HUMAN BIOSCIENCES A (HBS1HBA) NOTES

Transcription

1 HUMAN BIOSCIENCES A (HBS1HBA) NOTES 1.1 ANATOMY AND PHYSIOLOGY DEFINED (LO 1) Anatomy the structure or study of the structure of the body and the relationship of its parts to each other. Physiology science that deals with the functions of an organism or its parts how the body parts work. The structure of a part of the body often reflects its functions The bones of the skull join tightly (structure) to form a rigid case protecting the brain (function) The bones of the fingers are more loosely joined (structure) to allow a variety of movements (function) The walls of the air sacs in the lungs are very thin (structure), allowing for rapid movement of inhaled oxygen into the blood (function)

2 1.2 LEVELS OF STRUCTURAL ORGANISATION AND BODY SYSTEMS (LO 2) 1. Chemical level: Basic level can be compared to the letters of the alphabet Includes atoms (smallest units of matter that participate in chemical reactions) and molecules (two or more atoms joined together) Carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), calcium (Ca), and sulphur (S) are atoms essential for maintaining life DNA (genetic material passed from one generation to the next) and glucose (blood sugar) are two familiar molecules found in the body Atoms combine to form molecules, which combine to form cells

3 2. Cellular level: Can be compared to words which are the smallest elements of language that make sense much like cells which are the smallest living units in the human body. There are muscle cells, nerve cells and epithelial cells (cells that line hollow organs and glands) 3. Tissue level: Can be compared to sentences the materials surrounding tissues work together to perform a particular function, much like the way words are put together to form sentences Four basic types of tissue: Epithelial tissue covers body surfaces, lines hollow organs and cavitities, and forms glands Connective tissue connects, supports, and protects body organs while distributing blood vessels to other tissues Muscular tissue contracts to make body parts move and generates heat Nervous tissue carries information from one part of the body to another through nerve impulses 4. Organ level: Can be compared to the relationship between sentences and paragraphs as different types of tissues (sentences) are joined together to form an organ (paragraph)! Composed of two or more different types of tissues

4 Have specific functions and recognisable shapes Eg. The stomach, skin, bones, heart, liver, lungs and brain The stomach s outer covering is a layer of epithelial tissue and connective tissue that reduces friction when the stomach moves and rubs against other organs (serous fluid is also responsible for allowing free movement of organs in body cavities) Underneath there are 3 layers of a type of muscular tissue called smooth muscle tissue, which contracts to churn and mix food and then push it into the next digestive organ, the small intestine The innermost lining is the epithelial tissue layer that produces fluid and chemicals responsible for digestion in the stomach 5. System level: Can be compared to a chapter as a system (chapter) consists of related organs (paragraphs) with a common function Also called the organ-system level Eg. Digestive system breaks down and absorbs food The organs in the digestive system include the mouth, salivary glands, pharynx (throat), oesophagus (food tube), stomach, small intestine, large intestine, liver, gall bladder and pancreas Sometimes an organ is part of more than one system eg. The pancreas is part of both the digestive and the hormone-produing endocrine system 6. Organismal level: Can be compared to a book as an organism (book) consists of many systems (chapters) OVERALL ANALOGY: Chemical cellular tissue organ system organismal Alphabet words sentences paragraphs chapters book A molecule is made up of 2 or more atoms molecules combine to form cells cells work together to form tissues tissues join together to form organs related organs join together to form systems all the systems of the body put together forms an organism

5 ACTION POTENTIAL (LO7) Electrical events that are conducted along the entire length of a nerve cell s axon Means of communication along a neuron The generation of a new action potential occurs when an sodium ion (Na+ or K+) from the depolarisation of the previous action potential reaches the Node of Ranvier in the axon, triggering the opening of the voltage-gated channels in the NoR for the sodium ions to enter through, thus leading to the generation of a new action potential Action potentials move forward in one direction only, therefore only sodium ions that travel forwards can trigger an action potential Sodium ions that travel backwards cannot travel through the voltage-gated channels along the axon as the channel would become inactive, not allowing for anymore sodium ions that are travelling backwards to enter the cell, preventing the cell from becoming more positively charged purpose of the inactivation of voltage-gated channels List the major events that occur in an action potential and state whether movement of sodium or potassium ions into or out of the cell are responsible for each event. Action potentials don t always occur, the depolarising stimulus (EPSPs) must bring membrane to threshold value (graded potentials (EPSPs) are responsible for this) for an action potential to occur this is determined by the axon hillock (trigger zone of the axon)

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7 SIGNAL TRANSMISSION AT SYNAPSES (LO8) Describe how neurons communicate with each other by chemical signalling molecules released at the synapse. What is a synapse? A synapse is a region where communication occurs between to neurons or between a neuron and an effector cell (muscle or gland cell) Allows us to modify what happens at the site of an action potential (when it travels) There are often multiple presynaptic neurons stimulating the postsynaptic neuron Presynaptic neuron: Nerve cell that carries a nerve impulse towards a synapse Sends a signal to the postsynaptic neuron Postsynaptic neuron: Carries a nerve impulse away from a synapse or an effector cell that responds to the impulse at the synapse Receives the signal from the presynaptic neuron Most synapses are axodendritic from axon to dendrite Others are axosomatic from axon to cell body Or axoaxonic from axon to axon

8 THE HEART (LO 1) State the major structures of the heart and the function of each. Organ of the cardiovascular system responsible for pumping blood throughout the body; located in the thoracic cavity superior to the diaphragm The heart lies in the mediastinum (extends from the sternum to the vertebral column)

9 PERICARDIUM: The membrane that surrounds and protects the heart Allows sufficient freedom of movement for vigorous and rapid contractions Consists of two main parts (fibrous and serous pericardium): Fibrous pericardium (triple-layered sac): Composed of tough, irregular connective tissue Prevents overstretching of the heart Provides protection Anchors the heart in the mediastinum CHAMBERS OF THE HEART: The heart has four chambers: Two superior receiving chambers the ATRIA Receive blood from blood vessels returning blood to the heart VEINS Relatively thin, small-walled chambers as they only need to contract blood downwards (following gravity) to the ventricles Two inferior pumping chambers VENTRICLES Eject blood from the heart into blood vessels ARTERIES Make up most of the volume of the heart THE RIGHT ATRIUM: Forms the right surface of the heart Receives blood from three veins: superior vena cava, inferior vena cava and coronary sinus Blood flows into the right atrium through the superior vena cava, inferior vena cava and coronary sinus into the left atrium through four pulmonary veins