Transcript Concept 45.2: Hormones and other chemical signals bind to

Paracrine Signaling by Local
Regulators
• In paracrine signaling, nonhormonal
chemical signals called local regulators elicit
responses in nearby target cells
• Types of local regulators:
– Neurotransmitters
– Cytokines and growth factors
– Nitric oxide
– Prostaglandins
• Prostaglandins help regulate aggregation of
platelets, an early step in formation of blood
clots
LE 45-6
Hypothalamus
Pineal gland
Pituitary gland
Thyroid gland
Parathyroid glands
Adrenal glands
Pancreas
Ovary
(female)
Testis
(male)
Concept 45.2: Hormones and other
chemical signals bind to target cell
receptors, initiating pathways that
culminate in specific cell responses
• Hormones convey information via the
bloodstream to target cells throughout the
body
• Three major classes of molecules function
as hormones in vertebrates:
– Proteins and peptides
– Amines derived from amino acids
– Steroids
• Signaling by any of these hormones
involves three key events:
– Reception
– Signal transduction
– Response
Epinephrine
(also known as Adrenaline)
Epinephrine
(also known as Adrenaline)
Tyrosine
(an amino acid)
LE 45-3
SECRETORY
CELL
SECRETORY
CELL
Hormone
molecule
VIA
BLOOD
Hormone
molecule
VIA
BLOOD
Signal receptor
TARGET
CELL
TARGET
CELL
Signal
transduction
pathway
OR
Signal
receptor
Cytoplasmic
response
DNA
Signal
transduction
and response
mRNA
DNA
NUCLEUS
Nuclear
response
NUCLEUS
Receptor in plasma membrane
Synthesis of
specific proteins
Receptor in cell nucleus
Intracellular Receptors for
Lipid-Soluble Hormones
• Steroids, thyroid hormones, and the hormonal
form of vitamin D enter target cells and bind
to protein receptors in the cytoplasm or
nucleus
• Protein-receptor complexes then act as
transcription factors in the nucleus, regulating
transcription of specific genes
LE 4-9
Estradiol
Female lion
Testosterone
Male lion
LE 45-3
SECRETORY
CELL
SECRETORY
CELL
Hormone
molecule
VIA
BLOOD
Hormone
molecule
VIA
BLOOD
Signal receptor
TARGET
CELL
TARGET
CELL
Signal
transduction
pathway
OR
Signal
receptor
Cytoplasmic
response
DNA
Signal
transduction
and response
mRNA
DNA
NUCLEUS
Nuclear
response
NUCLEUS
Receptor in plasma membrane
Synthesis of
specific proteins
Receptor in cell nucleus
LE 45-4
different cell responses
Different receptors
Epinephrine
Epinephrine
Epinephrine
a receptor
 receptor
 receptor
Glycogen
deposits
Vessel
constricts
Intestinal blood
vessel
Vessel
dilates
Skeletal muscle
blood vessel
Different intracellular proteins
Glycogen
breaks down
and glucose
is released
from cell
Liver cell
different cell responses
LE 45-3
SECRETORY
CELL
SECRETORY
CELL
Hormone
molecule
VIA
BLOOD
Hormone
molecule
VIA
BLOOD
Signal receptor
TARGET
CELL
TARGET
CELL
Signal
transduction
pathway
OR
Signal
receptor
Cytoplasmic
response
DNA
Signal
transduction
and response
mRNA
DNA
NUCLEUS
Nuclear
response
NUCLEUS
Receptor in plasma membrane
Synthesis of
specific proteins
Receptor in cell nucleus
cAMP
(cyclic Adenosine
Monophosphate)
Which of the following statements about hormones is
correct?
– A. Steroid and peptide hormones produce different
effects but use the same biochemical mechanisms.
– B. Steroid and peptide hormones produce the same
effects but differ in the mechanisms that produce the
effects.
– C. Steroid hormones affect the synthesis of proteins,
whereas peptide hormones affect the activity of
proteins already present in the cell.
– D. Steroid hormones affect the activity of certain
proteins within the cell, whereas peptide hormones
directly affect the processing of mRNA.
– E. Steroid hormones affect the synthesis of proteins to
be exported from the cell, whereas peptide hormones
affect the synthesis of proteins that remain in the cell.