Nervous System

Young Woman or Old? That depends on your interpretation. Young people tend to see a young girl; older people, an elderly lady. With effort, you can switch from one to the other: the young woman's chin becomes the old woman's nose; the old woman's mouth, a band on the neck of the young woman.

Words and Colors Read the image aloud--but rather than reading the words, say the color of the ink that was used to write each word. It's not easy; the written words have a suprisingly strong influence over the actual color.

Faces or Vases? The answer depends on what you perceive as the background--the black spaces or the white. Photographer Zeke Berman has created this intriguing collage using silhouettes of real people. "Goblet Portraits" by Zeke Berman ©1978

Do you see the Phantom Spots? You may see spots where the white lines intersect, but if you try looking right at one, it will disappear. The spots, of course, aren't really there. They're caused by the way your eyes respond to light and dark areas. When an area is surround by light, your eye compensates by "turning down" the brightness a bit, making you see darkened blobs. In this grid, the areas surrounded by the most white are at the intersections of the white lines. Since this phenomenon works best in your peripheral vision, the spots disappear when you look right at them.

VISUAL ACUITY: A person who has sufficient visual acuity should see the number twelve in the circle on the left whether or not they have normal color vision.

COLOR BLINDNESS: A person with normal color vision sees a number seven in the circle on the left. Those who are color blind usually do not see any number at all.

RED-GREEN COLORBLINDNESS People with red-green color blindness see either a three or nothing at all. Those with normal color vision see an 8.

PROTANOPIA & DEUTERANOPIA Those with normal vision see the number thirty-five in the circle above. A person with protanopia sees only he number five. A person with deuteranopia sees the number three. People who are partially color blind will see both numbers but one more distinctly than the other.

Test for Macular Problems: Amsler Grid Make sure your room lights are on. Put on your reading glasses if you wear them, and test each eye separately (cover one eye at a time). Concentrate on the center spot . If the lines appear wavy, or if their are spots or holes in the grid, then you may have a macular problem

Complimentary Colors: Study complimentary colors using the ExploreSciences shockwave experiment. With one eye covered, stare at the center of the diagram below with the other eye for 30 seconds. Then click on the flag and see what you see with the same eye (keep the other one covered.)

Complimentary Colors

Nervous systems Nerves~ bundles of neurons wrapped in connective tissue Central nervous system (CNS)~ brain and spinal cord Peripheral nervous system (PNS)~ sensory and motor neurons

Structural Unit of Nervous System Neuron~ structural and functional unit Cell body~ nucelus and organelles Dendrites~ impulses from tips to neuron Axons~ impulses toward tips Myelin sheath~ supporting, insulating layer Schwann cells~PNS support cells Synaptic terminals~ neurotransmitter releaser Synapse~ neuron junction

Simple Nerve Circuit Sensory neuron: convey information to spinal cord Interneurons: information integration Motor neurons: convey signals to effector cell (muscle or gland) Reflex: simple response; sensory to motor neurons Ganglion (ganglia): cluster of nerve cell bodies in the PNS Supporting cells/glia: nonconductiong cell that provides support, insulation, and protection

Reflex Action A sense neuron is stimulated The cell body sends a signal to the axon and then to an interneuron The signal then goes to the brain 4. The brain sends a signal to the motor neuron 5. The motor neuron causes the muscle to contract

Sensory neurons, interneurons, and motor neurons The pathways of impulses from dendrite to cell body to axon of sensory neurons, interneurons, and motor neurons link the chains of events that occur in a reflex action. Similar paths of neural connections lead to the brain, where the sensations become conscious and conscious actions are initiated in response to external stimuli. Students might also trace the path of the neural connections as the sensation becomes conscious and a response to the external stimulus is initiated. Students should also be able to identify gray and white matter in the central nervous system.

Neural signaling, I Membrane potential (voltage differences across the plasma membrane) Intracellular/extracellular ionic concentration difference K+ diffuses out (Na+ in); large anions cannot follow….selective permeability of the plasma membrane Net negative charge of about -70mV

Transmission of Nerve Impulses Transmission of nerve impulses involves an electrochemical “action potential” generated by gated ion channels in the membrane that make use of the countervailing gradients of sodium and potassium ions across the membrane. Potassium ion concentration is high inside cells and low outside; sodium ion concentration is the opposite.

Nerve Impulses continued The sodium and potassium ion concentration gradients are restored by an active transport system, a pump that exchanges sodium and potassium ions across the membrane and uses ATP hydrolysis as a source of free energy. The re-lease of neurotransmitter chemicals from the axon terminal at the synapse may initiate an action potential in an adjacent neuron, propagating the impulse to a new cell.

Multiple Sclerosis Is a disease of the nervous system It is caused by hardening of the myelin sheath of the axons Due to the hardening of the axons the nerve impulse travels slower Symptoms include weakness, loss of coordination, problems with vision and speech

Neural signaling, IV “Travel” of the action potential is self-propagating Regeneration of “new” action potentials only after refractory period Forward direction only Action potential speed: 1-Axon diameter (larger = faster; 100m/sec) 2-Nodes of Ranvier (concentration of ion channels); saltatory conduction; 150m/sec

Synaptic communication Presynaptic cell: transmitting cell Postsynaptic cell: receiving cell Synaptic cleft: separation gap Synaptic vesicles: neurotransmitter releasers Ca+ influx: caused by action potential; vesicles fuse with presynaptic membrane and release…. Neurotransmitter

The cellular and molecular basis of muscle contraction Controlled by calcium ions and powered by hydrolysis of ATP, actin and myosin filaments in a sarcomere generate movement in muscles. Striated muscle fibers reflect the filamentous makeup and contraction state evidenced by the banding patterns of those fibers. A sketch of the sarcomere can be used to indicate the functions of the actin and myosin filaments and the role of calcium ions and ATP in muscle contraction.

Neurotransmitters Acetylcholine (most common) •skeletal muscle Biogenic amines (derived from amino acids) •norepinephrine •dopamine •serotonin Amino acids Neuropeptides (short chains of amino acids) •endorphin

Vertebrate PNS Cranial nerves (brain origin) Spinal nerves (spine origin) Sensory division Motor division •somatic system voluntary, conscious control •autonomic system √parasympathetic conservation of energy √sympathetic increase energy consumption

The Vertebrate Brain Forebrain •cerebrum~memory, learning, emotion •cerebral cortex~sensory and motor nerve cell bodies •corpus callosum~connects left and right hemispheres •thalamus; hypothalamus Midbrain •inferior (auditory) and superior (visual) colliculi Hindbrain •cerebellum~coordination of movement •medulla oblongata/ pons~autonomic, homeostatic functions