds to specific target-cell proteins (receptors) -Conformational change -> activation -Responses to Stimuli Include: 1. Permeability, transport properties, or electrical states of the plasma membrane. 2. Metabolism 3. Secretory activity 4. Rate of proliferation and differentiation (proteins) 5. Contractile (other activities)

Impulse Conduction Continued

1. Signals travel very quickly though AV bundle, bundle branches, and subendocardial conducting network 1a. Ventricular myocardium contracts -Very high density of gap junctions 2. Ventricular systole- starts at apex 2a. Myocardium twists ventricles slightly - Like wringing out a towel

Cardiac Conduction System Steps (Detailed)

1. Sinoatrial Node- Upper Posterior wall of Right atrium 1a. Pacemaker -No external stimulation 1b. Depolarizes about every .8 seconds at rest -About 75 BPM -Special nodal cells (non-contractile myocardiocytes) 1c. Set off heartbeat and determines heart-rate 2. Internodal Conduction 2a. Spread of signals from SA node -Through contractile cardiomyocytes 2b. Across both atria -Results in atrial contraction before ventricular 3. Atrioventricular(AV) Node 3a. Similar to SA node 3b. Interatrial septum above tricuspid valve 3c. "Gateway" for electrical signals headed to ventricles -Fibrous skeleton blocks all other paths 3d. Delays signal -Allows ventricles time to fill -Thin cardiomyocytes w/ gap junctions 4. Atrioventricular (AV) Bundle 4a. Modified cells leaving AV node - -> Interventricular septum -LOTS of gap junctions -Moves signal up to 4 m/s 4b. Forks into right and left bundle branches -Descends towards apex 5. Subendocardial Conducting Network 5a. Turn upward at heart apex 5b. Branch throughout ventricular myocardium 5c. Conduct action potentials rapidly (Gap junctions) -Ventricles contract in near unison.

Striations

1.Precise organization of actin and myosin 2. Dark A bands alternating with Light I bands 2b. A bands: -Thick and thin filaments overlap - Width remains same in sliding theory 2c. I bands: -Only thin filaments -Narrow when thin filaments slide -bisected by thin dark line- Z line (disc) -Protein provides anchorage for thin/elastic filaments 3. Z-disc makes boundary for the sarcomere (contractile unit) -Move closer with sliding filament theory 4. H-Bands in middle that disappear when contraction occurs. 5. M-Line is the center line that runs through the striation LENGTHS OF FILAMENTS DON'T CHANGE WHETHER MUSCLE IS CONTRACTED OR RELAXED. -Only relative position

Phase 4: Muscle Relaxation

14. Nerve signal ceases= no more ACh 15. ACh already in synapse -released from receptors -Broken down by acetylcholinesterase -Cessation of muscle fiber stimulation 16. Calcium release closes -No more Ca2+ released 17. Ca2+ actively pumped out of cytoplasm and reabsorbed - Ca2+ ATPase pumps require ATP 18. Troponin-tropomyosin complex- Ca2+ Disassociates -Returns to resting position - Blocks myosin from binding to actin RELAXATION OF MUSCLE

Phase 1 Cont.

5. Adjacent sarcolemma has voltage gated ion channels -Opens channels in response to EPP - Separate Na+ and K+ channels -Initiates wave of voltage changes (action potential) -Spreads in all directions away from neuromuscular junction(NMJ) MUSCLE IS NOW EXCITED

Phase 2 Cont.

8. Ca2+ binds to troponin on thin filament 9. Ca2+ binding changes shape of troponin-tropomyosin complex. - Reveals active sites on actin

Anterior Pituitary Hormones (Cont.)

3. Thyroid Stimulating Hormone (TSH) 3a. Thyroid gland- secrete thyroid hormone -Metabolism regulation, body temperature 4. Adrenocorticotropic Hormone (ACTH) 4a. Stimulates adrenal cortex -Secrete Glucocorticoid hormones (ex. Cortisol) -Regulates: glucose, fat, and protein metabolism, (stress response) 5. Prolactin (PRL) 5a. Stimulates mammary glands to synthesize milk (after birth) -secreting cells increased during pregnancy 6. Growth Hormone (GH;Somatropin) >1000x any other hormone - Promotes Tissue Growth -Mobilizes energy from fat -Raises levels of electrolytes -Stimulates protein synthesis, mitosis, and cellular differentiation. -Widespread effects on body -Most conspicuous during childhood and adolescence -Muscle and bone growth directly

