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3) Mammalian Physiology > Set 3 (Part I) > Flashcards

Set 3 (Part I) Flashcards

1
Q

What are electrical signals?

A
  • Involve changes in membrane potential

- Mostly seen in nervous system

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2
Q

What are chemical signals?

A
  • Molecules secreted by cells into EF
  • Responsible for most communication within the body
  • Mostly seen in endocrine system
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3
Q

What are the four basic methods of cell-to-cell communication?

A
  1. Gap junctions
  2. Contact-dependent signals
  3. Chemicals that diffuse through EF
  4. Long-distance communication
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4
Q

What do gap junctions allow?

A

Direct cytoplasmic transfer of electrical and chemical signals between adjacent cells

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5
Q

When do contact-dependent signals occur?

A

When surface molecules on one cell membrane bind to surface molecules on another

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6
Q

What do chemicals that diffuse through EF act on?

A

Cells that are close by

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7
Q

What does long-distance communication use?

A
  • Uses a combination of chemical signals transported by the blood
  • Relies on the presence or absence of a receptor
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8
Q

What is the simplest form of cell-to-cell communication?

A

Gap junctions

- Direct transfer of electrical and chemical signals by creating cytoplasmic bridges

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9
Q

What forms a union of membrane-spanning proteins? What are they called?

A
  • Gap junctions

- Connexins

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10
Q

When open ions, amino acids, ATP, cAMP diffuse directly from one cytoplasm of one cell to the cytoplasm of the next, this is called _________.

A

gap junction

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11
Q

What can’t pass through gap junctions?

A

Larger molecules

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12
Q

What is the only means by which electrical signals can pass directly?

A

Gap junctions

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13
Q

What does contact-dependent signaling require?

A

Requires that surface molecules on one cell membrane bind to a membrane protein of another

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14
Q

Where do contact-dependent signals occur?

A

Occurs in the immune system and during growth/development

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15
Q

Which cell-to-cell communication includes cell-adhesion molecules?

A

Contact-dependent signaling

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16
Q

In what direction do CAMs and integrins transfer signals?

A

In both directions

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17
Q

What are paracrine and autocrine signals?

A

Chemical signals

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18
Q

Define autocrine signals.

A
  • Chemical signal

- Act on the same cell that secreted them

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19
Q

Define paracrine signals.

A
  • Chemical signal

- Secreted by one cell and diffuse to adjacent cells

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20
Q

What is responsible for long-distance communication?

A
  • Hormones secreted by endocrine glands or cells into the blood
  • Target cells with receptors
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21
Q

What are neurotransmitters?

A

Chemicals secreted by neurons that diffuse across a small gap to the target cell

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22
Q

What two types of signaling do neurons use

A
  • Electrical (action potential)

- Chemical (neurotransmitter)

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23
Q

What are neurohormones?

A

Chemicals released by neurons into the blood for action at distant targets

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24
Q

What kind of signals may cytokines carry-out?

A
  • Local

- Long-distance

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25
Q

What are cytokines synthesized by? What aren’t they synthesized by?

A
  • Synthesized and secreted by all nucleated cells

- Not produced by specialized cells

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26
Q

What do cytokines control?

A
  • Cell development
  • Differentiation
  • Immune responses
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27
Q

How do cytokines differ from hormones?

A
  • Cytokines act on a broader spectrum of target cells than hormones
  • Cytokines are made on demand (not stored)
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28
Q

Explain the four steps of signal pathways utilized by paracrine/autocrine molecules and hormones.

A
  1. Signal molecule binds to receptor protein
  2. Receptor protein activates intracellular signal molecules
  3. Intracellular signal molecules alter target proteins
  4. Target proteins create a response
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29
Q

Where are receptor proteins located?

A
  • Inside the cell

- On the cell membrane

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30
Q

What is the location of ligand/receptor binding dependent on?

A

Whether a signal molecule is lipophilic or hydrophilic

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31
Q

Where can lipophilic signal molecules diffuse?

