9.1/9.2/9.3/9.4 Flashcards
1
Q
Endocrine System
A
System that works in parallel with the nervous system to maintain homeostasis by releasing chemical hormones from various glands.
2
Q
Endocrine Gland
A
Ductless gland that secretes hormones directly into the bloodstream.
action of hormone can happen far from the endocrine gland secreting the hormone
3
Q
Hormone
A
Chemical messengers sent to many parts of the body to produce a specific effect on a target cell or organ.
4
Q
What are hormones responsible for controlling?
A
- Growth and Development
- Metabolism
- Regulation of Internal
Environment - Reproduction
5
Q
Glands that Function Exclusively as Endocrine Glands
A
- pituitary
- pineal
- thyroid
- parathyroid
- adrenal glands
6
Q
Tissues and Organs that Secrete Hormones
A
- hypothalamus
- thymus
- pancreas
- testes and ovaries
7
Q
Target Cells
A
Cells whose activity is affected by a particular hormone.
8
Q
How do hormones affect their target cells?
A
Each target cell contains receptor proteins which the hormone can bind to and it triggers other reactions in the target cell.
9
Q
Exocrine Gland
A
- release their secretions through ducts or tubes
eg. sweat glands, salivary glands, tear glands
10
Q
Steroid Hormones
A
- lipid-based hormones made from cholesterol that can diffuse through the lipid bilayer of cell membranes
- hydrophobic*
11
Q
Examples of Steroid Hormones
A
Testosterone, Estrogen, Cortisol
12
Q
What happens when steroid hormones enter a target cell?
A
- They bind to receptor proteins which activates specific genes, causing changes in the cell.
- Hormone/receptor complex acts as a transcription factor turning target genes on or off.
13
Q
Water-Soluble Hormones
A
-hormones that cannot diffuse across the cell membrane
14
Q
How does a water-soluble hormone interact with the target cell?
A
- it will bind to a receptor protein on the surface of the target cell
- this starts a cascade of reactions inside the target cell which amplifies the impact of a hormone
15
Q
Examples of Water-Soluble Hormones
A
Epinephrine, Human Growth Hormone (hGH), thyroxine, insulin
16
Q
Protein Hormones
A
-hydrophilic, large hormone molecules that bind to receptors (transmembrane proteins) on the surface of “target” cells
17
Q
How does a protein hormone interact with the target cell?
A
- binding of the hormone to its receptor initiates a sequence of intracellular signals that alter the behaviour of the cell or stimulate gene expression in the nucleus
- cell begins to produce the appropriate gene products in response to the hormonal signal
18
Q
Examples of Protein Hormones
A
Insulin, glucagon, oxytocin, antidiuretic hormone
19
Q
How is hormone production regulated?
A
- hormone production increases or decreases in response to changing metabolic needs of the body
- regulated by nervous and endocrine system
20
Q
The impacts of a specific hormones on the activity of target tissues is a function of what?
A
A) the rate of hormone production and secretion
B) hormone concentration in the blood
C) rate of blood flow to target organ or tissue
D) half life of hormone
21
Q
Pituitary Gland
A
- “master gland”
- controls all other endocrine glands
- small sac at base of brain connected to hypothalamus
- produces and stored hormones
22
Q
Hypothalamus
A
-controls release of hormones by the pituitary gland through the use of hormone releasing and inhibiting hormones
23
Q
Releasing Hormones
A
- hormones that stimulate the pituitary gland to secrete hormones that act on other endocrine glands
- secreted by hypothalamus*
24
Q
Tropic Hormone
A
-hormone that targets endocrine glands and stimulates them to release other hormones
25
Process of Hormone Secretion
1) Hypothalamus secretes a releasing hormone into anterior pituitary.
2) Anterior pituitary releases a second tropic hormone into bloodstream.
3) Second tropic hormone stimulates target gland to release third hormone into the blood.
26
How is the process of hormone secretion regulated?
Negative Feedback Loop
27
How does negative feedback in hormones work?
-the third hormone secreted prevents further release of the first two hormones in the pathway
28
How do the functions of the nervous and endocrine systems overlap?
