Fundamentals of Nervous System
Neuroanatomy—study of structure of nervous system considered context of disorders of nervous
system
-teach us lessons about organization of nervous system
-more often, structure dictate’s function
-understanding structure help understand function, help us target therapeutics for
disorders
Main Divisions of Nervous System
CNS-comprising of brain and spinal cord
PNS-comprising of cranial and spinal nerves leave CNS
-Somatic Nervous System- innervates structures of body wall
-Muscle, skin, membranes
-Autonomic Nervous System— Innervates smooth muscles, glands of internal organs,
vessal
-Returns sensory information to CNS
Divisions of Nervous System--CNS
-Spinal Cord
-Brain
-Cerebrum—Forebrain
-Telencephalon -Diencephalon
-Cerebellum
-Mesencephalon—Midbrain
-Brain Stem
-Pons -Medulla
-Ventricular System
Surface Area in Brain Human CNS
Human CNS:
Tel:81 DI:4 Mid: 1 Hind:2 CBM: 10 SC:2
Rat CNS: TEL:38 DI:6 MID: 4 HID: CLM: 10 SC: 35
General Ascending Organization
Receptor (communicating to cranial nerve or spinal cord)
Hindbrain (cranial nerve nuclei V-XII, reflexes, basic functions: BP, Heart rate) (Direct
projections to thalamus sometimes)
Midbrain (cranial nerve III- IV, visual and auditory information, reflexes, eye movement, body
movement)
Thalamus (relay station and filter for sensory processing, some involvement in movement)
Cortex (thought, voluntary movement, language, reasoning, perception, sensory cortex)
,Sensory input- Spinal Cord- Midbrain- Thalamus- Telencephalon
Symmetry of CNS
-general theme of neuroanatomy is CNS is largely symmetrical
-Hemispheres of cerebrum
-Tracts (fasciculi)
-largely move in symmetrical function through nervous system
-Columns (funiculi)-move vertical or ascend and descend through CNS
-Can decussate or cross from one side to CNS to other
-Crossed representation—generally right side of CNS receives information from
left and vis vera. Same for control or motor movements
-Commissures—move lateral or horizontal through CNS
Functional Units of CNS
-Glia—non neuronal, support cells
-Oligodendecytes, astrocytes, microglia
Neurons—Specialized cells receive and transmit signals to other cells
Neurites- axons, dendrites, terminal buttons
Nuclei—Collection of neurons comprising of unit of functionally related cells
-Grey matter
Tract—Collection of axons traversing the CNS
-White matter
Dendrites—Provide receptive pole of neuron
-branching and dendritic spines
Cell Body—metabolic and genetic central hub of a neuron
Axon—Special structure that propagates electrical signals from initial segment to terminals
Terminal Buttons—Area of neurotransmitter release, communicatees with other neurons
Synapses
-Two primary classes of synapse
-Electrical Synapse—characterized by gap junctions
-electrical signal moves from presynaptic to postsynaptic neuron
-relatively fast communication but less nuanced
,Chemical Synapses—majority of CNS responses
-Pre and post synaptic neuron separated by 30 nm space
-Communicate through neurotransmitters
-Directly-linked—fast communication associated with ligand gated ion channels
-Ionotropic receptors
-second messenger mediated—slower, dependent on interactions between proteins
to open channels
-Metabotropic receptors
-Channel openings produce postsynaptic potentials
Membrane potential
-Concentration gradient -Electrical gradient
Equilibrium potential
-Nernst Equation
NA+
Inside cell: 15. Outside Cells: 150 Equilibrium potential: 60+
K+
Inside cell: 150 Outside Cell: 5.5 Equilibrium potential: -90
CI-
Inside: 9 Outside: 125 Equilibrium potential: -70
Action Potential
-Na Channel opens when potential reached
Refractory Period-
-Absolute Refractory
-Relative Refractory
Cell Death: no longer have energy to do process, recorrect neurons, dies due to not being
able to have NA leave cell
Overview of Signaling—Myelination
PNS-Schwann Cells
CNS-Oligodendrocytes
-Myelin has high electical resistance and low capacitance
-acts as insulator
-unmyelinated axons result in slower propagation of action potential
-Myelinated axons result in increased conduction velocity at reduced metabolic
cost
-10-fold increase in speed
-unmyelinated axon at 100 um diameters= myelinated axon at 10 um diameters
-Myelin not continuous
, -NA+ and K + channels not evenly distributed
-saltatory conduction—to jump
-Whether a cell fires an action potential depends on balance of excitatory and inhibitory
inputs
Neurotransmitters
3 main classes:
- Exhibitory: serves to increase likelihood of postsynaptic neuron firing
-Glutamate -Norepinephrine
-Inhibitory: serves to decrease likelihood of postsynaptic neuron firing
-GABA, Endorphins
-Modulatory- has variables effects largely depend on brain area and receptor
targets
-Dopamine -Serotonin
Glutamate
-4 main classes of receptors
-3 ionotropic receptors
-NMDA (involved in associative learning) -Kainate -AMPA
Metabotropic receptors
Norepinephrine
-Catecholamine
-Functions through two main classes of receptors
-Both are meta tropic receptors
-a1 and a2
-a2 receptors have some inhibitory effects
-B1, B2, B3
-important of sympathetic tone
GABA
-Inhibitory
-Functions through two classes receptors
-GABA ionotropic receptor selectively permeable to CI-
GABA- metabotropic receptor permeable to K+
Synthesized from glutamate
Dopamine
-Modulatory catecholamine
-Relatively a few in number and produced in distinct areas
Acetylcholine
-Modulatory neurotransmitter critical for neuromuscular activation and cognitive process
