T8: 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 cell body of a neurone?

  The nucleus
• What organelles are found within the cytoplasm of neurones?

  Mitochondria
• What is the energy form provided by mitochondria for active transport in neurones?

  ATP
• What are dendrites involved in?

  Conducting impulses towards the cell body.
• What is the function of axons in neurones?

  They conduct impulses away from the cell body.
• What are the three types of neurones?

  • Sensory neurones
  • Motor neurones
  • Relay neurones
• How do the functions of sensory, motor, and relay neurones differ?

  They differ by the position of the cell body within the neurone.
• What is the role of motor neurones?

  They transmit electrical signals from the central nervous system to muscles and glands.
• What do sensory neurones transmit impulses from?

  From receptors to the central nervous system.
• Where are relay neurones located and what is their function?

  They are located within the central nervous system and transmit impulses from sensory neurones to motor neurones.
• How does the diameter of nerve cells affect impulse transmission?

  Wider diameter nerve cells transmit impulses more quickly.
• What is myelination and how does it affect impulse speed?

  Myelination is a layer of fatty substance that increases the speed of impulses by acting as an electrical insulator.
• What is saltatory conduction?

  It is the process where action potentials jump between gaps in the myelin sheath called nodes of Ranvier.
• What is the resting state of nerve cells characterized by?

  It is characterized by the polarization of the neurone membrane.
• What causes the negative charge inside a nerve cell during the resting state?

  An imbalance between sodium ions and potassium ions.
• What is the value of the resting potential in a neurone?

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

  It becomes depolarized.
• What triggers the opening of sodium ion channels during depolarization?

  The excitation of the neurone cell triggered by a stimulus.
• What is the threshold potential that triggers further sodium channel openings?

  • 55mV
• What is the potential difference at the end of depolarization?

  +30mV
• What occurs during repolarization of the neurone?

  Sodium ion channels close and potassium ion channels open.
• What is hyperpolarization?

  It occurs when the potential difference becomes greater than the resting potential.
• How is the resting potential restored after hyperpolarization?

  Through the sodium-potassium pump which returns the potential difference to -70mV.
• What is the refractory period in neurones?

  It is a short period during which the neurone membrane cannot be excited.
• How does the action potential travel along the neurone?

  As a wave of depolarization where sodium ions move to the adjacent resting region.
• What are synapses?

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

  It depolarizes, causing calcium channels to open.
• What is the role of calcium ions in the neurone during synaptic transmission?

  They cause the fusion of synaptic vesicles filled with neurotransmitters.
• What neurotransmitter is mentioned in the context of synaptic transmission?

  Acetylcholine
• What happens after neurotransmitters are released into the synaptic cleft?

  They bind to receptors on the postsynaptic membrane.
• What is created when an excitatory neurone releases neurotransmitters?

  An excitatory postsynaptic potential (EPSP).
• What occurs when inhibitory neurones release neurotransmitters?

  Chloride ions enter, causing hyperpolarization of the postsynaptic membrane.
• What role do digestive enzymes play in the synaptic cleft?

  They break down neurotransmitters to prevent overstimulation of the postsynaptic membrane.
• What happens to neurotransmitters after they are broken down?

  They are taken up by the presynaptic membrane and reused.
• What ensures that the action potential can only travel in one direction?

  The presence of receptors on one side of the synapse and the refractory period.
• What are cells specialized for detection of stimuli called?

  Receptors
• What are sense organs such as the eye specialized for?

  Detection of stimuli.
• What is the role of digestive enzymes in the synaptic cleft?

  They break down neurotransmitters to prevent overstimulation of the post-synaptic membrane.