This summary is focused on the lectures and contains all the necesary information you need to know to successfully pass this course. It also contain the practice question of the lectures (will be updated every friday)
Lecture 1 Structure and function of nerve cells
From chemical elements to cell membrane:
• Oxygen, carbon (sugar & fats), hydrogen are the most present elements in our body
Bonding elements:
• Ionic bond (electrostatic) force: + attracts -
• Covalent bond (sharing of electrons to form molecules): e.g. H combines with O and
forms H2O (more centered around O because the proton is more positively charged
and therefore attracts more negatively charged neutron→ by sharing electrons both
atoms will be fully filled and ‘happy’
Carbon chains:
• Glucose (sugar) C6H12O6
• Amino acid (extra Nitrgogen atom)
• Protein: are coupled amino acids
- Peptides: short protein chains
• Lipids (fat) (long carbon chains)
Phospholipids: Carbon chains connected by an extra phosphate
(P) group
• Hydorphilic: has a negative charge and is consequently, and is thus attracted to water → The
head contains Phosphate
• Hydrophobic: don’t have an electrical charge and thus not attracted to water →The tails are
fatty acids (Lipids (fats))
- Double layer of phospholipids forms the cell membrane → the head are orientated towards
the water Colom and the tails are orientated towards each other
Nerve cells: global function neurons
• Dendrites (receive signals) → soma (=cell body) (integrate signals)→ axon (send signals) →
terminal buttons (passes on the signal to other neurons)
- Meylin sheath: fatty layers around the axon that speeds up the signal that is transported
through the axon
Global structure:
1: Cell nucleus with pores for mRNA → Recepy
for making proteins) transport
2: Endoplasmatic reticulum (production,
storage and transport proteins) → recepy is
read
3: Golgi apparatus: post office for packing
(neurotransmitter in vesicles) → packs up the
recepy
4: Mitochondria: power plant (ATP: Adenosine
Tri-Phosphate → the energy used to make the
recepy)
5: Lysosomes: waste processing →brakes down
molecules that are not being used
6: : Microtubuli: road system for
transportation of neurotransmitter through
axon → moves the recepy from the cell body to
the terminal buttons
,Cell nucleus and protein production:
• Nucleus contains chromosomes with genes (pieces of DNA: DeoxyriboNucleic
Acid) → provide recepy to make certain proteins
• Transcription: genes are read from the DNA and converted to mRNA
(messenger RNA)→ mRNA leaves the nucleus through the pores, and the
recepy is read out by ribosomes (complex of proteins), to form a protein
Axoplasmic transport:
• Kinesin: anterograde transport from the cell body (soma) to terminal buttons
• Dynein: retrograde transport from terminal buttons to soma (recycling
mechanism; transports it to the Lysosomes)
Glia cells (support cells):
• Microglia: immunologic defense and removal of dead cells
• Macroglia:
- Oligodendrocytes: creates myelin sheath around the axon in our CNS (multiple myelin
sheets)
- Schwann cells: creates myelin sheath around the axon in our in PNS (single sheet of myelin)
- Astrocytes:
o structure and solidity (glia = glue) (attaches neurons with each other)
o isolate synaptic clefts → keeps the terminal buttons of one neuron in contact with
the dendrites of another neurons
o Feeding neurons with glucose → because it is connected with the blood vessel it can
bypasses the Blood-brain-barrier for important substances e.g. glucose
Bioelectricity: membrane potential
• Neuron is a small battery!
• Inside of cell is negatively charged relative to the outside (-65 mV in humans)
Membrane potential origin →The membrane potential is caused by a balance between two forces:
• Diffusion: Due to random motion, particles will move from regions with high concentration
to regions with low concentration
• Electrostatics: Oppositely charged particles (+,-) attract each other
(+ repel + and – repel - )
The membrane contains io specific channels (Na+= sodium, K+=
potassium), Cl-, etc):
• Will open and close due to changes in voltages
• Outside cell: many Na+ en Cl-, want to move in (diffusion)
• Cl- remains out because of the electrostatic
force
• Na+ driven inward by both diffusion and
electrostatic forces (does leak in, but
transported to the outside by Na+-K+ pump to
keep it in balance)
• Inside cell: many K+ en A- (negatively charged
proteins made by the DNA), that want to go out
(diffusion) → A- can’t because they are to big
(cannot pass membrane channel)
, • K+ retained by electrostatic force (also some are leaked out but are pumped back at the same
rate by the Na+-K+ pump to keep it in balance)
Sodium-Potassium pump maintains membrane potential
• Higher Na+ concentration outside cell due to Na+-K+ pomp → for every 3
sodium ios pumped out, 2 potassium ions will be pumped in → therefor
higher potassium ions concentration inside
• Active 24/7 → highly energy consuming (ATP)!!
Action potential:
• Electric stimulation of the axon induces an action potential
• The axon generates an action potential only if the resting potential
crosses a threshold (e.g. from -70mV to -60mV)
• Al-or-none law: The magnitude of the action potential is always the
same!! → only the frequency can change
Action potential mechanism:
• Electrical stimulation causes the membrane potential to be less negative
• If a threshold is crossed (-70mV to -60mV) a cascade starts:
1. More Na+ channels are opened, Na+ flows into the cell, cell inside becomes
less negative (depolarisation)
2. K+ channels open, K+ flows out the cell, will counteract the electrical effect
of the Na+ inflow (potassium wants to go out due to diffusion)
3. Na+ channels close (refractory period), Na+ inflow is halted.
4. K+ keeps flowing out, cell inside returns to negative (repolarisation)
5. K+ channels close, Na+ channels return to their normal closed condition (can be opened
again)
6. Following the massive outflow of K+, the membrane temporarily has an extra negative charge
(hyperpolarisation) → relative refractory period
Action potential conduction: The first action potential triggers a domino effect in the axon → in this
way an action potential can be conducted along the axon → But this type of conduction is:
• Relatively slow - new action potentials are generated in neighboring regions
• Energy consuming – resting potential needs to be recovered across the whole axon, by
means of the Na+-K+ pumps
Myelin (passive conduction): An action potential can also be conducted passively (without new
action potentials).
• This is much faster, but the signal decays strongly with distance! → Solution: saltatory
conduction:
- Axon covered with pieces of myelin that prevent the generation of action potentials .
- Action potential is conducted passively through the myelin
- A new action potential is generated at the myelin interruptions (nodes of Ranvier)
Advantages myelin conduction:
• Saltatory conduction is faster (partly passive and fast through myelin)
• Saltatory conduction is energy efficient (no action potentials in myelin regions)
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