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Flashcards in the central nervous system Deck (30):

what is the skull / vertebrae

- outermost protective layer
- spinal cord runs down vertebral canal


what is the meninges

- cover entire CNS, connective tissue (membranes)
- dura mater: tough, fibrous, connective, external, two layers, periosteal (attaches to periosteum of skull), meningeal (true external covering of brain), fused but in some spaces sinuses occur (space, collect venous blood from brain)
- arachnoid: loose meshwork of fibres, contains BV
- pia mater: delicate, contains BV, directly attached to surface of brain


what is cerebrospinal fluid

- occupies space in middle layer of meninges brain cavities, brain ventricles and centre of spinal cord
- watery, clear, some cells, glucose, proteins (less than plasma), urea, lactic acid, ions, WBC's, salt, constant V
- support (brain floats in it), protection (shock absorber, cushioning), transport nutrients / wastes (nourish brain, carry signals, removes waste)
- formed by blood, circulates CNS and re-enters blood


what is the blood brain barrier (BBB)

- continuous endothelium (attached via tight junctions) of capillary walls
- maintain stable environment of brain, selective barrier, separates neurons from some blood borne substances
- no large molecules of toxic substances, protective mechanism to protect the brain from toxins or parasites
- pharmacology is developing treatments that can cross BBB


what are the ventricles of the brain

- 4 ventricles
- connected to one another and to central canal of spinal cord, lined by ependymal cells, contain CSF
- 1-2: c-shaped, in cerebral hemispheres, anterior / inferior horns, septum pellucidum (double membrane)
- 3: in the diencephalon
- 4: in the hind brain


what are the functional regions of the brain

- cerebral hemispheres
- diencephalon
- brain stem
- cerebellum


describe the structure of the cerebral hemispheres

- cerebrum: largest division, cerebrum (gray), white mater (myelinated), basal ganglia (grey, deep), 2 hemispheres, 5 lobes
- gyri: elevated ridges (pre / post central gyrus)
- sulci: small grooves, divide gyra, central sulcus divides frontal and parietal lobes
- fissure: deep grooves, divide large regions / lobes, transverse (occipital / cerebellum), longitudinal (left / right hemisphere), lateral / sylvian (temporal / parietal + frontal)


name the lobes of the brain

- frontal, parietal, occipital, insula (deep, under temporal)


what is the cerebral cortex

- gray mater outside, cell bodies, dendrites, glia and BV, convolutions = big SA
- conscious mind, aware of ourselves, communication, memory, understanding
- motor (impulses to muscles voluntary movement)
- association (interpret / integrate info, intellectual / emotional responses)
- sensory (receive / process impulses, conscious awareness of sensation)
- contralateral


what is the fontal lobe

- primary motor cortex (pre-central gyrus), conscious control of precise, skilled voluntary movement
- motor homunculi upside down caricatures, motor innervation, precise motor control (face, tongue, hands) = disproportionately large area in brain
- pre motor cortex: anterior, learned, repetitious / patterned motor skills
- contralateral


what is the parietal lobe

- primary somatosensory cortex (post central gyrus), sensory info from skin, skeletal, joints, capable of spatial discrimination (without sight)
- damage = could not recognise objects without looking at them


what is the occipital lobe

- processing, integrating, interpretation of vision and visual stimuli
- primary visual cortex: input from retina via optic nerve, does not give meaning (role of cerebellum)
- visual association area: use past visual experiences to interpret stimuli


what is the temporal lobe

- hearing, language comprehension, memory, information retrieval
- primary auditory cortex: interprets pitch, loudness, location
- auditory association area: perception of sound stimulus, whether a scream, thunder, music etc (uses memories)
- wernickes area: top back of temporal, language comprehension, give meaning to what we read / what people say
- damage: hear with no meaning


what is an ischemic stroke

- blood circulation blocked, brain tissue dies
- blockage of cerebral artery by blood clot (thrombotic)
- blockage of BV, clot moves and eventually causes blockage to brain (embolic)
- hemiplegia, sensory / speed deficits, paralysis loss of balance, vertigo, vision loss, speech impairment
- treat with drugs, stent (remove clot) if quickly administered (4.5 hours after)


what is the diencephalon

- least developed part of brain, eldest region
- thalamus: gateway to cerebral cortex (sensory info), sorts, edits, relays info, mediates sensation, motor actives, cortical arousal, learning, memory, pleasant / unpleasant stimuli
- hypothalamus: anterior, autonomic control, emotional / limbic response, regulation
- epithalamus: posterior, pineal gland (melatonin = sleep)


