Endocrine Physiology Flashcards
What are the 2 parts of the pituitary?
Anterior
Posterior
What is the difference between the posterior and anterior pituitary?
Anterior contains true endocrine cells
Posterior similar to brain tissue because it contains many neurons
What is the infundibulum?
The stock/ stem that attaches the pituitary to the hypothalamus
Where are neurohormones made?
Made in the hypothalamus (rough ER)
What is the pathway of neurons through the thalamus to the posterior pituitary?
Cell bodies and dendrites of neurons are in the hypothalamus, and the axon travels down the infundibulum and axon terminals are in the posterior pituitary
How are neurohormones released?
Signal comes from the thalamus when there is an action potential it is sent down the axon and are stored in axon terminals which are incontac with the capillaries and released into the blood
How does the hypothalamus communicate with the anterior pituitary?
Through capillary beds
Hormones are released in the hypothalamus and anterior pituitary, but what happens when the hormone gets to the target cell/tissue?
Once the signal is released and at the target cell/tissue, that target will release a third hormone which is apart of a negative feedback loop which will signal the hypothalamus to stop producing the initial hormone which will cause hormone 2 and 3 to stop producing.
What are the 2 things the posterior pituitary releases?
2 Peptide Hormones
- Oxytocin
- Antidiuretic
both produced in the hypothalamus
Why is oxytocin important?
Promotes uterine contractions during labour as well as milk excretion
-in both sexes
What is Antidiuretic Hormone (ADH)?
Also know as Vasopressin
-Hormone that acts on specific regions of the kidney tubules to conserve water by allowing reabsorption of water back into the blood
What does ADH affect?
Blood pressure, since blood will be in a low blood volume state= low blood pressure
Where would you find vasopressin receptors to belated on the plasma membrane of kidney cells
Surface receptors
What are the consequences of a mutated ADH receptor?
- Diabetes insipidus
- lack of ADH or mutated receptors (aka receptors aren’t working)
- cant be fixed
What happens when a hormone binds a membrane-bound receptor?
It must trigger an intracellular event in the target cell to alter its function
How do you get a target cell to alter its function?
Receptor may activate a G-protein, affect intracellular enzymes or alter the function of an ion channel
What happens when a hormone binds a intracellular receptor?
It may change the transcription of genes, causing an increase or suppression in protein synthesis
What are some of the hormones synthesized and released from the anterior pituitary?
Luteinizing Hormone (LH) Follicle Stimulating Hormone Thyroid Stimulating Hormone (TSH) Adrenocorticotropic Hormone (ACTH) Growth Hormone (GH) Prolactin
When do endocrine cells in the pituitary know when to release hormones?
When it is singled from the hypothalamus
What are the hormones released from the Hypothalamus?
Gonadotropin Releasing Hormone (GnRH) Thyrotropin Releasing Hormone (TRH) Corticotropin Releasing Hormone (CRH) Growth Hormone Releasing Hormone (GH) Dopamine
What is special about Dopamine and Prolactin?
Dopamine is inhibitory and stops the release of prolactin
Prolactin is not released when dopamine is present
What does LH/FSH act on?
Gonads
What does TSH act on?
Thyroid glands
What does ACTH act on?
Adrenal Glands
What does GH act on?
Bone
Skeletal Muscle
Liver
Adipose Tissue
What does Prolactin act on?
Mamary Glands
What and where is the Thyroid Gland?
One of the largest endocrine gland, butterfly shape
Located in the lower neck region just below the larynx
What happens to the thyroid when it isn’t functioning properly?
Can increase or decrease depending on what is happening
What does the thyroid produce?
Hormones that act on most of the cells in your body to influence metabolic rate
What surrounds the network of capillaries in the thyroid?
Individual units called follicles
Why are thyroid follicles important?
Hormones produced by the thyroid are made in these follicles
What is the colloid?
Stores the thyroid hormones and the site of production
How do thyroid hormones leave the colloid?
When thyroid hormones are done being made they go in the capillaries to be circulated in the blood
What are the 2 thyroid hormones that are made in the follicles?
Thyroxine (Tetraiodothyronine) T4
Triiodothyronine T3
What are the building blocks of T3 and T4?
2 Tyrosine and iodide is added
Where do we get iodide to make T3 and T4?
Comes from our diets
Where do we find tyrosine to make T3 and T4?
Found on a target protein called Thyroglobulin (almost half of thyroglobulin is tyrosine)
T4 Characteristics?
- Less potent
- Not active
- More abundant
- There when you need it to make T3
T3 Characteristics?
- More potent
- Does most of the work
- Dont require much for metabolism to increase
Specifically where are T3 and T4?
Hormones are actually made outside the follicular cells and inside the colloid of the follicle
-tyrosine and iodide have to be transported into the colloid
What are the symptoms of hyperthyroidism?
(Too much) Lower body mass Higher temp Lose weight Hungrier Increased heart weight More fat released as energy Fidgety, hypertensive and irritable
Causes of hyperthyroidism?
