Grey Matter

• What are nerve cells called?

  Neurones
• What role do neurones play in the nervous system?

  They coordinate communication within the nervous system
• What is contained within the cell body of a neurone?

  Nucleus and organelles like mitochondria
• What is the function of mitochondria in neurones?

  They provide energy in the form of ATP
• What are dendrites involved in?

  Conducting impulses towards the cell body
• What do axons do?

  Conduct impulses away from the cell body
• How many types of neurones are there?

  Three types
• What are the three types of neurones?

  Sensory, motor, and relay neurones
• What is the function of motor neurones?

  Transmit signals from the CNS to muscles
• What do sensory neurones do?

  Transmit impulses from receptors to the CNS
• Where are relay neurones located?

  Within the central nervous system
• What is the role of relay neurones?

  Transmit impulses from sensory to motor neurones
• How does the diameter of nerve cells affect impulse transmission?

  Wider diameter transmits impulses more quickly
• What is myelination?

  A layer of fatty substance around neurones
• How does myelination affect impulse speed?

  Increases speed by acting as an insulator
• What is saltatory conduction?

  Impulse jumps between nodes of Ranvier
• What is the resting potential of a neurone?

  • 70mV
• What causes the resting potential in neurones?

  Imbalance between sodium and potassium ions
• What do sodium-ion pumps do?

  Remove sodium ions from the cell cytoplasm
• How do potassium ions move during resting potential?

  They diffuse out through ion channels
• What happens when potassium ion forces are balanced?

  No net movement occurs, resting potential is reached
• What occurs upon stimulation of a neurone?

  The neurone cell membrane becomes depolarised
• What triggers the opening of sodium ion channels?

  Excitation of the neurone cell by stimulus
• What is the threshold potential for action potential?

  • 55mV
• What happens during depolarisation?

  Membrane potential becomes less negative
• What occurs during repolarisation?

  Sodium channels close and potassium channels open
• What is hyperpolarisation?

  Potential difference becomes greater than resting potential
• How is resting potential restored?

  With the help of sodium-potassium pump
• What is the refractory period?

  Period when neurone membrane cannot be excited
• How does an action potential travel along a neurone?

  As a wave of depolarisation
• What are synapses?

  Junctions between two neurones
• What happens when an action potential arrives at a synapse?

  Presynaptic membrane depolarises and calcium channels open
• What causes the release of neurotransmitters?

  Fusion of synaptic vesicles with presynaptic membrane

  
• What do neurotransmitters do at the postsynaptic membrane?

  Bind to receptors and open cation channels
• What is an excitatory postsynaptic potential (EPSP)?

  Caused by neurotransmitters from excitatory neurones
• What is an inhibitory postsynaptic potential (IPSP)?

  Caused by chloride ions entering the postsynaptic membrane
• What role do digestive enzymes play in synapses?

  Break down neurotransmitters to prevent overstimulation
• What happens to neurotransmitters after they are broken down?

  They are taken up by the presynaptic membrane and reused
• How does the presence of receptors affect synaptic transmission?

  Ensures action potential travels in one direction only
• What are cells specialized for detection of stimuli called?

  Receptors