A
  • Through the phospholipid bilayer

- Binding to cytoplasmic or nuclear receptors

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32
Q

Where do lipophobic signal molecules bind?

A
  • Cannot diffuse through plasma membrane

- Bind to extracellular receptors (on membrane)

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33
Q

Differentiate the outcomes of lipophilic and lipophobic signal molecules.

A
  • Lipophilic: receptor activation often turns on or off a gene; relatively slow
  • Lipophobic: causes a cascade of events to occur; very rapid
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34
Q

Where can lipophilic molecules bind?

A
  • To the membrane

- Intracellular receptors

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35
Q

What three consequences may secondary messengers cause?

A
  1. Alter gating of ion channels
  2. Increase intracellular calcium (which bind to proteins to change their function)
  3. Change enzyme activity, especially of protein kinases and protein phosphatases
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36
Q

Explain the mechanism of the insulin receptor involving a tyrosine kinase.

A
  1. Insulin binds to receptor on the surface.
  2. Activation of tyrosine kinase on the cytoplasmic side
  3. TK transfers a phosphate group from ATP to a tyrosine of a protein
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37
Q

What do most signal transductions use?

A

G proteins

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38
Q

What are G proteins?

A
  • Bind nucleotide guanosine

- Large and complex family of membrane-spanning proteins that cross the bilayer 7 times

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39
Q

What happens when G proteins are activated?

A
  • Open ion channels in the membrane

- Alter enzyme activity on the cytoplasmic side of the membrane

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40
Q

Explain the mechanism of the GPCR Adenylyl-Cyclase-cAMP signal transduction pathway.

A
  1. Ligand binds to G protein receptor
  2. G protein turns on adenylyl cyclase
  3. Adenylyl cyclase converts ATP to cAMP
  4. cAMP activates PKA
  5. PKA phosphoryaltes other proteins
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41
Q

Explain the mechanism of the GPCR Phospholipase C system.

A
  1. Ligand binds to G protein
  2. G protein activates phospholipase C (PL-C)
  3. PL-C converts membrane phospholipids into diacylglycerl (membrane) and IP3 (cytoplasm)
  4. DAG activates protein kinase C
  5. IP3 causes release of Ca2+ from organelles
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42
Q

Explain the mechanism of a receptor ion channel.

A
  1. Receptor-channels open or close in response to signal binding
  2. Some channels are linked to G proteins
  3. Other respond to intracellular second messengers
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43
Q

Which signal pathway initiates the most rapid response?

A

Receptor ion channel

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44
Q

How does calcium enter the cell?

A
  • Voltage gated calcium channels

- Ligand or mechanically gated

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45
Q

What is an agonist?

A

An agonist activates a receptor

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46
Q

What is an antagonist?

A

Blocks receptor activity

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47
Q

Which two systems function to achieve and maintain homeostasis?

A
  • Nervous (fast-acting)

- Endocrine (slow-acting)

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48
Q

When the nervous and endocrine systems work together, they are referred to as the ______________.

A

neuroendocrine sytem

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49
Q

What are the differences between the nervous and endocrine systems in terms of anatomy?

A
  • Nervous: each nerve cell terminates on a specific target cell
  • Endocrine: endocrine glands are not linked with their target cell (wireless); the messengers are secreted into blood
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50
Q

Differentiate the nervous and endocrine systems in terms of what they can affect.

A
  • Nervous: rapid, short-lived

- Endocrine: slow, long-lasting

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51
Q

Differentiate the nervous and endocrine systems in terms of what they stimulate.

A
  • Endocrine: can access most tissues and cells

- Neurons: only stimulate muscles and glands across a synapse

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52
Q

What is neural specificity due to?

A
  • Anatomic proximity between the nerve cell and target tissues
  • Which muscle moves depends on which neuron releases acetylcholine as all motor neurons have Ach receptors
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53
Q

Differentiate endocrine and exocrine glands.

A
  • Endocrine: secretes hormones in interstitial space and gets picked up by blood
  • Exocrine: secretes products that end up outside of the body, passes through a duct
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54
Q

Describe the function of the endocrine glands that are made of neurosecretory tissue. Give an example.

