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Biology > 6.6 Hormones, homeostasis and reproduction > Flashcards

6.6 Hormones, homeostasis and reproduction Flashcards

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1
Q

What do cells in the pancreas respond to?

A

Changes in blood glucose levels

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2
Q

What is initiated when glucose concentration deviates substantially from a set point of aobut 5mmolL-1?

A

Homoestatic mechanisms mediated by the pancreatic hormones insulin and glucagon are initiated

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3
Q

How many glands in the pancreas?

A

The pancreas is effectively two glands in one organ

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4
Q

What tissue is most of the pancreas?

A

Exocrine glandular tissue

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5
Q

What do exocrine glandular tissue from the pancreas do?

A

They secrete digestive enzymes into ducts leading to the small intestine

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6
Q

What is the small region of tissue that makes up the pancreas alongside exocrine glandular tissue?

A

There are small regions of endocrine tissue called islets of Langerhans dotted through the pancreas

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7
Q

What do islets of Langerhans do?

A

They secrete hormones directly into the blood stream

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8
Q

What are the two cell types in the islets of Langerhans that secrete different hormones?

A

Alpha cells and Beta cells

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9
Q

What do alpha cells in the islets of Langerhans synthesis and secrete?

A

They synthesize and secrete glucagon if the blood glucose level falls below the set point

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10
Q

What does glucagon stimulate?

A

This hormone stimulates breakdown of glycogen into glucose in liver cells and its release into the blood, increasing the concentration

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11
Q

What do Beta cells in the pancreas synthesize and secrete?

A

They synthesize insulin and secret it when the blood glucose concentration rises above the set point

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12
Q

What does insulin stimulate?

A
  • uptake of glucose by various tissues, particularly skeletal muscle and liver
  • conversion of glucose to glycogen
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13
Q

What does insulin do?

A

Reduces blood glucose concentratioin

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14
Q

How are most hormones broken down?

A

Broken down by the cells it acts upon, so its secretion must be ongoing

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15
Q

What is diabetes?

A

Is the condition where a person has consistently elevated blood glucose levels, leading to the presence of glucose in the urine

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16
Q

What are the consequences of diabetes?

A
  • Continuously elevatedglucose damages tissues, particularly their proteins
  • Impairs water reabsorption from urine while it is forming in the kidney
    -> resulting in an increase in the volume of urine and body dehydration
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17
Q

When should a person get tesed for diabetes?

A

If they need to urinate more frequently, is constantly thirsty, feels tired and craves sugary drinks

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18
Q

What are the two types of diabetes?

A

Type I and Type II

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19
Q

What is type I diabetes?

A

aka early-onset diabetes
* inability to produce sufficient quantities of insulin
* It is an autoimmune disease arising from the destruction of beta cells in the islets of Langerhans by the body’s own immune system
* causes are still being researched

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20
Q

Why is type I diabetes an autoimmune disease?

A

the body’s own immune system is detroying the beta cells in the islets of Langerhans

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21
Q

Why is type I diabetes an autoimmune disease?

A

the body’s own immune system is detroying the beta cells in the islets of Langerhans

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22
Q

What is type II diabetes?

A

aka late-onset diabetes
* inability to process or respond to insulin because of a deficiency of insulin receptors or glucose transporters on target cells
* Onset is slow
* Disease may go unnotices for many years
* Causes are not well understood
* Main risk factors are sugary, fatty diets, prolonged obesity due to habitual overeating and lack of exercise, together with genetic factors that affect energy metabolism

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23
Q

What is the current treatment of type I diabetes?

A
  • regularly testing the blood glucose concentration and injecting insulin when it is too hight or likely to become too high
  • Injections are often done before a meal to prevent a peak of blood glucose as the food is digested and absorbed
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24
Q

Why is timing of the insulin injection important?

A

Insulin molecules do not last long in the blood

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25
Q

What are some better treatments being developed for type I diabetes?

