Neuro Flashcards
What is an action potential?
a sudden change in the voltage across a cell surface membrane due to the flow of certain ions in and out of the neuron
at the resting membrane potential, is the inside of the cell more or less negative?
more
What is the resting membrane potential?
the difference in electrical charge between the inside and the outside of the cell when it is at rest
What is the value for the RMP for neurons?
-70mV
Do all cells have the same RMP?
no
is K+ found at a higher concentration inside or outside the cell?
inside
are Na and Cl- found at higher concentrations inside or outside the cell?
outside
Which ion has the greatest impact on the RMP?
K+
How is the RMP maintained?
Na+ K+ ATPase
Actively pumps 3Na+ out, 2K+ in
Which ion is the membrane predominantly permeable to?
K+
Where does the action potential begin?
axon hillock (conical projection between the cell body and axon)
what happens during depolarisation?
voltage gated sodium ion channels open due to an electrical stimulus
fast influx of sodium ions to +30mV
their positive charge changes potential within the cell from negative to more positive
what is the threshold potential?
the value of membrane potential that must be reached by depolarisation for an action potential to be initiated
what is the value of the threshold potential?
-55mV
what does ‘all or nothing’ mean
if the threshold potential is reached, a response of the same magnitude is initiated regardless of the strength of the stimulus
what happens once the cell has been depolarised?
voltage gated sodium ion channels begin to close
why do voltage gated potassium channels open?
the potential within the cell is positive
what is repolarisation?
voltage gated potassium channels open
K+ ions leave the cell down their electrochemical gradient
the membrane potential becomes more negative and approaches the resting potential
what is hyperpolarisation?
repolarisation overshoots the resting potential
K+ channels are open slightly too long
the membrane potential becomes more negative
is Na+/ K+ ATPase involved in repolarisation?
no
what is a refractory period, and what are the two divisions?
time following an action potential
absolute refractory period
relative refractory period
when does the absolute refractory period occur
occurs when sodium channels close after an action potential
sodium channels cannot be opened regardless of the membrane potential
when does the relative refractory period occur?
sodium channels slowly come out of inactivation
action potentials can occur if the stimulus is large enough
what is saltatory conduction?
myelinated regions of the axon are not depolarised
why do action potentials only flow in one direction?
the refractory period
how are action potentials propagated along axons?
local currents flow following depolarisation and allow depolarisation of adjacent axonal membranes
what factors determine how far local currents travel?
capacitance and resistance
what is capacitance?
ability to store charge
how does capacitance affect the distance travelled by a local current?
a lower capacitance means a greater distance travelled
what is resistance?
number of ion channels open
how does myelin increase conducting speeds?
decreases capacitance and increases resistance
how does resistance affect the distance travelled by a local current?
a higher resistance means fewer ion channels open
means a greater distance travelled
what does osmium stain?
white matter/ myelin black
what stains myelin, and what colour?
osmium
black
what are the myelinating cells of the CNS?
oligodendrocytes
what are the myelinating cells of the PNS?
Schwann cells
what is MS?
immune system attacks the myelin sheath
saltatory conduction is disrupted
symptoms
- uncontrolled eye movement
- slurred speech
What is Guillain Barre Syndrome?
damage to PNS myelin
autoimmune
muscle weakness and pain
what is synaptic transmission?
process by which neurons communicate with each other
what are the types of synaptic transmission?
chemical (more common) and electrical
describe electrical synaptic transmission
gap junctions join pre and post synaptic clefts
very rapid adjacent depolarisation
give an example of where you can find an electrical synapse
brainstem e.g hypothalamic hormone secretion
describe a chemical synapse
5 stages
- manufacture
- storage in vesicles
- release
- activation at post synaptic receptors
- inactivation - breakdown or re-uptake
what is an EPSP?
a postsynaptic potential that propagates an action potential and results in depolarisation
excitatory post synaptic potential
what is an IPSP?
a postsynaptic potential that inhibits an action potential and results in hyperpolarisation
inhibitory post synaptic potential
Is the NMJ always, sometimes or never excitatory?
always
what is an excitatory neurotransmitter?
membrane potential of postsynaptic neuron depolarised
what is an inhibitory neurotransmitter
membrane potential of postsynaptic neuron hyperpolarised or stabilised at resting potential
what are the two types of summation?
spatial and temporal
why is summation required?
one EPSP is not enough to reach the action potential threshold
what is spatial summation?
integration of neurotransmitter signals from several presynaptic neurones to one post synaptic neurone
what is temporal summation?
input signals arrive from the same presynaptic cells at different times
how are neurotransmitters removed?
3 methods
actively reuptaken back to presynaptic axon terminal
diffuse away from receptor site
enzymatically transformed into inactive substances
Give examples of fast neurotransmitters
Ach
glutamate
GABA
Is Ach excitatory, inhibitory or both?
Both
Where is Ach excitatory?
Skeletal muscle
Where is Ach inhibitory
cardiac muscle
what is the main excitatory neurotransmitter
GLUT
glutamate
what is the main inhibitory neurotransmitter
GABA
Give examples of slow neuromodulators
NAd (norepinephrine/ noradrenaline)
DA (dopamine)
Serotonin
which neurotransmitter has a major function at the NMJ?
Ach
what are the main types of receptors of Ach?
nicotinic and muscarinic
what do nicotinic receptors respond to?
ACh and nicotine
which receptor is found at the NMJ?
nicotinic
where do muscarinic receptors work?
where PNS innervates peripheral organs and glands
e.g salivary glands and
are nicotinic receptors metabotrophic or ionotrophic?
ionotrophic
are muscarinic receptors metabotrophic or ionotrophic?
metabotrophic
what is the action of AchE
Acetylcholinesterase
Breaks down Ach to acetate + choline after function in the synaptic cleft
which neurotransmitter is important in the peripheral heart and CNS?
