BIOL 2230 Unit 1 Semester PDF

Lecture Objectives: Endocrine System 1 1. Discuss the differences between neural and endocrine mechanisms of control of body functioning. Nervous System ​ Uses electrochemical impulses sent through neurons throughout the body ​ Only affects the excitable tissue ○​ Skeletal, smooth,...

Lecture Objectives: Endocrine System 1 1. Discuss the differences between neural and endocrine mechanisms of control of body functioning. Nervous System ​ Uses electrochemical impulses sent through neurons throughout the body ​ Only affects the excitable tissue ○​ Skeletal, smooth, and cardiac muscle ○​ Glands ​ Response can happen in milliseconds ​ Adaptation can occur ○​ Nervous system won't respond as intensely to a stimulus after a while Endocrine System ​ Uses chemical messengers (hormones) ○​ Hormones are secreted by glands ​ Affect metabolic activity of the target cell ○​ Any cell with the receptor for that hormone can be affected (target cell) ​ There is a lag time before a response occurs ○​ Slower than the nervous system, but the effect lasts much longer 2. Differentiate exocrine and endocrine glands. Exocrine Glands ​ Secretes substances through ducts ​ Involved in digestive processes ​ Ex: ○​ Sweat, oil, and saliva glands ​ Not hormonal glands, not endocrine secretions Endocrine Glands ​ Ductless ​ Highly vascularized ​ Cell secretes a substance, and it gets into the bloodstream quickly ★​ Some organs have both exocrine and endocrine glands (ex: pancreas) 3. Identify the neuroendocrine link, and discuss its functioning.  ​ The neuroendocrine link is the hypothalamus ○​ It functions to connect the nervous and endocrine systems ○​ 4. List and differentiate the types of chemical messengers. Hormones ​ Long-distance chemical messenger ​ Chemical that is produced in one part of the body, but exerts its effects in another part of the body Autocrines ​ Chemical produced by a cell that changes the activity of that cell ○​ The autocrine changes the structure of the cell which created it, thereby affecting its own function Paracrines ​ Chemical signals secreted by cells that affect neighboring cells ○​ These neighboring cells may be of the same or different tissue ​ Localized effect Pheromones ​ Chemical secretion produced by one individual that affects another individual ​ Predominantly used for mating ○​ Ex: ​ Cat secretes pheremones when in heat to attract mating partners ​ Women produce pheromones in their sweat 5. Identify the cells at which hormones exert their effects, and discuss the generalized effects hormones can produce. ​ Hormones exert their effects on target cells ○​ Target cells are any cells with the receptor for that hormone ​ When a hormone binds to a receptor, it alters the activity of the cell ​ Some hormones can have different effects based on the target cell ○​ A hormone will affect a target cell depending on the receptor of the target cell ​ Called receptor specitivity ​ Most cells have receptors for GH and thyroid hormone Hormonal Effects/Actions ​ Open or close ion channels ○​ Changes the permeability of the cell ○​ Let certain substances in or out ​ Stimulate protein synthesis ○​ Can cause synthesis of different types of proteins ​ Structural protein ​ Ex: ○​ Channel protein ​ Export proteins ​ Released from cell and travel somewhere else ​ Enzymes ​ Used to change cellular activity ​ Activate or deactivate enzymes ○​ Can turn enzymes inside the cell on or off ​ Promote secretion ○​ Hormones can cause an increase in the secretory responses of cells ​ Ex: ​ Increased secretion of mucus and export proteins ​ Stimulate mitosis ○​ Hormones can cause growth and repair 6. Describe the chemical classifications of hormones Amino acid-based (non-steroid hormones) ​ Most hormones are amino acid-based ​ Also called peptide hormones, protein hormones, non-steroid hormones, or proteinaceous hormones ​ These hormones are water soluble ○​ These hormones dissolve in water and travel easily in plasma (liquid portion of the blood) ​ Target cells for these hormones have receptors on the plasma membranes ○​ Extracellular receptors Steroids ​ These hormones are derived from cholesterol ​ They are fat soluble hormones ○​ Can pass through a cell's plasma membrane  ​ Steroids go into many cells but will exit cell through plasma membrane if there is no receptor ​ Steroids bind to carrier molecules to move through the bloodstream ​ Receptors for steroids are inside the cell ○​ Intracellular receptors ​ Steroids are only produced in two places: ○​ Gonads ​ Ovaries and testes ○​ Cortex of the adrenal glands -> make adrenocorticosteroids Eicosanoids ​ Not hormones ○​ Not really a hormone because they have localized effects instead of long distance effects ​ Biologically active lipids ​ Paracrines ○​ Released by cell to affect neighboring cells, have localized effect ​ Ex: ○​ Prostaglandins and leukotrienes ​ Play a role in the immune system and are inflammatory chemicals 7. Describe the two major mechanisms by which these two classes of hormones bring about their effects. Amino acid based mechanism ​ Receptors for amino acid based hormones are located on the plasma membrane ○​ Extracellular receptors ​ Involves G proteins and secondary messengers ○​ G proteins are peripheral proteins ​ Does not activate the cell directly ○​ Uses G protein and secondary messenger Steroid-based mechanism ​ Receptors inside the cell ○​ Intracellular receptor ○​ Usually inside the nucleus ​ Direct activation ○​ Causes cells to make new proteins 1.​ Hormone diffuses through plasma membrane 2.​ Hormone binds with intracellular receptor  3.​ Activated hormone- receptor complex binds to a receptor protein on DNA ○​ Acts as a promoter to turn the gene on 4.​ Transcription is initiated 5.​ mRNA translated at ribosome outside the nucleus 6.​ Protein produced 8. Discuss the two models of amino acid-based action. Cyclic AMP mechanism 1.​ Hormone binds to membrane receptor 2.​ Modified receptor binds to G protein ○​ Causes G protein to become activated 3.​ Activated G protein activates adenylate cyclase (enzyme) 4.​ Adenylate cyclase creates cAMP from ATP 5.​ cAMP stimulates protein kinase reactions 6.​ Protein kinase phosphorylates proteins ○​ Phosphorylating a protein can activate or deactivate it; depending on what protein it is 7.​ Phosphodiesterase degrades cAMP PIP- Calcium mechanism 1.​ Hormone binds to membrane receptor 2.