Ch 45: Hormones and Endocrine System

2.e.2 – Timing and coordination of physiological events are regulated by multiple mechanisms (11.1).

3.b.2 – A variety of intercellular and intracellular signal transmissions mediate gene expression (11.1 & 11.4).

3.d.1 – Cell communication processes share common features that reflect a shared evolutionary history (11.2 & 11.2).

3.d.2 – Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling (11.1 & 11.2).

Essential Knowledge

3.d.3 – Signal transduction pathways link signal reception with cellular response (11.3).

3.d.4 – Changes in signal transduction pathways can alter cellular response (11.4).

Essential Knowledge

Endocrine system deals with chemical control and communication

Uses hormones◦Hormone: chemical signal usually transported

through bloodstream, elicits a specific response from target cell

◦Produced by endocrine cells (neurosecretory cells) Specialized nerve cells

◦ Hormones regulate activity of other cells and organs

◦ Hormones bind to cell surface receptors

Introduction

Hypothalamus and pituitary gland coordinate◦Produce many hormones

that control production of other hormones in other endocrine glands/organs

◦Nervous system: coordinates and communicates

◦Endocrine system: produces hormones which regulate bodily processes

Introduction

A receptor/sensor detects a change (stimulus)◦ Receptor notifies the control center◦ Control center sends out an efferent signal which

directs a response by effector Endocrine cells: acts as both sensor and

control center◦ Sends out either hormones or signal

Usually controlled via negative feedback loop

Pathways for signals

Three groups/classes of hormones:1.Peptide/Protein (water-soluble)2.Amine (water-soluble)3.Steroid

Types of signals:1. Hormones: within body (long distance)2. Local regulators: neighboring cells3. Phermones: communication between

individual organisms

Hormones

Hormones bind to target cell receptors◦Initiate pathways/signals that end in

specific cell responses Steps of signal response:

1.Reception: Signal binds to specific protein receptor on target cell

2.Signal transduction: signal’s message is transmitted via target cell

3.Response: the end result, how the target cell responds

Hormones

Hypothalamus and pituitary integrate the endocrine system functions◦Hypothalamus: Situated in lower brain Integrates endocrine and nervous system Receives nerve signals from body It’s neurosecretory cells release hormones These hormones are stored in or regulate

by the pituitary gland

Hypothalamus

Pituitary gland:◦Located at the base of hypothalamus◦Regulate and stores hormones produced by

hypothalamus◦Two parts:

1.Posterior: stores and secretes two hormones from hypothalamus

2.Anterior: makes at least 6 hormones (tropic hormones), important to chemical coordination

Pituitary gland

Antidiuretic hormone (ADH)◦ Functions in osmoregulation◦ Increases water retention by kidney (decreases

urine volume)◦ Produced in posterior pituitary

Oxytocin◦ Induces uterine contractions during birth ◦ Induces milk ejection during nursing◦ Produced in posterior pituitary

Thyroid-stimulating hormone (TSH)◦ Regulates production of thyroid hormones◦ Produce in anterior pituitary gland

Hormone examples

Follicle-stimulating hormone (FSH) and luteinizing hormone (LH):◦ Stimulate gonad activity◦ Produced in anterior pituitary

Prolactin (PRL)◦ Mammals: milk production and secretion◦ Amphibians: delays metamorphosis◦ Fish: osmoregulation◦ Produced in anterior pituitary

Endorphin:◦ Pain perception ◦ Can resemble opiate drugs (giving you a sense of

well-being!) ◦ Produced in anterior pituitary

Hormone examples

Growth hormone (GH):◦ Variety of target tissues◦ Signals release of IGFs (Insulin-like growth factors)◦ Gigantism (human growth disorder caused by

excessive GH)◦ Produced by anterior pituitary

IGFs:◦ Produced by liver◦ Stimulate bone and cartilage growth

T3 and T4:◦ Produced by thyroid gland◦ Secretion controlled by negative feedback◦ Critical to development and maturation

Hormone examples

T3 and T4, cont.:◦ Contributes to homeostasis

Maintain normal blood pressure, heart rate, muscle tone, digestion, reproductive function

Blood calcium hormones:◦Parathyroid hormone (PTH): stimulate

Calcium resabsorption in kidney, activate vitamin D which helps uptake of Ca in intestines

◦Calcitonin: hormone that lowers calcium levels in blood

Hormone examples

Blood glucose hormones:◦Glucagon: raises glucose concentrations

by stimulating liver to increase breakdown of glycogen

◦Insulin: lowers glucose concentration by promoting movement of glucose from blood into other body cells

◦Produced by pancreatic cells◦Diabetes mellitus: absence of insulin in

bloodstream or loss of response to insulin Type-I: autoimmune disorder, treated by regular insulin

injections Type-II: 90% of diabetics, insulin deficiency, controlled

via exercise and diet control

Hormone examples

Stress hormones:◦Epinephrine (adrenaline)◦Norepinephrine (noradrenaline)

Sustain blood pressure◦Produced by adrenal glands◦Increase availability of energy sources◦Increase metabolic rate

Gonadal sex hormones:◦Produces by testes and ovaries ◦Affect growth, development and

reproductive cycles and behaviors

Hormone examples

Epinephrine works on the sympathetic ½ of nervous system

Gonadal sex hormones, cont.:◦Three groups:

1.Androgens: Produced primarily by testes Ex: testosterone (determines gender,

stimulate development of male reproductive system)

2.Estrogens Produced by ovaries Regulate development and maintenance of

female reproductive system3.Progestins

Help prepare and maintain uterus for growth of embryo

Hormone examples

Melatonin:◦Secreted and produced in pineal gland

(near center of brain)◦Regulate functions related to light and

changes in day length◦Secretion at night functions with

biological clock for daily or seasonal activities (such as sleeping, mating, nesting)

Hormone examples

Exclusion Statements Memorization of the names, molecular

structures, and specific effects of hormones or features of the brain are responsible for these physiological phenomena is beyond the scope of the course and the AP Exam.