An Introduction to Regulatory Systems

Compare the response times of the two major systems of internal communication: the nervous system and the endocrine system.

The nervous system conveys high-speed signals along specialized cells called neurons for a quick response to stimuli.

The endocrine system uses hormones for a much slower transfer of information to parts of the body. Hormone transfer is through body fluids.

What are neurosecretory cells and what is their action.

Neurocecretory cells secrete hormones that can function in both the endocrine system and the nervous system. Epinephrine functions as both a hormone produced by the adrenal gland for ‘fight or flight’ and as a neurotransmitter to convey messages between neurons.

Chemical Signals and Their Modes of Action

How do pheromones work.

Pheromones carry messages between different individuals of a species, as in mate attraction.

Describe the diverse functions of growth factors, nitric oxide, and prostaglandins.

Growth factors are proteins that stimulate cell proliferation and are present in the extracellular environment. Their names, e.g., nerve growth factor, epidermal growth factor, are more restrictive then their many actions on different cell types.

Nitric oxide (NO) is a local regulator, acting on neighboring cells. It is highly reactive and potentially toxic. NO functions as a neurotransmitter, in white blood cells it kills bacteria and cancer cells, and when released from endothelial cells it causes smooth muscle around blood vessels to dilate.

Prostaglandins are local regulators and are modified fatty acids. They help induce fever and inflammation, and function in vasoconstriction and vasodilation.

Define a signal-transduction pathway.

A series of molecular changes that converts an extracellular chemical signal to a specific intracellular response.

Describe several examples of different physiological reactions in animals exposed to the same hormone.

Estrogen induces cells in the reproductive system of a female bird to synthesize large amounts of ovalbumin and in human females estrogen functions in development and maintenance of female characteristics and uterine lining growth.

Thyroxine – in humans regulates metabolic rate and in frogs it triggers metamorphosis of the tadpole into an adult.

The Vertebrate Endocrine System

Explain how the hypothalamus and pituitary glands interact and how they coordinate the endocrine system.

The hypothalamus receives information from nerves and the pituitary obeys hormonal orders from the hypothalamus.

List and explain the functions of the hormones released from the anterior and posterior lobes.

Posterior pituitary: Oxytocin – acts on muscles of uterus during childbirth and stimulates the mammary glands to produce milk during nursing, and ADH – acts on the kidney functions to increase the water retention of the kidney, thus decreasing urine volume.

Anterior pituitary: thyroid-stimulating hormone (TSH) – regulates the release of thyroid hormones, adrenocorticotropic hormone (ACTH) controls the adrenal cortex, follicle-stimulating hormone (FSH) and leuteinizing hormone (LH) control reproduction by actions on the gonads. Also growth hormone (GH), which stimulates the release of other growth factors, prolactin, endorphins (also produced in the brain) and melanocyte-stimulating hormone are produced in the anterior pituitary.