Nervous
System Outline
Health Occupations
Nervous System Functions

Directs the functions of all human body
systems
– 100 Billion Nerve cells

Carry messages from brain to rest of body
Neurons
The basic element of nervous system
 Highly specialized
 Vary in function, shape, and size
 Separated by synapses

– Gaps in between each neuron

Neurotransmitters
– Stimulates impulse to jump to next nerve
Neurons

3 Parts
– Cell Body
 Have fibers to reach out to send or
receive impulses
– Dendrites
 Thin branching extensions of cell body
 Conduct nerve impulses to cell body
– Axon
 Conducts nerve impulses away from cell body
 Covered by a myelin sheath
– Fatty tissue that makes impulse travel faster
 End of axon has fibers that let the impulse leave the
nerve
Neurons

2 Basic Properties
– Excitability
 Ability to respond to a stimulus
– Conductivity
 Ability to transmit a signal
Neurons

3 Types
– Efferent (motor)
 Carry information to muscles and glands from CNS
– Afferent (sensory)
 Carry information from sensory system to CNS
– Interneurons
 Carry and process sensory information
Neuron bundles = Nerves
 Stimulus
Receptor
Nerve
Receptor

Impulse
Neuroglias
Support, connect, protect,
and remove debris
 Do not transmit impulses
 Form blood-brain barrier

– Permits some chemical
substances to reach the brain’s
neurons but blocks most
others
Central Nervous System (CNS)

Consists of:
– Brain
– Spinal cord

Center of Control
CNS Functions
Receives and interprets all stimuli
 Sends nerve impulses to instruct muscles
and glands to take over or respond to
certain actions
 Causes Voluntary and Involuntary actions

Brain Divisions
Brainstem
 Cerebellum
 Cerebrum
 Diencephalon


Midbrain
Brain Stem
– Visual reflexes

Pons
– Controls certain respiratory functions

Medulla Oblongata
– Regulates heart & lung functions
– Swallowing
– Vomiting
– Coughing
– sneezing
Cerebellum

Coordinates musculoskeletal movement
– Maintains balance
– Posture
– Muscle tone
Cerebrum
 2 hemispheres
– Left and Right

Cerebral Cortex
– Conscious decision making

Four Lobes
– Frontal
 Moral Behavior, voluntary motor movements
– Parietal
 Controls and interprets senses and taste
– Temporal
 Memory, equilibrium, emotion, hearing
– Occipital
 vision
Diencephalon
Deep portion of brain
 Contains:

– Thalamus
– Hypothalamus
Relay center for sensations
 Controls:

– Heart rate
– Blood pressure
– Temperature regulation
– Water and electrolyte balance
– Digestive functions
– Glandular activities
Cerebrospinal Fluid (CSF)
Fills the area between the brain and
cranium
 Watery fluid that contains various
compound
 Cradles and cushions brain

Spinal Cord
Extends from base of brain to first
lumbar vertebrae in back
 Protected by:

– Cerebrospinal fluid
– Vertebral column
– Meninges
 3 layers of membranes that cover brain
and spinal cord
Meninges

Dura Mater (outer layer)
– Tough, fibrous
– Contains channels for blood to enter brain
tissue

Arachnoid Mater (middle layer)
– Web-like structure

Pia Mater (innermost layer)
– Contains blood vessels that nourish spinal
cord
Peripheral Nervous System

12 Cranial Nerves
– Carry impulses to and from
the brain

31 pairs of spinal nerves
– Carry messages to and from
the spinal cord and the torso
and extremities of the body
Peripheral Nervous System

2 Subsystems according to
function
– Somatic Nervous System
– Autonomic Nervous System
Somatic Nervous System
Receive and process sensory input from
the skin, muscles, tendons, joints, eyes,
tongue, nose and ears
 Excite voluntary contraction of skeletal
muscles

Autonomic Nervous System
Carry impulses from the central nervous
system to glands, various involuntary
muscles, cardiac muscle, and membranes
 Stimulates organs, glands and senses by
stimulating secretions of substances
 Divided into sympathetic and
parasympathetic divisions

Autonomic Nervous System

Sympathetic
– Operates when the body
is under stress
– Activates responses
necessary to react in
dangerous or abnormal
situations
– Fight or Flight response

Parasympathetic
– Operates to keep the
body in homeostasis
under normal conditions
The End