Neurotransmitters
neurotransmitters are the language of the nervous system
one type of chemical signaling
chemical signaling is the main way cells talk to each other
Many different kinds of chemicals can be used for signaling:
a. paracrine regulators (tissue hormones)
effects only on neighboring cells
distributed by simple diffusion through interstitial fluids
don’t enter blood
rapidly inactivated by enzymes after triggering receptor
protein on target cell
eg. histamine
b. neurotransmitters
secreted by neurons in response to electrical stimulus
very short range cell to cell across synapse
c. neurohormones
released into blood by neurons
d. hormones
long range
secreted into blood by endocrine gland
specific chemicals bind to receptors on or in cell to cause change in cell function
some receptor proteins are enzymes that cause reactions
some open and close gated membrane channels
cell only responds to a chemical if it has the correct receptor protein
= target cell for that chemical
Neurotransmitters are released at most synapses
100’s of neurotransmitters have been identified
some are excitatory
some are inhibitory
some neurons produce and release a single NT
Human Anatomy & Physiology: Nervous System-Neurotransmitters; Ziser, Lecture Notes, 2005 1
, most make 2 or more and can release one or all at the same time
different cells respond in different ways to same chemical
eg. ACh stim skeletal muscle cells
inhibits heart muscle cells
the same NT may have different effects in different parts of body
eg. excitatory one place, inhibitory another
The effect of a NT on a postsynaptic neuron depends on:
the properties of the receptor protein
not on the nature of the NT
a variety of different kinds of chemicals have been found to act as
neurotransmitters:
1. acetylcholine
2. protein & peptides
3. amino acid derivatives
biogenic amines
amino acids
4. Inorganic gasses
5. ATP
synapses in PNS release only a few different neurotransmitters
eg. Somatic Motor Neurons ACh,
eg. Autonomic Motor Neurons Epinephrine, NE
most of the diversity is in the CNS, esp the brain
Neuromodulators
other chemicals can be released at synapse in addition to neurotransmitters:
=neuromodulators
neuromodulators can influence the release of NTs or the post synaptic
neuron’s response to the NT
NM are usually peptides = neuropeptides
a chemical may be both a NT and NM
Human Anatomy & Physiology: Nervous System-Neurotransmitters; Ziser, Lecture Notes, 2005 2
neurotransmitters are the language of the nervous system
one type of chemical signaling
chemical signaling is the main way cells talk to each other
Many different kinds of chemicals can be used for signaling:
a. paracrine regulators (tissue hormones)
effects only on neighboring cells
distributed by simple diffusion through interstitial fluids
don’t enter blood
rapidly inactivated by enzymes after triggering receptor
protein on target cell
eg. histamine
b. neurotransmitters
secreted by neurons in response to electrical stimulus
very short range cell to cell across synapse
c. neurohormones
released into blood by neurons
d. hormones
long range
secreted into blood by endocrine gland
specific chemicals bind to receptors on or in cell to cause change in cell function
some receptor proteins are enzymes that cause reactions
some open and close gated membrane channels
cell only responds to a chemical if it has the correct receptor protein
= target cell for that chemical
Neurotransmitters are released at most synapses
100’s of neurotransmitters have been identified
some are excitatory
some are inhibitory
some neurons produce and release a single NT
Human Anatomy & Physiology: Nervous System-Neurotransmitters; Ziser, Lecture Notes, 2005 1
, most make 2 or more and can release one or all at the same time
different cells respond in different ways to same chemical
eg. ACh stim skeletal muscle cells
inhibits heart muscle cells
the same NT may have different effects in different parts of body
eg. excitatory one place, inhibitory another
The effect of a NT on a postsynaptic neuron depends on:
the properties of the receptor protein
not on the nature of the NT
a variety of different kinds of chemicals have been found to act as
neurotransmitters:
1. acetylcholine
2. protein & peptides
3. amino acid derivatives
biogenic amines
amino acids
4. Inorganic gasses
5. ATP
synapses in PNS release only a few different neurotransmitters
eg. Somatic Motor Neurons ACh,
eg. Autonomic Motor Neurons Epinephrine, NE
most of the diversity is in the CNS, esp the brain
Neuromodulators
other chemicals can be released at synapse in addition to neurotransmitters:
=neuromodulators
neuromodulators can influence the release of NTs or the post synaptic
neuron’s response to the NT
NM are usually peptides = neuropeptides
a chemical may be both a NT and NM
Human Anatomy & Physiology: Nervous System-Neurotransmitters; Ziser, Lecture Notes, 2005 2
