Chapter 31 The Nervous System By: Aubrey Fischer Jenny Czech

31.1 The Function of the Nervous System: Send and receive messages within the body Respond to stimuli Neuron- basic unit of structure and function of the nervous system

31.1 peripheral nervous system: network of nerves and supporting cells that carries signals into and out of the central nervous system central nervous system: includes the brain and spinal cord; processes information and creates a response that is delivered to the body cell body: largest part of a typical neuron, contains the nucleus and much of the cytoplasm Dendrite: extension of the cell body of a neuron that carries impulses from the environment or from other neurons toward the cell body Axon: long fiber that carries impulses away from the cell body of a neuron myelin sheath: insulating membrane surrounding the axon in some neurons resting potential: electrical charge across the cell membrane of a resting neuron

31.1 action potential: reversal of charges across the cell membrane of a neuron; also called a nerve impulse Threshold: minimum level of a stimulus that is required to cause an impulse Synapse: point at which a neuron can transfer an impulse to another cell Neurotransmitter: chemical used by a neuron to transmit an impulse across a synapse to another cell

31.1 Types of Neurons: Sensory Neurons: Impulse from sense organ to spinal cord/brain Motor Neurons: Impulse from brain/spinal cord to muscles and glands Interneurons: Connect sensory and motor neurons

31.1 Messages are electrical and chemical signals Nerve Transmission: Messages are electrical and chemical signals An electric charge is conducted down a neuron (Dendrite to axon) Axon is covered in an insulating layer called a myelin sheath to speed up impulses As it reaches the end of the axon, chemicals (neurotransmitters) are released across the synapse (gap between neurons) to the next neuron The message continues neuron to neuron

31.2 Vocab Reflex: quick, automatic response to a stimulus Cerebrum: part of the brain responsible for voluntary activities of the body; the “thinking” region of the brain cerebral cortex: outer layer of the cerebrum of a mammal’s brain; center of thinking and other complex behaviors

31.2 Vocab Thalamus: brain structure that receives messages from the sense organs and relays the information to the proper region of the cerebrum for further processing Hypothalamus: structure of the brain that acts as a control center for recognition and analysis of hunger, thirst, fatigue, anger, and body temperature Cerebellum: part of the brain that coordinates movement and controls balance brain stem: structure that connects the brain and spinal cord; includes the medulla oblongata and the pons Dopamine: neurotransmitter that is associated with the brain’s pleasure and reward centers

31.2 Central Nervous System Brain- control center; transmits and receives messages Cerebrum Cerebellum Brain Stem (midbrain, pons, medulla oblongata.) Spinal Cord- connects brain with rest of the nervous system

31.2 Dopamine – neurotransmitter released with pleasurable activities Addiction and the Brain: Dopamine – neurotransmitter released with pleasurable activities Addictive drugs cause large release of dopamine (resulting in “high”) Brain reacts by reducing number of receptors for dopamine  normal activities no longer produce the pleasure they once did

31.3 Vocab somatic nervous system: part of the peripheral nervous system that carries signals to and from skeletal muscles reflex arc: the sensory receptor, sensory neuron, motor neuron, and affecter that are involved in a quick response to a stimulus autonomic nervous system: part of the peripheral nervous system that regulates activities that are involuntary, or not under conscious control; made up of the sympathetic and parasympathetic subdivisions

31.3 Link between the central nervous system and the rest of the body Peripheral Nervous System: Link between the central nervous system and the rest of the body Network of nerves throughout the body *Made of many neurons

31.3 Sensory Division: Transmits impulses from sense organs to central nervous system Uses sensory receptors Chemoreceptors Photoreceptors Mechanoreceptors Thermoreceptors Pain receptors

31.3 Motor Division: Transmits impulses from central nervous system to muscles or glands Somatic nervous system: regulates activities under conscious controlAutonomic nervous system: regulates activities that are automatic or involuntary Autonomic nervous system: regulates activities that are automatic or involuntary

31.4 Vocab taste bud: sense organs that detect taste Cochlea: fluid-filled part of inner ear; contains nerve cells that detect sound semicircular canal: one of three structures in the inner ear that monitor the position of the body in relation to gravity Cornea: tough transparent layer of the eye through which light enters Iris: colored part of the eye

31.4 Vocab Pupil: small opening in the iris that admits light into the eye Lens: structure in the eye that focuses light rays on the retina Retina: innermost layer of the eye; contains photoreceptors Rod: photoreceptor in the eyes that is sensitive to light but can’t distinguish color Cone: in the eye, a photoreceptor that responds to light of different colors producing color vision

31.4 Senses: Vision- eyes Hearing and Balance- ears Smell and taste- nose and mouth Touch- skin

31.4 Hearing/balance Mechanoreceptor Smell Chemoreceptor Taste Touch Mechanoreceptor Pain receptor Thermoreceptor Vision Photoreceptor