REGULATION Biology-Unit 9

Definition The life function by which an organism controls and coordinates its other life functions to maintain existence. Includes both Nervous Control (animals only) and Chemical Control (all organisms). -Responses are very rapid in rate and short lasting in the nervous system, slower and longer lasting in the endocrine system.

Parts of the nervous system 1. Neurons – basic functional units of the human nervous system. -Neurons are cells specialized for the transmission of nerve impulses from place to place in the body.

Typical Neuron Nucleus Axon terminals Cell body Myelin sheath Nodes Dendrites

Neurons are made of the following: Dendrites – fibers that serve to detect a stimulus and direct an impulse toward the cell body. Cell body – the main cell body, containing most of the cytoplasm, nucleus, and other organelles. -It is here that the nerve impulse is generated.

Neurons are made of the following: Axon – an elongated portion of the neuron that carries the nerve impulses from the cell body toward the terminal branches. Terminal Branches – fibers leading from the axon of the nerve cell that reach toward the dendrites of adjacent neurons and secrete chemical neurotransmitters.

Neurons are made of the following: Synapse- the gap that occurs between adjacent neurons. -Nerve impulses are prevented from being transmitted between nerves across this gap unless a special chemical (neurotransmitter) is secreted. Neurotransmitter – special chemicals produced and secreted by the neuron’s terminal branches. -Carries the nerve impulse across the synapse.

Neurons are made of the following:

Three types of Neurons: a. Sensory neurons– receives stimuli from environment and transmits to central nervous system (CNS) for interpretation.

Three types of Neurons: b. Interneurons – located in central nervous system. Interprets sensory impulses and transmits “commands” to motor neurons.

Three types of Neurons: c. Motor Neurons– carries impulse from “command centers” in central nervous system (CNS) to effector organs (muscles or glands) where a response is initiated.

Organization of Neurons Nerves – bundles of neurons -May contain single type of neuron (sensory or motor nerves) or two separate types (mixed nerves). Central Nervous System (CNS) – consists of the brain and spinal cord.

The Central Nervous System The Brain – large organ composed of a mass of interneurons located in cranial cavity. -The Brain is highly specialized and subdivided into three major regions: The Cerebrum, Cerebellum, and Medulla

Parts of the Brain Cerebrum Thalamus Pineal gland Hypothalamus Pituitary gland Cerebellum Pons Medulla Spinal cord

Parts of the Brain 1. Cerebrum – largest portion of the brain -Regulates: conscious thought, memory, sense interpretation, reasoning, and other voluntary activities.

Parts of the Brain 2. Cerebellum – located at the rear of cranium. -Responsible for coordinating muscular activities and balance (cerebalance).

Parts of the Brain Medulla – Located at the base of brain. -Regulates the automatic, rhythmic processes of the body Ex. Heart beat, Peristalsis, rate of breathing, etc.

The Spinal Cord Continuous with the brain, Encased within the bony vertebral column (for protection). -coordinates the Reflex Arc.

Reflex Arc-Definition A rapid response made possible by a series of three neurons working together.

Reflex Arc-Components Receptor – A specialized structure sensitive to specific stimuli, they are found in sense organs. -A Stimulus is anything that can cause a change in activity by triggering a nervous impulse.

Reflex Arc-Components Sensory Neuron – receives a stimulus in a receptor. Interneuron (in the Spinal Cord) – interprets the sensory neurons impulse.

Reflex Arc-Components Motor Neuron – Carries impulses from the spinal cord to an effector. Effector – A muscle or a gland that works in response to a stimulus. Reflexes are so rapid and automatic that many are complete before our cerebrum makes us aware of the stimuli initiating them.

