Endocrinology Introduction PDF

ENDOCRINOLOGY - Secrete directly onto other cells, The study of hormones, the endocrine tissues, ECF, or the circulating system, and their role in the body’s blood (which acts as a carrier physiology....

ENDOCRINOLOGY - Secrete directly onto other cells, The study of hormones, the endocrine tissues, ECF, or the circulating system, and their role in the body’s blood (which acts as a carrier physiology. onto the target sites). The physiological branch deals with the study of endocrine glands, hormones EXOCRINE they produce, and their function. - Denotes secretion outside the body (e.g., through sweat HORMONES glands or ducts that lead into the Chemical compounds or substances gastrointestinal tract). produced in a minute (small) amounts - Ex: Milk from the mammary from the endocrine system or glands, gland is secreted outside via the affecting the body’s function. ducts. A substance produced by an endocrine - Ex: Saliva is secreted outside organ in minute (small) amounts but the cells. can still affect body functions. The endocrine system releases It circulates in the lymph vessels. hormones into the circulation to convey information to target cells that contain ENZYMES cognate hormone receptors. A substance produced by certain This system is subject to complex organs/exocrine glands catalyzes regulatory mechanisms that govern several compounds into other particles hormone synthesis, release, transport, or products. metabolism, and delivery to the interior of the target cells, and the expression ENDOCRINE SYSTEM and activity of the hormone receptor Controls the flow of information itself and its downstream signaling between different cells and tissues. machinery (in short, it acts like - Ex: signal of cell phones. gasoline). Although they are far from each other, they can contact each ENDOCRINE SYSTEMS ARE FOR: other. Functions of the endocrine ENDOCRINE 1. Maintain internal homeostasis - Denotes the internal secretion of - To balance the processes inside biologically active substances. the body. - Ex: Small amount of estrogen in - Ex: bitches get estrus cycle the bitch already has a big (most prominent in pigs since impact on its behavior. estrus cycle is 21-28 days) due ➔ If the estrogen increases to the rise and fall of the body’s even in the smallest hormones. amount, it will undergo - Ex: the body’s heat regulation is proestrus. normal if the thyroid hormones’ ➔ If the estrogen production is also normal. decreases and the - Ex: pituitary gland’s hormones progesterone increases, produce balance since it is the it will undergo diestrus. one who signals or gives - Ductless glands whose feedback. secretion can influence various 2. Support cell growth vital functions of the animal - Reasons for normal growth, behavior (before birth to death). dwarfism, and gigantism. - Control homeostasis 3. Coordinate development (homeokinesis). 4. Coordinate reproduction - Body activities controlled by the 5. Facilitate responses to external stimuli endocrine: - Ex: due to heat, the body ➔ Aging maintains the normal ➔ Conception temperature to avoid heat ➔ Digestion explosion. ➔ Gestation ➔ Growth ➔ Metabolism ➔ Parturition ➔ Puberty 1 In the endocrine system, all the regulated, it is detected by the physiological activities of the body are pituitary gland which secretes regulated by 2 major systems: hormones to control the thyroid 1.) Nervous System gland]. - Make the body move via - Ex: Cellphones (endocrine) stimulation. Once there is a have no direct connection, but stimulus, the body reacts, they communicate with one whether it is the autonomic or another. In contrast, the central nervous system. telephone (nervous) has a line - Radiate signal through connected to communicate. neurotransmitters between Integrate stimuli and responses to nerve endings. changes in an external and internal environment. - The nervous system responds faster to the stimuli, whereas the endocrine system takes time to process. 2.) Endocrine System - Ex: if the weather is hot, the - The happenings inside the body endocrine system takes time to with the individual being aware. release hormones. Whereas in - It functions by secreting some the nervous system, once it has chemical substances called the stimulus site, it will hormones. immediately respond or signal - Ex: when urinating, hormones (reaction is at once). are produced to make the cycle Both are crucial to coordinated normal and easy to urinate. functions of highly differential cells, tissues, and organs. - Ex: a guy got scared, which makes his heart beat fast, and it has not yet gone back to its normal heartbeat after minutes, to find out that he has excess hormone production (such as thyroid hormone). Now, the brain will command the heart via cranial nerves to stop beating These 2 systems interact with one fast. But if the production of the another and regulate body functions thyroid hormone does not (not autonomous from one another). decrease, the work of the cranial - Ex: The ova