Human Anatomy & Physiology - 2 (HMG381) PDF

Week 3; Session 1 Human Anatomy & Physiology - 2 (HMG381) Maintaining Homeostasis - Role of Nervous System & Endocrine System Dr. Merin Thomas [email protected] Office hours : Monday & Wednesday - 9.00am to 10.30am Tuesday & Thursday - 10.45am to 12.30pm Learning Objectives Overview of the E...

Week 3; Session 1 Human Anatomy & Physiology - 2 (HMG381) Maintaining Homeostasis - Role of Nervous System & Endocrine System Dr. Merin Thomas [email protected] Office hours : Monday & Wednesday - 9.00am to 10.30am Tuesday & Thursday - 10.45am to 12.30pm Learning Objectives Overview of the Endocrine system Overview of the Nervous system Integration of endocrine and nervous system Role of endocrine and nervous system homeostasis in OVERVIEW OF THE ENDOCRINE SYSTEM NAMES AND LOCATION OF GLANDS OVERVIEW OF THE ENDOCRINE SYSTEM It is a complex network of glands and other organs. Uses hormones to control and coordinate your body's metabolism, energy level, reproduction, growth and development, and response to injury, stress, and mood A hormone is a molecule that is released in one part of the body but regulates the activity of cells in other parts of the body. Most hormones enter interstitial fluid and then the bloodstream. The circulating blood delivers hormones to cells throughout the body. Hormones travel throughout the body in the blood BUT it affects only specific target cells. - RECEPTORS OVERVIEW OF THE ENDOCRINE SYSTEM - HORMONES Control of Hormone Secretion The release of most hormones occurs in short bursts, with little or no secretion between bursts. When stimulated, an endocrine gland will release its hormone in more frequent bursts, increasing the concentration of the hormone in the blood. In the absence of stimulation, the blood level of the hormone decreases. Regulation of secretion normally prevents over-production or underproduction of any given hormone to help maintain homeostasis. ENDOCRINE SYSTEM & HOMEOSTASIS The hormones of the endocrine system contribute to homeostasis by regulating the activity and growth of target cells in your body. Hormones also regulate metabolism. OVERVIEW OF THE NERVOUS SYSTEM The nervous system is one of the the most complex of the body systems. This intricate network of billions of neurons and even more neuroglia is organized into two main subdivisions: The Central nervous system The Peripheral nervous system COMPARISON BETWEEN SOMATIC & AUTONOMIC NERVOUS SYSTEM The somatic nervous system includes processes that are perceived or consciously controlled The autonomic nervous system includes processes regulated below the conscious level COMPARISON BETWEEN SOMATIC & AUTONOMIC NERVOUS SYSTEM DIVISIONS OF THE AUTONOMIC NERVOUS SYSTEM DIVISIONS OF THE AUTONOMIC NERVOUS SYSTEM OVERVIEW OF THE NERVOUS SYSTEM The nervous system carries out a complex array of tasks. These diverse activities can be grouped into three basic functions NERVOUS TISSUE The Nervous tissue comprises two types of cells Neurons - Highly specialized cells; connect all regions of body to brain & spinal cord; lost ability to undergo mitosis Neuroglia - support, nourish, and protect neurons; Much more in number than neurons; continue to divide throughout lifetime NERVOUS TISSUE - TERMINOLOGY nerve cell bodies Nerve cell bodies ELECTRICAL SIGNALS IN A NEURON Neurons are electrically excitable. They communicate with one another using two types of electrical signals: 1. Graded potentials - used for short-distance communication only. 2. Action potentials - allow communication over long distances within the body. ELECTRICAL SIGNALS IN A NEURON Signal transmission at Synapses A synapse is the functional junction between one neuron and another, or between a neuron and an effector such as a muscle or a gland. Synapses are essential for homeostasis because they allow information to be filtered and integrated. ELECTRICAL SIGNALS IN A NEURON Signal transmission at Synapses - Electrical Synapse - Action potentials conduct directly between the plasma membranes of adjacent neurons through structures called gap junctions. Electrical synapses have two main advantages Faster communication Synchronization ELECTRICAL SIGNALS IN A NEURON Signal transmission at Synapse - Chemical Synapse The plasma membranes of presynaptic and postsynapic neurons in a chemical synapse are close but they do not touch - separated by the synaptic cleft, a space that is filled with interstitial fluid. Nerve impulses cannot conduct across the synaptic cleft, so an alternative, indirect form of communication occurs. In response to a nerve impulse, the presynaptic neuron releases a neurotransmitter that diffuses through the fluid in the synaptic cleft and binds to receptors in the plasma membrane of the postsynaptic neuron. The postsynaptic neuron receives the chemical signal and in turn produces a postsynaptic potential, a type of graded potential. NEUROTRANSMITTORS Chemical messengers - molecules used by the nervous system to transmit messages between neurons, or from neurons to muscles. Some neurotransmitters bind to their receptors and act quickly to open or close ion channels in the membrane. Others act more slowly via second-messenger systems to influence chemical reactions inside cells. The result of either process can be excitation or inhibition of postsynaptic neurons. Name of Neurotransmitter Effect Acetylcholine Excitatory neurotransmitter/ inhibitory neurotransmitter - depends on receptor Glutamate Predominantly an excitatory neurotransmitter Aspartate Predominantly an excitatory neurotransmitter Gammaaminobutyric acid (GABA) Predominantly an inhibitory neurotransmitter Glycine Predominantly an inhibitory neurotransmitter Epinephrine Excitatory neurotransmitter/ inhibitory neurotransmitter - depends on receptor Norepinephrine Excitatory neurotransmitter/ inhibitory neurotransmitter - depends on receptor NERVOUS SYSTEM & HOMEOSTASIS The excitable characteristic of