Download Unit IV: Regulation Endocrine System

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 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
Endocrine Glands
• Receptors located on cell membrane
• Alters activity of enzymes
Hormone
Protein
receptor
G protein
(inactive)
G protein
activated
Ca2+ as 2nd messenger
cAMP as 2nd messenger system
Ca2+
Hormone
Hormone
G protein
activated
G protein
activated
cAMP
Opens ion
channels
Hormone
ATP
Activates
enzymes
cAMP
G protein
activated
AMP
Reduced
enzyme
activity
Ca2+
Ca2+
Ca2+
Calmodulin
Activates
enzymes
Endocrine Glands
• Receptors located in ICF
• Alters activity of specific genes
Thyroid hormone
Steroid hormone
Transport
Diffusion
Target cell response
Target cell response
Alteration of cellular
structure or activity
↑ATP
production
Receptor
Alteration
of activity
Translation
Receptor
Translation
CYTOPLASM
Transcription
Transcription
Receptor
Receptor
Nuclear
pore
Gene
activation
Binds to DNA
Gene
activation
Binds to DNA
Nervous vs. Endocrine Systems
1. Communication
– nervous - electrical
– endocrine - only chemical
2. Speed and persistence of response
– nervous - reacts quickly; stops quickly
– endocrine - reacts slowly
Neurotransmitter
Nerve impulse
Neuron
3. Adaptation to long-term stimuli (a) Nervous system
– nervous - response declines
– endocrine - response persists
4. Area of effect
(b) Endocrine system
– nervous - targeted and specific
– endocrine - general, widespread effects
Target cells
Endocrine Target cells
cells
Hormone in
bloodstream
Hypothalamus
• Shaped like a flattened funnel,
forms floor and walls of third
ventricle of brain
Hypophyseal
Supraoptic Paraventricular
nuclei
nuclei
Neurosecretory
neurons
HYPOTHALAMUS
Portal System
• Regulates primitive functions from
water balance to sex drive
• Many functions carried out by
Portal vessels
pituitary gland
– Hypophyseal portal system
– Hypothalamo-hypophyseal tract
Infundibulum
Posterior lobe of
pituitary gland
Anterior lobe of
pituitary gland
Hypophyseal veins
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
Pituitary/Hypophysis Hormones
Hypothalamus
Indirect Control through Release
of Regulatory Hormones
Corticotropinreleasing
hormone
(CRH)
Growth
hormonereleasing
hormone
(GH-RH)
Thyrotropinreleasing
hormone
(TRH)
Adrenal cortex
Gonadotropinreleasing
hormone
(GnRH)
Prolactininhibiting
hormone
(PIH)
Anterior lobe of
pituitary gland
GH
TSH
Liver
Thyroid
gland
PRL
Kidneys
OXT
FSH
MSH
LH
Somatomedins
Corticosteroids
Bone, muscle,
other tissues
Thyroid
hormones
Mammary
glands
Osmoreceptor
stimulation
Posterior lobe
of pituitary gland
ADH
ACTH
Adrenal
glands
Direct Release
of Hormones
Sensory
stimulation
Testes
of male
Inhibin Testosterone
Ovaries
of female
Estrogen Progesterone
Males: Smooth
muscle in ductus
deferens and
prostate gland
Females: Uterine
smooth muscle and
mammary glands
Melanocytes (uncertain
significance in healthy
adults)
Inhibin
Growth Hormone (Somatotropin)
Promotes tissue growth
– stimulates liver to produce IGF-I and II
Stimulation
GH-IH
• protein synthesis
GH-RH
Inhibition
– proteins synthesized
– enhances amino acid transport
into cells
Anterior
• lipid metabolism
lobe
– stimulates FFA and glycerol
Epithelia,
release from adipocytes
adipose tissue,
GH
liver
• CHO metabolism
Liver
– glucose sparing effect
• Electrolyte balance
Somatomedins
– promotes Na+, K+, Cl- retention,
Stimulates growth of skeletal muscle,
Ca 2+ absorption
cartilage, and many other tissues
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