Chapter 23Chapter 23A&PA&P

The Nervous SystemThe Nervous System

IntroductionIntroduction

The nervous system is the body’s The nervous system is the body’s information gather, storage center information gather, storage center and control system.and control system.

It controls, directs and coordinates It controls, directs and coordinates body functions.body functions.

The nervous system is divided into The nervous system is divided into the central nervous system and the the central nervous system and the peripheral nervous system.peripheral nervous system.

ObjectivesObjectives Identify the structures that make up the Identify the structures that make up the

nervous system.nervous system. Explain how nerve impulses are Explain how nerve impulses are

transmitted.transmitted. State the functions of the central nervous State the functions of the central nervous

system, the peripheral nervous system system, the peripheral nervous system and the autonomic nervous system.and the autonomic nervous system.

Identify disorders associated with the Identify disorders associated with the nervous system.nervous system.

Lifespan considerations.Lifespan considerations.

Neurons, Nerve Fibers, Neurons, Nerve Fibers, Nerves and TractsNerves and Tracts

Neurons / Nerve CellNeurons / Nerve Cell

All nervous system tissue is made up of All nervous system tissue is made up of nerve cells, called neurons, and their nerve cells, called neurons, and their supporting tissues called neuroglia.supporting tissues called neuroglia.

These cells allow the body to interacts These cells allow the body to interacts with its internal and external with its internal and external environments.environments.

There are 3 types of neurons: motor There are 3 types of neurons: motor (doers), sensory (sensors) and (doers), sensory (sensors) and interneurons (communicators).interneurons (communicators).

Motor NeuronsMotor Neurons

Motor neurons cause muscles to Motor neurons cause muscles to contract and glands to secrete, and contract and glands to secrete, and organs to perform their functions.organs to perform their functions.

They can also inhibit these actions.They can also inhibit these actions. Motor neurons are also known as Motor neurons are also known as efferentefferent meaning they carry meaning they carry messages away from the cell body to messages away from the cell body to the muscles and organs.the muscles and organs.

Motor neuronMotor neuron Motor neurons have a Motor neurons have a

nucleated cell body nucleated cell body with process with process extending away from extending away from the cell body.the cell body.

These nerve fibers These nerve fibers are called axons and are called axons and dendrites.dendrites.

Dendrites carry Dendrites carry impulses to the cell impulses to the cell body and the axon body and the axon carries impulses carries impulses away from it.away from it.

Motor neuronsMotor neurons

Most axons are covered with a fatty Most axons are covered with a fatty insulating substance called the myelin insulating substance called the myelin sheath.sheath.

Axons with myelin sheath transmit Axons with myelin sheath transmit impulses faster than those without.impulses faster than those without.

Damage to unmyelinated cells is Damage to unmyelinated cells is usually permanent.usually permanent.

The axon and dendrites allow neurons The axon and dendrites allow neurons to communicate.to communicate.

What does this mean?What does this mean?

Hit your thumb Hit your thumb with a hammer and with a hammer and the motor neurons the motor neurons allow you to pull allow you to pull back you hand.back you hand.

Smell fresh baked Smell fresh baked bread and your bread and your mouth waters.mouth waters.

Dust in your eye Dust in your eye causes you to blink.causes you to blink.

Sensory neuronsSensory neurons

The second types of nerve cell is known The second types of nerve cell is known as the sensory neuron or as the sensory neuron or afferentafferent neurons.neurons.

Sensory neurons have sensor receptors Sensory neurons have sensor receptors that allow transmission or impulses, or that allow transmission or impulses, or messages, to the central nervous system.messages, to the central nervous system.

Therefore our ability to feel the hammer, Therefore our ability to feel the hammer, smell the bread or feel the discomfort smell the bread or feel the discomfort from the dust.from the dust.

InterneuronsInterneurons

Third type of nerve cell.Third type of nerve cell. Found in the central nervous system Found in the central nervous system

and mediate impulses between the and mediate impulses between the motor and sensory neurons.motor and sensory neurons.

Nerve fibers, Nerves and Nerve fibers, Nerves and TractsTracts

A nerve is a bundle of nerve fibers, A nerve is a bundle of nerve fibers, located outside the brain and spinal located outside the brain and spinal cord, that connect various parts of the cord, that connect various parts of the body.body.

Sensory nerves carry messages to the Sensory nerves carry messages to the CNS (brain) and the motor nerves CNS (brain) and the motor nerves carry messages away from the CNS.carry messages away from the CNS.

Groups of nerve fibers within the CNS Groups of nerve fibers within the CNS are known as tracts.are known as tracts.

Nerve ImpulsesNerve Impulses Chemical Chemical

neurotransmitters are neurotransmitters are stored in the axon stored in the axon terminals.terminals.

The space between The space between neurons is called a neurons is called a synapse.synapse.

Information is received Information is received in the dendrite, passed in the dendrite, passed through the cell body, through the cell body, travels down the axon travels down the axon and over the synapse to and over the synapse to the next dendrite.the next dendrite.

The Central Nervous The Central Nervous SystemSystem

Brain

CerebrumLargest part

of thebrain

Thoughtintelligence

CerebellumRegulates &Coordinates

Body movement

BrainstemConnectsCerebrumTo spinal

cord

Spinal CordConducts info

To & fromthe brain.

Protected byMeninges

Dura MatterArachnoid Pia Matter

The Peripheral Nervous The Peripheral Nervous SystemSystem

The peripheral nervous system The peripheral nervous system has 12 pairs of has 12 pairs of cranialcranial nerves nerves and 31 pairs of and 31 pairs of spinalspinal nerves. nerves.

Peripheral nerves with special Peripheral nerves with special functions for the functions for the autonomicautonomic nervous system.nervous system.

Cranial NervesCranial Nerves The cranial nerves The cranial nerves

conduct impulses conduct impulses between the brain between the brain and the head, neck, and the head, neck, chest and abdomen.chest and abdomen.

Impulses for smell, Impulses for smell, vision, hearing, vision, hearing, pain, touch, pain, touch, temperature and temperature and pressure, voluntary pressure, voluntary and involuntary and involuntary muscles control.muscles control.

Peripheral Nervous Peripheral Nervous StsyemStsyem

Spinal nerves Spinal nerves carry impulses carry impulses from skin, from skin, extremities and extremities and internal body internal body structure not structure not supplied by cranial supplied by cranial nerves.nerves.

Autonomic Nervous Autonomic Nervous SystemSystem

Controls involuntary muscles and Controls involuntary muscles and functions including heartbeat, blood functions including heartbeat, blood pressure, intestinal contractions and pressure, intestinal contractions and glandular secretions.glandular secretions.

Autonomic Nervous Autonomic Nervous SystemSystem

SympatheticSympathetic

Speeds up Speeds up functionsfunctions

Stimulated with Stimulated with exerciseexercise

Stimulated with Stimulated with anger, excitement anger, excitement or fear.or fear.

ParasympatheticParasympathetic

Slows down Slows down functionsfunctions

Activated with Activated with relaxationrelaxation

Activated when Activated when under stimulated under stimulated for too longfor too long

What happens with fear?What happens with fear?

The Sensory SystemThe Sensory System