Chemical Messenger Flashcards
1
Q
What is homeostasis ?
A
the maintenance of constant internal environment to enable cells to function at an optimum level
2
Q
Homeostasis is achieved by the actions of:
A
- The Endocrine System:
by the release of chemical messenger (hormones) - The Nervous System:
by the transmission of nerve impulses to and from various part of the body
3
Q
What are the exocrine glands?
A
Secrete into a duct that carries the secretion to the body surface or to one of the body cavities.
4
Q
What are the examples of exocrine glands?
A
sweat glands, mucous glands, salivary glands and glands of the alimentary canal
5
Q
What the function of endocrine glands?
A
- Secrete hormones into the extracellular fluids
- The secretion usually passes into the capillaries to be transported by the blood
- Endocrine glands are ductless glands
6
Q
What are the examples of endocrine glands?
A
- Pituitary (anterior and posterior)
- Thyroid
- Adrenal
- Pineal
- Parathyroid
- Thymus
- Pancreas
- Gonads (Testes and Ovaries)
7
Q
How are hormones produced?
A
by endocrine glands
8
Q
How do hormones transport ?
A
throughout the body by the blood
9
Q
Who is affected by the hormones?
A
A hormone affects only particular groups of cells (target cells) or target organs that have the specific and complementary receptor for the hormone.
10
Q
What will happen once all the receptor molecules are occupied by hormone molecules?
A
the addition of more hormones does not produce any greater effect (saturated).
11
Q
What are hormones?
A
Any secretion from an endocrine gland
- May be proteins, steroids or amines
12
Q
Characteristics of hormones
A
Hormones are NOT enzymes, but hormones may change the type, activity and quantity of enzymes/proteins
13
Q
Roles of hormones
A
- activate certain genes in the nucleus so that a particular enzyme or protein is produced
- change the shape of an enzyme so that it is activated or inactivated
- change the rate of production of an enzyme
14
Q
What is enzyme amplification ?
A
- One hormone activates thousands of enzyme molecules.
* A hormone can trigger a cascading effect, which in turn produce more than a billion enzyme molecules.
15
Q
What are hormones clearance ?
A
- If the required effect is achieved, the hormone must be turned off by breaking down the hormone molecules.
- Some hormones are broken down in target cells but most are broken down in the liver and kidneys, and excreted in the bile or in the urine.
16
Q
Explain the control of hormone secretion
A
• To maintain homeostasis, the amount of hormone produced by an endocrine gland must be very closely regulated.
• Hormonal secretions are generally regulated by negative feedback systems, whereby the response produced by the
secretion of the hormone is opposite to the stimulus that caused the secretion.
17
Q
Types of hormones
A
- Steroid hormones
2. Amine and protein hormones
18
Q
Characteristic of steroid hormones
A
Steroid hormone are lipid & are derived from cholesterol
19
Q
Examples of steroid hormones
A
1. Adrenal cortical hormones (corticoids) • Cortisol, aldosterone 2. Sex Hormones • Female (Oestrogen, Progesterone) • Male (Testosterone)
20
Q
Explain mode of action of steroid hormones?
A
- Steroid hormones diffuses across the plasma membrane of the targeted cells
- Once inside the cell, hormones bind to the specific & complementary receptor. The receptor may be on mitochondria , on the other organelles or in the nucleus.
- The hormone-receptor complex activates the gene controlling the formation of particular proteins.
- Gene is transcribed to produce mRNA
- mRNA moves out of nucleus to bind to ribosme
- Ribosome performs translation to produce protein
21
Q
Characteristics of amine and proteins hormones
A
Non-steroid hormones are water-soluble
22
Q
What is amine hormones?
A
AMINEHORMONES
• Modified amino acids
• Examples: Epinephrine,
23
Q
What is protein hormones?
A
PROTEINHORMONES
• Chains of amino acids
24
Q
Explain the mode of action of protein and Amine hormones
A
- Non-steroid hormones do not enter the target cell (they are mostly water soluble )
- These hormones binds to the receptors on the plasma-membrane, forming hormone-receptor complex
- The binding of hormone with receptor causes a secondary messenger (cAMP)cyclic AMP to be produced and trigger enzyme cascade to acitvate particular enzymes.
25
What is the function of hypothalamus?
• Located at the base of the brain, on top of pituitary gland
• Regulates body temperature,
water balance and heart rate
• Many functions of hypothalamus are carried out through the pituitary gland
26
What is the function of pituitary glands ?
* Located under hypothalamus and is joined to hypothalamus by infundibulum
* Many pituitary hormones regulate the activity of the other endocrine glands: MASTER GLAND
27
The pituitary consists of 2 portions:
1. anterior pituitary
| 2. exterior pituitary
28
What does the true endocrine gland, composed of?
several types of hormone-secreting cells in a network of capillaries
29
What are the secretions of the anterior lobe are controlled by?
releasing and inhibiting factors secreted by the neurosecretory cells located in the hypothalamus.
