Main Page

Lecture Notes
Chapter 4

• Signaling
• Information transfer
  • Within cells
  • Between cells

• Neuroglia
  • Astrocytes
  • Myelin
    • Oligodendrocytes
    • Schwann cells
• Neurons
  • Sensory
  • Interneuron
  • Motor

• Soma
• Axon
• Terminals
• Dendrites

Like any other cell

• Nucleus, mitocondria, plasma membrane

plasma membrane

• Communication
• Connect to:
  • Dendrites
  • Soma

• Oligodendrocytes (CNS)
• Schwann cells (PNS)

• Microtubules ("axon escalators")
  • Cytoskeleton
• Neurotransmitters
• Proteins

Connects with:

• Dendrites (common)
• Soma (common)
• Other axons (rare)

• Chemical transmitters
  • Neurotransmitters
• Electrical signals
• Excitatory or inhibitory signals

• Presynaptic cell
  • Transmitter
• Postsynaptic cell
  • Receiver
• Chemical and electrical synapses

• Demonstrates chemical (neurotransmitter) synapse

• Presynaptic
  • Axon terminal (contains neurotransmitter)
• Postsynaptic
  • Dendrite or soma

• Space between pre- and postsynaptic elements

1. Axon terminal releases neurotransmitter
2. Neurotransmitters diffuse across synaptic cleft
3. Postsynaptic receptors uptake neurotransmitter
4. Signal travels to next neuron (unidirectional!)

• Cell-to-cell pores

• Mediates signalling
• Low resistance pathways

• Neurons are physically coupled
• No synaptic cleft to diffuse across

• Lucifer yellow

• -40mV to -90mV
• Negative relative to extracellular

Depolarized

• Less negative than resting potential

• More negative than resting potential

• "Firing" of the axon

• Critical point

All or none

• Either threshold is reached, or nothing happens
• Can't stop an action potential

• Larger depolarizing stimulus, greater firing rate

• Porous skin of neuron
• Intracellular fluid
• Extracellular fluid
• Ion channels
  • Potassium
  • Sodium
• Balance of charge
  • Intracellular more negative than extracellular
  • Resting potential (negative)

Action Potential

• Initiation phase
  • Sodium channels open
• Depolarization phase
  • Sodium ions enter
    • Concentration gradient
    • Electrical gradient
  • Repolarization phase
    • Sodium channels close
    • Potassium channels open
      • Potassium ions exit
  • Sodium-potassium pump

• e.g., walking, swimming, peristaltic movement

• Contract, relax, contract, relax...

• Different neurons innervate different muscles

• Two neurons
• Reciprocal inhibition
• Postinhibitory rebound
  • Cell becomes more excitable after hyperpolarization (threshold is reduced)

• Learning based on neuronal structure
• Input units
  • Sensory neurons
• Hidden units
  • Interneurons
• Output units
  • Motor neurons

• No

• Simulation
• Metaphore
• Hypothesis testing

• Brain
• Spinal cord
• Non-regenerative

• Nerves outside the CNS
• Regenerative

• Sensory neurons
  • Carry information from sensory organs to CNS
• Interneurons
  • Only in CNS
  • Carry information from one neuron to another
  • Organize and integrate information
• Motor neurons
  • Carry information to muscles and glands

• Muscles attached to bones
• Externally observable movements
• Neurons extend directly from CNS to muscle

• Visceral muscles and glands
• Indirect neuronal action from CNS to ganglion to target site
• Sympathetic division
  • Immediate responses to stressful stimuli
• Parasympathetic division
  • Regenerative, energy-conserving processes

• Hydrogen dipoles
• Normally randomly positioned

• Repositions hydrogen dipoles

• Takes time for dipoles to re-position after magnetic field turned off

• Long axis
• 100 to 2000 ms in biological tissue

• Perpendicular to long axis
• 30 to 300 ms in biological tissue

• Ascending tracts
  • Somatosensory information to brain
• Descending tracts
  • Motor-control information from brain
  • Central pattern generators
    • Interneurons
    • Brain influences
  • Spinal reflexes
    • Sensory neuron
    • Interneuron
    • Motor neuron
    • e.g., flexion reflex

 

• Cranial nerves

• Postural reflexes
  • Balance
• Vital reflexes
  • Breathing, heart rate, etc.
• Mid-brain
  • Basic movements
  • Connections to CPGs in spinal cord
• Thalamus
  • "Relay station"
  • Connects parts of the brain
  • Sensory tracts from brainstem terminate here
    • Output then to cerebral cortex

 

Cerebellum

• Motor control
• Rapid, powerful movements
• Information processor
  • Input from sensory organs
  • Coordinates complex movement

• Grey matter
  • Unmyelinated
• Motor control
• Slow, precise movements

• Amygdala
  • Scent
  • Drives and emotion
• Hippocampus
  • Memory hypothalamus
• Regulates internal environment of the body
  • Autonomic nervous system
  • Hormones
  • Drive states

 

• Input from sensory nerves (via thalamus)
  • Visual area
  • Auditory area
  • Somatosensory area
• Back

• Sends axons to motor neurons in brainstem and spinal cord
• Middle

• Perception, thought, decision making
• Receives input
  • Sensory areas
  • "Lower brain" structures
• Front

• Connects hemispheres

• Sensory neurons from right side input to left hemisphere and vise versa
• Motor neuron from left hemisphere to right side of body
• Unified sensation and movement due to corpus callosum

• Left hemisphere
  • e.g., Speech
• Right hemisphere
  • e.g., Spatial tasks

• Right visual field to left hemisphere
• Left visual field to right hemisphere
• Corpus callosum would transfer information

• Visual picture in left visual field
• Test: touch object with left hand
  • Success!
• Test: name object
  • Failure!

• Related to neurotransmitters

• Endocrine glands
• Internal organs
• Brain

• Long-term
  • e.g., Anatomical sex differences, growth, bone strength
• Short-term
  • e.g., Fight-or-flight response, healing, menstrual cycle

• Peptides
  • Pituitary gland
  • Donšt pass cell membranes easily
  • Act like neurotransmitters
    • Open/close membrane channels
    • Change ion concentrations
• Steroids
  • Adrenal cortex and gonads
  • Pass cell membranes easily
  • Effect in cell nucleus
    • Genes
    • Production/reduction of certain proteins
  Brain control of hormones
  • Pituitary
    • Posterior
      • Part of the brain
      • Connected to neurosecretory cells in hypothalamus
      • Produces hormone releasing factors
    • Anterior
      • Triggered by releasing factors
      • Produces pituitary hormones
      • Releases hormones into bloodstream