synapses + reflexes

• what are sensory receptors?

  groups of cells that can detect a change in environment, different receptors detect different stimuli
• what do the receptors in your skin detect?

  pressure and temperature change
• what happens when a stimulus is detected by receptors?

  the information is converted to a nervous (electrical) impulse and sent along sensory neurones to the CNS
• what is a synapse?

  the connection between 2 neurones
• what is a neurotransmitter?

  a chemical that transfers nerve signals, they diffuse (move) across the gap
• what do neurotransmitters do after transferring the nerve signals?

  they set off a new electrical signal in the next neurone
• what slows down the transmission of a nervous impulse?

  the transmission of a nervous impulse is very fast but it is slowed down a bit at the synapse as the diffusion of neurotransmitters across the gap takes time
• where do the neurones in reflex arcs go?

  through the spinal cord or through an unconscious part of the brain
• what happens when a stimulus is detected by receptors?

  impulses are sent along a sensory neurone to a relay neurone in the CNS
• what happens when an impulse reaches a synapse between the sensory neurones and the relay neurone?

  they trigger neurotransmitters to be released. These cause impulses to be sent along the relay neurone
• what happens when an impulse reaches a synapse between the relay neurones and the motor neurone?

  they trigger neurotransmitters to be released. These cause impulses to be sent along the motor neurones
• where do the impulses go once they have travelled along the motor neurone?

  to the effector (muscle or gland)
• what is therapeutic cloning?

  a process that produces an embyro with the same genes as the patient. Stem cells taken from this embryo will have the same DNA as the patient meaning their body will not reject the stem cells made from the embryo's stem cells.
• how do synapses work?

  1. the electrical impulse reaches the end of the neurone before the synapse.
  2. this triggers the release of neurotransmitters.
  3. the neurotrasmitters diffuse across the gap between the neurone.
  4. the neurotrasmitters bind to receptors on the next neurone.
  5. the presence of the neurotransmitter causes the production of a new electrical impulse in the next neurone.
• what are examples of reflex arcs?

  • sneezing
  • blinking
  • dropping hot objects
• what does the sensory neurone do?

  carries the signal in the form of an electrical impulse to the CNS.
• what does the relay neurone do?

  (in the CNS) relays the electrical impulse from the sensory neurone to the appropriate motor neurone.
• what does the motor neurone do?

  carries the electrical impulse from the CNS to an effector.