The Nervous System Neurons Nerves the Brain and

The Nervous System Neurons, Nerves, the Brain and Neurotransmitters

Organization of the nervous system

The central nervous system = The Brain + Spinal Cord Spinal cord: A collection of neurons and supportive tissue running from the base of the brain down the center of the back –Protected by spinal column But the central nervous system is only one part…

Spinal Reflexes: Who Needs a Brain? • For example, pulling your hand away from something hot • No need to involve the brain • “Spinal reflexes” go right from the skin to the spinal cord back to the muscle • Neurons that serve the skin and muscles in arms and legs are part of the peripheral nervous system • So, spinal reflexes involve the central and peripheral nervous systems

Organization of the nervous system

Peripheral Nervous System • 43 pairs of nerves – Nerves are bundles of many, many neurons • 12 pairs go straight to the brain • 31 pairs go to the spinal cord (remember the spinal reflexes? )

Peripheral Nervous System • Autonomic (think “automatic”): controls heart, stomach, etc. • Somatic: Arms and legs – things you control voluntarily

Autonomic Nervous System • Sympathetic: Prepares the body for ACTION! • Parasympathetic: Rests the body and restores to get ready for next round.

Organization of the nervous system

A Neuron is a very special cell: You have about 100 billion of them! • Dendrites: Receive information from other neurons and transmit toward the cell body

A Neuron is a very special cell: You have about 100 billion of them! • Cell body: Keeps the neuron alive and determines whether it will fire • Axon: Extending fiber that conducts impulses away from the cell body and transmits to other cells.

Neurotransmitter Chemical released by a transmitting neuron at the synapse and capable of affecting the activity of a receiving neuron

Major neurotransmitters Serotonin – involved in treatment of depression Dopamine Acetylcholine (Ach) Norepinephrine Gamma aminobutyric acid (GABA) Glutamate Endorphins – “runner’s high”

The brain stem Pons: Involved in sleeping, waking, and dreaming

chapter 4 The brain stem Medulla: Responsible for certain automatic functions such as breathing and heart rate

chapter 4 The brain stem Reticular activating system: Arouses cortex and screens incoming information

The cerebral cortex: curly