A
  • Modified neurons that secrete chemical messengers that diffuse in the bloodstream rather than across a synapse
  • Adrenal medulla
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55
Q

What is the function of the hypothalamus?

A
  • Master gland
  • Receives input and acts accordingly
  • Controls the release of anterior pituitary hormones through releasing and inhibiting factors
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56
Q

What does the hypothalamus control?

A

Anterior pituitary

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57
Q

What seven products are secreted by the anterior pituitary?

A
  1. TSH
  2. ACTH
  3. GH
  4. FSH
  5. LH
  6. PRL
  7. MSH
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58
Q

What is the function of thyroid-stimulating hormone (TSH)?

A
  • Stimulates thyroid cells to produce T4 and T3
  • Brain development
  • Metabolism
  • Reproduction
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59
Q

What is the function of adrenocorticotropic hormone (ACTH)?

A

Stimulates cortisol secretion from adrenal cortex

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60
Q

What is the function of growth hormone (GH)?

A

Growth and metabolic effects

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61
Q

What is the function of follicle-stimulating hormone (FSH)?

A
  • Acts on gonads
  • Women: growth of follicles
  • Males: androgen-binding expression by Sertoli cells (spermatogenesis)
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62
Q

What is the function of luteinizing hormone (LH)?

A
  • FSH triggers the production of estrogen
  • Rise in estrogen decreases FSH, and increases LH
  • LH causes the egg to be released from the ovary (ovulation)
  • In males: testosterone production
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63
Q

What is the function of prolactin (PRL)?

A

Milk synthesis from mammary glands

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64
Q

What is the function of melanocyte-stimulating hormone?

A
  • Melanocytes give skin its pigment

- Only active during development and pregnancy

65
Q

What are the two hormones released by the posterior pituitary?

A
  • Vasopressin (antidiuretic hormone)

- Oxytocin

66
Q

What is oxytocin responsible for?

A
  • Milk let down

- Uterine contractions

67
Q

What does the pineal gland produce? What is it responsible for?

A
  • Melatonin

- Controls biological (circadian) rhythm

68
Q

What does the thyroid gland secrete? What are their overall functions?

A
  • T3
  • T4
  • Calcitonin
  • Controls how quickly the body burns energy and makes proteins (metabolism regulator)
69
Q

What is the function of calcitonin?

A

Secreted if blood calcium is high; makes the system utilize calcium for bone production

70
Q

What does the adrenal cortex secrete?

A
  • Mineralocorticoids

- Aldosterone, corticosteroids, androgens

71
Q

What is the function of aldosterone? What is it secreted by?

A
  • Acts on the kidney to cause conservation of sodium and overall retention of water
  • Adrenal cortex
72
Q

What is the function of corticosteroids? What is it secreted by?

A
  • Increases BP and blood sugar

- Reduces immune responses (anti-inflammatory)

73
Q

What does the adrenal medulla secrete? What is their function?

A
  • Epinephrine and norepinephrine

- Stress adaptation

74
Q

What does the pancreas secrete? What is their function?

A
  • Insulin, glucagon, somatostatin

- Nutrient levels and utilization

75
Q

What do the gonads secrete?

A
  • Testes: testosterone

- Ovaries: estrogen and progesterone

76
Q

What is T4?

A
  • Thyroxine

- Tetraiodothyronine

77
Q

What is T3?

A

Triiodothyronine

78
Q

Explain the onset of goiter.

A
  • Results from iodine deficiency, which is essential in the production of the thyroid hormones
  • The thyroid gland panics during deficiency and starts producing more cells (hyperplasia), which results in a big mass on the neck
79
Q

What are the consequences of children with thyroid hormone deficiency?

A
  • Physical growth and development problems

- Brain development can be severely impaired (cretinism)

80
Q

What is the most common form of hyperthyroidism?

A

Grave’s disease

81
Q

What is Grave’s disease?

