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MCAT BIOLOGY FLASHCARDS > MCAT BIO CH. 8 PART 2 > Flashcards

MCAT BIO CH. 8 PART 2 Flashcards

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1
Q

How does light enter the eye? What happens to light when it passes through the cornea?

A

Passing through the cornea

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2
Q

What happens to light when it passes through the cornea?

A

Refracted; refractive index of the cornea is higher than that of air

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3
Q

What is the sclera? (Based on vision)?

A

The white of the eye

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4
Q

Where is the choroid located? What does it contain? What’s it purpose? (Based on vision)?

A

Beneath the sclera; contains darkly pigmented cells; absorbs excess light within the eye

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5
Q

Where is the retina located? What is its purpose? (Based on vision)

A

Beneath the choroid; the surface upon which light focuses

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6
Q

What is just inside the cornea? What does it contain? (Based on vision)

A

The anterior chamber; fluid called aqueous humor

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7
Q

What does the iris do? (Based on vision)

A

Muscles in the iris regulate the diameter of the pupil

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8
Q

What is located just behind the iris? What does it contain? (Based on vision)

A

Posterior chamber; aqueous humor

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9
Q

What is located at the back of the posterior chamber?(Based on vision)

A

Lens

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10
Q

What is the purpose of the lens? (Based on vision)

A

Fine-tune the angle of incoming light so beams are perfectly focused on the retina

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11
Q

How is the curvatures of the lens varied (the refractive power)? (Based on vision)

A

By the ciliary muscle

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12
Q

As light passed through the lens, where does it go through to reach where? (Based on vision)

A

Goes through the vitreous chamber en route to the retina

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13
Q

What does the vitreous chamber contain? (Based on vision)

A

A thick jelly-like fluid called the vitreous humor

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14
Q

What does the retina contain? (Based on vision)

A

Photoreceptors known as rods and cones

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15
Q

What type of cells do the rods and cones of the retina synapse with? (Based on vision)

A

Bipolar cells

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16
Q

What are bipolar cells type of nerve cells? (Based on vision)

A

Only have one axon and one dendrite

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17
Q

What type of cells do bipolar cells from the rod and cones synapse, synapse with? (Based on vision)

A

Ganglion cells

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18
Q

Which nerve does the ganglion cells stimulate? (Based on vision)

A

The optic nerve which travels from each eye towards the occipital lobe of the brain

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19
Q

What is the optic disk of the retina? (Based on vision)

A

The point where many axons from ganglion cells converge to form the optic nerve

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20
Q

What is the blind spot (optic disk)? (Based on vision)

A

Contains no photoreceptors

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21
Q

What is the macula? (Based on vision)

A

Portion at the center of the retina that makes vision focused

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22
Q

What is in the center of the macula? (Based on vision)

A

Fovea centralis (focal point)

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23
Q

What does the fovea centralis only contain and what is it important for?

A

Contains only cones and responsible for extreme visual acuity

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24
Q

What are special about opsin that are located in rods and cones?

A

Special pigment proteins that change their tertiary structure upon absorbing light

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25
Q

What are opsin proteins bound to, based on vision?

A

Bound to one molecule of retinal, derived from Vitamin A

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26
Q

What happens in the dark when the rods and cones are resting, based on the opsin protein and retinal molecule? (Based on vision)

A

Retinal has several trans double bonds and one cis double bond to keep sodium channel open with opsin

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27
Q

Since the retinal has several trans double bonds and one cis double bone to keep sodium channels open, the cell remains…..? (Based on vision)

A

Depolarized

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28
Q

What happens when there is absorption of the photo light, based on retinal and opsin?

A

Retinal is covered to all trans-for which triggers reactions that close sodium channels and cell is hyper polarized

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29
Q

What neurotransmitter is released by rods and cones (photoreceptors) in the dark?

A

Glutamate onto the bipolar cells

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30
Q

What happens in the light to the photoreceptors rods and cones based on the neurotransmitter they release?

A

Glutamate is released less or stopped, cell is hyper polarized

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31
Q

Where can the bipolar cells be located?

