Unit 5 Review PDF

5.3​ Magnetic Resonance Imaging (MRI) Summary What is MRI? ​ Anatomical imaging based on the behavior of neutrons and protons (unlike X-rays, CTs, and PET scans). ​ Provides detailed soft tissue images but is poor at imaging bones. ​ ​ Built on the discovery of nu...

5.3​ Magnetic Resonance Imaging (MRI) Summary What is MRI? ​ Anatomical imaging based on the behavior of neutrons and protons (unlike X-rays, CTs, and PET scans). ​ Provides detailed soft tissue images but is poor at imaging bones. ​ ​ Built on the discovery of nuclear magnetic resonance (NMR) by Isidor I. Rabi(1937). ​ ​ Milestones: ​ ​ First MRI prototype by Raymond Damadian (1974). ​ ​ First human MRI scan (5 hours) by Damadian (1977). ​ ​ First modern MRI scanner by Paul Bottomley (1980). How Does MRI Work? ​ 1.​ Magnetic Field Application: ​ ​ Aligns hydrogen atoms in the body. ​ ​ Only atoms with odd numbers of protons or neutrons (e.g., Hydrogen-1) are detectable. 2.​ Radio Waves Emission: ​ ​ Alters hydrogen atom spin. ​ ​ Atoms release absorbed energy when returning to alignment, producing detectable signals. ​ 3.​ Signal Processing: ​ ​ Coil transmits signals to a computer. ​ ​ Data is processed into images using tissue-specific formulas. Patient Procedure: ​ ​ No eating or drinking 6 hours before an abdominal MRI. ​ ​ Remove all magnetic objects (jewelry, etc.). ​ ​ Lie still during the test (30 minutes to 2 hours). ​ ​ Scans are loud; earplugs may be provided. Functional MRI (fMRI): ​ ​ Maps brain activity by detecting changes in blood flow. ​ ​ Relatively new (first used in the 1990s). ​ ​ Measures oxygenated vs. deoxygenated blood to identify active brain regions. ​ ​ Color maps indicate areas of high neural activity. Benefits and Downfalls: ​ ​ All diagnostic tools have unique pros and cons depending on the situation, though specifics aren’t detailed here. 5.2​ The Nervous System Summary Function of the Nervous System: ​ ​ Master control and communication system, coordinating thoughts, emotions, and actions via electrical impulses. ​ Key Functions: ​ 1.​ Sensory Input: Detects changes inside/outside the body via sensory receptors. ​ 2.​ Integration: Processes sensory input and decides on actions. ​ 3.​ Motor Output: Activates muscles or glands (effectors) for a response. Structure of the Nervous System: ​ ​ Cells: ​ ​ Supporting Cells (Glia): Provide support, insulation, and protection but don’t transmit impulses. ​ ​ Neurons: Transmit impulses using their structure (cell body, dendrites, axon). ​ ​ Dendrites: Receive signals and carry impulses to the cell body. ​ ​ Axon: Carries impulses away to other neurons or effectors. ​ ​ Myelin Sheath: Fatty insulation that speeds up impulse transmission. ​ ​ Nodes of Ranvier: Gaps in the myelin where impulses “jump” for faster conduction. Types of Neurons: ​ 1.​ Sensory (Afferent): Carry input from receptors to the CNS. ​ 2.​ Interneurons: Found in the CNS, process sensory input and determine responses. ​ 3.​ Motor (Efferent): Carry impulses from the CNS to muscles/glands to trigger responses. Reflex Arc: ​ ​ Simplest nervous response involving: ​ 1.​ Receptor ​ 2.​ Sensory Neuron ​ 3.​ Interneuron (in the spinal cord) ​ 4.​ Motor Neuron ​ 5.​ Effector (e.g., muscle). ​ ​ Brain may or may not participate. Nerve Impulse (Action Potential): ​ 1.​ At Rest: Inside is negative, outside is positive due to sodium-potassium pump activity. ​ 2.​ Impulse Initiation: Stimuli open sodium channels, allowing Na+ in, causing depolarization. ​ 3.