neurobiology Flashcards
what does the hippocampus do?
formation of memories
pituitary gland
production and release of hormones
hypothalamus
homeostatic regulation
wide laminar 4
sensory input
wide laminar 5
motor output
basket cells
inhibitory- innervate different layers or are confined to a single layer
functional scan
detects changes in blood flow and metabolism
lesion in parietal association cortex
lead to deficits in attention
contralateral neglect syndrome- cannot perceive objects or body parts in space
temporal association cortex
recognition of objects and memory
frontal association cortex
planning
whats in the diencephalon?
epithalamus, hypothalamus and thalamus
rubrospinal pathway
from red nucleus to spinal cord- magnocellular
from red nucleus to cerebellum- parvocellular
mesencephalic locomotor region
important in regulating speeding pattern of motion
epithalamus
circadian rhythms
reticular nucleus
GABAergic input to thalamus
sub thalamic nucleus
basal ganglia, motor control
deep brain electrode stimulation
which layer is the lateral horn in
thoracic
what does an alpha motor neurone do
innervates muscle
wallenbergs syndrome
medullary
thrombosis of vertebral artery, wide ranging of sensory and motor deficits
- Ipsilateral loss from face- trigeminal system- taste
- Contralateral loss- pain/ temperature sensitivity
Dysphagia- glossopharyngeal and cranial
brainstem glioma
account for approximately 10-20% of all childhood brain tumours.
double vision, weakness, unsteady gait, difficulty in swallowing, drowsiness, nausea, and vomiting. Rarely, behavioural changes or seizures may be seen.
functions of reticular nucleus
ascending- control arousal- sleep, attention + awareness
descending- form reticule-spinal tract- posture
contribute to HR and respiration
what does medullary nuclei of raphe nuclei do?
project to spinal cord and modulate pain transmission, movement and autonomic control
what does rostral nuclei of raphe nuclei do?
project to diverse higher brain areas- modulate pain, mood and sleep-wake cycles
axo-dendritc
excitatory- glutamate
axo-somatic
inhibitory- GABA
ago-axonic
modulatory and control transmitter release
what is presynaptic inhibition used for?
endogenous pain pathways- whether or not pain reaches CNS
1- C is inhibitory so depresses calcium current
2- reduction in transmitter released
3- synaptic potential reduced
neural integration
decision making
occurs at axon hillock
convergence and divergence
orthodromic direction
direction AP travels, from axon hillock to terminal
events at a chemical synapse
1- AP arrives at presynaptic terminal causing depolarisation
2-voltage gated calcium channels open
3-calcium rushes into the cell
4- calcium ions trigger neurotransmitter release
5-calcium influx can influence the shape of the action potential
where are neuropeptides manufactured?
in the cell body using protein manufacturing- rough ER and golgi apparatus
where are amines and amino acids manufactured?
in the synaptic terminal using synthesising enzymes that are transported from the soma
what is co-existence?
single neurone released more than one NT
3 ways to remove a NT
1- enzymatic break down- acetylcholinesterase
2-diffusion of neurotransmitter
3- reuptake of neurotransmitter
disinhibition
arrangement of inhibitory and excitatory cells in a circuit the generates excitation by transiently inhibiting a tonically active neurone
synaptotagmin
calcium sensor
synaptobrevin
binds to SNAP-25 to form a complex- moves vesicle into juxtaposed position with the membrane
3 integral membrane proteins
snaptobrevin
SNAP-25
snaptotagmin
ionotropic receptors
ion channels- action potentials
fast response
metabotropic receptors
coupled to intracellular proteins that transduce signal
slow response
how many subunits does GABA have
5
how many subunits does glutamate have
4
NMDA receptor
excitatory
needs to bind both glutamate and glycine
coincidence detector
allows sodium and calcium through- calcium acts as a secondary messenger for synaptic plasticity
noradrenaline on beta receptors
Gs- adenyl cyclase- cAMP- PKA- protein phosphorylation
metabotropic glutamate on mGLuR1
mGLuR1- Gq- phospholipase C- produces 2 secondary messengers
1- diacylglycerol- protein kinase C
2- IP3- Ca2+ release
increases protein phosphorylation and activate calcium binding proteins
dopamine
D2
Gi
decrease in adenyl cyclase- decrease in cAMP, PKA and protein phosphorylation
what happens when glutamate binds to mGLuR2
it is linked to Gi- decrease in adneyl cyclase and cAMP
hemicolinium
blocks reuptake of choline so decreases Ach signalling
vesamicol
inhibits Ach uptake- decreasing signal
botulinum
prevents release of Ach- muscle paralysis
nicotine
enhances activity of Ach
scopolamine
decreases activity of Ach
sarin
enhances activity of Ach
AchE is an unreliable thing to stain
1- it might be located postsynaptically
2- it could be serving other cellular functions
3- missing from cholinergic neurones
enzyme that catalyses glutamine to glutamate
glutaminase
enzyme that catalyses glutamate to glutamine
