Chemical Signaling by Neurotransmitters and Hormones Flashcards
What are the three types of synaptic connections?
- Axodendritic
- Axosomatic
- Axoaxonic
What are the most common synapses in the brain?
Axodendritic
What’s an axodendritic synapse?
An axon terminal from the presynaptic neuron communicates with a dendrite of the postsynaptic cell
What are axosomatic synapses?
Synapses between a nerve terminal and a nerve cell body
What are axoaxonic synapses?
One axon synapses on the terminal of another axon
Neuromuscular junction
The connection point between a neuron and a muscle
Neuromuscular junction
The connection point between a neuron and a muscle
What are some amino acids?
- Glutamate
- GABA
- Glycine
What are some monoamines?
- Dopamine
- Norepinephrine
- Serotonin
Dopamine is what kind of neurotransmitter?
Monoamine
Serotonin is what kind of neurotransmitter?
Monoamine
Norepinephrine is what kind of neurotransmitter?
Monoamine
GABA is what kind of neurotransmitter?
Amino acid
Glycine is what kind of neurotransmitter?
Amino acid
Glutamate is what kind of neurotransmitter?
Amino acid
What are some functions of amino acids?
- Serve as building blocks of proteins
- Metabolic things
What is the largest group of “nonclassical” neurotransmitters?
Neuropeptides
Where are neurotransmitters manufactured?
Anywhere in the cell (except for neuropeptides)
What is the most recently discovered group of neurotransmitters?
Gaseous transmitters
Exocytosis
A fusion of the vesicle membrane with the membrane of the axon terminal
Active zones
Specialized regions near the postsynaptic cell, which stain darkly on the electron micrograph
What is required for exocytosis to take place?
A vesicle must be transported to an active zone, and then “dock” to the active zone
Vesicle recycling
The continuous release and reformation of vesicles
Neurotransmitter release is regulated by what different mechanisms?
- Rate of cell firing
- Probability of transmitter release from the terminal
- Presence of autoreceptors on axon terminals or cell bodies and dendrites
What happens when a neuron is rapidly firing action potentials?
It will release much more transmitter
What are the two different types of autoreceptors?
- Terminal autoreceptors
- Somatodendritic autoreceptors
What is the main function of terminal autoreceptors?
To inhibit further transmitter release
What is the main function of somatodendritic autoreceptors?
To slow the rate of cell firing
What is the main function of somatodendritic autoreceptors?
To slow the rate of cell firing
What are the ways of neurotransmitter inactivation?
- Enzymatic breakdown
- Reuptake by the axon terminal
- Uptake by nearby glial cells
Reuptake
Transport out of the synaptic cleft by the same cell that released the transmitter
What are the two types of neurotransmitter receptors?
- Metabotropic receptors
- Ionotropic receptors
What is another name for ionotropic receptors?
Ligand-gated channel receptors
Which type of neurotransmitter receptor goes through desensitization?
Ionotropic receptors
Desensitization
The channel remains closed even though there may be ligand molecules bound to the receptor
Once desensitization occurs, what must happen before the channel can be activated again?
It must resensitize
What are the two major mechanisms by which all G proteins operate?
- By stimulating or inhibiting the opening of ion channels in the cell membrane
- By stimulating or inhibiting certain enzymes in the cell membrane
Protein kinases
Enzymes that phosphorylate a protein
Phosphorylate
To catalyze the addition of one or more phosphate groups to the molecule
What are the second-messenger systems?
- Cyclic AMP (cAMP)
- Cyclic GMP (cGMP)
- Phosphoinositide
- Calcium (Ca2+)
What is the associated protein kinase for cyclic AMP?
Protein kinase A (PKA)
What is the associated protein kinase for cyclic GMP?
Protein kinase G (PKG)
What is the associated protein kinase for phosphoinositide?
Protein kinase C (PKC)
What is the associated protein kinase for calcium?
Calcium/calmodulin kinase (CaMK)
Tyrosine kinase receptors
Receptors that mediate the action of neurotropic factors
What are the three specific tyrosine kinase receptors that are used by neurotropic factors?
- trkA for NGF
- trkB for BDNF and NT-4
- trkC for NT-3
What are the two ways to reduce the inactivation of a neurotransmitter?
- By blocking the enzyme involved in its breakdown
- For neurotransmitters that use transporters for reuptake out of the synaptic cleft, by blocking those transporters
Where are the adrenal glands located?
Over each kidney
What is the inner part of the adrenal gland?
The adrenal medulla
What are the cells of the adrenal medulla called?
Chromaffin cells
What is the outer part of the adrenal gland?
The adrenal cortex
What is one of the main functions of glucocorticoids?
To maintain normal blood glucose levels while helping to store excess glucose for future use
What hormone is secreted by the adrenal cortex?
Glucocorticoids
Where is the thyroid gland located?
In the throat
Where is the pineal gland located?
Just over the brainstem
Where is the pituitary gland located?
Just under the hypothalamus
Describe step 1 in figure 3.5
Neurotransmitter is synthesized and then stored in vesicles
Describe step 2 in figure 3.5
An action potential invades the presynaptic terminal
Describe step 3 in figure 3.5
Depolarization of presynaptic terminal causes opening of voltage-gated Ca2+ channels
Describe step 4 in figure 3.5
Influx of Ca2+ ions through channels
Describe step 5 in figure 3.5
Ca2+ causes vesicles to fuse with presynaptic membrane
Describe step 6 in figure 3.5
Neurotransmitter is released into synaptic cleft via exocytosis
Describe step 7 in figure 3.5
Neurotransmitter binds to receptor molecules in postsynaptic membrane
Describe step 8 in figure 3.5
Opening or closing of postsynaptic channels
Describe step 9 in figure 3.5
Postsynaptic current causes excitatory or inhibitory postsynaptic potential that changes the excitability of the postsynaptic cell
Describe step 10 in figure 3.5
Retrieval of vesicular membrane from plasma membrane
