Exploring the Exploring the Human Nervous Human Nervous SystemSystem

Chapter 9 pp. 202-247Chapter 9 pp. 202-247

Introduction to the Introduction to the Nervous SystemNervous System

What is the nervous system?What is the nervous system? It is a communication system that It is a communication system that

gathers information, interprets that gathers information, interprets that information, and makes either information, and makes either conscious or subconscious reactions.conscious or subconscious reactions.

The fundamental unit of the nervous The fundamental unit of the nervous system is the neuron (nerve cell)system is the neuron (nerve cell)

Vocabulary: due Vocabulary: due WednesdayWednesday

Peripheral nervous system Peripheral nervous system (PNS)(PNS)

Central nervous system (CNS)Central nervous system (CNS) Nerve impulseNerve impulse DendriteDendrite AxonAxon NerveNerve Sensory receptorSensory receptor Somatic nervous systemSomatic nervous system Autonomic nervous systemAutonomic nervous system MyelinMyelin Sensory neuronsSensory neurons InterneuronsInterneurons Brain stemBrain stem CerebellumCerebellum SulcusSulcus

Motor neuronsMotor neurons Nerve pathways p.218Nerve pathways p.218 SynapseSynapse NeurotransmitterNeurotransmitter Excitatory response p. 214Excitatory response p. 214 Inhibitory response p.214Inhibitory response p.214 Reflex arcReflex arc ReflexReflex Meninges (meninx)Meninges (meninx) White matterWhite matter Grey matterGrey matter Spinal nervesSpinal nerves CerebrumCerebrum DiencephalonDiencephalon fissuresfissures convolutionsconvolutions

The Fundamentals of the The Fundamentals of the Nervous SystemNervous System

Composed of Composed of 2 types of cells2 types of cells Neurons: nerve cell that transmits impulsesNeurons: nerve cell that transmits impulses Neuroglia: helper cells that aid and protect the Neuroglia: helper cells that aid and protect the

parts of the nervous system parts of the nervous system What are nerves? What are nerves?

– Bundles of nerve fibersBundles of nerve fibers

Divided into Divided into 2 main branches2 main branches Central Nervous System (CNS)Central Nervous System (CNS)

Brain and spinal cordBrain and spinal cord Peripheral Nervous System (PNS)Peripheral Nervous System (PNS)

Consists of perpheral nerves that connect the CNS to Consists of perpheral nerves that connect the CNS to the rest of the bodythe rest of the body

The nervous system provides The nervous system provides sensory, integrative, and motor sensory, integrative, and motor functionsfunctions to the body. to the body. Motor functions can be divided into Motor functions can be divided into

the consciously controlled “somatic the consciously controlled “somatic nervous system” and the unconscious nervous system” and the unconscious “autonomic system”.“autonomic system”.

Neuroglial cellsNeuroglial cells

FunctionFunction to fill spaces, support neurons, to fill spaces, support neurons, provide framework, produce myelin, provide framework, produce myelin, and carry on phagocytosis.and carry on phagocytosis.

The only neuroglial cell we will look at is The only neuroglial cell we will look at is the the Schwann cell.Schwann cell. Myelin producing neuroglial cell located in Myelin producing neuroglial cell located in

the PNS.the PNS. MyelinMyelin is a fatty covering that protects and is a fatty covering that protects and

insulates an axon. It helps impulses insulates an axon. It helps impulses transmit easier.transmit easier.

Neuron StructureNeuron Structure Cell body containing a Cell body containing a

nucleusnucleus Nerve fiber contains a Nerve fiber contains a

single axon and many single axon and many dendrites.dendrites.

Dendrites carry Dendrites carry impulses from other impulses from other neurons to the cell neurons to the cell body.body.

Axons carry impulses Axons carry impulses from the cell body to from the cell body to dendrites of dendrites of neighboring neurons.neighboring neurons.

Functional Classification of Functional Classification of NeuronsNeurons

SensorySensory gather data; detect changes in environmentgather data; detect changes in environment Located in the PNSLocated in the PNS

InterneuronsInterneurons located in CNS located in CNS Link other neuronsLink other neurons

MotorMotor carry impulses from the CNS to effectors carry impulses from the CNS to effectors

(muscles or organs responding to change).(muscles or organs responding to change). Located in the PNSLocated in the PNS

Nerve ImpulseNerve Impulse

ConductionConduction Unmyelinated fibers conduct impulses over Unmyelinated fibers conduct impulses over

their entire membrane surface.their entire membrane surface. Myelinated fibers conduct impulses from Myelinated fibers conduct impulses from

node of Ranvier to node of Ranvier, process node of Ranvier to node of Ranvier, process called called saltatory conductionsaltatory conduction..

Saltatory conduction is faster than conduction on Saltatory conduction is faster than conduction on unmyelinated neurons.unmyelinated neurons.

