Lecture_23_Endocrine_System.pptx

Endocrine System Lecture 23: Chapter 37 Endocrine System Hormones – chemical signals secreted by cells or glands which influence the actions of other cells within the body Endocrine System Endocrine system regulates: Responses to the environment Growth and development Homeostasis Reproduction Enviro...

Endocrine System Lecture 23: Chapter 37 Endocrine System Hormones – chemical signals secreted by cells or glands which influence the actions of other cells within the body Endocrine System Endocrine system regulates: Responses to the environment Growth and development Homeostasis Reproduction Environmental Responses Often triggered by sensory input from the nervous system Predator presence => Release of adrenaline Mate presence => Release of sex hormones Growth Regulation Sex hormones are released to trigger the development of secondary sex characteristics as an animal approaches adulthood. Molting and metamorphosis in insects is triggered by the release of hormones in tissues in the head Growth Regulation Loof and Schoofs. 2020. Growth Regulation Growth Regulation The corpora allata are an example of neurosecretory cells. These cells are neurons that secrete hormones, rather than neurotransmitters. In humans, growth regulation is primarily controlled by the pituitary gland, which produces Human Growth Hormone (hGH or somatotropin). Homeostasis Regulation Hormones regulate a large number of bodily processes including: Circadian rhythms Metabolism “Fight, Flight, Freeze” responses Blood Sugar Blood Sugar Regulation Pancreas – endocrine organ that regulates blood sugar via negative feedback loops Regulation via Positive Feedback Loops Have a destabilizing impact Used to precipitate a particular event, like childbirth Hormones Hormones target specific cells Only affect cells that have a receptor for the hormone Allows hormones to be released into the blood and trigger cells in different parts of the body Hormones Hormones Receptors May be on the cell surface May be inside a cell Which depends on the molecular makeup of the hormone Hormones Hormones Molecules Hydrophilic Cannon cross cell membrane Ex: Peptides & Amines Hydrophobic Can cross cell membranes Ex: Steroids Hormones Amines & Peptide Hormones More abundant More diverse Work in minutes to hours Typically initiate signal cascades that activate or repress enzymes Changes cell shape, size, division, or triggers release of another hormone Hormone Amplification Hormones are typically released in small amounts, but are amplified along a hormonal pathway. Hormonal pathway – one gland releases a hormone that triggers a second gland to release a hormone, etc. Signals are amplified at each step of the pathway until the final impact on the target cell is quite large Hormone Amplification Hormone pathways usually begin with a Releasing Hormone from the hypothalamus Evolutionary Conservation of Hormones Vertebrates and invertebrates share a number of hormones, though their function differs between the groups Some hormones also function as neurotransmitters Vertebrate Endocrine System Responds to sensory input from the nervous system Hypothalamus responds to sensory input by secreting releasing hormones Releasing hormones signal anterior or posterior pituitary Pituitary then releases hormones to regulate the rest of the endocrine system Pituitary Gland Anterior pituitary forms from epithelial cells in the roof of the mouth Posterior pituitary forms from neural tissue at the base of the brain Both sets of cells form pouches adjacent to each other Pituitary Gland The hypothalamus contains neurosecretory cells that release hormones into the blood vessels that supply the anterior pituitary The hypothalamus neurosecretory cells synapse directly with the posterior pituitary gland Pituitary Gland Hormones released by the anterior pituitary act on other glands to cause the release of other hormones Hormones that control the release of other hormones are called Tropic Hormones Pituitary Gland Hormones released by the anterior pituitary include: TSH – target thyroid Controls metabolism FSH – signals gonads for sexual development LH – signals gonads to produce sex hormones ACTH – signals adrenal glands to produce cortisol in times of stress Raises blood sugar and suppresses immune function Pituitary Gland Hormones released by the posterior pituitary gland include oxytocin and antidiuretic hormone (ADH) These are both peptide hormones Other Body Glands Parathyroid gland – controls the level of calcium in the blood by signaling bone to be built or broken down Pineal gland – controls circadian rhythms by secreting melatonin Other Body Glands Adrenal medulla – secretes epinephrine and norepinephrine, which regulate fight, flight, freeze responses Local Chemical Communication Called “paracrines” Chemical that acts on the cell that secreted it is called “autocrine” Histamines are paracrines that are released when a cell is damaged They dilate blood vessels and cause inflammation Akash Institute. 2024. Other Forms of Chemical Communication Local chemical signals regulate neighboring cells Pheromones released into the environment influence conspecifics Pheromones Chemical signals released by animals to communicate with other members of the species Signal mating, mark territory, communicate food location, alert others to danger, provide a trail to follow, etc.