​ Modified receptor binds with G protein ○​ Causes G protein to become activated 3.​ Activated G protein activates phospholipase (enzyme) 4.​ Phospholipase splits PIP2 into DAG and IP3 5.​ DAG activates protein kinases ○​ Kinases will phosphorylate proteins within a cell 6.​ IP3 triggers release of calcium from the endoplasmic reticulum 7.​ Calcium acts as a secondary messenger either inside or outside the cell 9. Identify the factors that control hormone action. Hormone level in the bloodstream ​ The more hormone produced and released into the blood, the greater effect the hormone will have ​ The concentration of a hormone in the blood is referred to as a titer The number of receptors in/on target cells  ​ More receptors = more activity ​ Up regulation ○​ Stress can cause a target cell to make more receptors, making it easier for the hormone to bind to it ​ Down regulation ○​ As stress continues, the target cell may decrease the number of receptors on itself ○​ The body ignores the stress Receptor Affinity ​ A hormone with high receptor affinity binds more easily to a receptor ​ Greater receptor affinity = greater hormonal activity 10. List three kinds of interaction that different hormones acting on the same target cell can have. Permissiveness ​ The presence of a second hormone causes the first hormone to exert its full effect ○​ Ex: ​ Gonadotropins causes development of reproductive organs ​ Thyroid gland hormones increase the activity of gonadotropins Synergism ​ When multiple hormones have the same effect, the release of the multiple hormones has a greater effect on the body ○​ Ex: ​ Glucagon and epinephrine both cause blood sugar to rise. ​ When glucagon and epinephrine are released simultaneously, blood sugar rises faster than if only one of the hormones was released Antagonism ​ Two hormones work against each other; two hormones have the opposite effect. ○​ Ex: ​ Glucagon and insulin work in opposite ways to affect blood sugar 11. Explain how hormone release is regulated. Humoral  ​ When concentration levels change in the bloodstream, glands may release hormones to restore the concentration levels ○​ Ex: ​ Ion concentration in the bloodstream like sodium ions ​ Concentration of sugar can affect the release of hormones Neural ​ Some glands are stimulated by nervous impulses Hormonal ​ Some endocrine glands are target cells for other hormones ​ When other hormones bind to a gland, the gland will secrete its own hormone ★​ Most glands are inhibited with a negative feedback system 12. List the major endocrine glands, and describe their body locations. 1.​ Pituitary ​ Located underneath the hypothalamus 2.​ Thyroid: ​ Under larynx 3.​ Parathyroid: ​ Located on the posterior side of the thyroid gland 4.​ Adrenals: ​ On top of kidneys 5.​ Pancreas: ​ Near small intestine/behind the stomach 6.​ Gonads: ○​ Ovary/testis are located near the groin 7.​ Pineal: ​ Brain (near epithalamus) 8.​ Thymus: ​ Above heart (behind sternum) 13. Discuss the structure of the neurohypophysis (posterior pituitary gland) and describe the effects of its two hormones. Structure  ​ Neural tissue ​ Does not produce hormones, it only secretes hormones ​ Extension/ outgrowth of the hypothalamus Posterior Pituitary Gland/Neurohypophysis Hormones ​ Both are Amino acid-based hormones and use the PIP-calcium mechanism 1.​ Oxytocin ​ Stimulates smooth muscle contractions in childbirth and milk ejection ​ Linked to sexual arousal and satisfaction ​ Linked to orgasm ​ Tends to produce affectionate behavior in males and females ○​ “cuddle hormone” ​ Promotes nurturing ​ Can act as an amnesiac 2.​ ADH: Antidiuretic Hormone ​ Acts on kidneys to reabsorb water back into the bloodstream instead of releasing the water as urine ​ Regulates water balance by preventing urine formation ​ The osmoregulatory center (in the brain) controls the concentration of the blood. ○​ If blood becomes too concentrated, ADH is released to get more water into the body/bloodstream 14. Discuss the structure of the adenohypophysis (anterior pituitary gland). List the hormones made by the adenohypophysis, and describe the effects of these hormones. Structure ​ Started as an outgrowth of oral cavity (Rathke’s pouch) ​ Only connection between neurohypophysis and adenohypophysis are blood vessels ​ Gland/secretory tissue Anterior pituitary gland/Adenohypophysis Hormones ​ All these hormones are amino acid-based ​ All use the cAMP mechanism 1.​ Growth hormone (GH) ​ Stimulates ○​ Cell growth and division (especially muscle and bone) ○​ Protein synthesis ○​ Fat metabolism ○​ Glucose conservation  ​ Pituitary dwarfism ○​ Lack of production of growth hormone ​ Gigantism ○​ Too much growth hormone ​ Acromegaly ○​ Burst of growth hormone and adult life ○​ Long legs, hands, and feet ​ Production decreases in adult life Direct actions of Growth Hormone 1.​ Increases blood levels of fatty acids ​ Takes fat out of storage to be put in the bloodstream to be used by cells 2.​ Decreases cellular uptake/metabolism of glucose ​ Leaves glucose in the system for the body to use 3.​ Encourages breakdown of glycogen into glucose in the liver ​ Called diabetogenic effect 4.​ Causes liver to create IGFs (insulin-like growth factors) Indirect actions of Growth Hormone 1.​ Growth hormone “operates” through insulin-like growth factors ​ IGFs stimulate uptake of amino acids from blood into cells ​ Stimulate uptake of sulfur into the matrix of cartilage ○​ Increasing the concentration of sulfur into the matrix of cartilage increases the strength of the cartilage 2.​ Thyroid Stimulating Hormone (TSH) ​ Also called thyrotropin ​ Stimulates the development of the thyroid gland ​ Stimulates secretion from the thyroid gland 3.​ Adrenocorticotropic Hormone (ACTH) ​ Stimulates adrenal cortex to release corticosteroid hormones ○​ Especially glucocorticoids ​ ACTH responds to stress by activating the adrenal cortex 4.​ Gonadotropins ​ Regulate functions of gonads ​ Gonadotropins include FSH and LH ○​ FSH ( follicle-stimulating hormone) stimulates gamete production ○​ LH (luteinizing hormone) promotes the production of gonadal hormones ​ Men and women produce both hormones Males and Gonadotropins  ​ FSH: Sperm production ​ LH: Stimulates interstitial cells of the testes to produce testosterone Females and Gonadotropins ​ FSH: Ova production ​ LH: Triggers ovulation and promote synthesis of estrogen and progesterone (ovarian hormone) ​ FSH and LH cause maturation of follicle 5.