View
263
Download
3
Category
Preview:
Citation preview
Endocrine System Role of the Endocrine System
Hormones: Types
Transport of Hormones
Interaction of Hormones with Target Cells
Effects of Hormones on Target
Control Mechanisms of Endocrine Glands
Endocrine Organs
• Pituitary (Anterior and Posterior)
• Thyroid
• Parathyroids
• Adrenals (Cortex, Medulla)
• Pancreas
• Gonads
Ovaries
Testes
The Endocrine System A more broad-based and long-lasting
communication system than the nervous system
Uses chemical messages (hormones) that are released into the blood
Hormones control several major processes
• Reproduction
• Growth and development
• Mobilization of body defenses
• Maintenance of much of homeostasis
• Regulation of metabolism
Types of Hormones Protein-based hormones
Steroid hormones
Prostaglandins and catecholamines
Insulin Growth hormone
Hormones as Chemical Messengers
Endocrine gland (source)
Target organs or glands
Hormones move through the bloodstream to target organs
Hormone Interaction with Target Cells Hormones bind to receptors sticking out from the plasma membrane of
target cells or within target cells
growth factor insulin epinephrine
Hormones
Examples of receptors found in the plasma membrane of cells
Receptors
Effects Caused by Hormones Changes in electrical state of the cell,
stimulating change
Causes enzymes to be made, changing metabolic abilities of target cell
Turn on or off enzymes that alter metabolism inside cell
Stimulate cell division and multiplication
Turn on certain genes
Control Mechanisms of Endocrine Glands
Hormonal: Chemical stimulus (i.e. endocrine
glands are activated by other hormones)
Humoral/Blood-Based: Changing blood levels of
certain ions stimulate hormone release
Neural: Nerve impulses stimulate hormone release; most are under
control of the sympathetic nervous system
Location of Major Endrocrine Organs
Figure 9.3
Pituitary Gland
glandular tissue nervous tissue
blood portal system
Nervous system that hormones can drip down on
Flip and enlarge
Hormones of the Anterior Pituitary Six anterior pituitary hormones
• Two affect non-endocrine targets
• Four stimulate other endocrine glands (tropic hormones)
Characteristics of all anterior pituitary hormones
• They are proteins (or peptides)
• They act through second-messenger systems
• They are regulated by hormonal stimuli, mostly negative feedback
Hormones of the Anterior Pituitary
Increases bone and
skeletal massCauses
milk secretion in breasts
Causes follicle and sperm maturation,
ovulation and testosterone production
Stimulates thyroid
hormone secretion
Causes aldosterone,
glucocorticoid, or androgen
release
Hormones of the Posterior Pituitary
Inhibits diuresis (urine production) and
increases blood pressure
Stimulates uterine muscle contraction in labor and intercourse; causes milk
ejection
Thyroid Gland
Figure 9.6
Thyroid hormone
Controls rate of cellular respiration. All body cells are targets.
Calcitonin
Decreases blood calcium levels by causing bone calcium deposition. Made by parafollicular cells.
Consists of two lobes and a connecting isthmus
Thyroid Hormone Lack of Dietary Iodine: Goiter
Hyposecretion of thyroxine
( hypothyroidism in adults)
Hyperthyroidism (Grave's disease)
Calcitonin (Calcium deposition) Decreases blood
calcium levels by causing its deposition on bone
Antagonistic to parathyroid hormone
Produced by C (parafollicular) cells
Figure 9.9
Parathyroid Glands (Calcium removal)
Parathyroid hormone
1. Stimulates osteoclasts to remove calcium from bone
2. Stimulates the kidneys and intestine to absorb more calcium
3. Raises calcium levels in the blood
Found on posterior surface of thyroid
Adrenal Glands Two parts that act as if
separate glands
• Cortex – outer glandular region in three layers
• Medulla – inner neural tissue region
Sits on top of the kidneys
Ad-renal both mean “upon or
Epi-nephros next to the kidney”&
Adrenal Hormones and Their Locations
Adrenal Cortex
Outer portion produces mineralocorticoids like aldosterone
Middle layer produces glucocorticoids like cortisone and cortisol
Innermost layer produces androgens like estrogens and testosterone
Medulla produces catecholoamines like epinephrine and norepineprhine
Adrenal Cortex (Outer Portion)
Aldosterone release causes salt and water retention, increasing blood pressure
Hormones of the Innermost Cortex Layer Sex hormones (steroids)
• Produced in the inner layer of the adrenal cortex
• Androgens (male) and some estrogen (female) -- both produced regardless of gender
• Hypersecretion causes masculinization (regardless of gender) - most obvious effects in females
• Hyposecretion causes Addison's disease
Hormones of the Adrenal Medulla Produces two similar hormones
(catecholamines)
• Epinephrine
• Norepinephrine
These hormones prepare the body to deal with short-term stress
Sympathetic system stimulates catecholamine release in fight or flight: increased heart rate, blood pressure, blood gluocose, respiratory rate
Pancreatic Islets The pancreas is a mixed gland
The islets of the pancreas produce hormones
• These hormones are antagonists that maintain blood sugar homeostasis
Pancreatic Islets
Figure 9.13
Insulin
Allows glucose to cross plasma membranes into cells from beta cells (hypoglycemic hormone)
Glucagon
Allows glucose to enter the blood from alpha cells (hyperglycemic hormone)
Pancreatic Hormones and Blood Sugar
Figure 9.14
Pineal Gland Found on the third
ventricle of the brain
Secretes melatonin
• Helps establish the body’s wake and sleep cycles
• May have other as-yet-unsubstantiated functions
Hormones of the Ovaries Estrogens
• Produced by Graafian follicles or the placenta
• Stimulates the development of secondary female characteristics
• Matures female reproductive organs
• Helps prepare the uterus to receive a fertilized egg
• Helps maintain pregnancy
• Prepares the breasts to produce milk
Hormones of the Ovaries Progesterone
• Produced by the corpus luteum
• Acts with estrogen to bring about the menstrual cycle
• Helps in the implantation of an embryo in the uterus
Hormones of the Testes
Interstitial cells of testes are hormone-producing
Produce several androgens
Testosterone is the most important androgen
• Responsible for adult male secondary sex characteristics
• Promotes growth and maturation of male reproductive system
• Required for sperm cell production
Other Hormone-Producing Tissues and Organs Parts of the small intestine
Parts of the stomach
Thymus
Kidneys
Heart
Many other areas have scattered endocrine cells
Developmental Aspects of the Endocrine System Most endocrine organs operate smoothly until old age
Menopause is brought about by lack of efficiency of the ovaries
Problems associated with reduced estrogen are common
Growth hormone production declines with age
Many endocrine glands decrease output with age
Recommended