hormone in animals
TRANSCRIPT
Body Regulation
Endocrine Systems
Principles of Endocrine Control
- endocrine glands: ductless glands secreting chemical messengers (hormones) which diffuse directly into blood and carried to target organs to exert a specific physiological effects
Nervous co-ordination gives rapid control.Endocrine co-ordination regulates long-term
changes.
The two systems interact in a dynamic way in order to maintain the constancy of the animal's internal environment, while permitting changes in response to a varying external environment.
Both systems secrete chemicals, the nervous system as a transmitter between neurones and the endocrine system as its sole means of communication between various organs and tissues in the body. .
Chemistry of Hormones Steroids - oestrogen, progesterone, testosterone,
cortisone, aldosterone Polypeptides (less than 100 amino acids) -
oxytocin, insulin, glucagon, antidiuretic hormone (vasopressin)
Amines - adrenaline, noradrenaline, thyroxine Proteins - prolactin, follicle stimulating
hormone, luteinizing hormone, thyroid stimulating hormone, adrenocorticotrophic hormone, growth hormone
Pituitary gland- The “master” endocrine gland. Controls other endocrine glands
The Hypothalamus & the Pituitary The Hypothalamus & the Pituitary Gland-- Master Endocrine Glands!Gland-- Master Endocrine Glands!
The Hypothalamus: Located in the brain,
this region controls most endocrine secretions
Mainly regulatory hormones are released here. Most control the pituitary gland
The Pituitary Gland Descending from the
hypothalamus, this gland has two halves: anterior & posterior
The anterior half secretes mainly regulatory hormones
The posterior half secretes hormones, but manufactures none
The Posterior Pituitary LobeThe Posterior Pituitary Lobe
No hormones are made here. They are made in the hypothalamus and just released here.
Two peptide hormones are released from the posterior pituitary lobe (the neurohypophysis):
ADH (antidiuretic hormone or vasopressin) OT (oxytocin)
Function of Posterior Pituitary Lobe Function of Posterior Pituitary Lobe HormonesHormones
ADHosmoregulation as an “antidiuretic,” ADH
decreases urine formation by having kidneys conserve water
also can contract smooth muscle cells, as found in blood vessels-- this causes an increase in blood pressure
ADH release triggered by osmoreceptors and inhibited by stretch receptors in blood vessels
OT: In females, contracts
the uterine wall smooth muscles
In females, helps to eject milk when lactating
No known function in males, although in both males and females, OT can have some antidiuretic effects
LactationLactation
In females, PRL promotes milk synthesis Milk release is stimulated by oxytocin Milk contains an inhibitory peptide to stop
lactation when not required. In males, PRL decreases LH secretion (note
that too much PRL would then decrease androgen levels and cause sterility)
Hormones secreted by the Hypothalamus & Hormones secreted by the Hypothalamus & Anterior Pituitary GlandAnterior Pituitary Gland
Hypothalamus Anterior PituitaryGHRH (GH-releasing) GH (growth hormone)
SS (somatostatin, GH-inhib) “CRH (corticotropin-rel) ACTH
(adrenocorticotropic)
GnRH (gonadotropin-rel) LH (luteinizing hormone)
“ FSH (follicle-stimulating)
PRH (PRL-releasing) PRL (prolactin)
PIH (PRL rel-inhibiting) “TRH (thyrotropin-rel) TSH (thyroid stimulating)
What do these anterior pituitary What do these anterior pituitary hormones do?hormones do?
Growth Hormone: stimulates cells to grow
and divide increases amino acid
transport rate and protein synthesis
increases fat metabolismTypically, GH is secreted
during sleep.GH secretion increases
when malnourished
GH influences bone growth via somatomedin:
GH in bloodGH arrives in liverliver secretes
somatomedincartilage dividesbones grow!
Hormones of the complex– releasing hormones
of the hypothalamus• TSHr
– ant. pituitary hormones: thyrotropin
– thyroxine
How are hormones regulated?How are hormones regulated?Hypothalamus-Pituitary-ThyroidHypothalamus-Pituitary-Thyroid
Thyroid
Negative Feedback
Click for animation
thyroid– thyroxine (T4),
triiodothyronine (T3)• increase oxidative metabolism• protein distribution and
metabolism
Hormones of the thyroidHormones of the thyroid
About the Thyroid Hormones...About the Thyroid Hormones...