​ Prolactin ​ Stimulates milk production by breasts ​ May enhance testosterone production in males 6.​ POMC ​ Pro-opiomelanocortin ​ Chemical linked to the activity of the adrenal cortex ​ Linked to the production of endorphins ​ Linked to melanocyte activity ​ This chemical is a pre-hormone and is involved in stress response Lecture Objectives: Endocrine System 2 1. Identify the hormone producing organs, list the or hormones each produces, and discuss the actions of each product (purple=gland, green= hormone, red=hormone action) 1.​ Thyroid gland ​ Two lobes connected by the isthmus ​ Largest pure endocrine gland ​ Located beneath the larynx a.​ Thyroid hormone (Thyroxine, T3/T4) ​ Thyroid hormone is composed of two separate hormones ○​ T3 is thyroglobulin with three iodine atoms bonded to it ○​ T4 has four iodine atoms bonded to it ​ Almost every cell in the body has a receptor for it ○​ Except brain, spleen, testes, uterus, and thyroid gland ​ ​ Thyroxine Actions ​ Increases metabolic rate and heat production ○​ This is known as the calorigenic effect (maintenance of body temperature by cellular activity) ​ Maintain blood pressure by increasing the number of adrenergic receptors  ❖​ Thyroxine is transported in the blood by binding to transport proteins ​ Especially thyroxine binding globulin (TBG) ❖​ Thyroxine acts like a steroid by binding to intracellular receptors, even though it is an amino acid-based hormone ​ TBG can bring thyroxine into the cell ​ Transcription results b.​ Calcitonin ​ Produced by parafollicular cells in the thyroid ○​ Also called C cells ​ Most important during times of rapid skeletal growth and reformation ○​ Most important hormone for regulating blood calcium during infancy and childhood ​ Lowers blood calcium levels ​ ​ Calcitonin Actions ​ Inhibits osteoclast activity ​ Stimulates calcium uptake and deposition 2.​ Parathyroid Gland ​ Embedded in the posterior portion of the thyroid gland ○​ Typically four parathyroid hormones a.​ Parathyroid hormone ​ Most important hormone in controlling calcium balance of blood as an adult ​ ​ Parathyroid Hormone Actions ​ Stimulates osteoclasts to release calcium and phosphate into the blood ​ Enhances reabsorption of calcium by the kidneys ​ Increases absorption of calcium by intestines ○​ Calcium normally doesn't absorb well in the intestines, parathyroid hormone helps it absorb ​ Promotes kidneys to convert vitamin D to its active form, calcitriol (Vitamin D3) ○​ Vitamin D helps with calcium uptake by cells 3.​ Adrenal Gland ​ Paired glands located atop each kidney ​ Each gland is made up of a cortex and a medulla ○​ The cortex is glandular epithelial tissue ○​ The medulla is part of the sympathetic nervous system ​ Modified sympathetic neurons  ​ Adrenal gland hormones counteract stress a.​ Mineralcorticoids ​ Most important is aldosterone ( 95%) ​ Mineralocorticoids function to regulate the concentration of electrolyte of extracellular fluids ○​ Especially sodium and potassium ​ Play a role in controlling membrane potentials, blood pressure, and blood volume levels ​ ​ Mineralcorticoid Actions ​ Stimulate sodium reabsorption ○​ Occurs in the distal parts of kidney tubules ○​ Also occurs from sweat, saliva, and gastric juices b.​ Glucocorticoids ​ Most important is glucocorticoid is cortisol ○​ Released during periods of stress ​ Functions to regulate energy metabolism of most body cells and resist stressors ​ ​ Glucocorticoid Actions ​ Helps to maintain blood sugar levels via gluconeogenesis ​ Gluconeogenesis ○​ Producing carbohydrates from non carbohydrate sources ○​ Occurs in the liver. Converts proteins and fats to sugar/ carbohydrates ○​ Makes more sugar available to the body to create energy ​ Helps maintain blood volume by preventing the uptake of water by cells ​ Assists in vasoconstriction c.​ Gonadocorticoids ​ Most hormones made here are weak androgens ​ DHEA is one of these weak androgens ○​ DHEA is a precursor to testosterone and estrogen ​ Contributes to the onset of puberty ​ Provides sex drive to women d.​ Epinephrine/Norepinephrine ​ ​ Epinephrine Actions ​ Stress promotes the release of epinephrine by stimulating the sympathetic nervous system ○​ Ex: ​ Test in school ​ Cold weather ​ Exercise ​ Imbalance in the body ​ Causes the following physiological changes in the body:  ○​ Blood sugar levels increase ○​ Blood vessels constrict ○​ Heartbeat increases ○​ Blood pressure increases ○​ Blood is diverted to the brain, heart, skeletal muscles, and preganglionic sympathetic nerve endings in the medulla 4.​ Pancreas ​ Located in the abdomen behind the stomach ​ Has both endocrine and exocrine components ○​ Exocrine ​ Pancreatic duct empties into the small intestine ​ Pancreas produces chemicals to aid in digestion ○​ Endocrine ​ Pancreas produces hormones that affect blood sugar levels a.​ Glucagon ​ Functions on liver to release glucose ​ ​ Glucagon Actions ​ Assist in the breakdown of glycogen into glucose ​ Help synthesize glucose from lactic acid and non carbohydrate molecules ​ Helps promote the release of glucose into the bloodstream b.​ Insulin ​ Lowers blood sugar levels ○​ Moves sugar from blood into storage ​ Influences protein and fat metabolism ​ ​ Insulin Actions ​ Enhances membrane transport of glucose into cells ​ Inhibits breakdown of glycogen into glucose ○​ Also inhibits the production of glycogen ​ Inhibits conversion of amino acids or fats into glucose ○​ Stops gluconeogenesis 5.​ Gonads ​ Sex organs ○​ Testes ○​ Ovaries a.​ Testosterone Testosterone Actions ​ Maturation and maintenance of male reproductive organs ​ Responsible for secondary sex characteristics of males ○​ Increase of muscle mass, hair production, oil production, enlarged larynx, deeper voice, production of gametes (sperm production) b.​ Estrogen ​ ​ Estrogen Actions ​ Maturation of female reproductive organs ​ Responsible for secondary sex characteristics of females ○​ Changes of the deposition of fat storage to hips and breasts c.​ Progesterone ​ ​ Progesterone Actions ​ Functions with estrogen to: ○​ Promote breast development ○​ Causes cyclic changes in the uterine lining 6.​ Pineal Gland ​ Extends from the roof of the third ventricle in the diencephalon a.​ Melatonin ​ ​ Melatonin Actions ​ Promotes drowsiness ​ Inhibit sexual maturation ○​ Helps time puberty 7.​ Thymus ​ Located deep to sternum in the thorax ​ Above the heart ​ Active as an embryo, but gets smaller as you age a.