A
  • An immune system protein mimics thyroid stimulating hormone (autoimmune)
  • Immunoglobulins are binding to the thyroid gland, which is perpetually stimulated
  • Results in hyperthyroidism, and sometimes in an enlarged tumor
82
Q

What are the signs and symptoms of Grave’s disease?

A
  • Sweating
  • Headache
  • Weight loss
  • Nausea and diarrhea
  • Irritability
  • Muscle weakness
  • Sleeping problems
  • Fast heartbeat
  • Goiter (sometimes)
83
Q

How is Grave’s disease treated?

A

Radioactive iodine to destroy thyroid cells

84
Q

What are hydrophilic hormones? Give examples.

A
  • Water soluble (usually peptide or protein hormones)

- Insulin, epinephrine

85
Q

What are lipophilic hormones? What do they include?

A
  • High lipid solubility, poorly soluble in water

- Thyroid hormones and steroids

86
Q

What are steroids?

A

All steroids are derived from cholesterol

87
Q

What are thyroid hormones made of?

A

Iodinated tyrosine (AA) derivative

88
Q

What are tropic hormones?

A

Targets other endocrine glands and stimulate their growth/secretion of other hormones

89
Q

What do sex hormones target?

A

Reproductive tissues

90
Q

What do anabolic hormones do?

A
  • Stimulate anabolism (to build) in target cells

- Ex: testosterone stimulates protein synthesis and build up of cellular tissue

91
Q

What do the solubility properties of a hormone determine?

A
  1. The way the hormone is transported in the blood
  2. The mechanism by which the hormone exerts its effect (signaling)
  3. The means by which the hormone is processed by the endocrine cell
92
Q

How are hydrophilic hormones transported in the blood?

A

Dissolved in the plasma

93
Q

How are lipophilic hormones transported in the blood?

A
  • Bound reversibly to plasma proteins

- Hormones are released by these proteins when they actively signal target cells

94
Q

How do hormones generally produce their effects?

A
  • Altering intracellular proteins (signal transduction)
  • Hydrophilic hormones: receptors on surface
  • Lipophilic: hormones pass through cell membranes
95
Q

What are the precursors of hydrophilic peptide hormones?

A

Preprohormones

96
Q

How are preprohormones made?

A
  • Made on ribosomes in the ER
  • Converted to prohormones in the Golgi, and then to active hormones
  • Golgi concentrates the hormone into secretory vesicles
  • Released by exocytosis
97
Q

What is the precursor to lipophilic hormones?

A

Cholesterol for steroid hormones (exception is thyroid hormone)

98
Q

How are steroid hormones made from cholesterol?

A
  • Enzymatic steps modify cholesterol into a different hormone
  • Only the precursor (cholesterol) is stored
99
Q

How are lipophilic hormones stored?

A
  • They are NOT stored

- Metabolized by the liver or excreted in urine

100
Q

Which lipophilic hormone is stored?

A

Thyroid amine hormones

101
Q

How are steroid hormones similar in terms of structure?

A

They all have a four-ring steroid nucleus at their core

102
Q

How can lipid-soluble hormones initiate gene transcription?

A
  • Bind to nuclear receptor, which usually has a zinc finger DNA binding domain
  • Bind at the hormone response elements (HRE)
103
Q

Which steroid hormones are synthesized in the adrenal cortex? Which is synthesized in the ovary?

A
  • Adrenal cortex: aldosterone, cortisol

- Ovary: estrogen

104
Q

What are non-steroid hormones synthesized from?

A
  • Synthesized from amino acids

- Protein hormones or glycoprotein hormones

105
Q

Human chorionic hormone-pregnancy recognition (hCG) hormone is an example of what?

A

Glycoprotein hormone

106
Q

Oxytocin and ADH are examples of what?

A

Peptide hormones

107
Q

How are amine hormones synthesized? What are they produced by?

A
  • Synthesized by modifying a single molecule of tyrosine

- Produced by neurosecretory cells and by neurons, or the thyroid gland

108
Q

Epinephrine, norepinephrine, T3 and T4 hormones are examples of what?

