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26 Cards in this Set

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Describe the FIVE layers of the epidermis
stratum corneum - keratinised
stratum lucidum - clear layer not usually seen
stratum granulosum - keratin-producing corneum precursor cells
stratum spinosum - desmosome-rich mechanical layer
stratum basale - mitotically active
What epidermal structures are associated with hairs?
Outer root sheath (entire length), inner root sheath (deeper part), arrector pili muscles

Hair cuticles point toward surface and are apposed by root cuticles
How do sinus hairs differ from others?
Sinus hairs are tactile and contain a blood space in the sheath
What are the THREE phases of hair growth?
Anagen - normal growth, capilla provides sustenance
Catagen - no capillar, hair regresses and moults
Telogen - new hair growth and capilla formation
What is the difference between physiological and competitive antagonists?
Physiological antagonists oppose the effect of agonists (not receptor-specific)

Competitive antagonists shift the agonist concentration-effect curve right
What is tachyphylaxis?
Self-antagonism: desensitisation to a drug with repeated administrations
Describe hepatic drug metabolism
Phase I: lipophilic molecules are converted to more polar molecules

Phase II: a conjugate group is added to further increase polarity and aid excretion
Which diet types cause acid or alkali urine?
Carnivores and concentrate-fed herbivores: acidic urine
Forage-fed herbivores: basic urine
What is normal distribution?
68% of the population are less than one standard deviation from the mean

95% of the population are less than two standard deviations from the mean
What are the THREE components of a reflex arc? Where are they found?
Afferent neurones (sensory): no dendrites; cell body and long axis in PNS, short axon in CNS

Interneurones: entirely in CNS

Efferent neurones (motor): dendrites and cell body in CNS, axon in PNS
What are the THREE functions of astrocytes?
Structural support of axons
Form the blood-brain barrier
Nutrient transfer between capillaries and neurones
Describe how neurones respond to axonal injury
Wallerian degeneration of all of the axon distal to the first Node of Ranvier proximal to the injury
What is the resting potential of neurones? How is it maintained?
-70mV. Maintained by Na+/K+ ATPase (3Na out for 2K in)
How is an action potential generated in a nerve? In a muscle cell?
Neurones: opening of fast Na+ and slow K+ channels to allow depolarisation

Muscles: Opening of Na+, K+ and Ca2+ channels to open voltage-gated Ca2+ channels
What THREE factors increase speed of transmission of nerve signals?
Increasing axon diameter
Increasing membrane resistance
Saltatory conduction
What are the TWO main types of synapse
Electrical (bidirectional, through gap junctions)
Chemical (unidirectional. e.g. ACh synapses)
List the types of nerve fibre and their function, in order of size
Largest to smallest:
Ia/Ib (A-alpha): proprioception
II (A-beta, A-gamma): cutaneous
III (A-delta): temperature + pricking pain
IV (C): pain, itch, temperature
What muscle fibre type does sarcopenia (loss of strength with age) affect?
Type I - fast/glycolytic
In terms of the sarcmere, define:
Actin
Myosin
Titin
T-tubules
Troponin
Actin - thin filament
Myosin - thick filament (sliding filament action of head long actin contracts muscle)
Titin - binds myosin to Z-disc (spring-like)
Troponin - facilitates sliding filament action when Ca2+ is present
What affect does insufficient prenatal nutrition have on muscle fibre type?
Type II (slow, oxidative) is maintained in preference to type I (fast, glycolytic)
Describe the arrangement of collagen in articular cartilage
Collagen is arranged in layers at different orientations: perpendicular resists tension and parallel facilitates smooth movement
What is the function of parathyroid hormone? Calcitonin?
PTH activates osteoclasts and increases the surface area of their ruffled borders, liberating calcium

Calcitonin inactivates osteoclasts and decreases the size of their ruffled borders.
What is Wolff's law?
Wolff's law dictates the ability of cancellous/trabecular bone to achieve maximum load-bearing strength from minimum mass
How are osteoclasts formed?
Fusion of monocytes; they are multinuclear
What is the function of osteocytes?
Perceive strain and recruit osteoblasts and osteoclasts as required
What changes occur with disuse of bones in juveniles? In adults?
Diameter of bone is reduced in juveniles, cortex is widened in adults.