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Unit II Lesson 4
Distant Connections:
The Endocrine Glands
The Endocrine Glands
• Are glands that secrete chemicals
called hormones directly into the
bloodstream
• Endocrine communication is slower
than synaptic communication
– Hormones
• Chemicals released into the bloodstream
by endocrine glands
Figure 2.9 The Endocrine Glands
The endocrine glands secrete hormones directly into the bloodstream, which carries them to
organs in the body, such as the heart, pancreas, and sex organs.
Pituitary gland
• Located in the brain
• Secretes human growth hormone
• Influences all other hormonesecreting glands (also known as
the master gland)
Pineal gland
• Located near the base of the
cerebrum
• Secretes melatonin
– Helps track day length (Seasons)
– Influences seasonal behaviors like
breeding and molting
• Regulates sleep-wake cycle
Thyroid gland
• Found in the neck
• Regulates growth and metabolism
• Thyroxin hormone regulates
metabolism
– How fast body burns available energy
Pancreas
• Controls the levels of sugar in the
blood
• Secretes insulin and glucagons
– Too little then diabetes
– Too much then hypoglycemia
Gonads
• Sex glands
• Secrete hormones that regulate
sexual behavior and reproduction
– Ovaries - female gonads
– Testes - male gonads
• Keep in mind: Humans are not like
animals in that the brain is the
master of their sexual system
– Psychological factors: Attractiveness
Adrenal glands
• Located on top of each kidney
• Secrete over 30 different
hormones
– Deals with stress
– Regulates salt intake
– Provides secondary source of sex
hormones during adolescence
Physiological Stressors
• Autonomic nervous system:
– Sympathetic system
• Responds to stressful events
– Parasympathetic system
• Restores body to normal functioning after stress
• General Adaptation Syndrome (GAS)
– Three stages:
• Alarm
– Sympathetic arousal
– Adrenal glands release hormones
• Resistance
– Continues until stressor ends
– May experience insensitivity to pain
• Exhaustion
– Can lead to formation of stress related illness
– Parasympathetic system attempts restoration of system
Stress
• Psychoneuroimmunology
– The study of the effects of psychological
factors on the body’s disease-fighting system
– Stress reducing benefits of laughter
• Laughing significantly increases the level of healthprotecting beta-endorphins
• Looking forward to a positive laughing experience
can decrease levels of hormones such as cortisol
Stress and the Immune System
• Immune system
– Cells, organs, and chemicals of the body
– Responds to diseases, infections, and injuries
– During stress, chemicals activate receptor sites
on the vagus nerve
– Positive effects of stress on the immune system
work when stress is not continual or chronic
– Natural killer cell
• Responsible for suppressing viruses
and destroying tumor cells
Stress and the Immune System
(2)
• Heart Disease
– Stress puts people at a higher risk for heart
attacks and strokes
• Liver does not have a chance to clear the fat and
cholesterol from the bloodstream
• Can lead to consumption of “comfort foods” which
are bad for health
Stress and the Immune System
(3)
• Diabetes
– Type 1: associated with pancreas not secreting enough
insulin
– Type 2: associated with excessive weight gain
• Cancer
– Stress causes the release of adrenaline and noradrenalin
• Can cause mistakes in instructions given by genes to cells of
the body
• Other health issues
– Chronic stress linked to changes in immune system’s
ability to fight off inflammation
– Children in stressed families appear to have more
fevers