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The Nervous and Skeletal System

The Nervous and Skeletal System. By Peter Van Kha Terry Stinson Nhi Dang. The Nervous System. The Eye and The Brain. The Eye. By Peter Van Kha. Photoreceptor Cells. Photoreceptor cells are neurons that are found in the eye’s retina.

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The Nervous and Skeletal System

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  1. The Nervous and Skeletal System By Peter Van Kha Terry Stinson Nhi Dang

  2. The Nervous System The Eye and The Brain

  3. The Eye By Peter Van Kha

  4. Photoreceptor Cells • Photoreceptor cells are neurons that are found in the eye’s retina. • They are used for phototransduction, in which light is converted into electrical signals. • When they absorb photons, their membrane potential change which allows them to send signals to other neurons. • All this is used by the visual system as information to help form images.

  5. Rod Cells • They are in the retina. • They function in less intense light • Because they are more light sensitive, they assist in night vision. • They can be found on the outer edges of the retina and are used in peripheral vision. • There are more then 100 million rod cells located in a human’s retina.

  6. Cone Cells • Cone Cells are found in the Retina. • They function in high intensive light. • They are concentrated in the foeva. • In a human’s retina, there are about 6 million cone cells. • Cone cells are less sensitive to light in comparison to Rod Cells. • They allow the perception of color and also give finer detail and the rapid changes in images, since their response time to stimuli is faster then rod cells.

  7. Nerve Cells • Nerve Cells can be found in the eyes. • They transmit information to the brain through electrical signals • They have excitable membranes that propagate electrical impulses.

  8. Ciliary Muscles • There are two sets of ciliary muscles in the eye; near the front of the eye, and above and below the lens. • Zinn, which is a connective tissue, connects the lens to the ciliary muscles. • They are in charge of shaping the lens to focus light on the retina.

  9. Ciliary Muscles (cont.) • When the muscles contract or relax, it changes the lens: • Contract: lens become more convex, which improves the focus for closer objects • Relax: flattens the lens, for focusing on further objects

  10. The Evolution of Eyes • Eyes evolved from a “proto-eye” about 540 million years ago • The earliest eyes were called “eyespots” • They were simple patches of photoreceptor cells • They first only sensed the brightness of things, and could not determine the direction the light was coming from • The “eyespot” then evolved into a “cup” shape, which then allowed us to see where the light is coming from

  11. The Evolution of Eyes (cont.) • The “cup” deepened over time and the number of photoreceptor cells increased. • Transparent Protective Cells developed to protect the eyes. • Soon we were able to see color and block harmful radiation. • The Transparent Protective Cells then evolved into two layers to help improve images • Transparent layers eventually evolved into the cornea and iris

  12. The Eye • Eyes are an organ of vision. • They allow the detection of light. • Eyes can be as simple as detecting light and dark to as complex as distinguishing shapes, colors, and filtering radiation.

  13. The Brain • By Terry Stinson aka DARKNESS

  14. The Function of the Brain • The brain controls all involuntary activities, such as: Heartbeat, respiration, and digestion. • The brain also controls reasoning, thought, and abstraction. • The human brain is thought to be the source of the conscious, or “cognitive mind.” • This means the brain is the source of perception, imagination, interpretation, and memories.

  15. The Brain (Cont.)

  16. The Brain (Cont.) • Frontal Lobe: Reasoning, planning, parts of speech, movement, emotions, and problem solving. • Parietal Lobe: Movement, Recognition, Orientation. • Temporal Lobe: Auditory, memory, and speech. • Occipital Lobe: Visual processing. • Cerebellum: Movement, posture, and balance.

  17. The Neuron (Cont.) • Neurons are nerve cells that transmit nerve signals to and from the brain. • The axon: Takes infromation away from the cell body. Bundles of axons are known as nerves or nerve tracts or pathways. • Myelin: Coats and insulates the axon. Myelin is manufactured by Schwann's cells, and consists of 70-80% lipids (fat) and 20-30% protein. • The cell body (soma): Contains the neuron's nucleus. • A typical neuron has about 1,000 to 10,000 synapses (that means it communicates with 1,000-10,000 other neurons, muscle cells, glands.) • Over 100 Billion in the brain!!!

  18. The Skeletal System

  19. Bones Nhi Dang

  20. Bones • Rigid connective tissues consisted of cells packed in a matrix • Make up the body’s framework • Bones Hierarchy: Bone cells -> bone tissues -> bones -> skeletal system

  21. Bone Tissues • Outer Bone (Cortical Bone): • Contains structures called osteons where Haversian canals allow blood vessels and nerves to pass through • Made up of compact tissues • Inner Bone (Trabecular Bone): • Contains cavities where red marrow tissue is located • Made up of spongy (cancellous) tissues • Hollow Core: • Contains yellow bone marrow and blood vessels

  22. Bone Cells • In the bone matrix: • Bone-lining cells • Osteoblasts • Osteocytes • Osteoclasts • In red bone marrow: • Stem cells (hematopoietic and mesenchymal) • Red blood cells • In yellow bone marrow: • Mainly fat cells

  23. Bone Matrix

  24. Bone-Lining Cells • Old osteoblasts • Coat the surface of the bone • Shape: flat and long • Regulate calcium level in bone

  25. Osteoblasts • Located where the bone marrow meets the matrix • Created when mesenchymal cells in bone marrow differentiate • Secrete osteoid, which later crystallizes and becomes new bone, and hormones to make bones flexible and durable

  26. Osteoclasts • Comes from haemopoietic cells in bone marrow • Formed from two or more cells and thus have two or more nuclei • Have ruffled edges and big surface areas to maximize their efficiency in dissolving and absorbing old bone • Found on surface of bone in between osteoblasts and next to dissolving bone

  27. Osteoblasts and Osteoclasts Working Together

  28. Osteocytes • Formed when osteoblasts are trapped in the bone matrix • Star-shaped, connect to one another using their branches called canaliculi, which are also used for the transportation of nutrients and waste • Maintain living bone by secreting enzymes and controlling minerals in bone • Senses pressure and cracks in the bone to direct the osteoclasts

  29. Bone Marrow

  30. Hematopoietic Cells • Produce white blood cells, red blood cells, and platelets • Give rise to osteoclasts

  31. Mesenchymal Cells • Lie between the bone marrow and the bone matrix • Differentiate into osteoblasts, chondrocytes (in cartilage), myocytes (in muscles) and many other types of cell. • Regulate substances in and out of bone marrow

  32. Skeletal System • Consisted of 206 bones connected together by tendons and ligaments • Functions: • Works with the muscular system to control movement • Support and balance • Protects organs

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