What hormones does the anterior pituitary release?
LH - luteinizing hormone FSH- follicle stimulating hormone Prolactin GH- Growth hormone TSH - thyroid stimulating hormone ACTH- adrenocorticotropic hormone
What does the parathyroid gland do?
Regulation of calcium ion levels in body fluids
What does the pancreas do?
Secretes hormones regulating rate of glucose uptake and utilisation by body tissues (insulin & glucagon)
What hormones do the gonads secrete? (Testes & ovaries)
Testosterone
Oestrogen
Progesterone
How do cells communicate?
-Direct communication
Between adjacent cells via gap junctions eg. Cardiac muscle contraction
-Paracrine communication
Between nearby cells via extracellular fluid eg. Blood clotting
-Synaptic communication
Between adjacent cells via neurotransmitters
-Endocrine communication
Between distant cells/tissues via the bloodstream
What are the different types of hormones?
AMINO ACIDS DERIVATIVES
- thyroid hormones
- epinephrine, norepinephrine, dopamine (catecholamines)
PEPTIDE HORMONES
- 10-200 amino acids
- most hormones
LIPID DERIVATIVES
-steroids eg. Oestrogen, corticosteroids
What happens when a hormone reaches its target cell?
Receptors in plasma membrane
- peptide hormones & catecholamines are unable to cross the plasma membrane
- hormone does not enter target cell
- binding of hormone to receptor triggers a second messenger response inside the cell
Receptors inside the cell
- steroid hormones (lipid derivatives) & some small uncharged amino acid derivatives (thyroid hormone) can pass through plasma membrane
- binding of hormone to receptor inside the cell triggers a response
How does the hypothalamus direct control of the endocrine system?
- secretion of hormones that directly target organs
- release of regulatory hormones that control secretion of hormones from the pituitary gland
- autonomic neutrons that control secretion of hormones from the adrenal gland
What are the functions of the hypothalamus?
- production of hormones
- regulates eating/drinking behaviour
- controls body temperature
- regulates sleep/wake cycles
- regulates emotional & behavioural response
- control of autonomic nervous system
HYPOTHALAMUS
What are the hormones secreted that directly target organs?
Oxytocin (OXT)
Uterine contractions
Anti diuretic hormone (ADH)
Water retention & blood volume
HYPOTHALAMUS
Release of regulatory hormones that control secretions of hormones from the pituitary gland
TRH- thyrotropic releasing hormone CRH - corticotropin releasing hormone GnRH - gonadotropin releasing hormone GHRH- growth hormone releasing hormone GHIH- growth hormone inhibiting hormone PRH - prolactin releasing hormone PIH- prolactin inhibiting hormone
HYPOTHALAMUS
Autonomic neutrons that control secretion of hormones from the adrenal gland
Epinephrine
Norepinephrine
How is communication between the hypothalamus and the endocrine glands maintained?
The regulatory hormones secreted by the hypothalamus enter the hypophyseal portal system.
Hypophyseal portal system of capillaries that efficiently transports hormones from the hypothalamus to the anterior pituitary gland.
Negative feedback control rate of hormone secretion.
What is the pituitary gland?
Divided in to 2 lobes.
ANTERIOR LOBE
stimulated by tropic hormones from the hypothalamus
POSTERIOR LOBE
neural tissue that releases hormones produced in the hypothalamus
- neurosecretory cells
What hormones are secreted by the pituitary gland?
Oxytocin - uterine contractions Follicle stimulating hormone - sex hormones Thyroid stimulating hormone - thyroid ACTH - steroids Anti diuretic hormone - kidneys Growth hormone - growth Prolactin - mammary
What is the role of the human growth hormone?
- growth and repair
- tissue building
- protein synthesis
- fat mobilisation for use as fuel
- conserves glucose
- growth promoting effects mediated by somatomedins
How is the release of growth hormone controlled?
Negative feedback involving both releasing and inhibiting hormones.
From where is ADH released?
Secreted by the posterior pituitary gland
What is the function of ADH?
Assist with maintaining fluid balance & blood pressure
- decreases ruin production
- kidneys return blood to water
- decreases sweating
- causes constriction of arterioles
How is the release of ADH controlled?
- high blood osmotic pressure stimulates hypothalamic osmoreceptors
- osmoreceptors activate the neurosecretory cells that synthesise and release ADH
- nerve impulses liberate ADH from axon terminals in the posterior pituitary into the bloodstream
- kidneys retain more water, which decreases urine output
- low blood osmotic pressure inhibits hypothalamic osmoreceptors
- inhibition of osmoreceptors reduces or stops ADH secretion
Where is the thyroid gland?
Curves across the anterior surface of the trachea
What types of cells are found in the thyroid gland? What hormone are they responsible for?
Made up of follicles, which are hollow spheres surrounded by simple cuboidal epithelium.
Follicle cells produce thyroglobulin - a protein that contains the amino acid tyrosine.
Tyrosine is the building block for the thyroid hormones: triiodothyronine (T3) & thyroxine (T4)
C cells - produce calcitonin- released when blood calcium levels are too high
What are the functions of triiodothyronine (T3) & thyroxine (T4) ?
T3 & T4 are formed from tyrosine in the follicle cells.
Effects almost all cells:
- increases in BMR increase body temperature by stimulation of glucose oxidation
- effects fat metabolisation, protein synthesis & cholesterol synthesis by the liver
- increases number of adrenergic receptors in the blood vessels influencing blood pressure
- critical for normal growth - skeletal, nervous & reproductive tissue
- promotes normal muscle function, GI motility, reproduction
How is thyroid hormone secretion controlled?
- low blood levels of T3 & T4 or low metabolic rate stimulates release of thyroid releasing hormone
- TRH carried by hypophyseal portal veins to anterior pituitary stimulates release of TSH
- TSH released into blood stimulates thyroid follicular cells
- T3 & T4 released into blood by follicular cells
- elevated T3 inhibits release of TRH & TSH ( negative feedback)