Noradrenaline
what affects noradrenaline?
antidepressant drugs
stimulants
what affects serotonin?
antidepressant SSRI drugs (e.g Prozac)
ecstasy
which neurotransmitter is vital in basal ganglia?
dopamine
where are most dopaminergic neurons?
substantia nigra
what affects dopamine?
antipsychotics
stimulants
Parkinson’s medication
what is an ascending tract?
neural pathway by which sensory information from peripheral nerves is transmitted to the cerebral cortex
how are ascending tracts divided?
conscious and unconscious
what comprises conscious tracts?
dorsal column-medial lemniscal pathway (DCML) and the spinothalamic tract (anterolateral system)
what comprises unconscious tracts?
spinocerebellar tracts
why does the DCML have that name?
information travels through dorsal columns in spinal cord then transmitted through medial lemniscus in brainstem
describe the DCML
fine sensation detected by receptors
afferent signals carried along 1st oder neurones to dorsal columns and up to medulla where they synapse
second order neurones decussate in medulla and travel up to thalamus where they synapse
3rd order neurones travel through internal capsule to somatosensory cortex
what are the names of the groups of neurones that comprise the DCML?
first, second and third order neurones
what does the DCML carry the sensory modalities of?
fine touch, vibration, proprioception
what do first order neurones of the DCML do?
carry sensory information (regarding touch, proprioception or vibration) from the peripheral nerves to the medulla oblongata
where do DCML first order neurons travel in?
2 versions
fasciculus cuneatus for upper limb - lateral part
fasciculus gracilis for lower limb - medial part of dorsal column
this is in the spinal cord
where do second order neurones of the DCML begin?
gracile OR cuneate nucleus in medulla
what do second order neurones of the DCML do?
receive information from preceding neurones and deliver it to third order neurones in the thalamus
where do second order neurons of the dcml synapse?
medulla
where do fibres of second order neurones of the DCML desuccate?
medulla oblongata
travel to contralateral thalamus
what do third order neurones of the DCML do?
transmit the sensory signals from the thalamus to the ipsilateral primary sensory cortex of the brain
where do signals from the upper limb travel?
in the fasciculus cuneatus (the lateral part of the dorsal column)
what vertebral segments count as the upper limb?
T6 and above
what vertebral segments count as the lower limb?
T6 and below
where do signals from the lower limb travel?
in the fasciculus gracilis (the medial part of the dorsal column)
where do fibres from the upper limb synapse?
nucleus cuneatus of the medulla oblongata
where do fibres from the lower limb synapse?
nucleus gracilis of the medulla oblongata
in the DCML, how does information travel in the spinal cord?
via dorsal columns
in the DCML, how does information travel in the brainstem?
via the medial lemniscus
what are the two tracts of the anterolateral system?
anterior spinothalamic tract
lateral spinothalamic tract
pathways are the same for both tracts
the tracts run alongside each other
what are the names of the groups of neurones in the anterolateral system?
first, second and third order neurones
what is the function of the anterior spinothalamic tract?
crude touch and pressure
what is the function of the lateral spinothalamic tract
pain and temperature
where do the first order neurones of the spinothalamic tracts arise from?
sensory receptors in the periphery
where do first order neurones of the spinothalamic tracts travel after they have arisen
enter spinal cord
where do first order neurones of the spinothalamic tracts synapse?
tip of the dorsal horn
what do second order neurones of the spinothalamic tracts do?
carry information from the dorsal horn to the thalamus
where do second order neurones of the spinothalamic tracts desuccate?
spinal cord
what do third order neurones of the spinothalamic tracts do?
carry information from the thalamus to the ipsilateral primary sensory cortex
describe the spinothalamic pathway
nociceptors or thermoreceptors detect pain, temperature or crude touch
1st order neurons carrying these signals enter spinal cord and ascend 2-3 levels before synapsing in dorsal horn of grey matter
2nd order neurones decussate either through anterior or lateral tracts then travel up to thalamus where they synapse
3rd order neurones travel through the internal capsule to the primary somatosensory cortex
what are spinocerebellar tracts?
groups of tracts carrying unconscious proprioceptive information from the muscles to the cerebellum
what are the 4 spinocerebellar tracts?
posterior spinocerebellar, cuneocerebellar, anterior spinocerebellar, rostral spinocerebellar
where does the posterior spinocerebellar tract carry information from?
lower limbs to ipsilateral cerebellum
where does the cuneocerebellar tract carry information from?
upper limbs to ipsilateral cerebellum
where does the anterior spinocerebellar tract carry information from?
lower limbs to ipsilateral cerebellum
how many times do fibres in the anterior spinocerebellar tract dessucate?
twice
meaning they end up where they started so the fibres go to thee ipsilateral cerebellum
spinoreticular tract
deep/ chronic pain
where does the rostral spinocerebellar tract carry information from?
upper limbs to ipsilateral cerebellum
what are descending tracts?
pathways by which motor signals are sent from the brain to the spinal cord
what are the divisions of the descending tracts?
pyramidal and extrapyramidal
where do pyramidal tracts originate?
cerebral cortex
what do pyramidal tracts do?
carry motor fibres to spinal cord and brainstem from cerebral cortex
what are pyramidal tracts responsible for?
voluntary control of musculature
makes sense as they come from cerebral cortex
where do extrapyramidal tracts originate?
brainstem
what do extrapyramidal tracts do?
carry motor fibres to the spinal cord
what are extrapyramidal tracts responsible for?
involuntary and autonomic control of musculature
e.g muscle tone, balancee, posture, locomotion
what are the two divisions of pyramidal tracts?
