Human physiology
3. Neuronsystem
Nervous system
= network of cells specialized for recep on, integra on and transmission of informa on
Central nervous system = brain + spinal cord
Peripheral nervous system = sensory + motor nerve fibers that leave and enter the CNS or
wholly outside the CNS
Neuron = fundamental unit
Surrounded by myelin (sheat of lipid material)
Supported by glial cells
Cells of nervous system
Neurons
!Diverse in size and shape
Sensory neurons (afferent)
Cell body in middle part (pseudounipolar)
Bipolar, in between the two extensions
Note: soma c --> myelinated
Interneurons of CNS
Anaxonic = no axon
Mul polar
- Branched informa on flow
- A lot of dendri c spines, to ac vate one axon
Motor neurons (efferent)
Cell body on one side, on this dendrites
So there are different types of neurons, the shape determines the func on (way of transpor ng info)
Efferent/motor neuron
Dendrites = receive info from cell
- Extended from cell body
- Receive info from synap c connec on with adjacent neurons
- Dendri c spines
= extensions --> increase surface --> more contact can be made
Cell body = control centre
- Contain nucleus (DNA), RER, mitochondria
1. Protein synthesis for export to axon
2. Ca2+ release in response to electrical ac vity
3. ATP produc on
Axon = carry outgoing signal
- Varies in length + diameter
- Mitochondria, microtubules, vesicles with neurotransmi ers
- Axon hillock: junc on with cell body
- Branch to form terminals, which make contact with other cell at
synapses
1
,Straining with microtubuli-associated proteins
!!MAP2 = microtubuli-associated protein, only present in cell body and dendrites, not in axon
So if stain a neuron, fluorescence, iden fy the map to expression
So iden fy dendrites
Iden fy axons --> Tau protein (only in axons, absent in cell body and dendrites)
An body that selec vely recognises Tau
Synap c terminals
Sites of release of chemicals (NT)
Close proximity of other neuron/effector cell
Contain (pre-synap c) vesicles
Synap c cle between neurons or neurons and skeletal muscle
Exocytosis of vesicles
Note: Alzheimer pa ents, dendri c spines decline
Neurons are specialized to
All with dis nct areas
1. Receive + process info
2. Transmit signal
3. Determine or modify differen a on of target cells
Sensory receptor cells
Effector cells (trophic func ons)
Neuroglial cells
Different types (important scheme)
Important: myelina on
> Schwann in peripheral
> Oligodendrocytes in CNS
Microglia cells
Clean op debri, Cleaning up cells (infec on or injury in brain)
!neuron diseases, also about glial cells
2
,Ependymal cells
Satellite cells
From cerebrospiral fluid
Olgiodendrocytes
Fewer + thinner processes,
several axons at same me --> help with sturdiness of CNS
Myeline sheets around axons in CNS by enveloping concentric
layers of plasma membrane
Func on: insula ng layer --> saltatory conduc on
Schwann cells
Wrapping around single axon
Astrocytes
Star-like
- Structural support of neurons + processes in the brain
- From electrical and metabolic syncy um: connexions
syncy um of poly-energide = een cel met meerdere kernen of een weefsel of orgaan dat bestaat uit
meerdere celkernen waartussen de celmembranen verdwenen zijn
- Express NT receptors (similar to neurons)
Neurotrophic factor
- !Substrate for E, can release gliotransmi ers (like glutamate or ATP)
- Blood brain barrier
- !!Take up K+, water, NT
High K+ permeability
--> take up K+ via inward rec fying channels
= channel that enables inward current (posi ve ions going into the cell), does
not allow outward current
So only uptake no release of K+
--> dissipated through syncy um of the coupled astrocytes (connexons), so
distributed throughout the syncy um
--> help to remain extracellular [K+] low in areas with high neuronal ac vity
When high neuronal ac vity, a lot of AP, over me K+ could build up outside,
prevent AP