- some nervous system structures, such as cells in the hypothalamus, secrete hormones
- several chemicals function as both neurotransmitters and hormones
- both regulated by feedback loops
29
Functions of the Pituitary Gland
-releases six main hormones involved in body's metabolism, growth, development and other critical life functions
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Two Lobes of Pituitary
Anterior and Posterior
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Posterior Pituitary
-stores and releases antidiuretic hormone (ADH) and oxytocin, which are produced in the hypothalamus and transferred to posterior pituitary
32
Anterior Pituitary
-synthesizes and secretes six major hormones
33
Six Major Hormones Secreted By Anterior Pituitary
- human growth hormone (hGH)
- prolactin (PRL)
- thyroid stimulating hormone (TSH)
- adrenocorticotropic hormone (ACTH)
- follicle-stimulating hormone (FSH)
- luteinizing hormone (LH)
34
Human Growth Hormone (hGH)
-hormone that ultimately affects almost every body tissue, by direct stimulation or via tropic effects
35
What does the hGH do?
-stimulates the liver to secrete hormones called growth factors, which along with hGH, influence many physiological process
36
What physiological processes do hGH and growth factors increase?
- protein synthesis
- cell division and growth (cartilage, bone, muscle)
- metabolic breakdown and release of fats stored in adipose (fat) tissue
37
What parts of the body does hGH stimulate the growth of?
- muscles
- connective tissue
- growth plates
38
What happens when you have too much hGH?
Gigantism
39
What happens when you have too little hGH?
Dwarfism
40
Acromegaly
-excessive production of hGH in adulthood which causes bones and soft tissues to widen along with other symptoms
41
Thyroid Gland
-butterfly-shaped gland located below the larynx in the neck
42
Function of the Thyroid
-produces the hormone thyroxine which helps regulate metabolism and growth
43
Thyroxine (T4)
-hormone produced by the thyroid and released into the bloodstream
44
Function of Thyroxine
-increases the rate at which the body metabolizes fat, proteins and carbs for energy
45
What does thyroxine stimulate?
-cells of the heart, skeletal muscles, liver and kidneys to increase cellular respiration
46
Cretinism
-when the thyroid fails to develop properly during childhood
47
Hypothyroidism
-condition resulting when the thyroid produces extremely low levels of thyroxine
48
Hyperthyroidism
-condition resulting when the thyroid produces extremely high levels of thyroxine
49
Grave's Disease
-severe state of hyperthyroidism that results when immune system attacks thyroid
50
Negative Feedback Loop of Thyroxine Secretion
- anterior pituitary releases thyroid-stimulating hormone which causes thyroid to secrete thyroxine
- thyroxine enters blood
- high levels of thyroxine cause thyroxine itself to feed back to the hypothalamus and anterior pituitary to suppress secretion
51
Thyroid-Stimulating Hormone
-hormone released by the anterior pituitary which causes the thyroid gland to secrete thyroxine
52
What does the thyroid require for thyroxine production?
Iodine
53
Goitre
- an enlargement of the thyroid gland characterized by a large swelling in the throat
- associated with a deficiency of iodine
54
What is calcium essential for?
- healthy teeth and skeletal muscles
| - blood clotting, nerve conduction, and muscle contractions
55
Calcitonin
-hormone that regulates levels of calcium in the blood
56
What happens with excess calcium in blood?
-Calcitonin stimulates uptake of calcium into bones
57
Parathyroid Glands
-4 small glands attached to thyroid that produce parathyroid hormone (PTH)
58
When does the body synthesize and release PTH?
-when calcium levels in the blood fall
59
What does PTH do?
- stimulates bone cells to break down bone material (calcium phosphate) and secrete calcium into the blood
- stimulates kidneys to reabsorb calcium from the urine activating vitamin D in the process which stimulates the absorption of calcium from food in the intestine
60
Adrenal Glands
-one of a pair of organs located on top of the kidneys which are composed of two layers (each produces different hormones and functions as an independent organ)
61
Two Layers of the Adrenal Glands
Adrenal Medulla (inner) and Adrenal Cortex (outer)
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Adrenal Medulla
- the inner layer of the adrenal glands that produces epinephrine and norepinephrine, hormones that regulate the short-tern stress response
- regulated by nervous system
- can be removed without an effect
63
Epinephrine
-hormone produced by the adrenal cortex that helps regulate the short-term stress response; also known as adrenaline
64
Short-Term Stress Response
-the body's acute reaction to stress in which the sympathetic nervous system is stimulated
65
How does the adrenal gland respond in response to a stressor?
