Adaptive Brain
Papers at journal club will be part of the exam
Textbook: Purves 5th ed
20 min presentation at journal club
5-6 MCs per lecture and 10 MCs on papers
LECTURE 1: Chapter 1
Nervous system cells can be divided into 2 categories
o Neurons
o Neuroglia supporting cells
Mitochondria concentrated at the synapses of neurons while ER is not present in
axons or dendrites
Dendrites are primary input for synaptic input from axons of other neurons
Dendrites have high ribosome content and specific cytoskeletal proteins
Neurons that lack dendrites are innervated by the axons of one or few neurons
o Their capacity to integrate information from diverse sources is limited
Neurons with elaborate and more dendritic branches are innervated by a large
number of other neurons
o For greater integration of information
Number of in puts to a neuron refer to its convergence and number of targets
innervated by a neuron refers to its divergence
Nerve cells integrate and relay information from other neurons in a neuronal circuit
Axons to dendrites make synaptic contact presynaptic neuron is adjacent to a
specialized region in the post synaptic receptors
, Neurons communicate via releasing molecules into the synapse and taking them up
neurotransmitters
Projection neurons have long axons for distant targets spinal cord to leg nerve
(1m)
Interneurons and projection neuron axons locally branch to innervate multiple post
synaptic sites on many neurons
Axons convey electric signals over distances by a self-regenerating wave of electric
activity called action potential
Chemical synapses presynaptic terminal and postsynaptic specializations
Electrical synapses mediated by gap junctions rare in normal CNS but present
in developing CNS synchronises local networks of neurons
Glial cells support nerve cells and also contribute to development of adult nervous
system repair, acting as stem cells when required
Mitochondria concentrated in synapses of neurons
The filament, tubules, motors and scaffolding proteins in glial and neuronal cells
o Migration of nerve cells
o Growth of axons and dendrites
o Trafficking and positioning of membrane components
o Exocytosis and endocytosis for synaptic transmission
Synaptic vesicles contain neurotransmitters and neuroactive molecules located
close to the presynaptic membrane
Glial cells functions
o Maintaining ionic concentrations of nerve cells
o Modulating rate of neuronal propagation
o Modulating synaptic action
o Providing scaffold for neuronal development
o Recovery from neural injury
o Interface between brain and immune system
, Glial cell types
o Astrocytes
Restricted to the CNS
Maintain appropriate chemical environment for neuronal signalling
including formation of BBB
o Oligodendrocytes
Restricted to CNS
Produce myelin for neurons
In some cases can regenerate themselves
o Schwann cells
In PNS
Produce myelin
In some cases can regenerate themselves
o Microglial cells
Derived mainly from hematopoietic but also neural precursor cells
Scavenger cells remove cellular debris
Secrete cytokines for local inflammation
Glial stem cells also in the brain (subset of astrocytes) regenerate glial cells and
sometimes even neurons also can renew themselves
o Found in subventricular zone
o And in ventricular zone
Oligodendrocyte precursors scattered through white matter give rise to
oligodendrocytes, astrocytes and sometimes neurons
Golgi method of visualisation staining with silver salts allowed for observing
neuronal cells
o Now use fluorescent dyes
, LECTURE 2: Electric signals of Nerve cells
Neurons communicate via electric signals
Neurons are poor generators and conductors of electricity because they are made of
lipids
Mechanism to overcome this
o Lipid bilayers are not permeable through the layer they are only
permeable via pores
o So neurons have pores that allow ion exchange
There is selective permeability for these ions
Electrical signals measured with an electrode
o You can measure receptor potential of the skin by touching a micro electrode
see a rise in membrane potential
o Synaptic potential can be measured by putting an electrode in the neuron
upon activating a single synapse
see rise in membrane potential
o Action potential when threshold potential is reached
Experiment
o Electrode to stimulate neuron
o An electrode to measure current
On injecting negative current get a hyperpolarizing potential
passive response
Injecting positive current get same response in positive direction
If you inject higher positive current and membrane potential goes
above threshold (action potential) you get a massive spike
(overshoot)
If you double the current height of action potential doesn’t
increase but you end up getting more so frequency of action
potential increases
So for neuron to fire membrane potential has to be above threshold high
stimulus causes multiple action potentials
Resting membrane potentials of neurons is always between -50 and -90 mV
negative membrane potential
