Pharmacology Flashcards
describe the ion distribution and ion flow in a typical neuron
What effect would would a Na+ antagonist have?
Any drug that is an agonist of a Na channel -> opens channel, causes Na flow in cell, causes excitation
A Na channel antagonist -> closes channel, stops Na ion flow, favours inhibition…..e.g. local anaesthetics like lidocaine
Any drug that is an agonist of a K channel -> opens K channel, cause K flow out of cell, makes cell more negative and is therefore inhibitory
A K channel antagonist -> closes K channel, retains K in the cell, favours positive rmp and is therefore excitatory
describe the maujor events taking place at the synapse during neurotransmission
explain how neutransmitters are deactivated
what are the two types of receptors in neurotransmission?
ionotropic and metabtropic
ionotropic receptors have a direct mode of action (eg. acetycholine binds to nicotinic Ach receptors)
metabotropic receptors have an indirect mode of action (eg muscarinic receptors coupled to ion channes via G protein system)
what is the major exitory neurotransmitter?
but….How may it have an inhibtory effect?
Glutamate
may have inhibitory effect if it activates a metabotropic receptor
classify the ionotropic glutamate receptors
Non-NMDA receptors- bind to Kainate and AMPA
transport Na+ and K+
NMDA receptors- Allow passage of Na+ K+ and Ca2+
………… receptors mediate fast excitatory synaptic transmission in the CNS whereas ………… contributes a slow component to the excitatory synaptic potential
Non-NMDA ionotropic receptors (AMPA and kainate)
NMDA
……. is the main inhibitory neurotransmitter in the CNS. It acts on 2 types of receptors
- Ionotropic …….. receptor that operates a Cl- channel
- …….. is a metabotropic receptor, often activates a potassium channel
GABA
GABAa
GABAb
which drugs act on GABA receptors?
Benzodiazepines: positive allosteric modulator of the GABAA receptor so enhance Cl entry, decrease rmp, and enhance inhibition in presence of GABA
Barbiturates: similar to benzodiazepines and potentiates the effect of GABA at the GABAA receptor
Baclofen: agonist of the GABAB receptor so enhances the K current (and increases inhibition)
which drugs operate on NMDA channels?
Certain anaesthetic agents e.g ketamine and psychomimetric agents e.g. phencyclidine are selective blockers of NMDA-operated channels
Glycine is also an inhibitory neurotransmitter acting on a glycine ionotropic receptor that gates a…….. channel. It is released by ……. to inhibit antagonist muscles motoneurones
Cl- channel
interneurones in spinal cord
is it ionotropic or metabotropic receptros that are responsible for fast epsp?
ionotropic
give a definition for Graded Potential
a change in the rmp caused by an EPSP or IPSP, such a change is caused by (inhibitory or excitatory) neurotransmitter release and is not of a magnitude large enough to cross threshold and result in an AP
what’s a projection neuron?
a neuron responsible for conveying signals to other parts of the brain, typically releases Glutamate and so brings about an EPSP
Neurotransmitter is released in discrete packages called ……..
quanta
what is the labeled line principle?
Structually similar nerves can transmit different information depending upon where they terminate in the CNS
describe the 3 different types of sensory adaption
describe the 4 classifications of neurones regarding conduction velocity
name the different types of cutaneous receptors
how quickly do the different receptors adapt and what are their specific functions?
which has the bigger receptive field meissner’s corpuscles and merkel’s discs or pacinian corpuscles and ruffini endings?
Pacinian corpuscles and ruffini endings rf is much larger
where do pain and touch fibres and proprioceptors terminate in the spinal cord?
Provide an outline of the trigeminal system
describe the capabilities of the DCML system
stereognenesis (ability to recognise an object by feeling it)
proprioception (awareness of body position and movements)
fine touch
vibration detection
desrcibe the modalities in the spinothalamic tract
thermosensation, pain, crude touch, itch, tickle
describe the subdivisions of the primary somatosensory cortex
3A- Body position
3B- Touch (texture, shape, stimulus size)
1- Texture discrimination
2- Object perception (size, shape of object – stereognosis)
describe the cortical representation of the body surface in the homunculus
what are the 3 sources of input to an alpha motor neuron?
central terminals of dorsal root ganglion cells whose axons innervate the muscle spindles
upper motor neurones (UMNs) in the motor cortex and brain stem
spinal interneurones
describe the skeletal muscle fibre types
- Slow-oxidative (Type I) Fibres:
- ATP derived from oxidative phosphorylation. Slow contraction and relaxation. Fatigue resistant.
