Ch 32: Internal Environment: Organization & Regulation Flashcards
Define homeostasis
Maintenance of relatively constant internal conditions in the face of a changing external environment; Homeostasis is not a static, unchanging state, but rather a dynamic equilibrium
List physiological parameters that are regulated within the body
- Temperature
- Heart rate
- Blood pressure
- Blood sugar
- Blood pH
- Water and ion concentrations
What is a feedback loop?
A feedback loop isa biological occurrence where the output of a system amplifies the system (positive feedback) or inhibits the system (negative feedback). Feedback loops are important because they allow living organisms to maintain homeostasis.
Describe the components of a feedback loop
Components:
- Sensor: monitors a physiological variable and relays information about the variable to control centers
- Control center: monitors information from the sensors and generate responses to deviations from the set point
- Effector: carries out the responses of the control center to return the variable to a homeostatic range
Contrast Negative and Positive Feedback
- Negative Feedback Loops
- Output shuts off or counteracts the original stimulus
- Cycle allows to return the variable to the set point / homeostatic level
- Positive Feedback Loops
- Output enhances or accelerates the original stimulus
- Cycle ends when the stimulus that initiated the feedback loop is removed
Give examples of negative and positive feedback
Example of a Negative Feedback: Temperature Regulation
Example of Positive Feedback: Childbirth and the role of Oxytocin
What are the types of chemical signals?
- Paracrine
- Autocrine
- Hormones
- Neurotransmitters
- Pheromones
Distinguish between different types of chemical signals
Paracrine - Limited to local area; In extracellular fluid
Autocrine - Limited to cell that produces the signal; In extracellular fluid
Hormones - Targets distant organs and tissues; In bloodstream
Neurotransmitters - Very localized- Targets post-synaptic cell; Across synapse
Pheromones - Act on a different individual of the same species; External environment
Compare and contrast communication in the nervous and endocrine systems
- Nervous system
- Electrical signals & neurotransmitters
- Faster transmission, short-lived response
- More localized response
- to direct immediate & rapid responses to the environment
- Endocrine system
- Chemical signals: hormones
- Slower, can be short or long lived
- Response can be widespread
- to coordinate gradual changes that affect the entire body
Define what an hormone is
Hormones are chemical signals that are secreted by endocrine cells or glands in one area of the body and travel through the bloodstream to act on target cells through receptors. They influence the actions of target cells elsewhere in body.
What are the three classes of hormones?
- Amine Hormones
- Peptide Hormones
- Steroid Hormones
Distinguish between different classes of hormones
Amine hormones - Hormones derived from the modification of amino acids are referred to as amine hormones; hydrophilic
Peptide hormones - Peptide hormones consist of short chains of amino acids; hydrophilic
Steroid hormones - Steroid hormones area group of hormones derived from cholesterol that act as chemical messengers in the body; hydrophobic
Contrast the receptor location and overall effects on the target cell of steroid hormones vs. amine/ peptide hormones
- Peptide and amine hormones are hydrophilic and bind to cell-membrane receptors activating second messenger pathways, which change the metabolic state or can affect gene expression of the target cell.
- Steroid hormones are hydrophobic and diffuse into the target cell, where they bind a cytoplasmic or nuclear receptor that allows them to act as transcription factors to alter the gene expression of the cell.
Explain why only target cells respond to a chemical signal, while other cells do not
Target cells have proteins called receptors, which bind to signaling molecules and cause a response. Signaling molecules that bind to receptors are called ligands. Ligands and receptors are specific for each other;a receptor will typically bind only to its specific ligand.
Recognize that hormonal signals are amplified
The effect of a hormone is amplified as the signaling pathway progresses.
