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LU9: Hormones & Endocrinology (51494 & 54020) (Major Vertebrate…
LU9: Hormones & Endocrinology (51494 & 54020)
Hormone
A
chemical signal
secreted into
body fluid, & communicates regulatory messages within the body
Only
target cells
equipped with specific receptor
will respond to the particular hormone
5 Regulatory Functions:
Metabolism
Growth
Development
Maturation
Reproduction
Classes of Hormones
1)
Protein-based Hormones
Polypeptides
-
small proteins (insulin, ADH)
Glycoproteins
-
large proteins + carbohydrate (FSH, LH)
Amines
-
Modified amino acids (epinephrine aka adrenaline, melatonin)
Hydrophilic & not lipid soluble
-
CANNOT
diffuse across membrane
Trigger secondary messenger pathway
:
Transmits
signal
across membrane
=
Signal Transduction
Activates a series of secondary messengers
=
Multi-step Cascade
Activate Cellular Response
-
Enzyme action, uptake / secretion of molecules
2)
Lipid-based Hormones
Steroids
-
Modified cholesterol (sex hormones, aldosterone)
Eicosanoids
-
Prostaglandins
Lipid-soluble
-
diffuse across membrane & enter cells
Activate genes
-
synthesis of new proteins
Bind to receptor proteins in nucleus
& bind to DNA as
transcription factors
Bind to receptor proteins in cytoplasm
-
hormone-receptor complex moves into nucleus
Endocrine System
A system of
ductless glands
Each gland contains specialized cells that
synthesizes Hormones
Endocrine
vs.
Exocrine
Endocrine Gland
Ductless
Bloodstream
Hormone
Exocrine Gland
Ducts
Lumen & Surfaces
e.g.: Enzyme & sweat
Endocrine Signaling
vs.
Nervous Signaling
Endocrine System
Signal Type =
Chemical (hormone)
Transfer = Blood circulation
to whole body
Action =
Slow, long-lasting response
Nervous System
Signal Type =
Electrical + Chemical
(nerve impulse + neurotransmitter)
Transfer =
Neuron network to target cells
Action =
Fast, short-lasting response
Major Vertebrate Hormones
Pituitary Gland
Anterior Lobe
1)
Growth Hormone (GH)
- Targets
many organs
Stimulates growth by promoting protein synthesis & fat breakdown for energy metabolism
2)
Adrenocorticotropic Hormone (ACTH)
- Targets
Adrenal Cortex
Stimulates secretion of adrenal cortical hormones (e.g. cortisol)
3)
Thyroid-stimulating Hormone (TSH)
- Targets
Thyroid gland
Stimulates thyroxine secretion
4)
Lutenizing Hormone (LH)
- Targets
gonads
Female:
Stimulates ovulation & corpus luteum formation
Male:
Stimulates secretion of testosterone
5)
Follicle-stimulating Hormone (FSH)
- Targets
gonads
Female:
Stimulates development of ovarian follicles
Male:
Stimulates spermatogenesis
6)
Prolactin (PRL)
- Targets
mammary glands
Stimulates milk production
7)
Melanocyte-stimulating Hormone (MSH)
- Targets
skin
Reptiles & amphibians:
Stimulates color change
Mammals:
Unknown function
Posterior Lobe
i)
Antidiuretic Hormone
- Targets
kidneys
Stimulates reabsorption of water; conserves water
ii)
Oxytocin
- Targets
Uterus & Mammary glands
Uterus:
Stimulates contraction
Mammary glands:
Stimulates milk ejection
Thyroid Gland
Thyroxine (Thyroid Hormone)
- Targets
Most cells
Stimulates metabolic rate; essential for normal growth & development
Calcitonin
- Targets
Bone
Lowers blood calcium level by inhibiting calcium loss from bone
Parathyroid Glands
Parathyroid Hormone
- Targets
Bone, kidneys & digestive tracts
Raises blood calcium level by stimulating bone; Stimulates calcium reabsorption; Activates vitamin D
Adrenal Medulla
Epinephrine
(adrenaline) &
Norepinephrine
(noradrenaline) - Targets
smooth cells, cardiac muscle, blood vessels
Initiate stress responses; raises heart rate, blood pressure, metabolic rate, dilate blood vessels; mobilize fat; raise blood glucose level
Adrenal Cortex
i)
Aldosterone
- Targets
kidney tubules
Maintains proper balance of Na+ & K+ ions
ii)
Cortisol
- Targets
many organs
Adaptation to long-term stress; raises blood glucose level; mobilizes fat
Pancreas
i)
Insulin
- Targets
liver, skeletal muscles, adipose tissue
Lowers blood glucose level; stimulates
storage
of glycogen in liver
ii)
Glucagon
- Targets
liver, adipose tissue
Raises blood glucose level; stimulates
breakdown
of glycogen in liver
Ovary
Estradiol
General:
Stimulates development of secondary sex characteristics in females
Female Reproductive Structures:
Stimulates growth of sex organs at puberty & monthly preparation of uterus for pregnancy
Progesterone
- Targets
uterus & mammary glands
Uterus:
Completes preparation for pregnancy
Mammary glands:
Stimulates development
Testis
Testosterone
- Targets
many organs
Stimulates development of secondary sex characteristics in males & growth spurt at puberty
Pineal Gland
Melatonin
- Targets
Male reproductive structures, gonads, pigment cells
Male reproductive structures:
Stimulates development of sex organs; Stimulates spermatogenesis
Gonads, pigment cells:
Function not well understood; influences pigmentation in some vertebrates; may control biorhythyms in some animals; may influence onset of puberty in humans
Hormone Regulation in Insect Development
Neurosecretory cells in brain - Produces
i) brain hormone (BH)
BH stimulates Protoracic gland - to secrete
ii) ecdysone
- induces
Molting
in moth
iii)
Juvenile Hormone (JH)
: secreted by corpora allata (a pair of small glands) -
promotes
retention
of larval characteristic
JH
balances the effect of
BH & Ecdysone
Control & Feedback
a)
Hormonal Stimulation
Endocrine glands - activared by other
hormones
b)
Humoral Stimulation
Changing blood levels of certain
ions
stimulate hormone release
c)
Neural Stimulation
Nerve impulses
stimulate hormone release
;
Most are under control of
sympathetic nervous system
Endocrine & Nervous System Links
Hypothalamus
("master control center") -
nervous system
Receives info from nerves around body about internal conditions
Regulates hormones release from pituitary
Pituitary gland
("master gland") -
endocrine system
Secretes broad range of hormones regulating other glands
Hormone Feedback Mechanisms
Negative Feedback
Stimulus triggers control mechanism that
INHIBITS
further change
- body temperature & sugar metabolism
Positive Feedback
Stimulus triggers control mechanism that
AMPLIFIES
effect - Lactation & labor contractions
Hormone Disorders
Unusual level of hormones in bloodstream
Caused by:
Endocrine disease / Drugs interaction
3 Categories of Endocrine Disease
:
i.
Endocrine gland
Hyposecretion
- leads to
hormone deficiency
ii.
Endocrine gland
Hypersecretion
- leads to
hormone excess
iii.
Tumors
(
benign/malignant)
of endocrine glands*
Hormonal Imbalance
Hyperthyroidism
Hypercortisolism
(
e.g. - Cushing's Syndrome
)
Example of Hormone Disorder:
Goiter
- due to
iron deficiency
- thyroid enlarges as it tries to produce thyroxine