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Cells
• All organisms are made up of cells
• Cells have particular properties
– Discrete Boundaries – each cell has a
membrane
– Metabolism – each cell uses energy and
creates waste
– Replication
– Function
– Communication
Hormones
• Provide cell communication
• Indirect communication – signaling (like
radio). This is called endocrine activity.
• Direct communication. This is called
paracrine activity.
Cell Properties
• Each cell (except sex cells) contains
identical DNA.
• Every cell has a complete set of
instructions on how to work like any other
cell.
• Redundant
• Why don’t all cells operate like all other
cells?
Cell Communication
• Certain cells have receptors so that they
can receive signals from proteins. Like
puzzle pieces.
• Hormones are proteins – each with a
particular shape.
Thyroid Function
Thyroid gland (T3 and T4) controls cell
metabolism, i.e., how the cell uses energy.
• Hypothalamus monitors the secretions of the
thyroid gland (T3 and T4). If levels aren’t
correct, then produces TRH.
• Pituitary gland (area called the
adenohypophysis) has TRH receptors. TRH
signals pituitary to produce TSH.
• Thyroid gland has TSH receptors, signaling it
to produce T3 and T4.
Hypothalamus
TRH
T3, T4
Negative Feedback
Thyroid
Pituitary
TSH
Thyroid Function
Diabetes
• Cells produce energy from glucose
• Insulin allows glucose to get from the
bloodstream into the cells
• Insulin is produced by the pancreas (Islets
of Langerhaus)
• When blood sugar increases, this causes
the pancreas to secrete insulin
• Diabetes – when body can’t make and/or
use insulin
Diabetes
• Type I – Juvenile diabetes: Immune
system attacks and destroys insulin
producing cells of the pancreas
• Type II – Adult onset: Cells don’t respond
to insulin, insulin resistance
• Without glucose, cells burn fat for energy
which creates ketones.
• When ketones build up in cells, they can
poison cells.
Diabetes
• Insulin Shock – too much insulin
• Neurons (i.e., your brain) also depend on
glucose as their source of energy.
• Neurons don’t need insulin to absorb glucose
• When too much insulin, then cells absorb all the
available glucose, leaving none for the neurons.
• Dizziness, speech impairment, loss of
consciousness – hypoglycemic coma