A

On center or off center

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32
Q

The bipolar cells that are on center, what happens in the dark and in the light?

A

Dark: Glutamate released and inhibits on center bipolar cells
Light: Inhibition stops, bipolar cell increases release of neurotransmitter

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33
Q

The bipolar cells that are off center, what happens in the dark and in the light?

A

Dark: Stimulated by glutamate release
Light: Inhibited as glutamate stops being released

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34
Q

What is night vision accomplished by?

A

Rods

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35
Q

Why is night vision accomplished by rods?

A

More sensitive to dim light and motion and more concentrated in the periphery of the retina

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36
Q

What is color vision accomplished by?

A

Cones

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37
Q

Why is color vision accomplished by cones?

A

Require abundant light and are more concentrated in the fovea

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38
Q

Color depends on the presence of there different types of cones; what are they?

A

Absorb blue, tree and red light

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39
Q

What is normal vision?

A

Emmetropia

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40
Q

What is myopia?

A

Too much curvature causes light to be bent too much and to be focused in front of the retina (nearsightedness)

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41
Q

What is hyperopia?

A

Focusing of light behind the retina

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42
Q

How can myopia be corrected?

A

By concave lens which cause the light rays to diverge slightly before they reach the cornea

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43
Q

How can hyperopia be corrected?

A

By a convex lens which causes light rays to converge before reaching the Cornes

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44
Q

What is presbyopia?

A

Inability to accomodate (focus)

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45
Q

How does presbyopia happen?

A

Results from loss flexibility of the lens which occurs with aging

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46
Q

Where is the location of neurons that fir in response to visual information?

A

Visual cortex

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47
Q

What is the feature detection theory?

A

Why different areas of the brain are stimulated when looking at different things

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48
Q

What is parallel processing based on process of vast amounts of visual information?

A

Many aspects of a visual stimulus are processed simultaneously

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49
Q

What’s the absolute threshold based on general sensory processing?

A

Minimum stimulus intensity required to activate a sensory receptor

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50
Q

What is the difference threshold based on general sensory processing?

A

The minimum noticeable difference between any two sensory stimuli

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51
Q

What is Weber’s law?

A

Two stimuli must differ by a constant proportion in order for their difference to be perceptible

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52
Q

What is signal detection theory?

A

Predicting how and when someone will detect the presence of a given sensory stimulus amidst all other sensory stimuli in the background

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53
Q

What are the four possible outcomes of the signal detection theory?

A
  1. Hit
  2. Miss
  3. False alarm
  4. Correct rejection
54
Q

What is the hit theory of the signal detection theory?

A

Signal is present and was detected

55
Q

What is the miss theory of the signal detection theory?

A

Signal was present but not detected

56
Q

What is the false alarm theory of the signal detection theory?

A

Signal was not present but the person thought it was

57
Q

What is the correct rejection theory of the signal detection theory?

A

The signal was not present and the person did not think it was

58
Q

What do gestalt psychologists believe?

A

Believe that the whole exceeds the sum of its parts

59
Q

Revert the gestalt psychologists belief in regards to humans, what does it mean?

A

When humans perceive objects, rather than seeing lines angles and colors they perceive it as a whole

60
Q

What is bottom-up processing?

A

Begins with the sensory receptors and works up to the complex integration fo information

61
Q

What is top-down processing?

A

The brain applies experience and expectations to interpret sensory information

62
Q

What does the endocrine system regular?

A

Physiology over a period of hours to days

63
Q

What is a hormone and what does it do?

A

A molecule secreted into the bloodstream by an endocrine gland and has effect on distant large cells

64
Q

What is the endocrine gland?

A

Ductless gland whose secretory products are piked up y capillaries supplying blood to the region

65
Q

How do exocrine gland secrete its products?

A

Into the external environment by way of ducts, which empty into the gastrointestinal lumen of the external world

66
Q

What is a hormone receptor?

A

A polypeptide that possesses a ligand-specific binding site

67
Q

What is autocrine activity?

A

Some signaling molecules modify the activity of the cell which secreted them

68
Q

What are the two groupings of hormones?

