the endocrine system

Question 1

what are the 2 types of endocrine glands

Answer 1

Exocrine glands: secrete their
products into duct (e.g., sweat or
the intestines)
2) Endocrine glands: ductless and
release hormones into the blood

Question 2

what is the endocrine system

Answer 2

The endocrine system is one of
the body two major communication systems:
- Consists of glands and organs that
secrete hormones
- A single gland may secret multiple
hormones

Question 3

what are Hormones

Answer 3

Hormones are chemical
messengers carried by the blood
to target cells

Question 4

hormones

Answer 4

Releases by glands to elicit a response
- Enhance or inhibit cellular reactions

Present at v. low concentrations
- Much lower than other similar molecules

Question 5

function of hormones

Answer 5

Hormones help regulate:
Chemical composition and volume of internal environment (e.g., interstitial fluid)
Metabolism and energy balance
Contraction of smooth and cardiac muscle fibers
Glandular secretions
Some immune system activities

2. Control growth and development
3. Regulate operation of reproductive system
4. Help establish circadian rhythm

Question 6

how do hormones operate

Answer 6

Operate in synchrony with the nervous system
- Endocrine = chemical messengers
Act (relatively) more slowly Often longer lasting effects
- Nervous system = electrical conduit system
Instantaneous
Short-lived

Question 7

what are the 3 structures of hormones

Answer 7

amines

peptide and proties

steriods

Question 8

what are examples amine hormones

Answer 8

Thyroid hormones, Dopamine, Catecholamines (Epinephrine & Norepinephrine)
Derivatives of the amino acid tyrosine
Secreted by the adrenal medulla and the hypothalamus

Question 9

what are examples of peptide hormones

Answer 9

The majority of hormones are polypeptides
Many peptide hormones are synthesised as large, inactive molecules that are cleaved into
active fragments.

Question 10

what are examples of steroids

Answer 10

Aldosterone, Cortisol, Androgens (e.g., testosterone), Estrogens
Produced from cholesterol by the adrenal cortex and the gonads

Question 11

how do hormones transport

Answer 11

Peptide and all catecholamine hormones
are water soluble and therefore circulate
dissolved in the plasma.

Some peptide hormones bind to plasma
proteins

Steroid and thyroid hormones circulate
mainly bound to plasma proteins.

Question 12

how are hormones excreted

Answer 12

the liver and kidneys are the major organs that remove hormones from the plasma by metabolizing or excreting them.

Liver = major organ responsible for the metabolic inactivation
(otherwise called metabolism or biotransformation)

Kidneys = filter the blood, removing waste products, including
hormones and their metabolites.

Peptide hormones and catecholamines are rapidly removed from the blood

Steroid and thyroid hormones are removed more slowly Because they circulate bound to plasma proteins

After their secretion, some hormones are metabolized to more active molecules in their target cells or organs.

Question 13

how do hormones work

Answer 13

Public transport (blood)– specific destinations (target tissues)
The presence of specific receptors for those hormones on or in the target cells necessary for response

Hormone receptors
For lipid-soluble steroid and thyroid
hormones, the majority of receptors are inside target cells affect cell function by altering gene expression

For water-soluble peptide hormones and
catecholamines, receptors are on the plasma membrane peptide hormones and catecholamines may exert both rapid (nongenomic) and slower (gene transcription) actions on the same target cell.

Question 14

what determines the responsiveness of a hormone

Answer 14

the hormone’s concentration in the blood,
(2) the abundance of the target cell’s hormone receptors, and
(3) influences exerted by other hormones.

Question 15

what are the 3 hormonal interactions

Answer 15

Permissive: action of one hormone enhances the responsiveness or activity of another hormone
e.g., epinephrine & thyroid hormones (T3 and T4) stimulation of lipolysis

Synergistic: the effect of two hormones acting together is greater or more
extensive than one hormone acting on its own.
e.g., follicle-stimulating hormone & estrogens

Antagonistic: one hormone opposes the actions of another hormone
e.g., insulin & glucagon

Negative feedback systems regulate the secretion of many hormones.

Question 16

what controls hormone secretion

Answer 16

Plasma concentration of an ion or nutrient that the hormone regulates
2. Neural input to the endocrine cells
3. Other hormones

Question 17

Neural input to the endocrine cells effect on secretion

Answer 17

The autonomic nervous system
controls hormone secretion via the
adrenal medulla and other
endocrine glands.
Neurons in the hypothalamus also
secrete hormones.

