Neuronal Communication, The Brain, and Animal Responses

• What is a myelin sheath made of?

  layers of the plasma membrane
• Why is the Pacinian corpuscle described as a transducer?

  it converts one form of energy into another
• Why does the deformation of the plasma membrane of the tip of the neuron cause the membrane to become more permeable to sodium ions?

  • the deformation increases pressure causing sodium ion channels to open
  • and temporary gaps to appear between the phospholipids bilayer
• Explain what the ‘All-or-Nothing’ law means.

  If the stimulus is not intense enough to reach or exceed the threshold potential, it wont generate an action potential as the depolarisation of the membrane is insufficient
• How is the strength and intensity of a stimulus is communicated to the brain.

  • it is represented by the frequency of the action potential
  • the higher frequency of action potentials, the stronger/intense the stimulus
• What is convergence in the context of synapses?

  It allows action potentials from several neurones to be passed to a single neurone.
• What is divergence in the context of synapses?

  It allows action potentials from a single neurone to be passed to several neurones.
• What types of synapses exist and what do they do?

  • inhibitory
  • stimulatory
  • allow action potentials to follow a specific path
• Name one chemical that transfers a nerve impulse from one neurone to another in the neuromuscular junction in mammals.

  Acetylcholine (ACh)
• Where, precisely, are acetylcholine receptors found?

  Post-synaptic membrane
• What type of molecule forms ion channels?

  Protein (glycoprotein)
• What is the name of the space between two neurons which the impulse is diffused across by a neurotransmitter.

  Synaptic cleft
• Name an enzyme found in the neuromuscular junction of mammals.

  Acetylcholine esterase (ACh esterase)
• State the structural similarities of a sensory and a motor neurone.

  • dendrite
  • axon
  • cell body
  • myelin sheath / schwann cell/ node of Ranvier
  • Voltage-gated channels
• What type of motor neurone stimulates contraction in a skeletal muscle?

  Somatic
• Explain why a spinal cord injury (SCI) causes both paralysis and loss of feeling below the site of the injury.

  • both sensory and motor neurones are damaged
  • impulse cannot reach muscles / pass through motor neurone
  • prevents impulse transmission, through sensory neurone / from receptors
• Define Pacinian Corpuscle:

  A pressure sensor that detects changes in pressure on the skin
• The Pacinian corpuscle is only sensitive to changes in pressure that deform the rings of connective tissue. When pressure is constant, they stop responding.
• Name this type of neurone.

  Sensory neurone

  
• Name the this type of neurone.

  Motor neurone

  
• Name this type of neurone.

  Relay neurone

  
• The cells of the body need to communicate with one another.

  State the name given to this process of communication.

  Cell signalling
• Two conclusions that can be drawn about the type of nervous response when it involves the relay neurone.

  • involuntary response = does not use the somatic nervous system
  • reflex response = only involves a few neurones