endocrine system
TRANSCRIPT
THE ENDOCRINE SYSTEMTHE ENDOCRINE SYSTEM
Like the Nervous System, the Endocrine System work through a group of chemical messengers. The endocrine messengers are called hormones.
Hormones: Substances secreted by one group of cells that travel through the blood stream and regulate the metabolic functions of other cells.
Hormones can affect only cells that have receptors that can bind the hormone
Target cells: Those cell types that can be affected by a given hormone
FUNCTIONS OF THE ENDOCRINE SYSTEM
The Endocrine system helps to maintain homeostasis by coordinating and regulating the activities of cells, tissues, organs, and systems throughout the body
The Endocrine System helps to control and integrate:
1- Reproduction
2- Growth
3- Development
4- Defense against stress
5- Water, electrolyte and nutrient balance
6- Energy balance
7- Cellular metabolism
Homeostasis
It is the ability of the human body to maintain relatively stable internal conditions (temperature, PH, etc) even though the outside world changes continuously.
A good homeostasis is indispensable to maintain the organism in good health. Most diseases can be regarded as a result of disturbance of homeostasis.
Example: The body temperature must be near to 37 C (98.6 F). When temperature increases only three degrees (to 40 C), the organism is in danger.
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Temperature: - 20 C Temperature: + 50 C o o
Homeostatic Control Mechanisms maintain the temperature of the bodies near to 37 C, and both men are in good health
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F E E D B A C K S Y S T E M S
Causes the variable to change in a direction opposite to that of the initial change.
Causes the variable to accelerate the change in the same direction that the initial disturbance.
1- Negative feedback mechanisms:
2- Positive feedback mechanisms:
or
or
[Calcium] in blood
Parathyroid hormone is released by parathyroid gland
Stimulates the osteoclasts to resorb bone, releasing calcium to the blood
First Hormonal Mechanism
Second Hormonal Mechanism
Calcitonin hormone is released by thyroid gland
Inhibits osteoclasts to resorb bone, and encourages calcium salt deposit in bone matrix
[Calcium] in blood
[Calcium] in blood
[Calcium] in blood
1- ENDOCRINE SYSTEM IN NEGATIVE FEEDBACK MECHANISMS
SENSOR
EFFECTOR
HYPOTALAMUS
CONTROL CENTER
Example:
PITUITARY GLAND
Positive feedback mechanisms are used to amplify or perpetuate events. They are referred as “cascades”.
2- ENDOCRINE SYSTEM IN POSITIVE FEEDBACK MECHANISMS
Uterine contractions
OXYTOXIN
Neural
electrical
impulses
DELIVERY!
Hypothalamus
Control of Hormone Secretion
Most of hormone secretions are controlled by the Hypothalamus and the Pituitary gland
Pituitary gland
Corpus callosum Septum pellucidum Fornix
Pineal gland
Anterior commissure
Thalamus
Intermediate mass
Hypothalamus Mamillary bodyOptic chiasm
Pituitary gland
Epi- thalamus
Three mechanisms of Hypothalamic Control over Endocrine Function
TSH, FSH, LH, ACTH, GH, PRL,
MSHOxytoxin and Antidiuretic Hormone (ADH)
Posterior lobeAnterior lobe
melanocyte stimulating
hormone
Hormones produced by the Anterior Lobe or Adenohypophysis (1)
2
1
5
Hormones produced by the Anterior Lobe or Adenohypophysis (2)
melanocyte stimulating hormone
4
3
3
6
GONADOTROPINS
Hormones produced by the Hypothalamus and released by the posterior pituitary
Hormonal Control of Water Retention in the Body
The body controls how much water is either sent to the bladder (in urine) or retained in circulation through a hormone called “antidiuretic hormone” (ADH)
When the body needs water, receptors in the hypothalamus sense the increase of solute concentration in the blood, and the hypothalamus orders the release of ADH from the pituitary gland.
ADH works on the distal nephron tubule and the collecting duct increasing their permeability to water. Consequently, more water moves out of the nephron tubule and collecting duct and thus back into circulation
Hormonal Control of Water Retention in the Body
SENSOR
EFFECTOR
HYPOTALAMUS
CONTROL CENTER
PITUITARY GLAND
Uterine contractions
OXYTOXIN
Neural
electrical
impulses
DELIVERY!
