Outcome 4 Endocrine System Flashcards
Endocrine glands secrete _____ into the _____.
Endocrine glands secrete CHEMICALS (HORMONES) into the BLOOD
What do hormones do?
Perform general functions of communication and control but a SLOWER, LONGER-LASTING type of control than that provided by nerve impulses
Cells acted on by hormones are called ____ found within ____
Cells acted on by hormones are called TARGET CELLS found within TARGET ORGANS
Hormone secretion is controlled by _____
Homeostatic feedback
Negative feedback
Mechanisms or loops that reverse the direction of a change in a physiological system back towards a normal value. Allows the brain and body to have control over the secretion rates of hormones.
Ex: an increase in blood glucose triggers secretion of insulin. Because insulin promotes glucose uptake by the cells, the blood glucose level is restored it’s lower, normal level
Positive feedback
(Uncommon) mechanisms that amplify the physiological changes
Major hormones in the anterior pituitary
TSH- thyroid stimulating hormone
GH- growth hormone
ACTH- adrenocorticotropic hormone (stimulates the adrenal glands)
Major hormone of the posterior pituitary
ADH-antidiuretic hormone (stops you from producing urine so you pee less. It causes the kidney to conserve water)
Homeostasis
RELATIVE CONSTANCY OF INTERNAL ENVIRONMENT. The temp, salt content, acid level (PH), fluid volume and pressure, oxygen concentration, and over vital conditions must remain within acceptable limits
Endocrine glands
DUCTLESS GLANDS made up of cells that produce and release chemicals known as hormones into the INTERCELLULAR SPACES of surrounding tissues. The hormones are quickly picked up by the blood stream and distributed to target organs and cells
Exocrine glands
Collections of glandular tissue within an organ that produce and release NON-HORMONAL substances INTO DUCTS that empty onto a surface or into a cavity. EX sweat glands, salivary glands
Target cell
Each hormone molecule may bind to a cell that has specific receptors for that hormone, triggering a reaction in the cell
Electrolytes
Substances such as salts that dissolve or break apart in water solution to form electrically charged atoms (or groups of atoms) called ions
Electrolyte balance
Homeostasis or relative constancy of normal electrolyte levels in the body fluids
The ability to maintain the balance of body functions is related to ____
AGE! During childhood, homeostatic functions gradually become more and more efficient and effective. They operate with max efficiency and effectiveness during young adulthood. During late adulthood and old age they gradually become less and less efficient and effective
Pineal gland
- attached to the roof of the 3rd ventricle in the center of the brain (part of the diencephalon)
- contains calcium salts (brain sand) that can be seen on radiographic images especially CT
- pine cone shaped
- secretes the hormone melatonin -> helps set the body’s biological clock, by regulating sleep/wake patterns
- uses info regarding changing light levels to adjust its levels of melatonin
- melatonin levels INCREASE at night and DECREASE during the day
- easily located in a child but becomes fibrous and encrusted with calcium deposits as a person ages
- SAD -> seasonal affective disorder
Pituitary gland
- attached inferiorly to the hypothalamus by a stem-like structure
- located in the sella tursica
- encased in dura mater, and surrounded by the circle of Willis
- size and shape of a pea
- made up of an anterior and posterior portion
Posterior pituitary
- cellular structure similar to nervous tissue
- does not manufacture any hormones
- it STORES two hormones made by the Hypothalamus
- only one is pertinent in radiography ADH-> anti diuretic hormone
ADH- antidiuretic hormone
- Stops you from producing urine so you “pee” less. It causes the kidneys to conserve water
- stored in the posterior pituitary
- made by hypothalamus
Thymus
- located in mediastinum
- composed largely of lymphocytes
- plays a critical part in the body’s defences against infections -> vital immunity mechanism
Anterior pituitary
- cellular structure of a true endocrine gland
- manufactures 6 hormones only 3 are pertinent to radiography
- TSH -> thyroid stimulating hormone
- GH -> growth hormone
- ACTH -> adrenocorticotropic hormone (stimulates the adrenal glands)
Hyperpituitarism
- can cause over production of hormones
- BEFORE the fusion of growth plates will cause GIANTISM
- AFTER the fusion of growth plates will cause ACROMEGALY
Hypo-pituitarism is usually due to a _____ or _____
- Pituitary tumour or pituitary ischemia
- diagnosed with CT, MRI or Angio
- treated with hormone replacement
Hypopituitarism can cause ____
Achondroplasia
Achondroplasia if a congenital disease
- sign of this if you are a dwarf (normal trunk but short limbs, 4ft tall, protruding buttock)
- a common cause of dwarfism
- genetic condition that prevents cartilage in the epiphyses from converting to bone
- widening at the distal end of the long bone shafts (trumpeting)
Achondroplasia if had a tumour on the pituitary
