WEEK 4 - HOMEOSTASIS & ENDOCRINE Flashcards
Explain the stages of: Negative Feedback Loop
Stimulus -> Receptor -> Input along Afferent pathway (Approaching the CNS) -> Control Centre -> Output along Efferent pathway (Exiting CNS) -> Effector -> Response
Positive Feedback loop
Enhances, exaggerates the stimulus to cause variable to change in the same direction as original change e.g. blood clotting. Blood only starts coagulating (stopping positive feedback mechanism) when enough platelets have been released/attracted to allow clotting cascade to take effect
HYPOTHALAMUS
MASTER GLAND: Tells Pituitary gland what hormones to release
THYROID GLAND
Makes thyroid hormone. It’s involved in growth, development and metabolic rate
ADRENAL GLAND
Split into 2 parts that release hormones related to stress: aldosterone, adrenaline and cortisol
PITUITARY GLAND
Split into 2 parts that releases many hormones that: - either stimulate the production of other hormones or act directly on structures
PANCREAS
Releases: Insulin and Glucagon to regulate sugar levels
GONADS
Under control of hypothalamic and pituitary gland hormones. Female gonads: ovary - make oestrogen
Male gonads: testes - make testosterone
Both are responsible for body development and responsible for maintaining reproductive organs
TRUE or FALSE
Endocrine glands are ductless glands
TRUE
TRUE or FALSE
Hormones can bind to any receptor on target tissues to have an effect?
FALSE. Hormones must bind to specific receptors on target tissues to have an effect
ENDOCRINE SYSTEM
- Endocrine cells: release and produce hormones
- Hormones travel to act on distant parts of the body
- Hormones can take minutes to days to produce an effect
- Involved in the regulation of metabolic functions such as: stress adaptation and growth
5.Hormone effects can last hours, days, months or years
NERVOUS SYSTEM
- Neurons: release and produce neurotransmitters (NT)
- NTs act on tissue or another neuron next to it (via the synapse)
- NT’s produce their effects within milliseconds
- Involved in short term ‘crisis’ management
- NT effects are usually short lived
PEPTIDE HORMONES
Amino acid based protein hormone
- short lived,
- they signal via secondary messenger
- can’t dissolve in plasma so don’t need carriers
- hydrophilic or lipid insoluble
STERIOD HORMONES
Cholesterol based hormones
- live longer
- require proteins for transport in plasma
- hydrophobic or lipid soluble
POSTERIOR PITUITARY HORMONES
OXYTOCIN:
In uterus - initiates labour by stimulating uterine contractions
In breasts - initiates milk ejection
ANTIDIURETIC HORMONE (ADH)/VASOPRESSIN
- Stimulates kidneys to reabsorb water
- Concentrates urine, prevents further fluid loss
- Alcohol blocks ADH that’s why you urinate a lot when you’re drinking
ANTERIOR PITUITARY HORMONES
Thyroid Stimulating Hormone (TSH): secretes and stimulates thyroid hormone
Adrenocorticotrophic Hormone (ACTH): release of cortisol from adrenal cortex
Follicle Stimulating Hormone (FSH):
- in females: maturation of egg and production of oestrogen (ovary)
- in males: sperm production (testes)
Luteinizing Hormone (LH):
- in females: triggers ovulation
- in males: testosterone production
Growth Hormone (GH): stimulates growth, cell reproduction and cell regeneration
Prolactin (PRL): involved in regulation of fluids, reproductive (lactation), metabolic and immune functions
Name 2 thyroid hormones and what equation they create
Thyroxine (T4); Tri-iodothyronine (T3)
T3 + T4 = Thyroid Hormone (TH)
Why is IODINE necessary?
Iodine is necessary for the synthesis of TH because thyroid gland cannot store it
Name 5 functions of TH
- Increase Basal Metabolic Rate (BMR)
- Oxygen consumption
- Heat production
- Energy expenditure
- Necessary for CNS development, mental alertness and reflexes
HYPOTHYROIDISM (LOW TH)
- Reduced BMR
- No energy, feeling weak
- Cold intolerance, decrease in body temperature (always feeling chilly)
- Weight gain
- Poor mental function/memory
HYPERTHYROIDISM (HIGH TH)
- Increased BMR
- Restlessness/ hand tremor/ heart palpitations
- Heat tolerance
- Weight loss
- Hyperphagia (excessive sweating)
- Diarrhoea
GOITRE
- Enlarged thyroid gland
- Decreased iodine deficiency = decreased levels of TH = increased TRH and TSH (due to negative feedback), TSH gland keeps growing
