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 the main component of the neurone's cell body?

  The nucleus
• What do mitochondria provide for neurones?

  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
• What are the three types of neurones?

  Sensory, motor, and relay
• What do motor neurones transmit signals to?

  Muscles and glands in the body
• What do sensory neurones transmit impulses from?

  Receptors to the central nervous system
• Where are relay neurones located?

  Within the central nervous system
• What do relay neurones transmit impulses between?

  Sensory neurones and 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 state of nerve cells?

  When they are not actively transmitting impulses
• What causes the negative charge inside a nerve cell at resting potential?

  Imbalance between sodium and potassium ions
• What is the value of the resting potential?

  • 70mV
• What happens to the neurone cell membrane upon stimulation?

  It becomes depolarised
• What triggers the opening of sodium ion channels?

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

  • 55mV
• What occurs at the end of depolarisation?

  Start of repolarisation
• What causes repolarisation in a neurone?

  Closing of sodium channels and opening of potassium channels
• What is hyperpolarisation?

  When potential difference exceeds resting potential
• How is resting potential restored?

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

  Time when neurone cannot be excited
• How does the action potential travel along the neurone?

  As a wave of depolarisation
• What are synapses?

  Junctions between two neurones
• What happens to the presynaptic membrane upon arrival of an action potential?

  It depolarises
• What do calcium ions cause in the neurone?

  Fusion of synaptic vesicles with the membrane
• What neurotransmitter is mentioned in the study material?

  Acetylcholine
• What happens when neurotransmitter binds to receptors on the postsynaptic membrane?

  Opens cation channels for sodium ions

  
• What is an excitatory postsynaptic potential (EPSP)?

  When neurotransmitter originates from excitatory neurone
• What happens during an inhibitory postsynaptic potential (IPSP)?

  Chloride ions enter, causing hyperpolarisation
• What role do digestive enzymes play in the synaptic cleft?

  Break down neurotransmitter to prevent overstimulation

  
• What happens to neurotransmitter after it is broken down?

  It is taken up by the presynaptic membrane and reused
• What ensures that action potentials travel in one direction only?

  Presence of receptors and refractory period
• What are cells specialized for detection of stimuli called?

  Receptors
• What are sense organs like the eye specialized for?

  Detection of stimuli