​ Thymoproteins b.​ Thymic factor c.​ Thymosins ​ ​ Thymoproteins, Thymic factor, and Thymosins Actions ​ Work together to help and giving us immunity ○​ Promotes the development of T lymphocytes Other Organs and Hormones 1.​ Heart a.​ ANP ​ Shuts off aldosterone, affects blood pressure and blood volume 2.​ Gastrointestinal Tract a.​ Ex: ​ Stomach can send hormone to affect large intestine activity 3.​ Placenta ​ Primary function is to link mother’s blood circulation with the baby’s blood circulation ​ Develops once fertilization occurs a.​ Estrogen b.​ Progesterone c.​ hCG (human chorionic gonadotropin) ​ This is what is detected in a positive pregnancy strip test  4.​ Kidneys a.​ Erythropoietin b.​ ​ Stimulates the production of red blood cells (RBC) 5.​ Skin a.​ Cholecalciferol ​ Inactive form of Vitamin D3 6.​ Adipose Tissue a.​ Leptin ​ Reduces appetite ​ Increases energy expenditure 2. Describe the histological composition of each endocrine gland to illustrate how the hormones are produced. 1.​ Thyroid gland ​ Made of follicles composed of cuboidal epithelium ○​ Produces thyroglobulin ○​ Thyroglobulin is stored in a colloid ​ Also contains parafollicular cells ○​ Called C cells ​ C cells produce calcitonin ​ Calcitonin is not stored ​ It is released into the bloodstream immediately 2.​ Parathyroid Gland ​ Two types of glandular cells ○​ Oxyphil cells ​ Do not know the function of these cells ○​ Chief cells ​ Produce parathyroid hormone (PTH) ​ Parathyroid hormone is the most important hormone in regulating blood calcium as adults 3.​ Adrenal Cortex ​ Zona glomerulosa ○​ Produces mineralocorticoids ​ Zona fasciculata ○​ Produces glucocorticoids ​ Zona reticularis ○​ Produces gonadocorticoids 4.​ Adrenal Medulla ​ Chromaffin cells are modified ganglionic sympathetic neurons ○​ Instead of a neurotransmitter crossing a synapse to another neuron, epinephrine is released into the bloodstream and act as a hormone 5.​ Pancreas  ​ Acinar cells ○​ Exocrine function ​ Pancreatic islets ○​ Called Islets of Langerhans ○​ Embedded in the middle of acinar cells ○​ Contain two types of cells: alpha beta cells ​ Alpha cells ​ Produce glucagon ​ Beta cells ​ Produce insulin 6.​ Pineal Gland ​ Pinealocytes ○​ Produce melatonin 3. Outline the feedback mechanisms that control endocrine gland activity. 1.​ Anterior Pituitary Gland / Adenohypophysis a.​ Growth hormone 1.​ The hypothalamus releases GHRH (growth hormone-releasing hormone) ○​ GHRH goes to somatotrope of the anterior pituitary 2.​ Somatotropic cells of anterior pituitary begin growth hormone synthesis 3.​ Increase in the circulation of growth hormone causes the production of growth hormone inhibiting hormone (GHIH) ○​ GHIH, also called somatostatin, stops GH production b.​ Thyroid Stimulating Hormone 1.​ Hypothalamus releases thyrotropin releasing hormone (TRH) ○​ TRH goes to thyrotropes of anterior pituitary 2.​ Thyrotropic cells of anterior pituitary begin making TSH 3.​ Increased levels of TSH inhibits both the hypothalamus and anterior pituitary ○​ Increased levels of TSH also stimulates production of GHIH 4.​ TSH Peaks before sleep and remains high at night c.​ Adrenocorticotropic hormone (ACTH) 1.​ The hypothalamus secretes CRH (corticotropin-releasing hormone) ○​ CRH goes to corticotropes of the anterior pituitary 2.​ Corticotropes release ACTH ○​ ACTH goes to adrenal cortex to make corticosteroids 3.​ Increase levels of glucocorticoids stop crh 4.​ ACTH secretion stops ★​ Fever, hypoglycemia, and stressors promote CRH released  d.​ Gonadotropins 1.​ At puberty, the hypothalamus secretes GnRH (gonadotropin releasing hormone) ○​ Until puberty, almost no GnRH is produced ○​ GnRH goes to gonadotropes of the anterior pituitary gland 2.​ Gonadotropes in anterior pituitary release gonadotropins (FSH/LH) 3.​ Gonadotropins cause gonadal production/ maturation and gonadal hormone production 4.​ Increase level of gonad hormones suppress FSH and LH secretion e.​ Prolactin (when cycling) 1.​ High estrogen levels stimulates the release of prolactin ○​ Prolactin releasing hormone exists, but is not very important ○​ Estrogen stimulates lactotropes in anterior pituitary to secrete prolactin by inhibiting prolactin inhibiting hormone (PIH) ○​ Males do not produce enough estrogen to shut off PIH 2.​ A decrease in estrogen levels stimulate production of PIH from hypothalamus ○​ Prolactin production is brief due to ovarian hormonal cycling 3.​ Prolactin production stops f.​ Prolactin (when pregnant) ​ High estrogen inhibits PIH, prolactin is released near end of pregnancy ​ Suckling maintains prolactin production after giving birth when estrogen levels decrease ​ Lack of suckling and return of normal hormonal cycles brings about PIH production 2.​ Thyroid gland a.​ Thyroxine/T3/T4/Thyroid Hormone 1.​ The anterior pituitary secretes TSH ○​ TSH goes to the thyroid via blood vessels 2.​ TSH stimulates production of thyroglobulin which accumulates in the follicles (stored in the colloid) ○​ TSH also opens channel proteins to allow iodine to move in 3.​ Thyroglobulin is iodized to form T1 and T2 4.​ T1 and T2 linked to form T3 and T4 5.​ T3 and T4 are packaged into lysosomes in follicular cells ○​ T3 / T4 moves from colloid into the follicular cells 6.​ Lysosomal enzymes free T3 / T4 and release them into the bloodstream 7.​ An increase levels of T4 in the bloodstream inhibit TSH production ○​ Decreased levels of T4 stimulate TSH production b.​ Calcitonin ​ High blood calcium levels are a humoral stimuli for C-cell activity ​ Low blood calcium levels inhibit C-cell activity 3.​ Parathyroid Gland a.​ Parathyroid hormone (PTH)  ​ Low blood calcium levels stimulate parathyroid glands 4.​ Adrenal Glands (Cortex/Medulla) a.​ Mineralocorticoids ​ Produced in the zona glomerulosa ​ Aldosterone secretion is stimulated by ○​ High potassium levels ○​ Low sodium levels ​ When sodium levels are high, aldosterone production stops ○​ Low blood volume ○​ Low blood pressure b.​ Glucocorticoids ​ Made in Zona fasciculata ​ CRH promotes ACTH which promotes cortisol release ​ An increase in cortisol inhibits both CRH and ACTH c.​ Gonadocorticoids ​ ACTH stimulates production of gonadocorticoids ​ Inhibition not noted ​ Once gonadocorticoid production begins, it does not really stop d.​ Epinephrine/Norepinephrine ​ Stimulated by stress 5.​ Pancreas a.