Increase in protein production which causes more emzymes to be around which increases the rates of reactions. This causes the body to make more ATP while using more O2
How do you treat hyperthyroidism
Removing thyroid
Radioactive iodine–> treats goiders by going in and causing degradation of the thyroid
What are symptoms of hypothyroidism?
(Too little) Slow heart rate Sensitive to cold Weight gain Fatigue and depression
Cause of hypothyroidism?
Not getting enough iodine. Body response is to increase TRH and TSH but we don’t have the iodine from our diet to make the T3 and T4
How do you treat hypothyroidism?
Pills for synthetic T4
Where is the adrenal gland?
On top of the kidneys
What are the 2 regions of the adrenal gland?
Cortex and inner medulla
Which of the 2 adrenal cortex regions are further divided and into how many?
Adrenal cortex is further subdivided into 3 layers
What are the 3 layers of the adrenal cortex
Zona Glomerulosa
Zona Fasiculata
Zona Reticularis
What are the 3 layers of the adrenal cortex
Zona Glomerulosa
Zona Fasiculata
Zona Reticularis
What do each adrenal cortex do?
Make specific steroid hormones for each layer
-depends on the enzymes in the layer
What hormone is made in the Zona Glomerulosa?
Aldosterone
What hormone is made in the Zone Fasiculata?
Cortisol
What hormone is made in the Zone Reticularis?
Androgens
What is cortisol production and secretion regulated by?
Through the hypothalamic-pituitary-adrenal-axis
What is cortisol “street name”?
Stress hormone
What is released in response to stress (physical or emotional stress)?
Corticotropin releasing hormone (CRH)
What is the cycle of cortisol levels in the body?
Flux’s throughout the day, highest in the morning to help you cope with the stress of the day.
Flows along with your circadian rhythm
How does cortisol effect muscle?
Through protein catabolism
proteins –> amino acids
effects on the bone
How does cortisol effect the liver?
Through gluconeogenesis
- signals the liver to make new glucose out of things that aren’t glucose like glycerol or amino acids
- glucose is put in the blood raising blood glucose levels fuel your brain
- becasue when you are stressed you want to be able to think properly with enough food going to feed you brain
How does cortisol effect adipose tissue?
Through Lipolysis
-Fat tissue breaks down triglycerides into glycerol and fatty acids
How does cortisol effect Immune system?
Through Immune suppression
- When cortisol is release it surpasses the body reaction to things, like skin breakouts
- cant fight of infections as easily
What cells will cortisol impact?
Nearly all cells will have receptors inside the cell because it is a steroid protein
If cortisol levels are too high for too long what can that result in?
Osteoporosis
-bone breakdown
Why is cortisol considered catabolic?
- It breaks down large macromolecules
- Causes enzymes to be produced and speed up processes of breaking down amino acids
- Needs amino acids to repair things
What is Cushings Disease?
Named after physicians who found it
-Hypercortisolism (to much cortisol)
What are symptoms of Cushings?
High blood sugar Muscle wasting/weakness Stretchmarks Stunted growth Osteoperosis Excessive fat break down in limbs but accumulation in abdomen Increased infection rate
How to treat Cushings?
Try to keep cortisol as low and as local as possible (puffer, cream)
When you take a pill it goes through your whole system
What is aldosterone?
Mineralocorticoid hormone
What does aldosterone do?
Act on kidneys to put Na+ back into the blood by making new protein channels and Na+/K+ pumps
Why do we want aldosterone to put Na+ back into the blood?
When there is Na+ water follows
how does aldosterone get released?
Usually released in response to ACTH, but it is often secreted when stimulated by angiotensin II which originated in the RAAS (Renin-aniotensin-aldosterone-system) not in the hypothalamus.
When is the RAAS pathway unregulated?
When blood pressure is low in order to reabsorb Na+ from areas in the kidney tubules and return it to the blood
What is aldosterone also stimulated by?
Increased levels of blood K+
What effect does K+ have on kidneys?
K+ is secreted into the kidney tubules by increasing the number of K+ ATPase pumps
What is the adrenal medulla?
Hydrophilic center of the adrenal gland
Which chemical does the adrenal medulla release?
Epinephrin (Catecholamine), Norepinephrin and Dopamine
What triggers the release of epinephrin?
The sympathetic nervous system signals the chromatin cells of the adrenal medulla to release epinephrin into the blood stream
-immediate response to stress causing you to flee
What are some effects of increased epinephrin in the body?
increased gluconeogenesis
increased heart rate
relaxes lung airways
increase blood pressure by constricting blood vessels
What hormones does the pancreas release?
Insulin and glucagon
Why does the pancreas release the 2 hormones?
to regulate blood glucose
Where are the 2 pancreas hormones produced?
In the islets of langerhans
What are islet cells?
islets are endocrine cells that are a mix of alpha and beta cells within the islets
What do islet alpha cells produce?
Glucagon
What is the trigger for releasing glucagon?
Low blood sugar tells cells to release glucose into the bloodstream
What do islet beta cells produce?
Insulin is produced and released here
What is the trigger for releasing insulin?
When blood sugar is too high it signals target cells to take up glucose so its not in the blood