Terminal Cisternae

Dilated sacs around T-tubules that real Ca2+ into cytosol(sarcoplasm)

Hypothalamic Nuclei to be Familiar With

1. Acruate Nucleus: Regulates appetite: secretes releasing hormones that regulate anterior pituitary. 2. Paraventricular Nucleus: Produces oxytocin (involved in childbirth, lactation, orgasm); controls posterior pituitary 3. Supraoptic Nucleus: Produces antidiuretic hormone (involved in water balance); controls posterior pituitary

(Adrenal) Androgens

1. Androgens 1a. Most secreted by testes -Adrenal androgens negligible in males 1b. Important for female physiology -Adrenal cortex primary source in females 2. Estradiol 2a. Adrenal estrogen 2b. Negligible in females- most estrogen produced by ovaries. -No longer functional after menopause 3. Both important in skeletal growth and bone mass

Adrenal (suprarenal) Glands

1. Atop kidneys 2. Relatively large in infant 2a. Shrink by 50% by age 2 3. Fusion of fetal tissues 3a. Different origins/functions 3b. 2 Parts: - Inner: Medulla (10-20%) - Outer: Cortex (80-90%) Think of as a type of "hat" on top of kidneys

Cardiac Conduction System

1. Autorythmic 1a. Beats without stimuli from nervous system 1b. Modified Cardiomyocytes - Do not contract but regularly depolarize - Concentrated in sinoatrial and atrioventricular nodes (nodal cells) 2. Electrical signals -> stimulate contractile cardiomyocytes = heartbeat Steps: 1. SA node fires 2. Excitation spreads through atrial myocardium 3. AV node fires 4. Excitation spreads down AV bundle and though the branches 5. Subendocardial conducting network distributes signal through ventricular myocardium.

Signaling Between Cells

1. Constantly sending and receiving chemical signals 1a. Development- determine what a cell becomes 1b. Later- help coordinate growth and daily functions 2. Cell-signaling pathway (in a nutshell): 2a. Chemical signal binds to receptor on target plasma membrane 2b. Initiates signal transduction pathway -Series of reactions set off by signal 2c. End product affects functionality of cell

Adrenal Medulla

1. Core of adrenal gland 2. Dual roles- endocrine gland/ganglion of sympathetic nervous system. 2a. Fibers penetrate cortex -> reach chromaffin cells -Functionally- sympathetic postganglionic neurons -No dendrites/axon release products into blood -Neuroendocrine cells

Regulatory Proteins

1. Determine when fiber can (and cannot) contract 1a. Tropomyosin and troponin

Hypothalamic Hormones

1. Eight Hormones produced in hypothalamus 1a. Six regulate anterior pituitary -Releasing Hormones -Stimulate anterior pituitary to secrete hormones -E.g., thyrotropin-releasing hormone -Stimulates pituitary to secrete thyroid-stimulating hormone -Inhibiting Hormones -Suppress pituitary output -E.g. prolactin-inhibiting hormone -Suppresses prolactin secretion when not pregnant 1b. Two in Posterior Pituitary: oxytocin, antidiuretic hormone (ADH)

Hormone Secretion (By Anterior Pituitary)

Hormone secretion by the anterior pituitary gland is controlled by hypothalamic (hypophysiotropic) hormones released by hypothalamic neurons

Excitation

Process in which nerve action potentials lead to muscle action potentials

Myofibrils

Thick Bundles of intratactile poteinsm, Myofilaents- actin and myosin

Neuromuscular Junction

This is where the nerve meets the muscle fiber

Transverse (T) Tubules

Transmit action potential through cell Allow entire muscle fiber to contract simultaneously. Brings electrical signal deep inside muscle fiber.

Regulatory Proteins

Tropomyosin and Troponin

Signaling

Types of Signaling: 1. Gap Junctions: adjacent cells pass ions/molecules through channels. 2. Paracrine Signaling: Cells within organ secrete molecules that diffuse across the extracellular space to nearby target cells (Local Signaling). 2a. Autocrine- cell receptors for molecule it secretes 3. Synaptic Signaling: Neurons secrete neurotransmitters across synapse. 4. Endocrine Signaling: Glands secrete hormones into the bloodstream.