A
  • Using implanted devices that can release exogenous insulin into the blood as and when it is necesary
  • A permanent cure may be achievable by coaxing stem cells to become fully functional replacement beta cells
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26
Q

How is type II diabetes treated?

A
  • adjusting the diet to reduce the peaks and troughs of blood glucose
  • Small amounts of food should be eaten frequently rather than infrequent large meals
  • foods with high sugar content should be avoided
  • Starchy food should only be eaten if it has a low glycemic index, indicating that it is digested slowly
  • High fibre foods should be included to slow the digestion of other foods
  • Strenous exercise and weight loss are beneficial as they improve insulin uptake and action
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27
Q

What is the hormone thyroxin secreted by?

A

the thyroid gland in the neck

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28
Q

Why is the chemical structure of thyroxin unusual?

A

The thyroxin molecule contains four atoms of iodine

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29
Q

A deficiency of what prevents the synthesis of thyroxin?

A

Prolonged deficiency of iodine as the thyroxin molecule contains four atoms of iodine

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30
Q

What are the targets of the hormone thyroxin?

A

All cells in the body are targets.
Thyroxin regulates the body’s metabolic rate, so all cells need to respond but the most metabolically active such as liver, muscle and brain are the main targets

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31
Q

What does higher metabolic rate support?

A

More protein synthesis and growth and it increases the generation of body heat

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32
Q

What does thyroxin regulate?

A

metabolic rate and help control body temperature

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33
Q

In a person with normal physiology, how does thyroxin work?

A

Cooling triggers increased thyroxin secretion by the thyroid gland which stimulates heat production so body temperature rises

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34
Q

What is it called when there is a thyroxin deficiency?

A

Hypothyroidism

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35
Q

What are the symptoms of hypothyroidism?

A
  • lack of energy and feeling tired all the time
  • forgetfulness and depression
  • weight gain despite loss of appetite as less glucose and gat are being broken down to release energy by cell respiration
  • feeling cold all the time because less heat is being generated
  • constipation because contractions of muscle in the wall of the guy slow down
  • impaired brain development in children
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36
Q

What is leptin?

A

A protein hormone

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37
Q

What is leptin secreted by?

A

Adipose cells (fat storage cells)

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38
Q

What is the concentration of leptin the blood controlled by?

A

food intake and the amount of adipose tissue in the body

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39
Q

What is the target of leptin?

A

group of cells in the hypothalamus of the brain that contribute to the control of appetite

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40
Q

What does leptin bind to?

A

Binds to receptors in the membrane of the group of cells in the hypothalamus

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41
Q

What happens when adipose tissue increase?

A

blood leptin concentration rise, causing long-term appetite inhibition and reduced food intake

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42
Q

What would you expect of leptin concentration of an obese person?

A

Most obese humans have exceptionally high blood leptin concentrations

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43
Q

Why may an obese person not respond to leptin?

A

The target cells in the hypothalamus may have become resistant to lepin so fail to respond to it, even at high concentrations

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44
Q

Whats the consequence of an obese person not responding to leptin?

A
  • Appetite is not inhibited and food intake is excessive
  • More adipose tissue develops, causing a rise in blood leptin concentration but the leptin resistance prevents inhibition of appetite
  • Injection of extra leptin inevitably fails to control obesity if the cause is leptin resistance (just as insulin injections alone are effective with early-stage type II diabetes)
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45
Q

What is a very small proportion of cases of obesity in humans due to?

A

Mutations in the genes for leptin synthesis or its various receptors on target cells

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46
Q

How do people with obesity due to mutations respond to leptin injections?

A

Significant weight loss

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47
Q

Why is leptin not suitable in children and young adults?

A

It has shown to affect the development and functioning of the reproductive system

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48
Q

What are circadian rhythms?

A

rhythms in behaviour that fits into a 24-hour cycle
Humans can continue in continious light or darkness because an internal system is used to control the rhythm

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49
Q

What do circadian rhythms in humans depend?

A

two groups of cells in the hypothalamus called the suprachiasmatic nuclei (SCN)

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50
Q

What do the cells from the suprachiasmatic nuclei (SCN) do?