nervous tissue allows for the generation of nerve impulses (action potentials) that provide communication with and regulation of most body organs. Regulates body activities by responding rapidly using nerve impulses Responsible for our perceptions, behaviors, and memories, and it initiates all voluntary movements. The spinal cord and spinal nerves contribute to homeostasis by providing quick, reflexive responses to many stimuli. The pathway for sensory input to the brain and motor output from the brain. NERVOUS SYSTEM & HOMEOSTASIS The brain contributes to homeostasis by receiving sensory input, integrating new and stored information, making decisions, and executing responses through motor activities. The autonomic nervous system contributes to homeostasis by conveying motor output from the central nervous system to smooth muscle, cardiac muscle, and glands for appropriate responses to integrated sensory information. COMPARISON OF CONTROL BY NERVOUS SYSTEM & ENDOCRINE SYSTEM The nervous and endocrine systems act together to coordinate functions of all body systems. CHARACTERISTIC SIGNALLING MOLECULES SITE OF ACTION NERVOUS SYSTEM Neurotransmitters released locally in response to nerve impulses. Hormones delivered to tissues throughout body by blood. Close to site of release, at synapse; binds to receptors in postsynaptic membrane. Far from site of release (usually); binds to receptors on or in target cells. Muscle (smooth, cardiac, and skeletal) TYPES FO TARGET fibers, gland cells, other neurons. CELLS TIME OF ONSET OF Typically within milliseconds ACTION DURATION OF ACTION ENDOCRINE SYSTEM Generally briefer (milliseconds) Cells throughout body. Seconds to hours or days. Generally longer (seconds to days). Table 18.1, Comparison of Control by the nervous and endocrine system; Principles of Anatomy and Physiology , 16th edition, authored by Gerard J. Torto INTEGRATION OF NERVOUS SYSTEM & ENDOCRINE SYSTEM The body uses both electrical and chemical systems to create homeostasis. The brain relies on chemical messengers sent by the endocrine system to transmit instructions around the body via the nervous system to key organs for growth and metabolism. Together with hormones from the endocrine system, nerve impulses provide communication and regulation of most body tissues. Together with the nervous system, circulating and local hormones of the endocrine system regulate activity and growth of target cells throughout the body. HYPOTHALAMUS is the link between the nervous system and the endocrine system. (Sargis, 2021) Through the production of releasing and inhibiting hormones, the hypothalamus controls the production and/or inhibition of hormones across the body One of the main functions of the hypothalamus is to maintain homeostasis Hypothalamus maintains homeostasis either by stimulating the ANS or by stimulating/inhibiting hormones In order to maintain homeostasis, the hypothalamus influences key processes in the body; many of them through the endocrine system Heart rate & blood pressure Body temperature Fluid and electrolyte balance, including thirst Appetite and body weight Glandular secretions of the stomach and intestines Production of substances that influence the pituitary gland to release hormones Sleep cycles Heart rate Cardiovascular center in the medulla oblongata provides nerve impulses to ANS that govern heart rate and the forcefulness of the heartbeat Epinephrine and norepinephrine increase heart rate and force of contraction Blood Pressure Nerve impulses from ANS also regulate blood pressure and blood flow through blood vessels ANS regulates secretion of hormones from suprarenal medulla and pancreas Aldosterone and antidiuretic hormone increase blood volume Several hormones elevate blood pressure during exercise and other stresses Sleep Cycles - Sleep is a complex and dynamic process that affects how one functions Many structures within the brain play an important role in the sleep cycles The hypothalamus - contains groups of nerve cells that act as control centers affecting sleep and arousal. The brain stem, at the base of the brain, communicates with the hypothalamus to control the transitions between wake and sleep. The thalamus acts as a relay for information from the senses to the cerebral cortex The pineal gland, located within the brain’s two hemispheres, receives signals from the neurons in the hypothalamus and increases production of the hormone melatonin, which helps sleep once the lights go down. OTHER STRUCTURES WITHIN BRAIN ALSO INVOLVED, NOT MENTIONED HERE (Brain Basics: Understanding Sleep, n.d.) ACTIVITES & ASSIGNMENTS Quiz 1 On MONDAY, March 11th 2023 (33/77) & TUESDAY March 12th 2024 (22/66) (Week 4.1) Portions: Anatomical terminology, planes & regions, Levels of structural organization, Homeostasis, Interaction and Interdependence of organ systems, Maintenance of homeostasis (Weeks 1-3.1) Assignment Submission On MONDAY, 18th March 2023; 11.59pm (22/66) & (33/77) (Week 5) ACTIVITES & ASSIGNMENTS Any doubts regarding assignment? REFERENCES Tortora, Gerard J. And Bryan H Derrickson. Principles of Anatomy and Physiology. John Wiley & Sons, 2020 McKinley, M., & O’Loughlin, V. (2020). Human Anatomy (6th ed.). McGraw-Hill Higher Education (International). Standring, Susan. Gray’s Anatomy E-Book. Elsevier Health Sciences, 2015 Sargis, R. M. (n.d.). An Overview of the Hypothalamus. Endocrineweb. https://www.endocrineweb.com/endocrinology/overview-hypothalamus Brain Basics: Understanding Sleep. (n.d.). National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/health-information/public-education/brain-basics/brain- basics-understanding-sleep Stangor, C., & Walinga, J. (2018). Putting It All Together: The Nervous System and the Endocrine System. Introduction to Psychology: 1st Canadian Edition. B.C. Open Textbook Project. https://opentextbc.ca/introductiontopsychology/chapter/3-4-putting-it-all-together-thenervous-system-and-the-endocrine-system/