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Week 5 Flashcards

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1
Q

What is the endocrine system?

A

A collection of glands and organs

Releases hormones into the circulatory system

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2
Q

What functions does the endocrine system regulate?

A

Digestion

Metabolism

Sleep–wake cycles

Development

Growth

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3
Q

How do endocrine glands work?

A

Trigger a specific physiological effect

Provide feedback to regulate gland activity

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4
Q

How do endocrine organs interact?

A

Some communicate by acting on other endocrine organs

Others act alone without neural or endocrine input

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5
Q

What are the three major components of the endocrine system?

A

Glands

Hormones

Receptors

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6
Q

What are glands?

A

Specialised cell clusters or organs

Produce and secrete hormones

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7
Q

What are hormones?

A

Chemical substances

Secreted by glands into the circulatory system

Released in response to stimulation

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8
Q

What are receptors?

A

Protein molecules

Bind with hormones

Trigger specific physiological changes in target cells

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9
Q

What is the main function of the hypothalamus?

A

Controls homeostasis (balance & stability), influences the autonomic nervous system, and releases hormones.

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10
Q

What physiological functions does the hypothalamus regulate?

A

Growth, development, and metabolism.

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11
Q

How does the hypothalamus control other glands?

A

It regulates hormone secretion and controls the pituitary gland.

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12
Q

How does the nervous system control bodily functions?

A

It uses electrochemical impulses via neurons, causing rapid responses within milliseconds.

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13
Q

How does the endocrine system control bodily functions?

A

It uses hormones (chemical messengers) that travel through the blood to regulate metabolic activity.

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14
Q

How do the response times of the nervous and endocrine systems differ?

A

The nervous system acts quickly (milliseconds), while the endocrine system has a lag period but longer-lasting effects.

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15
Q

How does the nervous system act on the body?

A

It sends fast electrochemical impulses via neurons to specific locations along axon pathways.

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16
Q

How quickly does the nervous system initiate a response?

A

Almost immediately—within milliseconds.

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17
Q

How long do nervous system responses last?

A

They are short in duration.

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18
Q

How does the endocrine system act on the body?

A

It releases hormones into the blood, which travel long distances to target organs.

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19
Q

How quickly does the endocrine system initiate a response?

A

It has a lag period—responses take seconds to days to start.

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20
Q

How long do endocrine system responses last?

A

They are prolonged and long-lasting.

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21
Q

Do all hormones affect all tissues in the body?

A

No, hormones only influence specific target cells that have the right receptor.

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22
Q

What determines whether a cell is a target cell for a hormone?

A

The presence of a specific receptor for that hormone.

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23
Q

What happens if a cell lacks the correct hormone receptor?

A

It will not respond to that hormone.

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24
Q

How do hormones affect target cells?

A

They alter cell activity by increasing or decreasing the rates of normal cellular processes.

