Transcript Nervous v Endocrine

Nervous and Endocrine
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Aims:
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Must be able to compare and contrast the
nervous and endocrine systems.
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Should be able to outline how nervous and
endocrine systems work together.
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Could be able to explain examples of
nervous and endocrine control in
homeostasis.
Comparison of Nervous and
Endocrine
Feature
Nervous System
Endocrine System
Speed of Response
Faster
Slower
Length of Action
Shorter
Longer
Area of Action
Can be Smaller
Larger
Transmission of
Message
Electrical Impulse and
Neurotransmitter
(Chemical
Messenger)
Hormones (Chemical
Messenger)
Structures Involved
CNS and/ or PNS path
Neurons (sensory,
motor, inter)
Neurotransmitters
Neurohormones
Blood vessels
Blood
Glands
Blood vessels
Blood
Hormones (steroid,
polypeptide based)
Second messengers
Nerves and Hormones Together
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Homeostatic responses usually involve BOTH the nervous
system and the endocrine system.
Some neurotransmitter substances stimulate neurons, muscles
or glands
others released by different neurons inhibit neurons, muscles
or glands.
The nervous system may stimulate glands to correct a change
that disturbs homeostasis.
As the response of the gland takes effect and the balance is
restored, further action by the nervous system inhibits the
gland.
Blood Pressure
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Blood pressure is controlled by a negative feedback
mechanism.
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If the blood pressure falls - Detected by pressure
receptors in the muscle in the walls of blood vessels.
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The signal passes to the brain which responds by sending
electrical signals to the heart and blood vessels.
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Nerves also produce neurohormones and stimulate the
production of hormones that act on smooth muscle in
blood vessels.
The heart rate increases as a result of neuron and
hormone signals.
Core Body Temperature
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To maintain a stable core temperature, heat gain
must balance heat loss.
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In humans, this balance results in a core
temperature of about 37°C.
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Drop in temperature = Heat-sensing neurons in
the skin transmit information to hypothalamus.
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The brain is alerted to a potential drop in
temperature of the cells of the body.
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Messages sent out via neurons to ensure that
changes occur in the body to balance the loss of
heat.
continued…
 Nerve impulses constrict blood vessels in the skin.
– This reduces the surface area of the vessels across
which heat can be lost by radiation.
 The hypothalamus sends messages to the skeletal
muscles to contract = shivering.
 Continuous muscle contractions produce significant
amounts of heat.
 The heat produced by metabolic processes within the
body of a person contributes to the maintenance of a
stable body temperature of the person.
Blood Pressure
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Maintenance of blood pressure is also associated
with water balance:
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As water varies, blood pressure varies:
 An
increase in water brings about an
increase in blood pressure.
 An decrease in water brings about a
decrease in blood pressure.
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Kidneys are the major organ that control water
balance in vertebrates.
Blood Pressure
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Significant compounds:
– Antidiuretic hormone (ADH)
 Vasopressin
– Renin
Vasopressin:
– Produced by neurosecretory cells in the
hypothalamus.
– Very little present in blood if water is sufficient.
– If blood water concentration drops,
osomoreceptors in hypothalamus detect this
and vasopressin is released…
Blood Pressure
1.
Vasopressin flows through the axons of the
neurosecretory cells to the posterior pituitary
where it is released into the bloodstream.
2.
It is then transported to the kidneys - It
increases the permeability of distal tubules and
collecting ducts to water
3.
The amount of water reabsorbed increases and
blood water concentration returns to normal.
Activity
 Complete
flow diagrams for the
control of Body Temperature, and
blood water levels.
 Biozone
pages p82/3