Review notes for chapter 39: Endocrine and Reproductive ...



Review notes for chapter 39: Endocrine and Reproductive Systems

The Endocrine System

The endocrine system is made up of glands that release their products into the bloodstream. These products broadcast messages throughout the body.

Hormones-“chemical messengers”-they are chemicals that travel through the bloodstream and affect the activities of other cells

-hormones bind to specific chemical receptors on other cells

-cells that have receptors for a particular hormone are referred to as target cells, cells that have no receptors are not affected by hormones

-the body’s response to hormones is slower and longer-lasting than the responses to nerve impulses

-most hormones can be classified as either Protein-type hormones, which consist of chains of amino acids or related compounds. These hormones cannot pass through the cell membrane because they cannot dissolve in the lipids that are present in the cell membrane. Insulin is an example of this typed of hormone. Steroid hormones such as Estrogen are lipid like, are able to pass through the cell membrane, and regulate gene expression. They are also produced from cholesterol

Glands

-glands are organs that produce and release secretions

-exocrine glands release their secretions through tube like structures called ducts (include those that release sweat, tears, and digestive juices)

-endocrine glands release their secretions directly into the bloodstream

-major endocrine glands in the body:

Hypothalamus-makes hormones that control the pituitary gland, makes hormones that are stored in the pituitary gland

Pituitary gland-produces hormones that regulate many of the other endocrine glands. Anterior pituitary and posterior pituitary

secretes:

ADH-stimulates the kidneys to reabsorb water

Oxytocin-stimulates contractions of the uterus during childbirth and releases milk in nursing mothers

FSH-stimulates production of eggs and sperm

LH-stimulates ovaries and testes

GH-stimulates protein synthesis and growth in cells

ACTH-stimulates the release of hormones from adrenal cortex

MSH-stimulates the melanocytes of the skin

Parathyroid glands- 4 glands that release parathyroid hormone, which regulates the level of calcium in the blood

Thymus-during childhood, they thymus releases thymosin, which stimulates T cell development

Adrenal glands-release epinephrine and norepinephrine, which helps the body, deal with stress

Pineal gland-releases melatonin, which is involved in rhythmic activities, such as daily sleep-wake cycles

Thyroid-produces thyroxine, which regulates metabolism

Pancreas-produces insulin and glucagons, which regulate the level of glucose in the blood. Islets of Langerhans are scattered throughout the pancreas, containing two types of cells: alpha and beta cells. Alpha cells secrete glucagon and beta cells secrete insulin

**when the pancreas produces too little insulin, diabetes mellitus occurs. Two types of diabetes: Type I, (most common in people before the age of 15) there is little or no secretion of insulin and Type II (more common in people after the age of 40) low to normal levels of insulin**

Ovary-ovaries produce estrogen and progesterone. Estrogen is required for the development of female secondary sex characteristics and for the development of eggs. Progesterone prepares the uterus for a fertilized egg

Testis-the testes produce testosterone, which is responsible for sperm production and the development of male secondary sex characteristics

Prostaglandins

-hormone like substances produced by other kinds of cells and tissues

-they are known as “local hormones” because they generally affect only nearby cells and tissues

-some cause smooth muscles to contract

-one group also causes the sensation of pain in most headaches

Control of the endocrine system

-the endocrine system is regulated by feedback mechanisms that function to maintain homeostasis

Inhibition

TSH-thyroid-stimulating hormone

TRH-thyroid-releasing hormone

↓ ←

Hypothalamus→TRH→Anterior Pituitary→TSH→Thryoid→Thyroxine→↑

Complementary hormone action

-refers to the joint control of part of the body’s internal environment by two hormones with opposite effects

-when you lose water, the concentration of dissolved materials in the blood rises, and the hypothalamus responds by signaling the pituitary gland to release antidiuretic hormone (ADH) to slow down the removal of water from the blood and later experience the sensation of thirst