These factors are themselves hormones and are carried by the blood to the anterior lobe of the pituitary
30
Explain secretion of hormones by the anterior lobe
1. Neurosecretory cells release inhibiting or releasing factors ( e.g :GH releasing factor)into the portal capillaries.
2. Inhibiting/ releasing factors travel to the anterior lobe via blood/portal system
3. Cells in the anterior lobe are stimulated to secrete hormones into the bloodstream.
4. Hormones travel to target organs.
31
Hormones synthesized by the anterior lobe:
```
TSH
PRL
FSH
LH
ACTH
GH
```
32
Target organs of FSH
Ovaries and testes
33
Main effect of FSH
In females: growth of follicles in the ovaries In males: production of sperm
34
Target organ of LH
Ovaries and testes
35
Main effect of LH
In females: ovulation and maintenance of corpus luteum
| In males: secretion of testosterone
36
Target organ of GH
All cells( Bones/ muscles )
37
Main effect of GH
Growth and protein synthesis
38
Target organ of TSH
Thyroid gland
39
Main effect of TSH
Secretion of hormones from the thyroid
40
Target organ of - adrenocorticotropic
Adrenal cortex
41
Main effect of ACTH
Secretion of hormones from the adrenal cortex
42
Target organ of prolactin
Mammary glands
43
Main effect of prolactin
Milk production
44
What is the posterior pituitary made up of ?
Mainly a capillary bed and the axon endings of neurosecretory cells whose cell bodies are in the hypothalamus
45
Neurosecretory cells in hypothalamus produce hormones which pass through?
axon endings in the posterior pituitary and are stored until released.
46
Explain the release of hormones by the posterior lobe
1.Neurosecretory cells in the hypothalamus produces hormones such as ADH and OT
2 Hormones travel to the posterior lobe via cell extensions of neurosecretory cells
3.Hypothalamus send nerve impulse through the neurosecretory cells. Hormones released by posterior pituitary into bloodstream.
4.Hormones travel to target organs
47
How does the hypothalamus and APG control the over secretion of thyroxine?
Secretion of TSH by the anterior lobe is controlled by TSH inhibiting factors
secreted by the neurosecretory cells located in the hypothalamus. Lesser TSH is secreted into blood, in return lesser thyroxine is secreted by the thyroid gland.
48
Does the PPG synthesised hormones?
No. The posterior lobe only stores and releases the hormones produced by neurosecretory cells in the hypothalamus
49
HORMONES RELEASED BY POSTERIOR PITUITARY GLAND
ADH, OT
50
Target organ of ADH- antidiuretic
Kidneys
51
Main effect of ADH
Reabsorption of water
52
Target organ of OT- oxytocin
Uterus and Mammary glands
53
Main effects of OT
Contractions of uterus during childbirth
| Release of milk
54
Explain production of ADH
* When water content in blood is low; ADH is released and the kidneys respond by reabsorbing more water.
* As the blood becomes dilute, less ADH is released (negative feedback)
55
Describe the pineal gland
The pineal gland, located in the brain, produces melatonin, primarily at night.
Melatonin is involved in regulation of sleep patterns.
56
Describe thyroid and parathyroid glands
Thyroid gland is in the neck, just below the larynx.
Parathyroid glands are embedded in the posterior surface of the thyroid gland
57
The main hormone produced by the thyroid gland is ??
thyroxine which contains four iodine atoms.
58
Function of thyroxine
increases metabolic rate and therefore O2 consumption and heat production - affects many tissues in the body.
59
Explain the Regulation of thyroxine level by negative feedback
```
1.Neurosecretory
cells of the hypothalamus
secrete TSH-releasing
hormone
2.The releasing hormone causes
the anterior pituitary to secrete
thyroid-stimulating hormone (TSH)
3.TSH causes the thyroid to
secrete thyroxine, which
increases cellular metabolism
throughout the body
4.Thyroxine inhibits
TSH-releasing hormone
and TSH release by
negative feedback
```
60
Thyroid gland produces calcitonin function of calcitonin ?
Calcitonin lowers the calcium level in the blood.
61
Low calcium levels stimulate the release of ?
parathyroid hormone (PTH) by the parathyroid glands to increase blood calcium levels.
62
Explain the use of calcitonin
reduces calcium in blood :
- Osteoclasts inhibited/osteoblasts stimulated/deposit calcium into the skeleton
- Reduces calcium absorption in small intestines
- Reduces calcium reabsorption in kidneys
63
Explain the use of parathormone/ parathyroid hormone
increases calcium in blood:
- Osteoclasts stimulated/release calcium from skeleton
- Increases calcium absorption in small intestines
- Increases calcium reabsorption in kidneys
64
What are the target cells of calcitonin?
