NEET MDS Synopsis
The Types of muscle cells
PhysiologyThe Types of muscle cells. There are three types, red, white, and intermediate.
White Fibers
Fast twitch
Large diameter, used for speed and strength.
Depends on the phosphagen system and on glycolysis-lactic acid.
Stores glycogen for conversion to glucose.
Fewer blood vessels.
Little or no myoglobin.
Red Fibers
Slow twitch
Small diameter, used for endurance.
Depends on aerobic metabolism.
Utilize fats as well as glucose.
Little glycogen storage.
Many blood vessels and much myoglobin give this muscle its reddish appearance.
Intermediate Fibers: sometimes called "fast twitch red", these fibers have faster action but rely more on aerobic metabolism and have more endurance. Most muscles are mixtures of the different types. Muscle fiber types and their relative abundance cannot be varied by training, although there is some evidence that prior to maturation of the muscular system the emphasis on certain activities can influence their development
PHYSIOLOGY OF THE BRAIN
Physiology
PHYSIOLOGY OF THE BRAIN
The Cerebrum (Telencephalon) Lobes of the cerebral cortex
Frontal Lobe
Precentral gyrus, Primary Motor Cortex, point to point motor neurons, pyramidal cells: control motor neurons of the brain and spinal cord. See Motor homunculus
Secondary Motor Cortex repetitive patterns
Broca's Motor Speech area
Anterior - abstract thought, planning, decision making, Personality
Parietal Lobe
Post central gyrus, Sensory cortex, See Sensory homunculus, size proportional to sensory receptor density.
Sensory Association area, memory of sensations
Occipital Lobe
Visual cortex, sight (conscious perception of vision)
Visual Association area, correlates visual images with previous images, (memory of vision, )
Temporal Lobe
Auditory Cortex, sound
Auditory Association area, memory of sounds
Common Integratory Center - angular gyrus, Parietal, Temporal & Occipital lobes
One side becomes dominent, integrats sensory (somesthetic, auditory, visual) information
The Basal nuclei (ganglia)
Grey matter (cell bodies) within the White matter of cerebrum, control voluntary movements
Cauadate nucles - chorea (rapi, uncontrolled movements), Parkinsons: (dopamine neurons of substantia nigra to caudate nucles) jerky movements, spasticity, tremor, blank facial expression
The limbic system - ring around the brain stem, emotions(w/hypothalamus), processing of olfactory information
The Diencephalon
The Thalamus - Sensory relay center to cortex (primitive brain!)
The Hypothalamus
core temperature control"thermostat", shivering and nonshivering thermogenesis
hunger & satiety centers, wakefulness, sleep, sexual arousal,
emotions (w/limbic-anger, fear, pain, pleasure), osmoregulation, (ADH secretion),
Secretion of ADH, Oxytocin, Releasing Hormones for Anterior pitutary
Linkage of nervous and endocrine systems
The Mesencephalon or Midbrain -
red nucleus, motor coordination (cerebellum/Motor cortex),
substantia nigra
The Metencephalon
The Cerebellum -
Performs automatic adjustments in complex motor activities
Input from Proprioceptors (joint, tendon, muscles), position of body in Space
Motor cortex, intended movements (changes in position of body in Space)
Damping (breaking motor function), Balance, predicting, inhibitory function of Purkinji cells (GABA), speed, force, direction of movement
The Pons - Respiratory control centers (apneustic, pneumotaxic)
Nuclei of cranial nerves V, VI, VII, VIII
Myelencephalon
The Medulla
Visceral motor centers (vasomotor, cardioinhibtory, respiratory)
Reticular Formation RAS system, alert cortex to incoming signals, maintenance of consciousness, arousal from sleep
All Afferent & Efferent fibers pass through, crossing over of motor tracts
Corpus Callosum: Permits communication between cerebralhemispheres
Generalized Brain Avtivity
Brain Activity and the Electroencephalogram(EEG)
alpha waves: resting adults whose eyes are closed
beta waves: adults concentrating on a specific task;
theta waves: adults under stress;
delta waves: during deep sleep and in clinical disorders
Brain Seizures
Grand Mal: generalized seizures, involvs gross motor activity, affects the individual for a matter or hours
Petit mal: brief incidents, affect consciousness but may have no obvious motor abnormalities
Chemical Effects on the Brain
Sedatives: reduce CNS activity
Analgesics: relieve pain by affecting pain pathways or peripheral sensations
Psychotropics: alter mood and emotional states
Anticonvulsants: control seizures
Stimulants: facilitate CNS activity
Memory and learning
Short-term, or primary, memories last a short time, immediately accessible (phone number)
Secondary memories fade with time (your address at age 5)
Tertiary memories last a lifetime (your name)
Memories are stored within specific regions of the cerebral cortex.