​ Glucagon ​ Low blood sugar levels and high amino acid levels exert humoral control (concentration of blood sugar) ○​ Humoral control ​ Sympathetic stimulation of medulla promotes release ○​ Neural control ​ Somatostatin (GHIH) inhibits the release of glucagon ○​ Hormonal control b.​ Insulin ​ High blood sugar levels, High amino acids / fatty acid levels ○​ Humoral control ​ Parasympathetic release of acetylcholine stimulates release ○​ Neural control ​ Hormonal influences also exist 6.​ Gonads ​ Regulated by gonadotropin levels ○​ Low gonadotropin stimulates the production of FSH/ LH ​ An increase of FSH and LH will lead to the development of gonadal hormones ○​ High gonadal hormones shuts off production of gonadotropins 7.​ Pineal Gland a.​ Melatonin  ​ UV light inhibits melatonin production ○​ When the sun goes does, melatonin production increases 4. Discuss four mechanisms of mineralocorticoid secretion. Renin-angiotensin mechanism ​ Most important production method of aldosterone 1.​ Stimuli (high potassium, low sodium, low blood pressure, low blood volume) cause kidney cells to make renin 2.​ The liver is always making an inactive protein, called angiotensinogen 3.​ Renin + angiotensinogen = Angiotensin 4.​ Angiotensin stimulates adrenal cortex to produce aldosterone Plasma Concentration Mechanism 1.​ High levels of potassium, or low levels of sodium can stimulate the zona glomerulosa of adrenal cortex directly to make aldosterone ACTH Mechanism 1.​ Directly stimulates adrenal cortex ​ Does not do much for mineralcorticoid production, ○​ ACTH mostly affects glucocorticoid production Atrial Natriuretic Peptide (ANP) 1.​ Produced by the heart ​ Shuts off aldosterone production if blood pressure is high Lecture Objectives: Reproduction 1. Describe the structure and function of the testes, and explain the importance of their location in the scrotum. Structure ​ Testes are the organ that produces gametes ​ The scrotum is a sac-like structure composed of skin and superficial fascia ​ Divided into compartments called lobules ○​ Lobules are further divided into seminiferous tubules ○​ Each lobule has a series of seminiferous tubules ​ Path of sperm:  ○​ Seminiferous tubules -> tubulus rectus -> rete testis -> efferent ductules -> epididymis -> ductus/vas deferens -> ejaculatory duct -> urethra ○​ Seminiferous empty directly into the tubulus rectus which empties directly into the rete testis etc ​ It is entirely directly continually connected Function ​ The purpose of the testes are to produce gametes Importance of Location in the Scrotum ​ Allows maintenance of optimal temperature ○​ Via dartos and cremaster muscles raise and lower testes depending on environmental temperature ○​ The testes must be kept 3* C cooler than the core body temperature in order to produce viable sperm ​ Testicular Blood Flow ○​ Blood going to the testes flow through the testicular arteries ○​ This blood passes through the pampiniform plexus ​ This is a modification of the testicular veins that acts to cool the blood in the testicular arteries ○​ After the cooled blood passes through the testes, the blood is drained by testicular veins 2. Describe the structure of the penis, and identify the physiological changes that occur during the reproductive process. Structure ​ Specialized copulatory organ ○​ “aiming device” ○​ The penis is the organ that allows male gametes to be delivered inside the female’s body ​ Glans is covered with prepuce (foreskin) ○​ Circumcision is the removal of the prepuce ​ Two types of erectile tissue: ○​ Corpus spongiosum ​ When engorged, it allows the urethra to stay open to allow gametes to leave the penis during ejaculation  ○​ Corpura cavernosum ​ Blood fills this space during sexual arousal ​ Both erectile tissues are a spongy network of connective tissue, smooth muscle, and vascular space ○​ Sexual arousal causes an increase in dilation of blood vessels and blood fill in that space ​ In males, the urethra carries both urine and reproductive fluids ​ Penis has three components ○​ Root ​ Inside the abdominal cavity ○​ Shaft ​ External ○​ Glans ​ “Head” of the penis Physiological Changes of the Penis ​ Erection (P for point, parasympathetic) ○​ Sexual arousal causes parasympathetic reflex to release nitric oxide in the penis ​ Release of nitric oxide is typically due to visual stimulation ○​ Nitric oxide causes arteriole dilation so more blood can enter ○​ Erectile bodies fill (engorge) with blood ○​ Corpus cavernosum expands, and compresses the drainage veins and blood gets stuck there ​ Because blood can't leave the veins, an erection occurs ○​ Bulbourethral gland stimulated by the parasympathetic nervous system ​ Ejaculation (S for shoot, sympathetic) ○​ Continuous stimulation (tactile,friction) causes massive sympathetic nerve discharge ○​ Reproductive ducts and accessory glands contract, pushing their contents into the urethra ○​ The bladder sphincter muscles constrict at the same time to shut off connection between the urethra and the bladder ​ Occurs from sympathetic stimulation ​ Alcohol can inhibit the constricting of the bladder sphincter ○​ Smooth muscles of penis undergo rapid series of contractions that results in ejaculation ○​ Semen is propelled from the penis ○​ Ejaculation and orgasms coincide for males. ​ Men must reach orgasm for fertilization to occur ​ This is not true for females 3. Describe the location and function of the male accessory reproductive organs. 1.​ Seminal Vesicles ​ Location ​ One on either side of the ejaculatory ducts ​ Function ​ Produces a fluid that is highly alkaline (basic pH) ​ Female reproductive tract is highly acidic ○​ Without seminal vesicle fluid, sperm would die from the acidity of the vaginal canal 2.​ Prostate Gland ​ Location ​ Single gland near where the ejaculatory duct becomes the urethra ​ Function ​ Secretes nutrients and enzymes to nourish sperm 3.​ Bulbourethral/Cowper’s Glands ​ Location (slide 14 and 15 on Reproduction powerpoint) ​ Posterior and lateral to the membranous portion of the urethra ​ Function ​ Secretes a clear and viscous mucus into the urethra ○​ This mucus eliminates urine crystals Etc ( nitrogen would kill the sperm) ​ Cleanses the urethra ○​ This fluid reduces trauma of insertion into female reproductive tract ​ This gland is stimulated before ejaculation, the secretions are secreted before ejaculation 4. Discuss the components of semen, and the contribution each makes to the reproductive process. ​ Semen is composed of sperm as well as secretions from the seminal vesicles, prostate gland, and bulbourethral glands 5. Outline the events of spermatogenesis, explain spermiogenesis, and describe the function of Sertoli cells. Spermatogenesis ​ Occurs in the outer edges of the seminiferous tubules ○​ Sperm do not mature until they are in the epididymis, and they still can't fertilize until in the female reproductive tract ​ Sperm production does not occur until puberty 1.