describe the hypothalamus in detail

- autonomic control centre: regulates visceral functions, BP, rate / force of HB, digestive tract motility, breathing rate / depth
- emotional response: ANS, perception of pleasure, fear, rage, biological rhythm and drives
- regulates: body temp (sweating / shivering), food intake (sugar / glucose / AA), water balance (osmotic pressure, thirst, kidneys)
- controls: release of hormones from anterior pituitary gland (directly attached)
- produces: ADH (reabsorption of water) and O (oxytocin, contraction of uterus, breastfeeding)


what is the brainstem made up of

- midbrain
- pons
- medulla oblongata


what is the mid brain

- between diencephalon and pons, posterior, cerebral aqueduct (connects 3-4 ventricles)
- nuclei controls CN3-4 (external muscles of eye)
- colliculi (superior visual and inferior hearing reflexes)
- substantia nigra (dark = melatonin, dopamine, damage = Parkinson's)
- red nuclei: high capillaries and iron cells, involuntary movement


what is the pons

- bridge
- connect higher brain centre and spinal cord


what is the medulla oblongata

- contains choroid plexus (produces CSF) of 4th ventricle
- just above spinal cord medulla, junction fibres cross over (decussation of pyramids = contralateral control of body)
- cranial nerves: 8 (equilibrium), 10 (parasympathetic) and 12 (tongue movement)
- autonomic reflex centre
- cardiovascular centre: activity of heart, contraction
- respiratory centre: breathing process, damage = death


what is the cerebellum

- word association and puzzle solving - coordination of fine contractions of muscles (smooth movements)
- maintenance of posture and balance (receives from inner ear, unconsciously)
- cerebellar ataxia (lack of coordination, clumsy speech, movement of limbs, gait), caused by (bleeding, ischemic stroke, multiple sclerosis, cancer, alcoholism)


describe communication within the cerebral white mater

- contains axons, communicating tracts that connect gray matter, 3 arrangements
- projection tracts: extend vertically, cerebral cortex to spinal cord
- commissural tracts: cross cerebral hemispheres, extend horizontally
- association tracts: connect different regions within same hemisphere


what are corticospinal tracts

- rapid, direct mechanism for controlling skeletal muscles
1. originate in pre central gyrus (frontal lobe)
2. pyramidal neuron = UMN form corticospinal tract (CCST)
4. exit spinal cord via anterior root
5. 10% axons dont decussate at medulla (anterior)
6. 90% axons decussate and form CST tract (lateral)
7. synapse at anterior grey horn of spinal cord, form LMN
8. reach skeletal muscles


what is the dorsal column medial lemniscal pathway

- detect discriminative touch and body position
- sensory nerve endings in skin relay sensory neurons
- cuneatus: afferent impulses, upper limbs / trunk, neck
- gracilis: impulses from lower limbs, inferior body trunk
- pass through thalamus, relayed to ventro postero lateral nucleus
- reach dorsal root ganglion and fibres run in dorsal column (posterior funiculi)


what is the spinal cord

- begins at foramen magnum ends at conus medullaris
- two way communication to and from brain
- spinal reflex centres
- protection = vertebral column / meninges
- cervical, thoracic, lumbar, sacral, coccygeal
- cervical and lumbar enlargements = supplies upper / lower limbs


describe the cross section of the spinal cord

- anterior median fissure and posterior median sulcus
- gray: inner, surrounds central canal, butterfly, cell bodies, 3 horns (posterior dorsal, anterior ventral and lateral = only in T and L regions),
- white: 3 columns (funiculi), dorsal (posterior), ventral (anterior) and lateral (lateral) = divided into sensory / motor tracts


what are 2 examples of spinal cord trauma (paralysis)

- flaccid: ventral root / horn damage, impulses do not reach muscles, no voluntary / involuntary, smaller muscles (atrophy)
- spastic: damage to UMN of primary motor cortex, spinal neurons in tact, no voluntary movement, spinal reflexes occur, shorter muscles


what is SCI

- spinal cord injury (acute / chronic)
- ASIA guidelines = motor control vs sensory assessment
- little hope in terms of treatment


what is poliomyelitis

- infection of polio virus, contact with faeces / contaminated water, worldwide epidemic
- destroys ventral horn motor neurons, no connection between spinal cord and muscles (flaccid paralysis)
- incubation period = 5-35 days


what is ALS

- amyotrophic lateral sclerosis
- 3-8 per 100000, risk increase with age (56-63)
- asymmetric, destroys ventral horn and pyramidal tract, limb weakness = greater in upper extremities
- glutamate excitotoxicity produced in CNS increase in conc. = kill neurons
- free radical toxicity or mitochondrial dysfunction