glutamine synthase
Nisl staining
number of neurone
stains the cell body
Golgi staining
whole neurone
stains dendrites and cell soma
layer 2 and 3 in the brain
small pyramidal cells
excitatory neurones
layer 4 in the brain
stellate cells
massive dendritic aborisations
from the thalamus
layer 5 in the brain
large pyramidal cells
output
layer 6 in the brain
pyramidal cells that project to the thalamus
what is an EEG
electrodes are placed on the head and the frequency is measured
frequency varies depending on the state of activity
superior colliculus
visual, acoustic and somatosensory info
in the tectal region
orientates the head and eyes towards a stimulus
inferior colliculus
acoustic
sends info either to superior colliculus or to the thalamus
red nucleus
high iron content
motor nucleus- output to cerebellum
rubrospinal pathway
important for fine control of movement
mesencephalic locomotor region
regulating speed of pattern of movement
mesocortical
ventral tegmental area to frontal cortex
linked to schizophrenia
mesolimbic
ventral tegmental area to ventral striatum
linked to OCD, ADHD and drug addiction
medial hypothalamus
homeostasis
lateral hypothalamus
sleep and wakefulness
voltage clamp
keep voltage the same but change the current
see what happens at different voltages
electrode in a single neurone
patch clamp
categorise ion channels
neuronal firing patterns
one in ECF and one in neurone
what is grey matter
neuronal cell bodies and dendrites
what is white matter
ascending and descending tracts
what is presynaptic facilitation
1- depresses K+ current in A terminal- depolarise for longer
2- calcium in A increases
3- increase in transmitter release in A and B
4- amplitude of synaptic potential in B increases
convergence
lots of inputs- only when all inputs come together might reach threshold and get an action potential
divergence
more than one axon- communication with more than one neurone
e.g. a basket cell acts on 10 purkinje cells
breakdown of glutamate
1- in an astrocyte- glutamine synthase
2- reversal of transamine reaction
3- glutamate dehydrogenase
what is glutamate dehydrogenase
enzyme that catalyses glutamate to GABA
mainly found in axons
Inhibited by allylglycine
GABAa binding sites
1- GABA 2- benzodiazepines 3- steroid- anaesthetics 4- barbiturate- depressants 5- picrotoxin- convulsants
what are the requirements of the visual system?
high resolution vision
sensitive to wide luminance range
ability to move the eye, stabilise the image and adjust gaze
what are the constraints of the visual system?
mechanical constraints on the optic nerve- thin and flexible
metabolic costs
what does the cornea do?
focuses the light on the retina
what does the iris do?
controls the size of the pupil in response to light intensity
what do the ciliary muscles do?
control the shape of the lens
what is accommodation?
changing the shape of the lens depending on near/far objects to focus light on the retina
what is resolution?
the ability to distinguish between 2 points
what happens in light- phototransduction
light absorbed by opsin activates transducer (G protein) alpha form binds to phosphodiesterase this breaks down cGMP into GMP ion channels close causing hyperpolarisation
receptive field
area of the retina that the ganglion cell is responsible for
receptive field centre
corresponds to the extent of the ganglion cell dendritess
what do starburst amacrine cells respond to?
motion moving away from the body
release more NT when a stimulus moves away along a dendrite
wired up to direction selective ganglion cells
what are bird detectors?
they are found in mice retina
they are strongly inhibited by motion in the large surround
sensitive to stimuli in the small receptive field
what happens if bright light on green on red off
green light on centre- excites RGC
red light on surround- excites amacrine cells- inhibits RGC
RGC compares how much green relative to red
what is the pigment melanopsin
responds best to blue light- between blue and green
iPRGCs
intrinsically photosensitive retinal ganglion cells
they encode how bright things are
contain melanopsin in the membrane so if all synaptic transmission is lost can still respond
will fire for a long and sustained time
>project to the SCN and OPN (olivary pretectal nucleus)
where does the vestibular system project to?
vestibular nucleus- oculomotor nerves
vestibule-ocular reflex?
allows you to focus on a point
accessory optic system
collection of 3 nuclei- anterior, medial and posterior- in pretectum
respond to global movements rather than local motion
only receive information from on DSCGCs
binocular field
area that overlaps between the left and right hemispheres
stereopsis
perception of depth
what is the magnocellular layer of the LGN
layers 1+2
parasol cells (M cells)
large cell bodies
what is the parvocellular layers of the LGN
layers 3-6
midget cells (P cells)
small cell bodies
where are the koniocellular layers in the LGN
between the layers
very small cell bodies
they match whatever is above them
what is retinotopic organisation?
