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Ch 35 The Nervous System Organization of the Body • The levels of organization in a multicellular organism include – Tissues – groups of similar cells that perform a single function – Organ – a group of tissues that work together to perform a complex function – Organ System – group of organs that perform closely related functions Body Tissues • Four major types of tissues include – Epithelial – lines body cavities and covers body surfaces – Connective – provides support for the body and connects its parts – Muscle – contracts to allow movement – Nerve Tissue – transmits impulses to coordinate body system Maintaining Homeostasis • Homeostasis – maintaining a controlled, stable environment • Negative Feedback – a stimulus produces a response that opposes the original stimulus • Positive Feedback – a stimulus produces a response that enhances the original stimulus The Nervous System • Controls and coordinates functions throughout the body and responds to internal and external stimuli. • Cells that transmit the impulses are called neurons. • Sensory Neurons – carry information to the brain and spinal cord. • Motor Neurons – carry information away from the brain and spinal cord. • Interneurons – relay messages between sensory and motor neurons. Parts of a Neuron • Cell Body – main part; contains nucleus and cytoplasm; most metabolic activity occurs here • Dendrites – short, branched extensions that carry impulses toward the cell body • Axon – long extension that carries impulses away from the cell body • Myelin Sheath – fatty layer that covers many axons; insulates the neuron and speeds up the rate of impulses. • Nodes of Ranvier – gaps in the myelin sheath; impulses jump from node to node Nerve Impulses: Resting Potential • At rest, a neuron has a high concentration of K+ ions inside the cell. • A rest, a neuron has a high concentration of Na+ ions outside the cell. • Negatively charged proteins and Cl- ions are found inside the cell. • Resting Potential: the inside is negative with respect to the outside. Nerve Impulses: Action Potential • A stimulus will cause the membrane to change its permeability. • The membrane becomes very permeable to Na+ and Na+ rushes in. • The membrane then becomes permeable to K+ and K+ rushes out. • The cell becomes less negative on the inside. • This is the “action potential”. • The impulse is selfpropagating (causing the next point along the membrane to be activated). The Threshold of a Stimulus • Impulse strength is always the same. • The minimum level of a stimulus required to activate a neuron is the threshold. • Any stimulus stronger than threshold will produce an impulse. • Any stimulus weaker than threshold will produce no impulse. • A nerve impulse will produce an impulse or it will not produce an impulse (All-or-none principal). Synapses • A synapse is the place where an axon meets dendrites, a muscle cell, or a gland cell. • The end of a neuron (axon tip) releases chemical messengers called neurotransmitters. • Neurotransmitters cause an impulse to travel to the next cell. Divisions of the Nervous System • Central Nervous System (CNS) – brain and spinal cord • Peripheral Nervous System (PNS) – cranial and spinal nerves. – Autonomic Nervous System (ANS) – regulates involuntary activities The Brain • Cerebrum – largest part – Two hemispheres – Site of intelligence, learning, and judgment – Folds and grooves on surface increase surface area – Divided into lobes • Frontal • Parietal • Temporal • Occipital Cerebellum and Thalamus • Cerebellum – Coordinates and balances actions of the muscles • Thalamus – Receives messages from all sensory receptors and relays the information to the proper region of the cerebrum. Hypothalamus, Medulla, Pons • Hypothalamus – Control center fro recognition and analysis of hunger thirst, fatigue, anger, body temperature • Medulla Oblongata – Contains vital reflex centers (swallowing, breathing, heart rate) • Pons – Contains important respiratory centers that affect normal breathing reflex Spinal Cord & Reflex Arc • Link between brain and rest of body • Reflex – quick, automatic response to a stimulus • Allows body to respond to danger immediately; does not require brain! • Reflex Arc: – – – – – Receptor Sensory Neuron Interneuron Motor Neuron Affector (muscle, gland) Peripheral Nervous System • Made up of cranial nerves and spinal nerves • Sensory Division – carries info from sense organs to CNS • Motor Division – carries info from CNS to muscles and glands Autonomic Nervous System • Division of PNS • Two subdivisions – Sympathetic Division – speeds up body process; “fight-orflight” response – Parasympathetic Division – slows down body processes Ch 36 Skeletal, Muscular, and Integumentary Systems Functions of the Skeletal System • • • • Protect vital organs Store minerals Makes blood Aids movement (provides site for muscle attachment) • Framework for body Bone Structure • Periosteum – tough layer of surrounding connective tissue • Osteocytes – bone cells • Haversian Canals – provide means for blood vessels to get to bone cells • Bone Marrow – soft tissue – Yellow Marrow (fatty) – Red Marrow (makes blood cells) • Cartilage – reduces friction between bones at a joint • Compact bone • Spongy bone Bone Development • Embryonic skeleton starts off as bone • Eventually, it is replaced by bone tissue • Process called ossification • Ossification completed between ages of 18 – 25. Human Fetus 6 Weeks Bones of the Skeleton • Axial Division – Skull, Ribs, Sternum, Vertebrae • Appendicular Division – Shoulders, Arms, Hips, Legs • Use Diagram to Learn Bones Joints • Place where two bones meet • Immovable Joints – “fixed” joints; allow no