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