Chapter 23 Notes - Dr. Meshagae Hunte-Brown PDF

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Dr. Meshagae Hunte-Brown...

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Chapter 23- Nervous and Motor Systems 23.1-23.3: What is the nervous system? 23.1- Why do we need a nervous system? Nervous System= Lets us see, hear, feel, taste, smell, remember, think, act, and react. A network of cells that collects information about an organism’s internal and external environments, processes that information, and sends signals to effectors, which are muscles and glands that are capable of responding to the information. 3 Critical Features of Nervous Systems: 1. Receives input (stimuli) from the surrounding world 2. Processes that information 3. Initiates responses to the internal and external environments, when necessary 23.2- Neurons are the building blocks of all nervous systems. Neuron= A type of cell that is specialized for generating and conducting electrical impulses and is found in all animals, with the exception of sponges. 3 Types of Neurons: 1. Sensory Neurons  Collect information from an animal’s environment 2. Motor Neurons  Stimulate action by conveying signals to muscles or glands 3. Interneurons  Integrate the signals coming in from the sensory neurons and relay them to the motor neurons. Nerves= Groups of neurons bundled together with connective tissue. Connect us to our world by enabling us to sense light, sound, touch, tastes, and smells and to respond to all of that sensory information. Cell Body= Contains a nucleus, mitochondria, endoplasmic reticulum, and other cellular machinery. Dendrite= The part of a neuron that is like an antenna. It senses and responds to stimulation from outside the cell and sends that information toward the cell body of the neuron. Numerous ones branch out from the neuron cell body. Axon= Transmits a signal, much like an electrical wire does over great distances. Long tube-like extension of the main cell body that transmits the signals picked up by the dendrites to the rest of the organism’s body.

Glial Cells= Non-neuronal cells, which function like a support staff to protect, insulate, and nourish the neurons. 23.3- The vertebrate nervous system consists of the peripheral and central nervous systems. Peripheral Nervous System (PNS)= The network of: 1. Sensory cells modified to receive information from the environment 2. Motor pathways that transmit signals to effectors, the muscles and glands that are capable of responding to that stimulus. Central Nervous System (CNS)= Made up of the spinal cord and brain. Not directly connected to sensory organs or to muscles, the central nervous system processes information that it receives from sensory cells about the organism’s surroundings and sends out instructions to other nervous tissue to act in response to that sensory information. Somatic Nervous System= Relays signals to your skeletal muscles and enables you to contract those muscles and move your limbs consciously, such as when you pick up a fork. Autonomic Nervous System= Relays signals to your glands and your smooth muscle tissue and cardiac muscle. These signals, which are not under conscious control, cause the muscles surrounding your stomach and intestine, for example, to contract and to move food through the digestive tract. Reflex= Direct sensory-motor response that causes reaction to a sensation that does not need to be processed through the brain. Sympathetic Nervous System= Responsible for coordinating the body’s fight-orflight response to stress, including increasing the heart and breathing rates and providing muscles with additional blood flow. Parasympathetic Nervous System= Responsible for controlling activities related to digesting food and eliminating waste, tending to slow the heart and breathing rates as these processes occur. 23.4-23.7: How do neurons work? 23.4- Dendrites receive external stimuli. Resting Potential= The cell is described as “polarized” and can be thought of as “ready to fire.” Action Potential= An electrical signal that travels down its axon. 23.5- The action potential propagates a signal down the axon.

