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Boğaziçi University
SCIENCE 102:
Neurons and Synapses
Prof.Dr. Hale Saybaşılı (BM501 Biology of Living Systems)
Yrd.Doç.Dr. Burak Güçlü (BM502 Intro. to Physiology)
Biomedical Engineering Institute
Morphology of neurons:
1012 neurons in the nervous system! 10-50 times this number of glial cells!
soma (cell body)
dendrites (input)
axon (output)
axon hillock
synaptic knobs, terminal buttons (contain vesicles of transmitters)
myelin (protein-lipid complex)
Schwann cell (a type of glial cell in the periphery)
oligodendrocyte (a type of glial cell in the central nervous system)
nodes of Ranvier (about 1 mm apart)
Stains for Neurons
Axoplasmic transport and exocytosis:
Action potential:
Resting membrane potential: -70 mV
Action potential:
depolarization
overshoot
repolarization
hyperpolarization.
Also called a ‘spike’.
All-or-none law!!!
Ionic basis of excitation & conduction:
Electrical equivalent of neuron membrane:
Synaptic transmission:
Neurons communicate mostly through
chemical synapses (synaptic cleft: 3050 nm wide)
Each neuron forms on average 1000
synaptic endings!
An average neuron may receive 40000
synapses!
Many many neurotransmitters:
Acetylcholine (myoneural junction,
autonomic system, many parts of brain)
Dopamine (hypothalamus, neocortex, limbic
system)
Epinephrine (hypothalamus, thalamus, spinal
cord)
Serotonin (hypothalamus, limbic system,
cerebellum)
Glutamate (cerebral cortex, brain stem)
Glycine (direct inhibiting neurons, retina)
GABA (cerebellum, cerebral cortex)
Substance P (endings of nociceptors)
NO (various parts of the brain, vascular
smooth muscle)
Nicotinic ACh receptor...