Gianfilippo Ruggiero and Emma Wakefield H.1: Hormonal Control Gianfilippo Ruggiero and Emma Wakefield

H.1.1: State that hormones are chemical messengers secreted by endocrine glands into the blood and transported to specific target cells

H.1.1 Endocrine glands produce and secrete hormones. Hormones are chemical messengers. They cause a physiological effect far from their gland origin. Hormones are transported throughout the body by transport of the blood stream. Target cells: are the cells affected by a hormone. Most hormones are under the control of a negative feedback mechanism, however there are exceptions like oxytocin, whose secretion is controlled by a positive feedback.

H.1.2: State that hormones can be steroids, proteins and tyrosine derivate, with one example each

H.1.2: Hormones and Their Action

H.1.3: Distinguish between the mode of action of steroid hormones and protein hormones

H.1.3: Mode of Action of Steroid Hormones Steroid H are typically synthesized by cholesterol: Therefore they are classified as lipids A cell membrane is made up of a double layer of phospholipids, meaning that Steroid H can pass through it. In the cytoplasm, it binds to a receptor protein: Forms a hormone-protein complex The complex passes through the membrane to bind with certain genes It can inhibit or induce protein transcription so that the steroid H can control the protein production of the target cell

H.1.3: Mode of Action of Peptide Hormones Cannot go through the membrane, so it binds with a receptor protein Create a receptor-hormone complex Once they are bonded to the receptor proteins, peptide H send a secondary messenger in the cytoplasm of the cell This second messenger can alter the actions of the cell

H.1.4: Outline the relationship between the hypothalamus and the pituitary gland.

H.1.4: Where are the hypothalamus and pituitary glands?

H.1.4: Pituitary gland is controlled by the hypothalamus The hypothalamus connects the cerebral hemispheres with the middle portion of the brain. The hypothalamus has many receptors for changes of internal conditions and serves as a link between the nervous system and the endocrine system (pituitary). Below the hypothalamus is a double lobed structure called the pituitary that produces the endocrine secretions when stimulated by the hypothalamus. Pituitary gland is often referred to as the ‘Master gland’ as it releases a wide variety of hormones However the secretion is controlled by the hypothalamus. Pituitary glands have two lobes: Posterior and anterior Communicate with the Hypothalamus in different ways

H.1.4: Posterior lobe communication Contains axons of cells called neurosecretory cells. Very long cells: Dendrites and cell bodies in the hypothalamus Axons in the posterior pituitary. Many hormones are produced at the cell body of these cells: Then move down the cells to the posterior pituitary Hormones are produce in the hypothalamus but secreted from the posterior pituitary Oxytocin

H.1.4: Anterior lobe communication Hypothalamus contains capillary beds: Secretes produced hormones in the capillary ‘Releasing Hormones’ – gonadotrophin releasing hormone (GnRH) Capillaries join together forming the portal vein Extends until anterior pituitary Branches out into another capillary bed, which allows the releasing hormones to diffuse into the anterior pituitary cells This causes the anterior pituitary to produce other hormones GnHR caused production of Follicle stimulating hormone (FSH) an luteinizing hormone (LH)

H.1.5: Explain the control of ADH secretion by negative feedback

H.1.5: ADH and the Negative feedback control ADH – Antidiuretic Hormone, controls how much water is reabsorbed from the collecting duct back into the bloodstream The hypothalamus is sensitive to plasma concentration changes The dendrites produce ADH in the hypothalamus: the hormone travels along the axon into membrane-bound granule at the end of the cell Into posterior pituitary

H.1.5: ADH and the Negative feedback control – Cont. Osmoregulatory sensitive cells in the hypothalamus: Detect changes in concentration of plasma Send action potentials to the storing region in the posterior pituitary If Water contents are low, ADH is secreted to reabsorb water back in the bloodstream If water contents are high, no action potentials are sent so no ADH is produced ADH is secreted and has its target tissue of the Distal Convoluted and Collecting tubules of the kidney. The ADH causes the opening of the Aquaporin (pores) which increases water reabsorption from kidney filtrate.