Terminal Buttons= Knob-like ends of the axon, positioned very close to a muscle cell or gland or to the dendrites of another neuron. Myelin Sheath= Axons are insulated by a fatty coating, preventing the action potential from weakening as it travels down the axon. 23.6- At the synapse, neurons interact with other cells. Synapse= The point where these cells meet. 1. Sacs called vesicles release neurotransmitters into the synaptic cleft.  Vesicles= Little sacs  Presynaptic Membrane= Axon’s cell membrane  Neurotransmitters= Chemical messengers  Synaptic Cleft= The space between the axon and the cell receiving the signal (muscle, gland, or neuron) 2. Neurotransmitter diffuses and binds to nearby receptor sites.  Postsynaptic Membrane= Neurotransmitter molecules attach to receptor sites on the adjacent cell. 3. Gates open in the postsynaptic cell membrane, and the signal enters the postsynaptic cell. 4. Neurotransmitter is released from the postsynaptic cell receptors and recycled or broken down. 23.7- There are many types of neurotransmitters. Acetylcholine= The neurotransmitter released by motor neurons at the point where they synapse with muscle cells. Glutamate= Appears to be involved with learning and memory. Dopamine= Important in initiating and coordinating movement. Serotonin= Generally functions as an inhibitory neurotransmitter. 23.8-23.14: Our senses detect and transmit stimuli. 23.8- Sensory receptors are our windows to the world around us. 5 senses: 1. 2. 3. 4. 5.

Hearing Touch Taste Smell Sight

23.9- Taste: an action potential serves up a taste sensation to the brain. Chemoreceptors= Within each taste bud are 60-80 sensory receptor cells, which are modified epithelial cells that synapse with sensory neurons, that are stimulated when particular chemicals in food dissolve in saliva and bind to proteins on the receptor cell surface. 23.10- Smell: receptors in the nose detect airborne chemicals. Neurons that can detect smell have dendrites modified with tiny, hair-like projections covered with chemoreceptors, densely packed within the nasal cavity. 23.11- Vision: seeing is the perception of light by the brain. Single-Lens Eyes= Evolved independently twice: in vertebrates and in a group of mollusks that includes the squid. Iris= Light hits the eye and enters the eye’s interior through this. Retina= Once the light is through the pupil, a lens focuses it onto this nervous tissue containing light-sensitive cells (Photoreceptor Cells). Photoreceptor Cells= Light-sensitive cells Optic Nerve= Transmits impulses to the vision center of the brain Rods= Photosensitive cells in the retina, which are highly sensitive to even tiny amounts of light and make it possible to see at night and in low-light. Cones= Less sensitive to light and so are more effective during daylight. Color-Blind= The result of mutant genes, some individuals (usually men) produce non-functioning red or green cones. Eye Cups= Simplest form found in the flatworms, such as planaria, which live in ponds and streams. Compound Eyes= Made of dozens to thousands of separate light-sensing units, each with its own image-forming lens that directs light onto about a dozen photoreceptors. 23.12- Hearing: sound waves are collected by the ears and stimulate auditory neurons. Mechanoreceptors= Specialized neurons with receptors that respond to mechanical pressure. Hearing:

1. Sound waves are funneled down the ear canal.  Ear Canal= A channel that conducts sound waves. 2. Sound waves cause the eardrum to vibrate.  Eardrum= A thin membrane that divides the outer ear from the middle portion of the ear. 3. Vibrations pass to the inner ear membrane. 4. Fluid in the inner ear conducts the vibrations, bending hair-shaped receptor cells and releasing neurotransmitters. 5. The neurotransmitters cause auditory neurons to fire an action potential. 6. The signal is passed to the brain, where it is interpreted as sound. 23.13- Touch: the brain perceives pressure, temperature, and pain. Mechanoreceptor= Sensitive to pressure Thermoreceptor= Sensitive to temperature Pain Receptor= Sensitive to pain 23.14- Other senses help animals negotiate the world.    

Balance and Motion Electricity Magnetism Heat

23.15-23.16: The muscular and skeletal systems enable movement. 23.15- Muscles generate force through contraction. 1. Skeletal Muscle= Responsible for generating most of the movement in vertebrates. 2. Cardiac Muscle= Causes the heart to pump blood through the body. 3. Smooth Muscle= Not under conscious control, surrounds blood vessels and many internal organs. Muscle Fiber Contraction: 1. Detach 2. Reach 3. Reattach 4. Pull Back Myofibrils= Cylindrical organelles that shorten when they contract. Sarcomeres= Repeating units in the myofibril where the contraction takes place. Actin= Thin filaments are made mostly from this protein.

