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Human Body Systems • Organization of the Body (Review) • • • • • • Basic unit of structure and function Tissues • Group of cells that perform a single function (e.g. epithelial, connective, nervous, muscle) Organs • Different types of tissues that work together to perform a closely related function (e.g. eye, liver, lungs) Organ Systems • Group of organs that perform closely related functions (e.g. circulatory, respiratory, digestive) Homeostasis • • • • Cells Definition: the process by which organisms keep internal conditions relatively constant despite changes in their external environments Requires the integration of all organ systems at the same time Nervous system in conjunction with the endocrine system (hormones) is responsible for this integration Positive feedback – your body’s response results in an increase in the effect of the stimulus, (e.g. the flight-fight response) Nervous System • Recognizes and coordinates the body’s response to changes in its internal and external environments. • General Functions of the Nervous System • Sensory input – vision, hearing, balance, smell, taste, and touch • • • Motor output – muscle contraction and movement Memory and integration of information Division of Labor • • Central Nervous System (CNS) Control center of the body that relays messages, and processes and analyzes information • Brain • • • Cerebrum – largest region; right and left hemispheres that are connected by corpus callosum; voluntary activities and higher brain functions Cerebellum – located at the lower back part of brain; coordination and balance Brain stem – connects the brain and spinal chord; two regions: pons and medulla oblongata, control breathing, heart rate and swallowing •Thalamus: Thalamus and hypothalamus - between brain stem and cerebrum relay station for sensory info Hypothalamus: most important homeostatic site; hormones, body’s thermostat, fight or flight, thirst, hunger, reproduction • Spinal Cord Two main functions: • • Processing of simple responses to certain stimuli (reflexes) Carries info to and from brain to body • • Peripheral Nervous System (PNS) Receives information from the environment and relays to and from CNS and sensory, motor and gland cells Two divisions: • • Sensory - Made of sensory neurons that bring info to the CNS Motor - Made of sensory neurons that convey info from the CNS; two subdivisions • • Somatic (voluntary): respond to external stimuli Autonomic (involuntary): respond to internal stimuli w/the parasympathetic and sympathetic divisions • • • Parasympathetic ↓energy consumption Autonomic Overview Movie Neurons (Nerve Cells) • • Specialized cells that carry electrical signals called impulses (Draw Fig. 35-5; pg. 897) 3 Types of Neurons: • • • • Sympathetic ↑energy consumption Sensory – carry impulses from the sense organs to the spinal cord and brain Motor – carry impulses from brain and spinal cord to muscles and glands Interneurons – Connect sensory and motor neurons and carry impulses between them Anatomy of a Neuron • Cell Body • • Largest part of the neuron Contains the nucleus and most of the cytoplasm • • • • • • Carry impulses from the environment or other neurons to the cell body Long fiber that carries impulses from the cell body Ends in axon terminals that contain vesicles for neurotransmitters Myelin Sheath • • • Insulates the axon Gaps in the myelin sheath allow an impulse to jump from node to node, thus increasing its speed The Nerve Impulse The Resting Neuron • • • • Dendrites Axon • • Metabolic activity takes place in the cell body At rest, the inside has a the resting (-70mVolts, outside of the cell has a net positive charge and the net negative charge. This charge difference is called potential. about 5% of the voltage in AA battery) The charge difference is created by active transport of ions across the cell membrane via the sodium-potassium pump. Sodium ions (Na+) are pumped outside the cell and potassium (K+) ions are pumped into the cell. The Moving Impulse • • An impulse begins when a neuron is stimulated by the axon of another neuron or by the environment. Na+ pores open and the flood of Na+ ions makes the inside positive. This reversal of charges, from negative to positive is called a nerve impulse, or an action potential. • • Nerve Impulse Pathway Overview • Impulse is received by the dendrites from the environment or another neuron, then gets rapidly channeled through the cell body to the axon • Axon branches out into axon terminals, which contain tiny vesicles filled with neurotransmitters, which are chemicals used by a neuron to transmit an impulse to another cell. (e.g. acetylcholine, serotonin, dopamine and adrenalin). • Vesicles release neurotransmitters into the open space between neurons called the synapse. • • As the impulse passes, K+ pores open and K+ flows out which restores the resting potential (charge difference) The neurotransmitters diffuse across the synapse and attach themselves to receptors on dendrite of neighboring cell Reflexes • • • Reflexes are automatic responses to stimuli Controlled by 5-part reflex arc: • • • • • Sensory receptors on finger reacts to stimulus (heat) Impulse is carried to the spinal cord by a sensory neuron In the spinal cord, the impulse is transferred by an interneuron to motor neuron Motor neurons conducts the impulse to an effector (arm muscles) Effector responds to the impulses by contracting (hand gets pulled away from the heat) The Senses 5 General Sensory Receptors: pain, thermo-, mechano-, chemoand photoreceptors. Vision • • Hearing and Balance Smell and Taste • • Nervous System Disorders • • • • • Touch Migraine Headaches – caused by change in serotonin levels? (affected by caffeine, estrogen, certain foods) Parkinson’s –caused by damage to dopamine transmitters; causes uncontrollable shaking, no cure Tay-Sachs –lack enzyme to break down fatty deposits in the brain; neurological deterioration; death by age 4-5 Dementia - damaged brain cells caused by injury or disease (Alzheimer’s); memory loss and personality change. Drugs and the Nervous System • • Stimulants • • • • • • Accelerate HR, BP, and breathing rate Increases the release of neurotransmitters; leads to release of energy and feeling of well-being When effect wears off, brain’s supply is depleted Caffeine Cocaine Methamphetamines Depressants • • • • Slow down HR, lower BP and breathing rate, relax muscles and relieves anxiety Alcohol Marijuana Sleeping Pills