Follows the “All-or-None Response”Follows the “All-or-None Response” Junction between 2 neurons is called a Junction between 2 neurons is called a

synapsesynapse..

How do impulses get across the synapse?How do impulses get across the synapse? Neurotransmitters or chemical messengers, Neurotransmitters or chemical messengers,

are released into the synaptic cleft.are released into the synaptic cleft. If the neurotransmitter allows for an increase If the neurotransmitter allows for an increase

in sodium ion permeability, then an impulse is in sodium ion permeability, then an impulse is triggered.triggered.

If the neurotransmitter decreases the flow of If the neurotransmitter decreases the flow of sodium ions through the path, then the sodium ions through the path, then the impulse is stopped.impulse is stopped.

There are at least 50 kinds of There are at least 50 kinds of neurotransmitters within the nervous system.neurotransmitters within the nervous system.

ReflexesReflexes

An automatic, unconscious An automatic, unconscious response to a stimulusresponse to a stimulus

Stretch reflexes: Occur when a Stretch reflexes: Occur when a muscle is stretched by a tap over muscle is stretched by a tap over its tendon. Stretch receptors its tendon. Stretch receptors called called muscle spindlesmuscle spindles, , initiating initiating an impulse over a reflex arc.an impulse over a reflex arc.

ReflexesReflexes Reflexes: “ Special” ResponsesReflexes: “ Special” Responses

Produce rapid, involuntary movement or Produce rapid, involuntary movement or responseresponse

Important in times of dangerImportant in times of danger Example: Blinking eyelids when insect approaches Example: Blinking eyelids when insect approaches

eye or when startled by unexpected loud noiseeye or when startled by unexpected loud noise Why are reflexes so fast?Why are reflexes so fast?

Involve few neurons Involve few neurons Many reflexes never reach the brain; travel only as Many reflexes never reach the brain; travel only as

far as the spinal cordfar as the spinal cord Example: Blinking eyelid occurs before cerebrum is Example: Blinking eyelid occurs before cerebrum is

even aware of dangereven aware of danger

Reflex ArcReflex Arc

Simplest type of nerve pathwaySimplest type of nerve pathway What happens in a reflex arc?What happens in a reflex arc?

Sensory receptor at the dendrite end Sensory receptor at the dendrite end of sensory neuron detect a changeof sensory neuron detect a change

Sensory neuron communicates with Sensory neuron communicates with interneurons in CNSinterneurons in CNS

Interneurons communicate with Interneurons communicate with motor neurons, whose axons lead out motor neurons, whose axons lead out to effector muscles or glands.to effector muscles or glands.

Examples of ReflexesExamples of Reflexes Knee-jerk reflexKnee-jerk reflex

Response: knee Response: knee extensionextension

Effector muscle: Effector muscle: quadricepsquadriceps

Ankle-jerk reflexAnkle-jerk reflex Response:Response: Effector muscle:Effector muscle:

Biceps-jerk reflexBiceps-jerk reflex Response:Response: Effector muscleEffector muscle

Triceps-jerkTriceps-jerk Response:Response: Effector muscleEffector muscle

Plantar reflexPlantar reflex Response:Response: Effector muscle:Effector muscle: Babinski:Babinski:

MeningesMeninges Layered membranes that lie between bony Layered membranes that lie between bony

coverings and the soft tissues of the CNScoverings and the soft tissues of the CNS Act to protect the brain and spinal cord.Act to protect the brain and spinal cord. Three layers:Three layers:

Dura mater: outermost layer; tough, white, fibrous Dura mater: outermost layer; tough, white, fibrous connective tissue; many blood vessels and nervesconnective tissue; many blood vessels and nerves

Arachnoid mater: middle layer; weblike; no blood Arachnoid mater: middle layer; weblike; no blood vesselsvessels

Subarachnoid space: contains watery cerebrospinal fluidSubarachnoid space: contains watery cerebrospinal fluid Pia mater: inner most; contains many nerves and Pia mater: inner most; contains many nerves and

blood vessels that blood vessels that nourish the cells of the brain nourish the cells of the brain and spinal cord.and spinal cord.

The CNS: Spinal CordThe CNS: Spinal Cord The slender nerve The slender nerve

column that passes column that passes downward from the downward from the brain through the brain through the vertebral column.vertebral column.

Consists of 31 Consists of 31 segments, each segments, each giving rise to a pair giving rise to a pair of spinal nerves.of spinal nerves.

Spinal nerves are Spinal nerves are accessory organs to accessory organs to the PNS.the PNS.