Contractile Proteins (Myofilaments)

myosin and actin

excitation-contraction coupling

events that link the action potentials on the sarcolemma to activation of the myofilaments, thereby preparing them to contract

Phase 2 Start: Excitation- Contraction Coupling

- Events that link APs on sarcolemma to activation of myofilaments are the coupling sites 6. Ap spreads over sarcolemma -Passes through T-Tubules into cell interior -This stimulates voltage gated DHP 7. Opens voltage gated Ca2+ channels in terminal cisterns (calcium release channels) (ryanodine receptors) -Mechanically linked to DHP receptors= conformational change -Ca2+ down concentration gradient into sarcoplasm -Stimulates release of more Ca2+ through calcium release channels.

Phase 3 Muscle Contraction

- Mechanism of contraction: sliding filament theory 10. ATP binds to myosin heads -Myosin ATPase splits ,hydrolyzes, ATP into ADP and phosphate (energy released) which causes head to cock 11. Myosin head binds to thin filament -Link between myosin head and actin is called a cross bridge. 12. Myosin releases Phosphate (Conformational change) -Flexes into original position -Tugs thin filament-power stroke ADP is released

Adrenal Cortex

1. 25+ steroid hormones (corticosteroids/corticoids) 1a. Critical to survival 1b. Specialized lipids synthesized from cholesterol 2. 5 secreted in physiologically significant amounts Three categories: 1. Mineralocorticoids- Regulate electrolyte balance 2. Glucocorticoids- Regulate metabolism (glucose), development, and have anti-inflammatory properties 3. Adrenal androgens (sex steroids)- developmental and reproductive functions.

Muscle excitation first step

1. Electrical nerve signal leads to an electrical signal and action potential in the muscle fiber 2. At rest, muscle fiber is polarized with sodium and potassium pumps.

Adrenal Medulla Part 2

1. Fear, pain, stress! 2. Epinephrine (adrenaline)(75-80%), norepinephrine (noradrenaline)(20%), trace of dopamine 2a. Adrenergic Receptors: G-protein mechanisms 2b. Increase alertness, prepare for physical activity, mobilize fuel. -Gylcogenolysis -Liver glycogen -> glucose -> blood -Muscle glycogen -> glucose -> remains in muscles -Breakdown of adipose tissue -> fatty acids -> blood 2c. Glucose-sparing; inhibits secretion of insulin -Fatty acids -> energy for muscles -Blood glucose -> brain 3. Reduces activity of "non-essential"(digestive/urinary) 4. Increases heart-rate, blood pressure, metabolic rate, respiratory rate. 4a. Increase alertness- preparation for physical activity

Blood Flow in the Heart (O2 Rich)

1. From Pulmonary Veins 2. Into Left Atrium 3. Through Left AV valve 4. Into left ventricle 5. Through Aortic Valve 6. Into Aorta 7. To Body

Anterior Pituitary

1. Hypothalamus -> anterior pituitary gland 1a. Network of small blood vessels 2. Hypophyseal Portal System: 2a. Blood flows from one capillary bed to another (rare) -Hypothalamus-> chemical signals(hormones) into primary capillaries. -Travel short distance (portal venules) to anterior pituitary -Leave bloodstream through secondary capillary network -Stimulate of inhibit anterior pituitary 3. Hypothalamic hormones regulate anterior pituitary cells 3a. Hypothalamic- releasing and inhibiting hormone

Posterior Pituitary

1. Hypothalamus -> posterior pituitary 1a. Controlled by hypothalamic tissue 1b. Neurosomas produce hormones- origin sites -2 small peptide hormones 1c. Nerve cell axons -> infundibulum -> posterior lobe -Hypothalamo-hypophysed tract - Hormones stored in posterior pituitary -Electrical signals stimulate release NERVE TISSUE (NOT A TRUE GLAND)

Anterior Pituitary Control

1. Hypothalamus doesn't make decision without input 2. Negative feedback inhibition 3. Ex. Chain of signals in thyroid hormone: 3a. Hypothalamus secretes thyrotropin releasing hormone to stimulate anterior pituitary 3b. Anterior pituitary secretes Thyroid-stimulating hormone to stimulate thyroid. 3c. Thyroid responds by secreting thyroid hormone 3d. Thyroid Hormone -Feeds back to both hypothalamus and anterior pituitary -Reduces TRH and TSH output -Keeps FH secretion in check

