Life Science Mr. Galloway Chapters 20 Human Biology & Health Nervous System Recommended Websites: www.soulcare.org www.icr.org www.AnswersInGenesis.org
Three Functions of Nervous System • Receive Information • Sensing stimuli • Respond to Information • Reacting to a stimuli • Maintaining Homeostasis • Directing the body to keep in balance
Major Structures of the Nervous System
Key Terms: Nervous System • Nerve (Neuron) = a bundle of nerve fibers, that carries information (impulse) through the nervous system. • Axon = carries impulses away from the cell body. • Dendrite = carries impulses toward the cell body • Synapse = tiny space between each axon tip and the next structure. • Neurochemicals carry the impulse across the synapse.
More Terms: Nervous System • Stimulus = any change or signal in the environment that can make an organism react. • Response = what you body does in reaction to a stimulus. • Three Types of Neurons: • Sensory = picks up stimuli inside or outside body • Interneurons = carries impulses nerve to nerve • Motorneurons = sends impulses to a muscle
Central Nervous System:Control Center of the Body • Brain = Controls most of the body’s functions • Concussion = bruiselike injury of the brain. • Using a helmet on skateboards and bikes is important. • Spinal Cord = thick column of nerve tissue linking the brain to the peripheral nerve system.
The Brain • 100 billion neurons (all interneurons) • Each receives from up to 10,000 other neurons • Each sends to about 1,000 more neurons • Cerebrum = interprets input from senses and controls skeletal muscles, thinking, etc. • Cerebellum = coordinates muscles and balance • Brainstem = controls involuntary actions • Automatic actions like breathing, heart beat, etc.
Peripheral Nervous System • A network of nerves branching out from the central nervous system and connecting it to the rest of the body. • It is subdivided into two branches: • Somatic = controls the voluntary actions using your skeletal muscles (like tying your shoes). • Autonomic = controls the involuntary actions using your smooth muscles (stomach, blood vessels).
Reflex = Automatic response that occurs very rapidly and without conscious control.
Your Six Senses • Vision: cells convert light stimulus to a nerve signal • Hearing: cells converts sound waves to nerve signal • Smell: cells in nose convert chemical stimuli • Taste: cells on tongue convert chemical stimuli • Touch: cells on skin convert mechanical pressure to nerve signals (impulses). • Balance: Inner ear’s semicircular canals indirectly convert the effect of gravity to nerve signals for balance
Vision • Eyes convert light into nerve impulses • Eye Structure: • Cornea – clear tissue covering the front of the eye • Pupil – the opening through which the light enters • Iris – colored area around the pupil which opens or closes • Lens – flexible structure that focuses the light (bends rays) • Retina – layer of receptor cells at back of the eye (130 million) (Rod cells see black/white) (Cones see color)
Vision Problems • Nearsightedness • Able to see near objects clearly, not distant objects • Eyeball is too long, so focal point is before retina. • Corrected by a concave lens • Farsightedness • Able to see far off objects clearly, not near objects. • Eyeball is too short, so focal point is beyond retina. • Corrected by a convex lens
Optical Illusions • Simply seeing is not perceiving • Perception involves the brain • Sensory information is processed • The information must be interpreted • It is not always interpreted accurately