Kidneys, small intestines, osteoblasts in bones
65
What are the target cells of parathyroid hormone?
Kidneys, small intestines, osteoclasts in bones
66
Describe thymus gland
Thymus is a lobular gland that lies in the upper thoracic cavity.
67
Hormone released by thymus gland
thymosin
68
Target cell of thymosin
T lymphocytes
69
Main effects of thymosins
Stimulates development and maturation of T lymphocytes
70
Describe adrenal glands
Two adrenal glands sit atop the kidneys.
Each gland consists of two parts: an outer adrenal cortex and an inner adrenal medulla.
Adrenal hormones increase during times of physical and emotional stress.
71
The hypothalamus exerts control over both portions:
Nerve impulses travel via the brain stem to the spinal cord to sympathetic nerve fibers to the adrenal medulla.
The hypothalamus uses ACTH‑releasing hormone (Adrenocorticotropic hormone) to control the anterior pituitary’s secretion of ACTH in return controlling secretions from the adrenal cortex (mainly cortisol and little control over aldosterone)
72
Describe the adrenal medulla
Release epinephrine (adrenaline) & norepinephrine (noradrenaline)
- bring about body changes corresponding to an emergency (fight-or-flight responses)
73
Function of epinephrine (adrenaline) & norepinephrine (noradrenaline)
Increase blood glucose level & metabolic rate.
The bronchioles dilate and breathing rate increases.
Blood vessels to the digestive tract and skin constrict; those to the skeletal muscles dilate.
The cardiac muscle contracts more forcefully and the heart rate increases.
74
Describe adrenal cortex
The adrenal cortex secretes two types of hormones: glucocorticoids and mineralocorticoids.
75
Function of glucocorticoids
Glucocorticoids (regulate blood glucose level), mainly cortisol
Raises blood glucose levels
Helps with repair of damaged tissues
76
Function of mineralocorticoids
Mineralocorticoids (regulate levels of minerals) mainly aldosterone
The primary target organ is the kidney
It promotes the reabsorption of Na+ and the excretion of K+
77
Describe short- term response and the adrenal medulla
1. Stressful stimuli cause the hypothalamus to activate the adrenal medulla via nerve impulses.
2. The adrenal medulla secretes epinephrine and norepinephrine
78
Effects of epinephrine and norepinephrine :
- glycogen broke down to glucose : increase blood glucose
- increase blood pressure
- increase breathing rate
- increase metabolic rate
- change blood flow patterns, leading to increased alertness and decrease digestive , extcretory and reproductive system .
79
Describe the long-term stress response and the adrenal cortex
1. Stress stimuli cause the hypothalamus to activate the adrenal cortex via hormonal signals.
2. The adrenal cortex secrets mineralocorticoid and glucocorticoids .
80
Effects of mineralocorticoid ;
- Retention of sodium ions and water by kidneys
| - increase blood volume and blood pressure.
81
Effects of glucocorticoid :
- proteins and fats broken down and converted to glucose ,leading to increased blood glucose
- partial suppression of immune system
82
Hormones released by adrenal cortex
Corticosteroids including:
Aldosterone
Cortisol
83
Target cell and main effects of aldosterone
kidney
| Increases reabsorption of sodium ions and secretion of potassium ions
84
Target cell and main effects of
| cortisol
most cells
| Promotes normal metabolism; helps the body deal with stress; promotes repair of damaged cells
85
Hormones released by adrenal medulla
Adrenaline and Noradrenaline
86
Target cell and main effects of Adrenaline and Noradrenaline
most tissues
| Prepares the body for fight-or-flight responses; reinforces the effects of the sympathetic nervous system
87
Describe pancreas
The pancreas lies below the stomach and alongside the duodenum
88
The pancreas is composed of two types of tissues:
Exocrine tissue produces and secretes digestive juices into the small intestine by way of ducts.
```
Endocrine tissues called pancreatic islets (islets of Langerhans)
- Alpha () cells releases glucagon
Beta Cells () releases insulin
```
89
Hormones released by pancrease
insulin and glucagon
90
Target cell and main effects of insulin
most cells
| Stimulates uptakes of glucose; lowers blood glucose level
91
Target cell and main effects of glucagon
Liver and fat storage tissues
| Stimulates breakdown of glycogen and fat; increases blood glucose level
92
Hormones released by testes
androgens
93
Target cell and main effects of
| androgens
many tissues
| stmulate sperm production; growth of skeleton and muscles and male sexual characteristics
94
Hormones released by ovaries
oestrogen and progesterone
95
Target cell and main effects of oestrogen
many tissues
| Stimulate the development of female characteristics; regulate the menstrual cycle
96
Target cell and main effects of
| progesterone
Uterus and mammary gland
| Regulates menstrual cycle and pregnancy; prepares mammary glands for milk secretion