Pituitary (Hypophysis)

1. Infundibulum: Stalk- suspends pituitary from hypothalamus 2. Functionally and embryologically two structures: 2a. Anterior Pituitary: -3/4s of pituitary -origin- pound of roof in embryonic pharynx (throat) 2b. Posterior Pituitary: -Down-growth from brain (hypothalamus) -Retains connection to brain

Intercalated Discs

1. Interdigitating folds: increase surface area of contact 2. Mechanical Junctions- tightly join cardiomyocytes 2a. Fascia Adherens- transmembrane proteins anchor each cell to next 2b. Desmosomes- prevent contracting cardiomyocytes from being pulled apart 3. Electrical Junction (Gap Junction) allow ion flow between cells; can stimulate neighbors 3a. Myocardium of either two atria or two ventricles act like single, unified cell

Functions of Mammalian Heart

1. Keeps O2 poor blood separate from O2 rich blood 2. Keeps the blood flowing in one direction 3. Creates blood pressure 4. Regulate the blood supply 5. Serve as an endocrine gland 5a. Natriuretic peptide hormones- increase urine output 5b. Na+ excretion for lower BP -Counters angiotensin 2 (kidneys)

Generating an Action Potential

1. Long depolarization period 200ms (compared to 2ms in skeletal muscle). 2. Long refractory period of approximately 250ms (compared to 1-2 ms in skeletal muscle). This all allows time for the blood to enter and or leave chambers within the heart.

Growth Hormone

1. Most pituitary hormones influence specific endocrine glands elsewhere 2. Growth Hormone- Widespread effects 2a. Bone growth, thickening, and remodeling -Especially during childhood and adolescence 2b. Ghrelin- released by empty stomach -Informs body of hunger -Stimulates release of GHRH -> spike in GH -Ready to utilize incoming nutrients 3. GH levels decline gradually with age 3a. Average 6 ng/ml during adolescence, 1.5 ng/ml in old age -Lack of protein synthesis contributes to aging of tissues and wrinkling of the skin.

Cardiac Muscle: Cardiomyocytes

1. Muscle cells of the heart 2. Striated, short 3. Central nuclei within each cell 4. Ends slightly branched 4a. Connect w/ other cardiomyocytes 4b. Synchronized unit 5. Gap Junctions 5a. Ion flow from cell to cell easily 6. Intercalated Discs

Dystrophin

1.Links thin filaments to proteins of sarcolemma 2. Transfers forces of muscle contraction to CT- ultimately leads to tendon 3. Muscular Dystrophy: genetic defects in dystrophin -Hinders force being transmitted to tendon

Generating an Action Potential in the Contractile Cardiomyocytes (STEPS)

1. Stimulus from SA node (or adjacent cell): voltage gated Na+ channels open 2. Na+ inflow depolarizes the membrane and triggers the opening of more Na+ channels. 2a. Creates a positive feedback cycle and a rapidly rising membrane voltage. 3. Na+ channels close when the voltage peaks at approx. +30mV. 3a. Action potential spreads across membrane 4. Calcium enters through slow voltage gated calcium channels. 4a. Prolongs depolarization of membrane- creates plateau - 2ms in skeletal; 200-250ms in cardiac 4b. Binds to ligand gated calcium channels on SR - Calcium-stiumlated (induced) calcium release channels 4c. Release stored calcium- binds to troponin - =contraction 4d. Plateau falls slightly because some potassium leakage; most potassium channels remain closed until end of plateau. 5. Calcium channels close; calcium is actively transported out of cell into SR. 5a. K+ channels open and rapid K+ outflow returns membrane to its RMP

Cardiac Regulation Cont.

