Endocrine System Flashcards
Main Functions
- Water balance
- Uterine contractions and milk release
- Growth, metabolism, and tissue maturation
- Ion regulation
- Heart rate and blood pressure regulation
- Blood glucose control
- Immune system regulation
- Reproductive functions control
ligands aka chemical signals
molecules released from one location that move to another location to produce a response
Intracellular chemical signals
produced in one part of a cell, such as the cell membrane, and travel to another part of the same cell and bind to receptors, either in the cytoplasm or in the nucleus
Intercellular chemical signals
released from one cell, are carried in the intercellular fluid, and bind to receptors that are found in other cells, but usually not in all cells of the body
Autocrine chemical signals
intercellular
chemical signals are released by cells and have a local effect on the same cell type. Example: prostaglandin-like chemicals that are secreted in response to inflammation
Paracrine chemical signals
intercellular
chemical signals are released by cells and have effects on other cell types. Example: somatostatin, secreted by the pancreas, inhibits the release of insulin by other cells in the pancreas
Neuromodulators and neurotransmitters
intercelluar
chemical signals are secreted by nerve cells and aid the nervous system. Example: acetylcholine produced during stressful encounters
Pheromones
intercellular
chemical signals are secreted into the environment and modify the behavior and physiology of other individuals. Example: those produced by women can influence the length of the menstrual cycle of other women
Receptors
proteins or glycoproteins chemical signal binds to to produce a response
specificity
only certain chemical signals can bind to a receptor sit e based on shape and chemical characteristics
Types of receptor molecules that respond to intercellular chemical signal
intracellular
membrane-bound
Intracellular receptors
receptors are located in either the cytoplasm or the nucleus of the cell. Signals diffuse across the cell membrane and bind to the receptor sites on intracellular receptors
Membrane-bound receptors
receptors extend across the cell membrane, with their receptor sites on the outer surface of the cell membrane. They respond to intercellular chemical signals that are large, water-soluble molecules that do not diffuse across the cell membrane
Receptors that directly alter membrane permeability
For example, acetylcholine (adrenaline) from nerve fiber endings binds to receptors that are part of the membrane channels for sodium ions
Receptors and G proteins
G proteins (guanine nucleotide-binding proteins) are found on the inner surface of the plasma membrane and function as receptors of hormones. For example, chemical signals include cyclic adenosine monophosphate glycerol and inositol triphosphate that bind to receptor molecules in the cell and alter their activity to produce a response
Receptors that alter the activity of enzymes
For example, increasing the activity of an enzyme responsible for the breakdown of glycogen into glucose makes glucose available as an energy source for muscle contractions
term endocrine
implies that intercellular chemical signals are produced in and secreted from endocrine glands
Hormones
produced (in minute amounts) by a collection of cells to influence the activity of those tissues in a specific way.
For example, neurohormones are hormones secreted from cells of the nervous system.
target tissues
Hormones are distributed in the blood to all parts of the body, but only certain tissues
Negative-feedback mechanisms
controls secretion of hormones
keep the body functioning within a narrow range of values consistent with life
Ways to control secretion of hormones
Blood levels of chemicals
Hormones
Nervous System
Blood Chemical Levels
secretion of some hormones is directly controlled by the blood levels of certain chemicals. For example, blood glucose levels control insulin secretion
Hormones
secretion of some hormones is controlled by other hormones. For example, hormones from the pituitary gland act on the ovaries and the testes, causing those organs to secrete sex hormones
Nervous system
hormones are controlled by the nervous system. For example, epinephrine is released from the adrenal medulla as a result of nervous system stimulation
cascade effect
few intercellular chemical signals can bind to their membrane-bound receptors, and each activated receptor can produce many intracellular chemical signal molecules that rapidly activate many specific enzymes inside the cell
