Lec 07 Flashcards
Nervous system
1- peripheral nervous system
2- central nervous system
Central Nervous system
1- Brain
2- Spinal cord
Peripheral Nervous System
1- Efferent (outgoing)
2- Afferent (sensory/incoming)
Efferent division
Somatic (motor/voluntary) nervous system
Autonomic (visceral/involuntary) nervous system
Autonomic nervous system
Parasympathetic
Sympathetic
Enteric Nervous system (gut)
Influenced by autonomic nervous system
** But can regulate itself without ans
Cells of nervous system
1- Neurons
2- Glial cells/neuroglia
Neurons
1- excitable cells
2- carry electrical signal
3- classified based on structure/function
Glial cells
-Non-excitable cells
-Physical and biochemical support for neurons
-Classified based on location/function
Glial cells in CNS
Ependymal cells — create barriers between compartments
Astrocytes — sweepers
Microglia (immune cells— scavengers)
Oligodendrocytes form Myelin sheath
Glial cells in pns
Schwann cells — myelin sheath in pns
Satellite cells — physical support
Neuron
1- Nucleus
2- Dendrites
3- Axon hillock
4- axon
Axon can have synapses with ——
1- dendrite
2- cell body
Nerve
Bundle of axons from multiple neurons
Different neural shapes
Different functions
Pseudounipolar and bipolar
Sensory neurons
Node of Ranvier
-Where action potential regenerated
-Unmyelinated axon membrane
Schwann cell nucleus
Pushed to outside of myelin sheath
Myelin sheath
Layers of plasma membrane that form insulation
Schwann cell form insulation for
Sensory or motor neuron in PNS
Disease of dimyelination
-multiple sclerosis: degeneration of CNS myelin
-guillain-barre syndrome: degeneration of PNS myelin— usually temporary
** loss of function depends on nerve affected
Electrical signals are
Changes in membrane potential generated by movement of ions
———— channels control ion permeability of neural membrane
Voltage gated
Graded potential
Depolarization (EPSP) or hyperpolarization (IPSP)
Amplitude depend on -strength of stimulus and density of receptor channel
Signal loose strength with distance traveled
Action potential
-Only depolarization
-All-or-none response depend ob threshold
-High density voltage-gated sodium channels required
Neuronal electrical signals
1- signal in dendrite (ion permeability)
——graded potential
2- graded potential reach soma
——axon hillock high density of Na channels, if threshold reach, action potential
3- action poten along axon
4- at axon terminal, action potential triggers neurotransmitters release
5- neurotransmitters binds to receptor on postsynaptic dendrite/cell membrane
Change in potential will
Reduce by distance from cite of entry
Initial amplitude depends on
1- strength of stimulus
2- density of receptor channels
Increase strength of stimulus
Increase activation of channels
Increase channel density
Increase sensivity to stimuli
Membrane resistance R(m)
-Membrane is good insulator— high Rm
-open channel allow ion flow— low Rm
Internal resistance of cytoplasm R(i)
Depends on cytoplasm composition
Inversely related to cell diameter
