Endocrinology Flashcards
What do the endocrine system control and integrate ?
processes such as:
- reproduction
- growth and development
- maintenance of electrolyte, water and nutrient balance of the blood
- regulation of cellular metabolism and energy balance
- mobilisation of body defenses
What is the main signal in the endocrine system?
hormone
What do endocrine glands do?
secrete hormones into the systemic circulation
how are hormones secreted?
via specialised organs called endocrine glands
Where are the hormones secreted to?
the blood to a tissue where they have a specific action
What is a hormone?
a chemical substance which is secreted by specialised endocrine cells directly into the blood to exert an effect on distant target cells to bring about specfic changes in cellular function.
What are the target cells?
Can be local
referred to as paracrines or autocrines
What are the 2 types which hormones are made of?
Amino acid based
Lipid based- steroid based hormones
What are the amino acid based hormones?
- Polypeptides (large)- long chain
- not able to pass through plasma membrane through diffusion- have to use specialised proteins/channels within plasma membrane
- water soluble - as they are protein based
- most common e.g TRH, TSH, insulin, glucagon
What are the modified amino acid based hormones?
-small
-still cannot pass though plasma membranes by diffusion
water soluble
e.g thyroxine
What are the steroid/lipid based hormones?
- synthesised by cholesterol
- small, fat soluble - can pass through the plasma membrane by diffusion- as they can pass through that hydrophobic region
e. g. cortisol, oestrogen, testosterone
Whta re the stimulus for these hormones to be released to maintain homeostasis?
- 3 types of stimuli- regulating endocrine system
- Humoral stimulus
- Neural stimulus
- hormonal stimulus
What is the humoral stimulus?
- Hormone release caused by altered levels of certain critical ions or nutrients
- these glands are constantly monitoring levels of ions and nutrients in systemic circulation
- endocrine glands sense if the levels are high or low and then will sense and respond by secreting a hormone
- Which will exert an effect on another gland in the body to change the uptake or excrete the ions/nutrients to regulate the level in the blood.
What is neural stimulus?
hormone release caused by neural input
- stimulated by nervous system
- Stimulus: action potential in preganaglionic sympathetic fibres to adrenal medulla
- response- regulate secretion of adrenaline by adrenal medulla cells
What is hormonal stimulation?
hormone release caused by another hormone
- stimulus- hormones from hypothalamus
- endocrine glands regulated by hormones
- response- pituitary gland secretes hormones that stimulate other endocrine glands to secrete hormones
How is hormone release regulated?
Negative feedback
Example of a negative feedback - homeostasis
hormonal stimulation
Gland A- secrete hormone A in blood stream
Hormone A - have effect on glsnd B
Gland B - release hormone B
-Hormone B - some used by a target organ (where it is neeeded)-Low levels of hormone B
-Again gland A stimulated- REPEAT process
-When too much hormone B- it inhibits secretion of it in gland A
What are the main endocrine glands in the body?
Pineal Pituitary- Growth/lactation/thyroid Thyroid- Metabolism Thymus- T-cell maturation Adrenal-stress response Pancreas-glucose metabolism Ovaries-ovulation Testis-spermatogenesis
What is pineal gland?
- Sits right in the middle of the brain
- regulate sleep wake cycle- info relayed through eyes- in retina have photoreceptor cells - nervous innervation through the retina
- Sends nervous innervation to pineal gland which secretes melatonin- peaks at night- causing drowsiness and lowers body temperature through neural stimulation
What does the hypothalamus do?
- receives input from higher brain centres- limbic system= detect emotional changes
- receive input from visceral and somatic sense via brain stem (everywhere else in body- respond to physical changes- neural stimulus from touch , temp to brain which relays info)
- The release hormones from the pituitary is regulated by different stimuli acting on the hypothalamus initially.- interaction into your endocrine system
- sends neurones into pituitary gland
What is optic chiasm?
- Bundles of nerves coming from back of eye ( optic nerve)
- cross middle line of brain
- sits directly above the pituitary gland
What is the hypothalamus?
part of CNS
- regulate pituitary and pineal gland- uses neuroendocrine system
- links the CNS to endocrine system
What is the pitutiary gland?
- lies close to optic nerves
- has a bony cup and grows upwards
- have 2 regions:
- anterior lobe
- posterior lobe
What does these 2 regions do?
secrete different hormones
and innervated differently by hypothalamus