corticospinal and corticobulbar
inputs of corticospinal tracts
primary motor cortex, premotor cortex, supplementary cortex
describe the path of the corticospinal tracts
begins in the cerebral cortex, descends through the corona radiata to the internal capsule, crus cerebri, pons, medulla
in which part of the medulla do the corticospinal tracts divide into 2?
caudal
where do corticospinal tracts terminate
ventral horn of spinal cord
what is the path of the lateral corticospinal tract?
desuccates and then descends, terminating in the ventral horn
what is the path of the anterior corticospinal tracts?
remain ipsilateral to the spinal cord, then desuccates and terminates in the ventral horn of the upper thoracic levels
describe corticospinal tracts
originate in primary motor cortex
descend through corona radiata and internal capsule to medullary pyramids
90% decussate to bceomee the lateral corticospinal tract
remaining 10% forms the anterior corticospinal tract
anterior tract then decussates through the anterior white commisure
both tracts terminate in the ventral horn
what does the corticospinal tract control?
motor control of the body muscles
anterior - axial muscles
lateral - limb muscles
what does the corticobulbar tract control?
motor control of the face and neck muscles
what are the two types of neurones in the descending tracts?
upper and lower motor neurones
where do the corticobulbar tracts begin?
lateral aspect of the primary motor cortex
inputs of the corticobulbar tracts
primary motor cortex, premotor cortex, supplementary cortex
path of the corticobulbar tracts
primary motor cortex, descend through internal capsule, crus cerebri, brainstem, terminate on motor nuclei of cranial nerves (acting on facial and neck muscles)
synapse with LMNs which carry motor signals to the face and neck
which nerves are the only two to not innervate motor neurons bilaterally?
facial and hypoglossal nerve have contralateral innervation
do the upper motor neurones facial and hypoglossal nerves only provide contralateral innervation?
hypoglossal - yes
facial - contralateral below the eyes
how can you tell the difference between an upper and lower motor neurone lesion
see if there bottom of the face can move (means UMN lesion - stroke rather than Bell’s palsy)
what are the types of extrapyramidal tracts?
vestibulospinal, reticulospinal, rubrospinal, tectospinal
where does the vestibulospinal tract arise from?
vestibular nuclei
where does the medial reticulospinal tract originate from?
pons
where does the lateral reticulospinal tract originate from?
medulla
where does the rubrospinal tract originate from?
red nucleus
where does the tectospinal tract originate from?
superior colliculus
which extrapyramidal tracts desiccate?
rubrospinal and tectospinal
role of vestibulospinal tracts
balance and posture
role of medial reticulospinal tracts
voluntary movement and increasing muscle tone
role of lateral reticulospinal tracts
inhibits voluntary movement and reduces muscle tone
role of rubrospinal tracts
fine control of hand movements
originate from rd nucleus
do rubrospinal or tectospinal tracts enter the spinal cord after dessucating?
tectospinal
role of tectospinal tracts
coordinates movements of the head in relation to vision stimuli
are there synapses in the descending pathways?
no
all the neurons within the descending motor system are UMNs, and they synapse with a LMN
what does the ANS innervate?
smooth and cardiac muscle, glands
what does the somatic nervous system innervate?
skeletal muscle
which neurotransmitter do somatic nerves use?
ACh
do somatic efferent nerves have one or two axons between the CNS and skeletal muscle cell?
one
where are cell bodies of the somatic nervous system?
brainstem or ventral horn of spinal cord
do somatic efferent neurons synapse from the CNS to muscle?
no
what is the only neurotransmitter for somatic efferent neurones to use?
Ach - only excitatory
how many axons do autonomic efferent neurones use?
2 (pre and post ganglionic)
what neurotransmitters do preganglionic neurones use?
always Ach
what neurotransmitters do postganglionic neurones use?
Ach - excitatory
NAd - inhibitory
what segment of the spinal cord supplies sympathetic innervation?
T1-L2
thoraco-lumbar
where does a sympathetic neurone synapse
lateral horn
do sympathetic neurones have a long or short preganglionic axon?
short
do parasympathetic neurones have a long or short preganglionic axon?
long
functions of the autonomic nervous system
thermoregulation, exercise, digestion, competition, sexual function
where are the nuclei of the parasympathetic cranial nerves located?
brainstem
which cranial nerves are parasympathetic?
10,9,7,3 (remember by 1973)
what is the role of cranial nerve 10 in a parasympathetic response?
decreases heart rate, vasoconstriction, increases GI motility
which types of receptor and neurotransmitters are used in the parasympathetic nervous system?
Ach to nicotinic
then
Ach to muscarinic
which types of receptor and neurotransmitters are used in the sympathetic nervous system?
Ach to nicotinic
then
NAd to adrenergic
what are the roles of cranial nerves 7 and 9 in a parasympathetic response?
9 - swallowing
7 - salivary glands
what is the role of cranial nerve 3 in a parasympathetic response?
pupil constriction
what is the enteric nervous system?
involved with the GI tract
can operate independently (autoregulation)
what is a motor unit?
a SINGLE motor neuron and all the muscle fibres it innervates
what happens to the adjacent motor units when on his damaged?
get bigger
where does an UMN travel from?
motor cortex to spinal cord
where does a LMN travel from?
spinal cord to muscle
what are the consequences of an UMN lesion?
hypertonia
hyperreflexia
spasticity
positive Babinski sign
clonus
what is a positive Babinski sign?
touch sole of foot with object
foot’s big toe extends rather than flexes
consequences of a LMN lesion
hyporeflexia
hypotonia
fasciculations (small twitch)
muscle atrophy
can a muscle cell be innervated by more than one neurone?
no
can a neurone innervate more than one muscle cell?
yes
what is an end plate potential?
voltages which cause depolarization of skeletal muscle fibers caused by neurotransmitters binding to the postsynaptic membrane in the neuromuscular junction.
what is a muscle spindle?
proprioceptors that consist of intrafusal muscle fibers enclosed in a sheath
intrafusal + stretch receptor
where are muscle spindles found and what do they do?
deep in muscle, detect stretch
what is the efferent supply of muscles?
by gamma (Y) neurones
what is the afferent supply of muscles?
