endocrine Flashcards
There exists two primary signaling mechanisms
endocrine system
nervous system
Endocrine system signaling style
Signaling by hormones
Chemical signals that travel via circulatory system (blood)
Only cells with specific receptors will respond to hormones
Relatively slow responses
A small number of hormone producing cells can control a large number of response generating cells
Hormone
secreted molecule that circulates throughout the body and stimulates specific cells
Hormones reach all cells in a body but only elicit a response in specific target cells
Nervous system
Signaling by neurons
Nerves make direct contact with target cells
Fewer target response generating cells are signaled than with hormones
Faster signaling than with hormones
Neuroendocrine signaling
Nerve cell doesn’t release neurotransmitters to a postsynaptic neuron, but releases it to a capillary bed that is then taken up by the circulatory system
Neurohormones diffuse into the bloodstream originating from a neurosecretory cell, and trigger responses in target cells anywhere in the body (synaptic signaling meets endocrine signaling)
. One function of endocrine signaling is to maintain homeostasis. How is this done
Hormones regulate properties that include blood pressure and volume, energy metabolism and allocation, and solute concentrations in body fluids
Many types of cells produce and secrete local regulators which are
molecules that act over short distances, reach their target cells solely by diffusion, and act on their target cells within seconds or even milliseconds
examples of this are
Paracrine signaling
Autocrine signaling
Paracrine signaling
Target cells lie near the secreting cell
Secreted molecules diffuse locally and trigger a response in neighboring cells
Autocrine signaling
Secreted molecules diffuse locally and trigger a response in the cells that secrete them
Secreting cells themselves are the target cells
Prostaglandins
Local regulators that are produced throughout the body and have diverse functions
Promote inflammation and the sensation of pain in response to injury for immune system
Synaptic signaling
Neurotransmitters diffuse across synapses and trigger responses in target tissues
Synaptic signaling is central to sensation, memory, cognition, and movement
Synaptic signaling vs neuroendocrine signaling
Synaptic signalling secretes neurotransmitters and neuroendocrine signaling secretes neurohormones which diffuse from nerve cell endings into the bloodstream
What kind of molecules make up hormones? Four main classes
Amino acid derived hormones (amines)
Polypeptide hormones
Eicosanoids
Steroid hormones
Amino acid derived hormones
Amines
Most are chemical derivatives of Tyrosine
Examples
Epinephrine and norepinephrine
Thyroxine
Epinephrine and norepinephrine
Water soluble hormone involved in stress response
Thyroxine
Lipid soluble hormone involved in determining metabolic rate
Polypeptide hormones
They are chains of amino acids
Each are polypeptide chains of diferent lengths and different sequences
Ex: insulin
Eicosanoids
Eicosanoids are signaling molecules synthesized by essential fatty acids
Used to regulate membrane fluidity
Prostaglandins
mediate inflammation
Steroid hormones
All made from cholesterol
Lipid soluble
Cortisol
Estradiol/Testosterone