T3 and T4: Function: metabolism regulation (break
down carbohydrates and fats, synthesize proteins)
Can only be made by follicular cells when iodides are available
Somewhat hydrophobic and get carried by proteins in the blood.
T3 more effective, T4 more abundant
Problems with the Thyroid GlandProblems with the Thyroid Gland
Hyperthyroidism: high metabolic rate, hyperactivity, sensitivity to heat, protruding
eyes Grave’s disease: when hyperthyroidism is due to an
autoimmune problem (TSH is mimicked by autoantibodies)
Hypothyroidism: in the adult: low metabolic rate, sensitivity to cold,
sluggishness in an infant: cretinism-- stunted growth, mental retardation,
abnormal bone formation goiter: no T3 and T4 can be made because not enough
iodides were ingested.
Goiter- without iodine, functional hormones cannot be made. Lack of iodine in our diet can lead to enlargement of thyroid gland (goiter) Uncommon in U.S. because of iodized salt
Pancreas- Produces insulin and glucagon
1. Regulates the metabolism of glucose (sugar)
2. Insulin decreases sugar and glucagon increases glucose levels.
3. Diabetes mellitus- condition where there is an undersecretion of insulin. Results in high level of glucose in blood.
Adrenal Glands- pyramid-shaped structures that sit on kidneys
1. Produces adrenaline (also called epinephrine) released during “fight or flight” situations
2. Increases blood glucose level, heart rate.
Hormones of the Adrenal GlandsHormones of the Adrenal Glands
Adrenal Medulla produces two hormones that regulate the “fight or flight” response– adrenalin (epinephrine)– noradrenalin (norepinephrine)
Hormones of the Adrenal GlandsHormones of the Adrenal Glands
Adrenal Cortex produces many hormones– steroids
• glucocorticoids (cortisol, corticosterone, cortisone)– cause a rise in blood sugar
Hormones of the Adrenal GlandsHormones of the Adrenal Glands
Adrenal Cortex produces many hormones– steroids
• mineralcorticoids (e.g., aldosterone)– regulates bp, bv, salt balance,
Other Endocrine GlandsOther Endocrine Glands
Reproductive glands (the gonads): the ovaries and the testes produce sex hormones
Reproductive Glands (the gonads)
1. Male gonads (testes) produce sperm. Control growth of facial hair, increase body size, deepening of voice, etc. (testosterone)
Female gonads (ovaries) produce eggs (ova). Control widening of hips, development of breasts, prepares uterus for arrival of developing embryo (estrogens, progesterone)
Negative Feedback of HormonesNegative Feedback of Hormones
Low concentrations of a particular hormone result in increased secretion of that hormone, and when the concentration reaches a certain level, secretion is reduced
Control of the Endocrine System
A. Regulated by negative-feedback mechanism that functions to maintain homeostasis
1. When target tissue responds to hormone- sends chemical back to gland
2. Gland stops producing hormone
3. If level of hormone to low- gland signaled to start secretion of hormone again
B. Automatic and self-regulating
Blood Glucose Regulation by the PancreasBlood Glucose Regulation by the PancreasGlucagon:It works on the liver to
cause the production of glucose via:– glycogenolysis– gluconeogenesis
It is regulated by blood glucose levels directly:– secreted when blood
glucose drops (before next meal)
Prevents hypoglycemia
Insulin:
It works on the liver to remove glucose from the blood via:– making glycogen– preventing gluconeogenesis– increasing glucose transport
into cells
It is also regulated by blood glucose levels directly
Prevents hyperglycemia
Note: glucagon and insulin work in opposition, and their combined effects control blood glucose
Pancreas: Regulation of GlucosePancreas: Regulation of Glucose
Diabetes results from pancreatic malfunction or receptor malfunction– alpha cells secrete glucagon (release of glucose)– beta cells secrete insulin (uptake of glucose)
Balance of glucagon and insulin determine blood glucose levels