Neuroanatomy—study of structure of nervous system considered context of disorders of nervous
system
-teach us lessons about organization of nervous system
-more often, structure dictate’s function
-understanding structure help understand function, help us target therapeutics for
disorders
Main Divisions of Nervous System
CNS-comprising of brain and spinal cord
PNS-comprising of cranial and spinal nerves leave CNS
-Somatic Nervous System- innervates structures of body wall
-Muscle, skin, membranes
-Autonomic Nervous System— Innervates smooth muscles, glands of internal organs,
vessal
-Returns sensory information to CNS
Divisions of Nervous System--CNS
-Spinal Cord
-Brain
-Cerebrum—Forebrain
-Telencephalon -Diencephalon
-Cerebellum
-Mesencephalon—Midbrain
-Brain Stem
-Pons -Medulla
-Ventricular System
Surface Area in Brain Human CNS
Human CNS:
Tel:81 DI:4 Mid: 1 Hind:2 CBM: 10 SC:2
Rat CNS: TEL:38 DI:6 MID: 4 HID: CLM: 10 SC: 35
General Ascending Organization
Receptor (communicating to cranial nerve or spinal cord)
Hindbrain (cranial nerve nuclei V-XII, reflexes, basic functions: BP, Heart rate) (Direct
projections to thalamus sometimes)
Midbrain (cranial nerve III- IV, visual and auditory information, reflexes, eye movement, body
movement)
Thalamus (relay station and filter for sensory processing, some involvement in movement)
Cortex (thought, voluntary movement, language, reasoning, perception, sensory cortex)
,Sensory input- Spinal Cord- Midbrain- Thalamus- Telencephalon
Symmetry of CNS
-general theme of neuroanatomy is CNS is largely symmetrical
-Hemispheres of cerebrum
-Tracts (fasciculi)
-largely move in symmetrical function through nervous system
-Columns (funiculi)-move vertical or ascend and descend through CNS
-Can decussate or cross from one side to CNS to other
-Crossed representation—generally right side of CNS receives information from
left and vis vera. Same for control or motor movements
-Commissures—move lateral or horizontal through CNS
Functional Units of CNS
-Glia—non neuronal, support cells
-Oligodendecytes, astrocytes, microglia
Neurons—Specialized cells receive and transmit signals to other cells
Neurites- axons, dendrites, terminal buttons
Nuclei—Collection of neurons comprising of unit of functionally related cells
-Grey matter
Tract—Collection of axons traversing the CNS
-White matter
Dendrites—Provide receptive pole of neuron
-branching and dendritic spines
Cell Body—metabolic and genetic central hub of a neuron
Axon—Special structure that propagates electrical signals from initial segment to terminals
Terminal Buttons—Area of neurotransmitter release, communicatees with other neurons
Synapses
-Two primary classes of synapse
-Electrical Synapse—characterized by gap junctions
-electrical signal moves from presynaptic to postsynaptic neuron
-relatively fast communication but less nuanced
,Chemical Synapses—majority of CNS responses
-Pre and post synaptic neuron separated by 30 nm space
-Communicate through neurotransmitters
-Directly-linked—fast communication associated with ligand gated ion channels
-Ionotropic receptors
-second messenger mediated—slower, dependent on interactions between proteins
to open channels
-Metabotropic receptors
-Channel openings produce postsynaptic potentials
Membrane potential
-Concentration gradient -Electrical gradient
Equilibrium potential
-Nernst Equation
NA+
Inside cell: 15. Outside Cells: 150 Equilibrium potential: 60+
K+
Inside cell: 150 Outside Cell: 5.5 Equilibrium potential: -90
CI-
Inside: 9 Outside: 125 Equilibrium potential: -70
Action Potential
-Na Channel opens when potential reached
Refractory Period-
-Absolute Refractory
-Relative Refractory
Cell Death: no longer have energy to do process, recorrect neurons, dies due to not being
able to have NA leave cell
Overview of Signaling—Myelination
PNS-Schwann Cells
CNS-Oligodendrocytes
-Myelin has high electical resistance and low capacitance
-acts as insulator
-unmyelinated axons result in slower propagation of action potential
-Myelinated axons result in increased conduction velocity at reduced metabolic
cost
-10-fold increase in speed
-unmyelinated axon at 100 um diameters= myelinated axon at 10 um diameters
-Myelin not continuous
, -NA+ and K + channels not evenly distributed
-saltatory conduction—to jump
-Whether a cell fires an action potential depends on balance of excitatory and inhibitory
inputs
Neurotransmitters
3 main classes:
- Exhibitory: serves to increase likelihood of postsynaptic neuron firing
-Glutamate -Norepinephrine
-Inhibitory: serves to decrease likelihood of postsynaptic neuron firing
-GABA, Endorphins
-Modulatory- has variables effects largely depend on brain area and receptor
targets
-Dopamine -Serotonin
Glutamate
-4 main classes of receptors
-3 ionotropic receptors
-NMDA (involved in associative learning) -Kainate -AMPA
Metabotropic receptors
Norepinephrine
-Catecholamine
-Functions through two main classes of receptors
-Both are meta tropic receptors
-a1 and a2
-a2 receptors have some inhibitory effects
-B1, B2, B3
-important of sympathetic tone
GABA
-Inhibitory
-Functions through two classes receptors
-GABA ionotropic receptor selectively permeable to CI-
GABA- metabotropic receptor permeable to K+
Synthesized from glutamate
Dopamine
-Modulatory catecholamine
-Relatively a few in number and produced in distinct areas
Acetylcholine
-Modulatory neurotransmitter critical for neuromuscular activation and cognitive process