Neural input from the autonomic
nervous system controls the
secretion of many hormones.

Question 18

other hormones effect of secretion

Answer 18

Often the secretion of a particular
hormone is directly controlled by the
blood concentration of another hormone

A hormone that stimulates the
secretion of another hormone is
often referred to as a tropic
hormone.

E.g., Thyroid-stimulating hormone
(TSH) or Follicle-stimulating
hormone (FSH)

Question 19

what are endocrine disorders

Answer 19

he wide variety of hormones and endocrine glands determines that
disorders of the endocrine system vary considerably.

Question 20

what are the 4 types of endocrine diseases

Answer 20

Too little hormones (hyposecretion)
E.g., type 1 diabetes

Too much hormone (hypersecretion)
E.g., gigantism

Decreases responsiveness of the target cells to hormones (hyporesponsiveness)
E.g., type 2 diabetes

Increases responsiveness of the target cells to hormone (hyperresponsiveness)
E.g., elevated heart rate due to increased circulating levels of thyroid hormone

Question 21

pharmacological effects on hormones

Answer 21

Pharmacological administration of hormones for medical purposes
- Can result in supraphysiological concentrations and effects not typically observed
with at physiological concentrations

Question 22

what impacts the risk of pharmacological

Answer 22

the type of steroid (oral corticosteroids more likely to cause side effects as they are acting
systemically).
the dose
the length of treatment
the age of the patient (children and older adults more susceptible)

Question 23

what is the posterior pituitary gland

Answer 23

The posterior pituitary is really a neural extension of the hypothalamus
Hormones are synthesized in the
hypothalamus, axons pass down the
infundibulum, terminate in the
posterior pituitary and release
hormones
E.g., oxytocin and vasopressin

Question 24

what does the anterior pituitary gland secret

Answer 24

The anterior pituitary gland secretes growth hormone (GH), thyroid-
stimulating hormone (TSH), adrenocorticotropic hormone (ACTH),
prolactin, and two gonadotropic hormones—follicle-stimulating hormone
(FSH) and luteinizing hormone (LH).

Question 25

pathway of the hormones

Answer 25

Secretion of the anterior pituitary
gland hormones is controlled mainly
by hypophysiotropic hormones from
the hypothalamus via the portal
vessels connecting the hypothalamus
and anterior pituitary gland.

Question 26

The anterior pituitary gland &
the hypothalamus

Answer 26

Typical sequence by which a hypophysiotropic
hormone (hormone 1 from the hypothalamus)
controls the secretion of an anterior pituitary
gland hormone (hormone 2), which in turn
controls the secretion of a hormone by a third
endocrine gland (hormone 3)

Question 27

what is the thyroid gland

Answer 27

Thyroid hormones has diverse and
widespread effects throughout the body.
E.g. protein synthesis in follicular epithelial cells,
increases DNA replication and cell division
The thyroid gland produces thyroxine (called T4 because it contains four
iodines) and triiodothyronine (T3, three iodines)
Most T4 converted to T3 in target tissues via enzymes, therefore T3 considered major thyroid
hormone
The thyroid gland sits within the neck in front of the trachea

Question 28

control of thyroid function

Answer 28

Thyroid-stimulating hormone (TSH) production is
controlled by the negative feedback action
of T3 and T4 on the anterior pituitary gland and, to a
lesser extent, the hypothalamus

Note: TSH causes growth
(hypertrophy) of thyroid tissue.
Excessive exposure of the thyroid
gland to TSH can cause goiter

Question 29

what are the actions of thyroid hormones

Answer 29

Increase T3 & T4 levels associated with ↑ oxidaƟve
substrate metabolism & ↑ mitochondrial enzyme
activity
↑ carbohydrate and lipid metabolism
Thus, T3 & T4 = high metabolic rate
T3 required for normal production of growth hormone from the anterior pituitary
gland.
T3 is a very important developmental hormone for the nervous system.

