wk 3 neurology Flashcards
perception
- the way we perceive our environment
- dorsal stream - where
- ventral stream - what - sends info to temporal lobe
anterior visual pathway
- Photons come in through the pupils
- Get to back of eye to cause electrical signal
- Travel through anterior visual pathway to occipital cortex
attention
- Part of cognitive functions called EXECUTIVE functions
- Reflective of frontal lobe functioning (PFC)
- Dysfunction is key sign in delirium (acute confusional state)
types of attention
- focused attention
- sustained attention
- selective attention
- alternating attention
- divided attention
bottom up perception
stimulus quality and accuracy of perception
- “garbage in garbage out”
top down perception
influence of action
- we see what were looking for
areas in the brain linked to memory
in occipital lobe
- site of visuo-spatial sketch-pad
- looped around for further processing if necessary
- connected to prefrontal cortex
- phonological lope
- auditory stimuli
- Broca’s and wernicke’s areas connection
areas of the brain linked to working memory
- prefrontal cortex
- episodic buffer
- in parietal lobe
- spatial and 3D processing
- linked to prefrontal cortex
hippocampus
- important in converting short-term memory to long-term mems
- gates prod. of long-term mems
- damage to it results in anterograde amnesia - can’t make any more long-term mems
procedural memories
split between basal ganglia
- important for repetitive and frequent actions
cerebellum
- important for skilled movement eg playing piano
declarative memories
- facts, data, events etc
- not localised to any part of brain
- stored loosely throughout cerebral cortex
- small mems from hippocampus are transferred to neocortex in a distributive way - usually during sleep
- memory problems can be caused by sleep disorders
- in dementia memory loss graceful
reasoning
-reflect highly developed (pre)frontal lobes in humans
sequence of events in brain when planning movement
- info from parts of brain (visual perception, auditory perceptions from back of brain etc)
- shuttled forward to prefrontal cortex (interpretation/ a plan for movement)
- then to premotor cortex (how muscles are going to move/ sequencing)
- then to PMC (movement of muscles/ action)
goal setting
evolutionary goals
- self maintenance - heat, thirst, hunger
- self-propagation - affiliation and sex
where do goals come from
bottom up goals - limbic system top down goals - prefrontal cortex - gives cognitive feelings - beliefs and emotions
limbic system
collection fo structures deep in the brain - from the diencephalic and mesencephalic structures embryologically contains the... -hypothalamus -nucleus accumbent -medial forebrain bundle -ventral tegmental area -amygdala If objects are useful to goals limbic system gives pos. emotion if harmful give neg. emotion
amygdala
- negative emotions such as fear and anxiety
Salience
the limbic drive to invest perceptual resource in significant stimuli
the anterior stream
on top of ventral and dorsal streams
- so what stream
- decides if low level info is worth investing ventral stream energy to figure out what we’re looking at
If the limbic system and prefrontal lobe decide to invest in a percept…..