- wouldn’t look like the classic “dwarf” they would have normal body proportions but are just short
- could take growth hormones sub dermally to treat this
Parathyroids
- usually 4 of them
- tiny yellow/brown glands located on posterior surface of thyroid
- secrete Parathyroid hormone (PTH) -> increases blood calcium levels by stimulating osteoclasts (bone absorbing cells) to breakdown bony matrix, thereby freeing calcium and phosphorus
- maintaining blood calcium at homeostatic levels is a matter of life and death
Parathyroid hormone (PTH)
- increases the concentration of calcium in the blood
- stimulates bone resorbing cells or osteoclasts to increase their breakdown of bones hard matrix, a process that frees the calcium stored in the matrix
- released calcium then moves out of the bone into the blood -> increasing bloods calcium concentration
Too much calcium in the blood
- Brain and heart cells soon do not function normally
- person becomes mentally disturbed
- heart stops altogether
Too little blood calcium
- nerve cells become overactive
- sometimes bombard muscles with so many impulses that the muscles go into spasms
Thyroid gland
- butterfly shaped
- located on anterior side of neck, sits anterior to trachea, inferior to larynx
- not located in a body cavity
- isthmus connects two lateral lobes
- stores and secretes thyroid hormone (TH) and calcitonin
Thyroid hormone (TH)
- production and release controlled through the negative feedback loop
- iodine is a key ingredient -> limited iodine in diet means thyroid gland cannot produce functional TH which causes feedback loop to fail: target cells do not receive functioning TH so they cannot, in turn, produce chemical inhibitors that stop the hypothalamus and pituitary glands from releasing more TSH
- speeds up cellular metabolism -> increased level of energy
- used to increase body temp, maintain BP, regulate tissue growth and development
Calcitonin
Hormone that decreases blood calcium levels
Hyperthyroidism
- Graves disease is most common cause ->hereditary autoimmune disease where the body produces antibodies that mimic TSH so TH is continuously released into the bloodstream
- protruding eyeballs (exophthalmos), edema in soft tissue posterior to the eyes
- can be triggered by smoking, stress, radiation to the neck, medications and viruses, thyroid neoplasms
Hypothyroidism
Hashimotos disease
- under secretion of thyroid hormones
- diet missing iodine
- sleepy, skin gets thick and flaky
- can cause a goiter or a condition called myxedema (mucous swelling), edema around the eyes and facial swelling
- the gland enlarges in an attempt to compensate for the lack of iodine in the diet necessary for the synthesis of TH
Cretinism
- lack of iodine to the fetus
- congenital hypothyroidism caused by low thyroid during fetal development
- short in stature; course features with protruding tongue, board flattened nose, widely set eyes
- on x-rays there is an absence of epiphyseal plate on femur and tibia
- increased thickness of skull
- must be treated within 3 months of age to avoid long term effects
Adrenal glands
- pyramid shaped glands perched on superior end of kidneys (visible on CT)
- often called “supra renal glands”
- like “two glands in one” because the cortex secretes different hormones than the medulla
- all adrenal hormones help us deal with stress!!
- epinephrine, norepinephrine, cortisol (glucocorticoid)
Epinephrine and norepinephrine
- direct nervous stimulation from the sympathetic nervous system causes the ADRENAL MEDULLA to immediately “dump” epinephrine and norepinephrine into the blood stream
- initiates powerful “fight or flight” mechanism
- RAPID INCREASE in BP, heart rate, blood sugar level and immediate diversion of blood to skeletal muscles
- allows us to effectively deal with a short term threat ex swarm of killer bees
Cortisol
- when stimulated by the ACTH from the anterior pituitary glad the adrenal cortex produces the glucocorticoid cortisol
- has 3 effects on the body
1) INCREASES blood sugar levels by increasing normal metabolic processes associated with glucogenesis. Helps the body deal with daily metabolic stressors related to changing routines or lifestyle choices. Ex cortisol will maintain blood sugar levels in the event you skip breakfast
2) suppresses the immune system
3) has an anti-inflammatory/ anti-allergic effect - under severe stress cortisol output increases
Cushing’s syndrome
- most often caused iatrogenically (no know cause) by steroidal drug therapies (ex prednisone) but may also be caused by pituitary and adrenal pathologies
- classic symptoms “moon face” and “Buffalo hump”
- H20 and salt retention, loss of bone and muscle mass-> eventually end up bed ridden
- chronic hyperglycemia
- intense anti-inflammatory effects can cause severe infections to go unnoticed
Pancreatic islets
- (islets of Lagerhans) clusters of 2 different types of hormone producing cells that work against each other to maintain blood sugar levels
1) alpha cells ->glucagon (hyperglycemic hormone)
2) beta cells -> insulin (hypogylcemic hormone)