1a fibres
what are Golgi tendons?
tension receptors
what fibres do Golgi tendons associate with?
1b fast fibres
what spinal nerve segments does the patellar reflex test?
L2-L4
describe the patellar reflex
patella knocked
activates stretch receptors in all knee
1a from intrafusal fibres to CNS (spinal cord)
A) monosynaptic excitatory stimulation of quadriceps - knee jerk (extension)
B) polysynpatic - inhibition of flexors of knee, excitation of synergistic muscles at knee
1b from Golgi tendon to CNS
C) polysynaptic inhibition of knee jerk when too much stretch detected (prevents overextension and injury)
inverse myotactic reflex
what is a motor unit?
an alpha motor neuron and all the extrafusal skeletal fibres it innervates
what is the effect of having an alpha motor neurone innervating fewer skeletal fibres?
finer regulation
how are motor neurones somatotrophically organised in the spinal cord?
alpha motor neurones in the lateral portion control distal muscle
alpha motor neurones in the medial portion control proximal muscle
what is the spinothalamic tract?
sensory tract that carries nociceptive, temperature, crude touch, and pressure from our skin to the somatosensory area of the thalamus
part of the anterolateral system
function of nociceptors
sense pain
function of the anterior spinothalamic tract
crude touch, pressure, slow pain
function of the lateral spinothalamic tract
pain and temperature
are alpha fibres myelinated?
yes
are C fibres myelinated?
no
analgesia vs anaesthetic
analgesia
- selective pain suppression
- consciousness not affected
anaesthetic
- total pain suppression
- consciousness can be affected
Parkinson’s
loss of substantia nigra
cannot initiate movement
Myesthenia gravis
ACh at neuromuscular junction blocked
muscle weakness
berry aneurysms
caused by weakened blood vessel
Duchennes
X linked
muscular degradation
recessive
Brown Sequard
hemisectional spinal cord compression
e.g lesion below medulla and above spinothalamic decussation
- ipsilateral motor dysfunction
- ipsilateral touch, vibration, proprioception and two point discrimination dysfunction
- contralateral pain, temperature and crude touch dysfunction
Huntington’s
low GABA
high dopamine
opposite of Parkinson’s, too much overshooting movement
full penetrance, autosomal dominant, anticipation
multiple sclerosis
myelin scarring
embryology of the brain
after week 3, gastrulation
- formation of trilaminar disc
ectoderm differentially mitoses
neural groove formed
neural tube formed
neural crest cells lateral to neural tube - differentiate into brain and CNS
what is the prosencephalon?
forebrain
what is the mesencephalon?
midbrain
what is the rhombencephalon?
hindbrain
what is the prosencephalon divided into?
telencephalon and diencephalon
what comprises the telencephalon?
cerebral hemispheres and basal ganglia
what comprises the diencephalon?
thalamus, sub thalamus, hypothalamus, epithalamus
what comprises the rhombencephalon?
pons, cerebellum, medulla oblongata
what macromolecules form the myelin sheath?
lipid and protein
when does myelination begin?
in utero
3rd trimester
does myelination appear as white or grey matter?
white
which neurons tend to be unmyelinated
post ganglionic autonomic fibres
olfactors neurones
interneurones
Guillain-Barre Syndrone
rapid onset of muscle weakness
autoimmune damage to PNS
myelin sheath damaged
pain and weakness
space between membranes of pre and post synaptic membranes
synaptic cleft
end of axon
axon terminal
types of synapse, and which is more common
chemical and electrical
chemical is more common
supporting cells of the nervous system
glial cells
type sof glial cells
astrocytes, oligodendrocytes, and microglial cells
describe chemical synapses
plasma membranes of pre and postsynaptic cells are joined by synaptic cleft
axon ends in axon terminal
synaptic cleft prevents direct propagation of the current
signals are transmitted via chemical messenger
synpases are covered by astrocytes, essential for reuptake of neurotransmitter
describe electrical synapses
plasma membranes of pre and postsynaptic cells are joined by gap junctions
local currents flow directly across junction
depolarises membrane of 2nd neuron to threshold potential
very rapid
where do we find electrical synapses?
brainstem neurons e.g hypothalamus for hormone secretion
which ion causes neurotransmitter release?
calcium
describe neurotransmitter release
voltage gated calcium channels open when action potential reaches pre-synaptic terminal
vesicles move to release sites and fuse with pre-synaptic membrane
exocytosis of neurotransmitter
two types of post-synaptic membrane receptors
ionotrophic and metabotrophic
nature of ionotrophic and metabotrophic receptors
ionotrophic - ligand gated ion channels
metabotrophic - G protein coupled receptors
response of activation of ionotrophic and metabotrophic receptos
ionotrophic - ion flux to change cell voltage
metabotrophic - acts via second messengers, causing cellular effects
which are faster, ionotrophic or metabotrophic receptors?
ionotrophic
which are longer acting, ionotrophic or metabotrophic receptors?
metabotrophic
give examples of uses of neuromodulators
learning
development
action of local anaesthetics
block sodium channels to prevent depolarisation
name of neurotransmitters that release ACh
cholinergic
how is ACh broken down?
by acetylcholinesterase into acetate and choline
fate of choline after production
transported back into presynaptic axon to be reused
how many vertebrae in total?
33
how many spinal nerves?
31
which spinal cord segments are fused?
sacral
coccyx
how many cervical vertebra?
7
which are the two uppermost vertebrae called?
C1 - altas
C2 - axis
how many thoracic vertebrae?
12
how many lumbar vertebrae?
