The Nervous System Nervous System

Function of the Nervous System React to outside Stimuli Controls activities of the body’s vital organs

Central Nervous System (CNS) Brain- 3 main regions Spinal Cord-link between the brain and the peripheral nervous system

Central Nervous System Cerebrum- movement, senses, speech, abstract thought Cerebellum- Maintain balance Brainstem-link between brain and the peripheral nervous system

Peripheral Nervous System (PNS) Nerves that carry impulses from the body to the brain and spine (senses) Connects the rest of the body

Neurons (nerve cells) Basic unit of function for the nervous system; quickly transmits messages

Four parts of a Neuron Dendrites- receive impulses and conducts them towards the cell body. Axon- carry impulses away from the cell body towards another nerve or muscle cell. Cell body-connects dendrite to axon, location of the cell nucleus. Axon terminal- releases neurotransmitters into the synapse

Sensory Neurons Carry impulses from body to spine and brain. (From shoulder – someone is tapping me)

Interneurons Found in the spine and brain. Process impulse and pass response to motor neurons. (within brain- decides what to do- we need to turn around and see)

Motor Neurons Activate muscles and movement (from brain- contract neck muscles, turn around and see who it is)

Nerve Impulse Nerve impulses depends on the movement of positively charged ions across the cell membrane

Resting Neuron (Polarized) Sodium more abundant and located on the outside of the cell. Na+/K+ pumps move ions across the membrane to create charges creating impulses.

Stimulated Neuron (Depolarized) Sodium channels open up and sodium ions pass into the neuron making the inside positively charged . This stimulates the neuron creating a wave of energy down the axon. Once the wave of energy passes, it returns to its resting state.

Stimulated Neuron (Depolarized back to Polarized) The reversal in charge moves down the neuron like a wave. This impulse is called action potential. As the wave passes, the membrane returns to its polarized state. Slight delay before it can transmit another impulse Polarized Depolarized Return to

Neurons do not physically touch their target cells Chemicals called neurotransmitters cross a gap called the synaptic cleft or synapse. Neurotransmitters are chemicals that stimulate the next nerve cell in line (EX: serotonin, dopamine) After they have “done their job”, they are broken down by enzymes or reabsorbed

Cerebrum Cerebellum Brian stem (Medulla oblongata

Brian stem Changes is heart rate Breathing, blood pressure, vomiting, swallowing Digestion

Cerebrum Intelligence, learning, judgment Speech and memory Sense of hearing, vision, taste and smell Skeletal muscle movement

Cerebellum Balance and coordination Posture