astrocytes are helping to lower extracellular K+ concentra ons by this uptake
- Assist in removal of certain neurotransmi ers via transporters like glutamate
Astrocytes exposed to NT
Ac vate gene protein coupled receptors
Ac va on of Ca signalling
Spreading through network
Coupled by connexons (enable communica on between cells)
modulate another neuron synap c region
Ca also effect of neuronal communica on (top of picture)
So impact neuronal communica on
Can influence connec on at other sides, so Ca signals that spread through network
3
, !!Providing neuronal energy
= glumate induced glycolysis during glutamatergic ac vity
Glutamate main NT
Problem:
> When cell ac ve, sustain ac vity, (to sustain excitability)
> Dependent on glucose as E source, directly uptake glucose
> Not all neurons in close proximity to capillary
> Exposure of neurons to glucose would depend on diffusion (only short distances)
Solu on:
Whenever neuron is ac ve --> also impact metabolism of astrocyte, increase E demand –> have to
take up glucose, but in more proximity to capillary (or form a network to neighbour other astrocyte)
> Glutamate taken up by EAATs
Cotransport of H+ and K+
Na levels in astrocytes raised (should be lowered) consumes ATP
!draw: not GLUT1 or 3, just GLUT
> Glu converted into Gln
Requires ATP
Bc for Gln there is an export system
Can be converted again into Glu in neuron
> Lactate towards the neuron
Pyruvate not leave, but lactate can bc of MCTs
In neuron again to pyruvate (is E source for neuron, mitochondria)
ATP --> Provide by indirect way --> energy rich intermediates
Not sufficient, to make a lot of ATP need pyruvate
Only need this sys when neurons are ac ve
Glu (=NT) is giving direct communica on to next neuron + info to astrocytes
= Glutamate induced glycolysis
Alzheimer pa ents display a decrease in astrocyte Cx43 gap junc ons (protein that make
gapjunc ons). How would this contribute to the disease (in other words impact brain func on)?
4
3. Neuronsystem
Nervous system
= network of cells specialized for recep on, integra on and transmission of informa on
Central nervous system = brain + spinal cord
Peripheral nervous system = sensory + motor nerve fibers that leave and enter the CNS or
wholly outside the CNS
Neuron = fundamental unit
Surrounded by myelin (sheat of lipid material)
Supported by glial cells
Cells of nervous system
Neurons
!Diverse in size and shape
Sensory neurons (afferent)
Cell body in middle part (pseudounipolar)
Bipolar, in between the two extensions
Note: soma c --> myelinated
Interneurons of CNS
Anaxonic = no axon
Mul polar
- Branched informa on flow
- A lot of dendri c spines, to ac vate one axon
Motor neurons (efferent)
Cell body on one side, on this dendrites
So there are different types of neurons, the shape determines the func on (way of transpor ng info)
Efferent/motor neuron
Dendrites = receive info from cell
- Extended from cell body
- Receive info from synap c connec on with adjacent neurons
- Dendri c spines
= extensions --> increase surface --> more contact can be made
Cell body = control centre
- Contain nucleus (DNA), RER, mitochondria
1. Protein synthesis for export to axon
2. Ca2+ release in response to electrical ac vity
3. ATP produc on
Axon = carry outgoing signal
- Varies in length + diameter
- Mitochondria, microtubules, vesicles with neurotransmi ers
- Axon hillock: junc on with cell body
- Branch to form terminals, which make contact with other cell at
synapses
1
,Straining with microtubuli-associated proteins
!!MAP2 = microtubuli-associated protein, only present in cell body and dendrites, not in axon
So if stain a neuron, fluorescence, iden fy the map to expression
So iden fy dendrites
Iden fy axons --> Tau protein (only in axons, absent in cell body and dendrites)
An body that selec vely recognises Tau
Synap c terminals
Sites of release of chemicals (NT)
Close proximity of other neuron/effector cell