5
how many sacral vertebrae?
5 fused to form the sacrum
how many coccyx vertebrae
4 fused
what happens when muscle fibres are depolarised?
actin and myosin slide over each other to produce muscle contraction
structure of skeletal muscle
actin and myosin myofibrils
form muscle fibres
form muscle fasciculi
features of cervical vertebrae
small vertebral body
transverse foramen
bifid spinous process bar C7
triangula rintervertebral foramen
which vertebrae have a transverse foramen, and what is the purpose?
cervical
contain vertebral artery and sympathetic chain
which is the only cervical vertebra not to have a bifid spinous process?
C7
prominent spike on C2
dens
which vertebrae have a circular vertebral foramen?
thoracic
which vertebrae contain costal facets?
thoracic
which vertebrae have a triangular vertebral foramen?
lumbar
which vertebrae have broad and thick spinous processes?
lumbar
what does the central canal of the spinal cord contain?
CSF
enlargements of the spinal cord
cervical - C3 -T1 to upper limb
lumbar - L1 - S3 to lower limb
where does the spinal cord end?
L1/L2
name for the tapering of the spinal cord to a cone
conus medullaris
name for the spinal cord tapering to a strand of tisse
filum terminale
what do axons in the dorsal cord convey?
afferent - sensory neurons
what do axons in the ventral cord convey?
efferent - motor neurons
how do cervical spinal nerves leave the spine?
1 vertebra higher except for C8 which is below
how do thoracic, lumbar and sacral nerves leave?
below the corresponding vertebra
how many pairs of spinal nerves, and how are they divided?
31
8 c
12t
5l
5s
1 coccygeal
what surrounds several nerve fascicles?
eepineurium
what surrounds each fascicle?
perineurium
what connects axons laterally in a fascicle?
endoneurium
larger bundles of fascicles
funiculi
what does silver stain?
grey matter black
what stains grey and white matter, and what colours? what does this correspond to?
grey matter - cell bodies
stained black by silver
white matter - axoms/ myelin
stained black by osmium
how many dorsal and ventral horns?
2 of each
which nerve and spinal segments control penis erection?
S2, S3, S4 pudendal nerve
ankle, knee, wrist and biceps, triceps reflexes
ankle - S1, S2
knee - L3, L4
wrist and biceps - C5, C6
triceps - C7, C8
where is the cell body of the first ANS neuron?
in the CNS
can the ANS be both excitiatory and inhibitory?
yes
which neurotransmitters are used in the ANS and when?
ach before ganglion
ach (excitatory) or noradrenaline (inhibitory) after
effects of sympathetic nervous system
increased heart rate
vasoconstriction
reduced gastric motility
are ejactulation and erection parasympathetic or sympathetic?
ejaculation is sympathetic
erection is parasympathetic
where is parasympathetic outflow from?
brainstem and sacral vertebrae
which neurotransmitter is used at the effector for parasympathetic, somatic and sympathetic nerves?
para - ACh
sympathetic - NE
somatic - ACh
is the preganglionic or post ganglionic nerve of ANS myelinated?
pre
do parasympathetic or sympathetic neurons have a longer preganglionic axon?
parasympathetic
what is a motor unit?
alpha motor neuron and all the extrafusal skeletal muscle fibres it innervates
do medial or lateral alpha motor neurons control distal muscles?
lateral
what is muscle tone?
degree of contraction of a muscle or the proportion of motor units that are active at a time
region of muscle fibre directly under the terminal portion of the motor neuron
motor end plate
junction between the axon terminal and motor end plate
neuromuscular junction
what is an EPP
end plate potential
comparable to EPSP
describe the NMJ
action potential arrives at axon terminal
plasma membrane depolarised
voltage gated calcium channels open
calcium ions diffuse into the axon terminal
ACh vesicles ruse with the neuronal plasma membrane
ACh diffuses to the motor end plate and binds to cholinergic nicotinic receptors
ion channels in the receptor protein opens
more Na moves in than K out
EPP produced
upper motor neuron
cell body originates in the cerebral cortex or brainstem
terminates within the brainstem or spinal cord
symptoms of upper motor neuron damage
hypertonia
hyperreflexia
spasticity
positive babinski’s sign
clonus
can a lower motor neuron innervate more than one muscle fibre?
yes but not the other way round
types of lower motor neuron
alpha and gamma
function of alpha motor neurons
contraction of muscle fibres
which motor neurons are somatotrophically organised?
alpha
which motor neurons exhibit signs of LMN syndrome when damaged?
alpha
function of gamma motor neurons
regulation of muscle tone
proprioception
symptoms of LMN damage
hypotonia
hyporeflexia
flaccid muscle weakness or paralysis
fasciculation - small involuntary twitches
muscle atrophy
function of stretch receptors
monitor muscle length and rate of change of muscle length
what is a muscle spindle?
intrafusal fibres embeddd in muscle - extrafusal fibres
what are intrafusal fibres (in muscle spindles) innervated by?
gamma motor neurons
function of gamma motor neurons in the intrafusal fibres
keep the intrafusal fibres at a set length to optimise muscle stretch detection
types of stretch receptors
nucelar chain and nuclear bag
function of nuclear chain receptors
respond to how much the muscle is stretched
function of muscle bag receptors
respond to magnitude and speed of stretching
what part of the muscle spindle are contractile?
