Endocrine System Flashcards
Describe how cells make up organisms
Use the cardiovascular system as an example
Cell
Specialised function e.g. cardiomyocyte
Tissue:
Group of cells working together e.g. myocardium
Organ:
Group of tissues working together to perform a function
E.g. the heart
Organ system e.g. cardiovascular system
Organisms
What are the main tissue types in the endocrine system and give examples of locations and functions of these
Epithelial: Make up the bulk of most glands and secretes many types of hormones
Connective: blood circulates hormones throughout the body
Nervous: parts of the brain secrete some hormones and control release of others; some neurons secrete hormones
What is epithelia?
They cover outer or line inner surfaces
Epithelia have no capillaries of their own
They receive oxygen through nutrients from the blood supply and connective tissue underneath
Draw an example of a simple squamous epithelium and say where this is found
See lecture notes
Found in air sacs of the lungs
Draw a diagram of a simple cuboidal epithelium and state where this is found in the body
See lecture notes
Found in the kidney
Draw an example of simple columnar epithelium and state where this is found
See lecture notes
Found in the intestine
Draw an example of pseudo-stratified ciliated columnar epithelium and state where this is found
See lecture notes
Found in respiratory tract
Draw stratified squamous epithelium and state where this is found in the body
See lecture notes
Esophagus
Draw the flow chart showing epithelia classification
See lecture notes
What is the function of ribosomes?
Where proteins are synthesised
Draw a diagram of a cell showing the apical and basal sides of the cell
Apical is on the side of the lumen
Basal is in contact with the basal lamina and underlying tissue e.g. blood capillaries and muscles
Describe what epithelial tissue is, the function and the structure
Draw a diagram showing this
Tightly packed cells that form a continuous layer
Protective function
May also be able to secrete, absorb, excrete or filter substances
Exposed on one side, connected to a basement membrane on the other side
Named based on the number of cell layers and the shape of the cells
These features are related to the specialised function that the cells need to perform
See lecture notes for diagram
What is homeostasis?
Homeostasis is the maintenance of a relatively constant internal environment
The body systems help to maintain homeostasis by adjusting their physiological response when conditions change
Internal environment is maintained close to an optimal point even though the external environment may change dramatically e.g. the external temperature may change but the body temperature remains near 37 degrees
If homeostasis is not maintained, the function of the organism is adversely adversely affected and illness occurs
The existence of a stable internal environment
It is crucial to survival
The environment is unpredictable
All body systems must react to fluctuations in the environment to resist change
Pathology emerges when homeostatic mechanisms break down
Discuss how body systems maintain homeostasis
All body systems work together to keep the internal environment relatively constant and maintain homeostasis
The nervous and endocrine systems co-ordinate and regulate the other systems
The cardiovascular, respiratory, digestive and urinary systems regulate the amount of gases, nutrients, water and wastes in the blood and interstitial fluid
Why is a stable environment crucial? And what happens if this is not maintained?
All metabolic reactions under influence of enzymatic control
Enzymes act maximally in a desired range of:
Ph
Temperature
Destabilisation leads to pathology and death
What are the two principles of homeostatic regulation
Requires co-ordinated efforts of multiple organ systems
Two general mechanisms:
Intrinsic (auto) regulation: cells regulating their own milieu
Extrinsic regulation: nervous and endocrine system maintain this
Discuss the concept of normal physiological ranges
Physiological functions are maintain within a normal range rather than a fixed value
Physiological values oscillate around a set-point
Set points may vary accordingly to changing environments/activity
The regulatory processes must therefore by dynamic
Homeostatic set points are determined by genetics, age, gender, health status and environment
What is the normal temperature range? And what is high and low temperature called?
37 degrees
Pyrexia is too hot
Hypothermia is too cold
What is the normal range of pulse rate? What is high and low pulse rate called?
60-80 beats per minute
Fast: tachycardia
Slow: bradycardia
What is the normal range of blood pressure?
What is high and low blood pressure called?
120/80mmHg
High: hypertension
Low: hypotension
What is the normal range of blood glucose?
What is high and low blood glucose called?
4.5 - 5.6mmol/l
High: hyperglycaemia
Low: hypoglycaemia
What is the range of respiratory rate? ;
14 to 20 respiration’s/ minute
What is the range of blood gases:
And what are high and low ranges called
Arterial pO2; 75-100mmHg
CO2; 36-46mmHg
High: hypercapnia
Low: hypocapnia
What is the range of pH balance in arterial blood?
