12. What does the depolarization of the presynaptic terminal lead to? What ion i
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12. What does the depolarization of the presynaptic terminal lead to? What ion is responsible for that response? 13. Describe the mechanisms of neurotransmitter release 14. Distinguish excitatory postsynaptic potential (EPSP) from inhibitory postsynaptic potential (IPSP). 15. Explain what are metabotropic and ionotropic receptors. 16. What are the main roles of the following neurotransmitters: (1) Acetylcholine, (2) Norepinephrine, (3) Dopamine, (4) Glutamate, (5) Glycine, (6) Serotonin, (7) GABA Regarding the neurotransmitters listed above, which tend to be inhibitory and which tend to be excitatory? Which is impaired in Parkinson's disease? Which is impaired in depression and other mood disorders? 17. 18. What are the main divisions of the cortex? Identify a known role to each of th regions 19. Indicate some functions of the hypothalamus, the basal ganglia and the cerebellum.Explanation / Answer
The neurons talk to each other at specialised region of contacts called synapse. The neuron that sends the signal is called the presynaptic neuron and the neuron which receive the signal is called the postsynaptic neuron. The neurotransmission across a nerve terminal starts with depolarization of the membrane. As the action potential reaches an axon terminal it causes depolarization of the membrane. Depolarization happens when the membrane potential changes due to a change in the permeability of the membrane to Na and K ions. As depolarization of presynaptic terminal happens it activates the voltage-gated Ca2+ ion channels.
13 The presynaptic influx of Ca2+ triggers the fusion of neurotransmitter-containing synaptic vesicles with the presynaptic membrane, resulting in the release of acetylcholine (ACh) at the cleft. ACh diffuses and binds specifically to the receptors on the postsynaptic membrane. These nAChRs are ligand-gated ion channels, upon binding the ligand they open and allow Na+ and Ca2+ influx into the cytosol of the postsynaptic cell. The influx of ions depends on the electrochemical gradient across the membrane. This influx of ions leads to depolarization of the postsynaptic cell and hence the transmission of information across the cell.
14. the binding of the neurotransmitter to the receptor on the postsynaptic membrane and causes the ion channels to close or open which changes the membrane potential and either make it more like or less likely to fire an action potential.
If this change in ion channel permeability makes it more like to fire an action potential it is called EPSP and if it is less to fire an action potential it is known as IPSP.
EPSPs are Depolarizing potentials they make the membrane potential of the cell positive and allow it to fire an action potential while IPSPs are hyperpolarising the cells they make them more negative and hence make the membrane potential below the threshold and decreases the chances to fire an action potential.
15. The ionotropic receptors allow for rapid neurotransmission and operate within milliseconds to send signals across the synapse. Ionotropic receptors are synonymous with ligand-gated ion channels. They allow ion passage across the membrane upon binding the specific ligands. Metabotropic receptors, on the other hand, activate a signaling cascade to regulate the ion channel activity upon binding to the neurotransmitter. These receptors operate over a time range of tens of milliseconds to seconds.
16. Acetylcholine: major excitatory neurotransmitter of the peripheral nervous system.
Norepinephrine: Also known as stress hormone as it is released from the nervous system in response to stress.
Dopamine: it plays important role in reward-motivated behavior and also regulate movement and emotional response.
Glutamate: a Major excitatory neurotransmitter in the central nervous system.
Glycine: inhibitory neurotransmitter in the central nervous system.
Serotonin: mood regulation, sleep, and appetite regulation.
GABA: inhibitory neurotransmitter.
17. acetylcholine and glutamate are excitatory while glycine and GABA are inhibitory. Dopamine can act as both excitatory and inhibitory neurotransmitter depending upon the site where it binds. In Parkinson disease, the nerve cell in the brain responsible for the body movement degenerates slowly. In this disease, dopamine and dopaminergic neurons play an important role as they play important role in regulating the body movements.
As these neurons begin to die the patients show symptoms like tremors, stiffness and balance problems.
The neurotransmitter serotonin, norepinephrine, and dopamine are associated with depression and mood disorders.
18. frontal lobe: thinking, planning, programming needs, and emotion
parietal lobe: pain, touch, taste, temperature
temporal lobe: auditory sense
occipital lobe: visual information
19. Hypothalamus: hormone production from pituitary and homeostasis.
Basal ganglia: control voluntary movements, eye movement, cognition, learning and habit learning
cerebellum: motor control, balance, coordination and speech
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