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HUBS191 P2 > homeostasis > Flashcards

homeostasis Flashcards

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1
Q

homeostasis

A

the presence of a relatively stable internal environment

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2
Q

normal range is?

A

an individual’s normal range within which their levels of a given variable fluctuate

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3
Q

reference range is?

A

the populations reference range based on the breadth of individual normal ranges within a population. the population reference range tends to be wider than normal fluctuations within an individual:

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4
Q

features of neural (aka synaptic) control system (4 features)

A
  • action potentials in axons and neurotransmitter release at synapse
  • targeting achieved by specific ‘wiring’
  • fastest transmission speed (compared to endocrine), to minimise response delays
  • good for brief responses
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5
Q

features of endocrine control system (3 features)

A
  • hormones released into the blood
    targeting by presence of specific receptors on target cells
  • relatively slow, but long lasting action
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6
Q

endocrine system (secrete-travel-target) consists of (4 facts)

A
  • endocrine gland cells that secrete hormones
  • these are carried in the bloodstream to the target cells upon which they act
  • target cells are mainly in other distant tissues and organs
  • target cells must have appropriate receptors
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7
Q

major endocrine glands

7 glands

A 
hypothalamus
pituitary gland
thyroid gland
adrenal gland
pancreas (pancreatic islets)
pineal gland
parathyroid glands
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8
Q

hypothalamus does?

A

links the nervous system to the endocrine system and controls the secretion of many endocrine glands

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9
Q

organs with secondary endocrine functions

5 organs

A 
heart
thymus
digestive tract
kidneys
gonads - testis, ovary
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10
Q

hormones

A

true hormones are chemical messengers produced in one location and transported via the bloodstream to a second location (target cells) where they cause a response in those cells

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11
Q

specificity of hormone action

what is the only thing a hormone can affect?

A

a hormone can only affect cells with specific receptors for that hormone. each receptor is a protein. it can be in the target cell membrane or inside the target cell

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12
Q

water soluble hormones

chemical classification

A

mostly peptides (75% of hormones), some catecholamines include adrenaline and noradrenaline

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13
Q

water soluble hormones

storage classification

A

made and stored until required (released by exocytosis)

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14
Q

water soluble hormones

transport classification

A

travel dissolved in the blood

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15
Q

water soluble hormones

receptors classification

A

cell surface

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16
Q

water soluble hormones

mechanism of action classification

A

through 2nd messengers

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17
Q

water soluble hormones

speed of response classification

A

milliseconds to minutes

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18
Q

Lipid (fat) soluble hormones

chemical classification

A

steroids

thyroid hormones including both T3 and T4

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19
Q

Lipid (fat) soluble hormones

storage classification

A

steroids are made from cholesterol as required

thyroid hormones are made in thyroid cells and stored until required

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20
Q

Lipid (fat) soluble hormones

transport classification

A

travel in blood bound to a carrier protein

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21
Q

Lipid (fat) soluble hormones

receptors classification

A

intracellular receptors in cytoplasm or nucleus

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22
Q

Lipid (fat) soluble hormones

mechanism of action classification

A

by altering gene transcription

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23
Q

Lipid (fat) soluble hormones

speed of response classification

A

hours to days

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24
Q

where are the water soluble hormone receptors located?

A

cannot cross the cell membrane, therefore receptors are located in target cell/plasma membrane