A

Amine hormones (from tyrosine)

109
Q

How do hormones signal a cell?

A
  • Binding to the target cell’s specific receptors (lock and key)
  • Different hormone-receptor interactions produce different regulatory changes
110
Q

What different regulatory changes can a hormone produce?

A
  • Inactivation of an enzyme

- Initiation of gene transcription

111
Q

What is synergism?

A

Combinations of hormones acting together have a greater effect on a target cell than the sum of the effects that each would have if acting alone

112
Q

FSH and estrogen acting on granulosa cells is an example of what?

A

Synergism

113
Q

What is permissiveness?

A

When a small amount of one hormone permits, or enables, a second one to have its full effects on a target cell

114
Q

What is antagonism?

A

One hormone produces the opposite effects of another hormone

115
Q

Parathyroid hormone and calcitonin are an example of what?

A

Antagonism

116
Q

Hormone actions must be ________.

A

terminated

117
Q

How are hormone actions terminated?

A

Hormones have a half-life and are degraded into inactive metabolites in the liver, which are then excreted

118
Q

What are the effects of extended actions of insulin?

A
  • Deprives the brain of glucose
  • Neurons are insulin independent, but muscle and fat are dependent
  • The glucose would go to muscle/fat, and the brain would be deprived
119
Q

Describe the mobile-receptor model.

A
  1. Hormone passes in the nucleus, where it binds to a mobile receptor and activates a certain gene sequence
  2. Transcription of mRNA, which moves to the cytosol and associates with ribosomes
  3. Synthesis of protein molecules that produce the effect of the hormone
120
Q

How do steroid hormones regulate cells? What determines the magnitude of a target cell’s response?

A
  • Regulating production of certain critical proteins

- The amount of steroid hormone present

121
Q

Why are responses to steroid hormones slow?

A

Because transcription and protein synthesis take time

122
Q

What does target cell sensitivity depend on?

A
  • In part, on the number of receptors that the cell has

- Receptors are constantly being broken down and replaced

123
Q

Differentiate up-regulation and down-regulation.

A
  • Up-regulation: increased number of hormone receptors; increases sensitivity
  • Down-regulation: decreased number of hormone receptors
124
Q

How does the secondary messenger mechanism differ from steroid hormone effects?

A
  1. Effects of the hormone are amplified by the cascade of reactions
  2. Second messenger mechanism operates much more quickly than the steroid
125
Q

How do non-steroid hormones usually operate?

A

Second messenger mechanism, in which the non-steroid hormone acts as the first messenger

126
Q

Describe the mechanism of action of non-steroid hormones.

A
  1. Non-steroid hormone binds to the receptor.
  2. Activation of a G, protein
  3. Alpha subunit shuttles and activates adenylyl cyclase
  4. Adenylyl cyclase converts ATP to cAMP
  5. cAMP acts as a secondary messenger and activates PKA, which phosphorylates proteins
127
Q

What are the four categories of membrane receptors?

A
  • Receptor-channel
  • Receptor-enzyme
  • G protein coupled-receptor
  • Integrin receptor
128
Q

What activity do receptor-enzymes have?

A
  • Tyrosine kinase

- Guanylyl cyclase

129
Q

What is the amplifyer enzyme in GPCR-cAMP?

A

Adenylyl cyclase

130
Q

What receptor transfers information from the extracellular matrix?

A

Integrins

131
Q

What do the most rapid signal pathways change? What does that create?

A
  • Change ion flow through channels

- Creates an electrical signal that alters voltage-sensitive proteins

132
Q

What is the difference between a first messenger and a second messenger?

A
  • First messengers are extracellular

- Second messengers are intracellular

133
Q

Where is most intracellular calcium stored?

A

In the endoplasmic reticulum

134
Q

Which gas is known to relax blood vessels?

A

Nitric oxide (NO)

135
Q

How can one chemical have opposite effects if a different tissue?