7.35 - 7.45
What is the blood electrolyte balance?
Na+, K+, Cl-, Ca2+, Mg2+
What is negative feedback?
Primary mechanism of homeostatic regulation, providing ling term control over internal conditions by opposing change
Negative feedback resists physiological deflections away from the body’s set-point
What is positive feedback?
Initial stimulus produces a response that exaggerates the change seldom encountered (blood clotting cascade and childbirth)
What is negative feedback and what are the three components?
Negative feedback is the primary mechanism that is used to keep a variable close to the optimum level and maintain homeostasis
The three compartments are:
- a sensory that detects a change in the internal environment
- a control centre that instructs a response to counteract the change
- an effector that gets activated to produce a physiological response that brings conditions back to the optimum level
Draw and label a negative feedback diagram, showing the sensor, control centre and the effect that resolves the issue
See lecture notes
How does Negative feedback regulate high body temperature?
Draw a diagram showing this
When body temperature rises above normal
The hypothalamus senses the changes and causes:
Blood vessels to dilate
Sweat glands to secrete, so that the the rapture returns to normal
When the body temperature is above normal, the control centre directs the skin to dilate. This allows more blood to flow near the surface of the body, where heat can be lost to the environment. In addition, the nervous system activates the sweat glands, and the evaporation of sweat helps lower body temperature. Gradually, body temperature decreases to 37 degrees
See lecture notes for diagram
How does negative feedback regulate low body temperature?
Use a diagram to show this
See lecture notes for diagram
When body temperature falls below normal:
The hypothalamus senses the change and causes blood vessels to constrict
In addition, shivering may occur to bring the temperature back up to normal. In this way, the original stimulus is resolved, or corrected
The control centre directs blood vessels of the skin to constrict. This conserves heat. If the body temperature falls even lower, the control centre sends nerve impulses to the skeletal muscles and shivering occurs. Shivering generates hear and gradually the body temperature rises to 37 degrees. When the temperature rises to normal, the control centre is inactivated
What is positive feedback?
Positive feedback is a mechanism by which the body responds to a change by amplifying it
It brings about rapid change in the same direction as the stimulus
Positive feedback DOES NOT maintain homeostasis
Only few biological functions demonstrate positive feedback e.g. childbirth and blood clotting
Positive feedback may also occur in disease
For example: a fever that rises above 42 degrees
Positive feedback does not last forever, once the relevant biological process is complete, other controls cut off the positive feedback loop and restores balance.
What are hormones?
Endogenous bio active substances which are distributed throughout the body via the bloodstream, to induce physiological changes in specific target cells
How do hormones target specific cells?
Most hormones are distributed by the bloodstream to target cells. Target cells have receptors for the hormones, and a hormone combines with a receptor. Like a key fits its lock
1: cells of endocrine gland produce hormone
2: gland secretes hormones into the bloodstream
3: hormones circulate throughout the body
4: hormones bind onto to target cells
If the receptor binds to the target cell a response happens
If the receptor doesn’t bind, no effects happen on the cell
What is a gland?
One or more cells that secrete a substance
What does unicellular mean?
One cell (goblet cells)
What does multicellular mean?
More than one cell
What are exocrine glands?
Have ducts (tubes) to carry the secretion away from the site of function
Examples: sweat, oil and gastric glands
What are endocrine glands:
Are ductless, they secrete hormones that enter capillaries and circulate through the body to the target organs
- thyroid glands
- adrenal glands
- pituitary glands
Is the pancreas an exocrine or endocrine gland?
It is an exocrine gland (digestive enzymes) and an endocrine gland (insulin and glucagone)
Draw diagrams showing the difference between circulating hormones and local hormones
See lecture notes
Compare endocrine, paracrine and autocrine hormones
Endocrine: cells realise chemicals called hormones into the circulation which act as target cells to regulate their activities
Paracrine: local hormone
Communication occurs from cell to cell within a tissue
Autocrine:
Local hormone
Communication occurs when the hormones act on the same cells that secretes them
Circulating (endocrine) hormones are carried through the bloodstream to act on distant target cells. Pancrines act on neighbouring cells and autocrines act on the same cells that produce them
Compare and contrast the endocrine and nervous system when controlling homeostasis
Endocrine and nervous systems work in parallel to control homeostasis, growth and maturation
Nervous system co-ordinates rapid responses to stimuli using electrical conduction
The endocrine system maintains long term control using chemical signals
Endocrine system:
Collection of glands secreting chemical messengers called hormones
Hormones pass through the blood to reach target receptors
How does the action of a neurotransmitter differ from that of a hormone?
