Lecture 3 - Neuronal Structure And Function Flashcards
Whats common properties of the neurone with other cells?
- cell membrane
- nucleas
- ## organelles and machinery for translating genetic code into proteins
Whats the neuronal specialisation?
Excitability of the membrane
Dendrites - network of fine processes derived
from cell body
Synapse – connection between two neurones
Axon – elongated neural process, specialised for
rapid signal transmission over long distances
Myelination – fatty sheath round axon
Explain the membrane potential?
- neuronal cell membrane differentials permeable to intracellular and extracellur chemical constituents
As a result of this differential permeability to ions, there is an uneven distribution of
charge across the membrane
• This difference is the membrane potential:
the resting membrane potential of neurones is around –70mV
Whats the resting potential of membrane potential?
-70mV
What does the dendrites do?
Receiving incoming signals
What does the axon do?
Rapid transmissions of signals over long distance
Whats the connection between two neurons called?
The synapse
Who won the noble prize in physiology or medicine in 1963?
John Eccles
Alan Hodgkin
Andrew Huxley
What happens permeability increases?
Increasing the permeability to sodium (Na+) causes the membrane potential to
become less negative (depolarisation)
Whats hyperpolairsation in membrane potential?
Increasing the permeability to chloride (Cl-) causes the membrane potential to
become more negative (hyperpolarisation)
Describe the changes in charge in the dendrites?
Relatively slow
Decay over distance
Whats signal integration ?
At any one point the membrane potential is
determined by the sum of all the individual
depolarising and hyperpolarising events
originating nearby
What’s spatial summation?
At any one point the membrane potential is depdent on sum of all ESPs and IPSPs,
Therefore polarising events occurring within a localised area of
membrane will add together
Whats temporal summation?
After an EPSP or IPSP, it takes a short time for the membrane to return to
resting potential (around 5-10 msec).
• Another polarising event (EPSP or IPSP) occurring during this period will
cause an additional change in the membrane potential
• Therefore polarising events occurring close together in time will add
together (temporal summation)
Whats the action potential?
An electrical spike cause by reversal of membrane polarity
- mediated by rapid changes in membrane permeability to sodium and potassium
Whats the all of non phenomenon
an action potential is always the
same size
Does not decay over distance
• an action potential is the same size
when it reaches the terminal as it
was when it left the axon hillock
What’s the comparison fo diff classes of primary afferent axon?
A - alpha fibre
A - beta fibre
A- delta fibre
C fibre
Thick - thin
What does increasing the permeability to sodium cause?
Depolarisation
An EPSP
What does increasing the permeability to chloride cause?
Hyperpolarisation
An IPSP
What released through the synaptic cleft?
Neurotransmitters and receptors
Explain neurotransmitters?
• Synthesised in the neurones, close to the site of release
• Stored on the terminal until required for release
• Released into synaptic cleft in response to an action potential
• Binds to receptors in post-synaptic membrane
• Causes changes in membrane potentia
What does excitatory receptors cause?
Depolarisation
What does inhibitory receptors cause?
Hyperpolarisatio
Examples of neurotransmitters?
Amino acids
Acetylcholine
Dopamine
Whats agonist?
Binds to receptors and evokes the same rponse as the native transmitter
Whats the antagonist?
Binds to receptors and does not evokes any response and prevents the native transmitter or any agonist from binding to the receptor
Examples of drugs acting by different mechanisms?
Drugs affecting membrane potentials - Local anaesthetics
Drugs affecting synthesis - L-DOPA enhances dopamine
synthesis in the treatment of Parkinson’s disease
Drugs interacting with receptors - dopamine receptor
antagonists used in the treatment of schizophrenia (antipsychotic drugs)
Drugs affecting reuptake - Serotonin reuptake inhibitors (SSRI’s) used in the
treatment of depression (antidepressants)
Drugs affecting breakdown - Serotonin breakdown inhibitors used in the treatment
of depression (antidepressants
Examples of plant derivatives?
atropine (belladonna : from deadly nightshade) : antagonist at acetylcholine
receptors : first pharmacological treatment for Parkinson’s disease
• curare (from plants - Chondrodendron) : antagonist at acetylcholine receptors
• nicotine (from tobacco) : agonist at acetylcholine receptors
• muscarine (from fungus) : agonist at acetylcholine receptors
Examples of venom toxins
• bungarotoxin (from cobras) : antagonist at acetylcholine receptors
• batrachotoxin (from ‘poison arrow frogs’): opens sodium channels leading to neuronal over
excitement
• tetrodotoxin (puffer fish venom) : prevents action potentials
• botulinum toxin : blocks acetylcholine release at the neuromuscular junction - paralysi
