Lecture 1 Structure and function of nerve cells
The course: learning goals
- Basics of neurophysiology and organization of the central and peripheral nervous system
(nerve conduction, neurotransmission, anatomy)
- Insight in biological mechanisms of perception, motor control, emotion and higher order
cognitive functions (memory, speech, reading, sleep-awareness etc.)
- Insight in the biological basis of behavioral disorders (sleep disorders, emotion disorders,
addiction, psychoses, but also neurological syndromes like Parkinson, Alzheimer, Broca’s
aphasia, etc).
- Insight in the techniques used in neuropsychology and neurophysiology
Overview
- From chemical elements to cell membrane
- Nerve cell structure
- Bioelectricity: made by nerve cells
From chemical elements to cell membrane
Bonding elements
- Bonding elements: to create molecules
- Ionic bond (electrostatic force)
o Plus attracts minus
o Creates salts
- Covalent bond (sharing of electrons forms molecules)
o Hydrogen spheres: can contain different levels of electrons
▪ Likes to have the spheres filled
▪ Different atoms have different number of spheres
• Number of electrons correlates with
number of neutrons
▪ Will make bonds to fully fill the spheres
o Orientation of the molecule is determined by the electrons
Carbon chains
- Glucose (sugar) C6H12O6
- Amino acid
o Extra Nitrogen atom = carboxylgroup
o Backbones will couple to each other
- Protein
o Peptides are short protein ch ains
- Lipids (fat)
o Long carbon chains
,...and phospholipids
- Carbon chains connected by an extra phosphate (P)
group
- Phosphate has a static negative charge and is
consequently hydrophilic
o Heads are hydrophilic: phosphate head loves
water
- Lipids (fats) are hydrophobic
o Fatty acids: do not have any charge:
hydrophobic
Cell membrane
- Formed by a double layer of phospholipids
- Heads are pointed towards water
- Tails are pointed away from water
- Tails will turn to each other
Nerve cell
global function neurons
- Neurons will have more than one dendrite but just one axon coming from the soma: can split
in into branches to activate other neurons
- Dendrites: receive signals
- Soma: integrate signals
- Axon: send signals (action potential)
- Terminal buttons: use neurotransmitter to
activate other cells
- Myelin sheath: used to speed up transmission
though the axon
o Multiple sclerosis: myelin sheath
problems, signal conduction problems
Axoplasmic transport
- Kinesin: anterograde transport from the cell body (soma) to terminal buttons
- Dynein: retrograde transport from terminal buttons to soma
global structure neurons
1. Cell nucleus with pores for mRNA transport
o to the cell body to create proteins
o contains DNA and chromosomes
2. Endoplasmatic reticulum (production, storage
and transport proteins):
3. Golgi apparatus: post office for packing
(neurotransmitter in vesicles)
4. Mitochondria: power plant (ATP: Adenosine
Tri-Phosphate)
5. Lysosomes: waste processing
6. Microtubuli: road system for transportation neurotransmitter through axon
,Cell nucleus and protein production
- Nucleus contains chromosomes with genes
- Transcription: genes are read from the DNA and converted
to messenger RNA (mRNA)
- mRNA leaves the nucleus through the pores to the cell
body, and is read out by ribosomes (complex of proteins), to
form a new protein
Glial cells (support cells)
- Glial cells: Used to be seen as just glue cells: nowadays considered to be more important
- Microglia:
o Little glia with housekeeping functions
o immunologic defence
o removal dead cells
- Macroglia: Larger glia cells
o Oligodendrocytes: form the myelin sheath
around axons in CNS
▪ Wraps extensions around axons to help
with conduction
▪ One oligodendrocyte can make multiple sheaths
o Schwann cells: myelin sheath in PNS
▪ Wraps itself around an axon
▪ Creates one layer of myelin
▪ So single Schwann cell forms a
single layer of myelin
o Astrocytes
▪ structure and solidity (glia = glue)
▪ isolate synaptic clefts: opening where
neurons contact each other
• wrap around the contact sites to
improve contact efficiency
▪ Star shaped cells
▪ Feeding neurons with glucose
• Takes out and stores important
blood components to give the brain cells
▪ Helps with keeping toxic blood components from entering the brain
▪ Neurons working very hard: can be fed by astrocytes
• Will also give adenosine: tells the cells to stop firing
