Pharmacology and Physiology Flashcards
what is a dendrite and its function
the branch of a neurone that receives input from other neurones
they convey graded electrical signals passively to the some
is a dendrite active or passive in its actions to the soma
passive
what is a soma and its functions
synthetic and metabolic centre of the neurone
contains the nucleus, ribosomes, mitochondria and ER
integrates incoming signals that are conducted passively to the axon hillock
what is the axon hillock
site of initiation of the ‘all or none’ AP
what is the role of the axon
conducts output signals as AP to other neurones
mediates transport of materials between soma and presynaptic terminal
what is the synapse
point of chemical communication between neurones
what is the difference between anterograde and retrograde direction
anterograde - transport of info from the soma to the presynaptic terminal
retrograde - transport of info from the presynaptic terminal to the soma
what diseases exploit retrograde transport to infection neurones
viruses
- herpes, polio, rabies
what is the flow of electrical information in a neurone
dendrites»_space; soma»_space; axon hillock»_space; axon»_space; synapse
what is the soma sometimes called
perikaryon
what are the different types of neurones and what is there role in the body
unipolar - peripheral autonomic neurone
pseudounipolar - Dorsal root ganglion neurone
bipolar - retinal bipolar neurone
multipolar - LMN
what is meant by pseudo unipolar neurone
one neurite that bifurcates ‘splits’
what are the 4 functional regions of neurones
- input
- integrative
- conductile
- output
what is the resting potential of a cell
-70 mV
what is the threshold of a neurones
-60 mV
what happens due to depolarisation in a neurone
voltage activated sodium channels are opened i.e. influx of sodium
where does the upstroke end
+40 mV
what causes the downstroke
opening of voltage activated potassium channels i.e. efflux of potassium
what is passive conduction a factor in
propagation of the AP
what makes myelin
schwann cells in PNS
oligodendrocytes in the CNS
(both are types of macroglia)
in which type of axons is there faster conduction - myelinated or non-myelinated
myelinated
how does the AP travel along myelinated axons
AP jumps from one node of Ranvier to the next
what channels cluster at Nodes of Ranvier
voltage activated sodium channels
what do demyelinating disorders cause
slowing/cessation of nerve conduction
how are types of synapses classified
by location of presynaptic terminal upon the postsynaptic cell
what are the types of synapses
axodendritic (v common)
axosomatic (common)
axoaxonic (uncommon)
what is the transmitter in EXCITATORY synapses in the CNS
glutamate
what is the transmitter in INHIBITORY synapses in the CNS
GABA
what is the third major amino acid neurotransmitter in the CNS
glycine
what do glutamate and GABA cause
glutamate - excitatory postsynaptic potential (e.p.s.p.)
GABA - inhibitory postsynaptic potential (i.p.s.p.)
what holds the pre- and post- synaptic membrane together
the synaptic cleft
what channels do GABA, glutamate, glycine, acetylcholine and 5-HT activate
ionotropic ligand-gated ion channels (LGICs) - for fast neurotransmission
G protein-coupled receptors - for slow neurotransmission
(except glycine)
Overview of Chemical Neurotransmission Transmission
1 - uptake of precursor
2 - synthesis of transmitter
3 - storage of transmitter
4 - depolarisation by AP
5 - Calcium influx though voltage activated calcium channels
6 - Calcium induced release of transmitter (exocytosis)
7 - receptor activation
8 - enzyme-mediated inactivation of transmitter
OR
9 - re-uptake of transmitter
what neurotransmitter must be specifically synthesised by neurones
GABA
synthesis and storage of peptide neurotransmitter
1 - Synthesis of precursor peptide by ribosomes associated with the rough ER
2 - Cleavage of precursor peptide in Golgi apparatus yielding active neurotransmitter
3 - Secretory granules bud off from the Golgi apparatus
4 - Secretory granules are transported to the presynaptic terminal by fast axoplasmic transport via microtubules
what channels are excitatory channels
Na channels
Ca channels
what channels are inhibitory channels
Cl channels
K channels
what would a drug that is an agonist of a sodium channel cause
opens channel»_space; excitation
an antagonist would close the channel favouring inhibition
what would an agonist of a potassium channel cause
opens channel»_space; inhibitory
an antagonist would close the channel favouring excitation
what are the 2 major families of ligand-gated channels
Nicotinic receptors
Glutamate receptors
what are the 2 receptors for GABA and what do they operate
Ionotropic GABAa receptor - Cl- channel
Metabotropic GABAb receptor - potassium channel
what is the difference between an ionotropic and metabotropic receptors
ionotropic - direct
metabotropic - indirect
what is the receptor for Glycine and what does it ‘gate’
glycine ionotropic receptor
Cl- channel
what is a graded potential
change in the rmp caused by an EPSP or IPSP but is not of a magnitude large enough to cross threshold and cause an AP
what is an excitatory and inhibitory neurone
excitatory - releases a depolarising neurotransmitter
inhibitory - releases a hyperpolarising neurotransmitter
what can affect the outcome of neurotransmission
the distance the current has to travel to the neurones trigger zone
what is a ‘quanta’
the release of neurotransmitter from a single vesicle
what are the receptors in the somatosensory system that have a low threshold
mechanoreceptors - touch, vibration, pressure
thermoreceptors - cold, cool, indifferent, warm and hot
what are the high threshold units in the somatosensory system
nociceptors
thermal - extreme heat (>45) or cold ( < 10-15)
chemical - substances in tissue as found in inflammation
what is shingles due to
infection of dorsal root ganglion neurones by the virus - Varicella zoster