matured, so it will nerve is not enough. In short, detach from the ovary, which will the nervous and the endocrine change hormones. When the needs to work out together, brain detects changes in which requires a stronger signal. hormones, the brain will - Ex: Gigantism. The pituitary command the pituitary gland gland produces many growth and other concerned glands not hormones, but the brain does to produce too many hormones. not control it (since the brain Both systems interact in controlling thinks it is normal since the body functions. pituitary gland is doing its job), making the individual grow ENDOCRINE vs. NERVOUS SYSTEM gigantically. Major communication systems in the - Ex: In a company, many body. systems require a cellphone and The body regulation systems. a telephone to do the job right. - The nervous system needs - Unlike the nervous system, the stimuli whereas the needs endocrine system is command from the brain and the anatomically discontinuous. feedback mechanisms [which Cell to cell signaling refers to also starts the production of the transferring information from one cell to endocrine; e.g., when the another (seen in both systems). thyroid hormone is high (let’s say P3 or P4), it needs to be 2  - Also called cell signaling or 2) Local hormones intercellular communication. - They are secreted from other The cells of the body communicate with tissues. each other through some chemical However, recently chemical messenger has substance called chemical been classified into 4 types: messengers. 1) Endocrine messengers - Directly secreted by endocrine CHEMICAL MESSENGERS glands. These are the substances involved in - Endocrine messengers are the cell signaling. classical hormones. - These messengers are mainly - A hormone is a chemical secreted from endocrine glands. messenger synthesized by - Some chemical messengers are endocrine glands and secreted by nerve endings and transported by the blood to the the cells of several other tissues target organs or tissues (site of (such as acetylcholine). action). - Ex: Delivery man (chemical - Ex: growth hormones and messenger) picks up the insulin. package (hormone) then brings - Cell in endocrine gland → it to you. Once received, you Transport of through blood → can now use the product inside Target blood. the package. Transducers are proteins that convert the information in hormonal signals into chemical signals understood by cellular machinery. They change their shape & activity when they interact directly with protein-hormone complexes. 2) Paracrine messengers Usually, enzymes or nucleotide-binding - These are the chemical proteins produce 2nd messengers or messengers which diffuse from change the activity of other proteins by the control cells to the target covalently modifying them (adding or cells through the interstitial fluid. removing phosphate, lipid groups, - Some of these substances acetate, or methyl groups), or they directly enter the neighboring interact with other proteins that do target cells through gap these things. junctions. They begin amplifying the energy - Such substances are also called content of the original hormone signals. juxtacrine messengers or Effectors are the enzymes and other local hormones. proteins that convert the transduced - Ex: prostaglandins and hormonal signal into biochemical histamine. changes that generate the cellular - Signaling cell → Messenger 😂 response to hormone binding. diffuses through an interstitial Usually, amplify the signal further and fluid (sa kalsada pinadaan ) allow cellular work to be done. → Target cell. - Cell motion, growth, division, - Signaling cell → Messenger altered metabolism, etc. diffuses through gap junction It carries the message (signal) from the (neighbor) → Target cell. signaling cells (controlling cells) to target cells. The messenger substance may be the hormones or hormones like substance. 4 CLASSIFICATION OF CHEMICAL MESSENGERS Generally, the chemical messengers are classified into 2 types: 1) Classical hormones - Endocrine glands secrete them. 3  3) Autocrine messengers ENDOCRINE GLANDS - Produces hormone, which will These are the glands that synthesize also use it by itself. and release the classical hormones into - Self-affect; signaling itself. the blood. - Signaling cell → Messenger Also called ductless glands because acts on the same cell. the hormones secreted by them are - Ex: there’s water; it splashes the released directly into the blood without water to itself (target cell and any duct. signaling cell are only one). These are distinct from the exocrine - Ex: A dog encounters stomach glands, which release their secretions hyperacidity due to starvation, through ducts. although there’s still food to digest in its stomach. To reduce ★ The difference between the endocrine acidity, he will vomit the gland and the exocrine gland is the site undigested food and eat it again of release. to let it think that he ate and he is full. 1.) The endocrine system is an integrator of body functions; and, together with the CNS, maintains homeostasis. - The nervous system brings about rapid localized responses (it’s like a 1-second delay). ➔ Directly via neural connections. 