Transcript Chapter 45

Chapter 45
Hormones and the Endocrine
System
Tissue Communication
• Extracellular animals have multiple levels of tissue
organization.
• Communication is essential to maintain homeostasis.
• Endotherms vs ectotherms
• Bioregulators are used.
The thermostat function of the hypothalamus and feedback mechanisms in human
thermoregulation
Chemical Signals
• Used for tissue communication
• Secreted chemical signals include
– Local regulators (travel short distances via diffusion)
– Neurotransmitters (nervous or endocrine
communication)
– Hormones (secreted into bloodstream, travel long
distances)
– Neurohormones (nerves that secrete hormones)
Types of Cellular Action
• __________ – impacting yourself.
• __________– impacting your neighbors.
• __________– impacting the next nerve in
sequence. Short distance, quick communication.
• __________– chemical secreted into blood stream.
Impacts distant targets, longer lasting
communication.
• __________– neurons secrete hormones into
bloodstream.
Fig. 45-2
Blood
vessel
Response
(a) Endocrine signaling
Response
(b) Paracrine signaling
Response
(c) Autocrine signaling
Synapse
Neuron
Response
(d) Synaptic signaling
Neurosecretory
cell
Blood
vessel
(e) Neuroendocrine signaling
Response
Integration of Systems
• Hormones impact the body through interrelationships of
the __________ system and the __________ system.
• The endocrine system secretes hormones that coordinate
__________ , but longer-acting responses including
reproduction, development, energy metabolism, growth,
and behavior.
• The nervous system conveys __________ electrical
signals along specialized cells called neurons; these signals
regulate other cells.
• NOTE: Some neurons can secrete hormones…
Neurotransmitters
• Neurons (nerve cells) contact target cells at __________ .
• At synapses, neurons secrete chemical signals called __________
that diffuse a short distance to bind to receptors on the target cell.
• Neurotransmitters play a role in sensation, memory, cognition,
and movement.
• Many neurotransmitters can also serve as __________ .
– Example: Epinephrine (__________ ) during ‘fight or flight’
response
Synapse
Neuron
Response
The Body’s Long-Distance Regulators
• Animal __________ are chemical signals that are secreted
into the circulatory system and communicate regulatory
messages within the body.
• Hormones mediate responses to environmental stimuli and
regulate growth, development, and reproduction.
• Stimuli can include:
– Change in __________
– Another __________
– __________ impulses
– __________ cues
Neurohormones
•
•
•
•
Nerves that secrete hormones into the __________ .
Have long-lasting effects at distant targets.
Can store hormones (weird)
Examples: hypothalamic hormones, oxytocin, antidiuretic hormone
Neurosecretory
cell
Blood
vessel
Response
How Hormones Work…
• Three part system:
– 1. Hormone is secreted
– 2. Travels to distant targets
via bloodstream
– 3. Bind at specific target
cells and cause a specific
response
• Endocrine glands are:
– Ductless glands, secretory
cells
– Well vascularized
– Range in size from individual
cells to entire organs
• Secretion can be turned off
or amplified via feedback
loops
Feedback Mechanisms: Negative
• The goal is to get back to
the ‘norm’.
• Something in the body
needs to be amended
hormone secreted from
endocrine tissue travels
to target tissue target
response deals with
situation, levels rise, etc.
and shuts down further
hormone secretion from
endocrine tissue.
Fig. 45-12-2
Body cells
take up more
glucose.
Insulin
Beta cells of
pancreas
release insulin
into the blood.
Liver takes
up glucose
and stores it
as glycogen.
STIMULUS:
Blood glucose level
rises.
Blood glucose
level declines.
Homeostasis:
Blood glucose level
(about 90 mg/100 mL)
Feedback Mechanisms: Positive
• The goal is to bring
about ‘change’
• Endocrine tissue
secretes hormone 
hormone impacts target
tissue, elicits
response causes
greater production of
original endocrine
tissue
Fig. 45-16
Pathway
Example
Stimulus
Suckling
+
Sensory
neuron
Positive feedback
Hypothalamus/
posterior pituitary
Neurosecretory
cell
Blood
vessel
Target
cells
Response
Posterior pituitary
secretes oxytocin ( )
Smooth muscle in
breasts
Milk release
Fig. 45-10
Major endocrine glands:
Hypothalamus
Pineal gland
Pituitary gland
Thyroid gland
Parathyroid glands
Organs containing
endocrine cells:
Thymus
Heart
Adrenal
glands
Testes
Liver
Stomach
Pancreas
Kidney
Kidney
Small
intestine
Ovaries
A few hormones…
and a few more…
Let’s simplify a bit…
Chemical Classes of Hormones
• Three major classes of molecules function as
hormones in vertebrates:
– __________(proteins and peptides)
– Amines derived from __________
– __________ hormones
Protein (or peptide) Hormones
• Made from proteins (hydrophilic)
• 2 categories:
– Monoamines-made from one amino acid (lots
of neurotransmitters, such as epinephrine)
– Polypeptides-made from multiple amino
acids. Examples: Growth Hormone, Insulin
• Bind to membrane-bound receptors, use
intracellular second messengers for
response
• Can bring about a quick response
• Secreted from:
– Pituitary
– Pancreas
– Parathyroid
Steroid Hormones
• Made from lipids
• All are derived from cholesterol
• Made within:
a. Gonads (testosterone, estrogen)
b. Adrenals (cortisol, aldosterone)
c. Brain (???)
