Endocrine Signalling Flashcards
(34 cards)
Homeostasis
Maintenance of a stable internal environment which is a dynamic process - constantly changing.
- blood ph - change in protein shape.
- blood volume - nutrients pumped around the body.
- blood soluble composition - urine.
- CO2 (and O2) - CO2 under very tight control as it binds with water and forms an acid.
- blood pressure
- blood glucose levels
- wast products
Negative feedback
Eliminate change from the set point - hypothalamus e.g send more blood to the skin to cool down.
Endotherms
Thermal regulators
Ectotherms
Cold blooded animals - Rely on their behaviour
Heat exhaustion
Body attempts to get rid of heat by sweating and increasing blood flow to the skin. As a result there is reduction in blood volume causing blood pressure, dizziness and floss of consciousness.
Heat stroke
Brain function affected due to overheating. Thermoregulatory centre begins to fail.
Positive feedback
Increases the divination from the set point. E.g response of the immune system, childbirth - stimulates oxytocin, ovulation - hormones from anterior pituitary gland.
Feedforward
Anticipates changes in the variable. E.g salivating.
What is a hormone?
‘A substance that is produced by one tissue and transported to another tissue where it induces a specific physiological response; animal hormones are produced by ductless glands of the endocrine system and pass into the blood’.
Autocrine signals
Travel through intercellular channels to affect cell of origin and/or neighbouring cells.
Paracrine signals
Molecular signals from one cell type, via intercellular, fluid filled channels, to neighbouring cell or cells.
Endocrine (hormones)
Endocrine glands secrete hormones (signals) from endocrine cells through the blood to distant targets cells. Not allowed into the brain!
Neurocrine
Signals released by neutrons into the blood, carried to near or distant cell(s).
Facts about hormones
- travel in the blood
- act via receptors in target cells
- receptors in cell membrane or cytoplasm
- feedback system for control
- same hormone can have different effects on different cells
Adrenaline (epinephrine)
- Present at low concentrations, binds primarily to beta2 receptors.
- at higher concentrations, binds to both alpha and beta2 type receptors
- alpha receptors cause vasoconstriction in the small arteries and arterioles.
- beta2 causes smooth muscle blood vesicles to vasodilation - relax, so more blood flow when the are high levels of adrenaline
Endocrine glands
- Pituitary
- thyroid
- adrenal
- stomach
- kidneys
- pancreas
- gonads
Pituitary
Posterior and anterior pituitary gland
- posterior produces: ADH (anti-diuretic hormone) - kidney tubules, oxytocin - mammary glands and uterus muscles
- anterior pituitary stimulated by neurosecretory cells:
- growth hormone - bones
- prolactin - mammary gland
- FSH and LH - gonads
- TSH - thyroid
- ACTH - adrenal cortex
- MSH - melanocytes
- endorphin - pain repressors
Tropic hormones
Have other endocrine glands as a target. Are controlled by the neurosecretory cells.
- TSH - thyroid stimulating hormone
- ACTH - adrenocortico-tropic hormone (corticotrophin) acts on cortex of adrenal gland
- FSH - follicle stimulating hormone, act on gonads
- LH - lutenizing hormone, act on gonads
Thyroid
Sits on the ventral side (towards stomach) and imbedded within it are the parathyroid glands (4 of 5).
Involved in calcium homeostasis - calcitonin; parathyroid hormone stops uptake of calcium when levels are
Bone marrow produces red blood cells and within the bones there are blood vessels, nerves, cells and collagen
Bones
Bone marrow produces red blood cells and within the bones there are blood vessels, nerves, cells and collagen
Osteoblasts - produce bones
Osteoclasts - break down bones that are used up
These sit in a matrix of collagen fibres and salts: phosphate and calcium - like reinforced concrete
Thyroid and parathyroid with calcium homeostasis
- blood calcium levels low - parathyroid hormone, oppose the actions of calcitonin and causes the uptake of more calcium from the filtrate, and causes release of calcium from the bones.
- blood calcium levels high - thyroid gland gets stimulated with calcitonin, causes calcium to be taken into the bones and makes the kidneys not take up as much calcium from the filtrate
Vitamin D and calcium
- hypercalcemia (to much calcium) - lead to muscle weakness.
- hypocalcemia - tingling and nerve contraction problems
- fit. D stored in live (lipid soluble) - function: interacts with gene expression which binds proteins and can facilitate the calcium pathways. Crucial for bone formation.
Adrenal gland
- medulla (inside) - responds to neural input - produces adrenaline and noradrenaline
- cortex (outside) - responds to hormone input - produces hormones collectively called adrenocorticoids.
- ACTH activate glucocorticoids, which are involved in dampening the immune system/inflammation.
Growth hormone
Lack of this can cause pituitary dwarfism
