Download AP Biology Animal Form and Function

AP BIOLOGY ANIMAL
FORM AND FUNCTION
Endocrine System
Endocrine System
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
The Endocrine System
produces hormones that
help maintain
homeostasis and
regulate reproduction
and development.
A hormone is a
chemical messenger
produced in one part of
the body that affects
target cells in another
part of the body
Hormones



Transported
throughout the body in
the blood
Minute amounts of
hormones can have
significant influence on
target cells
Hormones may be
steroids, peptides, or
modified amino acids
Brain and Hypothalamus


Through the senses, the
brain and
hypothalamus monitors
the external environment
and internal conditions
of the body.
The brain may
determine that some
kind of response is
necessary to maintain
homeostasis.
Neurosecretory Cells


Actions needed to maintain homeostasis are
initiated by special neurosecretory cells that link
the hypothalamus and the pituitary gland.
Neurosecretory cells are structured like neurons, but
instead of secreting neurotransmitters in the
synapses, they secrete hormones into the blood
Pituitary Gland

The Pituitary Gland is the size of a pea and is
divided into posterior and anterior sections. It is
often called the Master Gland because it controls
the actions of other glands.
The Anterior Pituitary is
connected to the
hypothalamus, which
controls the output of
hormones by the
Pituitary Gland.
Anterior Pituitary Gland
The Anterior Pituitary Gland is linked to the
hypothalamus via the bloodstream.
 When the concentration of a particular anterior
pituitary hormone is too low,
the hypothalamus will send
releasing factors via the
bloodstream that stimulate
the production of the needed
hormone.
Anterior Pituitary produces 6
hormones: TSH, STH, ACTH,
LH, FSH, and prolactin

Posterior Pituitary Gland
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The posterior lobe of the pituitary gland is derived
from neural tissue and its connection to the
hypothalamus is neural.
Posterior Pituitary produces 2 hormones: ADH and
oxytocin. These are produced by the nerve cell
bodies that are located in the hypothalamus, where
they are packaged into secretory granules and sent
down the axons to be stored in the posterior
pituitary.
Anterior Pituitary Hormones
FSH: Follicle-stimulating hormone. Stimulates activities
of the ovaries and testes. In females, it stimulates the
development of the ovarian follicle, which leads to the
production and secretion of estrogen.
 LH: Luteinizing hormone.
Stimulates ovulation and
formation of the corpus
luteum. Stimulates synthesis
of estrogen and progesterone

Anterior Pituitary Hormones

STH (or HGH):
Somatotropic hormone
(or Human Growth
Hormone). Stimulates
protein synthesis and
general growth in the
body.
Anterior Pituitary Hormones

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TSH: Thyroidstimulating hormone.
Works to stimulate the
synthesis and secretion
of thyroid hormones
Thyroid hormones
regulate the rate of
metabolism in the
body.
Anterior Pituitary Hormones


ACTH: Stimulates the
secretion of adrenal
cortical hormones, which
work to maintain
electrolytic homeostasis
in the body.
Prolactin: controls
lactogenesis—
production of milk by
the breasts. Decreases
the synthesis and
release of GnRH, and
thus inhibits ovulation.
Posterior Pituitary Hormones

ADH: Stimulates
reabsorption of water
by the collecting ducts
of the nephron in the
kidneys

Oxytocin: Stimulates
uterine contraction and
milk ejection for
breastfeeding.
Hormones of the Adrenal Gland
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The Adrenal Glands are
located on top of the
kidneys.
They produce 3
hormones: Cortisol,
Aldosterone, and
Epinephrine

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Cortisol: a stress
hormone released in
response to
physiological challenges
Aldosterone: Regulates
sodium concentration of
body
Epinephrine: Raises
blood glucose level,
increases metabolic
activity—fight or flight
hormone (aka:
adrenaline)
Pancreatic Hormones

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Insulin—Secreted in
response to high blood
glucose levels
When secreted, it
promotes the
conversion of glucose
in the blood to
glycogen and lowers
blood sugar.

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Glucagon—Stimulates
the conversion of
glycogen into glucose.
Raises blood sugar.
Sex Hormones

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Progesterone: Regulates
menstrual cycle and
pregnancy
Estrogen: Stimulates
development of sex
characteristics in women.
Secreted in ovaries. Induces
the release of LH, including
the LH surge of the
menstrual cycle. With
progesterone, it helps
maintain the endometrium
during pregnancy.
Sex Hormones
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Testosterone—
Stimulates sex
characteristics in men.
Secreted in testes.
Thyroid Hormones and Parathyroid
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Calcitonin: Lowers
blood calcium. Works
antagonistically to PTH
Thyroxine: Stimulates
metabolic activities.

Parathyroid hormone
(PTH); Increases serum
concentration of
Ca2+, assisting in the
process of bone
maintenance.
How is the Hormone Secretion Process
Regulated? – and + Feedback

Negative Feedbackoccurs when a
hormone acts to inhibit
further secretion of the
hormone of interest.

Positive Feedbackoccurs when a
hormone acts to
increase secretion of
the hormone.
Negative Feedback Example:

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Insulin is released by the pancreas.
When the blood glucose gets too high, the pancreas is
stimulated to produce insulin.
This causes cells to use more glucose. As a result of this activity,
the blood glucose levels decline, halting production of insulin.
Positive Feedback Example:


An example of positive feedback is the LH surge
that occurs prior to ovulation in females.
Estrogen is released as a result of the action of FSH.
It travels to the anterior pituitary to stimulate the
release of even more LH, which acts on the ovaries
to stimulate even more estrogen.
Hormones Can Work Antagonistically
to Maintain Homeostasis
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Insulin/Glucagon: Both are hormones of the pancreas
and have opposing effects on blood glucose.
Suppose you just ate a sugary snack that pushes blood
glucose above the desired level. This results in the
release of insulin to stimulate the uptake of glucose
from the blood to the liver to be stored as glycogen.
If you go a long time between meals, however, your
blood glucose may go below the desired level. This
causes glucagon to be released. Glucagon acts on the
liver to stimulate the removal of glycogen from storage
and produce glucose to pump into the bloodstream.