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129 Cards in this Set
- Front
- Back
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Describe the transmission of signals between neurones? |
Presynaptic neurone --> AP --> synapse --> post synaptic neurone --> AP |
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What is a synapse? |
Th junction at which the signal is passes from one neurone to another |
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What is the synaptic cleft? how big is it? |
The space that separates neurones, 20-30 nm wide |
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When was the Synapse discovered and who by? |
Charles Scott Sherrington (1857-1952) |
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What did Charles Scott Sherrington (1857-1952) find out about neurones? |
Reflexes are slower than the conduction along the axon supported Ramon Y Cajal's claim that there was a small gap between neurones |
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what is the speed of the impulse conduction Vs the reflex? |
12m/s compared to 40 m/s along an individual sensory or motor neuron |
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who discovered chemical transmission at the synapse? |
Otto Loewi 1921 -isolated frog hearts |
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What did Otto Loewi discover using isolated frog hearts? |
stimulating the vagus nerve of the donor heart slowed the heart rate down
He collected the fluid from the heart and transferred it to the recipient heart - this slowed it down Conclusion - each nerve released different chemicals into to fluid - one inhibited and one excited it
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What is the sequence of events of chemical transmission at the synapse? |
presynaptic neurone synthesises NTs
NTs stored in vesicles in axon terminals AP arrives and opens voltage gated Ca channels Ca moves into the neurone and depolarised is Within 1-2 ms leads to an increase in NT release across the synaptic cleft NT cross the synaptic cleft in 0.01 ms and attach to receptors on the postsynaptic neurone |
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What is a receptor? |
A protein embedded in the membrane that matches the molecular shape of a NT |
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What are ionotropic receptors? |
Open directly as a results of NT and are some kind of Ion channel Have a fast effect (few ms) Short lived (20ms) Used for visual and hearing inputs and muscle activity |
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What are metabotropic receptors? |
NT opens ion channels indirectly Produces slower effect +30ms Longer lasting (seconds, mins or longer) Useful behaviours such as hunger, thirst, fear, anger |
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What are EPSPs and IPSPs? |
excitatory/ inhibitory postsynaptic potentials Graded potentials - varying magnitude |
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What is an IPSP? |
Hyperpolarisation of the neurone
Decreases the rate of APs in the neurone relative to spontaneous firing
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What is an EPSP? |
Depolarisation of the neurone Increases the rate of APs in the neurone relative to spontaneous firing |
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What is temporal summation? |
PSPs can accumulate over a short time rapid repeated sub threshold stimulations of presynaptic neurone added together |
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What is spatial summation? |
IPSP and EPSP inputs arrive simultaneously at different locations on the dendrite and cell body and are combined to give an over all effect |
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In information processing the neurone acts as? |
1. an information integrator (summation) 2. a decision maker combining EPSP and IPSP inputs algebraically and determining whether to fire |
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How does the neurone act as a decision maker? |
task is made up of sets of instructions using simple logic operators. AND (.4 +.4) = .5 OR (.4 +.4) = .3 NOT (-.1) = 0 |
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what are the 3 ways to terminate NT action at the synapse? |
1. re- uptake 2. Enzymatic degradation 3. glial cells reabsorb NT |
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What NTs are cleared from the synapse via reuptake? |
5HT, DA, NA |
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What NTs are cleared from the synapse via Enzymatic degradation ? |
ACh - AChE --> acetate and choline |
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What NTs are cleared from the synapse via Glial cells? |
Glutamate - astrocytes enclose the synapse. absorbs Glutamate and converts it to its precursor glutamine Glutamine is the returned to the presynaptic terminal for reuse |
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ACh function |
enables muscle action regulates attention, learning, memory, sleeping and dreaming |
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Dopamine function |
influences movement, motivation, emotional pleasure and arousal |
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Glutamate function |
main excitatory NT involved in learning and memory |
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GABA function |
Main inhibitory NT |
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NA function |
helps control mood and arousal hunger and sleep |
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5HT function |
regulates hunger, sleep, arousal, and aggressive behaviour
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Endorphins function |
Act within the pain pathways and emotion centres of the brain |
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Examples of malfunctions of Ach? |
AD - Ach neurones deteriorate |
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Examples of malfunctions of DA? |
lower levels linked to PD higher levels linked to schizophrenia |
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Examples of malfunctions of glutamate? |
overstimulation - migraine and seizures |
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Examples of malfunctions of GABA? |
undersupply linked to seizures, tremors, insomnia |
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Examples of malfunctions of NA? |
Undersupply can depress mood |
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Examples of malfunctions of 5HT? |
Undersupply linked to depression |
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Examples of malfunctions of Endorphisns |
lack can lead to lower pain threshold or reduce ability to self sooth |
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What differences are there in NTs across species? |
NTs are the same but there are quantitative differences Number of synapses Amount of NT released Sensitivity of the receptors on postsynaptic cells They yield a rich variation in behaviour of species |
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What are the main agonist psychoactive drug mechanisms ? |
L- dopa - increase the production of NT Amphetamine - Increase the release of NT Clomidine - Bind to autoreceptors and block their inhibitory effects SSRIS, cocaine - Block the reuptake of NTs Nicotine - Bind to Postsynaptic receptors to increase the NT effect |
