Endocrine System Flashcards
1
Q
Endocrine system
A
- endocrine system and nervous system work together
- endocrine system:
- hormones released into bloodstream travel throughout body
- results may take hours but last longer
- nervous system
- releases neurotransmitters to excite or inhibit nerve, muscle and gland cells
- results in milliseconds, brief duration of effects
2
Q
Hormone receptors
A
-hormones only affect target cells with specific membrane proteins called receptors
3
Q
Role of hormone receptors
A
- constantly being synthesized and broken down
- a range of 2000-100,000 receptors/ target cells
- up-regulation:
- deficiency of hormone, produces and increased number of receptors to up take more
- target tissue more sensitive to hormone
- down regulation
- excess hormone, produces a decrease in number of receptors
- receptors undergo endocytosis and are degraded
- decreases sensitivity of target cell hormone
4
Q
Hypothalamus and pituitary gland
A
- both are master endocrine glands wince their hormones control other endocrine glands
- hypothalamus receives input from cortex, thalamus, limbic system and internal organs
- hypothalamus is connected to pituitary gland by a stalk called the infundibulum
5
Q
Anatomy of pituitary gland
A
- pea shaped gland found in sella turcica of sphenoid
- infundibulum attaches it to brain
- anterior lobe: 75%
- connected to hypothalamus by portal veins
- posterior lobe: 25%
- ends of axons of neurons found in hypothalamus
- stores and releases neurotransmitters/hormones into blood stream
6
Q
Flow of blood to anterior pituitary
A
- controlling hormones enter blood
- travel through portal veins
- enter anterior pituitary at capillaries
7
Q
Anterior pituitary (adenophypophysis) secretions
A
- 7 major hormones secreted by 5 cell types:
- HGH
- TSH
- ACTH
- FSH
- LH
- PRL
- MSH
8
Q
Human growth hormone (anterior pituitary)
A
- produced by somatotrophs
- common target cells are liver, skeletal muscles, cartilage and bone
- increases cell growth and cell division by increasing their uptake of amino acids and synthesis of proteins
9
Q
Thyroid stimulating hormone (anterior pituitary)
A
- produced by thyrotrophs
- TSH stimulates the synthesis and secretion of T3 and T4 from thyroid gland
- metabolic rate stimulated
10
Q
Follicle stimulating hormone (anterior pituitary)
A
- gonadotrophs release FSH
- initiates the formation of follicles within ovary
- stimulated follicle cells to secrete estrogen
- stimulated sperm production in testes
11
Q
Luteinizing Hormone (anterior pituitary)
A
- produced by gonadotrophs
- in females LH stimulates:
- secretion of estrogen
- ovulation of 2nd oocyte
- formation of corpus luteum
- secretion of progesterone
- in males, stimulates interstitial cells to secrete testosterone
12
Q
Prolactin (anterior pituitary)
A
- produced by lactotrophs
- PRL causes milk production in women
- function not known in males
13
Q
Adrenocorticotrophic hormone (anterior pituitary)
A
- ACTH produced by corticotrophs
- ACTH stimulated cells of adrenal cortex that produce glucocorticoids
14
Q
Melanocyte stimulating hormone (anterior pituitary)
A
- secreted by corticotrophs
- function not certain in humans
- increases skin pigmentation in frogs
15
Q
Posterior pituitary (neurohypophysis)
A
- doesn’t synthesize hormones
- consists of axon terminals of hypothalamic neurons
- neurons release 2 neurotransmitters that enter capillaries
- antidiuretic hormone
- oxytocin
16
Q
Antidiuretic hormone (posterior pituitary)
A
- ADH also known as vasopressin
- response to low BP
- decrees urine production
- decrease sweating
- increase BP
- increase thirst
17
Q
Oxytocin (posterior pituitary)
A
- 2 target tissues - both involved in neuroendocrine reflexes
- during delivery:
- baby’s head stretches cervix
- hormone released enhances uterine muscle contraction
- baby and placenta delivered
- after delivery:
- suckling and hearing baby’s cry stimulates milk ejection
- hormone causes muscle contraction and milk ejection
18
Q
Thyroid gland
A
- on each side of trachea is lobe of thyroid glands joined by isthmus
- consists of (simple cuboidal) follicular cells surrounding follicle filled with precursor substance (thyroglobulin)… active form is T3 or T4