Myosin= Thick filaments are made mostly from this protein. Twitch= The duration between a contraction and a relaxation when a muscle contracts. 23.16- Skeletal systems enable movement, among several other important functions. 3 types of Skeletal Systems: 1. Hydrostatic Skeleton= Pressure created within a fluid-filled cavity creates sufficient rigidity that the muscles surrounding it can generate movement, including in earthworms, the ability to dig. Ex. Jellyfish, squid 2. Exoskeleton= A rigid outer covering that supports and protects an animal’s body. Ex. Turtle, insects, crabs, lobsters, spiders 3. Endoskeleton= A support structure of hard mineralized tissue, as is found in echinoderms (sea stars and sand dollars) and in all vertebrates, including humans. Functions of the Skeletal System: 1. Structural support 2. Protection 3. Enabling movement 4. Cell production 5. Mineral reservoir Vertebrate Skeleton Structure:  Axial Skeleton= Includes the skull, sternum, ribs, and vertebrae  Appendicular Skeleton= Includes the limbs, the pelvic girdle, and the pectoral girdles (of the shoulder region) 23.17-23.18: The brain is organized into distinct structures dedicated to specific functions. 23.17- The brain is organized into several distinct regions. Hindbrain= The top of the spinal cord is the beginning of the brain. 1. Medulla= Pathway for motor and sensory neuron signals; regulates basic physiological functions such as respiration, heart rate, and digestion. 2. Pons= Pathway for motor and sensory neuron signals. 3. Cerebellum= Coordinates motor activity. Midbrain= Filters and evaluates motor and sensory neuron signals. Forebrain= Largest region of the brain

1. Cerebral Cortex= Involved in abstract thought, problem solving, and language. a. Frontal Lobe= Regulates speech production, motor control, smell, problem solving, and many aspects of personality. b. Temporal Lobe= Perceives and processes auditory and visual sensations; important in pattern recognition and language comprehension. c. Parietal Lobe= Receives and perceives touch and pressure sensations; important in sensory integration. d. Occipital Lobe= Receives and processes visual information. 2. Thalamus= Receives sensory input and relays some signals to the cerebral cortex while blocking others. 3. Hypothalamus= Regulates many fundamental drives, including hunger and thirst, sexual activity, and maintenance of body temperature; controls the hormone secretions of tiny pituitary gland. 4. Limbic System= A set of structures near the center of the brain together make this up. a. Hippocampus and Amygdala= Responsible for many of our physiological drives and instincts. Together, these structures play an important role in emotions, learning, and memory. Corpus Callosum= Thick and broad band of neurons that connects the divided left and right hemisphere of the brain. Left Hemisphere= The site of areas specializing in language, logic, and mathematical skills. Right Hemisphere= Dedicated to emotions, intuitive thinking, and artistic expression. 23.18- Specific brain areas are involved in the processes of learning, language, and memory. Language= Simply the means of communication between individuals of any species. Wernicke’s Area= Located in the left temporal lobe. Required for the understanding of speech, including the linking of words with meaning. Broca’s Area= Controls the muscles involved in the actual process of speaking. It is located in the front part of the left frontal lobe. Long-Term Depression and Long-Term Potentiation= Neurotransmitters are repeatedly released by the presynaptic membrane, the adjacent neuron responds by

initiating an action potential, but also by becoming less likely or more likely to respond to future stimulation with an action potential. Functional MRI (FMRI)= Can visualize the size of activity of different brain structures. 23.19-23.21: Drugs can hijack pleasure pathways. 23.19- Our nervous system can be tricked by chemicals.  

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Cocaine Prozac and Zoloft o Selective Serotonin Reuptake Inhibitors (SSRIs)= Block serotonin from being reabsorbed and recycled by the presynaptic cells that released it, prolonging its effect. Morphine and Heroin Nicotine

23.20- A brain slows down when it needs sleep. Caffeine wakes it up. Caffeine binds to the adenosine receptors, and blocks the fatigue-inducing message of adenosine. 23.21- Alcohol interferes with many different neurotransmitters. Alcohol affects the functioning of multiple neurotransmitters including glutamate, endorphins, dopamine, and serotonin, slowing reaction times, slurring speech, blocking pain, and increasing contentment....