4c Chemical Structures Of Neurotransmitters Flashcards
What are the neurotransmitters we are responsible for?
Adrenaline
Noradrenaline
Serotonin
Acetylcholine
GABA (gamma-aminobutyric acid)
What makes epinephrine/adrenaline and norepinephrine/noradrenaline special?
They can act as hormones and neurotransmitters
What effect does an excitatory neurotransmitter have on a post synaptic cell? Inhibitory?
Excitatory: causes the post synaptic cell to depolarize (more positive Na+ ions enter) and leads to a positive membrane potential
Inhibitory: causes the post synaptic cell to hyperpolarize (prevents + ions from entering and/or allows - ions to enter)
How can neurons be classified?
According to the neurotransmitter released at the presynaptic axon terminal
Ex. Neurons that release serotonin form serotonergic synapses
Describe the direct mechanism of water based neurotransmitter action.
Direct-> ligand gated ion channels
1. Neurotransmitter binds to the ion channel, opening it
2. Ions follow the gradient and enter (usually Na+ or Ca2+ or both)
3. Ions flow across the membrane which leads to depolarization
Describe the indirect mechanism of water based neurotransmitter action?
G-protein coupled receptors
1. Neurotransmitter binds to receptor
2. Receptor activates g-protein on inside of membrane
3. G-protein subunits or intracellular messagers regulate ion channels
4. The ion channels open and ions flow
Is acetylcholine excitatory or inhibitory or both?
Mostly excitatory but inhibitory at neuromuscular synapses with the heart
Where is the neurotransmitter acetylcholine found?
CNS: throughout the brain
PNS: neuromuscular junction (voluntary muscle), sympathetic nervous system, parasympathetic nervous system
Is norepinephrine excitatory or inhibitory and what is it involved in?
Excitatory
Involved in: attention/consciousness, temperature control, pituitary gland secretion
Where is norepinephrine found?
CNS: brain, spinal cord
PNS: neuromuscular tissue and neuroglandular junctions of the sympathetic nervous system
Is dopamine excitatory or inhibitory?
Excitatory (amplified by cocaine)
Inhibitory (involved in precise movement control)
Where is dopamine found?
CNS: hypothalamus, midbrain, limbic system, cerebral cortex, retina
Is serotonin excitatory or inhibitory and what does it affect?
Both
Attention and emotional states
What is an example of a selective serotonin reuptake inhibitor?
Ecstasy
What does SSRI stand for?
Selective Serotonin Reuptake Inhibitor?
What causes depression?
Low levels of serotonin OR serotonin left too long leading to less sensitivity of neurotransmitters
Where is serotonin found?
CNS: hypothalamus, cerebellum, spinal cord, retina
Is GABA inhibitory or excitatory and what effect does it have?
Inhibitory
Anti-anxiety effect
What does GABA stand for?
gamma aminobutyric acid
Where is GABA found?
CNS: cerebral cortex, cerebellum, interneurons in spinal cord
Is Glutamate excitatory or inhibitory and what does it affect?
Excitatory
Important in memory and learning
Where is glutamate found?
CNS: cerebral cortex brainstem
What is the main excitatory neurotransmitter in the brain?
Glutamate
Where is acetylcholine excitatory?
Neuromuscular junctions with skeletal muscle and smooth muscle of the intestines
Where is acetylcholine inhibitory?
Between the vagus nerve and cardiac muscles
What do you call synapses where acetylcholine is released
Cholinergic
What’s the difference between the types of cholinergic synapses?
The structure of the receptors
If it finds the nicotine receptor, you get muscle contraction
If it finds the muscarinic receptor, it slows the heart rate
What do you call synapses where norepinephrine is released?
Adrenergic
The veins in your face have what kind of receptors?
Beta adrenergic receptors (for norepinephrine)
What kind of receptors do most of the veins in your body have?
Alpha adrenergic receptors
What’s the difference between alpha and beta adrenergic receptors?
Activated beta adrenergic receptors cause blood vessels to dilate, heating the skin and causing blushing
Activated alpha adrenergic receptors cause blood vessels to constrict and shunt blood towards the heart and away from the skin in fight or flight response
What is an agonist in the context of the nervous system?
A drug that mimics the effect of a neurotransmitter
What is an antagonist in the context of the nervous system?
A drug that blocks the effect of the neurotransmitter
Why do agonists work?
They have the same shape as the normal neurotransmitter and therefore can be detected by the same receptor
How do antagonists work?
The drug is close enough in shape to bind to the receptor but not close enough to produce an effect
This allows it to take up receptor space and prevents the neurotransmitter from actually binding to its site
What are the two kinds of antagonists and how do they differ?