2 responses…
1- limbic system activates the hippocampus
- if something is useful or harmful then good to make a longterm memory for future guidance
2- pathway to frontal lobe - attentional control centre activated
- signals from ACC activate ventral stream
- tell ventral stream to figure out what input is
Next…
- integrate all the diff. info
- send to frontal lobe to figure out what to do
- sequence activity
- send sequence to PMC to instruct muscles to move
where does value lie in perception
1- we can learn from it
2- it can guide future actions
how we “make a plan”
1- a ‘best-guess’ about what reality currently is
2- a commitment to some goal (top down, bottom up motivation)
3- hypothesis generation
4- action in the world
5- dynamic monitoring of whether or not goal is getting closer or further away
what does top down and bottom up motivation mean
top down - PFC influence - higher order volitions - more philosophical and deep bottom up - limbic influence - primary volitions - insights from addiction, compulsions, personality disorders - more basic
wernicke-geschwind model for language
Broca - frontal lobe - production of language Wernicke - parietal temporal occipital junction (PTO) - comprehension AF (arcuate fasciculus) - connects B&W
what side of the brain are centres for language
- On the left for about 80%
- On the right for about 10%
- On both side for about 5%
damage to language areas
Broca - 'expressive' aphasia - inability to find word you're looking for Wernicke - 'receptive' aphasia - patients aren't able to understand - talk alot but nonsense as not self-monitoring AF - 'conductive' aphasia - relatively normal - unable to repeat something can't join up the understanding with the action
clinical aphasia (associated damage)
- Fluent – Wernicke or ‘phonological loop’
- Non-fluent – Broca’s, or output paths
cognitive assessments
MMSE - very limited, poorly responsive other than in advanced dementia Addenbrooke's Cognitive Examination III - useful takes ~20 mins - scored out of 100
what are the big 5 personality traits
oppeness conscientiousness extroversion agreeableness neuroticism
neural theories behind the big 5 personalities
Openness -Highly sensitive to DA spikes in PFC Conscientiousness -High connectivity within PFC centres Extroversion -Good face recognition (VC) and connectivity to amygdala -High serum oxytocin Agreeableness -Good recognition of facial emotion expression -Enlarged superior temporal gyrus Neuroticism -High connectivity from amygdala to PFC (fear/anxiety inc.)
clinical relevance of the big 5 personalities
Openness -Mixed reports of relationship to health Conscientiousness -Increased life success and subjective wellbeing -More likely to adhere to treatment Extroversion -Increased subjective wellbeing Agreeableness -Increased subjective wellbeing Neuroticism -Increased risk of mood disorders -Increased risk of substance misuse disorders
the autonomic nervous system
- Controls internal environment
oWorks together with the endocrine system
oControls important functions not under voluntary control
divisions of the ANS
-Sympathetic – “fight, flight, or fright”
o Activated during exercise, excitement and emergencies
-Parasympathetic – “rest and digest”
o Concerned with conserving energy
- Innervate mostly the same structures
- Cause opposite effect
- Maintain homeostasis
spinal outflows of ANS
-Parasympathetic c
o Cranial-sacro outflow
-Sympathetic
o Thoraco-lumbar outflow
enteric NS
Intrinsic collections of neurones within the wall of the digestive tract, and can function independently of the CNS or PNS.
- run from mouth to anus through alimentary tract
SNS - basic organisation
oIssues from T1-L2
oPreganglionic fibres from the lateral grey horn of spinal cord
oSupplies visceral organs and structures of superficial; body regions
oContain more ganglia than the parasympathetic divisions
sympathetic trunk ganglia
oLocated on both sides of the vertebral column
oLinked by short nerves into sympathetic trunks
oJoined to ventral rami by white and gray rami communicans
oFusion of ganglia -> fewer ganglia than spinal nerves
pre-vertebral ganglia of the SNS
the second neurone in sympathetic chain
oSome will run through sympathetic chain without synapsing to prevertebral ganglia
Prevertebral ganglia occur only in abdomen and pelvis
Lie anterior to the vertebral columns
Main ganglia include – coeliac, superior mesenteric, inferior mesenteric, inferior hypogastric ganglia
pharmacology of SNS
-Vast majority of neurotransmitter used in the symp. System is nor-adrenaline
-Recepotors….