Two major Two major functionsfunctions Conducting nerve Conducting nerve

impulsesimpulses Center for spinal Center for spinal

reflexes.reflexes. Knee-jerk reflexKnee-jerk reflex Withdrawal Withdrawal

reflexesreflexes

Spinal cord innervationsSpinal cord innervations Cervical vertebrae (1-7) Cervical vertebrae (1-7)

located in the neck located in the neck Thoracic vertebrae (1-12) in Thoracic vertebrae (1-12) in

the upper back (attached to the upper back (attached to the ribcage) the ribcage)

Lumbar vertebrae (1-5) in the Lumbar vertebrae (1-5) in the lower back lower back

Sacral vertebrae (1-5) in the Sacral vertebrae (1-5) in the hip area hip area

Coccygeal vertebrae (1-4 Coccygeal vertebrae (1-4 fused) in the tailbone fused) in the tailbone

The CNS: Brain AnatomyThe CNS: Brain Anatomy Four regions of the brain:Four regions of the brain:

Cerebrum:Cerebrum: Largest regionLargest region Nerve centers associated with sensory and motor Nerve centers associated with sensory and motor

functions/ provides higher mental functionsfunctions/ provides higher mental functions Cerebellum:Cerebellum:

Sits below and behind the cerebrumSits below and behind the cerebrum Coordination and balanceCoordination and balance

Brain Stem:Brain Stem: Involuntary life processes (ie. Breathing and heart rate)Involuntary life processes (ie. Breathing and heart rate)

Diencephalon:Diencephalon: Processes sensory informationProcesses sensory information

The Cerebral CortexThe Cerebral Cortex

Structure of the cerebrumStructure of the cerebrum Divided into two cerebral Divided into two cerebral

hemispheres connected hemispheres connected internally by the corpus internally by the corpus callosum.callosum.

Surfaces ridges are called Surfaces ridges are called convolutions. A shallow convolutions. A shallow groove is a sulcus; a deep groove is a sulcus; a deep groove is a fissure.groove is a fissure.

Cerebral cortex: thin layer Cerebral cortex: thin layer of gray matter which is the of gray matter which is the outermost portion of the outermost portion of the cerebrum. Contains 75% of cerebrum. Contains 75% of all neuron cell bodiesall neuron cell bodies

4 lobes4 lobes Frontal: reasoning; planning, Frontal: reasoning; planning,

parts of speech and parts of speech and movement, emotions, and movement, emotions, and problem solvingproblem solving

Parietal: perception of stimuli Parietal: perception of stimuli related to touch, pressure, related to touch, pressure, temperature and paintemperature and pain

Temporal: perception and Temporal: perception and recognition of sound and recognition of sound and memorymemory

Occiptal: visionOcciptal: vision

Answer the following!Answer the following! If Christopher is in a car accident and due to If Christopher is in a car accident and due to

brain damage loses his sight, which lobes of the brain damage loses his sight, which lobes of the brain were probably damaged?brain were probably damaged?

When you go to the refrigerator and reach for a When you go to the refrigerator and reach for a can of pickles, which lobe of the brain are you can of pickles, which lobe of the brain are you using?using?

When you are listening to music on earphones, When you are listening to music on earphones, which lobe of the brain are you using?which lobe of the brain are you using?

When an Olympic gymnast does a flip on the When an Olympic gymnast does a flip on the balance beam, which lobe(s) of the brain is she balance beam, which lobe(s) of the brain is she using?using?

Diencephalon and Brain Diencephalon and Brain StemStem

DiencephalonDiencephalon Located between Located between

cerebral hemispheres, cerebral hemispheres, below the corpus below the corpus callosum.callosum.

Includes the Includes the thalamus, thalamus, hypothalamus, optic hypothalamus, optic chiasma, pituitary chiasma, pituitary gland, mammillary gland, mammillary bodies, and pineal bodies, and pineal glandgland

Brain StemBrain Stem Located from the Located from the

diencephalon to diencephalon to the spinal cord.the spinal cord.

Includes the:Includes the: MidbrainMidbrain PonsPons Medulla oblongataMedulla oblongata

CerebellumCerebellum

Reflex center for processing information Reflex center for processing information concerning body positionconcerning body position

Injuries to this area could lead to:Injuries to this area could lead to: TremorsTremors Inaccurate movements of voluntary musclesInaccurate movements of voluntary muscles Loss of muscle toneLoss of muscle tone An awkward walkAn awkward walk Loss of equilibriumLoss of equilibrium

The PNSThe PNS

Somatic nervous Somatic nervous systemsystem Cranial and spinal Cranial and spinal

nerves that nerves that connect to skin connect to skin and skeletal and skeletal musclesmuscles

Conscious Conscious activitiesactivities

Autonomic Autonomic nervous systemnervous system Connects CNS to Connects CNS to

the lining of the lining of hollow organs and hollow organs and glandsglands

Controls Controls unconscious unconscious activitiesactivities

Cranial and Spinal Cranial and Spinal nervesnerves