Download Endocrine System

Endocrine System
Chapter 45
What you need to know!
• Two ways hormones affect target organs.
• The secretion, target, action, and
regulation of at least three hormones.
• An illustration of both positive and negative
feedback in the regulation of homeostasis
by hormones.
Endocrine
• System produces
hormones that regulate
homeostasis,
reproduction,
development, and
behavior
• Master organs:
• Hypothalamus
• Pituitary gland
• Receive sensory input
from receptors
throughout the body
Hormones
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Transported by blood
Minute amounts needed
Are steroids, peptides, or amino acids
Work by either:
1. Binding to cell-surface receptors causing a signal
transduction pathway (cascade of chemical events
in response to stimulus) or
2. Diffusing across the cell membrane and binding to
intracellular receptors which then act as
transcription factors to activate specific genes
Blood Glucose Example
• Stable at 90mg/100ml
• Regulated by pancreas
• Pancreas serves multiple functions: digestions and blood
sugar regulation
• Glucagon is released by alpha-cells in response to low
blood glucose levels
• Insulin is released by beta-cells in response to high
blood glucose levels
Blood Glucose Example
• After eating food blood glucose levels in the body rise
leading to the release of insulin by the beta cells; this
stimulates the liver to build up glycogen (animal starch)
storage and other body cells to absorb glucose
• After exercise or starvation blood glucose levels drop,
alpha-cells release glucagon; this stimulates liver to
break down glycogen into glucose
Blood Glucose
Example
Diabetes
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Type 1 (juvenile)
Autoimmune destruction of beta cells
Type 2 (adult onset)
Exhaustion of beta cells due to high lifelong high
glycemic index diet
Stress (Fight or Flight) Response
• Regulated by hypothalamus/adrenal glands
• Stress activates the hypothalamus
• Fast reply: nerve connection to adrenal medulla
activates adrenalin (epinephrine) release
Adrenalin Action:
• Glycogen breakdown
• Blood glucose increase
• Heart rate increase
• Breathing rate increase
• Lower blood flow to intestines (vasoconstriction)
• Higher blood flow to muscles (vasodilation)
Long Term Stress
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Pituitary gland releases ACTH
Make adrenal cortex release corticoids
Corticoid action includes:
Increase in blood volume
Proteins/fat converted into glucose (rise in glucose
levels)
• Suppresses immune system
• Antinflamatory response