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25
where are the lipid soluble hormone receptors located?
can diffuse across the cell membrane into the target cell, therefore receptors are located in the cytoplasm or nucleus
26
cellular response to receptor activation | water soluble hormones (4 steps)
1. water soluble hormone binds to cell surface receptor 2. hormone binding allows activation of associated G-protein 3. G-protein activates/inhibits second messenger production/reduction 4. downstream proteins/pathways are activated or deactivated
27
cellular response to receptor activation | lipid soluble hormones (8 steps)
0. lipid soluble hormone dissociates from carrier protein 1. hormone diffuses across cell membrane 2. hormone binds to intracellular receptor 3. hormone-receptor complex acts as a specific transcription factor 4. target gene is generated 5. new mRNA is generated 6. new protein is generated by translation of mRNA 7. new protein mediates cell specific response (slow process)
28
maintenance of hormone levels for?
need to maintain hormone levels to maintain effects of hormones
29
maintenance of hormone levels | negative feedback
most common | reduce change until stimulus is removed or directly inhibit further release
30
maintenance of hormone levels | positive feedback
occasionally | amplification of change until a desired outcome is achieved
31
control of hormone secretion is?
amount of hormone depends on rate of hormone secretion, rate of removal from blood
32
control of hormone secretion | what is secretion usually controlled by?
negative feedback loops, most use negative feedback control
33
control of hormone secretion | what does deviation do?
occurs in a system and is detected by a 'receptor' and recognised by a control centre (sometimes the same organ is the 'receptor' and control centre, sometimes they are different).
34
control of hormone secretion | a mechanism is activated to?
bring the variable back to the set point (or reference range), change occurs in effectors
35
control of hormone secretion | in the long term, the secretion rates of many hormones?
are maintained at a fairly constant level by negative feedback
36
control of hormone secretion | a few hormones use?
positive feedback (at specific times)
37
control of hormone secretion | the goal of hormones is to?
maintain homeostasis | too much or too little hormone can lead to endocrine disorders
38
pancreas
an exocrine gland and an endocrine gland
39
pancreatic islets
~1% of mass beta cells secrete insulin alpha cells secrete glucagon
40
energy utilisation and storage | blood glucose concentration must be?
maintained within a narrow range at all times for normal functioning (homeostasis)
41
energy utilisation and storage | diabetes develops if?
blood glucose concentration is too high for too long
42
energy utilisation and storage | hypoglycemia occurs if?
blood glucose concentration is too low
43
energy utilisation and storage | what must the brain be supplied with at all times and why?
glucose as glucose is the only fuel that the brain uses
44
energy utilisation and storage | why do blood glucose levels fluctuate throughout the day?
because we use fuel continuously but eat intermittently
45
energy utilisation and storage | two metabolic states
fed state | fasting state
46
energy utilisation and storage | fed state
cellular uptake of nutrients and anabolic metabolism | synthesis of glycogen, protein and fat
47
energy utilisation and storage | fasting state
mobilisation of nutrients and catabolic metabolism | breakdown of glycogen, protein and fat
48
hormone regulation
insulin and glucagon maintain blood glucose concentration between 70-110 dL-1
49
pituitary gland | location
base of the brain and attached to the hypothalamus
50
pituitary gland | controls the?
secretion of pituitary hormones (when activated by neural input, the hypothalamus stimulates the pituitary gland to secrete hormones)
51
pituitary gland what do pituitary hormones do? (2 jobs)
some stimulate target cells | some stimulate the secretion of hormones by other endocrine glands
52
pituitary gland | two part of the pituitary gland are?
anterior lobe | posterior lobe
53
pituitary gland posterior lobe connected to the hypothalamus by?
neurons - cell bodies in the hypothalamus | axons terminate in the posterior lobe
54
pituitary gland posterior pituitary hormones 3 facts
made in hypothalamus (cell body of the neuron) travel down the axon stored at the axon endings until required (peptide hormones)
55
pituitary gland posterior lobe communication
hypothalamus uses neural communication with the posterior lobe to release hormones into the blood: increased (or decreased) frequency of action potentials leads to corresponding change in hormone release
56
pituitary gland posterior lobe what two hormones can be released into the blood by means of the posterior lobe?
antidiuretic hormone (ADH or oxytocin
57
pituitary gland posterior lobe antidiuretic hormone
stimulates kidneys to reabsorb water (the kidneys conserve water when the body dehydrates)
58
pituitary gland posterior lobe oxytocin
stimulates the contraction of uterine muscles during childbirth (an example of positive feedback) stimulates milk release in breastfeeding (milk ejection reflex)
59
pituitary gland posterior lobe hormones made and stored where?
both hormones are made in the hypothalamus and stored in the posterior pituitary until required
60
pituitary gland anterior lobe connected to the hypothalamus by?
blood vessels | hypothalamic hormones stimulate or inhibit release of stored hormones from specific anterior pituitary cells
61
pituitary gland anterior lobe communication 3 steps
stimulus - neural input within hypothalamus hypothalamus signals the anterior pituitary to release hormones by hormonal stimulation, secreting stored releasing hormone (or inhibiting hormone) hormone binds to receptor on membrane of a specific cell type and a specific anterior pituitary hormone is secreted e.g. prolactin, growth hormone
62
pituitary gland anterior lobe feedback regulation of the anterior pituitary gland 4 steps
hypothalamus releasing hormone ---> anterior pituitary gland releasing the pituitary hormone ---> target organ to release another hormone ---> hormone has an effect
63
pituitary gland anterior lobe 8 hormones
``` GH-RH GH-IH (SS) TRH PIH PRH PRL GnRH CRH ```
64
pituitary gland anterior lobe GH-RH function, target gland, secretes?
stimulates release of growth hormone liver IGF-1
65
pituitary gland anterior lobe GH-IH (SS) function
inhibits the release of growth hormone and TSH
66
pituitary gland anterior lobe TRH function, target gland, secretes?
stimulates the release of TSH thyroid T3 and T4
67
pituitary gland anterior lobe PIH function
inhibits the release of TSH and PRL
68
pituitary gland anterior lobe PRH function, target gland, secretes?
stimulates the release of PRL mammary breast milk
69
pituitary gland anterior lobe PRL function
inhibits the release of GnRH
70
pituitary gland anterior lobe GnRH function, target gland, secretes?
stimulates the release of FHS and LH gonads estrogen and testosterone
71
pituitary gland anterior lobe CRH function, target gland, secretes?
stimulates the release of ACTH adrenal cortex cortisol
72
pituitary gland anterior lobe growth hormone activity in the hypothalamus
one set of neurons will release the growth hormone releasing hormone and one set of neurons will release the growth hormone
73
pituitary gland anterior lobe growth hormone travels to?
the anterior pituitary gland where the growth hormone is released then travels to the liver and causes it to release somatomedin C (IGF-1) which will cause effects in the body
74
pituitary gland anterior lobe growth hormone once the growth hormone has been released what feedback to we get and why?
negative feedback to the hypothalamus to limit GH-RH release | and negative feedback to anterior pituitary via stimulation of hypothalamus to release GH-IH
75
pituitary gland anterior lobe growth hormone direct effects - muscle
stimulates protein synthesis (long term) and inhibits cellular uptake of glucose (short term)
76
pituitary gland anterior lobe growth hormone direct effects - liver
stimulates glucose synthesis (short term)
77
pituitary gland anterior lobe growth hormone direct effects - fat
increases triglyceride breakdown in adipose tissue (short term)
78
pituitary gland anterior lobe growth hormone indirect effects (2)
promotes the growth of bones, muscle and other tissues by causing release of somatomedin C which promotes cell division (long term) GH has a long term effect on growth and short-term effects on metabolism

HUBS191 P2 (9 decks)

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