- neurons of the sympathetic nervous system carry a signal from the hypothalamus directly to the adrenal medulla
- neurons stimulate the adrenal medulla to secrete epinephrine and small amounts of norepinephrine
66
Body's Response to Epi and Norepi
- triggers an increase in breathing rate, heart rate, blood pressure, blood flow to the heart and muscles, and the conversion of glycogen to glucose in the liver
- pupils of the eyes dilate, blood flow to the extremities decreases
67
Why is the release of epi and norepi rapid?
Under nervous system control.
68
Adrenal Cortex
- produces glucocorticoids and mineralocorticoids, hormones that regulate the long-tern stress response
- secretes small amounts of gonadocorticoids (female and male sex hormones)
69
Long-Term Stress Response
-sustained psychological response to stressors, characterized by increases in blood glucose and blood pressure and decrease in inflammatory response
70
Glucocorticoids
Increase blood sugar level
71
Mineralocorticoids
Increase blood pressure
72
Gonadocorticoids
Supplement the hormones produced by the gonads.
73
Most Abundant Glucocorticoid
Cortisol
74
Cortisol
- released by the adrenal cortex in a long-term stress response
- triggers an increase in blood glucose levels and reduces inflammation
75
Process of Cortisol Secretion
- brain detects danger
- hypothalamus secretes releasing hormone
- releasing hormone stimulates anterior pituitary to secrete adrenocorticotropic hormone (ACTH)
- ACTH targets adrenal cortex causing release of cortisol
76
Adrenocorticotropic Hormone (ACTH)
-hormone synthesized by the anterior pituitary gland to target the adrenal cortex and regulate the production of glucocorticoids
77
Functions of Cortisol
- raises blood glucose levels by breakdown of muscle protein into amino acids
- breakdown of fat cells to release glucose
78
What do high-levels of cortisol cause?
- impair thinking
- damage the heart
- cause high blood pressure
- lead to diabetes
- increase susceptibility to infection
- cause an early death
79
Main Mineralocorticoid
Aldosterone
80
Aldosterone
-type of mineralocorticoid hormone secreted by the adrenal cortex
81
Function of Aldosterone
-stimulates the kidneys to increase the absorption of sodium in the blood which increases the concentration of solutes in the blood, which draws in more water from the kidneys, raising blood pressure
82
Addison's Disease
- disease caused when adrenal cortex is damaged
- body secretes inadequate amounts of mineralocorticoids and glucocorticoids
- symptoms: hypoglycaemia (low blood sugar), sodium and potassium imbalances, rapid weight loss
83
Pancreas
-small gland in the abdomen that secretes digestive enzymes and secretes the hormone insulin
84
Islets of Langerhans
-clusters of endocrine cells found throughout the pancreas, consisting of glucagon-producing alpha cells and insulin-producing beta cells
85
beta cells
-cells of the pancreas that secrete insulin to decrease the level of blood glucose
86
alpha cells
-cells of the pancreas that secrete glucagon to increase the level of blood glucose
87
insulin
-a hormone secreted by the beta cells in pancreas to make target cells more permeable to glucose
88
glucagon
-hormone produces by alpha cells in pancreas to stimulate liver to convert glycogen back into glucose
89
How are insulin and glucagon levels regulated?
- negative feedback
- high blood glucose, insulin is produced
- low blood glucose, glucagon is produced
90
Diabetes Mellitus
- a serious chronic condition that results when the pancreas does not make enough insulin or the body does not respond properly to insulin
- causes hyperglycaemia
91
Hyperglycaemia
- condition resulting from high levels of blood glucose
| - occurs in individuals with diabetes mellitus
92
Type 1 Diabetes
- immune system produces antibodies that attack and destroy the beta cells of the pancreas, therefore unable to produce insulin
- require daily insulin injections in order to live
93
Type 2 Diabetes
- develops gradually, often because the insulin receptors on the body’s cells stop responding to insulin OR beta cells produce less and less insulin over time
- more common in overweight people
- can be controlled with diet, exercise and oral medications
- becoming an epidemic in some parts of the world
94
Gonads
- organ that produces reproductive cells (gametes)
| - produces sperm in males and eggs in females
95
Sex Hormone
-one of several chemical compounds that control the development and function of the reproductive or secondary sex characteristics
96
Testes
- two male gonads
| - held outside of body in scrotum
97
What are the testes composed of?
