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Mammalian Physiology > Slide Set 3 > Flashcards

Slide Set 3 Flashcards

1
Q

2 basic types of physiological signals

A

Electrical : involve changes in membrane potential

Chemical : molecules secreted by cells into extracellular fluid

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2
Q

4 methods of cell-cell communication

A

Gap Junctions
Contact-dependent signals
Chemicals that diffuse
Long-Distance communication

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3
Q

Gap junctions

A
  • simplest form of cell-to-cell communication
  • direct transfer of E and C signals
  • creates cytoplasmic bridges between adjacent cells
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4
Q

Which molecules can pass or can’t go through a gap junction

A

can : ions, amino acids, ATP, cAMP

can’t : large molecules

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5
Q

Connexins

A

= proteins on the membrane that connects the cell in a gap junction

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6
Q

What is the only means by which electrical signals can pass directly form cell to cell

A

gap junctions

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7
Q

Contact-dependent signals

A
  • interaction between membrane surface molecules on 2 cells
  • immune system, growth, development
  • Cell-adhesion molecules (CAMs)
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8
Q

What are CAMs

A

= Cell-adhesion Molecules
Are present in contact-dependent signals
They transfer signals, like integrins

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9
Q

Chemical signalling

A
  • paracrine : signals secreted by ONE cell and diffuse to the NEXT
  • autocrate : signals act on the SAME cell that secreted them
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10
Q

Long-distance communication

A
  • HORMONES
  • NEUROTRANSMITTERS
  • Cytokines
    (also local signalling)
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11
Q

HORMONES

A

Long-distance

  • secreted by endocrine glands/cells into the blood
  • cells with RECEPTORS for the hormone (“lock & key”) will respond to the signal
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12
Q

NEUROTRANSMITTERS

A

Long-distance
= chemicals secreted by neutrons that diffuse across a small gap to the target cell
- use chemical and electrical signals
- have a rapid effect

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13
Q

Neurohormones

examples :

A

chemicals released by neutrons into the blood for action at a distant target
examples : norepinephrine and epinephrine

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14
Q

CYTOKINES

A

Local and long-distance signals

  • all nucleated cells synthesise and secrete them
  • control cell development, differentiation, immune responses
  • have a broader action than hormones
  • made on demand, not stored
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15
Q

Difference between cytokines & hormones

A

Cytokines act on a broader spectrum of target cells than hormones. Are like hormone but not produced by a gland, they are made on demand.

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16
Q

Signal pathways

A
  1. Ligand/first molecules brings info/signal to target cell
  2. Ligand-receptor binding activates the receptor
  3. receptor activates one or more intracellular signal molecules
  4. Last signal molecule initiates synthesis of target proteins or modifies existing target proteins to create a response
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17
Q

Signal molecule -> binds to __ -> activates intracellular signal molecule -> alters __ -> response

A

receptor protein

target proteins

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18
Q

Where are receptor proteins located

A

Inside cell or on the cell membrane

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19
Q

Location of ligand/receptor binding is dependant on whether a signal molecule is __ or __

A

hydrophobic or hydrophilic

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20
Q

__ signal molecules can diffuse through the phospholipid bilayer binding to __ or __ receptors

A

Hydrophobic
Cytoplasmic
Nuclear

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21
Q

Receptor activation often turns on or off a _

This is a relatively __ process

A

gene

slow

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22
Q

Lipophobic signal molecules __ diffuse through the plasma membrane

A

CAN’T

  • they bind to extracellular receptors (on plasma membrane)
  • causes a cascade of events
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23
Q

Lipophobic molecules

hydrophilic

A
  • bind to extracellular receptors on plasma membrane

- very rapid response

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24
Q

Lipophilic molecules

hydrophobic

A
  • diffuse through phospholipid bilayer
  • bind to cytoplasmic or nuclear receptors
  • slow process
    (some can bind to membrane receptors in addition to intracellular receptors)
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25
Q

Why is the response slower for lipophilic signal molecules?

A

Because this is related to changes in genes activity,

the receptors bind in the nucleus

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26
Q

Where are receptors for lipophilic signal molecules?

