SA Medical - General Medicine And Imaging of Disease

Anterior horn (spinal cord) Latin cornu anterius medullae spinalis Gray's subject #185 753

Cerebral Cortex Basal Ganglia Limbic System Cingulate Gyrus Thalamus Hippocampus Amygdala Brain function Ability to generate information and output signals in the absence of external input. Three systems that influence output by motor systems: the sensory system monitors internal and external environments and initiates reflex responses a cognitive system voluntary responses a behavioural state system sleep-wake cycles and intrinsic behaviours The Cerebral cortex is organised into functional areas There are three functional specialisations: Sensory areas - sensory inputs Motor areas - direct muscle movement Association areas - integrate sensory and motor input and direct voluntary behavious Cerebral lateralization of function or left-right brain dominance. Neurons display a level of plasticity.  Sensory information is Integrated in the Spinal Cord and Brain Primary Somatic Sensory Cortex touch, temperature, pain, itch, and body position Visual Cortex O

The diencephalon is the second division of the forebrain. It is a small area situated between the cerebral hemispheres.   The diancephalon is divided into the Thalamus and Hypothalamus, and has two endocrine structures - the Pituitary and the Pineal Gland. The Diencephalon: Thalamus Integration, processing, and relay of sensory from the ascending tracts to the cortical areas The thalamus receives  receives  sensory fibers from the optic tract, the ears, and spinal cord,   Motor fibers from the cerebellum Projects fibers to the cerebrum where it is processed Hypothalamus - the center for homeostasis - Temperature control emotional states control over the autonomic nervous system and integration with endocrine functions - sex, water balance, temperature control, feeding activity (Hunger and Thirst) The Hypothalamus: receives input from the cerebrum, the reticular formation, and other sensory receptors output to the thalamus to various effectors Metathalamus Medi

The cerebellum is the control centre for the coordination of:  voluntary muscle activity,  equilibrium, and  muscle tonus.  It does not initiate movement and therefore a person who has cerebellar activity does not become paralysed. Rather his movements are: slow, clumsy, temulous and uncoordinated The muscles may be hypotonic and the person unable to walk steadily and tends to sway, stagger and fall. To carry out its three functions, the cerebellum needs to receive information concerning:  what "orders" are being sent from the cerebral motor cortex the "equilibrium state of the body the position and state of muscles and joints and the amount of tonus present. Inputs are then integrated and feedback for regulation  and control motor activity, equilibrium and muscle tonus. Cerabellar Organisation: Lobes and Regions  The cerebellum has 3 major Lobes, each associated with distinct syndromes if damaged: Anterior Lobe Posterior Lobe Flocculonodular lobe F

The Tympanic Membrane and the Ossicular System Sound from the tympanic Membrane to the Cochlea Tympanic Membrane, Malleus, Incus, Stapes, Oval Window - the ossicular chain. Malleus is also attached to the tensor tympani muscle. Impedance matching between sound waves in air and sound waves in the cochlear fluid is mediated by the ossicular chain. Sound is not amplified by increasing movement at the stapes, but increasing force of movement  at the stapes. Increasing pressure, increases the vibration of the fluid in the membranous labyrinth - via the oval window.  Impedance matching between air waves and fluid waves.  Contraction of the stapedius and the tensor tympani muscles attenuates sound conduction This is the same mechanism used to diminish the sensitivity to ones own speech Increases the rigidity of the stapes, and therefore the ossicular chain. Sound Transmission Through Bone Conduction The cochlea is embedded in bone, vibration of the skull can directly stimu

The Primary Sensation of Taste Taste Treshold Taste Buds and Their Function Transmission of Taste Signals in the Central Nervous System The Sense of Smell Olfactory Epithelium Stimulation of the Olfactory Receptor Cells Search for the Primary Sensations of Smell Transmission of Smell Signals into the Central Nervous System  

The Optics of Vision Physical Principles of Optics Slower velocity than air. Refractive Index of a transparent substance is the ratio of its velocity in air to the velocity in the transparent object. Perpendicular - The direction light travels is always perpendicular to the wave front, When light passes through an angulated surface, it is bent (refracted) at some angle if the refractive indices of the two media are different. The angle depends on the refractive index of the barrier material and the angle between the two surfaces.  Refractive Principles and their Application to Lenses    A Convex Lens - Converge Light that passes the lens perimeter is refracted - bent toward the center - to make perpendicular to the wavefront.    A Concave Lens - divergence Light through the lens perimeter are refracted away from the midline - bent away - to make themselves perpendicular to the wave front.    Focal Length of the Lens Focal Length of a lens is the distance beyound

Pain Sensation: fast and Slow Pain Classification Fast Pain Slow Pain All pain receptors are free nerve endings Three types of Stimuli Pain receptors are activated by mechanical, thermal and chemical stimuli Mechanical and thermal stimuli - fast pain Chemical stimuli - slow pain No adaptation, progressively greater as the pain stimulus  continues, this is called hyperalgesia Two separate pathways of Pain transmission A-delta fibers fast - 6 to 30m/s - Mechanical and thermal stimuli C-Fibers slow - 0.5 to 2m/s  neospinothalamic tract - A-delta fibers paleospinothalamic tract - C-fibers The neospinothalamic tract is used in pain localisation Activity in the paleospinothalamic system may impart unpleasant perception of pain. paleospinothalamic pathway Brain and Spinal Cord: Internal Pain Suppression system The periaqueductal gray  the periadueductal gray of the midbrain and the rostral pons receives input from the ascending pain pathways in addition to descending proje