Malfunctions of the Nervous System Cerebral Palsy – group of congenital (inborn) disorders of the muscle and speech centers of the brain. Meningitis – inflammation of the meninges (membranes covering brain and spinal cord). Alzheimer’s disease- a chronic condition involving breakdown of the neurons in the brain (currently there is no cure)

Malfunctions of the Nervous System Stroke – brain function is impaired or destroyed by lack of oxygen. A blood clot restricts blood flow to the brain

The Endocrine System (Chemical Control of Organisms) In animals, hormones are produced and secreted by specialized Endocrine Glands. These hormones travel throughout the body but affect only specific target cells and organs Nervous system responses are fast and short lived, endocrine responses are slow and long lasting

The thyroid produces thyroxine, which regulates metabolism. Hypothalamus The hypothalamus makes hormones that control the pituitary gland. In addition, it makes hormones that are stored in the pituitary gland. Pineal gland The pineal gland releases melatonin, which is involved in rhythmic activities, such as daily sleep-wake cycles. Thyroid The thyroid produces thyroxine, which regulates metabolism. Pancreas The pancreas produces insulin and glucagon, which regulate the level of glucose in the blood. Ovary The ovaries produce estrogen and progesterone. Estrogen is required for the development of secondary sex characteristics and for the development of eggs. Progesterone prepares the uterus for a fertilized egg. Testis The testes produce testosterone, which is responsible for sperm production and the development of male secondary sex characteristics Pituitary gland The pituitary gland produces hormones that regulate many of the other endocrine glands. Parathyroid glands These four glands release parathyroid hormone, which regulate the level of calcium in the blood. Thymus During childhood, the thymus releases thymosin, which stimulates Tcell development. Adrenal glands The adrenal glands release epinephrine and nonepinephrine, which help the body deal with stress.

Glands Pituitary Gland – Located under the brain. Known as the master gland since such a large number of hormones are produced there.

Glands Ex. -Growth Hormone – targets all cells and affects growth of long bones. -Follicle Stimulating Hormone – targets gonads and affects females monthly cycle, production of female sex hormones and male gametes.

Glands Thyroid Gland – Located in the neck, surrounding the trachea. -Produces and releases thyroxin, a hormone which regulates metabolic rate. -Depends on a dietary supply of Iodine.

Glands Adrenal Glands – Located on top of the kidneys -Secretes adrenalin which affects the body’s response to danger. -Adrenalin increases the breathing rate, heart rate, and metabolism.

Glands Pancreas (Inlets of Langerhans) – gland tissue scattered throughout the pancreas. Produces both insulin and glucagon

Glands Insulin and glucagon have opposite effects on the body’s storage of sugar. Both hormones target cells of the liver. Insulin promotes sugar storage in the liver Sugar travels from Blood  Liver (Lowers blood sugar) Glucagon promotes the release of stored sugar from the liver. Sugars travel from Liver  Blood (Increases blood sugar)

Glands Gonads (Sex Glands) Male gonads are the testes which produce Testosterone. -Testosterone targets male sex organs and affects gamete (sperm) production, and male secondary sex characteristics. Female gonads are the ovaries which produce estrogen and progesterone. -These hormones control female secondary sexual characteristics and female sexual functions (menstrual cycle and pregnancy).

Negative Feedback Control The body’s mechanism that controls the endocrine system. This control returns hormone levels to normal levels and prevents the secretion of hormones that are not needed.

Negative Feedback Control Beta cells release insulin into the blood Body cells absorb glucose Blood glucose level increases Blood glucose level decreases Liver converts glycogen to glucose Homeostasis: Normal blood glucose level Blood glucose level decreases Blood glucose level increases Liver converts glycogen to glucose Alpha cells release glucagon into blood

Malfunctions of the Endocrine System Goiter – An enlargement of the thyroid gland. A goiter is caused when the thyroid is unable to produce thyroxin due to the body’s lack of Iodine.

Malfunctions of the Endocrine System Diabetes – The body’s inability to remove sugar from the blood and store it as glycogen in the liver. There are two causes.

Malfunctions of the Endocrine System The first cause is the body does not produce enough insulin. The cells do not receive the message to take glucose out of the blood. This is called Type I or Juvenile Onset Diabetes.

Malfunctions of the Endocrine System The second cause is when receptors on the surface of the cells no longer recognize insulin as a hormone messenger. They ignore the signal to remove glucose from the blood. This is called Type II or Adult Onset Diabetes.