Module 5: Principles of Endocrinology Flashcards
List the 5 types of cell signalling
- Endocrine signalling
- Synaptic signalling
- Neuroendocrine signalling
- Paracrine signalling
- Autocrine signalling
Describe Endocrine signalling
- long distance signalling
- secrete molecules (hormones) diffuse into the blood stream, circulate, and trigger responses in target cells anywhere in the body
Describe Synaptic signalling
- local signalling
- secreted molecules (neurotransmitters) diffuse across a synapse, triggering a response in cells of the targeted tissue
Describe Neuroendocrine signalling
- long distance signalling
- secreted molecules (neurohormones, e.g. oxytocin) diffuse into the blood stream, circulate, and trigger responses in target cells anywhere in the body
Describe Paracrine signalling
- local signalling
- secreted molecules (local regulators) diffuse locally through the extracellular fluid, triggering a response in neighbouring cells
Describe Autocrine signalling
- local signalling
- secreted molecules (local regulators) diffuse locally, triggering a response in the cell which secreted them
List/ describe the two ways that animals manage their internal environment
- Regulating their internal environment despite external fluctuation: e.g. humans
- Allowing internal condition to conform to the external environment: e.g. reptiles (snakes, turtles)
List the 4 ways in which organisms regulate and maintain homeostasis
- Ectothermic vs. endothermic organisms
- Organisms use homeostasis to maintain a steady state or internal balance: independent of conditions in the external environment
- Hormones
- Types of hormones
Discuss 4 components of hormones
- one of the modes of long distance communication in animals
- endocrine cells in various organs and tissues release hormones into the blood stream
- these messengers send signals to cells
- specificity in receptors, specificity in binding
Discuss 3 components of types of hormones
- Water soluble (hydrophilic)
- polypeptides: insulin
- adrenaline: amine - Lipid soluble (hydrophobic)
- steroids: cortisol
- thyroxine/thyroid hormone: amine - Receptor location varies with hormone type
- water soluble hormones must be carried within a vesicle and have a receptor protein, but are free in the blood
- lipid soluble hormones are free in the cytoplasm and have a receptor protein on the nucleus, but must be carried on a transport protein in the blood
List 3 components of hormone uses
- Hormones have multiple effects in different target cells and species
- Feedback mechanisms
- Homeostasis with antagonistic hormones
Discuss in detail how: hormones have multiple effects in different target cells and species
- thyroid hormones (e.g thyroxin) regulate homeostasis and development
- adrenaline (fight or flight)
~in a liver cell (beta) blood glucose levels increase
~in a smooth muscle cell for skeletal muscle (beta), relaxes cell to dilate blood flow
~in a smooth muscle cell for intestines (alpha), contracts cell to constrict blood flow
Discuss in detail: feedback mechanisms
- positive feedback: response reinforces stimulus, e.g. uterine contraction in birth
- negative feedback: response reduces response to stimulus
Discuss in detail: homeostasis with antagonistic hormones
- insulin vs. glucose in response to blood glucose levels rising/ falling (respectively) beta/alpha cells in pancreas: types 1 and 2 diabetes
- homeostasis by RAAS (Renin-Angiotensin-Aldosterone System)
List the 5 steps of homeostasis by RAAS for blood pressure
- Blood pressure/volume drops
- JGA detects decrease
- JGA releases enzyme Renin
- Liver releases Angiotensinogen - Combines to form hormone Angiotensin 1
- Via ACE to Angiotensin 2
- Arterioles constrict, increases blood pressure
- Signals adrenal gland to produce aldosterone: Na+ and H20 are reabsorbed in distal tubules, increase blood volume - Normal blood pressure and volume
List the 4 types of major human endocrine glands
- Hypothalamus
- Pituitary gland
- Organs containing endocrine cells
- pancreas
- kidney
- ovaries/testes
- thymus
- heart
- liver
- stomach
- small intestine - Other glands
- pineal gland
- thyroid gland
- parathyroid glands (behind thyroid)
- adrenal glands (atop kidneys)
Discuss 3 points with regards to endocrine glands in the human brain
- the pineal gland is located above the cerebellum
- the hypothalamus is located below the thalamus which is below the cerebrum
- the posterior and anterior pituitary are located below the hypothalamus
List 3 overarching points with regards to posterior pituitary hormones
- Neurosecretory cells of the hypothalamus send neurohormones down axons to the posterior pituitary
- ADH (anti-diuretic hormone, aka. Vasopressin) (diuresis: increased urination)
- Diabetes insipidus
Discuss in detail how: Neurosecretory cells of the hypothalamus send neurohormones down axons to the posterior pituitary
- ADH is sent to the kidney tubules (anti-diuretic hormone controls water re-uptake in kidneys)
- Oxytocin is sent to mammary glands and uterine muscles
Discuss in detail: ADH
- osmoregulation is the control of solute concentration in body fluids, especially blood plasma
~osmoreceptors in the hypothalamus triggers release of ADH
~It also generates thirst
~Normal blood osmolarity = 300 mOsm/L - if water content of blood is too low, the posterior pituitary gland secretes anti-diuretic hormone (ADH) or vasopressin
- the cells of the collecting duct increase permeability of the plasma membrane to water
~They put water channels called aquaporins into their membranes
~As the filtrate passes down the collecting duct through the medulla the high solute concentration causes much of the water in the filtrate to be reabsorbed by osmosis
~a small quantity of concentrated urine is then produced - if the solute concentration is too low, ADH is not secreted and the collecting duct becomes less permeable
~once osmolarity is back to homeostatic set point
~negative feedback loop operates at the hypothalamic level reducing ADH production - ADH is a short polypeptide hormone (water soluble)
- Cell signalling mechanisms
Discuss in detail: Diabetes Insipidus
- mutations that prevent ADH production cause diabetes insipidus (“to pass through”)
- mutations in aquaporin genes can also cause DI
- consequences
~severe dehydration
~solute imbalances due to increased (dilute) urine volume - not always genetic
~ alcohol can also inhibit ADH release
~excess urine and dehydration causes ‘hangover’
Discuss 2 points with regards to Anterior pituitary hormones
- the anterior pituitary gland is pink in colour due to portal vessels and a large coverage of capillaries. It is not directly connected to the hypothalamus
- releases lots of hormones
List/describe the 3 types of anterior pituitary hormones
- Tropic (targets other endocrine glands)
- FSH, LH (gonadotropins)
- TSH (thyroid stimulating hormone)
- ACTH (adrenocorticotropic hormone) - Nontropic
- Prolactin (lactation in mammals, other uses in other animals)
- MSH (melanocyte stimulating hormone, also inhibits hunger) - Both
- GH (growth hormone)
Complete the GOATFLAPM: all hormones table
Acrostic : Hormone Name : Where Produced : Tropic
G : GH : Anterior : Both
O : Oxytocin : Posterior : No
A : ADH : Post : Yes
T : TSH : Ant : Yes
F : FSH : Ant : Yes
L : LH : Ant : Yes
A : ACTH : Ant : Yes
P : Prolactin : Ant : No
M : MSH : Ant : No