​ Diploid spermatogonia undergo mitosis to produce Type A and Type B daughter cells  ​ Type A cells are the replacement cells for the spermatogonia ​ Type B cells are called primary spermatocytes (diploid; barely differentiated) 2.​ Primary spermatocytes undergo meiosis 1 to become secondary spermatocytes (haploid) 3.​ Secondary spermatocytes undergo meiosis II to become spermatids Spermiogenesis 1.​ Spermatid decreases cytoplasmic volume ​ Gets rid of lots of its organelles ​ Keeps and packs DNA 2.​ Forms tail called flagellum 3.​ Forms midpiece that has lots of mitochondria ​ Gets nutrients from prostate gland to make energy for the flagellum to contract 4.​ Acrosome at top of head contains enzymes used in fertilization ★​ Results in the production of four genetically different haploid cells ★​ The finished product of spermiogenesis is known as a spermatozoa Sertoli/Sustentacular/Nurse Cells ​ Protect spermatocytes from the immune system ○​ Forms the blood-testes barrier ​ Secretes fluid to move sperm from Lumen into the epididymis ​ Disposes of eliminated cytoplasm ​ Regulates spermatogenesis through hormones 6. Discuss the hormones involved in reproduction for the male.​ ​ The hypothalamus releases GnRH ​ GnRH stimulates the release of pituitary gonadotropins (FSH/ LH) 1.​ FSH ​ Stimulate sertoli cells to release androgen- binding protein (ABP) ​ ABP accumulates on spermatogonia ​ ABP causes spermatogonia to accumulate testosterone ○​ ABP acts as a receptor for testosterone ○​ Testosterone binds to ABP 2.​ LH ​ Causes interstitial cells to secrete testosterone ​ Also causes a small amount of estrogen to be secreted 3.​ Testosterone ​ Stimulates spermatogenesis ​ Inhibits GnRH when testosterone accumulates ○​ Inhibits gonadotropin released  ​ Has anabolic effects on accessory reproductive organs ○​ It enlarges them ​ Promotes male secondary sex characteristic ○​ Deep voice, muscle mass, oily skin, hair development ​ Boosts basal metabolic rate (BMR) ○​ Makes it harder to put on weight ○​ BMR decreases after 35 due to the decrease in the production of testosterone ​ Influences Behavior ○​ Linked with aggression and sex drive in both men and women 4.​ Inhibin ​ Produced by Sertoli cells when sperm count is high ​ Inhibits release of FSH by inhibiting GnRH ○​ Stops sperm production 7. Describe the location, structure, and function of each of the organs in the female reproductive system. Ovaries ​ No direct pathway with oviduct ​ Ovaries have outer cortex and inner medulla ○​ Gametes are formed in the cortex ○​ Gametes exist as ovarian follicle ​ Ovarian follicle made of the oocyte + follicular and granulosa cells Ovarian Follicles ​ Primordial follicle ○​ Oocyte surrounded by follicular cells ​ Single layer of cells around the oocyte ​ Primary follicle ○​ Contains follicular and granulosa cells surrounding the oocyte ​ Secondary follicle ○​ Contains theca folliculi ​ Connective tissue ring surrounding granulosa cells ○​ Has fluid-filled space with fluid called antrum ​ Graafian follicle ○​ Distinguishable by the presence of the corona radiata ​ The stalk that holds the oocyte in place ​ Ovulation occurs ​ Corpus luteum ○​ Develops from the corpus hemorrhagicum ○​ If no fertilization occurs, the corpus luteum shuts off after 14 days  ○​ If fertilization occurs, the corpus luteum last for three months until the placenta takes over hormone production Oviducts (Fallopian tubes/uterine tube) ​ Ovulated oocyte released into the peritoneal cavity ​ Ciliated fimbriae sweep oocyte into the oviduct ○​ Due to hormonal signaling ​ Path through oviduct ○​ Infundibulum, ampulla, isthmus ​ Ultimately transported to the uterus ​ Normal site of fertilization is in the ampulla ○​ The fertilized egg will continue into the uterus ○​ If no fertilization occurs, the egg will travel to the uterus Uterus ​ Thick walled muscular organ that receives, retains, and nourishes fertilized ovum ​ Made up of the ○​ Body ○​ Fundus ○​ Cervix ​ The cervix has a canal that runs through it (os) ​ Internal/external os ​ Diameter of the canal is hair like; during birth the canal dilates to 10cm ​ Os will seal if zygote implants ​ Called cervical plug or mucus plug ​ Uterine wall layers ○​ Perimetrium ​ Surrounding layer ○​ Myometrium ​ Muscular layer of the uterus ○​ Endometrium ​ Lining of the uterus ​ Has two layers ​ Endometrium Strata ○​ Stratum functionalis ​ Closer to the lumen ​ Goes through the build-up process under hormonal influence ○​ Stratum basalis ​ Always present ​ Builds up to form Stratum functionalis ○​ If no fertilization occurs, the Stratum functionalis breaks down ​ This is menstruation Vagina  ​ Female organ of copulation ​ Acts as a birth canal ○​ Stratum functionalis of the uterine endometrium goes through the vaginal canal during menstruation if no fertilization occurs ​ Acidic environment ○​ Helps destroy foreign pathogens ○​ Can also destroy sperm ​ Contains the hymen ○​ Thin membrane ○​ Can tear during childhood ○​ Historically was used as a sign of chastity and purity External Genitalia ​ Mons pubis ○​ Pad of fatty tissue on top of the pelvis ○​ Contains lots of hair follicles ​ Hair can protect against friction and damage ​ Hair can act as a wick for perspiration and act as a filter for foreign objects to prevent entry into the vagina ○​ Protect pelvis ​ Labia majora ○​ External folds ○​ Rich with hair follicles ​ Labia minora ○​ Internal Folds ○​ Directly covers the vestibule ​ Greater vestibular glands ○​ Produces mucus ○​ Upon sexual arousal, releases mucus to help with insertion of penis ​ Clitoris ○​ Concentrated nerve endings ○​ Can cause muscle contractions and sense of pleasure without ejaculation ​ Perineum ○​ Tissue between vulva and anus ○​ May be surgically cut during delivery ​ If not cut during delivery, the baby's head can tear the perineum 8. Discuss the structure and function of the mammary glands. Structure ​ Modified sweat glands  ○​ Contain lots of