NERVOUS SYSTEM Science, Technology, & Society MR. CANOVA Period 11

Neurons and Nerve Impulses Neuron- Nerve cells that transmit information throughout the body Dendrites- ”Antennae” that receive information from other cells Axon- Extension of cytoplasm that conducts nerve impulses Myelin sheath- Layer of insulation Nodes of Ranvier- Gaps between myelin sheath

Neuron Function Membrane potential- The difference in electrical charge across the cell membrane. Expressed in voltage. Resting potential- The membrane potential of a neuron at rest -70 millivolts (mV) Inside of cell is negatively charged, outside of cell is positively charged K+ ions in the cell, Na+ out of the cell Action potential- A nerve impulse Approaches +40 millivolts (mV) Inside of cell is positively charged, outside of cell is negatively charged Na+ ions in the cell, K+ out of the cell

Communication between Neurons Synapse: The junction where a neuron meets another cell Pre/Post synaptic cell Neurotransmitters: Signal molecules that bind to receptor proteins on the postsynaptic cleft and interact wit the postsynaptic cell Can excite or inhibit the activity of a cell it binds to Membrane potential: + ions enter neuron, an action potential is produced (excitation) - ions enter neuron, an action potential is suppressed (inhibition)

Central Nervous System Consists of the brain and the spinal cord. Interprets and responds to information from the environment and from within the body. BRAIN- The body’s main processing center. Contains about 100 billion neurons. Cerebrum- The largest part of the brain Cerebellum- At the base of the brain, regulates balance, posture, and movement. Brain stem- At the base of the brain, a collection of structures leading to the spinal cord. Upper- Thalamus and Hypothalamus Lower- Midbrain, Pons, and Medulla oblongata SPINAL CORD- A dense cable of nervous tissue that runs through the vertebral column.

THE BRAIN

SPINAL CORD

Peripheral Nervous System Consists of 31 spinal nerves and 12 cranial nerves. Connects the brain and the spinal cord to the rest of the body 2 Divisions: Sensory and Motor Sensory-Directs sensory information to the CNS Motor-Carries out responses to sensory information. 2 Principal Divisions: Somatic and Autonomic Nervous systems Somatic- Reflexes, some are involuntary Autonomic-Involuntary responses 2 Divisions: Sympathetic and Parasympathetic Sympathetic- Under stress (Fight or Flight responses) Parasympathetic- Normal conditions When body is at rest (ie-sleep)

SENSORY RECEPTORS Receptor type StimuliLocations ThermoreceptorsTemperature changeSkin, Hypothalamus Pain receptorsTissue damageTissues and Organs MechanoreceptorsMovement, Pressure, Tension Skin, Ears, Muscles PhotoreceptorsLightEyes ChemoreceptorsChemicalTongue, Nose

Processing of Sensory Information 4 main lobes- Frontal Motor function Intellectual function Speech Smell Occipital Vision Parietal Sensory Taste Temporal Hearing

THE EYE Pupil-Allows light to enter the eye Lens-Disk that focuses light onto retina Retina-Lining on back of the eye that converts light energy into electrical signals Cornea-Transparent covering on eye Iris-Controls amount of light that enters the eye Rods-Respond to dim light Cones-Respond to bright light and allow color vision Optic nerve-Exits back of the eye and runs along base of the brain to the thalamus

THE EAR Eardrum-Vibrates when sound waves enter Middle ear-Consists of 3 small bones; hammer, anvil, and stirrup Cochlea-Fluid-filled chamber that contain hair cells that generate nerve impulses. Auditory nerve-Sends impulses to the brain Semicircular canals-Fluid-filled chambers in the inner ear that maintain equilibrium Located above cochlea

CHEMICAL SENSES CHEMORECEPTORS- LOCATED ON THE TONGUE 4 CHEMICAL SUBSTANCES OLFACTORY RECEPTORS- LOCATED IN THE NASAL PASSAGE Sense of smell

Drugs and the Nervous System Drug ExamplesPsychoactive effects DepressantsAlcohol, SedativesDecreased CNS activity StimulantsCocaine, Crack, NicotineIncreased CNS activity InhalantsPaint thinner, GlueDisorientation, Confusion HallucinogensLSD, PCP, MDMAAnxiety, Hallucinations THCMarijuana, hashishShort-term memory loss NarcoticsHeroin, Morphine, Codeine, Opium Sedation

Drug Addiction and Neuron Function Addiction- Physiological response caused by use of a drug that alters the normal functioning of neurons and synapses. Tolerance- Increasing amounts of the drug are needed to achieve the desired sensation. Withdrawal- Emotional and physical symptoms caused by removal of the drug from the body. Depressant- Drug that decreases the activity of the CNS Stimulant- Drug that increases the activity of the CNS