The Endocrine System Flashcards
Where does the sympathetic NS prioritise blood to in an emergency?
prioritises blood flow to brain, skeletal muscle, heart in emergency – skin vasoconstriction to minimise blood lose in injury, venoconstriction = increase cardiac return
Define endocrine
secrets hormones into the blood without ducts, wide spread, long lasting effects
Define neurocrine
neuron secrets substance into blood = hypothalamus, posterior pituitary, adrenal medulla
What are hormones and their main function ?
50 types, Control/regulate –> reproduction, metabolism, energy balance, growth/development, body defences, homeostasis. Can only trigger a reaction in specific cells = target cells with the right receptors, AA: cell membrane, steroid: intracellular. Hormone cascade: some hormones exist to control other hormones
What are the 2 main types of hormones, and where are their receptors?
AA (water soluble) or steroidal (lipid soluble). Protein hormone –> surface receptors. Steroid hormone –> intracellular receptors
What is a gland?
any structure that makes and secrets a hormone
What is the thymus?
Atrophy in teens. Function –> maturation of bone marrow dervied stem cells into T cells = thymic education. Prod thymosin = promotes T cell maturation
What is the pituitary?
Pea-sized structure located at base of the brain, just below hypothalamus, 2 lobes = anterior blood attachment, posterior nerve attachment
Describe the posterior pituitary
Connected by neurones, prod: oxytocin, ADH – both prod in hypo, travel neuronal axons, secreted to capillaries
Describe the anterior pituitary
Connect via blood supply, Prod: FSH= regulate growth and trigger sexual maturity, ACTH (adrenocorticotropic), TSH, LH, GW, prolactin
What is the thyroid gland?
Hypothalamic-pituitary-thyroid axis = thyroid gland prod thyroxin T3 T4 = -ve feedback loop on hypothalamus and anterior pit = anterior pit prod TSH, thyroid stim hormone. Controls metabolic rate
What are adrenal glands?
On top of kidneys. Adrenal cortical hormones = glucocorticoids (cortisol) mineralocorticoids (aldosterone)
Outline the HPA axis
hypothalamic release of corticotropin-releasing hormone (CRH). CRH binds to CRH receptors on anterior pituitary gland, adrenocorticotropic hormone (ACTH) is released. ACTH binds receptors on adrenal cortex and stimulates adrenal release of cortisol. Short/long –ve feedback from cortisol to AP and hypo
What are chromaffin cells?
Central = medulla = contains chromaffin cells (modified neurons) – nerve impulse = release adrenaline and noradrenaline –> considered neurocrine because chromaffin cells are considered the equivalent of postsynaptic neurones
What does the pancreas secrete?
BETA cells: Insulin. ALPHA cells: glucagon = regulates blood sugar
What is the pineal gland?
Prod melatonin = control of circadian rhythm (light exposure limits release – neuronal pathway from retina to hypo to pineal gland), inhibits LH, FSH. Calcifies in early adulthood
What is the function of the hypothalamus?
Thermoregulation, plasma osmolality, heart rate, BP, feeding, GIT regulation, circadian rhythms, wakefulness/sleep, lactation. PRODUCE: ADH + oxytocin: travel to posterior pituitary. Part of hypothalamo-hypophyseal portal system
