intro to neurology Flashcards
CNS overview
Nervous System (NS) is comprised of 2 parts:
Central Nervous System (CNS)
Peripheral Nervous System (PNS)
Central Nervous System
Brain & Spinal Cord
Peripheral Nervous System
Links CNS to peripheral structures via nerves
Receives sensory information
Neuron function
Receives & integrates incoming sensory information from sensory receptors & other neurones.
Transmits information to other neurones & effector organs.
types of neuron
spinal reflex is an example of …
afferent: info from periphery to CNS sensory neurons Efferent: infor from CNS to periphery Motor neurons Interneurons - in CNS
- spinal relfex= eg. of interplay between diff types of neurons
brain - cerebrum
Cerebrum
2 cerebral hemispheres separated by longitudinal fissure, and corpus callosum
Gyri – bumps on surface
Sulci – grooves between gyri (e.g. central sulcus)
Fissures – deeper grooves
Lobes – frontal, parietal, occipital, temporal
Cerebral cortex – thin layer (6mm) of grey matter over surface of the cerebrum
brain - lobes/ cerebral cortex
frontal lobe
Lobes/Cerebral Cortex
Frontal lobe – anterior cortex, posterior boundary central sulcus, lateral boundary lateral fissure. Divided into prefrontal area (most anterior - involved in elaboration of thought, emotions, creativity, executive function), pre-motor area (involved in co-ordination of movement ) & motor area (most posterior motor cortex - controls specific muscles, fine movements). Specialist Broca’s Area (involved in the coordination or programming of motor movements for the production of speech sounds).
parietal lobe
Parietal lobe – behind central sulcus extending to parieto-occipital sulcus, lateral boundry lateral fissure. Involved in somesthetic sensations (e.g. Touch, pressure, temperature). Divided into primary area (post central gyrus, receives signals directly from sensory receptors), secondary area (lies behind primary area, receives partly processed information from deeper structures & primary area)
occipital lobe
Occipital lobe – most posterior lobe has no natural boundaries on its lateral aspect. Involved in vision. Primary visual area receives input from the optic tract via the thalamus. Secondary visual areas integrate visual information, giving meaning to what is seen by relating the current stimulus to past experiences and knowledge.
temporal lobe
Temporal lobe - inferior to the lateral fissure & anterior to the occipital lobe. Separated from the occipital lobe by an imaginary line. Associated with auditory processing and olfaction. It is also involved in semantics, or word meaning. Specialist Wernicke’s Area plays a critical role in the ability to understand and produce meaningful speech. Heschl’s Gyrus (anterior transverse temporal gyrus/primary auditory area ) is the area in the temporal where sound first reaches the brain. 2 secondary auditory areas, part of Wernicke’s area, which make important contributions to the comprehension of speech. Inferior portions of the temporal lobe are involved in short-term memory.
organisation of the brain
frontal lobe - motor cortex, prefrontal cortex, Broca’s aread
Parietal lobe - sensory cortex, parietal association cortex
Temporal lobe - auditory cortex, Wernicke’s area
Occipital lobe - visual cortex
Insula (Insular cortex/Island of Reil): sometimes referred to as the 5th lobe. Portion of the cerebral cortex folded deep within the lateral sulcus between the temporal lobe & the frontal lobe. Thought to be involved in consciousness & play a role in diverse functions usually linked to emotion or the regulation of homeostasis. Functions include perception, motor control, self-awareness, cognitive functioning, & interpersonal experience. In relation to these it is involved in psychopathology. Recently thought to be involved in chronic pain perception.
Brain - white and grey matter
White & Grey Matter
CNS distribution of nerve cell bodies & their processes.
Grey matter = cell bodies
Central area of spinal cord, surface of cerebral hemispheres (cortex), interspersed clusters within the brain (basal ganglia)
White matter = nerve processes / axons
Association fibres – same side, allow communication between various parts of the cerebral cortex on the same side.
Commissural fibres – cross mid-line, allow communication across the hemispheres.
Projection fibres – project from lower regions of brain to cerebral cortex and vice versa.
Basal ganglia
Masses of grey matter at the base of the cerebral hemispheres.
Links cerebrum with spinal cord via internal capsule (major fibre pathway).
Function: Crude motor activities, later refined by cerebral cortex. Also involved in timing and scaling of movement, & relaying information.
brainstem
Medulla Oblongata
Pyramids – 2 longitudinal columns found anteriorly. Carry corticospinal fibres from cerebral peduncles of mesencephalon to spinal cord. Fibres cross to opposite side in inferior medulla – decussation of the pyramids. Therefore, left cerebral cortex controls muscle contraction on right of body.
Olive - protrudes from anterolateral medulla lateral to pyramids. Deep to this lies the inferior olivary nucleus – relays signals from basal ganglia & spinal cord to cerebellum.
Medial lemniscus – large tract relaying signals from spinal cord to cerebrum. Decussation here results in left side of brain being excited by sensory stimuli on right of body.