Nerve impluses pass along an axon causing the realise of a chemical signal, the neurotransmitter
A hormone e.g. insulin, is a chemical signal that travels in the cardiovascular system from the pancreas to the liver where it causes liver cells to store glucose as glycogen
Compare the nervous system and endocrine system in the following properties:
Anatomical arrangement
Nervous system:
A wired system, specific structural arrangement between neurons and their target cells, with structural continuity in the system
Endocrine system:
A wireless system
Endocrine glands are widely dispersed and not structurally related to one another or their target cells
Compare the nervous system and endocrine system in the following properties:
Type of chemical messenger
Nervous system:
Neurotransmitters released into the synaptic cleft
Endocrine system:
Hormones released into the blood
Compare the nervous system and endocrine system in the following properties:
Distance of action of chemical messengers
Nervous system:
Very short distance (diffuses across synaptic cleft)
Endocrine system:
Long distance
Carried by the blood
Compare the nervous system and endocrine system in the following properties:
Specificity of action on target cells
Nervous system: dependant on close anatomical relationship between neurons and their target cells
Endocrine system:
Dependant on specificity of target cell binding and responsiveness to a particular hormone
Compare the nervous system and endocrine system in the following properties:
Speed of response
Nervous system
General rapid
Milliseconds
Endocrine system:
Generally slow
Minutes to hours
Compare the nervous system and endocrine system in the following properties:
Duration of action
Nervous system:
Brief
Milliseconds
Endocrine:
Long
Minutes to days or longer
Compare the nervous system and endocrine system in the following properties:
Major functions
Nervous system:
Co-ordinates rapid, precise responses
Endocrine system:
Controls activities that require long duration rather than speed
Name the tissues and glands with secondary endocrine functions
Thymus gland
Heart
Stomach
Adipose tissue
Kidneys
Name the main endocrine glands
Pineal body
Pituitary gland
Thyroid gland
Parathyroid gland
Adrenal gland
Pancreatic islets
Ovaries in females
Testes in males
What are the five types of hormones and how are they grouped?
Hormones are grouped into 5 classes based on their structure
1: steroids (oestrogen)
2: peptides (oxytocin and ADH)
3: amines (epinephrine)
4: proteins (growth hormones and insulin)
5: glycoproteins (FSH/TSH)
What are steroids?
Lipids derived from cholesterol
Cortisol, secreted from adrenal cortex plays a role in mediating stress response
Testosterone and oestradiol secreted from the gonads and placenta is response for male and female sexual characteristics
Once synthesised, steroids pass into the bloodstream by they are not stored
Synthesis rate controls the amounts
What is cortisol used for?
Glucocorticoid Used in stress
What are progesterone and androstenedione used for?
They are sex steroids used for sexual differentiation
How does the structure of estradiol differ from that of testosterone?
Estradiol: has HO on the end of the basic steroid structure
Testosterone: has O with a double bond on the end of the basic steroid structure
What is a peptide?
Short chain of amino acids
Large. Majority of hormones produced
Secreted by pituitary, parathyroid, heart, stomach, liver and kidneys
Synthesised as precursor molecules and stored in secretory granules
Different end hormones can be made by cleaving a common precursor with a different enzyme
What are amines?
Derived from tyrosine
Secreted from thyroid and adrenal medulla
Amines like epinephrine (adrenaline) stored as granules in the cytoplasm until needed
Describe the mechanism of action of lipid soluble steroid or thyroid hormones
A steroid hormone passes directly through the target cells plasma membrane before binding to a receptor in the nucleus or cytoplasm. The hormone-receptor complex binds to DNA and gene expression follows
Non water soluble:
Pass through the plasma membrane initiating a 2-step process
Activated hormone receptor complex is formed within the cell
Complex binds to DNA and activates specific genes
Gene activation leads to the production of key proteins
Draw and label a diagram showing the mechanism of action of lipid-soluble hormones
See lecture notes
Draw and label a diagram showing the mechanism of action of lipid soluble steroid or thyroid hormones
See lecture notes
Dra wand label the mechanism of action of water soluble hormones such as amines, peptides and proteins
See lecture notes
What is the hypothalamus and pituitary gland?