A
  • in cytosol

- in nucleus

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27
Q

Signal pathway of lipophobic signal molecules

A
  • bind to cell membrane receptor
  • forms ligand-receptor complex
  • rapid cellular response :
    • Initiates transduction by proteins
    • second messenger
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28
Q

What is the role of the second messenger

A
  • alters gating of ion channels
  • increases intracellular calcium
  • changes enzyme activity (protein kinases, protein phosphatases)
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29
Q

Steps of signal transduction pathway form a __

A

CASCADE:

inactive A becomes active A thanks to a stimulus, leased to inactive B becoming active B etc until product

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30
Q

Example of receptor-enzyme

A

tyrosine kinase

  • is on the cytoplasmic side
  • it transfers a phosphate group from ATP to a tyrosine of a protein
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31
Q

Peptide hormones are lipophilic or lipophobic?

ex: insulin, glucagon, leptin, ADH, oxytocin

A

Lipophobic : they can’t cross freely the plasma membrane

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32
Q

What do most signal transduction use?

A

G proteins

They bind nucleotide guanosine

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33
Q

G protein coupled receptors

A

Membrane spanning proteins that cross phospholipid bilayer 7 times
When activated, they open ion channels in the membrane and alter enzyme activity on the cytoplasmic side of the membrane

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34
Q

GPCR : Adenyl Cyclase - cAMP

A
  1. signal molecule binds to G protein-linked receptor, activates G protein
  2. G protein turns on adenylyl cyclase, an amplifier enzyme
  3. Adenylyl cyclase converts ATP to cyclic AMP
  4. cAMP activate protein kinase A
  5. PKA phosphorylates other proteins, leading to a cellular response
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35
Q

GPCR : Phospholipase C system

A
  1. signal molecule activates receptor and associated G protein
  2. G protein activates phospholipase C an amplifier enzyme
  3. PLC converts membrane phospholipids into diacyglcyerol which remains in the membrane, and IP3, which diffuses into the cytoplasm
  4. DAG activates protein kinase C which phosphorylates proteins
  5. IP3 causes release of calcium from organelles, creating a calcium signal
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36
Q

Which enzymes is responsible for phosphorylation go other proteins?

A

Protein kinase A, C

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37
Q

Signal pathway : receptor channel

A
  • ion channels also serve for signal transduction
  • extracellular ligand binds to the receptor - channel protein, a channel gate opens or closes
  • initiates most rapid response
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38
Q

Between receptor-channel, PLC, AC-cAMP transduction, which initiates the fastest response?

A

receptor-channel

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39
Q

Calcium ions

A
  • versatile intracellular messenger
  • second messenger
  • enter through voltage-gates calcium channels or ligand/mechanically gated channels
  • inside, calcium can bind to calmodulin which alters protein activity
  • inside, calcium can also bind other proteins
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40
Q

A change in ion concentration inside the cell creates

A

electrical signal

this triggers release of calcium from organelles

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41
Q

An agonist and primary ligand ->

A

activates a receptor -> response

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42
Q

An antagonist ->

A

blocks the receptor activity -> no response

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43
Q

Endocrine and nervous system

A
  • function to achieve and maintain homeostasis
  • are connected
  • communication, integration, control
  • when work as one system = neuroendocrine system
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44
Q

Endocrine system

A
  • wireless
  • glands aren’t linked with their target cells
  • chemical messengers are secreted into blood and delivered to DISTANT target sites
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45
Q

Nervous system

A
  • each nerve cell terminates on a specific target cell
  • wired for specific transmission to a target
  • neutrons can release neurohormones into the blood instead of neurotransmitters
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46
Q

Differences btwn endocrine and nervous system

A
  • neurotransmitters : rapid effects, are short lived
    neurons can stimulate only muscles and glands across a synapse
  • hormones : slow, longer lasting, diffuse in blood and can access most tissues and cells
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47
Q

Important feature of nervous system

A

NEURAL SPECIFICITY

- muscle movement depends on which neuron releases Ach

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48
Q

Endocrine glands

A
  • endocrine glands : synthesise and secrete hormones
    = “ductless glands” widely scattered in body
  • a few are made of neurosecretory tissue => neurons don’t always secreted chemical messengers across a synapse
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49
Q

Exocrine glands

A

= secrete product

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50
Q

Endocrine glands examples:

A
  • hypothalamus
  • anterior pituitary
  • posterior pituitary
  • pineal glad
  • thyroid gland
  • adrenal cortex
  • pancreas
  • gonads
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51
Q

Function of :

- hypothalamus

A

= MASTER gland

  • receives input
  • controls release of pituitary hormones through realising/inhibiting factors
52
Q

Function of :

