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18 Cards in this Set
- Front
- Back
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Define hormone.
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Hormones are chemical signals released from endocrine glands/tissues into the bloodstream where they travel to target tissues, stimulating particular cellular actions
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What are the 2 different classes of hormone?
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1. Steroid
2. Protein |
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Define steroid hormone.
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Lipid soluble hormones derived from cholesterol. Steroid hormone receptors are found inside target cells.
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Define protein hormone.
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Water-soluble hormones (with the exception of thyroid hormone) derived from amino acids. Protein hormone receptors are located on the cell membrane of the target cells.
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Name 5 cellular actions hormones can stimulate.
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1. Opening or closing ion channels
2. Protein (enzyme) synthesis 3. Activating or deactivating enzymes 4. Secretion of cellular contents 5. Mitosis |
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What does the concentration of the hormone determine?
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The onset and duration of the target cell actions. The greater the concentration of a hormone, the greater its action at its target cells.
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What 2 things determine the concentration of a hormone?
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1. The rate of hormone release from its endocrine gland. This rate is determined by the stimuli that caused the release of the hormone in the first place.
2. The rate of inactivation and removal of the hormone from the blood. This is specific to each hormone and is based on the hormones half life. A small amount are degraded by enzymes inside the target cell. |
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What is an eicosanoid? |
Lipid derived chemicals, including leukotrines and prostaglandins, released from nearly all body cells which act locally |
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What is the stimuli for release for neural stimulation? |
Direct nerve stimulation of gland. |
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What is the stimuli for release for hormonal stimulation? |
Hormones from one endocrine gland target another endocrine gland and influence the production and release of that target glands hormones. |
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What is the stimuli for release for humoral stimulation? |
Concentration of ions/nutrients in the blood or other body fluids outside their set point range. |
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How are hormones regulated the majority of the time? |
Negative feedback mechanisms.
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How is humeral stimulation regulated? |
When the concentration of an ion/nutrient in the blood moves back into its set point range, it inhibits further release of the hormone (i.e. it ‘shuts off’ the hormone’s release). |
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How is hormonal stimulation regulated? |
When levels of a particular hormone rise, it inhibits the release of the hormone that triggered its release in the first place. |
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How is neural stimulation regulated? |
When nerve stimulation of an endocrine gland stops, it inhibits further release of that hormone (i.e. nerve stimulation works like an 'on-off' switch). |
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Name the 2 exceptions to the negative feedback regulation of hormone release. |
1. Hypothalamic - anterior pituitary regulation 2. Nervous system over ride. |
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What is hypothalamic - anterior pituitary regulation? |
The hypothalamus secretes a group of regulating hormones that target the anterior pituitary gland. These regulating hormones may either be releasing/stimulating hormones or inhibiting hormones. |
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Describe an example of nervous system override. |
The level of glucose in the blood is maintained in its set point range by two pancreatic hormones whose release are regulated via negative feedback of glucose concentrations in the blood. However, sympathetic nervous system activity can override this control, causing an increase in blood glucose levels beyond its set point range, when required- such as when stressed or being highly active. |