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25
Does a hormone always have the same effect on all target cells?
No, the response depends on the target cell type.
26
How does adrenaline affect smooth muscle cells in blood vessel walls?
It stimulates them to contract.
27
Can adrenaline cause different effects in different cells?
Yes, it can have entirely different effects depending on the target cell.
28
What are the three major types of stimuli for hormone release?
Humoral, neural, and hormonal stimuli.
29
What triggers hormone release in humoral stimuli?
Changes in ion or nutrient levels in the blood.
30
How does the parathyroid gland respond to low blood calcium levels?
It releases parathyroid hormone (PTH), which increases blood calcium.
31
What happens when blood calcium levels are high?
The release of parathyroid hormone (PTH) is inhibited.
32
How does the central nervous system (CNS) regulate hormone secretion?
It controls certain endocrine glands, such as the hypothalamus and adrenal medulla.
33
How does the hypothalamus control the pituitary gland?
Hypothalamic nerve cells stimulate the posterior pituitary to release ADH and oxytocin.
34
What factors influence ADH secretion?
Hypoxia (low oxygen), nausea, pain, stress, and certain drugs.
35
How does the CNS control adrenaline release?
The sympathetic nervous system stimulates the adrenal medulla, increasing adrenaline and noradrenaline levels.
36
What is hormonal stimuli?
The release of hormones in response to hormones from other endocrine organs.
37
How does the hypothalamus influence the anterior pituitary?
Peptide hormones from the hypothalamus travel through the portal system to stimulate the anterior pituitary to release hormones.
38
How do anterior pituitary hormones affect other endocrine organs?
They stimulate other glands to release their own hormones.
39
What is the role of negative feedback in hormonal stimuli?
As hormone levels from the target gland rise, they inhibit anterior pituitary hormone release, preventing overproduction.
40
What is the role of transport proteins in hormone circulation?
They bind to lipid-soluble hormones, helping them circulate in the blood, act as reservoirs, and protect hormones from degradation.
41
What is the biological half-life of a hormone?
The time it takes for half of a hormone's concentration to degrade or be removed from the bloodstream.
42
How does receptor number and affinity affect hormone action?
More receptors increase sensitivity, and higher affinity strengthens the hormone-receptor interaction, enhancing the effect.
43
What is a permissive hormone effect?
When one hormone enhances the responsiveness or activity of another hormone (e.g., oestrogen increases progesterone receptor formation in the uterus).
44
What are antagonistic hormones?
Hormones that have opposite effects to maintain homeostasis, such as insulin (lowers blood glucose) and glucagon (raises blood glucose).
45
What is a synergistic hormone effect?
When two or more hormones work together to amplify their effects (e.g., epinephrine and norepinephrine increase heart rate).
46
What are the two main classes of hormones based on chemical structure?
Amino acid-based hormones (proteins, peptides, amines) and steroid hormones (derived from cholesterol).
47
What are amino acid-based hormones made from?
Chains of amino acids, ranging from a single tyrosine molecule to proteins with more than 20 amino acids.
48
Why are amino acid-based hormones water-soluble?
Because they are made of amino acids, which dissolve in water and can be transported in the blood plasma.
49
How do amino acid-based hormones interact with target cells?
They bind to receptor proteins embedded in the cell membrane since they cannot pass through the lipid membrane.
50
What are steroid hormones derived from?
Cholesterol, through a series of chemical modifications.
51
Why do steroid hormones require transport proteins in the blood?
They are lipid-soluble, so they must bind to specific carriers (e.g., androgen-binding protein) or general plasma proteins (e.g., albumin) for transport.
52
How do steroid hormones enter target cells?
They diffuse directly through the plasma membrane and bind to receptors in the cytoplasm or nucleus.
53
How do steroid hormones travel in the bloodstream?
They bind to transport proteins (specific carriers or albumin) to circulate in the blood.
54
How does a steroid hormone find its target cell?
It circulates in the bloodstream until it reaches a cell with the specific intracellular receptor.
55
How do steroid hormones enter a target cell?
They are lipid-soluble, so they diffuse directly through the plasma membrane.
56
What happens when a steroid hormone binds to its receptor?
The receptor changes shape, releasing a chaperone molecule, which activates the receptor.
57
Where does the hormone-receptor complex go, and what does it do?
It moves into the nucleus and binds to a hormone response element (HRE) on DNA, activating specific genes.
58
How does a steroid hormone cause a cellular response?
Gene activation leads to mRNA transcription, which is translated into proteins (often enzymes) that trigger the cell’s response.
59
What happens once an amino acid-based hormone is secreted into the bloodstream?
The hormone circulates through the body, dissolved in plasma or bound to proteins. It moves until it reaches a target cell with the specific receptor for that hormone. Despite circulating throughout the body, a hormone affects only cells with the matching receptor.
60
What happens when an amino acid-based hormone reaches its target cell?
The hormone binds to a specific receptor on the cell membrane. This binding initiates a cascade of events leading to a cellular response.
61
Why do amino acid-based hormones bind to receptors on the cell membrane?
Amino acid-based hormones are water-soluble and lipid-insoluble. They cannot pass through the lipid bilayer of the cell membrane. Therefore, they must bind to receptors embedded in the plasma membrane.
62
What happens when the hormone binds to the receptor?
The receptor changes shape and displaces guanosine diphosphate (GDP). GDP is then converted into guanosine triphosphate (GTP), a high-energy molecule. The receptor is now activated.
63
What is the role of GTP in hormone signaling?
The activated receptor binds to a G protein and exchanges GDP for GTP. This activates the G protein, which plays a key role in the next step.
64
What does the activated G protein do?
The activated G protein binds to and activates an enzyme called adenylate cyclase. Adenylate cyclase converts ATP into cyclic AMP (cAMP).
65
How does cAMP influence the cell?
cAMP acts as a second messenger within the cell. It activates intracellular enzymes that either inhibit or activate many proteins. This results in the cellular response to the hormone.
66
How does the hypothalamus control the release of hormones from the anterior pituitary?
The hypothalamus secretes releasing and inhibiting hormones into the hypophyseal portal system. These hormones travel to the anterior pituitary, where they stimulate or inhibit the release of hormones. The anterior pituitary hormones are then distributed throughout the body.
67
How does the hypothalamus control the release of hormones from the posterior pituitary?
Oxytocin and ADH are produced by hypothalamic neurons and transported along nerve axons to the posterior pituitary. They are stored in axon terminals and released when the neurons fire. These hormones are then distributed through a capillary bed in the posterior pituitary.
68
How does the hypothalamus regulate thyroid hormone levels?
When thyroid hormone levels are low, the hypothalamus releases thyrotrophin releasing hormone (TRH), which stimulates the anterior pituitary to release thyroid stimulating hormone (TSH). TSH signals the thyroid to produce more hormones. As thyroid hormone levels rise, they feedback to decrease TRH and TSH production, maintaining balance.

DEN1DSA (10 decks)

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