LECTURE 3: CHEMICAL SIGNALS IN ANIMALS Flashcards
Regulatory Mechanisms
- Nervous System
- Endocrine System
conveys high-speed
electrical signals along specialized cells
called neurons; these signals regulate
other cells
nervous system
secretes hormones
that coordinate slower but longer-acting
responses including reproduction,
development, energy metabolism, growth,
and behavior
endocrine system
____________ are chemical
signals that are secreted into the
circulatory system and communicate
regulatory messages within the body
Animal hormones
*Hormones reach all parts of the body,
but only __________ are equipped to
respond
target cells
ex: ________________ is regulated by
hormones
Insect metamorphosis
Two type of Glands in Vertebrate Endocrine System
- Exocrine Gland
- Endocrine Glands
- secrete chemicals into ducts and the
effect is where the duct empties; sweat glands - sweat(evaporative cooling)
Exocrine glands
secrete chemical messengers
(hormones) into the blood for distribution throughout the
animal’s body and bind to specific hormone receptors.
Endocrine glands
- Hormones and other signaling molecules bind to
target receptors, triggering specific response pathways - Chemical signals bind to receptor proteins on target
cells - Only target cells respond to the signal
Target Cell Concept
Hormones and other signaling molecules bind to ____________, triggering specific response pathways
target receptors
Two Factors influencing the hormone concentration in the blood
1, Rate of Hormone Secretion into the blood
2. Rate of Removal of the hormone from the blood (metabolic clearance rate)
Clearance of Hormones from the plasma include:
- Metabolic Destruction
- Binding with the tissue
- excretion by the liver into the bile
- excretion by the kidney into the urine
Refers to the duration of time required to decrease the concentration of a circulating hormones by half
Half life of a hormones
Chemical Messengers
Hormones
Intercellular Communication
- Endocrine Signaling
- Synaptic Signaling
secreted molecules diffuse into the bloodstream and trigger responses in target cells anywhere in the body
Endocrine signaling
Types of Endocrine Signaling
- Paracrine Signaling
- Autocrine Signaling
secreted molecules
diffuse locally and trigger a response in
neighboring cells
Paracrine signaling
secreted molecules
diffuse locally and trigger a response in
the cells that secrete them
Autocrine signaling
neurotransmitters
diffuse across synapses and trigger
responses in cells of target tissues
Synaptic signaling
neurohormones diffuse into the
bloodstream and trigger responses
Neuroendocrrine signaling
Secreted chemical signals include
o Local regulators
o Neurotransmitters
o Neurohormones
o Pheromones
o Hormones
- chemical signals that travel over short
distances by diffusion - help regulate blood pressure, nervous system
function, and reproduction - divided into two types
Local Regulators
Types of Local Regulators
Paracrine and Autocrine
act on cells near the
secreting cell
Paracrine signals
act on the secreting cell
itself
Autocrine signals
proteins and
polypeptides that stimulate cell
proliferation
Growth factors
Growth factors
Cytokines
-acts as a neurotransmitter when secreted
by neurons
-kills bacteria and cancer cells when
secreted by WBCs
-dilates the walls of blood vessels when
secreted by endothelial cells
Nitric oxide (NO)
-modified fatty acids
-secreted by the placenta stimulate uterine
contractions during childbirth
-promote fever and inflammation and
intensify the sensation of pain
-regulate aggregation of platelets (early
step in blood clot formation)
Prostaglandins (PGs)
-secreted by neurons at many synapses
-diffuse a very short distance
-bind receptors on target cells
-play a role in sensation, memory,
cognition, and movement
-Acetylcholine (ACh) – muscle contraction
Neurotransmitters
-secreted by neurosecretory cells
-diffuse from nerve cell endings into
the bloodstream
-ADH (vasopressin) – increases
water permeability of kidney’s
collecting ducts and causes
vasoconstriction (ADH)
Neurohormones
-chemical signals that are released from
the body and used to communicate with
other individuals in the species
- mark trails leading to food
- defining territories
- warning of predators
- attracting potential mates
Pheromones
- chemicals that transfer information and
instructions between cells in animals and
plants - body’s chemical messengers
- regulate growth and development
- control the function of various tissues
- support reproductive functions
- regulate metabolism
- slow acting but long lasting
Hormones
-Animal hormones - chemical signals that are
secreted into the circulatory system and
communicate regulatory messages within the body
- reach all parts of the body, but only target cells
have receptors for that hormone
The Body’s Long-Distance Regulators
________ _________ loop
inhibits a
response by
reducing the
initial stimulus,
thus preventing
excessive
pathway activity
Negative
feedback
________ ______
reinforces a
stimulus to
produce an
even greater
response
Positive
feedback
The same hormone may have different
effects on target cells that have
-Different receptors for the hormone
- Different signal transduction pathways
- Different proteins for carrying out the
response
A hormone can also have different effects in
_______________
different species
Different_____________________ in different cells can lead to different responses to the same signal
signal-transduction pathways
Three major classes of molecules function
as hormones in vertebrates:
- Polypeptides (proteins and peptides)
- Amines derived from amino acids
- Steroid hormones
polypeptides and amines
water-soluble
- steroid hormones and other
largely nonpolar hormones
lipid-soluble
are secreted
by exocytosis, travel
freely in the
bloodstream, and bind
to cell-surface
receptors
Water-soluble
hormones
Water-soluble molecules bind to receptors
in the ______________ of the target cells
plasma membranes
has multiple effects
in mediating the body’s
response to short-term
stress
epinephrine
epinephrine binds to
receptors on the
plasma membrane of
________
liver cells
triggers the release of
messenger molecules
that activate enzymes
and result in the
release of glucose into
the bloodstream
Glucagon
diffuse across cell
membranes, travel in the
bloodstream bound to
transport proteins, and
diffuse through the
membrane of target cells
Lipid-soluble hormones
Lipid-soluble hormones bind to receptors in
the __________ or ___________ of
the target cells
cytoplasm or nucleus
response is usually a
change in gene
expression
Lipid-soluble molecules
_______________ binds to
its cytosolic receptor, a
hormone-receptor
complex forms that
moves into the nucleus
steroid hormone
receptor part of the
complex acts as a
_________________
of specific target genes
transcriptional regulator
Signaling by any of these hormones
involves three key events:
-Reception
-Signal transduction
-Response
Water-soluble hormones respond
Gene regulation and Cytoplasmic response
Lipid-soluble Hormones response in change in
Gene Expression7
