Download Introduction To Physiology ~ LECTURE NOTES

Introduction To Physiology ~ LECTURE NOTES WEEK ONE: INTRODUCTION TO PHYSIOLOGY, HOMEOSTASIS AND THE NERVOUS SYSTEM Physiology = functions of the human body. Comparative physiology is the study of different species; it is the basis for the development of new drugs and medical procedures Homeostasis •
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Homeostasis is the process of maintaining a constant internal environment despite the changing external environment. Maintaining homeostasis is absolutely vital to an organisms survival Claude Bernard (1813-­‐78): stable internal conditions regardless of external conditions. Walter Cannon (1871-­‐1945) coined the term ‘homeostasis’: it fluctuates within limited range around a set point Homeostasis mechanisms: 1. Receptor-­‐ sensitive to environmental change 2. Control centre-­‐ receives and processes the information supplied by the receptor and sends out commands 3. Effector – responds to commands by opposing the stimulus Room temperature does not stay at set point, it oscillates around the set point; this is the same for homeostatic control The body is said to be in homeostasis when its cellular needs are adequately met and functional activities are occurring smoothly. Every organ system plays a role in maintaining the internal environment Feedback occurs when receptor stimulation triggers a response that changes the environment at the receptor Negative feedback is when an effector activated by the control center opposes the original stimulus; it tends to minimise change In positive feedback, an initial stimulus produces a response that enhances the change in the original conditions. It accelerates a process to completion. The Nervous System •
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Master control and communication centre. Every though, action, and emotion involves the NS 3 overlapping functions: sensory input, integration and motor output Subdivisions of the Nervous System: 1. Central Nervous System (CNS): brain and spinal cord 2. Peripheral Nervous System (PNS): nerves (spinal and cranial) and ganglia Divisions of PNS: Sensory division = visceral sensory (from visceral organs) or somatic sensory (from skin, skeletal muscles and joints) Motor division = somatic motor (nerve fibres conduct impulse from CNS to skeletal muscles, voluntary or involuntary in somatic reflexes) or autonomic motor (nerve fibres regulate activity of smooth muscles, cardiac muscles and glands, consists of •
the sympathetic division-­‐ “fight-­‐or-­‐flight” and the parasympathetic division-­‐ “resting and digesting”) Functional types of neurons: 1. Sensory (afferent) neurons: detect changes in the body and external environment. Information is transmitted into the brain or spinal cord 2. Interneurons (association neurons): lie between the sensory and motor pathways in the CNS. Make up 90% of our neurons. They process, store and retrieve information 3. Motor (efferent) neurons: send signals out to effectors which carry out the response