Chapter 2 - Chemical Messengers Flashcards
Describe what the nervous system and endocrine system are responsible for in one sentence.
The nervous system exerts control by the transmission of nerve impulses to and from various tissues.
The endocrine system influences the activity of cells by the release of chemical messengers known as hormones.
What are the two main types of glands in the body and how are they different?
Exocrine glands - secrete into a duct that carries the secretion to the body’s surface. Examples of the exocrine glands are ; sweat glands, salivary glands and glands of the alimentary canal.
Endocrine glands - secrete hormones into the extracellular fluid that surrounds the cells that make up the gland. The secretion usually then passes into blood capillaries and are sometimes called ductless glands. Examples of endocrine glands ; the pituitary gland, thyroid gland, adrenal gland, pancreas, ovaries and testes.
What are hormones, in one sentence.
Hormones may be proteins, steroids and/amines that are transported throughout the body via blood to activate particular enzymes.
What are local hormones?
Also known as paracrines, local hormones are chemical substances that have been secreted by cells that want to communicate with adjacent cells. Paracrines move through extracellular fluid. Actual hormones, however, are secreted by specialised cell’s and move through the blood.
What are protein and amine hormones?
Protein/amine hormones work by attaching to receptor proteins embedded in the cell membrane of the target cell. The combination of hormone with the receptor causes a secondary messenger substance to diffuse through the cell and activate particular enzymes.
What are steroid hormones?
Steroid hormones work by entering the target cells and combing with receptor proteins that are on the organelles or in the nucleus. This hormone - receptor complex activates the genes that control protein synthesis.
What is enzyme amplification?
When a singular hormone triggers multiple enzyme molecules.
What is negative feedback?
Regulates/prevents the stimulus of secretions of particular hormones. It stops a secretion from being released.
Negative feedback often involve releasing factors (which stimulate the release of a hormone) and inhibiting factors (which slow down the secretion of a hormone).
What is the hypothalamus?
The hypothalamus is a vital organ located at the base of the brain that regulates body temperature, water balance, heart rate etc. many of these functions are carried out through the pituitary gland.
What are the components that make up the pituitary gland?
The pituitary gland aka the hypophysis is made up of a stalk that connects the hypothalamus to the two lobes called the infundibulum. The two lobes are called the anterior lobe (adenohypophysis) and the posterior lobe (neurophypophysis).
What is the function of the anterior lobe of the pituitary?
- front lobe
- has no nerves connecting it to the hypothalamus
- has blood vessels connecting to the hypothalamus
- hormones from the hypothalamus regulate and control the secretions from the anterior lobe.
What is the function of the posterior lobe of the pituitary?
- rear lobe
- connected to the hypothalamus via nerve fibres that come from nerve cell bodies.
- not a true gland because it does not manufacture hormones, but rather secretes hormones made in the hypothalamus.
Describe the thyroid gland.
- secretes thyroxine
- targets most cells
- increases and regulates metabolic rate and therefore oxygen consumption and heat production.
- located underneath the larynx and has two lobes
Describe the Parathyroid gland.
- secretes parathyroid hormones
- target organs include kidneys and bones
- increases level of calcium in the blood
- located in the back of the thyroid glands
Describe the thymus.
- secretes thymosins
- it targets T Lymphocytes
- stimulates development and maturation of T Lymphocytes
- located above the heart and just behind the sternum.