- anterior pituitary

A
  • TSH (thyroid stimulating hormone)
  • ACTH (adrenocorticotropic hormone)
  • GH (growth hormone)
  • FSH (follicle-stimulating hormone) & LH (luteinizing hormone)
  • PRL (prolactin)
  • MSH (melanocyte stimulating hormone)
53
Q

Function of :

- posterior pituitary

A
  • vasopressin : antidiuretic hormone acts on kidneys

- oxytocin : milk let down and uterine contractions

54
Q

ACTH

A

= adrenocorticotropic hormone

stimulates cortisol secretion from adrenal cortex

55
Q

GH

A

= growth hormone

growth and metabolic effects

56
Q

FSH & LH

A

= follicle-stimulating hormone & luteinizing hormone

57
Q

FSH & LH

A

= follicle-stimulating hormone & luteinizing hormone

act on gonads, growth of follicles, ovulation

58
Q

PRL

A

= prolactin

milk synthesis from mammary glands

59
Q

Function of :

- pineal glands

A

produce melatonin

> controls biological (circadian rhythm)

60
Q

Function of :

- thyroid glands

A

produce T3, T4 & calcitonin to decrease plasma.
controls how quickly body burns energy, makes proteins
=> metabolism regulator

61
Q

Function of :

- adrenal cortex

A

produces :
- mineralocorticoids
> aldosterone -acts on kidney conserve sodium, retain water
- corticosteroids
> cortisol - increase BP and blood sugar, reduces immune response, anti-inflammatory
> androgens - DHEA (sex steroids)

62
Q

Function of :

- adrenal medulla

A

produces : epinephrine and norepinephrine

=> stress adaptation

63
Q

Function of :

- pancreas

A 
produces : 
- insulin
- glucagon 
- somatostatin 
=> nutrient levels and utilisation
64
Q

Function of :

- gonads

A

testies: produce testosterone

ovaries : produce estrogen & progesterone

65
Q

Iodine deficiency

A

-> swollen neck because iodine is not present
iodine is essential for production of T3
coq: physical growth and development problem, mental impairment

66
Q

T3 and T4 are primarily composed of

A

iodine

67
Q

Calcitonin

A

helps reduce calcium concentration in blood

68
Q

Grave’s disease

A
  • hyperthyroidism
  • immune system makes an antibody (TSI - thyroid stimulatory immunoglobulin) that attaches to thyroid cells. It acts like TSH and stimulates thyroid gland to produce T3 and T4.
69
Q

Classification of hormones

A
  • structure

- function

70
Q

Structural classification of hormones

A
  • HYDROPHILIC
    > peptide or protein hormones (insulin, catecholamines : epinephrine)
  • LIPOPHILIC
    > thyroid hormones and steroids (steroids are derived from cholesterol)
71
Q

Functional classification of hormones

A 
- TROPIC hormones 
   > target other endocrine glands and stimulate their growth and secretion of other hormones 
   > ACTH targets the adrenal cortex 
- SEX hormones 
   > target reproductive tissues 
- ANABOLIC hormones 
   > stimulate anabolism (build up) in target cells
   > testosterone
72
Q

Hormone __ determines the way it is transported in the blood, the means by which the endocrine cell processed it, the mechanism by which it effects signalling

A

solubility

73
Q

Are all hormones transported in the blood? The same way?

A

Yes in the blood

Not the same way

74
Q

Hydrophilic hormones

A

In plasma: are dissolved

Bind : to receptors on the surface of target cells

75
Q

Lipophilic hormones

A

In plasma : are bound to plasma proteins

Bind : pass through target cell membranes and bind to receptors inside the target cell

76
Q

Preprohormones

A

= hydrophilic peptide hormones precursors

  • made on ribosomes of ER
  • converted to prohoromones in Golgi -> active hormones
  • released by exocytosis
77
Q

Precursor for all steroid hormone -lipophilic (except thyroid hormones)

A

Cholesterol !

