neurons + synaptic transmission

• Neurons are the basic building blocks of the nervous system.
• There are over 100 billion neurons in the human nervous system.
• Over 80% of neurons in the human nervous system are located in the brain.
• Neurons transmit messages through electrical and chemical signals.
• Order the three main types of neurons based on their function in the nervous system.

  1️⃣ Sensory neuron

  2️⃣ Relay neuron

  3️⃣ Motor neuron
• Sensory neurons carry messages from the peripheral nervous system to the central nervous system.
• The cell body of a neuron contains the nucleus, which holds the genetic material.
• Dendrites carry impulses from neighboring neurons towards the cell body.
• The long, fatty layer covering the axon is called the myelin sheath.
• The myelin sheath protects the axon and speeds up electrical transmission.
• The gaps in the myelin sheath are called the nodes of Ranvier.
• The nodes of Ranvier allow the electrical impulse to jump across the axon.
• Terminal buttons at the end of the axon communicate with the next neuron across a synapse.
• When a neuron is in a resting state, its inside is negatively charged.
• When a neuron is activated, its inside becomes positively charged, creating an action potential.
• Order the steps of chemical transmission at the synapse.

  1️⃣ Electrical impulse reaches presynaptic terminal

  2️⃣ Neurotransmitters are released from synaptic vesicles

  3️⃣ Neurotransmitters diffuse across the synapse

  4️⃣ Neurotransmitters bind to postsynaptic receptor sites

  5️⃣ Electrical impulse is regenerated in the postsynaptic neuron
• Neurotransmitters are reabsorbed into the presynaptic neuron after completing their task.
• Acetylcholine is a neurotransmitter that causes muscle contraction.
• Neurotransmitters can have either excitatory or inhibitory effects on neighboring neurons.
• Serotonin is a neurotransmitter that causes inhibition, making neurons less likely to fire.
• Adrenaline makes neighboring neurons more positively charged, increasing their likelihood to fire.