Neurons
Neurons are specialized nerve cells that helpyou gather information about your environment,interpret the information, and react to it.
33.1 Structure of the Nervous System
Nervous System
Neurons consist of three main regions: thedendrites, a cell body, and an axon.
Chapter 33
Dendrites pass signals they receive on to thecell body in electrical impulses.
Nervous System
The axon passes those impulses on to theother neurons or muscles.
33.1 Structure of the Nervous System
Chapter 33
There are three kinds of neurons: sensoryneurons, interneurons, and motor neurons.
Nervous System
Sensory neuronssend impulses fromreceptors in the skinand sense organs tothe brain and spinalcord.
Interneurons carry impulses to motor neurons.
33.1 Structure of the Nervous System
Chapter 33
Nervous System
33.1 Structure of the Nervous System
Motor neurons carry impulses away from thebrain and spinal cord to a gland or muscles,
resulting in a secretion
or movement.
The nerve impulsecompletes a reflexarc, or a nervepathway that
consists of a sensory neuron, an interneuron,
and a motor neuron.
Chapter 33
Nervous System
Chapter 33
A Nerve Impulse
Nervous System
Neurons at restdo not conductimpulses.
Sodium ions (Na+)collect on the outsideof the cell membrane.
33.1 Structure of the Nervous System
Chapter 33
Potassium ions (K+)collect on the inside ofthe cell membrane.
Nervous System
33.1 Structure of the Nervous System
Negatively chargedproteins activelytransport sodium ionsout of the cell and
potassium ions into the cell.
Chapter 33
An Action Potential
Nervous System
A nerve impulse is also known as an actionpotential.
The minimumstimulus to cause anaction potential to beproduced is called athreshold.
33.1 Structure of the Nervous System
Chapter 33
1. When a stimulus reachesthreshold, channels openin the plasma membrane.
Nervous System
2. Sodium ions are rapidlypumped through thesechannels causing atemporary change in theelectrical charges.
More positive charges arenow inside the membrane.
33.1 Structure of the Nervous System
Chapter 33
Impulse Transmission Steps
3.The now positive chargeinside the membranecauses other channels toopen and the potassiumis quickly pumped out ofthe cell.
Nervous System
4. The potassium restoresthe positive chargeoutside the cell.
33.1 Structure of the Nervous System
Chapter 33
This rapid positive tonegative to positivecharge reversal movesalong the axon like awave.
Nervous System
The movement can beseen by finding thesodium-potassiumreversal pattern in thethree diagrams.
33.1 Structure of the Nervous System
Chapter 33
Nervous System
Chapter 33
The small gap between the axon of oneneuron and the dendrite of another neuronis called a synapse.
Nervous System
An action potential is carried across thesegaps by neurotransmitters.
The Synapse
33.1 Structure of the Nervous System
Chapter 33
The nervous systemconsists of two majordivisions: the centralnervous system andthe peripheral nervoussystem.
33.2 Organization of the Nervous System
Nervous System
Chapter 33
The Central Nervous System Functions
Nervous System
The central nervous system (CNS) is madeup mostly of interneurons.
Coordinates all of the body’s activities
Relays messages, processes information,and analyzes responses
33.2 Organization of the Nervous System
Chapter 33
The Brain
Nervous System
The brain issometimes calledthe control centerof the entire body.
Divided into thecerebrum, thecerebellum, andthe brain stem.
33.2 Organization of the Nervous System
Chapter 33
The cerebrum is divided into two halvescalled the left and right hemispheres.
Nervous System
The functions of the brain include thoughtprocesses (learning), memory, language,speech, voluntary body movements, andsensory perception.
33.2 Organization of the Nervous System
Chapter 33
The cerebellum controls balance, posture,and coordination.
Nervous System
The skeletal muscles are controlled to makeyour motor skills coordinated and smooth.
33.2 Organization of the Nervous System
Chapter 33
The brain stem connects the brain andspinal cord and is composed of the medullaoblongata and the pons.
Nervous System
The medulla oblongata helps control breathingrate, heart rate, and blood pressure.
The pons also aids in breathing.
33.2 Organization of the Nervous System
Chapter 33
The hypothalamus, located between thebrain stem and the cerebrum, is essentialfor homeostasis.
Nervous System
The hypothalamus regulates bodytemperature, thirst, appetite, and waterbalance.
33.2 Organization of the Nervous System
Chapter 33
The Spinal Cord
Nervous System
Nerve column thatextends from the brainto the lower back.
Protected by thevertebrae
Processes reflexes
33.2 Organization of the Nervous System
Chapter 33
The Peripheral Nervous System
Nervous System
A nerve is a bundle of axons and may containsensory and motor neurons.
The peripheral nervous system (PNS) containsall the neurons that are not part of the centralnervous system.
33.2 Organization of the Nervous System
Chapter 33
The Somatic Nervous System
Nervous System
Nerves in the somatic nervous system relayinformation from external sensory receptors tothe central nervous system, and motor nervesrelay information from the central nervoussystem to skeletal muscles.
Voluntary movements and reflexes are a partof the somatic nervous system.
33.2 Organization of the Nervous System
Chapter 33
The Autonomic Nervous System
Nervous System
The autonomic nervous system carriesimpulses from the central nervous systemto the heart and other internal organs.
The body responds involuntarily, not underconscious control.
33.2 Organization of the Nervous System
Chapter 33
There are two branches of the autonomicnervous system.
Nervous System
The sympathetic nervous system is mostactive in times of emergency or stress whenthe heart rate and breathing rate increase.
The parasympathetic nervous system is mostactive when the body is relaxed.
33.2 Organization of the Nervous System
Chapter 33
Nervous System
Chapter 33
Taste and Smell
Specialized neurons in your body enable youto taste, smell, hear, see, and touch, and todetect motion and temperature.
33.3 The Senses
Nervous System
Chapter 33