Endocrine + Reproductive System Overview for TEAS

Purpose/function of endocrine system

The endocrine system uses hormones (chemical messengers) that travel through the bloodstream to regulate long-term processes such as growth, metabolism, reproduction, stress response, and homeostasis.

Difference between nervous and endocrine systems

Nervous:

• Electrical + neurotransmitters

• Fast speed

• Short duration

• Reflexes are an example

Endocrine:

• Includes hormones in blood

• Slower speed

• More long-lasting

• Growth and metabolism are examples

Name the three classifications of hormones, including their chemical structure, solubility, and some examples of each

Steroid hormones:

• are derived from cholesterol (four carbon ring structure)

• are lipid-soluble and can pass through cell membranes, and

• includes cortisol, aldosterone, estrogen, progesterone, and testosterone

Nonsteroid/peptide hormones:

• are composed of amino acid linked together,

• are water-soluble and can bind to cell surface receptors, but cannot pass through the lipid bilayer of membranes, and

• includes insulin, glucagon, ADH, FSH, and LH

Amine hormones:

• derived from a single amino acid

• can be water-soluble or lipid-soluble

• includes epinephrine (adrenaline), norepinephrine, thyroxine (T4), triiodothyronine (T3), and melatonin

What are the functions and receptor locations of the three classifications of hormones?

Think about how they relate to each other.

Steroid hormones:

• intracellular receptor (inside cell; in cytoplasm or nucleus)

• directly influence gene expression and protein synthesis

• long-lasting

Non-steroid hormones:

• bind to receptors on the cell surface (extracellular receptors)

• they activate second messenger systems inside the cell; leading to a cascade of cellular responses

• basically, act through second messengers

• fast

Amine hormones:

• Receptors in membrane or inside cell (can act as water-soluble or lipid-soluble hormones)

HYPOTHALAMUS main endocrine function

to control pituitary and link the nervous + endocrine systems

What four releasing hormones from the hypothalamus are sent to the anterior pituitary for stimulation of its own hormone release?

• TRH (thyrotropin-releasing hormone) → stimulates release of thyroid-stimulating hormone (TSH)

• CRH (corticotropin-releasing hormone) → stimulates the release of adrenocorticotropic hormone (ACTH)

• GnRH (gonadotropin-releasing hormone) → stimulates follicle stimulating hormone (FSH) and luteinizing hormone (LH)

• PRH (prolactin-releasing hormone) → stimulates prolactin

What inhibiting hormones are released from the hypothalamus?

• Somatostatin → inhibits GH (growth hormone)

• Dopamine “happy hormone” → inhibits prolactin

The posterior pituitary stores and releases hormones produced by the hypothalamus, what are those hormones?

• ADH (antidiuretic hormone), a vasopressin that regulates water balance, kidney function, and BP.

  • Water reabsorption in kidney; low urine output

  • Raises BP by constricting blood vessels

• Oxytocin, or the “love hormone”, functions in childbirth (uterine contractions), milk ejection, and emotional bonding.

The anterior pituitary gland, or the “master gland”, makes its own hormones.

Name the (6) hormones, its target organ, and main function.

• TSH (thyroid-stimulating hormone), which targets the thyroid and increases T3/T4 release

• ACTH (adrenocorticotropic hormone), which targets the adrenal cortex to increase cortisol

• FSH (follicle-stimulating hormone), which targets the gonads for egg maturation and sperm production

• LH (luteinizing hormone), which targets the gonads to trigger ovulation, estrogen/progesterone, and testosterone

• GH (growth hormone or somatotropin), targets the liver, bone and muscle, for growth and increase metabolism (increase blood glucose)

• Prolactin, which targets the mammary glands for milk production

The thyroid gland contains follicle cells and parafollicular (C) cells. Each secretes and functions differently.

Name these secretions and functions.

Follicle cells → T3 (triiodothyronine) & T4 (thyroxine)

• increases metabolism

• increases heart rate

• increases body temperature

• Required for growth and development

• Requires iodine

Parafollicular cells (C cells) → Calcitonin

• lowers blood calcium

• inhibits osteoclasts

• increases calcium deposition in bone

Parathyroid glands contain a certain type of cell.

Name this cell, its secretions, and its function.

Chief cells → PTH (parathyroid hormone)

(functions opposite of calcitonin)

• raises blood calcium

• stimulates osteoclasts

• increases calcium reabsorption in kidneys

• activates Vitamin D to increase calcium absorption in intestines

The adrenal cortex is composed of three layers, each producing different hormones, and functioning differently.