4) Neurocrine messengers - The endocrine system causes - Affect nerve impulses slower, often more widespread - Seen in between neuromuscular responses (it’s like 5 seconds junctions. delay). - Specific in nerve functions or ➔ Indirectly via hormone endings. receptors (dadaan pa sa - Neurocrine is neurotransmitters carriers niya). and neurohormones. 2.) Characteristics - Cluster of Cells - Ductless Glands (endocrine glands; pituitary, hypothalamus, thyroid and parathyroid gland, renal gland). - Scattered Single Cells 3.) Endocrine organs develop from all three NEUROTRANSMITTER germ layers (endoderm, ectoderm, and An endogenous signaling molecule mesoderm). carries information from one nerve cell to another nerve cell, muscle, or tissue. Ex: acetylcholine and dopamine. NEUROHORMONE A chemical substance is released by the nerve cell directly into the blood and transported to the distant target cells. - Ex: oxytocin, antidiuretic hormone, and hypothalamic releasing hormones. Some of the chemical mediators act as more than one type of chemical messenger. - Ex: noradrenaline and dopamine function as classical hormones as well as neurotransmitters. - Similarly, histamine acts as a neurotransmitter and paracrine messenger. 4  in hormonal signals into chemical signals understood by cellular machinery. - They can change shape and activity as they interact directly with protein-hormone complexes. - After interacting with enzymes or nucleotide-binding proteins, they produce 2nd messages or change the activity of other proteins by covalently modifying them (adding or removing 9 MAJOR ENDOCRINE GLANDS phosphate, lipid groups, acetate, 1) Hypothalamus or methyl groups), or they 2) Pituitary gland interact with other proteins that 3) Pineal gland do these things. 4) Thyroid gland ➔ It’s like 5) Parathyroid gland pass-the-message. 6) Thymus ➔ Ex: 1st messenger 7) Adrenal gland brings the paper to 2nd 8) Pancreas messenger. Once the 9) Reproductive glands (Ovary and 2nd person receives it, Testes) he becomes the 2nd messenger. - They begin amplifying the energy content of the original hormone signals. b. Effectors - These enzymes and other proteins convert the transduced hormonal signal into chemical changes that generate the cellular response to hormone binding. ➔ It will change or copy the 2 GROUPS OF THE ENDOCRINE 1st messenger to 1) Steroid Hormone Producers convert itself into the 2nd - Ovaries, Testes, Adrenal cortex, messenger. some fetal membranes. - It usually amplifies the signal 2) Protein Hormone Producers further and allows cellular work - The adrenal medulla, Thyroid, to be done as: Parathyroid, Hypophysis, ➔ Cell growth, division, Pancreas, Fetal membrane altered metabolism, (endometrium). secretion, depolarization, etc. MECHANISM OF ACTION (ENDOCRINE) 1) Direct Intracellular Stimulation 3) Information Transfer 2) Second-Messenger Concept This is how the information is a. Transducers transferred by the endocrine - These are proteins that gland. convert the information 5  a. Hormone - Receptor ⇆ parathyroid hormone to deposit Hormone-Receptor Complex → calcium into the bone and Activation of Cell Process increase the bone or muscle’s b. Where is the message? H? R? Or HR? size. c. Classes: 2. Antagonistic Action 1. Ligand has the message. - When a hormone decreases or - Receptors act only to stops the action of another concentrate, process, hormone. and/or translocate the - Ex: When there is excess ligand to the intracellular progesterone, a feedback site. Experimentally, an mechanism will happen. The element of ligand (in the feedback mechanism will absence of a receptor) produce hormones again to stop can activate the relevant estrogen production, especially biological event. when the mammal is already A. Toxins: cholera, pregnant. diphtheria (enzyme) B. Low-density lipoproteins (cholesterol) C. Virus (nucleic acid) 2. The receptor has the message. - The receptor has the full program for the cell activation, and experimentally, the receptor can produce a full effect without a specific natural ligand. Ligand’s function is to get the receptor to express its program. A. Polypeptide hormones: insulin, TSH B. Acetylcholine (nicotinic) receptors C. IgE receptors 3. Receptor and ligand. - Both receptor and ligand together contribute information to cell activation. A. Egg and sperm 2 TERMS TO TAKE NOTE OF (ENDOCRINE) 1. Potential or Synergistic Action - When a hormone increases the activity of other hormones. - Ex: Hormone A went out. Hormone A’s effect strengthens hormone B’s effect (sized up; x3 the potency). - Ex: Hypothalamus produces growth hormone. The growth hormone will expand the thyroid gland’s capacity to produce a 6 - Hypothalamus gives the message. Ex: When you are depressed and not eating, the hypothalamus provides you with a sign to eat. - It affects all emotions. 7 8