18.6 hypothalamus & pituitary gland Flashcards
(98 cards)
1
Q
What is the endocrine gland that secretes several hormones that control other endocrine glands? (the “master”)
A
pituitary gland (also known as hypophysis)
2
Q
What is the pituitary gland’s master?
A
the hypothalumus
3
Q
Cells in the hypothalamus synthesize at least how many hormones? How many in the pituitary gland?
A
Hypothalamus - 9
Pituitary gland - 7
4
Q
Where is the pituitary gland located?
A
in the hypophyseal fossa of the sella trice of the sphenoid bone
5
Q
How does the pituitary gland attach to the hypothalamus?
A
by a stalk, the infundibulum
6
Q
The infundibulum has 2 anatomically separate portions which are?
A
anterior pituitary (also called anenohyphosis) & posterior pituitary (also called neurohypophysis)
7
Q
Wheich portion of the pituitary gland accounts for 75% of the total weight of the gland? (anterior or posterior)
A
Anterior
8
Q
What kind of tissue is the anterior pituitary composed of?
A
epithelial tissue
9
Q
What are the 2 parts of the anterior pituitary ?
A
pars distils - larger portion
pars tubercles - from sheath around the infundibulum
10
Q
What tissue is the posterior pituitary composed of?
A
neural tissue
11
Q
What are the 2 parts of the posterior pituitary ?
A
pars nervosa - larger bulbar portion
Infundibulum
12
Q
The 3rd region of the pituitary gland is called the pars intermedia which is what?
A
atrophies during fetal development & ceases to exist as a separate lobe in adults, however some of its cells migrate to adjacent parts of the anterior pituitary where they persist
13
Q
What are the 5 types of anterior pituitary cells?
A
- somatotrophs
- thyrotrrophs
- gonadotrophs
- lactotrophs
- corticotrophins
14
Q
How many hormones to the 5 anterior pituitary glands secrete?
A
7
15
Q
Somatotrophs secrete what hormone?
A
growth hormone (GH)
(also known as smatotopin)
16
Q
What does the growth hormone stimulate in the body?
A
general body growth & regulate aspects of metabolism
17
Q
What hormone does thyrotrophs secrete?
A
thyroid-stimulating hormone (TSH) (also known as thryotropin)
18
Q
What does TSH control in the body?
A
controls the secretions & other activities of the thyroid gland
19
Q
What hormones do gonadotrophs secrete? (2)
A
Gonadotropins:
1. follicle-stimulating hormone (FSH)
2. Luteinizing hormone (LH)
20
Q
What do the FSH & LH hormones act on in the body?
A
FSH & LH act on the gonads (testes & ovaries)
produce sperm and secrete testosterone in men and stimulate the ovaries to mature oocytes and secrete estrogen and progesterone
21
Q
the lactotrophs secrete what hormone?
A
prolactin (PRL)
22
Q
What does prolactin (PRL) initiate?
A
milk production in the mammary glands
23
Q
What hormones do the coricotrophs secrete? (2)
A
- Adrenocorticotropic hormone (ACTH)
- Melanocytestimulating hormone (MSH) -> remnants of the pars intermedia
24
Q
What does the adrenocorticotropic hormone (ACTH) stimulate to secrete glucocorticoids such as cortisol?
A
the adrenal cortex
25
hypothalamus releases hormones which stimulates secretion of anterior pituitary hormones. What are the 5 hormones related by the hypothalamus?
1. Growth hormone-releasing hormone (GHRH)
2.Thyrotropin-releasing hormone (TRH)
3. corticotropin-relaying hormone (CRH)
4. Prolactin releasing hormone (PRH)
5. Gonadotropin releasing hormone (GnRH)
26
Growth hormone-releasing hormone (GHRH) also known as somatocrinin stimulates secretion of what hormone?
growth hormone
27
Thyrotropin-releasing hormone (TRH) stimulates secretion of what hormone?
thyroid-stimulating hormone
28
Corticotropin-Relaying hormone (CRH) stimulates secretion of what hormone?
adrenocorticotropic hormone
29
Prolactin-relasing hormone (PRH) stimulates secretion of what hormone?
prolactin
30
Gonadotropin-relasing hormone stimulates secretion of which hormones?
