Endocrine and Reproductive Systems

Endocrine System

• The Endocrine System is made up of glands that release hormones into the blood.

• These hormones affect organs throughout the body.

Hormones

• Hormones are organic compounds that act by binding to specific receptors on target cells.

• The bodies response to hormones is generally slower than to the nervous system.

• Many endocrine functions depend on two opposing hormones. i.e. insulin and glucagon

Exocrine and Endocrine glands

• Exocrine glands release their secretions through tubes. i.e. sweat, tears, digestive enzymes.

• Endocrine glands release their secretions directly into the bloodstream.

Steriod hormone mechanism of Action

• Steroid hormones pass through the cell membrane of the target cell.

• The steroid hormone binds with a specific receptor in the cytoplasm.

• The receptor bound steroid hormone travels into the nucleus and binds to another specific receptor on the chromatin.

• The steroid hormone-receptor complex calls for the production of messenger RNA (mRNA) molecules, which code for the production of proteins.

Some common steroid hormone structures

Anabolic Steroid hormones

• These are synthetic substances that are related to male sex hormones.

• They stimulate the production of protein which is used to build muscle.

• They increase the production of testosterone.

• Abuse can lead to infertility, hair loss, heart attacks and liver tumors

Nonsteroid Hormones

• Bind to receptors on cell membrane.

• This activates enzymes on the inner surface of the cell.

• These enzymes release secondary messengers, Ca+2, nucleotides, fatty acids and cAMP to relay the message in the cell.

• These messengers can activate or inhibit a wide range of the cells activities.

Nonsteroid hormone examples epinephrine, insulin, serotonin and dopamine

Steroid and nonsteroid hormone actions

Pituitary Gland

• Divided into two parts: anterior and posterior.

• The Pituitary gland produces hormones that directly regulate many body functions or control the actions of other endocrine glands.

Hypothalamus

• Attached to the posterior pituitary.

• It is the link between the brain and the endocrine system.

• It controls the secretions of the pituitary gland.

• It is influenced by the levels of hormones and other substances in the blood.

Hypothalamus II

• It contains neurosecretory cells which have axons in the posterior pituitary.

• ADH – stimulates kidney to absorb water

• Oxytocin- stimulates contractions during childbirth.

• These hormones are stored in the axons in the posterior pituitary.

Hypothalamus and anterior pituitary

• The Hypothalamus produces releasing hormones which are secreted into blood vessels leading to the anterior pituitary.

• These hormones control the secretions of the anterior pituitary

Adrenal Glands - Cortex

• 2 parts Cortex and medulla.

• The cortex produces steroid hormones called corticosteroids.

• Aldosterone regulates blood volume and pressure.

• It is stimulated by dehydration, excessive bleeding or Na+1 deficiency.

Adrenal Gland - medulla

• The medulla produces epinephrine (adrenaline) and norepinephrine.

• These hormones increase heart rate, and blood pressure.

• They widen air passageways and stimulate the release of glucose.

Pancreas

• The Pancreas is both an exocrine and endocrine gland.

• As an exocrine gland it secretes digestive enzymes that flow into the duodenum via the common bile duct.

• As an endocrine gland it secretes insulin and glucagon from the beta and alpha cells of the islets of Langerhans.

Function of insulin and glucagon

• Rising glucose levels, pancreas produces insulin.

• Insulin stimulates cells in the liver, muscle cells and fat tissue to absorb insulin.

• When blood glucose levels fall glucagon is released.

• Glucagon stimulates the liver to break down glycogen and release glucose.

• Glucagon also caused fat cells to break down fat into glucose as well.

Diabetes

• Type 1. Autoimmune disease beta cells killed.

• Patients must watch diet and receive daily doses of insulin to keep blood sugar levels normal.

• Type II. People produce low amounts of insulin or normal amounts, but their cells do not respond to it.

• Type 2. can often be controlled by diet and exercise.

Insulin pump

Thyroid Gland• Major role in regulating

the body’s metabolism.• Thyroid gland produces

thyroxine which increases metabolic rate.

• Iodine is needed for thyroxine – lack can produce a goiter.

• Hyperthyroidism – too much thyroxine.

• Hypothyroidism – too little.

Thyroid and parathyroid

• Thyroid also produces calcitonin which causes the body to absorb less calcium.

• Parathyorid glands produce PTH which causes the body to release calcium from the bones and increase calcium levels in the blood.

Control of Endocrine System.

• The endocrine system is regulated by feedback mechanisms that function to maintain homeostasis.

• H+, Na+1, K+1 and Ca+2, and soluble proteins are controlled by feedback inhibition.

• Thirst

Male Reproductive system• Testes – produce sperm

cells within the seminiferous tubules.

• Epididymis – recieves sperm cells from testes. Stores them as they mature.

• Vas deferens – tube that transports the sperm cells to the urethra.

• Seminal vesicles, prostate, and bulbourethral glands produce seminal fluid .

• Sperm + seminal fluid = Semen

Female Reproductive System

• Ovaries produce the eggs.

• At puberty each ovary contains as many as 400,000 follicles.

• Usually only 400 or so eggs are released in a females lifetime.

Menstrual Cycle

• One ovary produces and releases one ovum every 28 days.

• The process of egg formation and release is part of the menstrual cycle.

• This cycle is regulated by hormones made by the hypothalamus, pituitary, and ovaries.

Follicular phase

• Day 1-14.• Hypothalamus reacts

to low estrogen levels by releasing a hormone that stimulates the anterior pituitary to secrete FSH and LH.

• These two hormones travel to the ovaries where they cause a follicle to mature.

Follicular phase II• Usually just a single follicle,

but sometimes two or even three.

• As the egg develops cells around the egg enlarge and begin to produce increased amounts of estrogen.

• Rising estrogen levels cause the hypothalamus to produce less releasing hormone and the pituitary releases less LH and FSH. Estrogens cause the lining of the uterus to thicken in preparation for receiving a fertilized egg.

Ovulation

• As the follicle grows, it releases more and more estrogen.

• When the estrogen concentration reaches a certain level the hypothalamus releases a burst of LH and FSH

• This causes the follicle to rupture and the egg is released to the fallopian tubes.

Luteal phase

• Follicle cells turn yellow and become the corpus luteum.

• Corpus luteum releases estrogen and progesterone.

• Progesterone stimulates the development of the uterine lining.

• As these hormone levels rise LH and FSH are inhibited.

• And so additional follicles do not develop during this cycle.

Menstruation

• No fertilization and LH levels fall and corpus luteum degenerates.

• Low estrogen levels cause the lining of the unterine wall to detach and become discharged through the vagina.

• This cycle lasts 3 to 7 days on average.

STD’s

• Diseases spread by sexual contact.

• 2008 1 in 4 girls aged 14 to 19 had an STD.

• Chlamydia, a bacterial disease, is the most common disease in the US.

• Other bacterial diseases include syphilis and gonorrhea.

Viral STD’s

• Include AIDS, hepatitis B, genital herpes and genital warts.

• A vaccine has been developed to protect against genital warts which can lead to cervical cancer.

Fertilization

• Sperm meet the egg in the fallopian tubes.

• Sperm head releases powerful enzymes that break down the egg’s protective layer.

• Once the two haploid nuclei fuse the egg is fertilized and is now called a zygote.

In vitro fertilization

Gastrulation – from single layer blastocyst to three-layered gastrula.

Neuralation

Placenta

Fetal development