Lecture 3: Chemical Signals in Animals Flashcards
Regulatory Mechanism
Nervous system and 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
chemical
signals that are secreted into the
circulatory system and communicate
regulatory messages within the body
Animal Hormones
Two Types of Glands
Exocrine glands and 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
Experiment on hen
Arnold Adolph Berthold (1849)
Human development regulation
Signaling pathways
Signaling pathways are regulated by…
specific chemical signaling molecules
- Hormones and other signaling molecules bind to
target receptors, triggering specific response pathways - Chemical signals bind to receptor proteins on target
cells - Only cells that respond to the signal
Target Cells
Intercellular Communication
- Endocrine Signaling
- Paracrine Signaling
- Direct Signaling
Endocrine Signaling
Neuroendocrine
Paracrine Signaling
- Autocrine
- Synaptic
- secreted molecules diffuse into the bloodstream
and trigger responses in target cells
anywhere in the body. - Relatively slow.
Endocrine Signaling
neurohormones diffuse into the
bloodstream and trigger responses
Neuroendocrine
- secreted molecules
diffuse locally and trigger a response in
neighboring cells. - Quick response.
Paracrine Signaling
secreted molecules
diffuse locally and trigger a response in
the cells that secrete them
Autocrine
neurotransmitters diffuse across synapses
and trigger responses in cells of target
tissues
Synaptic/Neural Signaling
- for some signals to be
received, the cells must be in direct contact. - Either via interacting membrane proteins on two
different cells, or through special cell-cell junctions.
Direct Signaling
signals act on cells near the
secreting cell
Paracrine
signals act on the secreting cell
itself
Autocrine
proteins and
polypeptides that stimulate cell
proliferation
Growth Factors
play a role in immune
responses
Cytokines
Fast Signaling
Juxtacrine Signaling
For Animals
Gap Junctions
For Plants
Plasmodesmata
- 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)
The mechanism of erection of the penis involves the release of nitric oxide
(NO) in the ________ during sexual stimulation.
Corpus Cavernosum
enhances the effect of NO by inhibiting phosphodiesterase
type 5 (PDE5), which is responsible for the degradation of cGMP in the corpus
cavernosum
Sildenafil (Viagra)
- 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)
Prostaglandine (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
Neurotransmitters
muscle contraction
Acetylcholine (ACh)
- secreted by neurosecretory cells
-diffuse from nerve cell endings into
the bloodstream
Neurohormones
increases
water permeability of kidney’s
collecting ducts and causes
vasoconstriction (ADH)
ADH (vasopressin)
- chemical signals that are released from
the body and used to communicate with - ther 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
chemical signals that are
secreted into the circulatory system and
communicate regulatory messages within the body
Animal Hormones
Three major classes of molecules function
as hormones in vertebrates:
- Polypeptides (proteins and peptides)
- Amines derived from amino acids
- Steroid hormones
water-soluble
polypeptides and amines
lipid-soluble
steroid hormones and other
largely non-polar hormones
Water-soluble hormones are
secreted by _______, travel
freely in the bloodstream, and
bind to cell-surface receptors
Exocytosis
They bind to receptors in the
_______ of the target
cells
plasma membranes
- has
multiple effects
in mediating the body’s
response to short-term
stress - 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
Epinephrine
hormones diffuse across cell membranes, travel in the bloodstream bound to
transport proteins, and
diffuse through the membrane of target cells
Lipid-soluble
Signaling by any of these hormones
involves three key events:
- Reception
- Signal Transduction
- Amplification
- Response
detection of a signal in
the environment
Reception
activating a
series of proteins inside the cell
Signal Transduction
change in behavior that
occurs inside the cell
Response