- long coiled tubes (seminiferous tubules)
| - hormone-secreting cells (interstitial cells)
98
Interstitial Cells
-secrete testosterone
99
Seminiferous Tubules
-where sperm is produced
100
Epididymis
-where sperm go from the testes to mature and become motile
101
Ductus Deferens
-storage duct that connects to the epididymis which then leads to the penis via the ejaculatory duct
102
Penis
-transfers sperm from the male to the female reproductive tract
103
Foreskin
-sheath of skin that surrounds and protects the tip called the glans penis
104
Seminal Fluid (semen)
-fluid from a series of glands mixed with sperm
105
What happens with semen during sexual arousal?
-semen enters urethra from ductus deferentia and it is carried through the penis before it is ejaculated
106
What does the Y chromosome carry?
-a gene called the testis-determining factor (TDF) whose action triggers production of male sex hormones
107
Androgens
-male sex hormones that initiate the development of male sex organs and ducts in the fetus
108
Puberty
- the period in which the reproductive system completes its development and become fully functional
- happens due to hormonal events
109
Age of Puberty for Males
10-13 Years
110
GONADOTROPIC-RELEASING HORMONE (GnRH)
-hormone that acts on the anterior pituitary gland to cause it to release two different sex hormones; luteinizing hormone (LH) and follicle-stimulating hormone (FSH)
111
FOLLICLE-STIMULATING HORMONE (FSH)
- reproductive hormone that stimulates the development of the sex organs and gamete production in males and females
112
LUTEINIZING HORMONE (LH)
-reproductive hormone that triggers ovulation, stimulates the formation of the corpus luteum, stimulates estrogen production in the ovaries and testosterone in the testes
113
Testosterone
-reproductive hormone that stimulates the development of the male reproductive tract and secondary sex characteristics; only minor effects in females
114
How is sperm production controlled?
Hormone Feedback Mechanisms
115
Hormone Feedback Pathway for Sperm Production
- GnRH from the hypothalamus triggers the release of FSH and LH from the anterior pituitary
- FSH causes the seminiferous tubules to produce sperm
- at the same time, FSH causes cells in the seminiferous tubules to release inhibin (acts on the anterior pituitary to inhibit production of FSH)
- as FSH levels drop, testes release less inhibin
116
Inhibin
-acts on anterior pituitary to inhibit the production of FSH; produces a negative feedback loop that controls the rate of sperm formation
117
What is the hormonal mechanism for testosterone production?
-LH causes the interstitial cells in the testes to release testosterone
118
Andropause
-in men, a gradual decline in testosterone level beginning around age 40; symptoms include fatigue, depression, loss of muscle/bone mass, drop in sperm production
119
Female Gonads
-ovaries (produce limited number of gametes or ova)
120
Ovaries
- site of oogenesis (ova production)
| - two ovaries alternate so that only one produces an egg each month
121
Follicles
- specialized cell structures in the ovary
- a single ovum develops within each follicle and each month a single follicle matures and then ruptures releasing the ovum into the oviduct (ovulation)
122
Fimbriae
-thread-like projections that sweep over the ovary and sweep up an ovum when it is released, moving it to the oviduct
123
Oviduct
-carries the ovum from the ovary to the uterus
124
Uterus
-muscular organ that holds and nourishes a developing fetus
125
Endometrium
-lining of the uterus that is richly supplied with blood vessels to provide nutrients for the fetus
126
Upper and Lower Ends of the Uterus
- upper end connects to oviducts
| - lower end forms a narrow opening called the cervix which connects to the vagina
127
Vagina
- entrance for penis to deposit sperm
| - exit for fetus
128
Age of Puberty for Females
9-13 Years
129
When does a girl begin puberty?