  • the precursor is stored
  • the lipid soluble hormone is not stored or excreted in urine
78
Q

From preprohormone to secreted hormone

A

Preprohormone (ribosome) -> prohormone (ER) -> Golgi -> release

79
Q

Precursor for thyroid amine hormones

A

Tyrosine

These hormones are stored until they are secreted

80
Q

Steroid hormone synthesis

A
  • synthesised from cholesterol
  • have a 4 ring steroid nucleus
  • Lipid soluble
  • pass through plasma membrane of target cells bind to nuclear receptors (at HRE - hormone response element) to initiate gene transcription
81
Q

Steroid hormones examples

A
  • cortisol, aldosterone (= adrenals)
  • estrogen (ovary & testis)
  • progesterone (ovary-CL)
  • testosterone (testis - Leydic cells)
82
Q

Non-steroid hormone synthesis

A
  • synthesised form amino acids
  • some are :
    > protein hormones
    > glycoprotein hormones
    > peptide hormones
    > amino acid derivative hormones
83
Q

Protein hormones

A

= long, folded chains of aa

ex: insulin

84
Q

Glycoprotein hormones

A

= protein hormones with CARBOHYDRATE groups attached to the aa chain
ex: hCG (human chorionic hormone-pregnancy recognition)

85
Q

Peptide hormones

A

= smaller than protein hormones, short chain of aa

ex: oxytocin, antidiuretic hormone (ADH)

86
Q

Amino acid derivative hormones

A

= derived from a single amino acid molecule
> amine hormones - modifying tyrosine, produced by neurosecretory cells and neurones
ex: epinephrine, norepinephrine (adrenal medulla)
> adding iodine to tyrosine
ex: thyroxine (T4)

87
Q

General principles of hormone action

A
  • bind to target cell’s specific receptor in a “lock & key” mechanism
  • hormone-receptor interaction produce different regulatory changes (inactivation of an enzyme, initiation of gene transcription)
88
Q

Combined hormone actions

A
  • synergism : combinations of hormones acting together to have a greater effect on a target cell than if acted alone
  • permissiveness : when small amount of 1 hormone permits or enables a second one to have its FULL effects on a target cell
  • antagonism : one hormone produces the opposite effects of another hormone
89
Q

Which hormones demonstrate “permissiveness”

A

thyroid hormones are always present when development

90
Q

Which hormones demonstrate “antagonism”

A

parathyroid hormone : increases blood calcium

calcitonin : thyroid decrease blood calcium

91
Q

Most hormones have :

  • primary effect ->
  • secondary effects ->
A

-> directly regulate target cells
-> influence or modulate other regulatory mechanisms in target cells
ex: prolactin
1° effect - stimulates mammary gland cells to transcribe milk proteins
2° effect - on immune cells

92
Q

Hormone actions must be __

A

terminated

  • they have a half-life
  • are degraded into inactive metabolites in the liver
93
Q

Where are steroid hormones’ receptors? Responses to steroid hormones are often __

A

In nucleus or cell’s cytosol.

SLOW

94
Q

What does sensitivity of target cells depend on

A

number of receptors

95
Q

up-regulation

A

increased number of hormone receptors

increases sensitivity-hormones often regulate own receptor levels

96
Q

down-regulation

A

decreased number of hormone receptors decreases sensitivity

97
Q

Mechanisms of hydrophilic-protein and peptide hormones

A
  • second messenger mechanism : produces target cell effects that differ from steroid hormone effects
    > effects of hormone are amplified by cascade of reactions
    > much faster than steroid mechanism
98
Q

Non steroid hormones usually operate in __

A

second messenger mechanism

  • hormone molecule = first messenger
  • delivers chemical message to fixed receptors on plasma membrane
  • message passed by G protein into cell, where second messenger triggers the appropriate cellular changes
99
Q

Examples of second messengers

A
  1. cAMP :
    adenylyl cyclase -> cAMP -> activates PKA -> induces protein to change shape
    ex: FSH
  2. calcium (still binding of G protein linked receptor)
    phospholipase C -> IP3 -> calcium -> calmodulin -> induces protein to change shape
    ex: oxytocin
100
Q

Regulation of hormone secretion

A

= negative feedback loop (reverses deviations from set points)
endocrine gland : sensitive to physiological changes or regulated by a hormone produced by another gland

101
Q

Humoral status can also regulate hormones

A

lactation > blood calcium concentration decreases > sensed by parathyroid > parathyroid increases secretion of parathyroid hormone (PTH) > PTH stimulates osteoclasts in bone to release more calcium from storage in bone tissue > increases maternal blood calcium concentration to the set point level

102
Q

Pituitary Gland

A
  • very small (1.2-1.5cm)
  • well protected
  • INFUNDIBULUM - connects pituitary to hypothalamus
  • made of 2 glands : anterior & posterior
103
Q

