1 Postural Control in Multiple Sclerosis: Stability and Complexity Analyses!Communication between neurons: !synaptic transmission! University of Massachusetts Amherst Department of Kinesiology Questions ① What type neuronal synapses exist? ② What kind of neurotransmitters exist? Questions 1. What type neuronal synapses exist? Electrical and chemical synapses differ in their transmission mechanisms2 Intercellular communiction - Gap junctions The current I generated by the presynaptic cell has two alternative routes: it can either cross the gap and enter the postsynaptic cell, or it can simply leak out sideways through the synaptic cleft. Gap junctions: - Increaser Rl (lateral) - Reduce Rf (forward) Electrical and chemical synapses differ in their transmission mechanisms (Part 1) Fast Bi-directional Respiration Structure and function of gap junctions at electrical synapses (Part 2) Crayfish neuron: brief synaptic delay: ~ 0.1 ms Structure and function of gap junctions at electrical synapses (Part 3) Synchronization: hippocampus neurons3 Electrical synapse • Limitation: difficult in transmission of signal from small to large neuronal cell -> small neuron is not able to generate action potential in larger one. • Answer: chemical neurotransmitters Electrical and chemical synapses differ in their transmission mechanisms (Part 2) Slower Activation and inhibition - modulation Chemical Neurotransmission Sequence of events involved in transmission at a typical chemical synapse4 Co-transmitters Co-transmitters: single neuron contains two or more neurotransmitters Direct and indirect chemical neurotransmission direct: Cholinergic receptors – neuromuscular junction Indirect: G-protein gated channels with effect on membrane channels. (Left) The transduction mechanism in retinal rod receptors that allows them to respond to light. Questions 2. What kind of neurotransmitters exist? neurotransmitters • Acetylcholine (Ach) : neuromuscular junction • Glutamate : excitatory • Gamma-aminobutyric acid (GABA) : inhibitory • dopamine : movement: excitatory • Serotonin : sleep and wakefulness • Norepinephrine: arousal and attention • Histamine : arousal and attention5 Gamma Amino-Butyric Acid (GABA): main inhibitor Spastic Diplegia (Cerebral Palsy): Damage to upper motor neurons in Cerebral cortex, basal ganglia and brainstem; reduced GABA absorption. Result: increased tone (hypertonicity/spasticity/malformation) Dopamine Stimulants such as cocaine and methamphetamines act directly on dopamine; Reward system; produced in brain. Parkinsons: lack of dopamine; Schizophrenia: elevated levels. Glutamate Found in majority of excitatory synapses in brain and spinal cord. Involved in synaptic plasticity; plays role in neurodegeneration after brain/cord damage: overstimulation and cell death. Acetylcholine Excitatory neurotransmitter at neuromuscular junction; Autonomic nervous system: inhibitory for heart rate. Disease: Myasthenia Gravis – “grave muscle weakness” Questions 1. What type neuronal synapses exist? 2. What kind of neurotransmitters
View Full Document
Unlocking...