Structure and Function of Sensory, Relay and Motor Neurons

• Neurons - conduct nerve impulses by transmitting signals electronically and chemically with primary means of communication
• Dendrites - receive signals from neurons or other receptor cells and are typically connected to the cell body
• Axon - A long slender fibre that carries nerve impulses in the form of electrical signals known as action impulses
• Myelin Sheath - A protective layer around most axons that insulates them, speeding up the transmission of electrical impulses.
• Axon terminal - connects neurons to other neurons or organs, using a process called synaptic transmission
• Sensory Neuron - carry impulses from receptor cells to the CNS, allowing us to feel sensations. Some stop at the spinal cord to trigger quick reflexes (knee jerk).
• Relay Neurons - found in the brain and spinal cord. They connect sensory and motor neurons to allow communication
• Motor Neurons - found in the CNS and control muscle movement. They release neurotransmitters that bind to muscle receptors to trigger a response
• Synaptic Gap - small space between two neurons at a synapse where neurotransmitters are released from the presynaptic neuron to carry the signal to the postsynaptic neuron
• Fight or Flight Process:

  • stressful situations entered
  • Amygdala activation, send distress signals to hypothalamus
  • hypothalamus activates the SAM Pathway, stimulating the adrenal medulla and Sympathetic Nervous System
  • Adrenal Medulla secretes adrenaline and noradrenaline causing physiological changes
• Physiological Changes during F/F:

  • Increased heart rate - increase blood flow and adrenaline to body
  • Increased breathing rate - increase oxygen intake per breath
  • Pupil dilation - increase light intake and vision
  • Sweat production - regulate temperature
• Response to chronic (ongoing) stressors: if the brain continues to perceive something as a job (eg. a stressful job) a second system kicks - the HPA axis

  • Hypothalmus
  • Pituitary gland
  • Adrenal gland
• HPA (H) - the hypothalamus releases a chemical messenger CRH into the bloodstream
• HPA (P) - CRH causes the pituitary to release ACTH, which is then transported to the adrenal gland via the bloodstream
• HPA (A) - ACTH stimulates the adrenal cortex, releasing cortisol, responsible for several fight-or-flight responses. some are positive (quick bursts of energy), and some are negative (lowered immune system)
• why may F/F be unhelpful today:

  • F/F triggers, adrenaline
  • Sweat, quick reaction time etc
  • unhelpful during real life task and fighting irl isn't good