A

Set a daily rhythm even if grown in culture with no external cues about the time of day

In the brain:
* control the secretion of the hormone melatonin by the pineal gland

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51
Q

What is melatonin secreted by?

A

Pineal gland

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52
Q

When does melatonin secretion increase and decrease?

A

Increase in the evening and drops to a low level at down
Blood concentrations rise and fall rapidly in response to these changes in secretion

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53
Q

What feelings are caused with high and low melatonin levels?

A

High: feelings of drowsiness and promote sleep through the night
Low: encourage waking at the end of the night

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54
Q

What does melatonin contribute in terms of temperature?

A

Blocking the rise in melatonin levels reduces the drop in core body temperature

Giving melatonin artificially during the day causes a drop in core temperature

55
Q

What does the melatonin receptors found in the kidney suggest?

A

Decreased urine production at night may be another effect of this hormone

56
Q

Without light cues to indicate the time of day, what maintains the rhythm and how long?

A

SCN and pineal gland maintain a rhythm of slightly longer than 24 hours

57
Q

How is melatonin secretion responding to light?

A

The retina of the eye detects the light and passes impulses to cells in the SCN and it adjusts the melatonin secretion so that it corresponds to the day-night cycle

58
Q

What aer the symptoms of jetlag?

A
  • difficulty sleeping through the night
  • fatigue
  • irritability
  • headaches
  • indigestion
59
Q

What causes jet lag?

A

the SCN and pineal gland are continuing to set a circadian rhythm to suit the timing of the day and night at the point of departure rather than the destination

60
Q

How to combat jet lag?

A

It should only last for a few days
or melatonin can be taken orally at the time when sleep should ideally be commencing. It has shown to be effective

61
Q

What is human reproduction a fusion of?

A

Involves the fusion of a sperm from a male with an egg from a female

62
Q

What is the intial development of the embryo like?

A

It is the same in all embryos and the embryonic gonads that develop can either become ovaries or testes

63
Q

What does the developmental pathway of the embryonic gonads and thereby the whole baby depend on?

A

the presence or absence of one gene - gene SRY

64
Q

What do the embryonic gonads develop into in the presence of gene SRY?

A

Testes

65
Q

Where is the gene SRY located?

A

On the Y chromosome, so only present in 50% of embryos

66
Q

What does gene SRY code for?

A

A DNA-binding protein called TDF (testis determining factor)

67
Q

What does TDF stimulate?

A

the expression of other genes that cause testis development

68
Q

Why do embryos with 2 X chromosomes develop as ovaries?

A

Because there is no Y and so no SRY gene. TDF is therefore not produced and the embryonic gonads develop as ovaries

69
Q

In the 8th week, what happens to the testes?

A

They develop from the embryonic gonads

70
Q

At an early sage, what does the testes develop?

A

The testes develop testosterone-secreting cells

71
Q

Until when do the testosterone-secrceting cells produce testosterone?

A

until about the 15th week

72
Q

During the weeks of secretion of testosterone, what does testosterone cause?

A

During the weeks of secretion, testosterone causes male genitalia to develop

73
Q

When does the secretion of testosterone increase?

A

During purberty

74
Q

What does the increase in tetosterone stimulate at puberty?

A
  • sperm production in the testes
75
Q

What do testosterone also cause the development of besides sperm?

A

Also causes the development of secondary sexual characteristics during puberty such as:
* enlargment of the penis
* growth of pubic hair
* deepening of the voice due to growth of the larynx

76
Q

Why do female reproductive organs develop?

A

Due to the absence of fetal testosterone, the presence of maternal estrogen and progesterone that were always present in pregnancy and secreted by the mother’s ovaries and later by the placenta, develop female reproductive organs

77
Q

What occurs during puberty for females?

A
  • increased secretion of estrogen and progesterone causing the development of female secondary sexual characteristics
  • those include enlargement of the breasts and growth of pubic and underarm hair
78
Q

What are the labels

A
79
Q

What are the labels

A
80
Q

What is the function of testis?

