BPK 105 Study Guide - Midterm Guide: Thyroid, Autocrine Signalling, Extracellular Fluid
27 Apr 2018
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Module 6 - Objectives - Part 1
● Differentiate between the four classifications of chemical messengers, providing
examples of each.
1. Autocrine chemical messengers.
-stimulates the cell that originally secreted it, and sometimes nearby cells of the
same type.
- Good examples of autocrine chemical messengers are those secreted by white blood
cells during an infection. Several types of white blood cells can stimulate their own
replication so that the total number of white blood cells increases rapidly.
2. Paracrine chemical messengers.
- act locally on nearby cells.
-secreted by one cell type into the extracellular fluid and affect surrounding cells of a
different type.
- Ex. histamine, released by certain white blood cells during allergic reactions. Histamine
stimulates vasodilation in nearby blood vessels.
3. Neurotransmitters.
-secreted by neurons that activate an adjacent cell, whether it is another neuron, a
muscle cell, or a glandular cell.
- secreted into a synaptic cleft, rather than into the bloodstream.
- Therefore, in the strictest sense neurotransmitters are paracrine messengers.
4. Endocrine chemical messengers.
- secreted into the bloodstream by certain glands and cells, which together constitute the
endocrine system.
-affect cells that are distant from their source.
- Describe the importance of the terms receptor site specificity and target tissue.
- Hormones exert their actions by binding to proteins called receptors.
- A hormone can stimulate only the cells that have the receptor for that hormone.
- The portion of each receptor molecule where a hormone binds is called a receptor site
- shape and chemical characteristics of each receptor site allow only a specific type of
hormone to bind to it.
- tendency for each type of hormone to bind to one type of receptor, and not to others, is
called specificity (figure 10.6).
- Ex. insulin binds to insulin receptors, but not to receptors for thyroid hormones. However,
some hormones, such as epinephrine, can bind to a “family” of receptors that are
structurally similar.
Document Summary
Differentiate between the four classifications of chemical messengers, providing examples of each: autocrine chemical messengers. stimulates the cell that originally secreted it , and sometimes nearby cells of the same type . Good examples of autocrine chemical messengers are those secreted by white blood cells during an infection. Ex. histamine, released by certain white blood cells during allergic reactions. Histamine stimulates vasodilation in nearby blood vessels: neurotransmitters. secreted by neurons that activate an adjacent cell, whether it is another neuron, a muscle cell, or a glandular cell. secreted into a synaptic cleft, rather than into the bloodstream. Therefore, in the strictest sense neurotransmitters are paracrine messengers: endocrine chemical messengers. secreted into the bloodstream by certain glands and cells, which together constitute the endocrine system. affect cells that are distant from their source . Describe the importance of the terms receptor site specificity and target tissue. Hormones exert their actions by binding to proteins called receptors.
