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 hillocksynaptic 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:

depolarizationovershootrepolarizationhyperpolarization.

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: 30-50 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...