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The Brain and Neurons Copy everything in RED and draw/label when told to Levels of Organization (copy the pyramid) • Organ systems are living things made of a group of organs that contribute to a specific function within the body. • Organs are living things made of tissues that work together to perform a specific, complex function. • Tissues are living things made of a group of cells with similar structures and functions. • Cells are the smallest unit of life. Types of Tissues • Different tissue types work together within organs: • Muscle tissue (most abundant): controls internal movements of materials (ex: blood, food) • Epithelial tissue: closely packed cells covering the surface of the body and line internal organs (ex: inside chambers of heart, glands) • Connective tissue: holds organs in place and binds different parts of the body together (ex: tendons, ligaments) • Nervous tissue: receives messages from the body’s external and internal environments, analyzes the data, and directs response (ex: controls heart beat) Figure 35-2 Human Organ Systems Part I Section 35-1 Nervous System Integumentary System Skeletal System Muscular System Circulatory System Figure 35-2 Human Organ Systems Part 2 Section 35-1 Respiratory System Endocrine System Digestive System Reproductive System Excretory System Lymphatic System 11 Functions • Nervous: coordinates the body’s response to change in the internal and external environments. • Integumentary: serves as a barrier against infection and injury, helps to regulate body temperature, provides protection against UV radiation from the sun • Respiratory: provides oxygen needed for cellular respiration and removes excess carbon dioxide from the body Neurons • Messages carried by the nervous system are electrical signals = impulses • Nerve cells that transmit impulses = neurons • Sensory neurons: carry impulses from sense organs to the spinal cord and brain • Motor neurons: carry impulses from the brain and spinal cord to muscles and glands • Interneurons: connect sensory and motor neurons and carry impulses between them Parts of a Neuron • Cell body = largest part containing nucleus and cytoplasm (most metabolic activity occur here) • Dendrites = short, branched extensions spreading out from the cell body and they carry impulses from the environment or other neurons towards the cell body • Axon = long fibers that carry impulses away from the cell body and ends at the axon A Neuron DRAW and LABEL THIS Section 35-2 Nucleus Axon terminals Cell body Myelin sheath Nodes Axon Dendrites Synapse • At the end of the neuron, the impulse reaches an axon terminal where the impulse may be passed along to another neuron or another cell • The location where a neuron can transfer an impulse to another cell = synapse • The synapse is a small gap that separates the axon terminal from the dendrites of the next neuron or another cell • The terminals contain tiny sacs or vesicles filled with neurotransmitters = chemicals used by a neuron to transmit an impulse across a synapse • The impulse will continue with the stimulation exceeds the cell’s threshold Figure 35-8 The Synapse Section 35-2 Direction of Impulse Dendrite of adjacent neuron Axon Vesicle Receptor Axon terminal Synaptic cleft Neurotransmitter Reaction activity • Reaction time = the amount of time required for an impulse travel from your sensory neurons to your motor neurons Brain and Spinal cord • Both are • protected by bone • wrapped in 3 layers of connective tissue = meninges • layers may have a space between them filled with cerebrospinal fluid which protects (shock absorber) and exchanges nutrients and waste Brain • About 100 billion neurons, mainly interneurons • Major parts of the brain: • • • • • Cerebrum Cerebellum Brain stem Thalamus Hypothalamus Figure 35-9 The Brain Section 35-3 Cerebrum Thalamus Pineal gland Hypothalamus Cerebellum Pituitary gland Pons Medulla oblongata Spinal cord