Hormonal Communication Flashcards
Define an ‘endocrine gland’
A group of cells which are specialised to secrete chemicals/hormones directly into the bloodstream
List the 8 main endocrine glands in the body
Pituitary Thyroid Adrenal Testis Pineal Thymus Pancreas Ovary
What are the three main hormones that the pituitary gland secretes and what are their functions?
Growth hormone- growth of bones and muscles
ADH- increases reabsorption of water into the kidneys
Gonadotrophins- development of ovaries and testes
What does the the thyroid gland secrete and what is its function?
Produces thyroxine which controls the rate of metabolism and promotes growth
What does the adrenal gland secrete and what is its function?
Adrenaline which increases heart rate and breathing rate and raises blood sugar level
What does the testis gland secrete and what is its function?
Testosterone which controls sperm production and secondary characteristics
What does the pineal gland secrete and what is its function?
Melatonin which affects reproductive development and daily cycle
What does the thymus secrete and what is its function?
Thymosin which promotes production and maturation of white blood cells
What does the pancreas secrete and what is its function?
Produces insulin and glucagon
Insulin converts excess glucose into glycogen in the liver
Glucagon which converts glycogen back to glucose in the liver
What does the ovary secrete and what is its function?
Oestrogen which controls ovulation and secondary characteristics
Progesterone which prepares the uterus lining for receiving an embryo
Define an exocrine gland
Glands that secrete chemicals through ducts into organs or to the surface of the body
What are the two types of hormones?
Steroid hormones
Non-steroid hormones
Explain the 6 key characteristics of a steroid hormone
Derived from cholesterol Hydrophobic Insoluble in water Work through plasma membranes Binds to protein in cytoplasm or nucleus to form a hormone receptor complex which acts as a transcription factor Control gene function directly
Explain the 5 key characteristics of a non-steroid hormone
Proteins
Water soluble
Hydrophilic
Bind to receptors on the plasma membranes
Work through intermediates (secondary messengers) to effect cellular processes
Give an example of a secondary messenger
CAMP
Give an example of a steroid hormone
Oestrogen
Give an example of a non-steroid hormone
Adrenaline
Where are adrenal glands located?
On top of each kidney
Explain the structure of the adrenal glands
The adrenal cortex- outer region of the glands- essential
The adrenal medulla- inner region of the glands- inessential hormones
Which hormones does the adrenal medulla secrete?
Adrenaline, Noradrenaline
Which hormones does the adrenal cortex secrete?
Cortisol, aldosterone, androgens
Describe the key features of cortisol
Steroid hormone Glucocorticoids class of hormones Causes increase in blood sugar levels, blood pressure and cardiovascular function in times of stress
Describe the key features and functions of aldosterone
Steroid hormone
Mineralocorticoid
Essential for sodium conservation in the kidney
Central role in homeostatic regulation of blood pressure, plasma Na+ and K+ ions
Describe the function of androgens
Small levels of testosterone and oestrogen produced
When does the adrenal cortex produce hormones?
When the sympathetic nervous system is active as the body is stressed
Describe the key features and functions of adrenaline
Non steroid hormone Fight of flight responses Heart race increase Pupils dilate Glycogenesis
Explain the process of how the fight or flight response is initiated
Threat detected
Hypothalamus communicates with sympathetic nervous system and adrenal-cortical system
Sympathetic nervous system uses neuronal pathways to initiate body reactions
Adrenal-cortical system uses hormones in the blood stream
What are the 7 physical fight or flight responses and what are the purposes?
Heart rate increases- pump more oxygenated blood around the body
Pupils dilate- take in as much light as possible
Arterioles in skin contract- more blood to major muscle groups
Blood glucose levels increase- increase respiration to provide energy for muscle contraction
Smooth muscle of airways relaxes- to allow more oxygen into the lungs
Non-essential systems shut down- focus on emergency functions
Difficultly focusing on small tasks- brain focused on a sole purpose
Explain the process of adrenaline triggering glycogenesis
Adrenaline binds to its receptor
Adenylyl cyclase is activated
Adenylyl cyclase triggers conversion of ATP into CAMP on the inner surface of cell membrane
CAMP levels increasing activates protein kinases which phosphorylate and activate enzymes that trigger conversion of glycogen into glucose
What type of process is adrenaline triggering glycogenesis said to be?
A cascade effect
Where is the pancreas located in the body?
In the upper abdomen behind the stomach
What are the two main roles of the pancreas?
To maintain blood glucose concentration
Digestion
Define ‘glandular organ’
An organ which produces and secretes hormones and enzymes
What are the two main functions of the pancreas?
Exocrine gland- to produce enzymes and release them via a duct into the duodenum
Endocrine gland- to produce hormones and release them into the bloodstream
What two substances does the exocrine gland part of the pancreas secrete?
Digestive enzymes
Alkaline pancreatic juice
What are the three main digestive enzymes produced in the pancreas and what are their roles?
