Biology neuronal and hormonal communication

• How can modifying the post-synaptic membrane increase the likelihood of firing an action potential?

  By adding more receptors to increase sensitivity to acetylcholine
• How does aldosterone affect the kidneys?

  It increases sodium absorption and water retention
• What can severe hypoglycemia lead to?

  Impairment of brain function, confusion, seizures, unconsciousness, and even death.
• What is a Pacinian corpuscle?

  A pressure sensor found in the skin

  
• What is a sensory receptor?

  Cells that respond to stimuli in the internal or external environment
• What is a transducer in the context of sensory receptors?

  A cell that converts one form of energy into another
• How do Pacinian corpuscles detect pressure?

  High pressure opens channels allowing Na⁺ to travel through

  
• What type of energy change do light sensory cells in the retina detect?

  Change in light intensity
• What do temperature receptors in the skin detect?

  Change in temperature and heat
• What do vibration receptors in the cochlea of the ear detect?

  Change in sound
• What do hair cells in the inner ear detect?

  Movement
• What do muscle spindles detect?

  Change in muscle length
• What do olfactory cells in the epithelium detect?

  Chemicals in the air
• What do taste buds on the tongue detect?

  Chemicals in food
• What is the function of sensory neurones?

  • Carry action potentials from sensory receptors to the CNS
  • Transmit signals related to stimuli
• What is the function of motor neurones?

  • Carry action potentials from the CNS to effectors
  • Control muscle contractions and glandular secretions
• What is the function of relay neurones?

  • Join sensory neurones to motor neurones
  • Facilitate communication within the CNS

  
• What is the role of sodium and potassium pumps in neurones?

  They actively transport Na⁺ out of the cell and K⁺ into the cell
• What happens when the membrane of a neurone is deformed?

  Sodium channels open, allowing Na⁺ to diffuse into the cell
• What is the resting potential of a neurone?

  The potential difference across the membrane while the neurone is at rest
• What occurs during depolarization of a neurone?

  The membrane becomes less negative with respect to the outside
• What is positive feedback in the context of action potentials?

  A mechanism that increases change, taking the system further away from optimum
• What are the stages of an action potential?

  1. Resting potential at -60 mV
  2. Na⁺ channels open, depolarization occurs
  3. Positive feedback leads to rapid influx of Na⁺
  4. K⁺ channels open, repolarization occurs
  5. Hyperpolarization occurs
  6. Return to resting potential

  
• What is the role of myelin in neurones?

  It speeds up the rate of conduction of action potentials
• What is a cholinergic synapse?

  A synapse that uses acetylcholine as its neurotransmitter

  
• What are the steps of transmission across a synapse?

  1. Action potential arrives at synaptic bulb
  2. Calcium channels open
  3. Calcium ions diffuse in
  4. Vesicles fuse with pre-synaptic membrane
  5. Acetylcholine is released
  6. Acetylcholine binds to receptors on post-synaptic membrane
  7. Sodium channels open, creating a generator potential
  8. If sufficient, a new action potential is created
• What is summation in the context of synapses?

  When the effects of several excitatory post-synaptic potentials are added together
• What are inhibitory post-synaptic potentials (IPSP)?

  They cause hyperpolarization of the post-synaptic neurone
• What is the endocrine system?

  • A communication system using hormones as signaling molecules
  • Hormones are released by endocrine glands into the blood

  
• What are target cells in the endocrine system?

  Cells that possess specific receptors for hormones on their plasma membrane
• What are the types of hormones?

  • Protein and peptide hormones: bind to cell surface and release second messengers
  • Steroid hormones: pass through the membrane and affect DNA directly
• What is the role of first and second messengers in hormone signaling?

  First messengers are hormones that bind to receptors, second messengers are released inside the cell
• How do non-steroidal hormones act?

  They act via a G protein in the membrane
• What is the function of G proteins in hormone signaling?

  They activate effector molecules when a hormone binds to the receptor
• Where is DNA located in a cell?

  In the nucleus
• What type of cells receive endocrine signals?

  Target cells
• How can target cells be organized?

  They may be grouped together in target tissue
• What is required for target cells to respond to non-steroidal hormones?

  They must possess a specific receptor on their plasma membrane
• What happens if a cell contains a receptor for a hormone?

  The body can respond to the signal
• What are non-steroidal hormones classified as?

  First messengers