Ch 40 (Exm 2) Flashcards
hormones
Chemical signals for the control and regulation of cells
hormones are secreted by cells of the __
endocrine system into the extracellular fluid
Endocrine gland
group of endocrine cells that form a secretory organ
Secrete hormone directly into the extra cellular fluid
Circulating hormones
diffuse into blood and are carried to target cells throughout the body (ex: testosterone)
Paracrine hormones
released and affect only cells nearby
- Small amounts released, quickly taken up by local cells, or quickly degraded so they do not diffuse into circulations
Ex: histamine
Autocrine hormones
affect the same cell which released the hormone
- Can provide negative feedback for production of the hormone
Growth in arthropods is episodic
punctuated with molts
Each stage between molts is called an instar
Sir Vincent Wigglesworth
and his
experiments with the blood-sucking
insect Rhodnius
A blood meal triggers each molting event
hormones and evolution
- signaling molecules themselves (hormones) are highly conserved but functions may differ
- Plants have hormones
- Sponges have chemical communication similar to hormone activation
hormones in insects
Sir Vincent Wigglesworth exp 2
decapitated two bugs at different times after blood meal
Connected bugs with glass tubing
Both molted!
Substance from bug decapitated 1 week earlier
must have diffused to other bug and
Stimulated molting
Sir Vincent Wigglesworth conclusion
Endocrine and Nervous system work together: Nervous system receives various types of information to help determine optimal time for growth and development
Nervous system then controls the
endocrine gland producing the hormone
that causes a physiological response
Lipid-soluble hormones
diffuse through cell membrane – receptors inside the cell
often act to alter gene expression
Water-soluble hormones
cannot pass through membrane – receptors on the surface of the cell
Receptors are
glycoproteins with three domains:
three domains of glycoproteins
Binding domain, Transmembrane domain, Cytoplasmic domain
Binding domain
proteins outside the membrane
Transmembrane domain
anchors the receptor in the membrane
Cytoplasmic domain
- extends into the cytoplasm of the cell
- Initiates the target cell response by activating protein kinases or protein
phosphatases - These will then activate or inactivate enzymes in the cytoplasm
- Initiate a signaling cascade
Epinephrine
fight or flight response
Pituitary gland
- sits at base of skull just over back of the roof of the mouth
- Is attached by a stalk to the hypothalamus
- Involved in the hormonal control of many physiological processes
hormones from hypothalamus are stored and released by pituitary
Posterior pituitary
releases two peptide hormones – antidiuretic hormone and oxytocin
These hormones are synthesized in neurons in the hypothalamus – neurohormones
Vesicles containing neurohormones travel down axons from hypothalamus into
post. pituitary where they are stored
Nerve impulses will trigger their release
Antidiuretic hormone
increases the amount of water conserved by the kidneys
When secretion is high – kidney secretes a little concentrated urine
When secretion is low – kidneys produce lots of dilute urine
Oxytocin
produced during labor in women, stimulates contractions of the uterus
Brings about flow of milk
Suckling, sight, sounds of baby can stimulate production of oxytocin
Anterior pituitary
many peptide and protein hormones released
many are tropic
tropic
control the activities of other endocrine glands
Growth hormone
acts on a wide variety of tissues to promote growth
Stimulates cells to take up amino acids
Stimulates liver to produce factors that stimulate the growth of bone and
cartilage
Overproduction – gigantism
Underproduction – pituitary dwarfism
Prolactin
stimulates breast development and the production and secretion of milk
Important hormone during pregnancy
Endorphins and enkephalins
body’s natural opiates
In the brain act as neurotransmitters in pathways that control pain
anterior pituitary is controlled by
hypothalamic neurohormones
Hypothalamus receives information from the body through neuronal and hormonal signals through circulation
Portal blood vessels connect the hypothalamus to anterior pituitary -
Neurohormones travel in the portal blood vessels into anterior pituitary where they stimulate or inhibit the release of anterior pituitary hormones
tropic hormones of the anterior pituitary
Thyrotropin, Gonadotropic hormone, Corticotropin hormone
Thyrotropin
acts on thyroid
Tropic hormones of the Anterior pituitary:
Gonadotropic hormone
acts on gonads for release of sex hormones
Tropic hormones of the Anterior pituitary:
Corticotropin hormone
acts on adrenal glands
Tropic hormones of the Anterior pituitary:
Negative feedback loops control hormone secretion:
Cells of the Anterior pituitary under direct and indirect negative feedback control by the hormones of the target glands they stimulate