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What are the main antagonist psychoactive drug mechanisms ? |
AMPT - block the production of NTs Cause the depletion of NT in the vesicles Bo-tox - block the release of NTs Caffeine- Activate the autoreceptors so inhibit release of NTs Propranolol - Bind to postsynaptic receptors and block NT binding |
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What treatment is used in Myasthenia Gravis? |
Target the enzymatic degradation - AChE inhibitors |
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What is Myasthenia Gravis? |
autoimmune muscular disease leading to muscle weakness and fatigue |
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What causes Myasthenia Gravis? |
Circulating antibodies that block ACh receptors at the postsynaptic neuromuscular junction, inhibiting the stimulative effect os the NT Ach |
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What is the dominant action of Amphetamine and cocaine? |
Stimulants |
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What is the dominant action of Morphine? |
Narcotics |
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What is the dominant action of LSD? |
hallucinogen |
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What is the most common feature of abused drugs? |
They indirectly/ directly stimulate the release of dopamine in the nucleus accumbens reward |
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Cocaine |
Extracted from the coca plant topical eye and nasal surgery anaesthetic Blocks the Na channel and interferes with pain transmission Activates the CNS to produce arousal, increased alertness and elevated mood Blocks the reuptake of DA and 5HT at the synapses (potentiating their effects) |
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Define Nervous system? |
An interacting network of neurones that conveys electrochemical information throughout the body |
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Define Autonomic nervous system? |
A set of nerves that carries involuntary and automatic commands that control blood vessels, body organs and glands |
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Define Sympathetic Nervous System? |
A set of nerves that prepares the body for action in threatening situations. Fight or Flight |
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Define parasympathetic Nervous System? |
A set of nerves that helps the body return to normal resting state, controlling the body for normal metabolic business as usual |
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How long is the human brain? |
15 Cm |
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How heavy is the human brain? |
1400 grams |
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what does the forebrain consists of? |
Cerebral cortex subcortical structures Limbic system Basal ganglia Pituitary gland |
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What does the midbrain consist of? |
Tectum Tegmentum superior colliculi Substantia nigra |
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what does the hindbrain consist of? |
brain stem = Medulla reticular formation Cerebellum pons |
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cerebral cortex |
The outermost layer of the brain, visible to the human eye and divided into 2 hemispheres |
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How thick is the cerebral cortex? |
1.5-4mm thick |
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what makes us the cerebral cortex? |
Gray matter - cell bodies, dendrites and some glia White matter - dense collection of myelinated axons sites under top layer |
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What are the 2 hemispheres of the cerebral cortex separated by? |
the longitudinal fissure |
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What are the 2 hemispheres of the cerebral cortex connected by? |
The corpus collasum |
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what is the corpus collasum ? |
a dense band of fibres at the bottom of the longitudinal fissure that join the hemispheres and are essential for healthy brain function At the pons level the information crosses |
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At what level does information cross from one hemisphere to the other of the cerebral cortex? |
At the pons level |
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What is a corpus collastomy? |
surgical procedure that disconnects the cerebral hemispheres - spit brain |
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What have split brain patients shown? |
The left hemisphere - language
right - facial recognition and spatial organisation |
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What are the subcortical structures? |
thalamus Hypothalamus Mammillary bodies |
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Define subcortical structures? |
Areas that are housed under the cerebral cortex near the very centre of the brain |
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Thalamus |
relays and filters information from the sense organs and transmits information to the cerebral cortex
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hypothalamus |
regulates body temperature, hunger, thirst and sexual behaviour |
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mammillary bodies |
a relay for impulses coming from the amygdala and hippocampus |
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What makes up the limbic system? |
Hippocampus amygdala Cingulate cortex |
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what is the limbic system? |
a group of forebrain structures which are involved in motivation, learning and memory |
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Hippocampus |
responsible for the creation of new memories and integration of new memories into stable knowledge so they can be sorted indefintely in the cerebral cortex
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Amygdala |
located at the tip of each horn emotional behaviour and formation of emotional memories |
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Cingulate Cortex |
linking the behavioural outcomes to motivation and learning( critical in depression and schizophrenia) |
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What is the Basal ganglia? |
A set of subcortical structures that direct intentional movements Participates in planning behaviour and emotional expression Directs intentional behaviour
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What is the basal ganglia connected to |
abundant connections to with the prefrontal cortex |
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what does the basal ganglia consist of? |
Caudate nucleus Putamen Globus Pallidus |
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Pituitary gland |
releases hormones regulating many other glands in the body |
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What is the midbrain? |
located at the top of the brainstem and contains structures that have secondary roles in vision, audition and movement |
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Tectum |
a part of the midbrain that orients the organisms in the environment |
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Tegmentum |
