Lecture 9 &10

Question 1

What does the hypothalamus link with ?

Answer 1

links endocrine system and nervous system through its control of the pituatry gland (hypophesis)

Question 3

When responding to various stimuli/signals what can the hypothalamus do ?

Answer 3

-Synthesise and releease neurohormones into circulation via posterior pituatry
-Synthesise and release hypophysiotropic hormones into the hypophyseal portal blood system to regulate hormone release from anterior pituatry
-send neural signals to regulate the release of sympathetic nervous system hormones from the adrenal medulla

2 major control of secretion-neural control of neurosecretory cells(post

Question 4

What is the relationship between the hypothalamus and the pituatry gland ?

Answer 4

-Direct neural connection between hypothalamus & posterior pituatry gland
-Hormonal function between the hypothalamus & anterior pituatry via a dedicated portal vascular system (hypophyseal)

Question 5

The embryonic development of the pituatry gland ?

Answer 5

pituatry gland -2 glands with 2 diff embryonic origins
-outgrowth of tissues appear from floor of brain and roof of mouth (Rathke’s pouch)
-neural ectoderm forms the neurohyphsis
-oral ectoderm forms adenohypophysis

Question 6

What are the Pituatry glands 2 distinct lobe ?

Answer 6

-Adenopophsis (Anterior lobe)
-Neurohypophysis (Posterior lobe)

Question 7

Properties of Adenohypophesis ?

Answer 7

-aka anterior lobe
-derived from pharyngeal ectoderm
consists of 2
1. Anterior pituatry
2. Pars tuberalis: forms pituatry stalk

accounts for 80% pituatry weight

Question 8

Properties of Neurohypophysis ?

Answer 8

aka posterior lobe
derived from neural ectoderm
consists of 3 portions
1. Posterior pituatry
2. Medium eminence
3. Infundiblar stem/stalk

Question 9

Histology ????

Question 10

What are the functions of the hypothalamus ?

Answer 10

controls fundamental physiological activities inclusing:
-body temp
-hunger
-thirst
-sleep

Hypothalamus and pituatry is interface between endocrine and NS
recievs

Hyp…. interacts with both lobes of pituatry gland but in different ways

Question 11

What are the differences between anterior and posterior pituatry ?

Answer 11

?????

Question 12

What & where 2 neurohormones does the hypothalamus secrete ?

Answer 12

via posterior pituatry
oxytocin & antidiuretic (ADH)
synthesised in hypo in magnocellular neurons
transported in vesicles along axons of these neurons through ME into posterior pituatry* via infundiblum
stored in secratory granules

*consists of bundles & terminations of axons originating from the hypoth

Question 13

What else does the transport of hormones from hypothalamus to the pituatry require ?

Answer 13

requires association with transport protein :neurophysins
-stimulation of these hypothalmic neurosecretory cells causes AP to propagte –>release of hormones directly into capillary blood network via EXOCYTOSIS (Ca2+depenedent)
-Oxytocin & ADH are nonapeptide ( 2 AA diff) which travel as free hormones on general circulation with half time -1 min

Question 14

What are the functions of ADH ?

Answer 14

released in response to an increase in plasma osmotic pressure (osmolality) or a fall in blood volume
-Has Antidiuretic actions stimulate reabsorption of water from renal collecting ducts (cAMP dependent )
-urinary volume is decreased and urine osmolality is increased
-potent vasoconstricto

Question 15

What are the functions of oxytocin ?

Answer 15

stimulates milk ejection response to suckling-let down
-causes contraction of mammary gland myoepthelial cells to squeeze milk towards nipple
-stimuli can cause secretion’baby cry’etc
-Uterine contractions
helps expel fetus and placenta (labour)
POSITIVE FEEDBACK

establishes maternal nehaviour

Question 16

An example of positive feedback ?

Answer 16

Oxytocin secreted during childbirth
-increased excitability of uterus
-uterine contraction
-fetus presses on cervix
-afferent signal to hypothalamus
-oxytocin secretion by posterior pituatry–>
-birth of baby terminates positive feedback

Question 17

What role does oxytocin play in men ?

Answer 17

1. in sperm progression
2. erection
3. ejaculation

Question 18

What is the nuclei of hypothalamus involved in ?

Answer 18

Hormone synthesis and excretion
1. Cortotropin-releasing hormone(paraventricular nucleus)
2. Thyrotropin-releasing hormone(PVN
3. Gonadotropin-releasing hormone POA & arcuate nucleus (AR)

Parvocellular neurons in these nuclei may release 1 or more hypophysiotr

Question 19

What are the 5 principle endocrine cells ?

In the Anterior pituatry

Answer 19

1. Somatrophs-50% secrete growth hormones aka somatropin
2. Lactotrophs-15-20%:secrete prolactin (PRL)
3. Gonadotrophs-10% secrete FSH,LH
4. Corticotrophs:15-20% secrete ACTH & related peptides,melanoctye stimulating hormone.
5. Thyrotroph-5% secrete TSH

Question 20

What are the anterior pituatry hormone targets ?