A

produce sperm and testerone

81
Q

What is the function of scrotum?

A

Hold testes at lower than core body temperature

82
Q

What is the function of scrotum?

A

Hold testes at lower than core body temperature

83
Q

What is the function of epididymis?

A

Store sperm until ejaculation

84
Q

What is the function of epididymis?

A

Store sperm until ejaculation

85
Q

What is the function of sperm duct?

A

transfer sperm during ejaculation

86
Q

What is the function of seminal vesicle and prostate gland?

A

secrete fluid containing alkali, proteins and fructose that is added to sperm to make semen

87
Q

What is the function of urethra?

A

transfer semen during ejaculation and urine during urination

88
Q

What is the function of penis?

A

penetrate the vagina fpr ejaculation of semen near the cervix

89
Q

What is the function of ovary?

A

produce eggs, estrogen and progesterone

90
Q

What is the function of oviduct?

A

collect eggs at ovulation, provide a site for fertilisation then move the embryo to the uterus

91
Q

What is the function of oviduct?

A

collect eggs at ovulation, provide a site for fertilisation then move the embryo to the uterus

92
Q

What is the function of uterus?

A

provide for the needs of the embryo and then fetus during pregnancy

93
Q

What is the function of cervix?

A

provide the fetus during pregnancy and then diliate to provide a birth canal

94
Q

What is the function of vagina?

A

stimulate penis to cause ejaculation and provide a birth canal

95
Q

What is the function of vulva?

A

protect internal parts of the female reproductive system

96
Q

When does the mentrual cycle occur in most women?

A

from puberty until the menopause, apart from during pregnancies

97
Q

What are the two purpose of menstrual cycle hormones?

A
  1. Mature an oocyte
  2. Build the endometrium for implantation
98
Q

What is given a chance each time the mentrual cycle occurs?

A

pregnancy

99
Q

What is the first half of the menstrual cycle called?

A

follicular phase because a group of follicles is developing in the ovary

100
Q

What is stimulated to grow in each follicle?

A

an egg

101
Q

What happens at the same time during the follicular phase?

A

the lining of the uterus (endometrium) is repaired and starts to thicken

102
Q

What deterines which follicle releases it egg?

A

The most developed follicle breaks open, releasing its egg into the oviduct. The other folicles degenerate

103
Q

What is the second half of the mentrual cycle?

A

Luteal phase because the wall of the follicle that released an egg becomes a body called the corpus luteum

104
Q

What happens during luteal phase?

A

The wall of the follicle that released an egg becomes a body called the corpus luteum
Continued development of the endometrium prepares it for the implantation of an embryo

105
Q

Why does continued development of the endometrium do?

A

Prepares for the implantation of an embryo

106
Q

What happens if fertilization does not occur in the luteal phase?

A
  • the corpus luteum in the ovary breaks down
  • the thickening of the endometrium in the uterus also breaks down and is shed during menstration
107
Q

What happens if fertilization does not occur in the luteal phase?

A
  • the corpus luteum in the ovary breaks down
  • the thickening of the endometrium in the uterus also breaks down and is shed during menstration
108
Q

Which 4 hormones all help to control the menstrual cycle and how?

A
  • LH, FSH, progesterone, estrogen
  • all help to control the mentrual cycle by both negative and positive feedback
109
Q

What are FSH and LH and what are they produced by?

A

Both are protein hormones produced by the pituitary gland that bind to FSH and LH receptors in the membranes of follicle cells

110
Q

What are estrogen and progesterone and produced by what?

A

They are ovarian hormones released from the ovaries, produced by the wall of the follicle and corpus luteum

111
Q

What do FSH and LH do?

A

FH: stimulate oocyte development
LH: Matures oocyte and causes releases (ovulation)

112
Q

What does estrogen and progesterone do?

A

estrogen: develops endometrium, early: positive feedback on FSH, late: negative feedback on FSH and LH

Progesterone: maintains endometrum, negative feedback on FSH and LH

113
Q

Where is HCG released from and what does it do?

