The Central Nervous System

(The Brain and Spinal Cord)

The Nervous System

• Central Nervous System

– Brain and Spinal Cord

• Peripheral Nervous System

– Sensory Neurons (Afferent)

– Motor Neurons (Efferent)

• Chart p. 76

The Spinal Cord

• Extension of the Brain

– Average diameter of your fingers

– Reaches from the base of the brain, through the neck, down the hollow center of the spinal column

The Spinal Cord

• Protected by bone and spinal fluid

– Acts as a shock absorber

• Links the body with the brain

– (this is the significance when it is damaged-paralysis)

• Transmits messages between the brain and nervous system

– How??

Afferent and Efferent Neurons• Afferent neurons

– Transmit messages from sensory receptors to the spinal cord

– Sensory neurons

• Pain through someone stepping on your toe

• Nasty thoughts about the perpetrator

– 2 to 3 feet long

Afferent and Efferent Neurons

• Efferent Neurons

– Transmit messages from the spinal cord to muscles and glands

– Motor neurons

• Hopping routine after you realize your toe is hurt

• Sweating

• Hair on your arms stands up

A Way to Remember• SAME

• Sensory= Afferent, Motor= Efferent

• Neural Chain pictureInterneurons

(Carry message to and from spinal cord and brain)

Efferent Neurons(Motor Neurons)

ReceptorsEffectors

(Muscles and Glands)

Afferent Neurons(Sensory Neurons)

The Peripheral Nervous System(2 Systems: Somatic and Autonomic)

Peripheral Nervous System

• Consists of sensory and motor neurons that transmit messages to and from the brain and spinal cord

• Without this system, we would not be able to:– Perceive the world– Act on it– Allows the brain and spinal

cord to communicate with the muscles and glands of the body as well as the systems of the eyes, ears, skin, and mouth

Peripheral Nervous System

• Somatic Nervous System

– Contains sensory (afferent) and motor (efferent) neurons

– Sends messages to the central nervous system

• Sights

• Sounds

• Smells

• Body Position

Peripheral Nervous System

• Somatic Nervous System

– Controls purposeful body movements

• Raising a hand

• Winking

• Running

• Breathing

• Maintaining posture

• Maintaining balance

Peripheral Nervous System

• Autonomic (Automatic) Nervous System

– Regulates glands and muscles of internal organs

– Regulates:

• Heartbeat

• Respiration

• Digestion

• Dilation of the pupils

Peripheral Nervous System• Autonomic Nervous System

– Can be overridden by conscious control

• Example: You can control breathing

– Divided into two branches

• Sympathetic and parasympathetic

Autonomic Nervous System

• Sympathetic (has sympathy with one’s emotions)– Most active during

processes that involve the spending of body energy from stored reserves

– Fight or Flight response (allows people to deal with stressful events)

Autonomic Nervous System

• Parasympathetic

– Most active during processes that replenish reserves of energy

• Eating, drinking, rest

–Responsible for day-to-day functioning• Heartbeat,

breathing, digestion

Peripheral Nervous System

• Sympathetic and Parasympathetic Systems work together

– The parasympathetic division stimulates digestive processes, but the sympathetic branch inhibits digestion

• When we are scared or nervous, food can sit like a lump in our stomachs or we may even stop breathing

– Since the sympathetic division predominates when we feel fear or anxiety, these feelings can cause indigestion