snaptaya.blogg.se - Coursenotes ap bio ch 45

Most protein/peptides and amine hormones are water-soluble, unlike steroid hormones.Three major classes of molecules function as hormones in vertebrates: proteins and peptides, amines, and steroids.Pheromones carry messages to different individuals of a species.Other chemical signals-local regulators-transmit information to target cells near the secreting cells.Hormones convey information via the bloodstream to target cells throughout the body.The release of milk in turn leads to more suckling and stimulation of the pathway, until the baby is satisfied.Ĭoncept 45.2 Hormones and other chemical signals bind to target cell receptors, initiating pathways that culminate in specific cell responses.Oxytocin causes the mammary glands to secrete milk.The hypothalamus triggers the release of the neurohormone oxytocin from the posterior pituitary gland.

Suckling stimulates sensory nerve cells in the nipples, which send nervous signals that reach the hypothalamus, the control center.

The neurohormone pathway that regulates the release of milk by a nursing mother is an example of positive feedback.

Positive feedback reinforces the stimulus and leads to an even greater response.

Negative feedback regulates many endocrine and nervous mechanisms.

This prevents overreaction by the system.

In negative feedback, the effector response reduces the initial stimulus, and eventually the response ceases.

A common feature of control pathways is a feedback loop connecting the response to the initial stimulus.

The three types of simple hormonal pathways (simple endocrine pathway, simple neurohormone pathway, and simple neuroendocrine pathway) include these basic functional components.

In endocrine and neuroendocrine pathways, this outgoing signal, called an efferent system, is a hormone or neurohormone, which acts on particular effector tissues and elicits specific physiological or developmental changes.

After comparing the incoming information to a set point, the control center sends out a signal that directs an effector to respond.

A receptor, or sensor, detects a stimulus and sends information to a control center.

The fundamental concepts of biological control systems are important in regulation by hormones.

The nervous system plays a role in certain sustained responses-controlling day/night cycles and reproductive cycles in many animals, for example-often by increasing or decreasing secretions from endocrine glands.

Chemicals such as epinephrine serve as both hormones of the endocrine system and neurotransmitters in the nervous system.

The hormones produced by these cells are sometimes called neurohormones.Certain specialized nerve cells known as neurosecretory cells release hormones into the blood.The nervous and endocrine systems overlap to some extent.Hormone-secreting organs called endocrine glands secrete hormones directly into the extracellular fluid, where they diffuse into the blood.Hormones also regulate long-term developmental processes such as growth and development of primary and secondary sexual characteristics.Hormones coordinate slow but long-acting responses to stimuli such as stress, dehydration, and low blood glucose levels.Collectively, all of an animal’s hormone-secreting cells constitute its endocrine system.Animals have two systems of internal communication and regulation, the nervous system and the endocrine system.

A given hormone traveling in the bloodstream elicits specific responses from its target cells, while other cell types ignore that particular hormone.Ĭoncept 45.1 The endocrine system and the nervous system act individually and together in regulating an animal’s physiology.A hormone may reach all parts of the body, but only specific target cells respond to specific hormones.An animal hormone is a chemical signal that is secreted into the circulatory system that communicates regulatory messages within the body.Overview: The Body’s Long-Distance Regulators

Chapter 45 Hormones and the Endocrine System