Name these layers, hormones, and functions.

GFR = salt, sugar, sex!

• Zona Glomerulosa → produces aldosterone (mineralocorticoid)

  • Increases sodium reabsorption

  • Increases water

  • Increaes BP

• Zona Fasciculata → produces cortisol (glucocorticoid)

  • Stress hormone

  • Increases glucose

  • Anti-inflammatory

• Zona Reticularis → produces androgens

  • Puberty hair and sex drive

The adrenal gland also has the adrenal medulla, which contains a specific cell that releases two hormones.

Name the cell, the hormones, and its function.

Chromaffin cells → Epinephrine & Norepinephrine

• fight-or-flight

• increase heart rate

• increase BP

• increase glucose

• dilates bronchi

The pancreas has clusters of endocrine cells called Islets of Langerhans, which produces hormones. 

Name these cells and their hormone secretions, along with their function.

Alpha cells → produces glucagon to raise blood glucose and breakdown glycogen

Beta cells → produces insulin to lower glucose and promote storage

Delta cells → produces somatostatin to inhibit insulin and glucagon

PP cells → pancreatic polypeptide to regulate pancreas secretion

Insulin and Glucagon are associated with “fasting” and “fed” states.

Which of the following correctly states this relation?

A. Insulin = fed stage; Glucagon = fasting state

B. Glucagon = fed state; Insulin = fasting state

A. Insulin = fed state, glucagon = fasting state.

Name the hormone production and function of the Pineal gland.

Pineal gland produces melatonin

• regulates circadian rhythm

• released in darkness

There are male and female gonads, each produces and secretes hormones for their respective function.

Name the male and female gonads, the hormones, and functions.

Ovaries in females

• Estrogen → female characteristics; endometrial growth

• Progesterone → maintains uterine lining/prepares uterus for pregnancy

• Inhibin → inhibits FSH

Testes in males

• Testosterone → produced by Leydig cells or Interstitial cells; male traits, sperm production

• Inhibin → produced by Sertoli cells or Sustentacular cells; inhibits FSH

What does the Thymus produce and what is its function?

The thymus produces thymosin to promote T cell maturation. The thymus is most active in childhood.

What is the difference between positive and negative feedback loops?

Positive feedback loops enhance or amplify changes, which moves the system away from its equilibrium state.

Negative feedback loops work to stabilize a system by counteracting changes and bringing it back to its equilibrium. Negative feedback loops effectively maintain homeostasis.

What is the most common example of a positive feedback loop? List the steps.

Childbirth!

1) The baby’s head pushes against the cervix and creates pressure

2) Oxytocin releases from the pituitary gland

3) Oxytocin triggers stronger uterine contractions

4) Increased pressure of the cervix = INCREASED release of oxytocin

5) Upon birth, the positive feedback loop stops since the stretching of the cervix stops. No more oxytocin and cycle is completed.

Complete this summarized table of hormones.

Hormone	Source	Target	Function
ADH
Oxytocin
TSH
ACTH
GH
Calcitonin
PTH
Aldosterone
Cortisol
Epinephrine
Insulin
Glucagon
Estrogen
Progesterone
Testosterone

Hormone	Source	Target	Function
ADH	Posterior pituitary	Kidneys	Water retention
Oxytocin	Posterior pituitary	Uterus, breasts	Contractions, milk ejection
TSH	Anterior pituitary	Thyroid	T3/T4 release
ACTH	Anterior pituitary	Adrenal cortex	Cortisol release
GH	Anterior pituitary	Bones/muscles	Growth
Calcitonin	Thyroid C cells	Bone	Lower Ca²⁺
PTH	Parathyroid	Bone/kidney	Raise Ca²⁺
Aldosterone	Adrenal cortex	Kidneys	Na⁺ retention
Cortisol	Adrenal cortex	Liver/muscle	Raise glucose
Epinephrine	Adrenal medulla	Multiple organs	Fight-or-flight
Insulin	Pancreas beta	Body cells	Lower glucose
Glucagon	Pancreas alpha	Liver	Raise glucose
Estrogen	Ovary	Body tissues	Female traits
Progesterone	Ovary	Uterus	Maintains lining
Testosterone	Testes	Body tissues	Male trait

Which hormone lowers blood calcium?

Calcitonin

Which cell produces insulin?

Beta cells

Which hormone is released during dehydration?

ADH

Which gland produces cortisol?

Adrenal cortex

What type of hormone acts on DNA in the nucleus?

Steroid hormones

What gland shrinks after puberty?

