Cognitive Disorders Flashcards
(44 cards)
3 components of a neuron
a. cell body (soma)
b. dentrites (receptive)
c. axon (transmit message)
Nerve impulses
neurons generate and conduct electrical and chemical impulses by selectively changing the electrical potential of their plasma membranes and influencing nearby neurons by the release of neurotransmitters
Synapses
empty area where information exchange takes place, transmissions by chemical and electrical conduction
presynaptic: proximal to the synapse (delivering)
postsynaptic: distal to the synapse (receiving)
Neurotransmitter
- more than 46 substances
- excitatory: stimulate action potential
- inhibitory: reduce probability of action potential
- some are both
- manipulated by chemicals
Dopaminergic pathways: specific NTs in discrete groups of neuron and released in specific nerve pathways
NTs and behaviours
theorized that certain behaviours are related to NT imbalances
- excessive NT production/release
- insufficient NT production/release
- inadequate or excessive response to NT
NTs related to cognitive disorders
a. acetylcholine (ACh)
b. dopamine (DA)
c. serotonin
d. GABA and glutamate (amino acids)
e. norepinephrine (NE)
Acetylcholine (ACh)
- widely distributed
- triggers muscle contraction
- has both excitatory and inhibitory effects
= two kinds of receptors
a. nicotinic: neuromuscular junctions, nerve and muscles
(generally excitatory)
b. muscarinic: in the brain, role in memory, arousal and attention
(both excitatory and inhibitory, depending on subtype of receptor)
Clinical significance of ACh
Alzheimer’s disease is associated with a decrease in the number of ACh-secreting neurons (cholinergic hypothesis)
too much..muscle contractions
too little..paralysis
associated disorders: Alzheimer’s disease
Dopamine
- located in some areas of the brain and autonomic nervous system
- generally excitatory
- involved in voluntary movement, emotional arousal, reward motivation, inhibits unwanted movement
key role: focus and motivation
too much..schizophrenia
too little..parkinson’s, restless leg syndrome (can’t inhibit unwanted movement)
associated disorder: parkinson’s, schizo, drug addiction, depression
Serotonin
- located in many areas of the brain and spinal cord
- generally inhibitory
- involved in mood, anxiety, pain perceptions and sleep induction
- responsible for bowel movements, mood, nausea, sleep, blood clotting, bone health and sexual function
too much..confusion, twitching, dilated pupils, shivering, headache, sweating, diarrhea, irregular and fast heartbeat
too little..depression and sleep disorders, increased pain perception
associated disorders: depression
Norepinephrine
- located in many areas of brain and spinal cord and autonomic nervous system
- aka noradrenaline
- can be excitatory or inhibitory
- involved in learning and memory
- fight or flight
- stimulant drugs increase the release and block the reuptake of norepinephrine
associated disorders: depression, stress
Effect of norepinephrine
in brain:
increases arousal and alertness, promotes vigilance, enhances formation and retrieval of memory, focuses attention, increases restlessness and anxiety
in body:
increases HR and BP, triggers release of glucose, increases blood flow to skeletal muscle, decreases blood flow to GI system and promotes elimination
too much..over-arousal, aggression, impulsivity, increased SNS activity, cardiac issues
too little..under arousal, depression, cardiac issues
GABA and Glutamate (amino acids)
- GABA (gamma-aminobutyric acid) is the primary inhibitory NT in the CNS
- most neurons in CNS have GABA receptors
- glutamate is the primary excitatory NT in the CNS
- widespread in the brain and spinal cord
- associated with learning and memory
- role in schizophrenia
- drugs that block glutamate used in treatment of ALS
Clinical significance of GABA
- contributes to motor control, vision, regulates anxiety
- drugs that increase GABA used to treat epilepsy by inhibiting excessive discharge of neurons
too much..over-sedation, over-relaxing of muscles (including heart and respiration)
too little..epilepsy, seizure disorders, anxiety
associated disorders: anxiety, negative symptoms in schizo
Neuroplasticity
= long-lasting functional changes that occur when we learn new things causing changes in neural connections
= changes occur over the lifetime and vary across the lifespan
Two primary types of neuroplasticity
a. developmental (expected brain development)
b. adaptive (compensating for lost function and to maximize function following brain injury)
Dementia
- progressive failure of cerebral functions
pathophysiology
- neurodegeneration
- atherosclerosis, infarction
- trauma and lesions
- compression, increased intracranial pressure, chronic hydrocephalus
Primary vs Secondary dementia
Primary
- progressive, irreversible
- not secondary to any other disorder
Secondary
- potentially reversible
- a result of some other pathological process
Alzheimer’s Disease (AD)
- leading cause of dementia
- irreversible, no known cause
- late onset is most common, related to age and family history
- early onset, related to genetic defects
Stages
a. mild cognitive impairment (mild memory loss)
b. early stage (measurable short-term memory loss)
c. middle stage (significant forgetfulness, iADL dependent)
d. late stage (little cognitive ability, ADL dependent)
e. end stage (no significant cognitive function, non-ambulatory)
Symptoms of AD (7As)
anosognosia: loss of insight
agnosia: loss of ability to recognize
aphasia: loss of language
apraxia: loss of purposeful motor movement
altered perception: loss of ability to interpret information
amnesia: loss of memory
apathy: loss of drive or interest
Amyloid plaques
neuropathophysiological lesion of AD
= increased amounts in AD, also called dendritic or senile plaques
= deposits of neuron fragments, formed from the breakdown of a larger protein, surrounding a core of B-amyloid protein fragments
= hard, insoluble accumulation of beta amyloid protein that clump together between neurons
Neurofibrillary Tangles
neuropathophysiological lesions of AD
= a main component of tangles is a tau protein, which help bind and stabilize the structure of cells
= chemically altered tau twists to form neurofibrillary tangles inside the neuron
= harms synaptic communication between neurons
Brain Atrophy in AD
normal brain mass is about 1300-1400g in AD, brain becomes smaller in size, <1000g - shrinkage of cerebral cortex - shrinkage of the hippocampus - enlarged ventricles in brain
Main NT associated wit AD
= decreased production of ACh
- affects learning, memory and mood
= excess glutamate from damaged cells cause increased calcium uptake
Diagnosis of AD
- confirmed with microscopic examination of tissues
- often diagnosed by exclusion of other known causes of dementia (hypothyroidism, hypoglycemia, HE)
- thorough history, clinical examination and cognitive testing (MMSE, MoCA)