oAlpha 1 located most smooth muscle in arterioles causing vasoconstriction
oAlpha 2 located on coronary arteries causing vasodilatation
oBeta 1 located on cardiac muscle causing increased contractility
oBeta 2 found in sino-atrial node to increase heart rate, in some smooth muscle in arterioles (esp. skeletal muscle ) causing vasodilation and in smooth muscle of bronchi causing bronchodilation
parasympathetic NS outflow - cranial outflow
oComes from nerves in brainstem oInnervates organs of the head, neck, thorax, and abdomen oPreganglionic fibres run via Oculomotor nerve (III) Facial nerve (VII) Glossopharyngeal nerve (IX) Vagus nerve (X)
parasympathetic NS outflow - cranial outflow - outflow via the vagus nerve
Fibres innervate the visceral organs of the thorax and abdomen
Stimulates – digestion, red. In HR and BP
Preganglionic cell bodies
•Located in dorsal motor nucleus
Ganglionic neurons
•Confined within the walls of organs being innervated
oCell bodies located in cranial nerve nuclei in the brain stem
parasympathetic NS outflow - sacral outflow
oSupplies remaining abdominal and pelvic organs
oEmerges from S2-S4
oInnervates organs of pelvis and lower abdomen
oPreganglionic cell bodies
Located in visceral motor region of spinal gray matter
oFrom sphlanchnic nerves
pharmacology of the Parasympathetic System
Acetylcholine (Ach) binds to nicotinic and muscarinic receptors
comparison of Autonomic and somatic motor system
Somatic
- One motor neuron extends from the CNS to skeletal muscle
- Axons are well myelinated, conduct rapidly
Autonomic
-Chain of 2 motor neurons
oPreganglionic neuron
oPostganglionic neuron
-Conduction is slower due to thinly or unmyelinated axons
-Autonomic ganglia close to the viscera being innervated
anatomical differences of the sympathetic and parasympathetic divisions
Arise from different regions of the CNS
- Sympathetic – also called the thoracolumbar division
- Parasympathetic – also called the cranio-sacral division
Length of postganglionic fibres
- Sympathetic – long postganglionic fibers
- Parasympathetic – short postganglionic fibers
Branching of axons -Sympathetic axons – highly branched o Influences many organs -Parasympathetic axons – few branches o Localised effect
differences in the neurotransmitters in the ANS
Neurotransmitters of Autonomic Nervous System
-Neurotransmitter released by preganglionic axons
oAcetylcholine for both branches (cholinergic – nicotinic receptors)
-Neurotransmitter released by postganglionic axons
oSympathetic – most release noradrenaline (adrenergic)
oParasympathetic – release acetylcholine (muscarinic receptors)
the adrenal medulla
The role of the adrenal medulla in the sympathetic division –
- Major organ of symp. Nervous system
- Secretes adrenaline and noradrenaline
- Stimulated to secrete by pre-ganglionic sympathetic fibres
central control of the ANS
oReticular formation exerts most direct influence
Medulla oblongata
Periaqueductal gray matter
oControl by the hypothalamus and amygdala
Hypothalamus – main integration center of the ANS
Amygdala – main limbic region for emotions
oControl by cerebral cortex
clinical manifestations of ANS
- Eg in diabetes its important
- Dizziness, dry mouth or eyes, fatigue, gastric disturbance, malnutrition, constipation and diarrhoea, sexual dysfunction
Horner’s Syndrome
- Miosis
- Ptosis (drooping eyelid)
- Lots of sweating same side of face
- Redness of conjunctiva
- From interruption of symp. Flow to that eye
- Lesion of symp fibres centrally or peripherally
-Causes…
oCarotid artery dissection, brainstem stroke, syringomyelia
Syncope
- Vasovagal syncope – simple faint, seen commonly in young people with no underlying illness
- Sudden vasodilation often caused by strong emotion
o Peripheral resistance decreases in arterioles and blood pressure falls o Cardiac rate fails to increase o Vagal stimulation leading to bradycardia and perspiration o Increased peristalsis o Yawning o Nausea o Pallor o Salivation
Orthostatic Hypotension
- Like vasovagal syncope but brought on by getting up from reclines pos. or standing still for long periods
- Mild staggering, falling, loss of consciousness
Problems with bladder control
- Prime eg of autonomic dysfunction
- Common in MS (75%)
- Main symptoms are urgency, frequency, and urge on incontinence
- Main cause is overactivity of detrusor muscle, involuntary bladder contraction gives rise to feeling of need to void immediately despite bladder vol. being low.
tests for abnormality of the ANS
-Pupil reactions
-Postural BP response
o By bedside – a fall >30mmhg systolic and >15mmhg diastolic is abnormal
-Variation of HR with deep breathing (sinus arrhythmia)
-Lacrimal function