The hypothalamus is the part of the brain that controls the endocrine system, known as the master switchboard
The pituitary gland and the hypothalamus act as a uni, regulating the activity of the endocrine glands
The pituitary gland lies below the hypothalamus, to which it is attached by a stalk
It is the size of a pea and weighs about 500mg and consists of two main parts that originate from different types of cells
What are the two parts of the pituitary gland and what are the functions of the pituitary gland?
The anterior pituitary (adenohypophysis) is an upgrowth of glandular epithelium from the pharynx
The posterior pituitary (neurohypophysis) is a down growth of nervous tissue from the brain. There is a network of nerve fibres between the hypothalamus and the posterior pituitary
What hormones are realised from the hypothalamus and the posterior pituitary and what are the effects of these on the body?
Releasing and inhibiting hormones:
Control the anterior pituitary
Antidiuretic hormone (ADH) Released by posterior pituitary, causes water reuptake by the kidneys
Oxytocin:
Released by posterior pituitary, causes uterine contractions
What hormones are released from the anterior pituitary gland and what affects do these have on the body?
Gonadotropic hormones:
stimulate gonads
Thyroid-stimulating hormones (TSH)
Stimulates thyroid
Adrenocorticotropic hormone (ATCH) Stimulates adrenal cortex
Prolactin:
Causes milk production
Growth hormone (GH) Causes cell division, protein synthesis and bone growth
What are the two hormones secreted by the hypothalamus? Where are these stored And what are the functions of these
ADH and oxytocin
They are stored and secreted by the posterior pituitary
Oxytocin:
Mammary glands
Smooth muscle in the uterine
ADH:
Kidney tubules
How does the hypothalamus control the secretions from the anterior pituitary?
The hypothalamus controls the secretions of the anterior pituitary and the anterior pituitary controls the secretions of the thyroid gland, and renal cortex and gonads. Which are also endocrine glands
Growth hormone and prolactin are also produced by the anterior pituitary
What hormones are secreted by the anterior pituitary gland and what are their functions?
Growth hormone:
Regulates metabolism
Promotes tissue growth especially of bones and muscles
Thyroid stimulating hormone (TSH)
Stimulates growth and activity of the thyroid gland and secretion of T3 and T4
Adrenocorticotropic hormone:
Stimulates the adrenal cortex to secrete glucocorticoids
Prolactin (PRL)
Stimulates growth of breast tissue and milk production
Follicle stimulating hormone (FSH)
Stimulates production of sperm in the testes, stimulates secretion of oestrogen by the ovaries, maturation of ovarian follicles, ovulation
Luteinising hormone (LH) Stimulates secretion of testosterone by the testes, stimulates secretion of progesterone by the corpus Luteum
Draw and label a negative feedback system showing the secretion of hormones by the anterior pituitary gland
See lecture notes
How does the hypothalamus stimulate the anterior pituitary?
The hypothalamus releases multiple hormones that influence hormone production in the anterior pituitary
Both peptides
Releasing hormones:
Stimulates release of hormones from the anterior pituitary
Inhibiting hormones:
Inhibit the release of hormones from the anterior pituitary
How does the hypothalamus stimulate the posterior pituitary?
Produces two hormones that are stored in and released by the posterior pituitary
What hormones are secreted by the anterior pituitary gland? Wheat are their functions? And how are they regulated?
ADH:
Increases water reabsorption by the kidney tubules (water returns to the blood)
Decreases sweating
Causes vasoconstriction in large amounts
Regulated by decreased water content in the body (alcohol inhibits secretion)
Oxytocin:
Promotes contraction of the myometrium of the uterus
Promotes release of Milk from the mammary glands
Regulated by: nerve impulses from the hypothalamus, the result of stretching of cervix or stimulation of nipple secretion from placenta at end of gestation
Stimulus is unknown
Describe positive feedback using childbirth as an example
When a woman is giving birth, the head of the baby begins to press against the cervix (entrance to the womb), stimulating sensory receptors there. When nerve signals reach the brain, the brain causes the pituitary glands to secrete the hormone oxytocin. Oxytocin travels in the blood and causes the uterus to contract.
As labour continues, the cervix is increasingly stimulated, and uterine contractions become stronger until birth occurs
Draw and label a diagram showing how oxytocin stimulates the uterine smooth muscles during childbirth
See lecture notes
Drawn and label a diagram showing how oxytocin stimulates the muscle cells of lactating breasts after childbirth
See lecture notes