A

Receptors, like other proteins, may come as families of related isoforms

136
Q

What are two methods to down-regulate cell receptors?

A
  • Endocytosis

- Desensitization

137
Q

How can cells terminate signal pathways?

A
  • Ligand can be degraded by enzymes in the EC
  • Transport of ligand into neighboring cells
  • Endocytosis of the receptor-ligand complex
138
Q

What are the three ways hormones act on their target cells?

A
  1. Controlling rates of enzymatic reactions
  2. Controlling transport of ions of molecules across membranes
  3. Controlling gene expression and synthesis of proteins
139
Q

Name the membrane transport process by which glucose moves from the extracellular fluid into cells.

A

Facilitated diffusion (GLUT transporter)

140
Q

Where are prohormones contained? In what compartment of the cell? When are they released?

A
  • Contained in secretory vesicles
  • In the cytoplasm
  • Release their contents by calcium-dependent exocytosis
141
Q

Which cellular organelles do cells that secrete steroid hormones possess?

A

Lots of smooth ER

142
Q

Where are most steroid hormones made?

A
  • Adrenal cortex

- Gonads

143
Q

Do peptide or steroid hormones have an extended half-life?

A

Steroid hormones since they are bound to carrier proteins, which protect them

144
Q

The steroid hormone aldosterone has a short half-life for a steroid hormone—only about 20 minutes. What would you predict about the degree to which aldosterone is bound to blood proteins?

A

The short half-life suggests that aldosterone is not bound to plasma proteins as much as other steroid hormones are.

145
Q

Is it possible for steroid hormones to cause non-genomic effects?

A

Yes, in recent years, steroid hormones have been discovered to contain membrane receptors linked to signal transduction pathways

146
Q

Which amino acids create hormones?

A

Tyrosine or tryptophan

147
Q

What is melatonin derived from?

A

Tryptophan

148
Q

What are the catecholamines?

A
  • Epinephrine
  • Norepinephrine
  • Dopamine
149
Q

What do catecholamines behave like?

A

Neurohormones that behave like peptide hormones

150
Q

What is the sensor in the simplest endocrine reflexes?

A
  • The endocrine cell (directly sense a stimulus, and respond by secreting its hormone)
  • Response usually serves as a negative feedback
151
Q

Which two endocrine structures are incorporated into the anatomy of the brain?

A
  • Pineal gland

- Pituitary gland

152
Q

What are the three major groups of neurohormones? What are they secreted by?

A
  1. Catecholamines (adrenal medulla)
  2. Hypothalamic neurohormones (posterior pituitary)
  3. Hypothalamic neurohormones that control hormone release from the anterior pituitary
153
Q

Which pituitary gland is a true endocrine gland? Which is an extension of the neural tissue of the brain?

A
  • Anterior pituitary: true endocrine

- Posterior pituitary: extension of neural tissue

154
Q

Which gland secretes mainly trophic hormones? Which hormone is the exception?

A
  • Anterior pituitary

- Except prolactin

155
Q

What is the function of the hypothalamic-hypophyseal portal system?

A

Delivering hypothalamic releasing and inhibiting hormones from the hypothalamus to the anterior pituitary

156
Q

What is the advantage of hormones secreted into a portal system?

A

A much smaller amount of hormone can be secreted to elicit a given level of response

157
Q

How are feedback loops different in the hypothalamic-pituitary pathway?

A
  • Involve three integrating centers: hypothalamus, anterior pituitary and the endocrine target tissue
  • Instead of the response acting as the negative feedback signal, the hormones themselves are the feedback signal
  • The downstream hormones usually feed back to suppress the hormone(s) that controlled its secretion
158
Q

Differentiate long-loop feedback and short-loop feedback.

A
  • Long-loop feedback: the last hormone in a pathway feeds back to suppress secretion of its trophic hormones
  • Short-loop feedback: pituitary hormones feed back to decrease hormone secretion by the hypothalamus
159
Q

What is functional antagonism?

A

Two hormones having opposing physiological actions

3) Mammalian Physiology (24 decks)

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