Reversible: bind to the receptor in a non-permanent way
Irreversible: binds in a permanent way, can result in a permanent change in receptor, stopping it from binding to future ligands even after it detaches
What are the agonists of acetylcholine and what do they do?
Nicotine: It activates muscles to contract when it meets the nicotinic receptor
Muscarine: slows down your heart rate when bound to muscarine receptor
What molecules does the nicotinic receptor recognize?
Nicotine and acetylcholine and curare
What are the antagonists of acetylcholine and what do they do?
Curare: Prevents muscles from contracting when bound to the nicotinic receptor
Atropine: speeds up the heart rate when bound to muscarinic receptor
What molecules does the muscarinic receptor recognize?
Acetylcholine, muscarine and atropine
What does acetylcholine control and what are the associated agonists and antagonists?
Activates muscle contractions: nicotine is agonist and curare is antagonist
Lowers heart rate: muscarine is agonist and atropine is agonist
How can drugs act on neurotransmitters?
As agonists, antagonists, indirect agonists and indirect antagonists
What does a indirect agonist do?
Enhances neurotransmitter actions
Does not directly bind to receptor site to promote the action done by neurotransmitter but does something else that enhances the effect of the neurotransmitter, like maybe affecting the supply
What do indirect antagonists do?
Inhibit release or production of a neurotransmitter
Does not directly bind to receptor site
What are the different diseases we are responsible for?
Alzheimer’s disease
Clinical depression
Parkinson’s disease
What characterizes Alzheimer’s disease?
It’s associated with decreased levels of acetylcholine
Progressive disease that destroys memory and other cognitive function
What characterizes clinical depression?
Decreased levels of serotonin, dopamine and norepinephrine
Persistent feeling of sadness and loss of interest, leads to emotional and physical problems
On a brain scan its mostly Blue, looks inactive
What characterizes Parkinson’s disease?
Associated with decreased levels of dopamine
Affects nerve cells that produce dopamine
Symptoms: muscle rigidity, tremors, changes in speech and gait
Whaat does Alzheimer’s look like on a brain scan?
Big hollow black region in middle of the brain as opposed to brighter colours indicating brain activity
Result of brain atrophy
What are reflexes?
Rapid, predictable and involuntary motor responses to stimuli
Unlearned and unpremeditated, may be considered to be built in to our neural anatomy
How do reflexes occur?
Over neural pathways called reflex arcs
What are the types of reflexes?
Somatic reflexes
Autonomic reflexes
What characterizes somatic reflexes?
Réflexes that stimulate the skeletal muscles
Involuntary (even though skeletal muscle is usually under voluntary control
What characterizes autonomic reflexes?
Regulate activity of smooth muscles, heart and glands (involuntary aspects)
What are the steps to a reflex arc?
- Sensory Receptor: reacts to stimulus
- Sensory neuron: carries message to the integration center
- Integration center: processes information and directs motor output
- Motor neuron: carries message to an effector
5 Effector organ: muscle or gland to be stimulated
What is a two neuron reflex arc and what makes it different?
Simplest type of reflex arc, very fast
No interneurons
What is an example of a two neuron reflex and explain?
Patellar reflex
-Sensory proprioceptor senses stretch of when patellar tendon is tapped
-afférent nerve impulse travels along sensory neuron to spinal cord
-synapses with motor neuron
-efferent impulse travels along motor neuron to the effector muscle which contracts the quadriceps
What is a three neuron reflex arc and what makes it different?
Slower than 2 neuron, but still very fast
This one does have an interneuron
What is an example of a three neuron reflex arc?
Flexor (withdrawal) reflex
Why is the two neuron pathway shorter in time than the three neuron pathway?
The less neurons there are, the shorter the pathway, the quicker the signals and information can be conveyed
What is a flexor reflex?
Type of three neuron reflex
Comes from the detection of a painful stimulus by the cutaneous sensory receptor
Response to pain
What are the steps of a flexor reflex arc?
painful stimulus is sensed by cutaneous sensory receptor
Sensory info is sent to spinal cord via sensory neuron
Synapses with interneuron
Interneuron synapses with motor neuron
Efferent impulse then travels along a motor neuron to a muscle
Where does the interneuron synapse with a motor neuron?
In the spinal cords gray matter
What is one of the more complicated reflexes?
Emesis (vomiting) reflex
Why do we test our reflexes?
To test the integrity of the nervous system, its ability to integrate information
The spinal cord is cut off from the brain. Is the patellar reflex still intact?
Yes, the control center of this two neuron pathway is in the spinal cord