A
  1. Hydrophilic hormones

2. Hydrophobic hormones

69
Q

What are hydrophilic hormones?

A

Peptides and amino-acid derivatives

70
Q

What are hydrophobic hormones?

A

Steroid hormones bind to receptors in the cellular interior

71
Q

Where are peptide hormones synthesized?

A

Into the rough ER and modified the Golgi

72
Q

How are peptide hormones released?

A

Exocytosis

73
Q

What happens when peptide hormones are released in the bloodstream?

A

Dissolve as they are hydrophilic

74
Q

What does hydrophilicity of the peptide hormones prevent them from doing and what must they do?

A

They cannot cross biological membranes and required to communicate with the interior of the target cell by way of second messenger cascade

75
Q

What is the receptor of the peptide hormone?

A

Polypeptide with a domain on the inner surface of the plasma membrane that contains the ability to catalytically activate a second messenger

76
Q

What is the end result fo the second messenger based on peptide hormones and receptor?

A

Function of proteins in the cytoplasm is changed

77
Q

What is a key feature of second messenger cascade, based on peptide hormones and receptors?

A

Signal amplification which allows a few activated receptors to change the activity of many enzymes in the cytoplasm

78
Q

Because peptide hormones modality the activity of existing enzymes in the cytoplasm, how are their effects?

A

Done rapidly, minutes to hour from the time of secretion

79
Q

What are the two subgroups within the peptide hormone category?

A
  1. Polypeptides

2. Amino acid derivatives

80
Q

What is an important example of the polypeptide hormone?

A

Insulin

81
Q

Along with a complex tertiary structure, what does insulin contain?

A

Disulfide bridges

82
Q

What is insulin secreted by?

A

B cells of the pancreatic islets of Langerans in response to elevated blood glucose

83
Q

What does insulin bind to and what does it cause?

A

Binds to a cell-surface receptor with a cytoplasmic domain possession protein kinase activity

84
Q

What are amino acid derivatives?

A

Derived from single amino acids and contains no peptide bonds

85
Q

What is an example of an amino acid derivative?

A

Tyrosine the parent amino acid for the catecholamines (epinephrine) and the thyroid hormones

86
Q

What are catecholamines behave as?

A

Like peptide hormones while the thyroid hormones have more like steroid hormones

87
Q

What is epinephrine?

A

A small cyclic molecule secreted by the adrenal medulla upon activation of the sympathetic nervous system

88
Q

What does epinephrine do?

A

Binds to cell-surface receptors to trigger a cascade that makes second messenger cyclic adenosine monophosphate (cAMP) + activates protein kinases

89
Q

What do thyroid hormones do?

A

Enter cells, bind to DNA and activate transcription of genes involved in energy mobilization

90
Q

What does thyroid hormones incorporate in their structure?

A

Iodine

91
Q

What are steroid hormones synthesized from?

A

Cholesterol in the smooth endoplasmic reticulum

92
Q

Why can steroids diffuse through biological membranes?

A

Due to their hydrophobicity

93
Q

Since steroids are hydrophobic they can be dissolved in plasma. T/F

A

False

94
Q

Steroid hormones exerts its effects upon target cells by…?

A

Diffusing through the plasma membrane to bind with a receptor in the cytoplasm

95
Q

What happens after the steroid hormones has bounded to the receptor?

A

The steroid-hormone receptor complex is transported into the nucleus where it acts as a sequence-specific regular of transcription

96
Q

Why are steroid hormones effects exerted slowly, over a period of days and persist for days and weeks?

A

Because steroid hormones must modify transcription to change the amount and/or type of proteins in the cell

97
Q

Steroids regulating sexuality, reproduction and development are secreted by…?

A

Testes, ovaries and placenta

98
Q

Steroids regulating water balance and other processed are secreted by….?

A

Adrenal cortex

99
Q

Endocrine glands other than steroid hormones, secrete….?

A

Peptide hormones

100
Q

Although thyroid hormones is derived from an amino acids, its mechanism of action more closely resembles…?

A

That of the steroid hormones

101
Q

What is a physiological endpoint?

