Body Regulators PDF

Living Things and Their Environment Unit III Body Regulation Chapter VIII LESSON COMPETENCIES: 1. Give the importance of homeostasis in the body. 2.Explain the role of nervous and endocrine systems in maintaining homeostasis. 3.Enumerate some disorders associated with the nervous and endo...

Living Things and Their Environment Unit III Body Regulation Chapter VIII LESSON COMPETENCIES: 1. Give the importance of homeostasis in the body. 2.Explain the role of nervous and endocrine systems in maintaining homeostasis. 3.Enumerate some disorders associated with the nervous and endocrine systems. Nervous System Lesson 8.1  NERVOUS SYSTEM The nervous system is the major controlling, regulatory, and communicating system in the body. It is the center of all mental activity including thought, learning, and memory. Together with the endocrine system, the nervous system is responsible for regulating and maintaining homeostasis. STIMULUS-RESPONSE COORDINATION STIMULUS-RESPONSE COORDINATION STIMULUS IS ANYTHING THAT EVOKES A PERSON’S REACTION. EVERY STIMULI REQUIRES THE BODY TO REPOND. STIMULUS-RESPONSE COORDINATION  STIMULUS-RESPONSE COORDINATION The body has several internal control system that maintain HOMEOSTASIS. HOMEOSTASIS is the body’s ability to maintain constant internal equilibrium by adjusting its physiological process.  NERVOUS SYSTEM The nervous system is essential for communication within the body. The brain and the body receive signals and process internal or external information to control body responses.  NEURONS Neurons are cells in the brain and nervous system that transmit electrical and chemical signals to other neurons, muscles, and tissues throughout the body. Neurons have three main parts: Dendrites: The "arms" of the neuron, which are branch extensions that come out of different parts of the neuron. Cell body: The center of the neuron. Axon: An elongated fiber that extends from the cell body to the terminal endings and transmits the neural signal.  Classes of neurons Based on their roles, the neurons found in the human nervous system can be divided into three classes: sensory neurons, motor neurons, and interneurons. Sensory neurons Sensory neurons get information about what's going on inside and outside of the body and bring that information into the CNS so it can be processed. For instance, if you picked up a hot coal, sensory neurons with endings in your fingertips would convey the information to your CNS that it was really hot.  Motor neurons Motor neurons get information from other neurons and convey commands to your muscles, organs and glands. For instance, if you picked up a hot coal, it motor neurons innervating the muscles in your fingers would cause your hand to let go. Interneurons Interneurons, which are found only in the CNS, connect one neuron to another. They receive information from other neurons (either sensory neurons or interneurons) and transmit information to other neurons (either motor neurons or interneurons).  For instance, if you picked up a hot coal, the signal from the sensory neurons in your fingertips would travel to interneurons in your spinal cord. Some of these interneurons would signal to the motor neurons controlling your finger muscles (causing you to let go), while others would transmit the signal up the spinal cord to neurons in the brain, where it would be perceived as pain. Transmission of Nerve Impulses  Synapses Neuron-to-neuron connections are made onto the dendrites and cell bodies of other neurons. The sites at which information is carried from the first neuron, the presynaptic neuron, to the target neuron (the postsynaptic neuron).  There are two types of synapses: Electrical synapse: A direct electrical connection is made between neurons. Chemical synapse: Ions flow between cells.  Synapses process Axon splits into multiple branches upon approaching a synapse. These branches terminate into synaptic knob that is connected to either main parts of the neuron. Hormonal secretion enable the propagation of nerve impulses from the synapse.  Neurotransmitters Neurotransmitters are chemical messengers that neurons release to affect other cells across a synapse. The cells that receive the signal are called target cells, and they can be neurons, glands, or muscle cells. Some examples of neurotransmitters and their functions: Serotonin: Regulates mood, anxiety, happiness, appetite, sleep, memory, and learning Acetylcholine: Helps translate intentions to move into actual actions by passing signals from neurons into muscle fibers. Dopamine: Helps nerve cells send messages to each other Norepinephrine: Involved in arousal, alertness, memory, and attention, and triggers the "fight-or-flight" response. Endorphins: Stimulates neurons involved in reducing pain. The Reflex A reflex action is an automatic, involuntary, and rapid response to a stimulus that helps protect the body from harm. Reflex actions occur through neural pathways in the nervous system called reflex arcs. The spinal cord and peripheral nervous system coordinate to produce reflex actions, and the brain is not involved. Some examples of reflex actions: Pulling away from a hot object: When you touch something hot, your hand immediately pulls away. Adjusting your eyes to bright light: When exposed to bright light, your eyes adjust automatically. Withdrawing your hand or leg after being pricked by a pin: You suddenly and involuntarily withdraw your hand or leg. Coughing or sneezing: When an irritant is present in your trachea or nose, you cough or sneeze to expel it. DIVISION OF NERVOUS SYSTEM  Central Nervous System (CNS) The central nervous system (CNS) is made up of the brain and spinal cord. The CNS is the body's processing centre. The brain controls most of the functions of the body, including awareness, movement, thinking, speech, and the 5 senses.  BRAIN AND SPINAL CORD Brain The brain is a complex organ that controls most of the body's activities, including thought and behavior. Spinal cord The spinal cord is a tube-like structure that carries messages between the brain and the rest of the body. MAJOR PARTS OF THE BRAIN The brain structure is composed of three main parts: the forebrain, midbrain and hindbrain, each with multiple parts. SPINAL CORD A column of nerve tissue that runs from the base of the skull down the center of the back. It is covered by three thin layers of protective tissue called membranes.  Peripheral Nervous System (PNS) The peripheral nervous system is a network of nerves that runs throughout the head, neck, and body. It carries messages to and from the central nervous system (the brain and spinal cord). The primary peripheral nervous system function is to relay messages back and forth from the central nervous system (CNS), the nervous system made up of the brain and spinal cord. The muscles, glands, and organs that the PNS transmits signals to from the CNS are known as effectors.  Two main divisions of the PNS Somatic nervous system Autonomic nervous system Controls voluntary Regulates involuntary body muscle movement functions, such as those of and includes sensory the heart, lungs, and and motor neurons intestines. that send and receive information. Autonomic Nervous System The autonomic nervous system is further divided into the sympathetic and parasympathetic systems, which have complementary functions that work together to maintain homeostasis.  Sympathetic nervous system (SNS) Prepares the body for physical and mental activity, such as in times of danger or stress. This system activates the body's "fight-or-flight" response, increasing heart rate, opening airways, and inhibiting digestion. The SNS releases the hormones epinephrine and norepinephrine to accelerate the heart rate. Parasympathetic nervous system (PNS) Responsible for bodily functions when the body is at rest, such as digestion, relaxation, and metabolic processes. This system activates the body's "rest-and-digest" response. The PNS releases the hormone acetylcholine to slow the heart rate. SNS & PNS The two systems work together to keep the body in balance. The SNS takes the lead when the body needs to get through a period of danger, and then the PNS returns things to normal. However, the SNS can strain body systems if it's active for too long.