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Nervous System

The Nervous System

Two main divisions– Central Nervous System

(CNS) includes the brain and spinal cord

– Peripheral Nervous System (PNS) contains nerves which carry info between the CNS and other organs

Central Nervous System

The brain receives impulses and sends impulses back to the body

The spinal cord connects the brain to the body

CNS: The Brain (UP 5)

3 major regions– Cerebrum– Cerebellum– Brainstem

Cerebrum

Cerebellum

Brainstem

CNS: The Cerebrum Largest part of the brain Involved in voluntary activities, intelligence,

and consciousness Divided into 4 lobes

– Frontal - personality– Temporal - auditory

– Parietal - senses – Occipital - visual area

Parietal

Occipital

Frontal

Temporal

CNS: Cerebellum & Brainstem

Cerebellum – balance and coordination

Cerebellum

Brainstem includes the pons and medulla oblongata– Involuntary functions

– heart rate, breathing

Brainstem

Medulla Oblongata

PNS: Peripheral Nervous System All nerves that are NOT part of the brain

or spinal cord Two major divisions of the PNS:

– Sensory division sends impulses from sense organs (ears, nose, etc.) to the CNS

– Motor division send impulses from the CNS to the muscles or glands

PNS: Motor Divisions Motor division is then divided into the

autonomic and somatic nervous systems

Somatic System – regulates activities under conscious control such as muscle movement– Also involved with reflexes

Autonomic Nervous System Regulates automatic, involuntary

actions– Parasympathetic Nervous System

decreases heart rate and stimulates digestion; “rest and digest”

– Sympathetic Nervous System increases heart rate; “fight or flight”

These systems have opposite effects

Neuron Structure (UP 83)

Cell Body

Cytoplasm

Nucleus

Dendrites

MyelinAxon

Muscle (effector)

End Brush Motor End Plate

Neurons Three types:

– Sensory: carry impulses from sense organs to CNS

– Motor: carry impulses from CNS to muscles/glands

– Interneurons: connect motor and sensory neurons

Neural Impulses Impulses move along a neuron due to

electrical changes in the membrane

Neural Impulses (UP 83)

Membrane is polarized, more negative inside

Na+ ions enter; membrane depolarizes

Repolarization follows depolarization

Impulse travels the axon

–http://highered.mcgraw-hill.com/olc/dl/120107/bio_d.swf

Neural Impulses Resting potential – polarized state,

negative charge inside membrane Threshold –minimum stimulus needed

to activate a neuron Action potential – depolarization &

repolarization of membrane Myelin increases rate of impulse

Synapses Location where one neuron

transfers an impulse to a cell– Neuron to neuron– Neuron to muscle/gland

Chemicals called neurotransmitters carry signals across a synapse– Acetylcholine and serotonin

Synapses

http://www.bishopstopford.com/faculties/science/arthur/synapse.swf

Reflex Arc Reflexes prevent injury Impulse travels from sensory neuron

interneuron motor neuron

http://www.sumanasinc.com/webcontent/anisamples/nonmajorsbiology/reflexarcs.html

Reflex Arc (UP 84)

Association Neuron

(interneuron)

Sensory Neuron

Cell Body (Sensory Neuron)

Motor Neuron

Receptors (on dendrites)

Synapse

Synapse

Effector (muscle)Motor End Plates

Animations

Action Potential– http://highered.mcgraw-hill.com/olc/dl/120107/bio_d.swf

– http://outreach.mcb.harvard.edu/animations/actionpotential.swf

Chemical Synapse– http://www.bishopstopford.com/faculties/science/arthur/synapse.swf

– http://highered.mcgraw-hill.com/olc/dl/120107/anim0015.swf– http://outreach.mcb.harvard.edu/animations/synaptic.swf

Electroencephalogram (EEG) Records electrical activity of the brain Diagnosis of neurological diseases: stroke,

epilepsy, tumors, and sleep disorders

EEG Activity

Behavior Impacts EEG

EEG During Seizures

Diagnostic Techniques MRI – Magnetic Resonance Imaging uses

radio waves and VERY powerful magnets to create images of the brain

Used to image soft tissue, not bone or teeth

MRI of the Brain

CT Scan Computerized Tomography 3-D x-ray image based on tissue density

– Bone appears white, liquids/gases are black, and various tissues are grey

Used to diagnose tumors

PET Scan Positron Emission Tomography Creates images based on the detection of radiation particles Used to detect tumors, seizure disorders, and evaluate

patients with memory loss

Brain Death Irreversible cessation of brain activity for 24

hours so that cardiopulmonary function must be maintained by machine