Amylase- starch into simple sugars
Proteases- proteins into amino acids eg. trypsin
Lipases- lipids into fatty acids and glycerols
What two substances does the endocrine gland part of the pancreas secrete?
Produce insulin and glucagon
What are the islets of Langerhans?
Small regions of the endocrine tissue within exocrine tissue
What are the two types of cells that make up the islets of Langerhans?
Alpha cells
Beta cells
What is the role of an alpha cell?
Produce and secrete glucagon
What is the role of a beta cell?
Produce and secrete insulin
Are there more alpha or beta cells?
Alpha cells, they are also larger
Describe the histology of the islets of Langerhans under a microscope
Lightly stained
Large, spherical structures in clusters
Endocrine tissue
Describe the histology of the pancreatic acini
Darker stained
Small, berry shaped clusters
Exocrine tissue
What is the average concentration of blood glucose within the blood?
90 mg/cm-3
What three things cause an increase in blood glucose concentration?
Diet
Glycogenolysis
Gluconeogenesis
What is glycogenolysis?
Glycogen stored in the liver and muscle cells broken down into glucose and released into the bloodstream
What is gluconeogenesis?
Production of glucose from non-carbohydrate sources eg. liver= glycerol + amino acids = carbohydrates
What two factors cause a decrease in blood glucose concentration?
Respiration
Glycogenesis
How does respiration decrease glucose concentration?
Muscle cells need more glucose to contract during exercise
More glucose is used
Less glucose in the blood
What is glycogenesis?
Production of glycogen. Excess glucose(consumed in diet) converted into glycogen and stored in the liver
When is insulin secreted?
Beta cells detect that blood glucose concentration is too high
Explain how insulin lowers blood glucose levels
All cells have insulin receptors
Insulin binds to glycoprotein receptor
Binding causes change in tertiary structure of glucose transport protein channels
Channels open = more glucose in
Insulin activates enzymes to convert glucose to glycogen and fat
Give the 5 ways that insulin lowers blood glucose levels
Increases rate of absorption of glucose by cells
Increases respiratory rate of cells (higher uptake of glucose)
Increases rate of glycogenesis (stimulates liver to remove glucose and store as glycogen)
Increases rate of glucose to fat conversion
Inhibiting release of glucagon from alpha cells
Why does inslulin have to continually be secreted?
Insulin is broken down by enzymes in the liver
When is glucagon secreted?
When blood glucose concentrations are low
Which two cells have glucagon receptors?
Liver cells
Fat cells
Give the 3 ways glucagon increases blood glucose concentration
Glycogenolysis
Reduces the amount of glucose absorbed by liver cells
Increasing gluconeogenesis
Describe the process by which beta cells secrete insulin
1) Normal blood glucose concentration, potassium channels are open and potassium ions secrete out. -70mV resting potential
2) Blood glucose concentration rises and glucose enters by a glucose transporter
3) Glucose metabolised in mitochondria, results in production of ATP
4) ATP binds to ATP sensitive potassium channels and shuts them
5) Potassium ions are unable to diffuse out. Cell depolarised to -30mV
6) Voltage gated calcium channels open
7) Calcium ions diffuse in and cause secretory vesicles to release insulin via exocytosis.
What part of the nervous system is heart rate controlled by?
Autonomic nervous system
Which part of the brain controls heart rate?
Medulla oblongata
The are two centres within the medulla oblongata that are linked to the SAN. What are the roles of the two centres?
One centre increases heart rate by sending impulses through the sympathetic nervous system, transmitted via accelerator nerve
One centre decreases heart rate by sending impulses through the parasympathetic nervous system transmitted by the vagus nerve
What are the two receptors that affect heart rate?
Baroreceptors
Chemoreceptors
What is the role of baroreceptors?
Detect changes in the blood pressure
Where are baroreceptors present?
Aorta
Vena cava
Carotid arteries
What is the role of chemoreceptors?
Detect changes in the levels of particular chemicals within the blood
Where are chemoreceptors located?
Aorta
Carotid artery
Medulla
Explain how exercise affects cardiac output
Increased metabolic activity
More carbon dioxide produced due to increased respiration
Blood pH is lowered
Centre in medulla oblongata that speeds heart rate increases the frequency of impulses to SAN via the sympathetic nervous system
SAN increases heart rate
Increased blood flow removes carbon dioxide faster
Carbon dioxide levels return to original levels
Explain what happens when blood pressure is too high
Impulses are sent to the medulla oblongata which decreases heart rate
Medulla oblongata sends impulses along parasympathetic neurones to SAN to decrease heart rate
Blood pressure returns to normal
Explain what happens when blood pressure is too low
Impulses are sent to the medulla oblongata centre which increases heart rate
Medulla sends impulses along sympathetic neurones to SAN which increases heart rate.
Increases blood pressure back to normal
Which two hormones affect heart rate in times of stress?
Adrenaline
Noradrenaline
How do hormones affect heart rate?
Affect pacemaker region of heart
Increase frequency of impulses produced in the SAN
