Leture 13 - Endocrine System Flashcards
1
Q
Endocrine Cells
A
- cells that produce and release hormones
2
Q
Endocrine Gland
A
Group of endocrine cells forming a secretory organ
3
Q
Hormones
A
chemical signal released by endocrine cells that influences the activity of other cells at a distance
4
Q
Long distance signaling
A
- travel through blood stream
- blind to receptors on or in distant target cells
- target cell must have the proper receptor to bind the hormone
5
Q
Timing of endocrine system:
Coordination fo endocrine system:
A
- longer to turn on and off than more direct signaling (ie neurotransmitters)
- can coordinate many different responses
6
Q
3 chemical groups of hormones
A
- Peptide or protein hormones
- steroid hormones
- Amine hormones
7
Q
Peptide/protein hormones
A
- majority of hormones
- ex: insulin
- water soluble
- transported through blood without carriers
- receptors on the cell surface
8
Q
steroid hormones
A
- ex: testosterone
- synthesized from cholesterol
- lipid soluble
- easily pass through cell membranes
- bound to carrier molecules in blood
- receptors are mostly intracellular (in cytoplasm or nucleus)
9
Q
Amine hormones
A
- ex: thyroxine
- synthesized from the amino acid tyrosine
- can be water soluble OR lipid soluble
10
Q
Cell’s response to a signal depends on:
A
which receptors it possesses
- for that particular signal
- different types of cells have different types of receptors that bind the ligand –> different responses
11
Q
Receptors and intracellular pathways
A
- intracelllula rpathways activated by a particular receptor differ
- same receptor that binds ligand, but different responses
- due to cell’s predetermined state
*which “responders” are called to scene of activation
12
Q
Same Hormone, different responses in different cells…
Epinephrine
A
Ex: epinephrine
- one hormone can bind to receptors in many different tissues
- initiates fight or flight response
- heart pumps faster and stronger
- blood vessels to skin and gut constrict, shunting blood to muscles
- liver breaks down glycogen to supply glucose to blood
- fat cells release fatty acids to blood
13
Q
Receptor Specificity of Cells
A
- No receptor at all = no response
- different receptors might bind the same hormone = different pathways activated in those cells = different responses
14
Q
Control of hormone release
A
- brain responds to environmental conditions
- provide a signal to the endocrine cells to release hormones
- hormones released into blood stream
- bind to receptors on target cell
- physiological response
15
Q
Step 1: Brain communicated with endocrine system
A
- Hypothalamus: integrates infotmation from body and environment and communicates this to endocrine system
- sends it to the “control center”/pituitary gland of endocrine system
- pituitary then regulates other glands of body
16
Q
Pituitary
A
“mouthpiee through which the brain speaks to the body”
2 lobes:
- anterior
- posterior
- Hypothalamus speaks to pituitary
- regulates each lobe differently
17
Q
Posterior Pituitary
A
- NO secretory cells
- just capillaries
- hypothalamus releases neurohormones into capillaries in posterior pituitary
- hypothalamus axons extend down to posterior pituitary
- release hormones that go into blood stream
- from there, continue circulating through body
18
Q
Two hormones released by hypothalamus
A
- oxytocin
(childbirth, lactation, promotes bonding) - ADH
( increases water conserved by kidneys, inresponse to blood volume and salt concentration)
19
Q
Anterior pituitary
A
- an actual gland that synthesizes and releases itw own hormones
- neurones from the hypothalamus do not project all the way to pituitary
- release hormones onto blood vessels that run to anterior pituitary
- releasing hormones and releasing inhibiting hormones
- these hormones cause pituitary cells to secrete or stop secreting hormones into blood stream
20
Q
Type of hormones released by anterior pituitary
A
Tropic hormones
- control activities of other endocrine glands
- tropic hormones act on thyroid, adrenal gland, testes and ovaries
- ex: corticotropin –> signal the adrenal gland to release cortisol
21
Q
The Stress Response
A
- Hypothalamus:
- releases Corticotropin releasing hormone (CRH) - Ant Pituitary
- CRH causes pituitary to release corticotropin into blood stream - Adrenal Glan
- Corticotropin causes Adrenal gland to release cortisol - Cortisol
- mobilizes energy reserves
- supresses immune system
- effect neuron activity in short- and long-term
22
Q
Negative feedback loop
A
- endocrine cells in pituitary are also under negative feedback control by hormones f the glands that they stimulate
- tropic hormones released from pituitary stimulates release of a hormone from another endocrine gland
- this second hormone inhibits release of more tropic hormone from the pituitary
Ex: stimulates adrenal gland to release cortisol. Cortisol inhibits further release of corticotropin and corticotropin release hormone
23
Q
Thyroid gland
A
Hormones regulate its two main functions:
- cell metabolism (thyroxine)
- regulation of blood calcium levels (calcitonin, parathyroid hormone - PTH, calcitrol)
24
Q
Thyroxine synthesis
A
- release stimulates by thyroid stimulating hormone (TSH) produced by anterior pituitary
- thyroxine is modified by iodine atoms
- initially four iodine atoms are added onto the hormone
- Thyroid releases mostly T4 into bloodstream
- but thyroxine is active when only 3 iodines are on it, T3
- T4 is converted to T3 by an enzyme in the target cells
- therefore each target cell can set its own sensitivity to thyroid hormones by controlling the conversion step
25
Role of Thyroxine
Regulates cell metabolism:
Elevates metabolic rates of most cells and tissues
- most cells int he body have thyroxine receptor
- promotes amino acid uptake and protein synthesis
- very important during development
hypothalamus regulates release in response to temperature, day length, etc
- ex: exposure to cold leads to increased level of thyroxine
26
Hyperthyroidism
- excess production of thyroxine
| - high metabolic rates, jumpy/nervous, feel hot
27
Hypothyroidism
- deficiency of functional thyroxine
- low metabolism, intolerance of cold, physical and mental sluggishness
- ex: iodine deficiency
* can both lead to goiter
28
Thyroid gland and blood calcium concentrations
Regulates blood calcium concentrations:
- 99% of body calcium is stored in bones
- very important for the amount circulating in the blood to be tightly regulated
- body has multiple mechanisms for changing blood calcium levels:
1. deposition of absorption levels
2. excretion or retention of calcum (by kidneys)
3. absorbption of calcium from digestive tract
29
3 hormones that regulate blood calcium levels
1. calcitonin
2. parathyroid hormone (PTH)
3. Calcitrol
30
Calcitonin
Blood calcium too high:
- reduces blood calcium
- its deposited into bone
- more important in young individuals that are actively growing
31
Parathyroid hormone
Blood calcium levels too low:
- increase in blood calcium
- breakdown of bones releases calcium
- most important hormone in regulation of blood calcium levels
- activates synthesis of calcitrol
32
calcitrol
Blood calcium levels too low:
- synthesized from vitamin D
- stimulates kidneys and git to reabsorb calcium back into the blood rather than excrete it
33
Pancreas
Produces insulin and glucagon
34
Insulin
- released in response to eating a meal (high blood glucose)
- stimulates insertion of glucose transporters into cell membrane
- glucose can enter cell and be used as fuel
- also promotes storage of glucose as glycogen in liver
1. glucose as fuel
2. storage of glucose as glycogen
35
Glucagon
- released in response to low blood glucose levels
| - stimulates the lover to break down the stored glycogen and release glucose
36
Diabetes Mellitus
- lack on insulin (type i)
- lack of insulin responsiveness in target tissues (Type ii)
- glucose entry into cells is impaired
- high blood sugar
- cells suffer from a lack of metabolic fuel
37
Adrenal Gland
Medulla and cortex
38
Adrenal medulla
- inner core
- epinephrine
- norepinephrine
- acute release in response to stresful situations
- direct innervation from autonomic nervous system
- fight or flight response
39
Adrenal cortex
- surrounds medulla
- produces steroid hormones
- ex: cortisol
- release controlled by corticotropin from anterior pituitary
- slower to turn on, longer lasting stress response
- mobilizes energy reserves
- suppress immune system
40
Cortisol and chronic stress
- cortisol release normally turned off by negative feedback
- repeated activation of cortisol system has been shown to lead a decreased inability to terminate the stress response
- old rats also shown to be able to turn on stress response as well as young ones, but unable to turn it off as effectively
- digestive system problems, cardiovascur problems, strokes, impaired immune system
- mice given daily injections of cortisol show signs of neuron death
41
Gonads and their hormones
Male: testes
- produce androgens --> testosterone
female: ovaries
produce estrogen, progesterone
42
Pineal gland
- produces melatonin
- melatonin released int he dark
- marks length of the night
- exposure to light inhibits its production
- involved in biological rhythms
43
Photoperiodicity
- changes in day length cause physiological changes
Ex: siberian hamsters
- white in winter and do not reproduce
- brown in summer and breed
44
How does the body change blood calcium levels?
1. deposition of absorption levels
2. excretion or retention of calcum (by kidneys)
3. absorption of calcium from digestive tract
45
Importance of sex hormones
Development:
- Y chromosome --> gonads produce androgens in 7th week of development
- androgens --> undifferentiated reproductive system into a male
Puberty:
- production of sex steroids increases dramatically at the beginning of uberty
- hypothalamus stimulates pituitary to release gonadotropins
- gonadotropins stimulate release of sex hormones from gonads
- initiate development of secondary sex characteristics