Papers at journal club will be part of the exam
Textbook: Purves 5th ed
20 min presentation at journal club
5-6 MCs per lecture and 10 MCs on papers
LECTURE 1: Chapter 1
Nervous system cells can be divided into 2 categories
o Neurons
o Neuroglia supporting cells
Mitochondria concentrated at the synapses of neurons while ER is not present in
axons or dendrites
Dendrites are primary input for synaptic input from axons of other neurons
Dendrites have high ribosome content and specific cytoskeletal proteins
Neurons that lack dendrites are innervated by the axons of one or few neurons
o Their capacity to integrate information from diverse sources is limited
Neurons with elaborate and more dendritic branches are innervated by a large
number of other neurons
o For greater integration of information
Number of in puts to a neuron refer to its convergence and number of targets
innervated by a neuron refers to its divergence
Nerve cells integrate and relay information from other neurons in a neuronal circuit
Axons to dendrites make synaptic contact presynaptic neuron is adjacent to a
specialized region in the post synaptic receptors
, Neurons communicate via releasing molecules into the synapse and taking them up
neurotransmitters
Projection neurons have long axons for distant targets spinal cord to leg nerve
(1m)
Interneurons and projection neuron axons locally branch to innervate multiple post
synaptic sites on many neurons
Axons convey electric signals over distances by a self-regenerating wave of electric
activity called action potential
Chemical synapses presynaptic terminal and postsynaptic specializations
Electrical synapses mediated by gap junctions rare in normal CNS but present
in developing CNS synchronises local networks of neurons
Glial cells support nerve cells and also contribute to development of adult nervous
system repair, acting as stem cells when required
Mitochondria concentrated in synapses of neurons
The filament, tubules, motors and scaffolding proteins in glial and neuronal cells
o Migration of nerve cells
o Growth of axons and dendrites
o Trafficking and positioning of membrane components
o Exocytosis and endocytosis for synaptic transmission
Synaptic vesicles contain neurotransmitters and neuroactive molecules located
close to the presynaptic membrane
Glial cells functions
o Maintaining ionic concentrations of nerve cells
o Modulating rate of neuronal propagation
o Modulating synaptic action
o Providing scaffold for neuronal development
o Recovery from neural injury
o Interface between brain and immune system
, Glial cell types
o Astrocytes
Restricted to the CNS
Maintain appropriate chemical environment for neuronal signalling
including formation of BBB
o Oligodendrocytes
Restricted to CNS
Produce myelin for neurons
In some cases can regenerate themselves
o Schwann cells
In PNS
Produce myelin
In some cases can regenerate themselves
o Microglial cells
Derived mainly from hematopoietic but also neural precursor cells
Scavenger cells remove cellular debris
Secrete cytokines for local inflammation
Glial stem cells also in the brain (subset of astrocytes) regenerate glial cells and
sometimes even neurons also can renew themselves
o Found in subventricular zone
o And in ventricular zone
Oligodendrocyte precursors scattered through white matter give rise to
oligodendrocytes, astrocytes and sometimes neurons
Golgi method of visualisation staining with silver salts allowed for observing
neuronal cells
o Now use fluorescent dyes
, LECTURE 2: Electric signals of Nerve cells
Neurons communicate via electric signals
Neurons are poor generators and conductors of electricity because they are made of
lipids
Mechanism to overcome this
o Lipid bilayers are not permeable through the layer they are only
permeable via pores
o So neurons have pores that allow ion exchange
There is selective permeability for these ions
Electrical signals measured with an electrode
o You can measure receptor potential of the skin by touching a micro electrode
see a rise in membrane potential
o Synaptic potential can be measured by putting an electrode in the neuron
upon activating a single synapse
see rise in membrane potential
o Action potential when threshold potential is reached
Experiment
o Electrode to stimulate neuron
o An electrode to measure current
On injecting negative current get a hyperpolarizing potential
passive response
Injecting positive current get same response in positive direction
If you inject higher positive current and membrane potential goes
above threshold (action potential) you get a massive spike
(overshoot)
If you double the current height of action potential doesn’t
increase but you end up getting more so frequency of action
potential increases
So for neuron to fire membrane potential has to be above threshold high
stimulus causes multiple action potentials
Resting membrane potentials of neurons is always between -50 and -90 mV
negative membrane potential
