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 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 VocabThalamus: 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

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

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 Vocabtaste 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