• Limited energy source limits brain capacity and firing rate limits
Bioelectricity: membrane potential
- Giant axon of a squid: can be used to determine voltage difference
o Negative charge relative to outside
o the cell is like a small battery: charged cell
- Inside of cell is negatively charged relative to the outside (-65 mV): resting membrane
potential
o Varies is organisms and in different neurons within organisms
, Membrane potential origin
- The membrane potential is caused by a balance between two forces
- Diffusion:
o Due to random motion, particles will move from regions with high concentration to
regions with low concentration
- Electrostatics:
o Positively charged particles repel each other
o Negatively charged particles repel each other repulsion attraction
o Oppositely charged particles (+,-) attract each other
The membrane
- contains ion specific channels (Na+, K+, Cl-, etc)
- Channel contains: different protein subunits which creates a pore
Passing the membrane
- Outside cell:
o many Na+ en Cl-, want to move in (diffusion)
▪ sea water: salty water
o Cl- is retained by the electrostatic force
o Na+ driven inward by both diffusion and electrostatic forces
▪ (does leak in, but transported to the outside by Na+-K+ pump): if the
negative charge
inside the cell is
balanced: battery
power would be
gone
- Inside cell: many K+ en A- (negatively charged proteins), that want to go out (diffusion)
o A-: large negatively charged proteins that stay inside the cell: cannot get through: so
cell is permanently negatively charged
o K+ retained by electrostatic force
▪ lot of K+ in the cells: diffusion: should go to lower concentration outside the
cell, however negative in the cell so K will stay inside the cell
▪ too negative inside the cell: K+ will not leave: creates standard negative
potential of the cell -65mv
Sodium-Potassium pump
- maintains membrane potential
- Higher Na+ concentration outside cell due to Na+-K+ pomp
- (3 Na+ ions outward for 2 K+ ions inward): net effect: more positive taken out so negative
potential of the cell can be restored
- Active 24/7: always active for taking out sodium out of the neurons
- Highly energy consuming (ATP)!!
The course: learning goals
- Basics of neurophysiology and organization of the central and peripheral nervous system
(nerve conduction, neurotransmission, anatomy)
- Insight in biological mechanisms of perception, motor control, emotion and higher order
cognitive functions (memory, speech, reading, sleep-awareness etc.)
- Insight in the biological basis of behavioral disorders (sleep disorders, emotion disorders,
addiction, psychoses, but also neurological syndromes like Parkinson, Alzheimer, Broca’s
aphasia, etc).
- Insight in the techniques used in neuropsychology and neurophysiology
Overview
- From chemical elements to cell membrane
- Nerve cell structure
- Bioelectricity: made by nerve cells
From chemical elements to cell membrane
Bonding elements
- Bonding elements: to create molecules
- Ionic bond (electrostatic force)
o Plus attracts minus
o Creates salts
- Covalent bond (sharing of electrons forms molecules)
o Hydrogen spheres: can contain different levels of electrons
▪ Likes to have the spheres filled
▪ Different atoms have different number of spheres
• Number of electrons correlates with
number of neutrons
▪ Will make bonds to fully fill the spheres
o Orientation of the molecule is determined by the electrons
Carbon chains
- Glucose (sugar) C6H12O6
- Amino acid
o Extra Nitrogen atom = carboxylgroup
o Backbones will couple to each other
- Protein
o Peptides are short protein ch ains
- Lipids (fat)
o Long carbon chains
,...and phospholipids
- Carbon chains connected by an extra phosphate (P)
group
- Phosphate has a static negative charge and is
consequently hydrophilic
o Heads are hydrophilic: phosphate head loves
water
- Lipids (fats) are hydrophobic
o Fatty acids: do not have any charge:
hydrophobic
Cell membrane
- Formed by a double layer of phospholipids
- Heads are pointed towards water
- Tails are pointed away from water
- Tails will turn to each other
Nerve cell
global function neurons
- Neurons will have more than one dendrite but just one axon coming from the soma: can split
in into branches to activate other neurons
- Dendrites: receive signals
- Soma: integrate signals
- Axon: send signals (action potential)
