The synapse presentation on education in school ppt

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1. The synapse.
Electrical synapses: gap junctions.
Chemical synapses. Release of neurotransmitter.
Action of neurotransmitter

2. CELL SIGNALING
Cells communicate by signaling each other
chemically.
These chemical signals are regulatory molecules
released by neurons and endocrine glands,
and by different cells within an organ.

3. CELL SIGNALING
Cell signaling can be divided into three general categories:
1. paracrine signaling; 2. synaptic signaling; 3. endocrine
signaling
Chemical signaling between cells.
(a) In paracrine signaling, regulatory molecules are released by the cells of an
organ and target other cells in the same organ.
(b) In synaptic signaling, the axon of a neuron releases achemical
neurotransmitter, which regulates a target cell.
(c) In endocrine signaling, an endocrine gland secretes hormones into the
blood, which carries the hormones to the target organs.

4. Second Messengers
How regulatory molecules influence their target
cells. Regulatory molecules that are polar bond to
receptor proteins on the plasma membrane of a
target cell, and the activated receptors send second
messengers into the cytoplasm that mediate the
actions of the hormone.
Nonpolar regulatory molecules pass through the
plasma membrane and bind to receptors within the
cell. The activated receptors act in the nucleus to
influence genetic expression.
1. The polar regulatory
molecule binds to its receptor
in the plasma membrane.
2. This indirectly activates an
enzyme in the plasma
membrane that produces
cyclic AMP from its precursor,
ATP, in the cell cytoplasm.
3. Cyclic AMP concentrations
increase, activating
previously inactive enzymes in
the cytoplasm.
4. The enzymes activated by
cAMP then change the
activities of the cell to produce
the action of the
regulatory molecule.

5. G-Proteins
The G-protein cycle.
1. When the receptor is not bound to the regulatory molecule, the three G-protein
subunits are aggregated together with the receptor, and the α subunit binds GDP.
2. When the regulatory molecule attaches to its receptor, the α subunit releases
GDP and binds GTP; this allows the α subunit to dissociate from the βγ subunits.
3. Either the α subunit or the βγ complex moves through the membrane and
binds to the effector protein (an enzyme or ion channel). (4) The α subunit splits
GTP into GDP and Pi, causing the α and βγ subunits to reaggregate and bind to
the unstimulated receptor once more.

6. THE SYNAPSE
Once action potentials reach the end of an axon,
they directly or indirectly stimulate (or inhibit)
the other cell.
In specialized cases, action potentials can directly
pass from one cell to another. In most cases,
however, the action potentials stop at the axon
terminal, where they stimulate the release of a
chemical neurotransmitter that affects the next
cell.

7. THE SYNAPSE
A synapse is the functional connection between a neuron and
a second cell.
Neuron-neuron synapses involve:
axodendritic,axosomatic, and axoaxonic synapses
(btw axon of one neuron and the dendrites, cell body, or axon
of a second neuron)
Neuron-muscle synapses –neuromuscular synapses
Two hypothesis of synaptic transmission:
Electrical transmission
Chemical transmission

8. Electrical Synapses:Gap Junctions
The structure of gap junctions.
Gapjunctions are water-filled channels through which ions can pass from one cell
to another. This permits impulses to be conducted directly from one cell to another.
Each gap junction is composed of connexin proteins. Six connexin proteins in one
plasma membrane line up with six connexin proteins in the other plasma
membrane to form each gap junction.

9. Chemical Synapses
An electron micrograph of a chemical synapse.
This synapse between the axon of a somatic motor neuron and a skeletal
muscle cell shows the synaptic vesicles at the end of the axon and the
synaptic cleft. The synaptic vesicles contain the neurotransmitter chemical

10. Release of Neurotransmitter
Steps 1–4 summarize how action potentials stimulate the exocytosis of synaptic
vesicles. Action potentials open channels for Ca2+, which enters the cytoplasm and
binds to a sensor protein, believed to be synaptotagmin. Meanwhile, docked
vesicles are held to the plasma membrane of the axon terminals by a complex of
SNARE proteins. The Ca2+-sensor protein complex alters the SNARE complex to
allow the complete fusion of the synaptic vesicles with the plasma membrane, so that
neurotransmitters are released by exocytosis from the axon terminal

11. Action of Neurotransmitter
Two broad categories of gated ion channels have
been described: voltage-regulated
chemically regulated.
chemically regulated channels open in response to the binding of
postsynaptic receptor proteins to their neurotransmitter ligands
The opening of specific channels—particularly those that allow
sodium or calcium ions to enter the cell—produces a graded
depolarization, where the inside of the postsynaptic membrane
becomes less negative. This depolarization is called an excitatory
postsynaptic potential (EPSP) because the membrane potential
moves toward the threshold required for action potentials.

12. In other cases, as when chloride enters the cell through
specific channels, a graded hyperpolarization is produced
(where the inside of the postsynaptic membrane becomes
more negative). This hyperpolarization is called an inhibitory
postsynaptic potential (IPSP) because the membrane
potential moves farther from the threshold depolarization
required to produce action potentials.

13. The functional specialization of different regions in a multipolar
neuron.
Integration of input(EPSPs and IPSPs) generally occurs in the dendrites
and cell body, with the axon serving to conduct action potentials

14. The different regions of the postsynaptic neuron are specialized, with ligand-
(chemically) gated channels located in the dendrites and cell body, and
voltage-gated channels located in the axon
Events in excitatory synaptic transmission.

17. Divergence of neural pathways -one neuron
can make synapses with a number of other
neurons, by that means either stimulate or
inhibit them.
By contrast, convergence of neural pathways-
a number of axons can synapse on a single
neuron.

18. Spatial summation occurs due to the convergence of
axon terminals from different presynaptic axons (up
to a thousand in some cases) on the dendrites and
cell body of a postsynaptic neuron.
In temporal summation, successively rapid bursts of
activity of a single presynaptic axon can cause
corresponding bursts of neurotransmitter release,
resulting in successive waves of EPSPs (or IPSPs) that
summate with each other as they travel to the initial
segment of the axon.

20. Thank you for attention!