Download Endocrine System

Endocrine System
Chapter 39
Endocrine System
 A system of glands that secrete hormones into the blood that
regulate growth, development and metabolic processes.
The Endocrine Glands
Section 39-1
Hypothalamus
The hypothalamus makes hormones that
control the pituitary gland. In addition,
it makes hormones that are stored in the
pituitary gland.
Pituitary gland
The pituitary gland produces hormones
that regulate many of the other endocrine
glands.
Parathyroid glands
These four glands release
parathyroid hormone, which
regulate the level of calcium in the
blood.
Thymus
During childhood, the thymus releases
thymosin, which stimulates Tcell
development.
Adrenal glands
The adrenal glands release epinephrine and
nonepinephrine, which help the body deal
with stress.
Pineal gland
The pineal gland releases melatonin, which is involved
in rhythmic activities, such as daily sleep-wake cycles.
Thyroid
The thyroid produces thyroxine, which
regulates metabolism.
Pancreas
The pancreas produces insulin and glucagon, which regulate
the level of glucose in the blood.
Ovary
The ovaries produce estrogen and progesterone. Estrogen is
required for the development of 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
Hormones
 Hormones – chemical messengers that travel to remote
target tissues.
 Produce “slow” responses of long duration.
 Hormones only affect target tissues that have the correct
receptor to fit the hormone.
Section 39-1
Hormone Action
Nonsteroid hormone (first
messenger)
Steroid Hormone
Receptor
Receptor
Target cell
membrane
cAMP (second
messenger)
Hormonereceptor
complex
Altered
cellular
function
Nucleus
Enzyme
activities
DNA
Altered
cellular
function
Protein
synthesis
Cytoplasm
Cytoplasm
mRNA
Nucleus
Target cell
membrane
Negative Feedback
 Hormone levels in the blood are regulated by a negative
feedback mechanism.
 Hormones secreted into the blood bring about a change. When
the change occurs, secretion of the hormone stops.
 Ex: The pancreas secretes insulin to lower blood sugar levels
and glucagon to raise blood sugar levels. Secretion of these
hormones stops when sugar levels are correct.
 Diabetics cannot produce enough insulin to maintain correct sugar levels.
Actions of Insulin and Glucagon
Section 39-2
Pancreas releases
insulin into the blood
Blood glucose
level increases
Body cells absorb
glucose
Liver converts excess
glucose to glycogen
for storage
Blood glucose
level decreases
Homeostasis: Normal blood glucose level
Blood glucose
level increases
Blood glucose
level decreases
Liver converts
glycogen to glucose
Pancreas releases
glucagon into blood
The Reproductive System
Chapter 39
Reproduction
 A life process necessary for the survival of a species, but not
an individual…
The Male Reproductive System
 The testes produce the male sex cell sperm through the process
of meiosis.
 Sperm are haploid (23 chromosomes).
 The testes also produce the hormone testosterone.
 Testosterone aids in sperm production and is responsible for
the development of secondary sex characteristics.
The Male Reproductive System
Section 39-3
The Female Reproductive System
 The ovaries produce the female sex cell eggs through the
process of meiosis.
 Eggs are haploid (23 chromosomes).
 The ovaries also produce the hormones estrogen and
progesterone.
 Estrogen aids in egg development and is responsible for the
formation of secondary sex characteristics. Progesterone
prepares the uterus for implantation by a fertilized egg.
The Female Reproductive System
Section 39-3
The Menstrual Cycle
 Beginning with puberty, the female reproductive system
begins a periodic cycle of events regulated by hormones from
the pituitary and ovaries.
 This is known as the menstrual cycle.
 This cycle prepares the uterus each month for the advent of
pregnancy, when a fertilized egg will implant itself in the
uterine wall.
 If this does not occur, the uterine lining is shed out the vagina.
This is called menstruation.
Section 39-3
The Menstrual Cycle
Fertilization and Development
 Fertilization occurs in the Fallopian tube (oviduct).
 A sperm unites with the egg to produce a diploid zygote (46
chromosomes).
 The zygote undergoes a series of mitotic cell divisions
without growth in size (cleavage) on its way to the uterus.
 Approximately 7 days later the hollow ball of cells
(blastocyst) implants itself in the uterine wall.
 Development occurs in the uterus (womb).
Fertilization and Implantation
Section 39-4
Fallopian tube
Day 2
Day 3
Day 1
Day 4
4 cells
2 cells
Zygote
Morula
Day 7
Blastocyst
Fertilization
Day 0
Implantation of
blastocyst
Uterine wall
Ovary
Egg released by
ovary
Development
 After implantation the cells begin to differentiate.
 Tissue from both the mother and embryo form the placenta
– a temporary organ that will nourish the developing baby.
 Throughout the next nine months the developing baby
obtains nutrients and gets rid of wastes through its
connection to the placenta, the umbilical cord.
 Nutrients and wastes pass between the blood of the mother and
baby by diffusion.
Section 39-4
The Placenta
Birth
 At the end of nine months hormone changes produce a series of
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


contractions in the uterus known as labor.
The protective membrane surrounding the baby (amnion)
ruptures releasing fluid (“water breaks”).
Birth is imminent. Contractions stretch the cervix to a diameter
of about 10 cm and the baby is delivered head first (usually).
Contractions close off the umbilical cord near the baby. The cord
is cut, and eventually falls off leaving a scar (belly button).
Soon after, a second series of contractions force the placenta out
of the womb (after birth).