• Bind to intracellular receptors
• Influence gene formation
• Impacts:
–
–
–
–
–
–
Metabolism
Gamete formation
Stress response
Growth
Sex characteristics
Behavior
Coordination of Endocrine and Nervous
Systems in Vertebrates
• The hypothalamus receives information from the nervous
system and initiates responses through the endocrine system.
• It turns neural input into hormonal output through neurohormone
secretions.
• Examples:
• Gonadotropin releasing hormone (GnRH)
• Thyrotropin releasing hormone (TRH)
• Attached to the hypothalamus is the pituitary gland composed
of the anterior pituitary and posterior pituitary.
• Together, these structures regulate lots of hormonal processes.
Fig. 45-14
Cerebrum
Pineal
gland
Thalamus
Cerebellum
Pituitary
gland
Hypothalamus
Spinal cord
Hypothalamus
Posterior
pituitary
Anterior
pituitary
Anterior Pituitary
• The anterior pituitary makes and releases peptide hormones
into the bloodstream under regulation of the hypothalamus.
• The anterior pituitary releases a new hormone in response to
having received one by the hypothalamus.
• These hormones impact a variety of targets.
• Examples:
• Follicle stimulating hormone (FSH)
• Luteinizing hormone (LH)
• Adrenocorticotropic hormone (ACTH)
Posterior Pituitary Hormones
• The posterior pituitary stores and secretes hormones that are
made in the hypothalamus. These are neurohormones.
• Two hormones released from the posterior pituitary act directly
on nonendocrine tissues.
– Oxytocin (OT) induces uterine contractions and the release
of milk
– Antidiuretic hormone (ADH) enhances water reabsorption
in the kidneys
Fig. 45-15
Hypothalamus
Neurosecretory
cells of the
hypothalamus
Axon
Posterior
pituitary
Anterior
pituitary
HORMONE
ADH
Oxytocin
TARGET
Kidney tubules
Mammary glands,
uterine muscles
Some examples:
Endocrine Gland
Pineal gland
Thyroid
Parathyroid
Adrenals
Pancreas (certain cells)
Gonads
What it does…
Serves as biological clock
Regulates metabolism
Calcium regulation
Stress coping, ion regulation
Glucose regulation
Gamete formation, behavior
Plus many, many, many more…..
A practical application:
Diabetes mellitus
• Diabetes mellitus is perhaps the best-known endocrine disorder.
• It is caused by a deficiency of insulin (Type I) or a decreased response
to insulin in target tissues (Type II).
– Type I = usually genetic
– Type II = lifestyle induced, some genetic influence
• It is marked by elevated blood glucose levels.
– Used to be assessed through urine tasting (yuck!)
Insulin and Glucagon:
Control of Blood Glucose
• Diabetes results in the inability
to effectively regulate glucose
levels.
• Insulin and glucagon are
antagonistic hormones that help
maintain glucose homeostasis.
• The pancreas has clusters of
endocrine cells called islets of
Langerhans with alpha cells
that produce glucagon and beta
cells that produce insulin.
Target Tissues for Insulin and Glucagon
• Insulin reduces blood glucose levels by:
– Promoting the cellular uptake of glucose
– Slowing glycogen breakdown in the liver
– Promoting fat storage
• Glucagon increases blood glucose levels by:
– Stimulating conversion of glycogen to glucose in the liver
– Stimulating breakdown of fat and protein into glucose
Fig. 45-12-5
Body cells
take up more
glucose.
Insulin
Beta cells of
pancreas
release insulin
into the blood.
Liver takes
up glucose
and stores it
as glycogen.
STIMULUS:
Blood glucose level
rises.
Blood glucose
level declines.
Homeostasis:
Blood glucose level
(about 90 mg/100 mL)
STIMULUS:
Blood glucose level
falls.
Blood glucose
level rises.
Alpha cells of pancreas
release glucagon.
Liver breaks
down glycogen
and releases
glucose.
Glucagon
Other Applications:
Gamete Production
Birth Control
Secondary Sex
Characteristics
Aggression