Thymus

What does PTH do?

Raises blood calcium

List the types of ovarian follicles in the phases of the ovarian cycle in order.

Follicular Phase

1) Primordial Follicle

• Most basic stage

• Primary oocyte (stuck in prophase l of meiosis) surrounded by a layer of squamous follicle cells

2) Primary Follicle

• Follicle cells become cuboidal granulosa cells

• Zona pellucida forms around oocyte

• Thecal cells develop

3) Secondary Follicle

• Granulosa cells multiply

• Antrum starts forming (small cavities filled with follicular fluid)

4) Vesicular (tertiary) Follicle

• Primary oocyte finishes meiosis l and becomes secondary oocyte

• Large antrum filled with follicular fluid

Ovulation Phase

5) Ruptured Follicle

• secondary oocyte is released from the vesicular follicle into fallopian tube

• Triggered by LH surge

• Oocyte begins meiosis ll, but stops in Metaphase ll until fertilization

Luteal Phase

6) Corpus Luteum

• The remnant of the ruptured follicle

• Mainly secretes progesterone to support pregnancy; also, estrogen + inhibin

7) Corpus Albicans

• The remnant of the corpus luteum after it stops ceases hormone production

• Forms when there is no pregnancy; a decline in progesterone indicates menstruation

List and describe the three endometrial changes in the uterine cycle.

The uterine cycle changes the endometrium to prepare for pregnancy.

1) Menstrual Cycle (day 1-5)

• Triggered by LOW progesterone and estrogen

• Stratum functionalis layer of endometrium is shed → menstruation

2) Proliferative Phase (days 6-14)

• Triggered by rising estrogen

• Endometrium rebuilds

• Endometrial glands form

3) Secretory Phase (days 15-28)

• Triggered by progesterone from corpus luteum

• Spiral arteries convert stratum functionalis to secretory mucosa + endometrial glands secrete uterine milk

Fill in this summary table of the Ovarian vs Uterine Cycles

System	Phase	Dominant Hormone	Major Event
Ovarian
Uterine

System	Phase	Dominant Hormone	Major Event
Ovarian	Follicular	FSH → Estrogen	Follicle maturation
	Ovulation	LH surge	Oocyte released
	Luteal	Progesterone	Corpus luteum active
Uterine	Menstrual	Low hormones	Endometrial shedding
	Proliferative	Estrogen	Endometrium rebuilds
	Secretory	Progesterone	Endometrium ready for implantation

Function of the ovaries

produce oocytes and estrogen, progesterone, and inhibin

Function of the uterine (Fallopian) tube and structures included

• moves oocytes or fertilized ovum toward uterus

• site of fertilization and early stages of development

Structures:

• fimbriae (finger-like)

• infundibulum

• ampulla

• isthmus

Function of the uterus and its layers

• protects and sustains conceptus during pregnancy

• cyclic shedding results in menstrual flow

Layers:

• Perimetrium → outer

• Myometrium → smooth muscle 

• Endometrium → inner lining

Function of the greater vestibular gland of a female

secretes mucus, which helps lubricate the opening of the vagina

Function of the testis

produces sperm cells as well as testosterone and inhibin

Function of the epididymis

• promotes sperm cell maturation

• stores sperm until ejaculation

• moves sperm to ductus deferens

Function of the ductus deferens, ejaculatory duct, and urethra in males

Ductus Deferens

• stores sperm

• moves sperm to ejaculatory duct

• site of vasectomy

Ejaculatory Duct

• transports sperm from ductus deferens into urethra

Urethra

• transports semen out of penis

There are 3 accessory glands of the male reproductive system, what are they and what are their functions?

Seminal Vesicles

• produce 60% semen and secrete:

  • alkaline fluid (neutralize vaginal acidity) with nutrients (fructose)

  • prostaglandins for motility

  • co-agulating enzyme to clot semen in the vagina

Prostate Gland

• secretes fluid that supports sperm, helps activate sperm for fertilization

• anti-coagulant and antibacterial

Bulbourethral Glands

• secretes mucus to lubricate glans penis

• neutralize urine acidity in urethra

Function of the scrotum

encloses, protects, and regulates temperature of testes

• When cold, the cremator muscle contract to lift the testes closer to the warmth of the body while the detrusor muscle causes tightening and wrinkles.

• When hot, the muscles relax to hang lower from the body to reduce surface area for cooling.

What hormone prepares for implantation in females?

progesterone

What hormone triggers the release of gametes in females?

LH (during ovulation)