FSH and LH
31
How do hypothalamic hormones that release or inhibit anterior pituitary hormones reach the anterior pituitary?
through a portal system
32
Hypothalamus produces 2 inhibiting hormones? What do these do and what are the 2?
suppress secretion of anterior pituitary hormones
1.growth hormone inhibiting hormone (GHIH)
2.Prolactin-inhibiting hormone (PIH)
33
In the hypophyseal portal system how does blood flow?
From capillaries in hypothalamus --> portal veins that carry blood to capillaries of the anterior pituitary
34
How is blood brought into the hypothalamus?
the superior hypophyseal arteries (branches of the internal carotid arteries)
35
At the junction of the median eminence of the hypothalamus & the infundibulum, the arteries divide into a capillary network called what?
primary plexus of the hypophyseal portal system
36
From the primary plexus, blood drains into the hypophyseal portal veins which pass down where?
outside the infundibulum
37
In the anterior pituitary the hypophyseal portal veins divide again and form another capillary network called what?
secondary plexus of the hypophyseal portal system.
38
Hypophyseal veins drain blood from where? so that the hormones can travel to target tissues in the body
anterior pituitary
39
The anterior pituitary hormones that act on other endocrine glands are called what?
tropic hormones (or tropins)
40
release of anterior pituitary hormones is regulated by hypothalamus & _____ _______
negative feedback
41
The secretory activity of what 3 types of anterior pituitary cells decreases when blood levels of their target gland hormones rise?
thyrotrophs, corticotrophins and gonadotrophs
42
adrenocorticotropic hormone (ACTH) stimulates the cortex of the adrenal gland to secrete glucocorticoids, mainly cortisol, in turn the elevated blood level of cortisol does what
decreases secretion of both ACTH and CRH by suppressing the activity of the anterior pituitary corticotrophins & hypothalamic neurosecretory cells
43
What are the most numerous cells in the anterior pituitary?
somatotrophs --> which secrete growth hormone = most plentiful anterior pituitary hormone
44
What does growth hormone promote in the body?
growth of bones & skeletal muscles and regulates certain aspects of metabolism
45
How does GH exert its growth promoting effects indirectly?
through small protein hormones called insulin-like growth factors (IGFs) or somatomedins
46
In response to the growth hormone cells in which parts of the body secrete IGFs? (4)
-Liver
-Skeletal muscle
-Cartilage
-Bone
47
IGFs synthesized in the liver enter the bloodstream as what?
hormones that circulate to target cells throughout the body to cause growth
48
IGFs produced in skeletal muscle, cartilage & bone act as what?
autocrines or pancrines to cause growth of those tissues
49
effects of GH indirect & direct?
indirect- body growth
direct- metabolism
50
functions of IGFs and GH ? (3)
increase growth of bones & soft tissues
enhance lipolysis
decrease glucose uptake
51
How do IGFs cause growth of bones?
in bones IGFs stimulate osteoblasts, promote cell devision at epiphyseal plate & enhance synthesis of proteins needed to build more bone matrix
52
How do IGFs help to grow soft tissues such as skeletal muscle, kidneys and intestines?
IGFs cause cells to grow by increasing uptake of amino acids into cells & accelerating protein synthesis
Also decrease breakdown of proteins & use amino acids for ATP production
53
Due to effects of GH (acting with IGFs as mediators) what happens in childhood & teenage years?
increases growth of skeleton and soft tissues
54
Due to effects of GH (acting with IGFs as mediators) what happens in adults?
helps maintain mass of bones & soft tissues & promotes healing of injuries and tissue repair
55
what results from GH enhance lipolysis in adipose tissue?
increased use of the released fatty acids for ATP production by body cells
56
GH influences carbohydrate metabolism by?
decreasing glucose uptake --> which decreases the use of glucose for ATP production in most body cells
57
The action of decreasing glucose uptake spares glucose for what?
so that its available to neutrons for ATP production in times of glucose scarcity
58
GH stimulates liver cells to release what into the blood
glucose
59
somatotrophs release bursts of growth hormone how often?
every few hours (especially in sleep)
60
secretory activity of somatotrophs is controlled by which 2 hypothalamic hormones?
1. growth hormone-releasing hormone (GHRH)
2. growth hormone-inhibiting hormone (GHIH)
61
Which factors would promote GHRH secretion from the hypothalamus?