Also have nuclei of VIII, IX, X, XI, XII cranial nerves, reticular formation, CV centre, medullary rhythmicity area
pons
Bridge connecting spinal cord with the brain and parts of the brain with one another.
Corticospinal & corticopontine fibres pass from mesencephalon via cerebral penduncles. Corticospinal fibres pass to the medulla, while corticopontine fibres terminate in the pone synapsing with multiple pontine nuclei.
Transverse fibres cross to opposite side of the ventral pons & then circle back around the lateral sides of the pons to form the middle cerebellar peduncles that extend to the cerebellar hemispheres.
Motor cortex -> corticopontine fibres -> ontine nuclei -> transverse fibres/middle cerebellar peduncle -> cerebellum.
Pons contains nuclei of V, VI, VII, VIII cranial nerves, & nuclei of pneumotaxic & apneustic areas (medullary rhythmicity area) which control respiration.
cerebellum
Similar in structure to the cerebrum, 2 hemispheres separated by the Vermis (midline section), compact folds on surface (folia).. Each hemisphere divided into 3 lobes separated by deep fissures: Flocculonodular lobe (Vestibulo-cerebellum) – connected to the vestibular apparatus & functions in balance mechanisms. Anterior lobe (Spino-cerebellum) – command centre of the cerebellum, corrects movement errors & receives incoming information form higher centres & the periphery. Posterior lobe (Cerebro-cerebellum) – houses memory of movement & involved in learning, planning & timing of movement.
functions Functions: Control of posture & equilibrium Co-ordination of movement Prevention of overshooting Control of ballistic movements Planning & timing of movement Role in learning & storage of movement patternsAbnormalities Dysmetria Past pointing Ataxia Dysarthria Intention Tremor Cerebellar Nystagmus Hypotonia
Limbic system
Interconnected group of brain structures in Frontal lobe Temporal lobe Thalamus Hypothalamus Neuronal pathways Associated with emotions, moods & motivation.
CNS - tracts
Tracts
Nerve processes with similar connections + functions follow same course / run in pathways / tracts
Ascending
Dorsal column - fasciculus gracilis & fasciculus cuneatus
Spinothalamic – pain, thermal sensations, itch, crude touch, pressure, vibration
Spinocerebellar (posterior & anterior) – muscle length, tension
Descending
Pyramidal
Corticospinal – influence motor neurons
Corticobulbar – similar to corticospinal but located near motor nuclei of cranial nerves in medulla
Spinal cord -
Lies in vertebral canal
Receives information from limbs & trunk
31 pairs spinal nerves
Spinal nerve = afferent & efferent fibres
Spinal cord ends at L1+2 / Cauda equina
Spinal meninges
Dorsal roots - carry afferent fibres
(approaching)
Ventral roots - carry efferent fibres
(exiting)
Grey & white matter - horns and tracts
PNS sensory endings effector endings peripheral nerves dermatomes myotomes
Receives sensory information from the periphery & communicates to the CNS, relays information from the CNS to the periphery.
Sensory endings - special senses (hearing, vision, taste, smell, balance) & general sensation (exteroceptors, interoceptors, proprioceptors, mechanoreceptors, nociceptors).
Effector endings - Motor end plate or neuromuscular junction.
Peripheral nerves - Spinal nerves are redistributed to form peripheral nerves e.g. brachial plexus.
Dermatomes – area of skin supplied by spinal nerve.
Myotomes - group of muscles innervated by a particular spinal nerve.
Somatic nervous system
Somatic nervous system - comprises fibres going from CNS to skeletal muscle cells. Voluntary movement.
Cell bodies located in groups in brain and SC.
Large diameter / Myelinated axons.
Leave CNS skeletal muscle.
NM junction / Acetylcholine.
Activity leads to muscle contraction.
‘Motor neurons’.
autonomic nervous system
Autonomic nervous system (ANS) - nerve cells within the CNS & PNS concerned with the innervation & control of viscera, smooth muscle, cardiac muscle & secretory glands. Involuntary control.
Subdivided - sympathetic (SNS) & parasympathetic (PNS).
Fibres CNS & effector cells have 2 neurons & 1 synapse.
Synapse outside CNS in cell clusters called autonomic ganglia.
Sympathetic ganglia - close to SC paired chains of ganglia - sympathetic trunks.
Parasympathetic - lie within effector organ.
Neurotransmitters
Parasympathetic - ACh
Sympathetic - Norepinephrine
sympathetic nervous system
Sympathetic Nervous System (SNS) Thoracolumbar T1 - L2. Preganglionic neurones in lateral horn grey matter T1 - L2. ‘Flight or fight’ HR and BP bronchodilation vasodilation skeletal muscle GIT blood flow / motility Sweating and blood glucose
parasympatheitc nervous system
Cranio-sacral. Cranial nerves III, VII, IX, X & Spinal nerves S2 - S4 ‘Rest & Digest’ HR and BP bronchodilation vasodilation skeletal muscle GIT blood flow / motility Sweating and blood glucose