- Red fibres “dark meat” because of high myoglobin content.
- Fast (Type II) Fibres:- at least two further categories
- Type IIa. ATP derived from oxidative phosphorylation. Fast contraction and relaxation. Fatigue resistant. Red and reasonably well vascularised.
- Type IIx. ATP derived from glycolysis. Fast contraction but not fatigue resistant, pale in colour and poorly vascularised. “white meat”
describe the three types of motorunit and how the different muscle fibres match to different nerve thickness and thresholds
what’s the Henneman size principal?
the susceptibilty of a motorneurone to discharge an action potential is a function of it’s size.
Meaning slow motor units are recruited first and as frequency of action potentials increases ty[e IIa and IIx fibres are recruited
what does a muscle spindle consist of?
Spindles consist of:
a fibrous capsule
intrafusal muscle fibres (note extrafusal fibres generate muscle force)
sensory afferents (Ia class, myelinated and very fast conducting) that innervate the intrafusal fibres
gamma motor neurone efferents that innervate the intrafusal fibres (see later)
describe the stages of the myotatic reflex arc
which spinal level is being assessed at the:
Supinator
Biceps
Triceps
Quadriceps
Gastrocnemius
when a skeletal muscle is pulled, it pulls back.
This is caleed the ………. reflex
the myotatic reflex
describe the intrafusal fibres and the efferent/ afferent innervation of each type of fibre
intrafusal fibres consist of nuclear bag fibres and nuclear chain fibres
nuclear bag fibres can be brocken down in to bag 1 (dynamic) fibres and bag 2 (static fibres
Dynamic nuclear bag fibres are innervated by dynamic gamma motor neurons and type Ia afferents
Static nuclear bag fibres and nuclear chain fibres are innervated by static gamma motor neurons and type Ia & type II afferents
Describe the location, function and innervation of golgi tendon organs
located in between mucle fibre and tendon,
there function is to regualte muscle tension both generally and for protection
innervated by type Ib afferents
describe the polysynaptic pathway of the inverse myotatic pathway
name the four type of sensory endings that make up joint receptors and describe their functions
There are four types of sensory endings that make up joint receptors; free nerve endings, golgi type endings, ruffini endings, and paciniform endings
- free nerve endings, found in capsule and connective tissue – most numerous – HT – SA – nociceptive function
- Golgi-type endings, found only in ligaments – HT – SA – protective role?
- Paciniform endings, found in periosteum near the articular attachments and the fibrous part of the joint capsule – LT – SA – acceleration detectors
- Ruffini endings, found mainly in joint capsule – LT – SA - static position and speed of movements
describe reciprocal inhibition using the myotatic reflex as an example
describe reciprocal inhibition in the context of a movement initiated by the motor cortex
describe the flexor reflex and the crossed extensor relfex
nociceptoras are first order neurones that relay information to second order neurones. Where are the cell bodies of nociceptors located?
Cell bodies are located in the dorsal root ganglia (DRG) and trigeminal ganglia (TG)
what type of fibres comprise nociceptors? Describe the difference in morphology and how this relates to function
Primary afferents terminate in the dorsal horn of the spinal cord in various laminae
Most nociceptive C- and Aδ-fibres termination superficially in …..
……. cells synapse only with C- and Aδ-fibres
……… neurones receive input from all three types of fibre and thus respond to a wide range of stimuli
Cells that receive input from only Aβ-fibres are ……..
laminae I and II
Nociceptive specific (NS)
Wide dynamic range (WDR)
proprioceptive
explain reffered pain
Some visceral and skin afferents afferents converge upon the same spinothalamic neurones.
Second order neurones ascend the spinal cord in the ….. system comprising mainly
the……… & the ……….
anterolateral
The spinothalamic tract (STT)
The spinoreticular tract (SRT)
the srt transmits mostly ….. fibres
and is involved in …… response to pain
- Largely transmits slow C-fibre pain
- Involved in autonomic responses to pain, arousal, emotional responses, fear of pain
explain gate control theory
stimulation of non nociceptive neurones inhibits firing of projection neurones. Controls from cns and stimulation of non nociceptive neurones reduce transmission via projection neurones