A

Released from placenta
* pregnancy hormone: keeps estrogen and progesterone high

114
Q

What is oxytocin and what does it do?

A

Birth hormone: contractions of uterus and dilates the cervix

115
Q

What are estrogen and progesterone absorbed by and what do they influence?

A

by many cells in the female body
they influence gene expression and therefore development

116
Q

When does FSH rise to a peak?

A

Towards the end of the mentrual cycle

117
Q

What does FSH stimulate?

A
  • the development of follicles, each containing an oocyte and follicular fluid
  • secretion of estrogen by the follicle wall
118
Q

When does estrogen peak?

A

towards the end of the follicular phase

119
Q

What does estrogen stimulate?

A
  • repair and thickening of the endometrium after menstruation
  • stimulate an increase in FSH receptors that make the follicles mroe receptive to FSH, boosting estrogen production (positive feedback)
  • When it reaches high levels, estrogen inhibits the secretion of FSH (negative feedback) and stimulates LH secretion
120
Q

When does LH peak?

A

LH rises to a sudden and sharp peak towards the end of the follicular phase

121
Q

What does LH stimulate?

A
  • the completeion of meiosis in the oocyte and partial digestion of the follicle wall allowing it to burst open at ovulation
  • promotes the development of the wall of the follicle after ovulation into the corpus luteum which secretes estrogen (positive feedback) and progesterone
122
Q

WHen do progesterone levels rise?

A

At the start of the luteal phase, reach a peak and then drop back to a low level by the end of this phase

123
Q

What does progesterone promote?

A
  • the thickening and maintenance of the endometrium
  • Inhibit FSH and LH secretion by the pituitary gland (negative feedback)
124
Q

What does in vivo fertilization mean?

A

The natural method of fertilization, meaning it occurs inside the living tissues of the body

125
Q

What does in vitro fertilization mean?

A

Abbreviated to IVF, is fertilization that happens outside the body in carefully controlled laboratory conditions

126
Q

What is the first stage of IVF?

A

Down-regulation
* The woman takes a drug each day, usually a nasal spray to stop her pituitary gand secreting FSH or LH.
* Secretion of estrogen and progesterone therefore also stops
* This suspends the normal mentrual cycle
* This allows the doctors to control the timing and amount of egg production in the woman’s ovaries

127
Q

What occurs in the superovulation stage of IVF?

A
  • intramuscular injections of FSH and LH are then given daily to stimulate follicles to deveop
  • the FSH injections give a much higher concentration than during a normal mentrual cycle -> far more follicles develop
128
Q

What is done to the follicles when they are 18mm in diameter in the IVF?

A
  • stimulated to mature by an injection of HCG
  • A micropipette mounted on an ultrasound scanner is passed through the uterus wall to wash eggs out of the follicles
  • Each egg is mixed with sperm cells in sterile conditions in a shallow dish
  • incubated at 37C until the next day
129
Q

What is the otder of phases of the mentrual cycle?

A

Day 1-4 Follicular phase
Day 5-14 Ovulatory phase
Day 14-28 Luteal phase

130
Q

What occurs during the follicular phase?

A
  • menstruation. Endometirum shed
  • FSH increases, stimulating folicle development
131
Q

What occurs during the ovulatory phase oft he menstrual cycle?

A
  • FSH and follicle stimulate oestrogen release
  • Oestrogen stimulate endometrium development
  • oestrogen stimulates LH
  • Peak in LH causes ovulation
132
Q

What occurs in the luteal phase of the menstrual cycle?

A
  • Fall in LH. Corpus luteum forms from now-empty follicle
  • Corpus luteum releases progesterone
  • progesterone maintains the endometrium and inhibits FSH and LH
133
Q

What happens in the mentrual cycle when n o fertilisation and implantation occurs?

A

Progesterone and oestrogen drop, triggering menstruation. andFSH release`

134
Q

Negative and positive feedback mechanisms involving ovarian and pituitary hormones

A

Biology (57 decks)

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