Neurotransmitters Flashcards
What are neurotransmitters?
Neurotransmitters are chemical signaling molecules/ messengers which transmits signals from one neuron to another. They are endogenous and are found throughout the body.
They transmit signals between neurons in the brain and other parts of the body, thereby allowing communication within the brain and between the brain and the rest of the body.
Neurotransmitters can either be excitatory or inhibitory .
Neurotransmitters do not bind to only neurons, they can also bind to tissues, muscles cells or glands
List the functions of neurotransmitters
- SIGNAL TRANSMISSION
- REGULATION OF MOOD AND EMOTIONS
- MOTOR CONTROL
- MEMORY AND LEARNING
- PAIN SENSATION
- REGULATION OF SLEEP AND WAKEFULLNESS.
Outline how neurotransmitters work
First, neurotransmitters are synthesized within the neuron’s cell body or nerve terminals from precursor molecules through enzymatic reactions. Once synthesized, they are packaged into small vesicles within the nerve terminals. Then, when an action potential reaches the nerve terminal, it triggers the release of neurotransmitters from the vesicles into the synaptic cleft.
The released neurotransmitters then diffuse across the synaptic cleft and bind to specific receptors the postsynaptic neuron.
After binding, the neurotransmitter can either excite or inhibit the postsynaptic neuron depending on the receptor type. This leads to the generation of an electrical impulse in the postsynaptic neuron.
After transmitting their signals, neurotransmitters can be taken up again into the presynaptic neuron and used for another synthesis
List the neurotransmitters
Adrenaline
GABA
Noradrenaline
Acetylcholine
Dopamine
Glutamate
Serotonin
Endorphins
Describe glutamate as a neurotransmitter
Glutamate is the main excitatory transmitter in the brain and spinal cord and has been calculated to be responsible for 75% of the excitatory transmission in the CNS. There are two distinct pathways involved in the synthesis of glutamate. In one pathway, a-ketoglutarate produced by the Krebs cycle is converted to glutamate by the enzyme GABA transaminase (GABA-T). In the second pathway, glutamate is released from the nerve terminal into the synaptic cleft by Ca 2+ -dependent exocytosis and transported via a glutamate reuptake transporter into glia, where it is converted to glutamine by the enzyme glutamine synthetase. Glutamine then diffuses back into the nerve terminal where it is hydrolysed back to glutamate by the enzyme glutaminase.
• Glutamate has 2 major receptors that neurotransmitters bind to called
NMDA and AMPA.
What is the function of glutamate?
Involved in learning and memory, regulates development and creation of nerve contacts
Describe GABA as a neurotransmitter
GABA is the major inhibitory mediator in the brain and mediates both presynaptic and postsynaptic inhibition. GABA, which exists as B-amino butyrate in the body fluids, is formed by decarboxylation of glutamate by the enzyme glutamate decarboxylase (GAD), which is present in nerve endings in many parts of the brain.
• GABA plays an important role in inhibiting neurons by increasing chloride ions in the cell, causing hyperpolarization, thereby stopping the neurons from firing off.
What is the function of GABA?
Calms firing nerves in CNS
High levels improve focus, low levels cause anxiety.
Also contributes to motor control and vision
Describe serotonin as a neurotransmitter
Serotonin(5-HT) is a neutransmitter and hormone produced in the brain and intestines, which influences mood, emotions and digestion.
It is derived from the amino acid tryptophan. It plays a vital role in regulating sleep, thermoregulation, memory, sexual activity and learning.
It is sometimes called the ‘ happy chemical
as it contributes to happiness.
- Serotonin plays an important role in sleep, mood, emotions.
• It also plays a role in bone remodeling.
Describe dopamine as a neurotransmitter
Dopamine plays a crucial role in daily life functions affecting movement, emotions, memory, attention, cognition and impulse control.
Dopamine has 2 major receptors which are D1 and D2. Binding of neurotransmitters on Di causes an excitatory signal while binding on
D2 receptors causes an inhibitory signal.
Dopamine receptors couple to different G proteins sites, leading to the activation or inhibition of adenylyl cyclase and k+ channels.
Involved in the reward pathway
What are the functions of serotonin?
- Blood clotting: helps the body to heal faster
- Sleep: stimulates the areas of the brain that are in control of sleep-wake behavior
- Sexual function: can cause a decreased libido when levels are too high
- Bone health: can cause osteoporosis when levels are too high
- Mood regulation: reduces feelings of depression and anxiety
- Nausea: helps the body expel food quicker than normal
Describe acetylcholine as a neurotransmitter
Acetylcholine is a neurotransmitter and hormone involved in stimulating muscle contractions, regulating heart rate, controlling smooth muscle contractions, memory and learning process.
• It is produced from choline and acetyl co-A, stored at nerve endings and released into the synaptic cleft to bind to receptors, triggering various responses.
Acetylcholine effect in the PNS is that it is responsible for skeletal muscle contraction by binding to muscarinic receptors.
In the CNS, acetylcholine plays a role in memory and cognition
Describe norepinephrine as a neurotransmitter
• A neurotransmitter and a hormone that plays a crucial role in
‘fight or flight response’
• It is a part of the sympathetic nervous system which is activated during emergency situations to prepare the body for action.
• As a neurotransmitter, norepinephrine helps in transmitting signals between nerve cells.
• Has functions such as constriction of blood vessels leading to increase in blood pressure, increases heart rate and can also regulate the release of opioids.
List the diseases associated with neurotransmitters
Alzheimer’s disease
Depression
Schizophrenia
Parkinson’s disease
Epilepsy
Myasthenia gravis
Huntingtons disease
What is the correlation between Alzheimer’s and neurotransmitters
Alzheimer’s disease is a neurodegenerative disorder characterized by learning and memory impairments. It is associated with a lack of acetylcholine in certain regions of the brain.