2 ends
centre is non-contractile
which part of the spindle is associated with fast type 1a afferent sensory nerves?
middle third
non contractile part
which part of the spindle is associated with type 2 afferent sensory nerves that are slower conducting?
inferior and superior parts
what are muscle spindle attached to in paralell?
extrafusal fibres
what does muscle tension depend on?
muscle load
muscle length
degree of muscle fatigue
what detects muscle tension?
golgi tendon organ
what do golgi tendon organs detect?
force developed by muscle and resultant change in length
what is the Golgi tendon organ?
endings of afferent fibres that wrap around collagen bundles in the tendons
which fibres run from the golgi tendon organ?
afferent 1b sensory nerve fibres
- inhibitory
how do golgi tendon organs work?
when the muscle is stretched, tension is exerted on the tendon
the bundles straighten and activate the GTO receptor endings
what do golgi tendon organs stimulate and inhibit?
stimulate motor neurons of the antagonistic muscle
inhibit alpha motor neurons to prevent muscle contraction
function of 1b fibres
inhibit muscle contraction via inhibiting alpha motor neurons
what is the stretch reflex called?
myotatic
patellar reflex
stretch reflex
patellar tendon is tapped
thigh muscle stretch
stretch receptors activation
burst of action potentials in the afferent nerve fibres
stimulation of motor unit
muscle contraction
extension of lower leg
is the patellar reflex monosynaptic?
yes
what is a polysynaptic reflex?
at least one interneuron between the afferent and efferent neurons
reciprocal innervation
afferent nerve fibres end on inhibitory interneurons
when activated, they inhibit the motor neurons of the antagonistic muscle
e.g with the patellar reflex, the neurons that flex the knee would be inhibited
withdrawal reflex
pain stimulation activates flexor muscles and inhibits extensor muscles
affected limb moves away from harmful stimulus
example of withdrawal reflex
touching something hot
withdrawal reflex in the leg
shift in weight
motor neurons to the contralateral extensors aree activated, and the flexors are inhibited
acute pain last how long
less than 12 weeks
how long is chronic pain?
over 12 weeks
nociceptive pain
arises from actual or threatened damage to non-neuronal tissue
neuropathic pain
caused by primary lesion/ dysfunction of the nervous system
pain pathway to brain
first order neuron remains ipsilateral? and synapses with second order neuron
second order neuron cell body is in the spinal cord/ brainstem
it decussates and ascends to the thalamus
third order neuron cell body is in the thalamus
axons project to somatosensory cortex
internal nociceptors
viscera
joints
muscles
external nociceptors
mucosa
skin
cornea
what can cause hyperalgesia?
bradykinin
prostaglandin E2
what is hyperalgesia?
reduced nociceptive action potential threshold
increased sensitivity to pain
types of nociceptors
alpha delta fibres
C fibres
smallest nerve fibres
C fibres
which nerve fibres have a high activation threshold?
alpha delta
what type of pain are alpha delta fibres responsible for?
and C fibres?
quick and localised pain
slow spread out pain
myelination of alpha delta fibres
thinly myelinated
myelination of C fibres
none
are alpha delta or C fibres fast?
alpha delta
what information do alpha delta fibres carry?
touch, pressure, temperature
what do alpha delta fibres release?
glutamate
what information do C fibres carry?
pain, temperature, touch, pressure, itch
what do C fibres release?
glutamate and substance P
what is substance P and its function?
peptide neurotransmitter and vasodilator
remains bound to receptors for a longer time, causing long lasting pain
analgesia
selective suppression of pain without effects on consciousness
anaesthesia
uniform suppression of pain
no pain is felt
can cause loss of consciousness
brain development
fertilisation
morula - 16 cells
blastocyst - over 16 cells
trilaminar disc
- ectoderm
- mesoderm
- endoderm
ectoderm thickens in the midline to form the neural plate in the 3rd week
neural groove formed
groove deepens to form neural tube by end of 4th week
where are neural crest cells?
lateral to neural plate
what do neural crest cells form?
ganglia
Schwann cells
adrenal medulla
meninges
dermis
CN 5, 7, 9, 10
when do primary and secondary brain vesicles form?
5th and 7th week
when does the blood brain barrier form?
8 weeks
cells of blood brain barrier
endothelial cells, pericytes, astrocytes
when does the neural tube close?
end of week 4
failure of neural tube to close in spinal cord
spina bifida
failure of neural tube to close in cephalic region
anencephalus
functions of frontal lobe
thought, memory, reasoning
which areas make up Broca’s area?
Brodmann’s area 44 and 45
only sensation not to relay through thalamus
olfactory
which gyrus is linked to limbic system?
cingulate
where is the degree of pain judged?
insula
grey matter in the midbrain around the cerebral acqueduct
periaqueductal grey
dorsal striatum
caudate nucleus and putamen
ventral striatum
nucelus accumbens and olfactory tubercle
parts of basal ganglia
caudate nucleus, putamen, nucleus accumbens, olfactory tubercle, globus pallidus, ventral pallidum, substantia nigra, subthalamic nucleus
basal ganglia disorders
parkinsons
huntingtons
lack of dopamine
parkinsons
excess dopamine
huntingtons
Parkinson’s
loss of dopaminergic neurons in substantia nigra
spacicity, reduced movement, bradykinesia, tremor
parkinson’s treatment
L Dopa
corrects dopamine deficiency
Huntington’s
cag repeats
too little GABA results in too much dopamine
autosomal dominant
full penetrance
dementia and personality change
destruction of the striatum - in particular the caudate nucleus
function of basal ganglia
posture, motor control, behavior
function of limbic system
interface between the internal and external environment
adaptive behavior, emotional responsiveness
parts of limbic system
cingulate gyrus, hippocampus, parahippocampal gyrus, anterior perforated substance, septal nuclei, uncus, amygdala
what connects the parts of the limbic system
papez circuit
function of amygdala
fear and reward
function of septal nuclei
reward and reinforcement
function of hippocampus
short term memory, spatial memory, navigation
function of papez circuit
emotional expression and memory
what does the papez circuit start and end with?
hippocampus
papez circuit
hippocampal formation, fornix, mamillary bodies, mammilothalamic tract, anterior thalamic nucleus, cingulum, entorhinal cortex, hippocampal formation
a disease of the papez circuit/ limbic system
Alzheimers
where is memory stored?
