Nervous system Flashcards

1
Q

How is visual acuity measured? What does the fractions of a VA of 6/24 represent?

A

By using a Snellen chart viewed at a distance of 6m (20 feet) Numerator/denominator (e.g. 6/6 - normal vision; 6/24 - reduced VA) Numerator is the distance at which the chart is read; denominator is the smallest line that can be read

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2
Q

What factors influence visual acuity?

A

Optical factors - the state of the image forming mechanisms / sharpness of focus

Retinal factors - the state of the cones

Stimulus factors - illumination, brightness of the stimulus, contrast between stimulus and background, length of time exposed to stimulus

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3
Q

Why is the fovea important for visual acuity?

A

Fovea is the point where VA is the greatest

Fovea is the centre of the macula, a thinned-out rod-free portion of the retina where the cones are densely packed and each synapses on a single bipolar cell

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4
Q

By what processes does the body lose heat?

A

Radiation and conduction (70% of loss at 21 C)

Vaporization of sweat (27%)

Respiration (2%)

Urination and defecation (1%)

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5
Q

How does the body produce heat?

A

Basal metabolic processes

Contraction of skeletal muscle

Food intake

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6
Q

What temperature-regulating mechanisms are activated by the cold?

A

Shivering

Hunger

Increased voluntary activity

Increased secretion of noradr and adr

Decreased heat loss mechanism

Cutaneous vasoconstriction

Curling up

Horripilation

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7
Q

What part of the brain controls the reflex responses activated by cold?

A

The posterior hypothalamus

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