​ Impulse Transmission: Moves along the neuron as a wave. ​ 4.​ Repolarization: K+ exits the cell, restoring the resting potential. ​ ​ Impulse moves faster in myelinated fibers. Synapses: ​ ​ Space between neurons where neurotransmitters (e.g., dopamine) are released to carry signals across. ​ ​ Neurotransmitters are quickly broken down or reabsorbed to prevent continuous firing. Organization of the Nervous System: 1.​ Central Nervous System (CNS): Brain and spinal cord; interprets sensory info and sends commands. ​ 2.​ Peripheral Nervous System (PNS): Nerves outside the CNS; connects organs to the CNS. Regions of the Brain: ​ 1.​ Hindbrain: ​ ​ Medulla Oblongata: Controls vital involuntary actions (e.g., heartbeat, breathing). ​ ​ Pons: Relays signals between brain regions, aids in breathing. ​ ​ Cerebellum: Coordinates muscle movements, balance, and posture. ​ 2.​ Midbrain : Relays impulses between forebrain and hindbrain, and controls reflexes related to eyes and ears. ​ 3.​ Forebrain: ​ ​ Cerebrum: Largest part, controls voluntary actions, sensations, thoughts, and memory. ​ ​ Thalamus: Relays sensory signals to appropriate brain regions. ​ ​ Hypothalamus: Regulates homeostasis (e.g., temperature, hunger, hormones). Key Points on Action Potentials: ​ ​ All-or-none response: A stimulus must exceed the threshold to trigger an impulse. ​ ​ Impulses only move from axon terminals to dendrites due to neurotransmitter release at synapses. ​ Endocrine System Overview (5.4) ​ ​ Made up of glands that function as a communication/control system. ​ ​ Slower than the nervous system and relies on hormones. ​ Hormones ​ ​ Organic chemicals that affect target cells/tissues. ​ ​ Travel via the circulatory system to their target cells. ​ ​ Involved in reproduction, growth, stress response, metabolism, and more. ​ Hormone Actions ​ ​ Change plasma membrane permeability, protein synthesis, enzyme activation, mitosis, and secretory activity. ​ Classes of Hormones ​ ​ Steroid hormones: Lipid-soluble, bind inside the cell (e.g., estrogen, testosterone). ​ ​ Amino acid hormones: Water-soluble, bind to membrane receptors (e.g., insulin, growth hormones). ​ Control of Hormone Release ​ ​ Negative feedback regulates hormone levels in blood. ​ ​ Endocrine vs. Exocrine Glands ​ ​ Endocrine: Ductless, release hormones into blood (e.g., thyroid). ​ ​ Exocrine: Use ducts, secrete substances like sweat and enzymes (e.g., salivary glands). ​ Hypothalamus ​ ​ Controls endocrine glands and releases hormones like ADH. ​ Pituitary Gland ​ ​ Master gland that influences other glands. ​ ​ Releases hormones like HGH, FSH, LH, TSH, ACTH. ​ Thyroid Gland ​ ​ Controls metabolism via thyroid hormone. ​ ​ Calcitonin lowers blood calcium, Thyroxine controls cellular respiration. ​ Parathyroid Glands ​ ​ Regulate calcium levels in blood. ​ Thymus Gland ​ ​ Stimulates T-cell development, crucial for the immune system. ​ Pancreatic Islets ​ ​ Beta cells produce insulin, Alpha cells produce glucagon. ​ ​ Regulate blood glucose levels (insulin lowers, glucagon raises). ​  Adrenal Glands ​ ​ Adrenal cortex: Produces corticosteroids (e.g., aldosterone, cortisol). ​ ​ Adrenal medulla: Releases adrenaline (epinephrine) and noradrenaline for emergency responses. ​ ​ Testes and Ovaries ​ ​ Testes: Produce testosterone for male traits. ​ ​ Ovaries: Produce estrogen and progesterone for female traits and menstrual cycle regulation.