Download IHB Endocrine Sys

Chapter 10
The Endocrine System
The Endocrine System
Endocrine System Characteristics
• Each hormone acts only on specific cells
(target cells)
• Only target cells have receptors for specific
hormones
• Endocrine control slower than nervous
system
• Endocrine and nervous systems
complement each other
Endocrine Functions: Hormones
• Hormones:
– Come from endocrine glands
– Circulate in the blood stream
– Act on specific cells in the body
Exocrine Gland
Classification of Hormones: Steroid Hormones
Lipid-soluble and water-soluble
hormones interact differently with
target cells
• Steroid Hormones:
– Lipid soluble, chemically derived from
cholesterol
– Bind to receptors inside target cells
– Activate specific genes to produce specific
proteins
How Steroid Hormones Act
Characteristics of Non-steroid
Hormones
• Nonsteroid hormones:
– Water soluble
– Bind to receptors on target cell membranes
– Work through intermediate mechanisms
(second messengers) to activate existing
enzymes
– Faster action than steroid hormones; time to
action = seconds to minutes
How water-soluble
hormones act
Hormone Receptors
• All hormones work through receptors
• Target cells (and only target cells) for a
hormone contain receptors for that
hormone
• Example: Estrogen Receptor Knockout
(ERKO) mouse (and human)
In order for a hormone to work on a cell
(or tissue):
A. Receptors are useful but not essential
B. Receptors for that hormone must be
present
Feedback mechanisms regulate
the secretion of hormones
• Refer to in-class worksheet
Hypothalamus and Pituitary Glands
• Hormones from the hypothalamus
regulate the pituitary gland
• Neurosecretory cells: part neuron;
part endocrine organ
• Pituitary hormones often prompt other
glands to release hormones
The Hypothalamus and Anterior
Pituitary Gland
• Anterior pituitary
– Connection to hypothalamus: releasing (and
inhibiting) hormones from hypothalamus travel
to pituitary through pituitary portal vessels
– No nerve connection to hypothalamus
Neurosecretory Cells From the Hypothalamus
Control the Pituitary
True/False
Neurosecretory cells have characteristics
of both hormone secreting cells and
neurons
Hormones of the Pituitary Gland
Hypothalamus and the Posterior
Pituitary Gland
• Posterior pituitary
– Connection to hypothalamus: hormones made in
hypothalamus, stored in posterior pituitary
– Neurosecretory cells project to post. pit.
Hypothalamus and the Posterior
Pituitary Gland
• Posterior pituitary Hormones (protein)
• Antidiuretic hormone (ADH): conserves water
in kidneys, regulates water balance in body
• Regulated by:
–High/Low water intake
–Alcohol
Hypothalamus and the Posterior
Pituitary Gland
• Posterior pituitary Hormones (protein)
• Oxytocin induces:
–Uterine contractions during labor
–Milk ejection through neuroendocrine
reflex
–Behavioral Effects: Love/Trust/Bonding
Oxytocin
Oxytocin
• Human Sexual Response:
– Oxytocin may have a role in sexual arousal,
orgasm & sexual satiety/satisfaction
• CNS: Penile erection, copulatory behavior
• Trust/Love
– Pair bonding
• Maternal Behavior:
• Oxytocin induces maternal behavior in female rats
Oxytocin
Oxytocin and ADH (antidiuretic hormone)
A. Are synthesized and released from
the anterior pituitary gland
B. Are synthesized and released from
the posterior pituitary gland
Posterior Pituitary Disorder
• Diabetes Insipidus: hyposecretion of ADH,
inability to conserve water appropriately
Anterior Pituitary Disorders
• Gigantism: hypersecretion of growth
hormone (during growth phase)
• Pituitary Dwarfism: hyposecretion of growth
hormone (during growth phase)
Anterior Pituitary Disorders
• Acromegaly: hypersecretion of growth
hormone after bones have stopped growth
Acromegaly Symptoms
• Bony changes alter
facial features:
– The brow and lower
jaw protrude
– Spacing of the teeth
increases
– Enlarged jaw
(prognathism), lips,
nose & tongue
Acromegaly
Symptoms
• Enlarged hands and/or feet
– Soft tissue swelling of the
hands & feet is often an
early feature, with patients
noticing a change in ring or
shoe size
• Widened fingers or toes due
to skin overgrowth with
swelling, redness, & pain
Why is Growth Hormone an Abused
Drug?
• Role of GH in Normal Adults
– Increases muscle growth
– Decreases fat stores
Thyroid Gland
Thyroid Gland
• Secretes thyroid hormones:
– Thyroxine (T4) and Triiodothyronine (T3)
Thyroid Gland
• Secretion: regulated by hypothalamus
(TRH) & pituitary (TSH) hormones
• Action of T4 & T3
– Increase metabolic rate & heat prodn.
– Development of fetal nervous system
(cretinism results from lack of T4 & T3)
Disorders of the Thyroid Gland
• Hypothyroidism:
• Children: cretinism
• Adults: myxedema
• Low BMR, Lethargy, Weight gain, Low body temp.
• Hyperthyroidism: Graves Disease
•
•
•
•
Increased BMR
Hyperactivity, nervousness, agitation
Weight loss
Exophthalmos
Hypothyroidism and Goiter
• Causes of Goiter
•Low iodide intake
•Genetic mutation
•Diet
•Direct cause is
excess TSH
secretion
Low Iodide Goiter
Goiters can be caused by:
A. Too little iodide in the diet
B. Too much iodide in the diet
Too little iodide in the diet causes a
goiter because:
A. Not enough T3/T4 is produced
B. Not enough negative fdbk of T3/T4 on
the pituitary/hypothalamus
C. Excess secretion of TSH (Thyroid
Stimulating Hormone)
The factor that most often is the direct
stimulus that causes a goiter is
excess:
A. Iodide
B. T3/T4
C. TSH (Thyroid Stimulating Hormone)
Exophthalmos and Hyperthyroidism
Exophthalmos is caused by oversecretion of the thyroid hormone
which leads to accumulation of fluid behind the eyes causing the eyes
to bulge out.
Hyperthyroidism Patient
Hyperthyroid
Normal
Hypothyroidism and Cretinism
Cretinism is characterized by mental retardation, dwarfism and delayed
sexual development and is caused by undersecretion of thyroid hormone during
fetal life or infancy.