movement; held by sutures or tightly with connective tissue • Slightly Movable Joints – slight movement • Freely Movable Joints – Ball-and-Socket – Pivot – Hinge Joints Miscellaneous (Bones) • • • • Ligaments – hold bones together at a joint Osteoporosis – weakening of bones Arthritis – inflammation of a joint Strain – damaged ligaments Types of Muscle Tissue • Skeletal Muscle – Has striped appearance – Voluntary – Found attached to bones • Cardiac Muscle – Has striped appearance – Involuntary – Found only in heart • Smooth Muscle – Has no striped appearance – Involuntary – Found in walls of hollow organs Muscle Structure • Myosin filaments – Thick proteins • Actin filaments – Thin proteins • Muscles contract because myosin pulls on actin. • Requires ATP Muscle Contraction • Neuromuscular Junction – where neuron and muscle cell meets • Acetylcholine – neurotransmitter released by neurons that triggers muscle contraction • Muscles can only pull on bones; not push! Muscle Names • Tendons – connect muscles to bone • Use diagram to learn muscles – – – – – – – – – – Biceps brachii Triceps brachii Rectus femoris Biceps femoris Rectus abdominis Pectoralis Trapezius Gastrocnemius Gluteus Maximus Deltoideus The Skin • Integumentary System includes skin, hair, nails, sweat glands, etc. • Functions – Barrier against infection and injury – Regulate body temperature – Remove waste – Protect against UV radiation – Makes Vitamin D Layers of the Skin • Epidermis – Outer layer – Outermost cells are dead and keratinized – Keratin is a protein that makes cells flat and water resistant – Inner cells are living, contain pigment called melanin – Does not contain nerve cells or blood cells. Layers of the Skin • Dermis – Inner layer – Lies beneath epidermis – Contains blood vessels, nerves, glands, hairs – Two types of glands • Sebaceous Glands – oil glands • Sweat glands Hair and Nails • Hair covers almost every body surface • Protects body and insulates • Hairs grow from the root • Nails grow from nail root • Fingernails grow about 4X faster than toenails. Ch 37 Circulatory and Respiratory Systems Functions of the Circulatory System • Circulates gases like oxygen and carbon dioxide • Circulates heat • Circulates water • Circulates nutrients, hormones, wastes • Blood is always red! Blood Composition • Plasma (55%) – yellowish – Mostly water – Contains dissolved nutrients, gases, wastes, etc. • Corpuscles (45%) – Erythrocytes – red cells; carry oxygen; hemoglobin – Leukocytes – white cells; immunity – Thrombocytes – platelets; coagulation Blood Transfusion Compatibility Type Antigens Antibody Can Give To Can Receive From A Type A Anti-b A, AB A, O B Type B Anti-a B, AB B, O AB Type A and Type B None AB All Types O None Both Anti-a All and Anti-b Types O Transfusions with Rh Factor examples Type Antigens Antibody Can Give To Can Receive From A+ Type A & Rh Anti-b A+, AB+ A+, O+,A-, O- B- Type B Anti-a, Anti-Rh B+, AB+, B-, AB- B-, O- AB+ Type A, Type B, and Type Rh None Type AB+ All Types O- None, Anti-Rh Both Anti-a and Anti-b All Types O- Blood Vessels • Arteries – Smaller diameter than veins – Higher BP than veins – Carry blood away from heart • Veins – Larger diameter than arteries – Lower BP than arteries – Carry blood toward heart • Capillaries – One cell thick – Only site for diffusion Circulation of Blood • See p. 944 The Heart Beat • There are two masses of nerve/muscle tissue in the heart that control the heart beat. • Both are located in the right atrium. • The SA Node (sinoatrial Node) – natural pacemaker; initiates beat • The AV Node (Atrioventricular Node) – causes ventricles to contract • Heart rate varies with activity Blood Pressure • Like any pump, the heart produces pressure. • When the heart contracts, it produces a wave of fluid pressure in the arteries. • Blood pressure decreases when the heart relaxes. • Device called sphygmomanometer measures BP. • The first number is the systolic pressure (pressure when ventricles contract) • The second number is the diastolic pressure (pressure when ventricles relax) • Normal reading 110 – 120/80 mmHg Diseases of the Circulatory System • Atherosclerosis – fatty deposits called plaque build up on the inner walls of arteries • High Blood Pressure – Also called hypertension; increases risk of heart attack or stroke • Heart Attack – blood flow to heart muscle blocked; heart muscle dies; symptoms include shortness of breath, nausea, chest pain The Respiratory System • The basic function is to bring about the exchange of oxygen and carbon dioxide between the blood, air, and tissues. • The respiratory system consists of the nose, pharynx, larynx, trachea, bronchi, and lungs. Parts of the Respiratory System • Nose – Hairs – Smell receptors – Mucus glands • Pharynx • Trachea – Epiglottis – Cartilage supports • Bronchi, Bronchioles • Alveoli Gas Exchange & Breathing • Gas exchange occurs only via the alveoli. • Inhalation – Diaphragm – Ribs & Sternum – Volume vs Pressure • Exhalation – Diaphragm – Ribs & Sternum – Volume vs Pressure Control of Breathing • Rate of breathing controlled by medulla oblongata. • Average breathing rate at rest 12 – 15 breaths per minute. • Affected by – Amount of CO2 in blood – Emotions – Exercise Tobacco & The Respiratory System • Nicotine is a stimulant that increases heart rate and blood pressure. • Carbon Monoxide is a poisonous gas that blocks the transport of oxygen by hemoglobin in the blood. It decreases the blood’s ability to supply oxygen to its tissues. • Tar has been shown to cause cancer. • Nicotine and CO paralyze the cilia of the airways. • Smoking causes the lining of the airway to swell, reducing air flow. • Emphysema is the loss of elasticity in the tissues of the lungs.