A

Point that much be maintained at constant levels

102
Q

What are tropic hormones?

A

Hormones that regulate hormones

103
Q

What is the role of the adrenocorticotropic hormone (ACTH)?

A

To stimulate increased activity of the portion of the adrenal gland called the cortex

104
Q

What is the cortex of the adrenal gland responsible for?

A

Secreting cortisol (and other steroid hormones)

105
Q

What does ACTH stand for?

A

Adrenocorticotropic hormone

106
Q

Why is ACTH considered a tropic hormone?

A

It regulates another regulator (cortisol)

107
Q

What does cortisol regulate?

A

Regulates physiological endpoints, including cellular responses to stress and glucose

108
Q

Most feedback in the endocrine system are____?

A

Negative feedbacks or feedback inhibition

109
Q

The portion fo the brain which controls such of the endocrine system is the _______?

A

Hypothalamus

110
Q

How does the hypothalamus control the endocrine system?

A

By releasing tropic hormones that regulate other tropic hormones; called releasing and inhibiting factors

111
Q

What does the hypothalamus specifically control and why does that relate to the endocrine system?

A

Controls the anterior pituitary and the anterior pituitary controls most of the endocrine system

112
Q

What is the name of the endocrine control center?

A

Hypothalamic-pituitary control axis

113
Q

What’s the hypothalamic-pituitary portal system?

A

The blood supply, a special miniature circulatory system provided for efficient transport of hypothalamic releasing and inhibiting factors

114
Q

What is a hypophysis?

A

Another name for pituitary gland

115
Q

What is the arrangement of the capillaries in a portal system?

A

Consists of two capillary beds in sequence, allowing for direct communication between nearby structures

116
Q

What are the two halves of the pituitary gland?

A
  1. Anterior pituitary: Adenohypophysis

2. Posterior pituitary: Neurohypophysis

117
Q

What is the anterior pituitary and what does it do?

A

Normal endocrine gland; controlled by hypothalamic releasing and inhibiting factors (tropic hormones)

118
Q

What is the posterior pituitary and what does it do?

A

Composed of axons with descend from the hypothalamus

119
Q

Based on the posterior pituitary, where are the neurons that allow axons to descend?

A

The hypothalamic neurons that send axons down to the posterior pituitary; an example of neuroendocrine cells

120
Q

What are neuroendocrine cells?

A

Neurons which secrete hormones into the bloodstream

121
Q

What are the hormones from the posterior pituitary?

A

ADH (antidiuretic hormone or vasopressin)

122
Q

What is the purpose of ADH?

A

Causes the kidney to retain water during times of this and oxytocin

123
Q

What does the retaining of oxytocin help with, based n ADH function?

A

Causes milk let-down for nursing’s and uterine contractions during labour

124
Q

Are hormones made by axon termini in the posterior pituitary or by somas in the hypothalamus?

A

Hypothalamic and pituitary hormones are peptides, and since there’s no protein synthesis at axon termini, the posterior pituitary doesn’t make any hormones but stores them

125
Q

Thyroid hormone is produced from where?

A

Produce from the AA tyrosine in the thyroid gland

126
Q

What is the structure of the thyroid hormone?

A

Comes in two forms, with three or four iodine atoms per molecule

127
Q

How is the production of the thyroid hormone increased?

A

Increased by thyroid stimulating hormone from the anterior pituitary

128
Q

What is the mechanism of action of thyroid hormone?

A

Bind to a receptor in the cytoplasm of cells that then regulates transcription in the nucleus

129
Q

What is the effect of the regulation of thyroid hormone based on regulating transcription in the nucleus?

A

Increase the overall metabolic rate and body temperature, and in children stimulate growth

130
Q

What is cortisol secreted by?

A

Adrenal cortex in response to ACTH from the pituitary

131
Q

The effects of cortisol help the body deal with _____?

A

Stress

132
Q

What does cortisol help mobilize and store?

A

Mobilize glycogen and store fat to provide energy during stress and increase protein consumption

MCAT BIOLOGY FLASHCARDS (23 decks)

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