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Nerves, Hormones &
Homeostasis
Assessment Statements
Obj.
6.5.1
State that the nervous system consists of the central nervous system (CNS) and peripheral
nerves, and is composed of cells called neurons that carry rapid electrical impulses.
1
6.5.2
Draw and label a diagram of the structure of a motor neuron.
1
6.5.3
State that nerve impulses are conducted from receptors to the CNS by sensory neurons, within
the CNS by relay neurons, and from the CNS to effectors by motor neurons.
1
6.5.4
Define resting potential and action potential (depolarisation and repolarisation).
1
6.5.5
Explain how a nerve impulse passes along a non-myelinated neuron.
3
6.5.6
Explain the principles of synaptic transmission.
3
6.5.7
State that the endocrine system consists of glands that release hormones that are transported
in the blood.
1
6.5.8
State that homeostasis involves maintaining the internal environment between limits, including
blood pH, carbon dioxide concentration, blood glucose concentration, body temperature and
water balance.
1
6.5.9
Explain that homeostasis involves monitoring levels of variables and correcting changes in levels
by negative feedback mechanisms.
3
6.5.10
Explain the control of body temperature, including the transfer of heat in the blood, and the
roles of the hypothalamus, sweat glands, skin arterioles and shivering.
3
6.5.11
Explain the control of blood glucose concentration, including the roles of insulin, glucagon and α
and β cells.
3
6.5.12
Distinguish between type I and type II diabetes.
2
Command terms: http://i-biology.net/ibdpbio/command-terms/
Assessment statements from: Online IB Biology Subject Guide
The Motor Neuron
Diagram from: http://commons.wikimedia.org/wiki/File:Anatomy_and_physiology_unlabeled_neuron.jpg
http://bcs.whfreeman.com/thelifewire/content/chp44/4402s.swf
From McGraw Hill: http://goo.gl/tI2MD
http://www.blackwellpublishing.com/matthews/actionp.html
http://www.blackwellpublishing.com/matthews/channel.html
http://outreach.mcb.harvard.edu/animations/synaptic.swf
Insulin and Glucagon: Control of Blood
Glucose
• Two types of cells in the pancreas
– Secrete insulin and glucagon, antagonistic
hormones that help maintain glucose
homeostasis
• Glucagon
– Is produced by alpha cells
• Insulin
– Is produced by beta cells
• Maintenance of glucose homeostasis
Body cells
take up more
glucose.
Insulin
Beta cells of
pancreas are stimulated
to release insulin
into the blood.
Liver takes
up glucose
and stores it
as glycogen.
STIMULUS:
Rising blood glucose
level (for instance, after
eating a carbohydraterich meal)
Blood glucose level
declines to set point;
stimulus for insulin
release diminishes.
Homeostasis:
Blood glucose level
(about 90 mg/100 mL)
Blood glucose level
rises to set point;
stimulus for glucagon
release diminishes.
Figure 45.12
Liver breaks
down glycogen
and releases
glucose into
blood.
STIMULUS:
Dropping blood glucose
level (for instance, after
skipping a meal)
Alpha cells of pancreas
are stimulated to release
glucagon into the blood.
Glucagon
High blood glucose levels Low blood glucose levels
1. pancreas (beta) produces
1. pancreas (alpha) produces
insulin
glucagon
2. Insulin stimulates muscle
and liver to take glucose
from blood and convert to
glycogen.
2. Glucagon stimulates liver
to convert glycogen back
into glucose.
3. resulting in lowering the
glucose level in the blood.
3. releasing of glucose into
blood
• Diabetes mellitus, perhaps the best-known endocrine disorder
– Caused by a deficiency of insulin or a decreased response to insulin in
target tissues
– Is marked by elevated blood glucose levels
• Type I diabetes mellitus (insulin-dependent diabetes)
– Is an autoimmune disorder in which the immune system destroys the
beta cells of the pancreas
– Juvenile
• Type II diabetes mellitus (non-insulin-dependent diabetes)
– Is characterized either by a deficiency of insulin or, more commonly,
by reduced responsiveness of target cells due to some change in
insulin receptors
– Adults
– Body produces insulin, pancreas either cant produce enough or body
cant use it adequately (glucose cant get into cells so there is a build up
of glucose in blood)