The Thyroid Gland
Right lobe
Left lobe
Isthmus
T4 or Thyroxine
T3 or Triiodothyronine
Calcitonin
Thyroid Hormones
1- T4 or thyroxine
2- T3 or triioodothyronine
Follicular hormones (they are produced by the follicular cells)
1- They increase the rate of oxygen uptake and the basal metabolic rate
2- They enhance the effects of sympathetic stimulation (increasing heart rate, blood pressure, nervousness, and sweating)
3- They help to maintain body temperature
4- They help to regulate growth, development, and intracellular metabolism by increasing protein synthesis and lipid breakdown
5- They stimulate RBC formation, and speed up bone turnover
1- T4 or thyroxine
2- T3 or triiodothyronine
3- Calcitonin
3- Calcitonin
It is released in response to high levels of calcium in the blood
Calcitonin hormone is released by thyroid gland
Inhibits osteoclasts to resorb bone, and encourages calcium salt deposit in bone matrix
[Calcium] in blood
[Calcium] in blood
The Parathyroid Glands
Thyroid gland, posterior view
Parathyroid glands
Parathyroid glands
The Parathyroid Hormone
It increases calcium blood levels by targeting bone and kidneys
1- In bones
[Calcium] in blood
Parathyroid hormone is released by parathyroid gland
Stimulates the osteoclasts to resorb bone, releasing calcium to the blood
[Calcium] in blood
2- In kidneys
- It increases calcium reabsortion
- It increases formation and secretion of calcitriol Increases absorption of calcium and
phosphate from the intestines
Adrenal or Suprarenal Glands
Mineralocorticoids(Aldosterone)
Glucocorticoids(Cortisol, Cortisone and
Corticosterone)
Sex hormones( androgens)
Medulla (It is considered part of Sympathetic Autonomic nervous System)
Catecholamines(Epinephrine and Norepinephrine)
Hormones of the Adrenal Glands
1- Mineralocorticoides (Aldosterone)
-It increases sodium ion and water reabsortion in kidneys
-It increases potassium secretion in kidneys
Aldosterone secretion is regulated by the renin-angiotencin mechanism
Blood pressure or plasma solute concentration
Renin-angiotencin mechanism
Aldosterone secretion
2- Glucocorticoids (Corticosterone and Cortisol)
-They help the body to resist stressors
-They depress the immune system and the inflammatory response
3- Gonadocorticoids or Sex Hormones (Androgens)
-They are masculinizing hormones.
- In females they stimulate sexual drive. After menopause they are converted to estrogens.
4- Catecholamines (Epinephrine and Norepinephrine)
-Blood glucose levelsThey increase:-Cardiac activity -Blood pressure-Glycogen breakdown-Triglyceride breakdown
Three mechanisms of Hypothalamic Control over Endocrine Function
The Pancreas
Endocrine pancreas Exocrine pancreas
Pancreatic acini
They secrete large quantities of an alkaline, enzyme rich fluid
Islets of Langerhans
1- Beta cells:
2- Alpha cells:
3- Delta cells:
4- F cells:
Insulin
Glucagon
Somatostatin
Pancreatic polypeptide
1- Glucagon (Released by alpha cells)
-It stimulates the liver to produce glucose
-It stimulates to breakdown glycogen
Glucose in blood Glucagon
(Alpha cells)
Pancreas Liver Glycogen
Glucose
2- Insulin (Released by beta cells)
- High blood glucose
- Parasympathetic stimulation
- High level of some aminoacids
(Beta cells)Pancreas
Insulin
- It increases the rate of glucose uptake by cells
- It increases cellular metabolism
- It increases the storage of lipid and glycogen
- Increases aminoacids absorption and protein synthesis
Seminiferous tube
Primary spermatocyte
Secondary spermatocyte
Spermatids
Sperm (immature)
Spermatogonia
Interstitial or Leydig cells: Produce androgens
(testosterone)
The Gonads
Sustentacular or Sertoli cells: Produce Inhibin
The Development of the Egg
Primary Primary oocytesoocytes
Primary Primary folliclesfollicles
Secondary Secondary folliclesfollicles
Tertiary Tertiary folliclesfollicles
Corpus Corpus luteum luteum ::
FolliclesFollicles: Estrogens and Inhibin
Progesterone
The Pineal Gland
Melatonin:
Pineal gland
1- Inhibiting reproductive functions
2- Protecting against damage for free radicals
3- Setting circadian rhythms
Hormones of the Kidneys
1- Calcitriol:
It stimulates uptake of calcium and phosphate ions from the gut
2- Erythropoietin:
It stimulates the production of red blood cells by red bone marrow
3- Renin:
It converts angiotensinogen into angiotensin-I and starts the cascade of enzymatic changes known as the renin-angiotensin system
Atrial Natriuretic Peptide (ANP)It is produced by the atrial cells of the heart
It reduces the blood volume and blood pressure