1. Sympathetic nerves increase contraction strength (and heart rate) 2. Fibers terminate in SA/AC and atrial and ventricular myocardium. 2a. Post ganglionic cardiac nerve fibers are andrenergic- release NE. 2b. Bind to adrenergic receptors on the heart -Activate cAMP second-messenger system in cardiomyocytes and nodal cells. 2c. -> Enzyme activation that increases calcium channels in PM. 2d. Calcium inflow accelerates depolarization of SA node and contraction of cardiomyocytes. 2r. Activates mechanisms that also increase calcium uptake in the SR. -Cells can relax quicker 3. Increase heart rate

Anterior Pituitary Hormones

1. Synthesizes Six Peptide Hormones 2. Two Hormones that target gonads (gonadotropins) 2a. Follicle-Stimulating Hormone(FSH) - Stimulates Maturation of follicles containing eggs -stimulates secretion of estrogen -Regulates ovarian/menstrual cycles -Stimulates production of sperm 2b. Leutenizing Hormone (LH) -Stimulates Ovulation -Release of egg from follicle -After Ovulation- follicle becomes corpus lutem -Secretes progesterone - Maintains lining of uterus if pregnancy occurs -Testes to secrete testosterone

Types of Receptors

1. Target cell receives a signal- specific receptor protein on plasma membrane or inside cell. 2. Plasma Membrane Receptors (polar/water soluble) 2a. Transmembrane Proteins -Chemical Messengers bind to extracellular regions -Intracellular regions proceed with signal transductions 2b. Transduce signals without directly interacting with DNA - Ex. Epinephrine, acetylcholine, and insulin 3. Intracellular Receptors (non-polar/lipid soluble) 3a. Cytosol or nucleus -Messengers bind to regulatory proteins on sites on DNA 3b. Transduce signals through interaction with genes -Ex. Steroid hormones, thyroids hormone, etc

Myofilaments

1. Thick filaments: 1a. Several hundred myosin (protein) molecules 1b. 2 chains: Shaft-like tail and double globular head (golf club). 1c. Heads directed outward in a helical array around bundle -Heads on one half of the thick filament angle to the left -Heads on other half angle to the right -Bare zone with no heads in the middle 2. Thin Filaments: Fibrous (F) actin 2a. Two intertwined strands of globular (g) actin -Beaded necklace - Active site-binds myosin 2b. Tropomyosin- shorter regulatory protein (Key) -Blocks (6-7) G-actin subunits 2c. Troponin- attached to tropomyosin (Lock) - Binds Ca2+ to allow binding to occur

Adrenal Cortex Part 2

1. Three Tissue Levels: 1. Zona Glomerulosa -Thin outmost layer -Cells arranged in rounded clusters -Mineralocorticoids 2. Zona Fasciculata -Middle and thickest layer -Cells arranged in parallel cords (fascicles) -Glucocorticoids and androgens 3. Zona Reticularis -Innermost layer -Cells in branching network (reticulum) -Glucocorticoids and androgens

Elastic Filaments

1. Titin: Huge, springy protein - Runs through core of thick filament -Anchors myosin to z-disc and m-line -Stabilizes and positions the thick filament -Prevents over-stretching and provides recoil

Hypothalamic Hormones and Posterior Pituitary (KNOW THESE)

1. Two produced in hypothalamus; transported along axons to posterior pituitary 2. Released when hypothalamic neurons are stimulated 2a. Oxytocin (OT) and antidiuretic hormone (ADH) - Both stored and released by posterior pituitary - Posterior pituitary does not synthesize them

(Adrenal) Androgens (also estrogen)

1. Zona reticularis and fasciculata 2. Regulated by ACTH (Adrenocorticotropic Hormone) 3. Primary: Dehydroepiandrosterone (DHEA) 3a. Converted to testosterone/ dihydrotestosterone 3b. Produced in large quantities in male fetus -> role in male reproductive tract development 3c. Stimulates development in both sexes of -Pubic and axillary hair -Apocrine sweat glands -Libido

Phase 1 of Muscle Excitation (Continued)

2. Diffusion of Acetylcholine across synaptic cleft 3. ACh binds to receptors on sarcolemma (motor end plate) 4. Excitement of sarcolemma 4a. Ligand Gated channels open 4b. Na+ rushes in, K+ rushes out 4c. Motor End-plate potential (EPP) up and down voltage fluctuation.

Motor Unit

Nerve fiber and all the muscle fibers innervated

Phase 3 Cont.

Remains Attached Until: 13. ATP binds to myosin head -Actin released, cross bridge broken HEAD NOW READY TO REPEAT WHOLE PROCESS

Contraction

Step in which the muscle fiber develops tension and may shorten

Relaxation

When Stimulation ends, muscle fiber relaxes and returns to its resting length