unit iv: regulation endocrine system
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Unit IV: Regulation Endocrine System. Chapter 16 pp. 541-551; 560. Overview of Cell Communications. Mechanisms: gap junctions pores in cell membrane allow signaling chemicals to move from cell to cell neurotransmitters released from neurons to travel across gap to 2 nd cell - PowerPoint PPT PresentationTRANSCRIPT
Unit IV: RegulationEndocrine System
Chapter 16
pp. 541-551; 560
Overview of Cell Communications
Mechanisms:
– gap junctions
• pores in cell membrane allow signaling chemicals to move from cell to cell
– neurotransmitters
• released from neurons to travel across gap to 2nd cell
– paracrine (local) hormones
• secreted into tissue fluids to affect nearby cells
– hormones
• chemical messengers that travel in the bloodstream that exert an influence on target cells
Endocrine Glands
Endocrine vs. Exocrine Glands
• Exocrine glands
– ducts carry secretion to a surface or organ cavity
– extracellular effects
• Endocrine glands
– no ducts, hormones
– intracellular effects
cAMP as 2nd messenger system Ca2+ as 2nd messenger
Hormone Hormone Hormone
G proteinactivated
G proteinactivated
G proteinactivated
cAMP cAMP AMPATP
Opens ionchannels
Activatesenzymes
Reducedenzymeactivity Activates
enzymes
Ca2+
Ca2+Ca2+
Ca2+
Calmodulin
Hormone
Proteinreceptor
G protein(inactive)
G proteinactivated
Endocrine Glands
• Receptors located on cell membrane• Alters activity of enzymes
Endocrine Glands
Nuclearpore
Binds to DNA
Gene activation
Transcription
Receptor
Translation
Alteration of cellularstructure or activity
Target cell response
Diffusion
CYTOPLASM
Receptor
Steroid hormoneThyroid hormone
Target cell response
Alteration of activity
Translation
Transcription
Gene activation
Binds to DNA
Receptor
Receptor
Transport
↑ATPproduction
• Receptors located in ICF• Alters activity of specific genes
Neuron
Nerve impulse
Neurotransmitter
Target cells
Target cells
(b) Endocrine system
(a) Nervous systemEndocrinecells
Hormone inbloodstream
Nervous vs. Endocrine Systems1. Communication
– nervous - electrical– endocrine - only chemical
2. Speed and persistence of response– nervous - reacts quickly; stops quickly– endocrine - reacts slowly
3. Adaptation to long-term stimuli– nervous - response declines– endocrine - response persists
4. Area of effect– nervous - targeted and specific– endocrine - general, widespread effects
Portal vessels
Hypophyseal Portal System
Supraopticnuclei
Paraventricularnuclei
Neurosecretoryneurons
HYPOTHALAMUS
Infundibulum
Posterior lobe ofpituitary gland
Anterior lobe ofpituitary gland
Hypophyseal veins
MEDIAN
EMINENCE
Hypothalamus
• Shaped like a flattened funnel, forms floor and walls of third ventricle of brain
• Regulates primitive functions from water balance to sex drive
• Many functions carried out by pituitary gland– Hypophyseal portal system– Hypothalamo-hypophyseal tract
Hypothalamic Hormones
•Transported to posterior lobe of pituitary–Antidiuretic hormone (ADH)–Oxytocin (OXT)
•Stimulate the anterior pituitary to release its hormones–Thyrotropin-releasing hormone release of TSH & PRL–Corticotropin-releasing hormone release of ACTH–Gonadotropin-releasing hormone release of FSH & LH–Growth hormone-releasing hormone release of GH
•Inhibit the anterior pituitary from releasing its hormones–Prolactin-inhibiting factor inhibits release of PRL–Somatostatin /GH-IH inhibits release of GH & TSH
HypothalamusIndirect Control through Releaseof Regulatory Hormones
Direct Releaseof Hormones
Sensorystimulation
Osmoreceptorstimulation
Posterior lobeof pituitary gland
Kidneys
Males: Smoothmuscle in ductusdeferens andprostate gland
Females: Uterinesmooth muscle andmammary glands
Melanocytes (uncertainsignificance in healthyadults)Ovaries
of femaleTestesof maleMammary
glands
Bone, muscle,other tissues
Thyroidgland
Adrenalglands
Adrenal cortex Anterior lobe ofpituitary gland
ACTH
TSH GH
PRLFSH LH MSH
OXT
ADH
Liver
Somatomedins
Corticosteroids
Thyroidhormones
Inhibin Testosterone Estrogen Progesterone Inhibin
Corticotropin-releasinghormone(CRH)
Thyrotropin-releasinghormone
(TRH)
Growthhormone-releasinghormone(GH-RH)
Prolactin-inhibitinghormone
(PIH)
Gonadotropin-releasinghormone(GnRH)
Pituitary/Hypophysis Hormones
Stimulation
Inhibition
Stimulates growth of skeletal muscle,cartilage, and many other tissues
Epithelia,adipose tissue,liver
Anteriorlobe
GH
GH-IH
GH-RH
Liver
Somatomedins
Growth Hormone (Somatotropin)
Promotes tissue growth– stimulates liver to produce IGF-I and II
• protein synthesis – proteins synthesized– enhances amino acid transport
into cells• lipid metabolism
– stimulates FFA and glycerol release from adipocytes
• CHO metabolism– glucose sparing effect
• Electrolyte balance– promotes Na+, K+, Cl- retention,
Ca 2+ absorption
Growth Hormone and Aging
• Childhood and adolescence
– bone, cartilage and muscle growth
– Stimulates growth at epiphyseal plates
• Adulthood
– increase osteoblastic activity and appositional growth
– aging of tissues
• Levels of GH
– higher during deep sleep, after vigorous exercise, after high protein meals
– lower after high CHO meals
Pineal Gland
• Peak secretion ages 1-5; by puberty 75% lower
• Produces serotonin by day, converts it to melatonin at night
• May regulate timing of puberty in humans
• Melatonin in SAD & PMS by phototherapy
Thymus
• Involution after puberty
• Regulate development and activation of T-lymphocytes– Thymopoietin, thymosins, and thymulin