Unit 10Chapter 36

The Nervous System

The Nervous System

Neurons Nerves cells, the basic unit of structure &

function of the nervous system

The Nervous System

Neuron structure:Dendrites

Branchlike extensions that receive impulses & carry them toward the cell body

Cell body Location of the nucleus & much of the

cytoplasmAxons

Extensions carrying the impulse away from the cell body

The Nervous System Categories of neurons: Sensory neurons carry impulses from the body

to the spinal cord & brain Motor neurons carry impulses from the spinal

cord & brain to the body Interneurons are found within the spinal cord &

brain, pass response impulses between sensory & motor

The Nervous System Transmitting an Impulse: Each impulse consists of an electrical charge

that travels the length of a neuron’s cell membrane to a gap, called a synapse

The impulse is caused by the depolarization of chemicals surrounding the cell membrane

Chemicals called nuerotransmitters, are released into the synapse, which stimulates a charge in the next neuron

Transmitting an impulse along the axon

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Transferring signals across the synapse to an adjoining neuron

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The Nervous SystemDivision of the Nervous System:Central Nervous

System (CNS) Consists of the

brain and spinal cord

Peripheral Nervous System (PNS) Consists of the nerves

that carry messages to & from the CNS

The Central Nervous System

Anatomy of the Brain:Cerebrum

Largest lobe, controlling voluntary movement, intelligence, memory, & the senses

Cerebellum Located at the back,

controlling balance, posture, and coordination

Medulla oblongata Located within the brain stem,

controlling involuntary (vital) activities

Cerebrum

Cerebellum

Medulla

The Peripheral Nervous System Somatic Nervous System

(SNS) Made up of cranial & spinal

nerves, relaying voluntary information between the CNS and the skin & muscles

Autonomic Nervous System (ANS) Made up of the sympathetic

& parasympathetic systems, relaying involuntary responses, not under conscious control

The Peripheral Nervous SystemReflexes

An automatic, unconscious response for protecting the body

This response travels to the spinal cord where it responds directly back to a muscle

The SensesSensing Chemicals:Odor chemicals stimulate nerve endings in

the nasal passages, which transmit through the olfactory nerve to the cerebrum

Chemical dissolved in saliva stimulate nerve endings in the taste buds of your tongue, detecting only sweet, sour, bitter & salty

The SensesSensing light:The eye’s retina contains nerve enedings

called rods & cones, which transmit impulses through the optic nerve to the cerebellum

Rods and Cones

The eye

The SensesSensing vibrations (sound)Sounds waves vibrates

the eardrum, the three small bones—hammer, anvil, & stirrup—then the nerve endings in the cochlea, which transmit impulses through the auditory nerve to the cerebrum

The ear

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The SensesSense of Balance:Within the inner ear are three

semicircular canals, which contain fluid & nerve endings that transmit impulses to the cerebellum

The SensesSense of Touch:Nerve endings in the dermis of your skin

respond to temperature, pressure and pain, transmitting impulses through sensory neurons to the CNS