Neurons and synaptic transmissions

• What are the three main types of neurons?

  Sensory, relay, and motor neurons
• How do neurons transmit signals?

  They transmit signals electrically and chemically
• What is a neuron?

  • Basic building blocks of the nervous system
  • Transmit electrical and chemical signals
  • Found in the central nervous system (CNS)
• What do sensory neurons do?

  They carry nerve impulses from the PNS to the CNS
• What is the role of relay neurons?

  They connect sensory neurons to motor neurons
• Where are motor neurons found?

  They are found in the CNS and have long axons in the PNS
• What are the main features of neurons?

  • Cell body (soma): contains nucleus
  • Dendrites: receive impulses from other neurons
  • Axon: carries impulses away from the cell body
  • Myelin sheath: protects axon and speeds up impulses
  • Nodes of Ranvier: gaps that speed up nerve impulses
• What is the function of the myelin sheath?

  It protects the axon and speeds up the nerve impulse
• What happens during the resting state of a neuron?

  The inside of the axon is negatively charged compared to the outside
• What triggers an action potential in a neuron?

  The entry of sodium ions (Na+) into the axon
• What is synaptic transmission?

  The process by which nerve impulses are transmitted across the synapse
• What are neurotransmitters?

  Chemical messengers released into the synapse
• What happens when a neurotransmitter is released?

  It affects the postsynaptic membrane and changes its function
• What is the role of enzymes in neurotransmitter action?

  They break down neurotransmitters to regulate their effects
• What are the effects of excitatory and inhibitory neurotransmitters?

  • Excitatory neurotransmitters (e.g., acetylcholine): increase action potential chances
  • Inhibitory neurotransmitters (e.g., GABA): decrease action potential chances
• What is summation in the context of neurotransmitters?

  It is the addition of individual signals to determine if a neuron will fire
• What is temporal summation?

  The summing of excitatory signals at one synapse in quick succession
• What is spatial summation?

  The summation of excitatory and inhibitory signals from multiple sites
• How do SSRIs affect serotonin levels?

  • Slow down the reuptake of serotonin
  • Ensure serotonin stays active longer in the synapse
• What is the knee jerk reflex an example of?

  A reflex arc involving a rapid, involuntary response
• What is the role of the effector in the knee jerk reflex?

  It causes the knee to bend or kick
• What is the function of a receptor in the knee jerk reflex?

  It detects the stimulus
• What is the role of the spinal cord in the knee jerk reflex?

  It passes the message from sensory neurons to relay neurons
• What happens during depolarisation of a neuron?

  The neuron's membrane becomes more permeable to sodium ions
• What occurs during repolarisation of a neuron?

  The neuron returns to its normal electrical condition
• What is the significance of the nodes of Ranvier?

  They speed up the nerve impulse by allowing it to jump across gaps
• How does the structure of a neuron relate to its function?

  The long axon allows for the rapid transmission of impulses
• What is the basic structure shared by all neurons?

  They all have a cell body, dendrites, and an axon
• What is the role of the presynaptic terminal button?

  It communicates with the next neuron at the synapse
• What is the effect of an excitatory neurotransmitter on a postsynaptic neuron?

  It increases the chance of an action potential being generated
• What is the effect of an inhibitory neurotransmitter on a postsynaptic neuron?

  It decreases the chance of an action potential being generated
• How does the balance of excitatory and inhibitory inputs affect neuron firing?

  The net effect determines if the neuron will fire or not
• What is the role of the postsynaptic receptor site?

  It is where neurotransmitters bind to affect the postsynaptic neuron
• What happens to neurotransmitters after they have acted on the postsynaptic neuron?

  They are broken down by enzymes and reabsorbed by the presynaptic neuron
• What is the significance of the breakdown of neurotransmitters?

  It regulates their effect and prevents prolonged action
• How do psychoactive drugs like SSRIs affect neurotransmitter activity?

  They alter the reuptake of neurotransmitters, affecting mood regulation
• What is the relationship between serotonin levels and mood disorders?

  Low levels of serotonin are linked to mood disorders like depression
• What is the role of the muscle spindle organ in the knee jerk reflex?

  It acts as a receptor that detects the stimulus
• What is the function of the motor neuron in the knee jerk reflex?

  It carries the message to the effector organ
• What is the role of the relay neuron in the knee jerk reflex?

  It transmits the message from sensory neurons to motor neurons