The same all the way through
visual space to ganglion cells to LGN- will be next to each other the whole way through
what does staining with cytochrome oxidase reveal?
columns running through the layers
the columns are colour opponent- neurones in these regions are processing colour
lateral corticospinal tract
skilled limb movement
ventral corticospinal tract
axial muscle control
corticobulbar tract
controls primary facial muscles, jaw, and muscles for speaking and swallowing
red nucleus, RF.
rubrospinal tract
red nucleus
limb control
tectospinal tract
originates from superior colliculus
head-eye coordinating gaze
reticulospinal tract
diverse automatic movements and posture
vestibulospinal tract
for posture and balance
extrafusal fibres
generate muscle tension
innervated by alpha motoneurones
intrafusal fibres
gain control function
innervated by gamma motor neurones
what is proprioception?
sense of oneself
Receptors on skeletal muscles, joints, skin
Vision & Vestibular System
detected by golgi tendon organs and spindle
what is Exteroception?
sense of external world
All special senses
Somatosensory: contact, pressure, stroking, vibration, etc.
Ia afferent
spindle afferents and efferents
senses stretch and rate of change in stretch
excite alpha motoneurons
Ib afferents
tendon organ afferents
force change in muscle
inhibit alpha motoneurons
II afferent
spindle afferents and efferents
group 2 afferent
senses stretch only
reflex
a fast, predictable automatic response to a change in the environment or a stimulus
where does the corticospinal tract go?
tract to the spinal cord
it is important for skilled movement
Plantar reflex/ Barbinski reflex
sole of foot is stimulated with a blunt instrument
normally- Plantar- the toes curl downwards
Babinski- the toes curl upwards- After loss of supraspinal or descending control (CST)
Lesions to reticulospinal and vestibulospinal tracts-
impaires gross movements but not fine
what does the basal ganglia consist of
corpus striatum, substantia nigra, globus pallidus, sub-thalamic nucleus
what is the direct pathway in the basal ganglia?
putamen to internal globus pallidus
what is the indirect pathway in the basal ganglia?
Putamen -> external Globus Pallidus -> Subthalamic nucleus -> internal Globus Pallidus
ataxia
bad movement
dysmetria
innappropiate displacement
hypotonia
weakness/ lack of muscle tone
Dysdiadochokinesis
inability to make rapid repetitive movement
Decomposition of movement
lack of co-ordination of different joints
mossy fibres
Mossy fibers -> excite granule cells -> weak affect on many Purkinje cells.
Directly :
Vestibular and spinal afferents(especially muscle spindles),.
climbing fibres
Climbing fibers -> contacts a few purkinje cells (~10) strongly excites them.
tactile receptors
sensations - mediated by low threshold mechanoreceptors, Merkel, Ruffini, Meissner & Pacinian types
Proprioception
mediated by muscle (spindle) & joint (Golgi tendon) receptors, some inputs from cutaneous mechanoreceptors
Thermal sensations
mediated by thermoreceptors localised to discrete zones that exhibit hot & cold sensitivity
Nociceptive (painful) sensations
mediated by mechanical, thermal & polymodal nociceptors
Meissner’s
Low frequency vibrations
rough texture and movement
Merkel’s disks
Small forms and shapes
epidermal/dermal border
detects form, shapes, rough edges, borders, texture
Pacinian Corpuscles-
High frequency vibrations
fine texture and movement
Ruffini’s corpuscles
pressure
deep dermis
stretching, indentation or lateral movement
Free nerve endings
noxious- harmful
hair follicle receptor
light touch
nociception
sensory process that provides the signals that trigger pain.
1st pain
fast AD fibres
sharp or prickly
short duration
mechanical/ thermal nociceptors
2nd pain
slow C fibres
dull ache
slow onset but persistent
polymodal nociceptors
areas in spinal cord innervated by afferent
lamina 1+2- substantia gelatinosa
causes of hyperalgesia
A reduced threshold for pain
An increased intensity of painful stimuli
Spontaneous pain
5 categories of taste
sweet, salty, bitter, sour and savoury
Circumvallate papillae
largest, contain many thousands of taste buds, located at posterior
Foliate papillae
elongated structure, contain hundreds of taste buds, lie along posterior lateral edge
Fungiform papillae
smallest, contain one or two taste buds, widespread across anterior portion and tip of tongue
sequence of events for taste transduction
1- Dissolved molecules interact with sites OR modulate ion channels on apical microvilli
2- Triggers membrane depolarization & action potential firing
3- Accompanied by increase in intracellular calcium which initiates transmitter release
4-Transmitters excite afferent nerve fibres which combine to form cranial nerves (VII, IX & X) activated by taste stimuli
4 mechanisms in transduction cascade
Directly pass through ion channel
Bind to and block ion channels
Bind to and open ion channels
Bind to receptors that activate 2nd messenger systems that modulate ion channels
3 facts of neurodegenerative disorders
progressive
loss of neurones
irreversible
symptoms of parkinsons
rigidity slurred and monotone speech tremor akinesia- difficulty in initiating movement postural- stoop, shuffling and balance