The Reproductive System

Reproduction is the formation of new individuals. Organisms can reproduce sexually or asexually. Asexual reproduction is a process where one parent reproduces by itself. Sexual reproduction is a type of reproduction in which two parents give rise to offspring that have a unique combination of genetic material

Asexual reproduction

-There is no involvement of gametes

-Binary Fission-a parent cell divides into two new daughter cells the same size as the parent with the same kind and quantity of DNA. This is common in protozoans, bacteria, and some algae

-Budding - is a type of asexual reproduction in which an outgrowth on a yeast cell grows and separates from the parent cell and functions as an individual. This can occur in the hydra

-Spore formation- a cell undergoes a series of cell divisions inside its own cell wall. Each new cell produces a thick wall of its own, and the old cell wall becomes a spore case holding small thick-walled cells, the spores. These grow into new individuals

Sexual Reproduction

-Puberty is a period of rapid growth and sexual maturation during which the reproductive system becomes fully functional. LSH and FH levels are increased. Secondary sex characteristics develop. In males, growth of facial and body hair increase in body size, and deepening of the voice. In females, development of the reproductive system, widening of the hips, and development of the breasts.

Gonads- are structures which produce gametes, a testis is a male gonad and an ovary is a female gonad

The male reproductive system

-the main structures of the male reproductive system are the testes, the epididymis, the vas deferens, the urethra, and the penis. These structures work together to produce and deliver sperm.

-the testes descend from the abdomen through a canal into the scrotum, temperature is about one to three degrees lower than the internal body temperature for proper sperm development

-within the testes are the seminiferous tubules, this is where sperm is produced.

-spermatogenesis is the process that results in sperm cell formation

-sperm cells are the male gametes. They consist of a head, a middle piece, and a tail (flagellum)

-the epididymis is a site where the sex cells are stored and where they mature

-a nutrient-rich fluid called seminal fluid, when combined with sperm forms semen

-an ejaculation occurs when sperm cells are ejected from the penis by contractions of the smooth muscles lining the glands in the reproductive tract (200-600 million sperm released per average ejaculation)

The female reproductive system

- the main structures of the female reproductive system are the ovaries, the Fallopian tubes, the uterus, and the vagina. In addition to producing eggs, the female reproductive system prepares the females body to nourish a developing embryo

- during ovulation one sex cell matures and is released from the ovary into the oviduct.

- Clusters of cells surrounding a single egg are called primary follicles

- the hormone that stimulates a follicle to grow and mature each month is FSH

- the egg moves through the Fallopian tubes and during its journey can be fertilized , and then to the uterus

The menstrual cycle

-during the menstrual cycle an egg develops and is released from an ovary, if the egg is not fertilized it is discharged along with the lining of the uterus

-there are four stages to this cycle:

Follicular phase-follicle develops

Ovulation-egg is released from ovary

Luteal phase-egg travels through the Fallopian Tubes

Menstruation-lining of the uterus is shed and is discharged through the vagina (lasts on the average of 3-7 days)

Fertilization

-the process of sperm joining an egg

-the fertilized egg is called a zygote

Early development

Morula-name of the embryo when it is a solid ball of about 50 cells

Blastocyst-name of embryo when it is a hollow ball of cells

Implantation-process in which the blastocyst attaches to the wall of the uterus

Gastrulation-process of cell migration that produces three cell layers

Amnion-membrane that surrounds and protects embryo

Placenta-organ that nourishes the embryo

-after 8 weeks the embryo is called a fetus

-an amniocentesis is a process where a long needle is inserted into the amniotic sac of a pregnant woman at about the sixteenth week of pregnancy. The cells are examined for abnormalities

Childbirth and Early Years

- Birth occurs about nine months after fertilization

- Rhythmic contractions known as labor occur

- Amniotic sac breaks and contractions of the uterus force the baby , usually head first, out of the vagina

- Multiple births can happen due to a situation where two eggs are released and fertilized during the same cycle (fraternal twins) or when a single zygote splits apart to produce two embryos (identical twins)

- Infancy, childhood, adolescence, and adulthood

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