Answer 20

1. TSH –>metabolism & growth
2. ACTH–>stress response ,metabolic actions
3. MSH in animals– skin darkening in amphibians,reptiles and fish
4. Prolactin-growth during pregenancy,many functions including reproduction,water&ion balance
5. Growth hormone-

Question 21

What are the functions of growth hormone ?

Answer 21

Acts on a variety of tissues to promote growth & development
-Anabolic :promotes protein synthesis
-Principle targets:muscles and bone
GH hypersecretion in children -gigantism(very tall-8 feet)
GH hyposecretion :pituatry dwarfism shorrt-4 feet

Question 22

What are the metabolic effects of the growth hormone ?

Answer 22

GH increases blood glucose uptake and increase glycogenolysis
stimulas :hypoglycemia
direct effect on proteins ,fats,carbohydrates
Skeletal growth –>

Question 23

What are the functions of prolactin ?

structuarally similar to GH

Answer 23

in females
-promotes maturity of mammary glands during pregenancy
-stimulates synthesis of milk(lactation)
-its secretion is increased by suckling
-Prolactinoma :lactating men
-Prolactin function have evolved

Question 24

What is the function & anatomy of the adrenal galnd ?

Answer 24

located at superior pole of each kidney (suprarenal ):consist of of inner medulla & outer cortex
-2 distinct endocrine functions:secretion
-Catelcholamines(adrenaline,noradrenaline) in response to sympathetic nerve action
3 classes of steroid hormones :
glucocorticoids,mineralcorticords,sex steroids

Question 25

What is the function of adrenal cortex ?

endocrine function

Answer 25

controlle hormonally
humans-cortisol is dominant glucocorticod rapidly relesing from cells by diffusion following synthesus mostly bound to plasma binding membrane (in blood)

endocrine system

Question 26

How does the HPA axis link to Adrenal cortex ?

Answer 26

Cortisol is regulated by the hypothalamic -pituatry-adrenal (HPA) axis
Diurnal variaition in cortisol
Circulating glucocorticods inhibit secretions of CRH & ACTH by hypathalamus and anterior pituatry

CRH = corticotropin relaesing hormone
ACTH =adrenocorticotropin hormone

Question 27

What does cortisol control ?

Answer 27

Control of carbohydrate and protein metabolism
counteracts stress:trauma,intense heat or cold,infection

main glucocortoid in primates & fish is cortisol .In reptiles ,amphibian

Question 28

What is the stress response ?

short term

Answer 28

activation of both the sympathetic nervous system & HPA axis
short term response
1. glycogen broken down to glucose ; ↑ blood glucose
2. ↑ blood pressure
3. ↑ breathing rate
4. ↑ metabolic rate
5. change in blood flow patterns leading to ↑ alertness and decrease kidney & digestive activity

Question 30

What is the long term stress response ?

Answer 30

1. Retention of sodium ions & wayer by kidneys
2. ↑ blood volume & blood pressure
3. Proteins & afts broken down and converted to glucose leading to ↑ blood glucose
4. immune sytem may be supressed

cortisol:high levels supress normal immune response to infection
A & NA

Question 31

Define stress?

Answer 31

adverse reaction people have to excessive pressures or other types of demand placed on them

Question 32

Defines stress response ?

Answer 32

the resonpse of an animal to a threatening/hostile or challenging situation

stressors:wounded,thermal extremes,social condititon
essential ebhaviou

Question 33

What is stress repsonse associated with ?

Answer 33

with physiological changes ensure survival in acute crisis
healthy ,normal reaction
feedback meechanisms ensure stress response is turned off

Question 34

What is chronic stress ?

Answer 34

stressor persists for long periods can be damaging
can lead to hypertension (↑ BP) susceptibility to infections ,supression pf reprosuctive function

Question 35

Female human reproductive cycle ?

brief overview

Answer 35

2 linked cycles
1.Ovarian cycle :produces eggs and ovarian hormones
-involves follicle development ,ovulation ,growth ajnd eventual degeneration of the corpus luteum
2.Uterine cycle (mestrual cycle)
prepeates unterine endometrium for blastocyst implantation
involves ‘build up’ of the endometrium
in absence of implantation endometrium ‘sloughs off’ and menstruation occurs (in most mammals no bleeding)

FSH symulates follicle development ,LH surge causes ovulation
oestrogen

Question 36

Hormonal control of ovarian cycle ?

Answer 36

Puberty:Hypothalamus ↑ GnRH release stimulates release of gonadotropins (FSH,LH) from anterior pituatry
FSH ,LH cause growth of ovarian tissue ;ovarian hormones are produced
-First 12 days oestrogen inhibits LH & FSH release
12-14 days :oestrogen exerst positive feedback-> LH surge :triggers ovulation

Question 37

What does the corpus luteum function as ?

Answer 37

functions as an endocrine gland:produces oestrogen and progesterone

Question 38

Negative feedback and the difference between short vs long ?

Answer 38

Endocrine cells are also under the direct/indirect negative feedback control by hormones of target glands they stimulate
long loop example :HPA axis –>cortisol can ihibit both ACTH & CRH
short loop :ACTH

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