Thyroid
wraps around front of the windpipe
Thyroxine
thyroid gland
- require iodine
- regulates cell metabolism
- lipid soluble so it can bind to receptors
- affects genes involved in enzymes active in energy, transport, structural proteins
- elevates the metabolic rates
- activated by thyrotropin from anterior pituitary
Hyperthyroidism
- excess of thryoxine
- can cause goiter when negative feed fails t turn off follicle cells
- thyroid grows bigger
Hypothyroidism
thyroxine deficiency
- Goiter can result when not enough circulating Thyroxine to turn off Thyrotropin production in the anterior pituitary. make more follicle cells
Calcitonin
thyroid hormone
- lowers Ca in blood
- can deposit or absorb Ca in bone
- can excrete or keep Ca by kidneys
- absorption of Ca or not in Gi tract
When blood calcium is high
alcitonin is triggered and signals more deposition of calcium into bone by
Osteoblasts – take up circulating calcium and deposit new bone
Parathyroid glands
- make parathyroid hormone on surface of thyroid gland
- - Fall in blood calcium triggers the release of PTH
fall in blood calcium
- release of PTH
- stimulates bone turnover and remodeling
- stimulates kidneys to reabsorb calcium rather than excrete it in urine
- activates Vitamin D which causes digestive tract to absorb more calcium
- acts on kidneys to increase elimination of phosphate in urine
pancreas
endocrine gland located just below the stomach
Contains clusters of cells call islets (islets of Langerhans)
three times of islet cells
alpha, beta, delta
beta cells
secrete insulin
alpha cells
glucagon
delta cells
produce the hormone somatostatin
insulin
Binds to a receptor on plasma membrane of target cell and allows glucose to
enter the cell
If glucose cannot enter the cell it accumulates in the blood
Cells must then use fat and protein for fuel instead of glucose
Critical tissues and organs can be damaged
Glucagon
- produced by alpha cells in islets
- When blood glucose is low, stimulates liver to convert glycogen to glucose to
- resupply the blood
Diabetes
destruction or failure of beta cells to produce or secrete insulin
type 1 diabetes:
- Autoimmune disease: body’s own cells destroy the insulin producing cells (beta cells)
- Irreversible. No mechanism to replace the beta cells
- Dependent on an outside source of insulin
Starts as a child (earlier onset)
Type 2:
- can have genetic link
- Often related to diet/lifestyle/ obesity
- Develop an insulin insensitivity due to diet.
- Can be reversible if caught in early stages. Change diet, exercise etc.
Adrenal gland
- sits above above each kidney
adrenal cortex
- cortex, produces steroid hormones, under the control of corticotropin from anterior pituitary
adrenal medulla
- core, called the adrenal medulla, makes epinephrine and norepinephrine
Epinephrine and Norepinephrine
- amine hormones
- Both bind to the same receptors on the surface of target cells
- Stimulate different actions within the cells
- Epinephrine binds both types of receptors
- Norepinephrine binds only alpha receptors
types of receptors
alpha-adrenergic or beta-adrenergic receptors
what does adrenal cortex make
use cholesterol to make steroid hormones:
glucocorticoids (cortisol), mineralocorticoids (aldosterone), sex steroids
glucocorticoids
- influence blood glucose
- EX. cortisol
- mediates stress response, blocks immune reactions, controlled by corticotropin from anterior pituitary
mineralcorticoids
- influence the balance of ions in extracellular fluid
- EX. aldosterone
- Stimulates the kidneys to conserve sodium and to excrete potassium
Sex steroids
- produced by gonads
male steroids
collectively called Androgens – dominant one = testosterone
female steroids
Female steroids – estrogen and progesterone
Dominant estrogen = Estradiol made from testosterone
fetus into sex
after 7 weeks
gonadotropins and puberty
Production increases at the beginning of puberty
Production controlled by Leutinizing Hormone (LH) and Follicle Stimulating Hormone (FSH)
female pubery
increases in LH and FSH at puberty stimulated the ovaries to begin producing female hormones
- This initiates development of breasts, broadened hips, pubic hair, menstrual cycle
male puberty
increases in LH stimulates cells in testes to synthesize testosterone
Initiates deepening of voice, facial and body hair, growth of testes and penis
pineal gland
located between two sides of brain
- makes amine hormone melatonin
- release in the dark
photoperiodicity
Melatonin is involved in biological rhythms
- seasonal changes in day length cause change in animals
- signal reproductive cycle, sleep-wake cycle etc
Thymosin
produced by the thymus, is important for development of the T cells of the immune system
Gastrin
an important digestive enzyme made by cells in the stomach that can stimulate the release of digestive enzymes
