Physiology of Excitable cells - Neuroanatomy

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3 Types of neurons
sensory - touch, smell, taste, motor - control muscle action, inter-neuron - connect one neuron to another
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Glial cells
most abundant cell types in CNS, maintain homeostasis, form myelin, and provide support and protection for neurons, e.g. oligodendrocytes, microglia, astrocytes and Schwann cells
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Astrocytes
cellular extensions - interact with synapses and blood vessels, control composition of extracellular space to allow neuronal function, form scar tissue after injury
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Microglia
Brain macrophages - clear infection and debris
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Oligodendrocytes
cellular extensions form insulating myelin sheath around axons to allow rapid nerve impulse conduction
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Myelination
Flattened extensions of plasma membrane used to form insulation around axonal internodes - facilitates axonal conduction by greatly decreasing current leakage from internodes and by focusing ion channels at nodes
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Myelination in CNS
by oligodendrocytes, one oligodendrocyte can myelinate several internodes
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Myelination in PNS
by Schwann cells, one schwann cell myelinates a single internode
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Forebrain
cerebral cortex, basal ganglia, thalamus, hypothalamus
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Midbrain
colliculi, substantia nigra
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Hindbrain
cerebellum, pons, medulla
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Brain-stem
medulla, midbrain, pons
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Spinal cord
cerebrospinal fluid, dorsal root ganglia, spinal nerves contain both efferent and afferent axons.
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Brain
covered by meninges, CSF, inter capillary tight junctions and glial end feet contribute to blood brain barrier. 4 lobes - frontal, parietal, occipital, temporal
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White matter
made of axons connecting different parts of grey matter to each other, white because of the myelin that surrounds the nerve fibres
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Grey matter
contains cell bodies dendrites and axon terminals of neurons- where all synapses are.
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Somatosensory system
processes info such as pain temperature touch position and vibration - received through receptors then processed by neuronal pathway
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Dermatome
region of skin innervated by dorsal roots from one spinal segment- mainly supplied by single spinal nerve
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Ascending pathways
afferent aB fibres enter spinal cord and ascend ipsilateral dorsal column - synapse 1 at medulla, secondary afferents decussate - synapse 2 at thalamus, tertiary afferents make synapse 3 at primary sensory cortex
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Thalamus
relay motor and sensory signals to cerebral cortex
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Homunculus
distorted representation of human body based on neurological map of the areas and proportions of human brain dedicated to processing motor functions or sensor functions for different parts of the body
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Parasympathetic division
preganglionic nuclei in medulla and sacral cord - ganglia in viscera have cholinergic effects
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Sympathetic division
preganglionic nuclei in the thoracic and lumbar cord - ganglia in paravertebral chain have adrenergic effects - prepares for fight or flight
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Hypothalamus and Posterior pituitary
head ganglion of autonomic nervous system, posterior pituitary is an extension of hypothalamus via infundibulum, hypothalamus secretes vasopressin and oxytocin via posterior pituitary
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The motor unit
Alpha motoneuron and the group of skeletal muscle fibres innervated by it. Groups of motor units work together to coordinate contractions of single muscle
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Descending signal pathways
pathway that goes down spinal cord and allows brain to control movement of body below the head - ventromedial and lateral
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Ventromedial pathway
ventral face of cord and medial - control of posture and locomotion - controlled by brain stem
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Lateral pathway
voluntary movement of distal muscles, controlled by cortex of brain
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Corticospinal tract
white matter motor pathway starts at cerebral cortex, decussates in medulla to its target lower motor neurons, CST controls voluntary movement of distal muscles, conduction block in CST by injury/MS causes paralysis
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Corticobulbar tract
two neuron white matter neuron pathway connecting motor cortex to medullary pyramids in medulla- talking and moving head. death of lower motor neurons occurs in spinal muscular atrophy - paralysis
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cortical control of voluntary movement
engages most of frontal and parietal lobes, 2 important circuits involve - basal ganglia and cerebellum. Parkinson’s - death of basal ganglia neurons, Spinocerebellar ataxias - death of basal ganglia neurons
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Hippocampus
removal of basal temporal lobes - stops epileptic seizures but causes profound amnesia, but still able to learn new habits - Hippocampus = role in declarative memory (memory of facts and events)
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Limbic system
includes amygdala (key region - emotion), hippocampus and cingulate cortex, lesions - reduced emotion, electrical stimulations - fear, violent aggression
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Progression of grey matter damage in Alzheimer’s disease
before clinical signs - neuronal loss from entorhinal cortex, 15-20 years later - lesions spread to hippocampus (mild memory loss), 15-20 years later - entire temporal lobe, much of frontal and parietal lobes affected, profound amnesia mood changes
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Neural dysfunction
white matter - interrupted axonal conduction, grey matter - death of neurons. injury, stroke, infection, neural tumour
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Diseases primarily affecting white matter
MS - CNS inflammatory demyelination, Paraplegias - distal degeneration of spinal cord tracts, Neuropathies - distal degeneration / demyelination of peripheral nerve
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Diseases primarily affecting grey matter
motor neuron diseases - spinomuscular atrophy, cerebellar disease - spinocerebellar ataxias, basal ganglia diseases - Huntingdon’s, Parkinson’s, temporal/frontal lobe diseases - Alzheimer’s
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Other cards in this set

Card 2

Front

most abundant cell types in CNS, maintain homeostasis, form myelin, and provide support and protection for neurons, e.g. oligodendrocytes, microglia, astrocytes and Schwann cells

Back

Glial cells

Card 3

Front

cellular extensions - interact with synapses and blood vessels, control composition of extracellular space to allow neuronal function, form scar tissue after injury

Back

Preview of the back of card 3

Card 4

Front

Brain macrophages - clear infection and debris

Back

Preview of the back of card 4

Card 5

Front

cellular extensions form insulating myelin sheath around axons to allow rapid nerve impulse conduction

Back

Preview of the back of card 5
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