Learning, a more complex process involving the integration of memories and their use to direct or modify behaviors
Neural basis for memory and learning has yet to be determined.
Fibers in CNS
Association fibers: link portions of the cerebrum;
Commissural fibers: link the two hemispheres;
Projection fibers: link the cerebrum to the brain stem
Nystatin
Pharmacology
Nystatin
Candida spp. are sensitive to nystatin.
Uses: Cutaneous, vaginal, mucosal and esophageal infections.
Candida infections can be treated with nystatin.
Cryptococcus is also sensitive to nystatin.
Nystatin is often used as prophylaxis in patients who are at risk for fungal infections, such as AIDS patients with a low CD4+ count and patients receiving chemotherapy.
MOA
nystatin binds to ergosterol, the main component of the fungal cell membrane. When present in sufficient concentrations, it forms a pore in the membrane that leads to K+ leakage and death of the fungus.
Procaine penicillin
Pharmacology
Procaine penicillin Procaine penicillin is a combination of benzylpenicillin with the local anaesthetic agent procaine. This combination is aimed at reducing the pain and discomfort associated with a large intramuscular injection of penicillin.
Indications
respiratory tract infections where compliance with oral treatment is unlikely ,syphilis, cellulitis
Water Acid Bases & Buffers
Biochemistry
Keq, Kw and pH
As H2O is the medium of biological systems one must consider the role of this molecule in the dissociation of ions from biological molecules. Water is essentially a neutral molecule but will ionize to a small degree. This can be described by a simple equilibrium equation:
H2O <-------> H+ + OH-
This equilibrium can be calculated as for any reaction:
Keq = [H+][OH-]/[H2O]
Since the concentration of H2O is very high (55.5M) relative to that of the [H+] and [OH-], consideration of it is generally removed from the equation by multiplying both sides by 55.5 yielding a new term, Kw:
Kw = [H+][OH-]
This term is referred to as the ion product. In pure water, to which no acids or bases have been added:
Kw = 1 x 10-14 M2
As Kw is constant, if one considers the case of pure water to which no acids or bases have been added:
[H+] = [OH-] = 1 x 10-7 M
This term can be reduced to reflect the hydrogen ion concentration of any solution. This is termed the pH, where:
pH = -log[H+]
Cementum & Cementogenesis
Dental Anatomy
Cementum & Cementogenesis
Cementum formation is called cementogenesis and occurs late in the development of teeth. Cementoblasts are the cells responsible for cementogenesis. Two types of cementum form: cellular and acellular.
Acellular cementum forms first. The cementoblasts differentiate from follicular cells, which can only reach the surface of the tooth's root once Hertwig's Epithelial Root Sheath (HERS) has begun to deteriorate. The cementoblasts secrete fine collagen fibrils along the root surface at right angles before migrating away from the tooth. As the cementoblasts move, more collagen is deposited to lengthen and thicken the bundles of fibers. Noncollagenous proteins, such as bone sialoprotein and osteocalcin, are also secreted. Acellular cementum contains a secreted matrix of proteins and fibers. As mineralization takes place, the cementoblasts move away from the cementum, and the fibers left along the surface eventually join the forming periodontal ligmaments.
Cellular cementum develops after most of the tooth formation is complete and after the tooth occludes (in contact) with a tooth in the opposite arch. This type of cementum forms around the fiber bundles of the periodontal ligaments. The cementoblasts forming cellular cementum become trapped in the cementum they produce.
The origin of the formative cementoblasts is believed to be different for cellular cementum and acellular cementum. One of the major current hypotheses is that cells producing cellular cementum migrate from the adjacent area of bone, while cells producing acellular cementum arise from the dental follicle. Nonetheless, it is known that cellular cementum is usually not found in teeth with one root. In premolars and molars, cellular cementum is found only in the part of the root closest to the apex and in interradicular areas between multiple roots.
Manipulation of Acrylic Resins
Dental Materials
Manipulation
Mixture of powder and liquid is painted onto working cast to create shape for acrylic appliance à After curing of mixture, the shape and fit are adjusted by grinding with burrs and stones with a slow-speed handpiece .Acrylic dust is irritating to epithelial tissues of nasopharynx and skin and may produce allergic dermatitis or other reactions. Grinding may heat polymer to temperatures that depolymerize and release monomer vapor. which may be an irritant
CARCINOMA IN SITU
General Pathology
CARCINOMA IN SITU
Epithelial malignancy which has not yet invaded even -the local confines viz basement membrane is termed as carcinoma in situ (intra epithelial neoplasia, pre-invasive cancer)
This lesion merges morphologically with severe dysplasia
Common sites for carcinoma-in-situ :
Cervical squamous epithelium
Oropharynx
Bronchial epithelium.
Breast ducts and lobules.
Skin, in the form of Bowen's disease.
Glans penis and vulva in the form of Erythroplasia of Queyrat