The Nervous System

Spinal Cord

• Sends sensory impulses up to the brain and motor impulses down to the body

• Also the center of integration for reflex arcs

Meninges

• Tough membrane surrounding brain and spinal cord

Dura Mater

Outermost layer

Arachnoid Mater

Intermediate layer

Pia Mater

Innermost membrane; covers brain and spinal cord directly

Cerebrospinal Fluid

• Located within the meninges

• Constantly circulates around the brain and spinal cord

• Provides nutrients from blood and delivers waste to blood

Peripheral Nervous System

Connects CNS to other parts of the body

Cranial Nerves

• 12 pairs

• Come off of the brain

Spinal Nerves

• 31 Pairs

• Come off of the spinal cord

• Branch throughout the body

Olfactory

Sense of smell

Optic

Sense of vision

Oculomotor

• Constriction of the pupils

• Eye movement

• Raising the eyelid

Trochlear

Eye movement

Trigeminal

• Sensation of the face, scalp, and teeth

• Chewing (motion)

Abducens

Eye movement

Facial

• Sense of taste

• Facial expressions

• Secretion of saliva and tears

Vestibulocochlear

Sense of hearing and balance

Glossopharyngeal

• Sense of taste

• Secretion of saliva

• Swallowing (motion)

Vagus

• Sensation of organs in the thoracic and abdominal cavities

• Vocal ability

• Swallowing (motion)

Accessory

• Shrugging of the shoulders

• Rotation of the head

Hypoglossal

Tongue movement

Parkinson’s Disease

• Deficiency of dopamine

• Without dopamine, the impulse to skeletal muscles does not transmit properly, which affects movement, often causing tremors

• Idiopathic

Multiple Sclerosis

• Myelin is destroyed

• Without myelin, conduction of impulse is impaired and weakness occurs

• Autoimmunity or viral infection

Cerebrovascular Accident (CVA)

• Stroke

• Cerebral blood vessels bleed or stop getting blood flow

• Injury; Blood vessel disease

Cerebral Palsy

• Permanent damage to motor control areas of the brain

• Difficulty with movement and posture

• Injury at birth, Maternal disease, Reduced oxygen to baby’s brain

Dementia

• Degenerative diseases characterized by impairment of brain function

• Neurons are damaged causing malfunctions of the cerebrum

Alzheimer’s Disease

• Type of dementia

• Progressive disorder where neurons and connections are destroyed

• Idiopathic

Seizure Disorders

• Sudden bursts of abnormal neuron activity

• Epilepsy

Epilepsy

• Chronic seizure episodes

• Tumors of physical and chemical agents

• Usually idiopathic

Meningitis

• Inflammation of the meninges

• Caused by a bacteria or virus

Paralysis

• Loss of voluntary movement and sensation

• Paraplegia

• Quadriplegia

Paraplegia

Paralysis of both legs

Quadriplegia

Paralysis of all 4 limbs

Bell’s Palsy

• Damage to the facial nerve

  • Can cause muscle weakness, drooling, tearing, impairment of taste

• Usually not permanent

Herpes Zoster (Shingles)

• Viral infection of the skin, usually in adults

• Caused by the same virus as chickenpox

• Virus reactivates and travels along a nerve to specific area of the body

Primary Functions of Nervous System

• Communication between organs

• Integration of body functions

• Control of body functions

• Recognition of sensory stimuli

Sensory Input

• Sense receptors detect a stimulus inside or outside of the body and send a message to the CNS

• Performed by the sensory division of the PNS

Integration

• Processing and interpreting the sensory input to make an observation or the make a decision for a response

• Performed by the CNS

Motor Output

• Activated effectors carry out the response to the stimulus

• Performed by the motor division of the PNS

Central Nervous System

• Brain and spinal cord

• Integration

Peripheral Nervous System

• Nerve and sense organs

• Sensory input and motor output

Motor Division

• CNS to muscles/glands

• Output to effectors

Sensory Division

• Receptors to CNS

• Input from receptors

Somatic Nervous System

• Skeletal muscles

• Voluntary effectors

Autonomic Nervous System

• Smooth/Cardiac Muscles: Glands

• Involuntary effectors

Nerve Cells

Neurons

Types of Neurons

• Sensory

• Interneurons

• Motor neurons

Sensory Neurons

• Carry out sensory input function of the nervous system

• Primarily found in PNS

Interneurons

• Perform integration

• Only found in CNS

Motor Neurons

• Perform the motor output function

• Primarily found in PNS

Dendrite

• Transmit impulse towards cell body

• Neuron can have many

Cell Body

Contains the nucleus

Axon

Transmits impulse away from cell body; 1 per neuron

Myelin

Insulates axon and allows for impulses to travel faster

Schwann cell

Wraps around axon; forms