proteins and fats ​ Mammary glands are divided into lobes ○​ Compartment ​ Lobules ○​ Smaller compartments ​ Alveoli ○​ Tiny sacs that are the site of milk production ​ Lactiferous ducts ○​ Once milk is produced, milk goes from the alveoli into the lactiferous ducts ​ Lactiferous sinus ○​ The lactiferous ducts carry the milk to the lactiferous sinus behind the nipple ​ Nipple ○​ Where suckling occurs ○​ Where milk is released from ​ Areola ○​ The darker tissue surrounding the nipple Function ​ Mammary glands function to produce milk to nourish newborns ​ Both sexes have these parts, but milk production only becomes functional in women because of hormonal changes (PIH inhibits milk production in males). Lecture Objectives: Female Reproductive Physiology 1. Describe the process of oogenesis and compare it to spermatogenesis Pre-puberty ​ Diploid oogonia undergo mitosis to produce primary oocytes ○​ Incorporates follicular cells to become primordial follicle ​ The follicular cells are a single layer of cells around the oocyte ​ Primary oocyte begins meiosis 1 ○​ Arrested at prophase 1 ​ Stops before birth ★​ A woman is born with primary oocytes arrested in prophase I with primordial follicles around the primary oocytes. Post-puberty ​ Meiosis 1 completes and produces first polar body and secondary oocyte ○​ The secondary oocyte is haploid  ​ First polar body undergoes meiosis II and produces two polar bodies ​ Secondary oocyte begins meiosis II ○​ Arrested at metaphase 2 ​ Secondary oocyte is ovulated Post-Ovulation ​ If fertilization occurs: ○​ Secondary oocyte completes meiosis II ​ Produces an ovum and a polar body ​ If no fertilization occurs: ○​ Secondary oocyte degenerates ​ Gets sloughed off during menstruation Comparison to Spermatogenesis ​ Spermatogenesis and oogenesis both begin with a diploid cell that undergoes mitosis ○​ In spermatogenesis, the diploid cell is a spermatogonia ○​ In oogenesis, the diploid cell is an oogonia ​ During spermatogenesis, one primary spermatocyte leads to the production of four viable, haploid, genetically different gametes ​ Oogenesis ends with one viable, haploid gamete 2. Describe the phases of the ovarian and uterine cycles, then relay them to one another and the events of oogenesis. Ovarian Cycle ​ Occurs on average every 28 days ○​ Any variability is in the follicular phase Follicular Phase ​ Primordial follicle becomes primary follicle ○​ Occurs under hormonal influence ○​ Primary follicle has follicular cells and granulosa cells ​ Primary follicle becomes secondary follicle ○​ Theca folliculi forms ​ Produce androgens that are converted by granulosa cells into estrogens ○​ Zona pellucida forms ​ Transparent membrane around the oocyte ​ Membrane is rich with glycoproteins ​ Glycoproteins are anchor points for sperm ​ Glycoproteins are receptors for the sperm  ○​ Antrum forms ​ Fluid-filled space ​ Key feature of the secondary follicle ​ Secondary follicle becomes graafian follicle ○​ Corona radiata forms ​ Stalk like feature Ovulation ​ Ovary wall ruptures and expels secondary oocyte and corona radiata into peritoneal cavity ​ Near the time of ovulation, the body temperature slightly increases ​ When ovulating, woman are inclined to have sex Luteal Phase ​ Corpus hemorrhagicum forms ○​ The graafian follicle fills with blood after ovulation ​ Corpus hemorrhagicum resorbs, but granulosa and theca cells produce corpus luteum ​ Corpus luteum secretes progesterone and estrogen ○​ Progesterone stimulates the uterus to get ready for implantation ○​ Estrogen and progesterone work to shut off gonadotropins ○​ Continues until placenta forms if fertilization occurs ​ If no fertilization occurs, the corpus luteum becomes the corpus albicans ○​ Scar connective tissue (granulation tissue) Uterine Cycle (Menstrual Cycle) ​ Menstrual Phase ​ Ovarian hormones at the lowest level ​ Functional layer of endometrium detaches ○​ Since there are low levels of hormones, the lining of the uterus is sloughed off and eliminated ​ Menstruation occurs ​ Corpus luteum is degraded Proliferative Phase ​ Estrogen levels increase ○​ By day 5, follicle begins producing estrogen ​ The functional layer of the endometrium initially begins to rebuild itself because of estrogen  ​ Progesterone receptors develop in endometrial cells ★​ The proliferative phase stops at ovulation ○​ High estrogen and high LH levels Secretory phase ​ Progesterone causes the endometrium to prepare for implantation and forms the cervical plug or mucus plug ○​ Preparation for implantation involves increasing vascularization of the endometrium and increasing mucus production ​ Decreased levels of progesterone and LH initiate breakdown of endometrium ★​ The luteal and secretory phases go hand in hand 3. Identify the hormones involved in regulating these cycles, and discuss the role each plays. ​ The hypothalamus secretes GnRH ○​ From birth to puberty, the ovaries are producing estrogen that inhibits the release of GnRH ○​ When puberty occurs, the hypothalamus changes its sensitivity to estrogen, and GnRH secretion begins ​ GnRH promotes FSH and LH production ​ Rhythmic pulsing production of GnRH until hormonal cycles stabilize ○​ Girl will have her first period ​ This is called menarche ​ This means the hormonal cycle is becoming stable Role of FHS ​ FSH stimulates the follicle, causing growth and maturation of the follicle Role of LH (early in the cycle) ​ Causes thecal cells to produce androgens ○​ The androgens are converted to estrogen by granulosa cells Role of Estrogen  ​ Initial rise in estrogen inhibits the release of FSH and LH ○​ Does not stop the production, just stops the secretion of FSH and LH ​ Stimulates follicle development ○​ Therefore, increase estrogen production ​ Increasing estrogen levels eventually cause a massive release of LH ○​ Called the LH surge Non-cyclic Role of Estrogen ​ Anabolic effects on female reproductive tract ○​ Causes maturation of female sex organs ​ Supply short-term rapid growth spurts at puberty ​ Promotes female secondary sex characteristics ○​ Reduction of hair, suppression of oil production, loss of density of bone and muscle mass, lack of deep voice ○​ Accumulation of lipid storage in the breasts and hips Role of LH (mid-cycle) ​ LH surge stimulates completion of meiosis 1 by dominant follicle ​ Stimulates ovulation ○​ Causes the graafian follicle to burst ○​ Inhibits estrogen production ​ Transforms ruptured follicle into corpus luteum ○​ This stimulates progesterone and estrogen production Role of Progesterone ​ Inhibits FSH and LH production ○​ Prevents the development of more follicles ​ Prepares the uterus for implantation ○​ Increases vascularization in the walls of the endometrium Role of Inhibin ​ Inhibin comes from the corpus luteum ​ Inhibits FSH and LH production ○​ No more follicular development ★​ Inhibin progesterone and estrogen work together to shut off GnRH 4. Differentiate the female sexual response from that of the males.  ​ Arousal for females is similar to that of males ○​ Results from a parasympathetic response ○​ Blood engorgement, especially in the clitoris ​ Blood flow to the surface and walls of the vaginal canal also increase ​ Blood flow to the breasts also increases ○​ Women are more stimulated by touch and thoughts, men are more stimulated visually ○​ Vestibular gland activity because of parasympathetic response ​ Releases viscous, slippery substance to aid with insertion of the penis ​ The female orgasm does not include ejaculation or a refractory period ○​ After one orgasm, continued stimulation can cause multiple orgasms ○​ Female orgasm includes muscle tension, muscle contraction, increase in heart rate, increase in blood pressure, and significant increases in oxytocin ​ Oxytocin causes the feelings of pleasure and relaxation 5. Identify how sex is determined, and discuss the process of sexual differentiation ​ Sex is determined by genetic composition of sperm ○​ Men are heterozygous and can contribute an X or Y gamete ○​ Women are homozygous and only contribute X gametes ​ Male and female embryos are sexually indifferent until approximately two months post conception ○​ Male and female embryos have the same developmental pathway for the first two months Sexual Differentiation ​ Gonadal ridges begin formation about 5 weeks post conception. ​ Mullerian (female) and Wolffian (male) ducts develop ○​ Both ducts start to develop in both males and females ​ Primordial germ (stem) cells are deposited ○​ These are the spermatogonia and oogonia ​ Genital tubercle develops ○​ Becomes external genitalia ○​ Contains: ​ Urethral Groove (external opening) ​ Urethral Folds (folds on side of Groove) ​ Labioscrotal swelling (form on the sides of urethral Folds) Sexual Differentiation (Males)  ​ Seminiferous tubules form and gonadal ridges and Link with Wolffian ducts ​ Developing testes secrete AMH (anti-mullerian hormone) which causes the mullerian duct to degenerate ​ Genital tubercle enlarges to form penis ​ Urethral folds fuse to form urethra ​ Labioscrotal forums fuse to form scrotum ​ Testosterone production guides secondary development ​ The testes descend into the scrotum approximately two months before birth Sexual Differentiation (Females) ​ Gonadal ridges form ovaries ​ Follicles form in the cortex of ovaries ​ Mullerian duct differentiates ​ Wolffian duct degenerates ​ Genital tubercle gives rise to clitoris ​ Urethral Groove becomes the vestibule ​ Urethral fold stay unfused and become labia minora ​ Labioscrotal fold stay unfused and become labia majora ​ Ovaries also descend, but only to pelvic rim 6. Define fertilization, and indicate the time period in which it is possible. ​ Fertilization ○​ When sperm fuses with a secondary oocyte ​ Forms a zygote ​ Zygotes are diploid ○​ Sperm can be viable for up to 72 hours ○​ An oocyte is viable for up to 24 hours ○​ There is a 3 day window of opportunity from when sex occurs that fertilization is possible 7. Identify the barriers acting to prevent fertilization. Barriers to Fertilization ​ Loss of sperm from vagina ○​ When a penis is withdrawn from the vagina, some sperm may not have been deposited into the vaginal canal ○​ Gravity can cause sperm to “fall out” of the vaginal canal ​ Vagina’s acidic environment  ○​ The vagina’s acidic environment can kill sperm ​ Consistency of cervical mucus ○​ Sperm have to work hard to travel through the viscous mucus ​ Phagocytic cells in the uterus ○​ Phagocytic cells in the uterus can phagocytize or break down sperm cells that make it to the uterus 8. Describe the roles of capacitation and the acrosomal reaction in fertilization. Capacitation ​ Sperm are incapable of fertilization immediately after ejaculation ​ Changes in the membrane of the sperm give the sperm the ability to fertilize ○​ The plasma membrane of the sperm must thin down to release its contents ○​ Friction from traveling to the oocyte and enzymes from the prostate gland help to thin the membrane so the acrosome can release its contents ○​ This takes 6-8 hours after ejaculation ​ Also changes activity in the tail Acrosomal Reaction ​ Sperm binds with the zona pellucida ​ Acrosomal enzymes are released into the immediate area ○​ These enzymes break down the zona pellucida ​ Hundreds of sperm are involved in this reaction ​ Allows sperm to penetrate to fertilize the ovum 9. Discuss the mechanisms that prevent more than one sperm from fertilizing the oocyte. Blocks to Polyspermy ​ Fast block ○​ Membrane depolarization ​ When a sperm cell fertilizes the oovum, the membrane depolarizes so that no other sperm can bind to it ​ Slow block ○​ Cortical reaction ​ After fertilization occurs, calcium is released right beneath the plasma membrane ​ This causes an influx of water into the cell underneath the membrane that pushes away the rest of the sperm 10. Name and describe the function of the major embryonic membranes. Embryonic Membranes ​ Chorion ○​ Chorionic villi ​ Acts as the embryo’s part of the placenta ​ Connection to the mother’s circulatory system ○​ Outer membrane ​ Amnion ○​ Amniotic fluid ​ Protects or cushions against trauma ​ This is the fluid responsible for “water breaking” in labor ○​ Inner membrane 11. Describe the various methods of contraception and identify their relative rates of success. ​ Mechanical contraception ○​ Blocks the sperm from getting to the egg ​ Chemical contraception ○​ Kills the sperm or the egg Methods of Contraception ​ Abstinence ○​ 100% effective ​ Birth control medication ​ Vasectomy ○​ 99% effective ○​ Cutting and clipping/cauterizing of vas deferens ​ Withdrawal ○​ 60% effective ​ Condom ○​ 80% effective ​ Tubal ligation ○​ Cutting and clipping/cauterizing of fallopian tubes ​ Spermicides ​ RU486 ○​ Morning after pill ○​ Prevents implantation ○​ Not really contraceptive ​ Rhythm method ​ Abortion ○​ Not really contraceptive