prefrontal cortex
function of hypothalamus
homeostasis
explicit memory
conscious
types of explicit memory
episodic and semantic
what is episodic memory?
autobiographical
hippocampus and midbrain
what is semantic memory?
knowledge
frontal temporal lobe
hat is implicit memory?
unconscious
skills and habits - cerebellum and basal ganglia
conditioned reflexes - cerebellum
emotion - amygdala
functions of cerebellum
motor control of equilibrium
maintenance of posture and balance
maintenance of muscle tone
coordination of voluntary movements
cerebellar tracts
corticopontocerebellar
vestibulocerebellar
spinocerebellar
where does the corticopontocerebellar tract receive information from and signal to?
primary motor cortex
middle cerebellar peduncle
where does the vestibulocerebellar tract receive information from and signal to?
vestibular impulses from labyrinths via the vestibule nucleus
to the inferior cerebellar peduncle
where does the spinocerebellar tract recieve information from and signal to?
sensory input for balance and position sense
superior cerebellar peduncle
layers of cerebellum out to in
molecular, purkinje, granule
symptoms of cerebellar damage
jerky and erratic movement
on which aspect of the midbrain are the colliculi and pineal?
dorsal
where do each pair of cranial nerves emerge?
The oculomotor nerve (III) and trochlear nerve (IV) emerge from the midbrain, the trigeminal (V), abducens (VI), facial (VII) and vestibulocochlear (VIII) from the pons, and the glossopharyngeal (IX), vagus (X), accessory (XI) and hypoglossal (XII) emerge from the medulla.
where is the locus coerulus?
lateral floor of 4th ventricle
function of locus coerulus
sleep-wake
attention and memory
stress
emotions
fissurres of the medulla
anterior median fissure
ventrolateral sulcus
posterolateral sulcus
what decussates at the medulla?
pyramids
DCML
where are the olives?
medulla
function of the medulla
autonomic
ventilation
which cranial nerves are parasympathetic?
1973
10th 9th 7th 3rd
innervation and function of hypoglossal
exit foramen
intrinsic and extrinsic muscles of the tongue
movement of the tongue
hypoglossal canal
how to tell which cranial nerves are sensory, motor or both
some say marry money but my brother says big brains matter more
innervation and function of accessory nerve
exit foramen
sternocleidomastioid and trapezius
movement of head and shoulders
innervation and function of vagus
exit foramen
a lot
pharynx, larynx, trachea, oesophagus
viscera
soft palate
general sensation
chemoreception
speech
swallowing
cardiac muscle innervation
and more
jugular foramen
innervation and function of glossopharyngeal
exit foramen
pharynx, posterior third of tongue, eustacian tube, middle ear, carotid body, carotid sinus, stylopharyngeus, parotid
taste, chemoreption, baroreception, swallowing, salivation
jugular foramen
function of vestibulocochlear nerve
innervates vestibular apparatus
position and movement of head
innervation of tensor tympani
mandibular division of trigeminal
function of third division of trigeminal
tension on tympanic membrane
innervation of lacrimal glands
facial
innervation of submandibular, sublingual and parotid
maxillary division of trigeminal
what passes through cavernous sinus?
O TOM CAT
oculomotor
trochlear
ophthalmic trigeminal
maxillary trigeminal
internal carotid
abducens
function of cornea
transmission of light
refraction
structure and function of sclera
white capsule around the eye except anterior surface where it is cornea
protection
continuation of dura and cornea
middle layer of eye
uvea
iris
specialised section of choroid
controls pupil size
sphincter muscles make pupil smaller
dilator muscles make pupil larger
give eye colour
ciliary body
smooth muscle control accommodation
innervated by PNS
glandular epithelium - produces aqueous humour
behind iris
where is the pars plana?
iris sclera junction
choroid
nutrition of the outer retina
heat sink
darkly pigmented to absorb stray photons
highly vascular
where is vitreous humour produced?
retina
where is light focused onto in the retina?
fovea centralis
this is in the middle of the macula lutea
what does the macula lutea have a high concentration of?
cones
where are the photoreceptors?
retinal pigment epithelium
function of rods
dim lighting, peripheral vision
function of cones
colour vision
layers of tear film, source and function
anterior - lipid from meibomiun gland - prevent evaporation
middle - aqueous from lacrimal glands - prevents infection
posterior - mucus from goblet cells - hydrophilic, even distribution of tear film
aqueous humour
produced by ciliary epithelium in ciliary body
maintains intraocular pressure
vitreous humour
collagen matrix
hyaluronic acid and water
what is intraocular prressure maintained at?
12-20mmHg
which parts of the eye refract light?
cornea and lens
photon pathway
tear film, cornea, aqueous humour, lens, vitreous humour, ganglion ceell, amacrine cell, bipolar cell, horizontal cell, cone, rods, pigmented epithelium (absorption of excess photons)
blood supply to the eye
internal carotid
- opthalamic artery, central retinal artery, ciliary arteries
external carotid
- facial artery supplies medial lid and orbit
in which bone is the optic canal?
sphenoid
extracranial visual pathway
optic nerve formed by convergence of axons from retinal ganglion cells
RGCs receive impulses from rods and cones
optic nerve leaves via optic canal
ntracranial visual pathway
optic chiasm in middle cranial fossa
nasal fibres cross
temporal fibres do not cross
optic tracts travel to lateral geniculate nucleus in the thalamus and fibres synapse
axons from LGN carry visula information via optic radiations
to visual cortex
Bauman’s loops
fibres from superior retinal quadrant
this is the inferior visual field
parietal lobe
meyers loop
fibres from inferior retinal quadrant
this is the superior visual field
temporal lobe
intortion
internal rotation towards midline
extortion
external rotation away from midline
which ocular muscles are controlled by nervees other than oculomotor?
