The Endocrine System and the Nervous System Control freaks of the body

Endocrine System The endocrine system is composed of glands that produces chemical messengers called hormones. Hormones are produced in one part of the body and travel to target organs through the bloodstream.

Endocrine system Glands of the endocrine system include: Pituitary gland Thyroid Gland Parathyroid glands Thymus Adrenal glands Pancreas Ovary and Testis

Hormones Responsible for regulating: Reproduction Growth & Development Energy production & use Maintenance of internal environment

Endocrine System The brain continuously sends signals to the endocrine glands to secrete and release hormones and the glands, in turn, send feedback to the nervous system. The hormone travels to its target organ and usually results in the release of another hormone into the bloodstream.

The Nervous Systems: a) Interprets incoming information, b) generates response when needed Sensory = afferent nerves, carry info to central processor as action potentials Central Processor (brain or ganglion) Motor = efferent nerves, carry info toward effectors Effectors (muscles or glands) Sensory Receptors Special nervous tissue to collect information that is important to the animal Organs that can cause a change in the body

Neuron Structure of a neuron. A, Diagram of a typical neuron showing dendrites, a cell body, and an axon. B, Segment of a myelinated axon cut to show detail of the concentric layers of the Schwann cell filled with myelin. C, Photomicrograph of neuron. (C, Dennis Strete.)

The Synapse the place where impulses are transmitted from one neuron to another (the postsynaptic neuron) Components of a synapse. Diagram shows synaptic knob or axon terminal of presynaptic neuron, the plasma membrane of a postsynaptic neuron, and a synaptic cleft. On the arrival of an action potential at a synaptic knob, neurotransmitter molecules are released from vesicles in the knob into the synaptic cleft. The combining of neurotransmitter and receptor molecules in the plasma membrane of the postsynaptic neuron opens ion channels and thereby initiates impulse conduction in the postsynaptic neuron.

Endocrine v. Nervous The hormones of the endocrine system produce specific effects on body functions very slowly. This is due to the slow release of the chemicals (hormones). By contrast, the nervous system brings about very fast changes. This is because the nervous system does not use chemical messengers, it uses electricity. The endocrine system and the nervous system work together to control the metabolic activity of the body.

How do the Nervous and Endocrine Systems Differ? Nervous System Rapid acting Involved in control of things that change over short time periods (seconds to minutes) Examples – Heart rate Respiration Voluntary muscle contractions Endocrine System More slowly acting Involved in control of things that change over long time periods (minutes to years) Examples – Growth reproduction Facebook post (endocrine system) vs. direct text message (nervous system)

TROPISM Plant growth in response to a stimulus (“tropo” – ”turn”) . There are many types of tropisms : Phototropism Geotropism Thigmotropism Hydrotropism Chemotropism Thermotropism 3 main types * Can be positive or negative

Geotropism is the growth of a plant in response to gravity. (“Geo” – Earth) Geotropism is the growth of a plant in response to gravity. Negative Geotropism Positive Geotropism It is the growth of a plant towards the center of the earth-down with gravity. Ex. roots growing down Negative Geotropism It is the growth of a plant away from the center of the earth-opposite from the pull of gravity Ex. stems grow up Positive Geotropism NEXT

Ex. Stems growing toward the window to get to the light PHOTOTROPISM (“Photo” – light) The growth response of a plant in response to light direction is called phototropism. Ex. Stems growing toward the window to get to the light NEXT

Thigmotropism is the growth of a plant in response to touch/contact. (“Thigmo” – “touch”) Thigmotropism is the growth of a plant in response to touch/contact. Photo by Christopher Meloche Tendrils on a sweet pea Vines growing on a wall or fence NEXT

Chemotropism THERMOTROPISM HYDROTROPISM (“Therm” – “heat”) Thermotropism is the tendency of plants or other organisms to bend toward or away from heat. Ex. curling of Rhododendron leaves in response to cold temperatures. HYDROTROPISM (“hydro” – “water”) Hydrotropism is the growth in response to water. Ex. roots growing toward moisture Chemotropism (“Chemo” – chemical”) Chemotropism is movement caused by chemical stimuli. Ex. Growth of a pollen tube is always towards the ovules so that reproduction can occur NEXT