Anterior pituitary

A
  • 2 parts : pars anterior and pars intermedia
  • tissue composed of irregular clumps of secretory cells supported by fine connective tissue fibres and surrounded by a rich vascular network
  • makes growth hormone, adrenocorticotropic hormone, thyroid stimulating hormone, gonadotropic hormones, prolactin
104
Q

5 functional types of secretory cells in adenohypophysis

A 
1- somatotrophs : secrete GH 
2- corticotrophs : secrete ACTH and MSH 
3- thyrotrophs : secrete TSH
4- lactotrophs : secrete prolactin 
5- gonadotrophs : secrete LH and FSH
105
Q

GH - Growth hormone

A
  • promotes growth of bone, muscle, other tissues
    > by stimulating liver to produce growth factors that accelerates amino acids transport into cells
  • stimulates lipid metabolism
    > accelerates mobilisation of lipids from cells and speeds up lipid catabolism
    > hyperglycemic effect
106
Q

Hyperglycemic effect of GH

A

Insulin-growth factor (IGF) released from the liver in response to GH

  • increases BG
  • enhances lipid catabolism
  • promotes protein anabolism
107
Q

When does prolactin come?

A
  • during pregnancy : promotes development of breasts, anticipating milk secretion
  • after baby is born : stimulates mammary glands to produce milk
108
Q

Tropic hormones

A

= hormones that have a stimulating effect on other endocrine glands

109
Q

What are the 4 principal tropic hormones produced and secreted by basophils of the pars anterior ?

A
  1. thyroid stimulating hormone
  2. adrenocorticotropic hormone
  3. Follicle stimulating hormone
  4. Luteinizing hormone
110
Q

What happens to FSH levels at menopause?

A
  • rise of FSH, it stays high for the rest of life

it tries to grow a follicle but it can’t

111
Q

Hypothalamic regulatory hormones reach ant pituitary by a __

A

capillary-capillary connection = hypothalamic hypophyseal portal system

112
Q

From hypothalamus to anterior pituitary gland

A

Hypothalamus > secretes releasing hormones into blood > carried to hypophyseal portal system > anterior pituitary gland

113
Q

Hormones released by hypothalamus

A

(RH: releasing hormone - IH : inhibiting hormone)

  • GHRH - growth hormone RH
  • GnRH - Gonadotropin RH
  • CRH - Corticotropin RH
  • TRH - Thyrotropin RH
  • PRH - Prolactin RH
  • PIH - Prolactin IH
  • GHIH - Growth hormone IH
114
Q

__ carries blood from hypothalamus directly to adenohypophysis where target cells of releasing hormones are located

A

hypophyseal portal system

115
Q

Anterior pituitary =

Posterior pituitary =

A

= adenohypophysis

= neurohypophysis

116
Q

What is the relationship between hypothalamus and posterior pituitary ?

A

hypothalamus : has neurosecretory cells’ body

posterior pituitary : has neurosecretory cells’ axon terminals

117
Q

What does the posterior pituitary release? (2)

A
  • OXYTOCIN

- VASOPRESSIN (ADH - antidiuretic hormone)

118
Q

Hormone pathologies occur when

A
  • hormone excess
  • hormone deficiency
  • abnormal responsiveness of target tissues
119
Q

Hormone excess

A

ex: hypercortisol secretion = Cushing’s disease
cause = tumour of adrenal gland secreting cortisol or tumour secreting acth -> stimulates excessive secretion of cortisol
symptoms = breakdown of muscle proteins, redistribution of body fat, red and round face

120
Q

Hormone deficiency

A

ex: hypothyroid secretion
causes = iodine deficiency, stress
symptoms = swelling of facial tissues, low body temp, sensitivity to cold, dry skin and hair, slow heart rate

121
Q

Abnormal responsiveness of target tissues

A

ex: type 2 diabetes mellitus (loss of tissue sensitivity to insulin)
causes = obesity
symptoms = high blood glucose, weight loss, excessive thirst, frequent urination

122
Q

Type 1 diabetes mellitus :

Type 2 diabetes mellitus :

A

1: loss of insulin production
2: loss of tissue sensitivity to insulin

123
Q

Neuroendocrine system adjusts

A

nutrient supply

124
Q

Calcitonin , parathyroid hormone, vitamin D balance __

A

calcium ion use

125
Q

Nervous system and hormones regulate _

A

Reproduction

Mammalian Physiology (6 decks)

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