- Terminal buttons: use neurotransmitter to
activate other cells
- Myelin sheath: used to speed up transmission
though the axon
o Multiple sclerosis: myelin sheath
problems, signal conduction problems
Axoplasmic transport
- Kinesin: anterograde transport from the cell body (soma) to terminal buttons
- Dynein: retrograde transport from terminal buttons to soma
global structure neurons
1. Cell nucleus with pores for mRNA transport
o to the cell body to create proteins
o contains DNA and chromosomes
2. Endoplasmatic reticulum (production, storage
and transport proteins):
3. Golgi apparatus: post office for packing
(neurotransmitter in vesicles)
4. Mitochondria: power plant (ATP: Adenosine
Tri-Phosphate)
5. Lysosomes: waste processing
6. Microtubuli: road system for transportation neurotransmitter through axon
,Cell nucleus and protein production
- Nucleus contains chromosomes with genes
- Transcription: genes are read from the DNA and converted
to messenger RNA (mRNA)
- mRNA leaves the nucleus through the pores to the cell
body, and is read out by ribosomes (complex of proteins), to
form a new protein
Glial cells (support cells)
- Glial cells: Used to be seen as just glue cells: nowadays considered to be more important
- Microglia:
o Little glia with housekeeping functions
o immunologic defence
o removal dead cells
- Macroglia: Larger glia cells
o Oligodendrocytes: form the myelin sheath
around axons in CNS
▪ Wraps extensions around axons to help
with conduction
▪ One oligodendrocyte can make multiple sheaths
o Schwann cells: myelin sheath in PNS
▪ Wraps itself around an axon
▪ Creates one layer of myelin
▪ So single Schwann cell forms a
single layer of myelin
o Astrocytes
▪ structure and solidity (glia = glue)
▪ isolate synaptic clefts: opening where
neurons contact each other
• wrap around the contact sites to
improve contact efficiency
▪ Star shaped cells
▪ Feeding neurons with glucose
• Takes out and stores important
blood components to give the brain cells
▪ Helps with keeping toxic blood components from entering the brain
▪ Neurons working very hard: can be fed by astrocytes
• Will also give adenosine: tells the cells to stop firing
• Limited energy source limits brain capacity and firing rate limits
Bioelectricity: membrane potential
- Giant axon of a squid: can be used to determine voltage difference
o Negative charge relative to outside
o the cell is like a small battery: charged cell
- Inside of cell is negatively charged relative to the outside (-65 mV): resting membrane
potential
o Varies is organisms and in different neurons within organisms
, Membrane potential origin
- The membrane potential is caused by a balance between two forces
- Diffusion:
o Due to random motion, particles will move from regions with high concentration to
regions with low concentration
- Electrostatics:
o Positively charged particles repel each other
o Negatively charged particles repel each other repulsion attraction
o Oppositely charged particles (+,-) attract each other
The membrane
- contains ion specific channels (Na+, K+, Cl-, etc)
- Channel contains: different protein subunits which creates a pore
Passing the membrane
- Outside cell:
o many Na+ en Cl-, want to move in (diffusion)
▪ sea water: salty water
o Cl- is retained by the electrostatic force
o Na+ driven inward by both diffusion and electrostatic forces
▪ (does leak in, but transported to the outside by Na+-K+ pump): if the
negative charge
inside the cell is
balanced: battery
power would be
gone
- Inside cell: many K+ en A- (negatively charged proteins), that want to go out (diffusion)
o A-: large negatively charged proteins that stay inside the cell: cannot get through: so
cell is permanently negatively charged
o K+ retained by electrostatic force
▪ lot of K+ in the cells: diffusion: should go to lower concentration outside the
cell, however negative in the cell so K will stay inside the cell
▪ too negative inside the cell: K+ will not leave: creates standard negative
potential of the cell -65mv
Sodium-Potassium pump
- maintains membrane potential
- Higher Na+ concentration outside cell due to Na+-K+ pomp
- (3 Na+ ions outward for 2 K+ ions inward): net effect: more positive taken out so negative
potential of the cell can be restored
- Active 24/7: always active for taking out sodium out of the neurons
- Highly energy consuming (ATP)!!
