Nerve system

• What is the primary function of the nervous system?

  To help organisms respond to the environment
• What are the three main types of neurones?

  Sensory, motor, and relay neurones
• How do sensory neurones function in the nervous system?

  They transmit nerve impulses from receptors to the central nervous system (CNS)
• What role do motor neurones play in the nervous system?

  They transmit nerve impulses from the CNS to effectors
• What is the function of relay neurones?

  They transmit nerve impulses between sensory neurones and motor neurones
• What happens when a stimulus is detected by receptor cells?

  A nerve impulse is sent along a sensory neurone
• What occurs when a nerve impulse reaches the end of a neurone?

  Chemicals called neurotransmitters transfer the information to the next neurone
• What does the CNS do with the information it processes?

  It decides what to do about it and sends impulses along motor neurones to an effector
• What is the sequence of events from stimulus detection to response?

  1. Stimulus detected by receptors
  2. Nerve impulse sent along sensory neurone
  3. CNS processes information
  4. Impulses sent along motor neurones to effectors
  5. Effector produces a response
• What are nerve impulses also called?

  Action potentials
• How do sensory receptors convert stimulus energy?

  They convert it into electrical energy in the form of nerve impulses
• What is the role of sensory receptors in the nervous system?

  They act as transducers, converting one form of energy into another
• What is the potential difference in a neurone at rest called?

  Resting potential
• What generates the resting potential in a neurone?

  Sodium-potassium pumps and potassium ion channels
• What happens to the neurone's membrane during depolarisation?

  The membrane becomes more permeable to sodium ions
• What is the threshold level for triggering an action potential?

  About -55 mV
• What is hyperpolarisation in a neurone?

  When the potential difference becomes more negative than the resting potential
• What occurs during repolarisation of a neurone?

  Potassium ions diffuse out of the neurone
• What is the refractory period in a neurone?

  The period during which the neurone cannot be excited again immediately
• What are the steps of an action potential?

  1. Stimulus excites the neurone
  2. Sodium ion channels open
  3. Depolarisation occurs
  4. Sodium channels close, potassium channels open
  5. Repolarisation occurs
  6. Hyperpolarisation occurs
  7. Resting potential is restored
• How does an action potential move along a neurone?

  It moves as a wave of depolarisation
• What is saltatory conduction?

  When the impulse jumps from node to node in myelinated neurones
• What is the role of nodes of Ranvier in myelinated neurones?

  They are where depolarisation occurs
• How does a bigger stimulus affect action potentials?

  It causes them to fire more frequently
• What is the function of a synapse?

  It is the junction between a neurone and another cell
• What is the tiny gap between cells at a synapse called?

  Synaptic cleft
• What does the presynaptic neurone contain at the synapse?

  A synaptic knob filled with neurotransmitters
• What happens when an action potential arrives at the end of a neurone?

  Neurotransmitters are released into the synaptic cleft
• What is depolarisation in the context of action potentials?

  Depolarisation is when the voltage difference across a cell's membrane becomes smaller.
• What happens during repolarisation of a cell's membrane?

  During repolarisation, the voltage difference across the cell's membrane increases again.
• What is a synapse and its components?

  • A synapse is the junction between a neurone and another neurone or an effector cell.
  • It includes:
  • Synaptic cleft (the gap between cells)
  • Presynaptic neurone (before the synapse)
  • Synaptic knob (contains synaptic vesicles with neurotransmitters)
• What is the tiny gap between cells at a synapse called?

  The tiny gap is called the synaptic cleft.
• What does the presynaptic neurone contain that is crucial for neurotransmission?

  The presynaptic neurone contains synaptic vesicles filled with neurotransmitters.
• What triggers the release of neurotransmitters into the synaptic cleft?

  The arrival of an action potential at the end of a neurone triggers the release of neurotransmitters.
• What happens to neurotransmitters after they bind to receptors on the postsynaptic membrane?

  They may trigger an action potential, cause muscle contraction, or cause hormone secretion.
• How are neurotransmitters removed from the synaptic cleft?

  Neurotransmitters are taken back into the presynaptic neurone or broken down by enzymes.
• What is an example of a neurotransmitter found at cholinergic synapses?

  Acetylcholine (ACh) is an example of a neurotransmitter at cholinergic synapses.
• What enzyme breaks down acetylcholine at cholinergic synapses?

  The enzyme that breaks down acetylcholine is called acetylcholinesterase (AChE).
• What are the steps involved in neurotransmitter release at a synapse?

  1. Action potential arrives at the presynaptic neurone.
  2. Voltage-gated calcium ion channels open.
  3. Calcium ions diffuse into the synaptic knob.
  4. Calcium influx causes synaptic vesicles to fuse with the presynaptic membrane.
  5. Neurotransmitter is released into the synaptic cleft via exocytosis.
• What occurs when neurotransmitters bind to receptors on the postsynaptic membrane?

  This binding opens sodium ion channels in the postsynaptic neurone.