-when the hypothalamus increases the production of GnRH which acts on the anterior pituitary to release LH and FSH
130
What do LH and FSH do in females?
-act on the ovaries to produce female sex hormones estrogen and progesterone which launch the reproductive cycle
131
Estrogen
- female sex hormone produced in the ovary
| - help maintain sexual organs and secondary sexual characteristics
132
Progesterone
-female sex hormone produced first by the corpus luteum of the ovary to prepare the uterus for the fertilized egg, and later by the placenta to maintain pregnancy
133
Menstrual Cycle
- in a female, period of 20-45 days during which hormones stimulate the development of the uterine lining, and an egg (ovum) is developed and released from an ovary; if the egg is not fertilized, the uterine lining is shed as the cycle begins again
- divided into the ovarian and uterine cycle
134
Typical Length of Menstrual Cycle
28 Days
135
Location of Ovarian Cycle
Ovaries (ironically!)
136
Location of Uterine Cycle
Uterus (ironically!)
137
Follicles
-structures in the ovary that contain the egg and secrete estrogen
138
How many follicles mature during reproductive years?
400
139
What happens in a single ovarian cycle?
-one follicle matures, releases an ovum, and then develops into a yellowish, gland like structure known as the corpus luteum which later degenerates
140
First Stage of the Ovarian Cycle
Follicular Stage
141
Steps of the Follicular Stage
- increase in FSH released by anterior pituitary which stimulates one follicle to mature
- as the follicle matures, it releases estrogen and some progesterone
- increased estrogen in blood acts on anterior pituitary to inhibit FSH release and trigger sudden release of GnRH from hypothalamus
- leads to increase in LH production triggering ovulation when the follicle bursts releasing the ovum
142
Second Stage of Ovarian Cycle
Luteal Stage
143
Steps of the Luteal Stage
- once the ovum is released, LH causes the follicle to develop into a corpus luteum
- corpus luteum secretes progesterone and some estrogen
- as hormone levels in blood rise they act on the anterior pituitary to inhibit FSH and LH production
- corpus luteum degenerates leading to a decrease in levels of estrogen and progesterone
144
What happens if the ovum is fertilized and implants in the endometrium?
- blood hormone levels of est and pro remain high under stimulus of hormones released by embryo-supporting membranes
- presence of pro maintains endometrium to support fetus
- presence of est stops ovarian cycle so no additional follicles mature
145
Events of the Uterine Cycle
- build-up of blood vessels and tissues in the endometrium
| - if fertilization does not occur, the endometrium disintegrates and menstruation begins
146
When does the uterine cycle begin?
-on the first day of menstruation (first day of ovarian cycle)
147
First Five Days of the Uterine Cycle
-menstruation occurs and ends with a thin endometrium from being shed
148
Sixth Day of Uterine Cycle
-estrogen level is high enough to cause thickening of endometrium
149
After Ovulation and the Uterine Cycle
-release of progesterone by corpus luteum causes more rapid thickening of endometrium
150
Day 15 to 23 of the Cycle
-thickness of endometrium may double or triple in size
151
Phases of the Menstrual Cycle
1) Flow Phase-shedding of the endometrium (Day 1-5)
2) Follicular Stage-development of follicles within ovary with estrogen secretion (Day 6-13)
3) Ovulatory Phase-egg bursts from ovary and follicular cells differentiate into corpus luteum (Day 14)
4) Luteal Phase-characterized by the formation of corpus luteum (Day 15-28)
152
What happens when there is no fertilization?
- decrease in estrogen and progesterone due to degeneration of corpus luteum
- weak contractions and endometrium is shed
153
What happens when fertilization occurs?
- corpus luteum does not degenerate
- estrogen and progesterone are sustained
- no ovulation, endometrium is maintained
154
The Effect of Age on the Menstrual Cycle
-number of functioning follicles in female reproductive system decreases with age resulting in gradual decline in the amount of estrogen and progesterone in the blood
155
Menopause
-period in a woman's life during which a decrease in estrogen and progesterone results in an end of menstrual cycles, occurring at age 50
156
Hormone Replacement Therapy
-administration of low levels of estrogen and/or progesterone to alleviate symptoms of menopause in females
