Transcript Ch. 45 Endocrine System

Endocrine System
Ch. 45
AP Biology
Ms. Haut
Overview: The Body’s LongDistance Regulators

An animal hormone
– Is a chemical signal that is secreted into the
circulatory system and communicates regulatory
messages within the body

Hormones may reach all parts of the body
– But only certain types of cells, target cells, are
equipped to respond
Regulatory Systems

Endocrine System
– All of an animal’s hormone-secreting cells
– Secretes hormones that coordinate slower but longer-
acting responses to stimuli
– Endocrine glands



Ductless glands
Secrete chemical messengers directly into blood stream
Nervous System
– Conveys high-speed electrical signals along specialized
cells called neurons
Hormones involved in Control
of Development in Insects

Control molting of
exoskeletons and
metamorphosis in
insects
 After a meal, a brain
hormone is released and
moves to the prothorasic
gland
 The brain hormone
stimulates the release of
ecdysone which
stimulates molting
Brain
1 Neurosecretory cells in the brain produce
brain hormone (BH), which is stored in
the corpora cardiaca (singular, corpus
cardiacum) until release.
Neurosecretory cells
Brain
hormone (BH)
Corpus cardiacum
Corpus allatum
Low
JH
Prothoracic
gland
Ecdysone
Juvenile
hormone
(JH)
2 BH signals its main target
organ, the prothoracic
gland, to produce the
hormone ecdysone.
3 Ecdysone secretion
from the prothoracic
gland is episodic, with
each release stimulating
a molt.
EARLY
LARVA
LATER
LARVA
4 Juvenile hormone (JH), secreted by the corpora allata,
determines the result of the molt. At relatively high concentrations of JH, ecdysone-stimulated molting produces
another larval stage. JH suppresses metamorphosis.
But when levels of JH fall below a certain concentration, a
pupa forms at the next ecdysone-induced molt. The adult
insect emerges from the pupa.
PUPA
ADULT
Control Pathways and Feedback Loops
Pathway
Example
Low blood
glucose
Stimulus

There are
three
types of
hormonal
control
pathways
Receptor
protein
Pancreas
secretes
glucagon ( )
Endocrine
cell
Blood
vessel
Target
effectors
Response
Pathway
Stimulus
Example
Example
Pathway
Suckling
Hypothalamic
neurohormone
released in
response to
Sensory
neural and
neuron
hormonal
signals
Hypothalamus
Sensory
neuron
Hypothalamus/
posterior pituitary
Neurosecretory
cell
Posterior pituitary
secretes oxytocin
Blood ( )
vessel
Stimulus
Neurosecretory
cell
Hypothalamus
secretes prolactinBlood
releasing
vessel
hormone ( )
Liver
Glycogen
breakdown,
glucose release
into blood
(a) Simple endocrine pathway
Target
effectors
Response
Smooth muscle
in breast
Milk release
Anterior
pituitary
secretes
Endocrine prolactin ( )
cell
Blood
vessel
(b) Simple neurohormone pathway
Target
effectors
Response
Figure 45.2a–c
Mammary glands
Milk production
(c) Simple neuroendocrine pathway

Three major classes of molecules function
as hormones in vertebrates
– Proteins and peptides
– Amines derived from amino acids
– Steroids

Signaling by any of these molecules
involves three key events
– Reception
– Signal transduction
– Response
Major human endocrine glands and some
of their hormones
Page 899
Table 45.1
Page 899
Table 45.1
Vertebrate Endocrine System

In addition to the
glands shown
here, many
organs also
secrete hormones
– Digestive system
produces at least
8 hormones (e.g.
gastrin, secretin)
Integration of the Hypothalamus
and Posterior Pituitary

Regulation of blood osmolarity
– Monitored by nerve cells
(osmoreceptors) in the
hypothalamus
–  plasma osmolarity causes
cells to shrink slightly and
transmit nerve impulses to
certain neurosecretory cells
– Cells in posterior pituitary
release antidiuretic hormone
(ADH)
– ADH targets kidney tubules—
increasing water permeability
of collecting ducts
– Water diffuses to capillaries to
decrease osmolarity
– Homeostasis is maintained!!
Integration of the Hypothalamus
and Anterior Pituitary

Hypothalamus produces releasing hormones and inhibiting hormones
into capillaries to affect anterior pituitary
Tropic Effects Only (target endocrine glands)
FSH, follicle-stimulating hormone
LH, luteinizing hormone
TSH, thyroid-stimulating hormone
ACTH, adrenocorticotropic hormone
Nontropic Effects Only (target other tissues)
Prolactin
MSH, melanocyte-stimulating hormone
Endorphin
Nontropic and Tropic Effects
Growth hormone
Thyroid and Parathyroid Hormones

Plays role in
development and
maturation and
homeostasis and
metabolism
 Produces two
iodine-containing
hormones,
triiodothyronine
(T3) and thyroxine
(T4)-regulated by
hypothalamus and
pituitary
Regulated by 2 negative feedback loops
Pancreas
Islets of Langerhans-consists of clusters of 2 cell types
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 the conversion of glycogen to
glucose in the liver
– Stimulating the breakdown of fat and protein
into glucose
Diabetes Mellitus

Diabetes mellitus, perhaps the best-known
endocrine disorder
– Is caused by a deficiency of insulin or a
decreased response to insulin in target tissues
– Is marked by elevated blood glucose levels

Type I diabetes mellitus (insulin-dependent
diabetes)
–

Is an autoimmune disorder in which the immune system
destroys the beta cells of the pancreas
Type II diabetes mellitus (non-insulin-dependent
diabetes)
–
Is characterized either by a deficiency of insulin or,
more commonly, by reduced responsiveness of target
cells due to some change in insulin receptors
Adrenal Gland


Are adjacent to the kidneys
Are actually made up of two glands: the adrenal medulla and
the adrenal cortex
Gonadal Steroids

Regulate growth, development, reproductive
cycles, and sexual behavior
 Testes
– Androgens (testosterone)



Stimulate development and maintenance of male reproductive
system
At puberty, high concentrations responsible for male secondary
sex characteristics
Ovaries
– Estrogens (estradiol)
– Parallel role in females
– Progestins—prepare and maintain uterus for support of
offspring
↑Estrogens (secreted by
follicle) = thickening and
vascularization of
endometrium
Melatonin and Biorhythms

The pineal gland, located
within the brain
– Secretes melatonin
– Release of melatonin

Is controlled by light/dark
cycles
– The primary functions of
melatonin

Appear to be related to
biological rhythms associated
with reproduction