-hypoglycemia
-decreased blood levels of fatty acids
-increased blood levels of amino acids
deep sleep
-increased activity of the sympathetic nervous system (stress or vigorous exercise)
-other hormones (testosterone, estrogens, thyroid hormones & gherkin)
62
Which factors would promote GHIH secretion
-hyperglycemia
-increased blood levels of fatty acids
-decreased blood levels of amino acids
-obesity
-aging
-high levels of GH and IGFs
63
Which is an example of negative feedback inhabitation? GHIH or GHRH?
GHRH - because the GH will be able to secrete IGFs
64
After being secreted due to factors that would secrete GHIH , GHIH enters the hypophyseal portal system & flows into the anterior pituitary,, what happens after that?
it prevents the somatotrophs from secreting GH by interfering with the singling pathway used by GHRH
65
Release of TRH (thyroid releasing hormone depends on blood levels of T3 & T4. High levels of thyroid hormones (T3 & T4) inhibit secretion of TRH via what feedback?
negative -> there is no inhibiting hormone
66
prolactin works with other hormones & initiates and maintains milk production by mammary glands. By itself it has a ___ effect
weak
67
ejection of milk from the mammary glands depends on the hormone ______
oxytocin
68
Milk production and ejection consitute ?
lactation
69
breast tenderness just before menstruation may be caused by elevated ______
prolactin
70
in females what hormone inhibits the release of prolactin from the anterior pituitary ?
prolactin inhibiting hormone (PIH) which is dopamine
71
just before menstruation begins what happens to the secretion and blood level of prolactin
secretion - diminishes
blood level - rises
(but not enough to stimulate milk production)
72
As the menstrual cycle begins what happens to Prolactin levels
PIH is again secreted and prolactin level drops
73
during pregnancy what happens to the prolactin level
prolactin level rises stimulated by prolactin-releasing hormone (PRH) from the hypothalamus
74
sucking of a nursing infant causes a ____ in hypothalamic secretion of PIH?
reduction
75
hyper secretion of prolactin in mails causes what?
erectile dysfunction
76
hyper secretion of prolactin in females causes what?
galactorrhea (inappropriate lactation)
amenorrhea (absence of menstrual cycles)
77
What is the role of the posterior pituitary?
does not synthesize hormones
it stores and releases 2 hormones
78
What does the posterior pituitary consist of
axons and axon terminals of more than 10,000 hypothalamic nerurosecretory cells
79
The cell bodies of the hypothalamic neurosecretory cells are in which nuclei of the hypothalamus?
paraventricular & supraoptic nuclei
80
the axons of the neurosecretory cells from which tract?
the hypothalamichypophyseal tract
81
Where does the hypothalamichypophyseal tract begin and end
begins in the hypothalamus & ends near blood capillaries in the posterior pituitary
82
The neuronal cell bodies of both paraventricular and supraoptic nuclei synthesize with which 2 hormones?
oxytocin (OT) and antidiuretic hormone (ADH)
83
the axon terminals in the posterior pituitary are associated with specialized neuroglia called?
pituicytes
84
Blood is supplied to the posterior pituitary by
inferior hypophyseal arteries (which branch from internal coroitid arteries
85
the inferior hypophyseal arteries drain into a capillary network called what? that receives secreted oxytocin and antidiuretic hormones called
capillary plexus of the infundibular process
86
From the plexus hormones pass into where for distribution to target cells in other tissues
they pass into the hypophyseal veins
87
antidiuretic
substance that decreases urine production
88
ADH decreases urine volumes by?
returning more water to the blood
89
in absence of ADH urine output would
increase more than a tenfold from the normal 1-2L per day to about 20L per day
90
why does drinking alcohol often cause frequent urination
because alcohol inhibits the secretion of ADH
91
ADH also decreases the water lost through sweated and causes contraction of arterioles --> this does what to BP
increases BP (other name for ADH is vasopressin)
92
what 2 major stimuli promote ADH secretion?
1. rise in blood osmolarity
2. decrease in blood volume
93
high blood osmolarity is detected by what neurons in the hypothalamus ?
osmoreceptors (monitor changes in blood osmolarity)
94
decreased blood volume is detected by volume receptors in ?
in the atria of the heart and by baroreceptors in the walls of certain blood vessels
95
blood carries ADH to which 2 target tissues?
the kidneys and smooth muscle in blood vessel walls
96
how do the kidneys respond to ADH?
retain more water --> decreases urine output
97
How do the smooth muscle in the walls of arterioles (small arteries) respond to high levels of ADH?
they contract which constrict (narrows) the lumen of these blood vessels --> increase BP
98
