The Human Nervous System

Major OrgansBrain, Spinal Chord, Nerves

Major functions

• Sensory– Millions of sensory receptors detect changes, called

stimuli, which occur inside and outside the body.

• Integration– Decisions that are made based on the sensory input.

• Motor– The response of the nervous system by sending

signals to muscles, causing them to contract, or to glands, causing them to produce secretions.

The Neuron ~functional unit of the nervous system!

All neurons have 3 main parts:1. Dendrites receive information from another cell

and transmit the message to the cell body. 2. The cell body contains the nucleus, mitochondria

and other organelles typical of eukaryotic cells 3. The axon conducts messages away from the cell

body.

Types of Neurons

• Neurons can also be classified by the direction that they send information.– Sensory (or afferent) neurons: send information

from sensory receptors (e.g., in skin, eyes, nose, tongue, ears) TOWARD the central nervous system.

– Motor (or efferent) neurons: send information AWAY from the central nervous system to muscles or glands.

– Interneurons: send information between sensory neurons and motor neurons. Most interneurons are located in the central nervous system.

Neuron Communication

• Neurons communicate with each other through the use of neurotransmitters.

• Neurotransmitters are released from the axon into the synaptic cleft between an adjacent axons dendrite

Pathway of a Nerve Stimulus

Dendrite receivesstimulus (impulse)

Impulse travelsthrough the cell

body

Tip of axon releases

neurotransmitter into the synaptic cleft

Axon takes impulse away from

the cell body

CNS & PNSCentral Nervous System & Peripheral

Nervous System

Nervous System Regulation

• The sympathetic & para-sympathetic systems are in control of the major organs of the body.

CommonNervous System

Diseases

Depression& Addictions

(neurotransmitters)

Alzheimer’s & Schizophrenia

(physiology)

Carpel Tunnel&

Spina Bifida(nerves)

Bacterial & Viral disease

Rabies is spread by infected saliva that enters the body through a bite or broken skin. The virus travels from the wound to the brain, where it causes swelling, or inflammation, and if untreated…death

Haemophilus influenzae , Streptococcus neumoniae, group B Streptococcus, Listeria monocytogenes, and Neisseria meningitidis can all cause meningitis. Symptoms include brain damage, hearing loss, learning disabilities and possible death. It is spread through secretions, air and contaminated food.

Career Opportunities• Child Neurology - specializes in the

diagnosis and management of neurologic conditions in children.

• Clinical Neurophysiology- A neurologist who specializes in the diagnosis and management of central, peripheral, and autonomic nervous system disorders using a combination of clinical evaluation and electrophysiologic testing such as electroencephalography (EEG), electromyography (EMG), and nerve conduction studies (NCS), among others.

• Pain Medicine - provides a high level of care, either as a primary physician or consultant, for patients experiencing problems with acute, chronic or cancer pain in both hospital and ambulatory settings.

Drugs & the Nervous System

Nicotine causes the nervous system to become more sensitive & stimulated. This leads to short term effects: – increase in blood pressure – heart rate– faster respiration constriction of the arteries.

Long-term effects of smoking on the nervous system are quite dangerous. People who smoke are more susceptible to cancers and muscular sclerosis.

Drugs, continued

Anabolic Steroids have

many effects on many

different organ systems. For the nervous system, steroids cause an increase in aggression ~ “Roid Rage”, irritability and severe fluctuation in moods. Users can also develop a dependency on this drug ~ they can become addicted. Users are also at an increased risk of committing suicide because of severe depression caused by steroid use.

Drugs, ContinuedAlcohol has profound effects on neurons and the nervous

system. Alcohol:• Impairs memory, judgment & reasoning• Depresses the actions of the Central Nervous System;

therefore, decreasing reaction times and vital organ function.• Causes neuropathy,

dementia, Wernicke's

encephalopathy and clinical

depression• Can lead to suicide and

sleep disorders

Drugs, continued

Methamphetamine is a

stimulant that causes actual physical changes to the brain. It effects the level of dopamine in the brain and is highly addictive.

Stimulants will increase the activity of the Central Nervous System

Anxiety, confusion, insomnia, depression and mood disturbances and displays of violent behavior are common with “meth” use.

Psychotic episodes are prevalent, such as paranoia, hallucinations and delusions.