Contain (pre-synap c) vesicles
Synap c cle between neurons or neurons and skeletal muscle
Exocytosis of vesicles
Note: Alzheimer pa ents, dendri c spines decline
Neurons are specialized to
All with dis nct areas
1. Receive + process info
2. Transmit signal
3. Determine or modify differen a on of target cells
Sensory receptor cells
Effector cells (trophic func ons)
Neuroglial cells
Different types (important scheme)
Important: myelina on
> Schwann in peripheral
> Oligodendrocytes in CNS
Microglia cells
Clean op debri, Cleaning up cells (infec on or injury in brain)
!neuron diseases, also about glial cells
2
,Ependymal cells
Satellite cells
From cerebrospiral fluid
Olgiodendrocytes
Fewer + thinner processes,
several axons at same me --> help with sturdiness of CNS
Myeline sheets around axons in CNS by enveloping concentric
layers of plasma membrane
Func on: insula ng layer --> saltatory conduc on
Schwann cells
Wrapping around single axon
Astrocytes
Star-like
- Structural support of neurons + processes in the brain
- From electrical and metabolic syncy um: connexions
syncy um of poly-energide = een cel met meerdere kernen of een weefsel of orgaan dat bestaat uit
meerdere celkernen waartussen de celmembranen verdwenen zijn
- Express NT receptors (similar to neurons)
Neurotrophic factor
- !Substrate for E, can release gliotransmi ers (like glutamate or ATP)
- Blood brain barrier
- !!Take up K+, water, NT
High K+ permeability
--> take up K+ via inward rec fying channels
= channel that enables inward current (posi ve ions going into the cell), does
not allow outward current
So only uptake no release of K+
--> dissipated through syncy um of the coupled astrocytes (connexons), so
distributed throughout the syncy um
--> help to remain extracellular [K+] low in areas with high neuronal ac vity
When high neuronal ac vity, a lot of AP, over me K+ could build up outside,
prevent AP
astrocytes are helping to lower extracellular K+ concentra ons by this uptake
- Assist in removal of certain neurotransmi ers via transporters like glutamate
Astrocytes exposed to NT
Ac vate gene protein coupled receptors
Ac va on of Ca signalling
Spreading through network
Coupled by connexons (enable communica on between cells)
modulate another neuron synap c region
Ca also effect of neuronal communica on (top of picture)
So impact neuronal communica on
Can influence connec on at other sides, so Ca signals that spread through network
3
, !!Providing neuronal energy
= glumate induced glycolysis during glutamatergic ac vity
Glutamate main NT
Problem:
> When cell ac ve, sustain ac vity, (to sustain excitability)
> Dependent on glucose as E source, directly uptake glucose
> Not all neurons in close proximity to capillary
> Exposure of neurons to glucose would depend on diffusion (only short distances)
Solu on:
Whenever neuron is ac ve --> also impact metabolism of astrocyte, increase E demand –> have to
take up glucose, but in more proximity to capillary (or form a network to neighbour other astrocyte)
> Glutamate taken up by EAATs
Cotransport of H+ and K+
Na levels in astrocytes raised (should be lowered) consumes ATP
!draw: not GLUT1 or 3, just GLUT
> Glu converted into Gln
Requires ATP
Bc for Gln there is an export system
Can be converted again into Glu in neuron
> Lactate towards the neuron
Pyruvate not leave, but lactate can bc of MCTs
In neuron again to pyruvate (is E source for neuron, mitochondria)
ATP --> Provide by indirect way --> energy rich intermediates
Not sufficient, to make a lot of ATP need pyruvate
Only need this sys when neurons are ac ve
Glu (=NT) is giving direct communica on to next neuron + info to astrocytes
= Glutamate induced glycolysis
Alzheimer pa ents display a decrease in astrocyte Cx43 gap junc ons (protein that make
gapjunc ons). How would this contribute to the disease (in other words impact brain func on)?
4
