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Synapses

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Synapses Electrical Synapses Chemical Synapses a. ionotropic (chemically gated) b. metabotropic (G-protein mediated) Synapse: junction between the axon terminus of ... – PowerPoint PPT presentation

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Title: Synapses


1
Synapses
  1. Electrical Synapses
  2. Chemical Synapsesa. ionotropic (chemically
    gated)b. metabotropic (G-protein mediated)

2
Synapse junction between the axon terminus of
one neuron and another neuron or effector (muscle
or gland).
3
Electrical Synapse (rare)
In an electrical synapse, current passes directly
from one cell to the next. Very rapid (a few
milliseconds) Examples include neurons that
control the snap of a crayfish tail and the
flip of a caudal fin of a fish.
4
Chemical Synapse ionotropic
Requires neurotransmitter for transmission Require
s chemically gated channels onpost-synaptic
membrane May involve degradative enzymes May
involve reuptake transporters on pre-synaptic
membrane
5
Chemical Synapse ionotropic
6
Examples of Neurotransmitters
  • Acetyl choline found at all nerve-muscle
    synapses (neuromuscular junctions)
  • Norepinephrine important neurotransmitter found
    throughout the central nervous system and
    peripheral nervous system.
  • Serotonin found primarily in the brain
    effects mood.
  • Dopamaine found primarily in the brain
    controls motor pathways and effects mood.

7
  • What is the function of degradative enzymes at
    the synapse?
  • What is the function of reuptake transporters at
    the presynaptic membrane?
  • Therapeutic and Recreational Drug EffectsA.
    monoamine oxidase inhibitors (MAOI)B. Prozac
    (selective serotonin reuptake inhibitors)C.
    Cocaine ( dopamine reuptake inhibitor)

8
Post-Synaptic Effects of Ionotropic Synapses
  • Excitatory Post-Synaptic Potentials
  • Inhibitory Post-Synaptic Potentials

9
Summation at the Hillock
Excitatory opens Na channels and causes graded
depolarization. Inhibitory opens K channels
and causes graded hyperpolarization.
Excitatory

Inhibitory
-
Summation of excitatory and inhibitory
post-synaptic potentials - may lead to
threshold and initiate an action potential.
10
Chemical Synapse metabotropic
Requires neurotransmitter for transmission Requir
es G-protein coupled receptor on post-synaptic
membrane G-protein activates an enzyme on the
cytoplasmic side of the membrane May involve
degradative enzymes May involve reuptake
transporters on pre-synaptic membrane Examples
transmission of smell, control of cardiac muscle
11
Cells of The Nervous System
Two neurons releasing neurotransmitters that act
on a third neuron. The first two neurons could
be in the Central Nervous System, and the third
might be a motor neuron leading out to a muscle
or gland.
Schwann Cells form a myelin sheath Around the
axon of motor neurons
  • Neuroglia (supporting cells)
  • Provide physical support to neurons
  • Provide electrical insulation to neurons
  • - May be involved in processes such as memory.
  • Neurons
  • Detect physical and chemical changes in their
    environment
  • Transmit electric impulses (action potentials)
    from one end to the other (one cell may be more
    than 3 feet long)
  • - Communicates with other neurons, muscles and
    glands using chemicals called neurotransmitters.

12
Motor neurons have their cell bodies in the
spinal cord, but their axons extend outward into
the body to stimulate muscles or glands.
Spinal cord smear
Dendrites
Microglia
13
Pyramidal cells (neurons) of the cerebral cortex
(Golgi stain)
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Cells of the Central Nervous System
19
Microglia - immune-like cells
20
Oligodendrocyte produce myelin sheath
21
Ependymal cells - line ventricles and help
produce cerebrospinal fluid
22
Astrocyte - blood brain barrier
23
Cerebrum
Cerebellum
Brain Stem
24
Central Sulcus
Sulcus
Gyrus
Transverse Fissure
Lateral Fissure
25
Lobes of the Cerebrum
Parietal Lobe
Frontal Lobe
Occipital Lobe
Temporal Lobe
26
Cerebrum
Corpus Callosum
Thalamus
Hypothalamus
Pons
Midbrain
Medulla
27
Cerebrum
Corpus Callosum
Thalamus
Basal Ganglia
28
Limbic System amygdala, hippocampus,
hypothalamus and cingulate gyrus The four Fs
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