a part of the midbrain that is involved in movement and arousal |
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Superior colluiculi |
help to guide eye movements and fixation of gaze |
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Inferior colluiculi |
helps sound localisation |
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Substantia Nigra |
Role in reward, addiction, projects to basal ganglia to integrate movements (dopamine containing pathways implicated in PD) |
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Hindbrain/ brain stem |
An area of the brain that coordinates information coming into and out of the spinal cord |
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Medulla |
An extension of the spinal cord into the skull that coordinates heart rate, circulation and respiration
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What do the cranial nerves relay? |
VI-XII control the sensations from the head, muscle movements in the head and parasympathetic output organs |
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reticular formation |
Brain structure that regulates sleep, wakefulness and levels of arousal |
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Cerebellm |
A large structure of the hind brain that controls fine motor skills
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Pons |
A brain structures that relays information from the cerebellum to the rest of the brain role in motor learning conigtive functions of attention and language |
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What are the 3 main dissecting planes? |
coronal (transverse of frontal) plane Sagittal plane Horizontal plane |
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Horizontal plane |
view from above
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Sagittal plane |
view from the side |
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coronal (transverse or frontal) plane |
View from the front |
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What are the 4 main lobes |
frontal lobe Parietal Occipital Temporal |
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Where is the Frontal lobe |
in the front (anterior to) the central sulcus and above (superior to) the lateral fissure |
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Where is the Parietal lobe? |
Behind (posterior to) the central sulcus |
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Where is the Occipital lobe? |
At the back (posterior) of the brain |
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Where is the Temporal lobe? |
Located on the side (laterally) of the brain |
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What is the cerebral cortex sectioned by? |
Gyrus - Sulcus - |
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What are gyrus |
a ridge on the cortex
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What are sulcus |
a groove in the brain surface
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What is the frontal lobe important for? |
Movement and complex human capabilities; speech,organising, planning, decision making personality, |
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What does the frontal lobe contain? |
Broca's area, Primary motor cortex, prefrontal cortex, |
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What is broca's areas responsible for? |
Speech production |
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What is the prefrontal cortex responsible for? |
Organising, planning, decision making, impulse control, adjusts to behaviour in response to rewards and punishments |
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What is prefrontal lobe dysfunction? |
impaired ability to learn from consequences and decreases the ability to control impulses found in schizophrenia and depression |
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What happened to phineus Gage? |
prefrontal corte damage left with no speech movement or intelligence or learning impairment Changed personality |
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What is a frontal lobotomy? |
surgical procedure that disconnects the prefrontal area from the rest of the brain |
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What is the biggest difference in the somatosensory and motor homunculus? |
The genital areas differ - larger in the somatosensory |
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What is the parietal lobe important for? |
body sensations and spatial localisation contains the primary somatosensory cortex |
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What lobes are the primary motor and somatosensory cortexes in ? |
motor- frontal somatosensory - parietal |
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What is the function of the somatosensory cortex? |
receives information about the skin senses, body position and movement and maps the functions as the sensory homunculus |
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The parietal association areas |
combine information from the body sense and vision identify object buy touch, determine location of the limbs and locate objects in space |
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What is the Occipital lobe important for?
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Vision contains the primary visual cortex |
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how does the visual cortex for a map of visual space? |
adjacent receptors in the eye send information to adjacent points in the visual cortex (retinotopic maps) |
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what does destruction of the striate cortex lead to? |
Cortical blindness in the related part of the visual field |
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What areas other than the visual cortex are in the occipital lobes |
areas that process individual components of a scene including colour, movement and form |
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What is the temporal lobe important for? |
Hearing - has the auditory cortex language, auditory and visual association areas |
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Where is Wernicke's area? |
in the temporal lobe |
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What is Wernicke's area responsible for? |
language comprehension and production damage results in meaningless speech and poor comprehension |
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Where is the inferior temporal cortex |
In the temporal lobe, part of the inferior temporal gyrus |
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What is the inferior temporal cortex important for? |
visual identification - difficulty recognising objects and familiar faces (prospoagnosia) |
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How many Broadmann areas are there? |
52 |
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what broadmanns areas are the primary auditory cortex? |
41 and 42 |
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anatomically where is the primary auditory cortex? |
posterior half of the superior temporal gyrus diving into the lateral sulcus as the transverse temporal gyri |
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what is the PNS divided up into? |
Sympa and parasympathetic nervous systems |