LR6SO4
damage to left optic nerve
left eye blindness
damage to optic chiasm
bitemporal hemianopia
damage to left optic tract
loss of temporal vision of left eye and nasal vision of right eye
damage to left Meyers loop
loss of superior nasal field of left eye and superior temporal field of right eye
stuff in upper right of eye diagrams pretty much
two pathways of the auditory system
lemniscal and non-lemniscal
organ of Corti
organ of the inner ear located within the cochlea which contributes to audition. The Organ of Corti includes three rows of outer hair cells and one row of inner hair cells.
which nerve carries information from the organ of corti?
vestibulocochlear
lemniscal pathway
carries auditory information to the primary auditory cortex
non-lemniscal pathway
unconscious perception
do not lead to primary auditory cortex
spiral ganglion
cell bodies of first order neurons located here
wherre does the spiral ganglion recieve information from?
organ of corti - hair cells
where do first order auditory neurons synapse?
ipsilateral cochlear nuclei
auditory pathway
spiral ganglion receives information from organ of corti
vestibulocochlear nevre enters via internal acoustic meatus
travels to brainstem
first order neurons synapse at the ipsilateral cochlear nuclei
fibres of cochlar nerve bifurcate
all fibres arrive at the inferior colliculus
fibres project to ipsilateral medial geniculate body in the thalamus
projections process to primay auditory complex in temporal lobe
organised tonotrophically
do non-lemniscal pathways lead to primary auditory cortex?
no
label the ear
.
pathway of venous drainage starting at the great cerebral vein
great cerebral vein, straight sinus, transverse sinus, sigmoid sinus, internal jugular vein, jugular vein, brachiocephalic vein (formed by uniting with subclavian), SVC
confluence of sinuses
straight sinus and superior saggital sinus
lining of ventricles
ependyma
what are vertebral arteries a branch of?
subclavian
upper border of thyroid cartilage
C4
whee does the common carotid bifurcate?
upper border of thyroid cartilage
C4
two other extraocular muscles innervated by CN3
levator palpebrae superioris
sphincter pupillae
motor innervation of stapedius
facial
which glands does the facial nerve innervate?
sublingual, submandibular, lacrimal
innervation and function of CN8
cochlea and vestibular apparatus
hearing and proprioception of the head
balance
sensory, motor and paraympathetic innervation of glossopharyngeal
sensory
- posterior third of tonguee
- middle ear
- pharynx
- carotid bodies
motor
- stylopharyngeus
parasympathetic
- parotid
what innervates carotid body?
glossopharyngeal
what innervates aortic body?
vagus
what nnervates external ear?
vagus
which nerve is responsible for swallowing and speech?
vagus
functions of glossopharyngeal
general sensation, tase, chemo/ baro reception, swallowing (motor), salivation
which region of the vertebrae rotates the most?
thoracic
which region has the least capacity for flexion?
thoracic
due to ribcage
components of intervertebral discs
inner nucleus pulposus
outer annulus fibrosus - collagen
what does the ligamentum flavum connect?
laminae of adjacent vertebrae
where does the spinal cord end in
an adult
birth
an embryo
L2
L3
runs entire length of vertebral column
where would you insert a lumbar puncture?
L3/L4 n subarachnoid space
where do the internal carotid arteries enter the skull?
carotid foramina
cauda equina
spinal nerves from lower spnal cord that hang obliquely downwards
dermatome
area of skin with a sensory nerve supply from a single root of the spinal cord
thumb dermatome
C6
knee dermatome
L3
biig toe dermatome
L5
4 ascending tracts
DCML
spinothalamic
spinocerebellar
spinoreticular
where is the 3rd ventricle formed in the embryo?
diencephalon
pluripotent stem cells within nural folds
neural crest cells
which vitamins ensure the neural tube fuses?
B9 - folic acid
B12
substances within CSF
protein
urea
glucose
salts
endorphins
peptides with opiate like effects
inhibit substance p release
how long does the refractory period last?
5-10ms
which meningeal layers are vascularised?
dura and pia
not arachnoid
does the function of a muscle affect how namy muscle fibres there are?
yes
fingertips have fewer fibres for greater resolution of movement
where are UMN cell bodies?
primary motor cortex
where are LMN cell bodies?
brain stem or spinal cord
where do the optic tracts terminate?
lateral geniculate body in the thalamus
which bones make up the ossicular chain?
malleus, incus and stapes
MIS
stapes is attached to oval window
smallest bone in the body
stapes
function of ossicles
transmit vibrations from tympanic membrane to oval window
which muscles change the stiffness of the ossicular chain?
stapedius and tensor tympani
innervation of stapedius
facial
innervation of tensor tympani
trigeminal
function of stapedius and tensor tympani
control the mobility of malleus and stapes
protect the inner ear from loud noises
two ear windows
oval and round
function of the round window
vibrates with opposite phase to vibrations entering the inner ear through the oval window
moves fluid in the cochlea which means that hair cells of the basilar membrane will be stimulated and audition occurs
function of the vestibular system
balance and spatial orientation
what are the vestibular apparatus?
otolithic organs - utricle and saccule
semicircular canals
what do semicircular canals detect?
angular acceleration
what do otolithic organs detct?
linear acceleration
changes in head position relative to gravity
where are vestibular hair cells?
utricle, saccule, 3 ampulla at the base of the semicircular canals
function of vestibular hair cells
detect changes in motion and position of the head
function of cochlea
sound
what do the semicircular ducts contain?
fluid
what do the semicircular canals empty into?
sac called the utricle
where are the sense organs for balance?
semicircular ducts and utricle
where is information from the semicircular ducts sent to?
CN8 then nuclei in the medulla
vestibular nuclei