- material produced and stored outside cells
- up taken by cells and activated when needed
- T3: triiodine hormone
- T4: tetraiodine hormone
19
Q
Thyroid hormone functions
A
- regulate oxygen use and metabolic rate
- cellular metabolism increase
- growth and development
- controlled by pituitary
20
Q
Histology of thyroid gland
A
- follicle: sac of stored hormone (colloid) surrounded by follicular cells that produce it
- in between cells are called parafollicular cells
- parafollicular cells produce calcitonin, which decreases blood calcium levels by decreasing activity of osteoclasts and excretion by kidneys
21
Q
Parathyroid glands
A
- 4 glands
- posterior to thyroid gland
- principle cells produce parathyroid hormone (PTH)
- oxyphil cell function is unknown
22
Q
Parathyroid hormone
A
- raise blood calcium levels
- increase activity of osteoclasts
- increases reabsorption of calcium by kidney
- promote formation of calcitriol (Vit D) by kidney and liver which increases absorption of calcium by intestinal tract
- opposite function of calcitonin
23
Q
Adrenal Glands
A
- one on top of each kidney
- controlled by pituitary gland
- good blood supply
- 2 glands in 1: cortex and medulla
24
Q
Histology of adrenal gland
A
- cortex produces 3 different types of hormones from 3 zones of cortex
- zona glomerulosa: mineralocorticoids
- zona fasciculata: glucocorticoids
- zona reticularis: androgens
-medulla produces epinephrine and norepinephrine and secretes into blood
25
Function of adrenal cortex
- minerlocorticoids (aldosterone) secreted in response to low blood pressure, signals kidneys to absorb more sodium and water
- glucocorticoids (cortisol) secreted in response to stress, raises blood sugar levels and also used as anti inflammatory agent (over use reduces immune response)
- androgens have masculinizing effects (sex producing hormones)
26
Function of adrenal medulla
- chromatin cells receive direct innervation from sympathetic nervous system
- develop from same tissue as postgangionic neurons
- produces epinephrine and norepinephrine
- hormones are sympathomimetic
- effects mimic those of sympathetic NS
- prepare for fight or flight
- longer effects due to hormone in blood
27
Cushing syndrome
- over secretion of aldosterone
| - fats destroyed and reorganized
28
Anatomy of Pancreas
- located in upper abdomen
- consists of head, body, tail
- exocrine and endocrine
- cells (99%) in acini produce digestive enzymes (exocrine)
- endocrine cells in pancreatic islets produce hormones: islets of langerhans
29
Cell organization in pancreas
- exocrine acinar cells surround a small duct
- endocrine cells secrete near a capillary
- lumina of acina connect together to form duct
30
Cell types in pancreatic islets
- alpha cells (20%) produce glucagon to increase blood sugar levels
- beta cells (70%) produce insulin to decrease blood sugar levels
- delta cells (5%) produce somatostatin to reduce secretions of alpha and beta cells
- F cells produce pancreatic polypeptides to inhibit activity of exocrine part of pancreas
31
Ovaries and testes
- ovaries
- estrogen, progesterone, relaxin & inhibin (under effect of FSH)
- regulate reproductive cycle, maintain pregnancy and prepare mammary glands for lactation
- testes
- interstitial cells produce testosterone (under effect of LH)
- regulate sperm production and secondary sexual characteristics
32
Pineal gland
- small gland attached to 3rd ventricle of brain
- consists of pinealoctyes (secrete melatonin) and neuroglia (CT cells)
- melatonin responsible for setting of biological clock
33
Effect of light on pineal gland
- melatonin secretion producing sleepiness occurs during darkness due to lack of stimulation from sympathetic ganglion (inhibits melatonin release)
- sympathetic fibres from superior cervical ganglia terminate in pineal gland
- inhibits melatonin release
34
Thymus gland
- important role in maturation of T cells in infants and children
- hormones produced by gland promote the proliferation and maturation of T cells
- thymosin
- thymic humoral factor
- thymic factor
- thymopoietin
- located in mediastinum in thorax