Question 30

what is cortisol

Answer 30

Cortisol secretion during stress is mediated by the
hypothalamus–anterior pituitary gland system

Question 31

during non stressful situations

Answer 31

Cortisol affects the responsiveness of smooth muscle cells to epinephrine
and norepinephrine (permissive action).
Thus, helps maintain normal blood pressure
Cortisol required to maintain the certain enzymes conc. involved in
metabolic homeostasis.
Thus, prevents plasma glucose concentration dropping too far below normal
Has anti-inflammatory and anti-immune functions

Question 32

cortisol over 24 hours

Answer 32

it has a normal diurnal rhythm

Question 33

in stressful situations

Answer 33

Effects on metabolism
1. Stimulation of protein catabolism in bone, lymph, muscle, and elsewhere
2. Stimulation of liver uptake of amino acids and their conversion to glucose
(gluconeogenesis)
3. Maintenance of plasma glucose concentrations
4. Stimulation of triglyceride catabolism in adipose tissue, with release of glycerol and fatty acids into the blood Physiological functions of cortisol

Enhanced vascular reactivity, improving cardiovascular performance

Unidentified protective effects against the damaging influences of stress

Inhibition of inflammation and specific immune responses

Inhibition of nonessential functions (e.g., reproduction &
growth)

Question 34

cortisol and recovery

Answer 34

Massage decreases circulating cortisol levels
Compression decreases circulating cortisol levels ??
Thus,
Supports recovery as:
↑ CorƟsol at rest inhibits immune system
↑ CorƟsol at rest inhibits inflammatory response
↑ corƟsol decreases capillary permeability in injured areas

Question 35

how does stress impact the sympathetic nervous system

Answer 35

When the stress response is triggered, the Sympathetic Nervous System is
activated, triggering the release of epinephrine
At the same time, the endocrine system releases cortisol from the adrenal gland

Question 36

what effect does cortisol have on epinephrine

Answer 36

synergistic which causes
Faster breakdown of fuel stores
Larger increase in cardiac function
Bigger increase in ventilation

Question 37

what hormones are important for growth

Answer 37

insulin-like growth factors 1 and 2
T3 (essential for growth during childhood and adolescents)
Insulin (mainly during fetal life)
Testosterone & estradiol

Question 38

what stimulates and inhibits the growth hormone

Answer 38

Growth hormone secretion is stimulated by growth
hormone-releasing hormone (GHRH) and inhibited by
somatostatin (SST)

Question 39

effects of growth hormone

Answer 39

Growth hormone is the major stimulus of postnatal growth.
It stimulates the release of IGF-1 from the liver and many other cells
IGF-1 then acts locally (and also as a circulating hormone) to stimulate cell
division.
Growth hormone also acts directly on cells to stimulate protein synthesis.
Growth hormone secretion is highest during adolescence.

Question 40

what produces testosterone in males and females

Answer 40

main source in Males produced in the testes
Source in Females
Also produced in smaller quantities in the ovaries and the adrenal cortex Peripheral conversion of androgens

Question 41

what produces Estrogen & Progestogen in males and females

Answer 41

in females: the overaies

women in menopause :
Some oestrogens also
produced in smaller
amounts by other tissues
(e.g., liver, pancreas, bone,
adrenal glands, skin, brain,
adipose tissue and breasts

for men:
Estrogen produce when FSH
binds to FSH receptors

Question 42

what does Oestrogen & Progestogen do

Answer 42

Promotes: development of female sex characteristics, regulates
menstrual cycle and adipose tissue growth

Question 43

what is Dehydroepiandrosterone (DHEA)

Answer 43

DHEA, and its sulfate (DHEAS) are hormones produced by the adrenal cortex
DHEAS are precursors for sex hormones such as testosterone and estradiol
DHEA/S affect various systems of the body ⇒ Purported to be anti-ageing
DHEA and DHEA-S production peaks at age 20-30 and then declines progressively
with age

Question 44

DHEA on age and exercise

Answer 44

DHEA/S increases following low and moderate intensity exercise in you but not older adults

Question 45

what is Hormone replacement therapy (HRT) and its effect on men and female

Answer 45

In women, oestrogen-containing HRT, improves muscle function, maintains muscle mass and prevents fat infiltration into the muscle compartment.
Exercise and HRT can be considered counteractive treatments o age-related changes in muscle
phenotype

In men, testosterone-containing HRT seems to preserve muscle tissue and offset age-related muscle loss, rather than cause significant gains.