Transcript Divisions of the Nervous System

Divisions of the
Nervous System
Unit 8: Human Body Systems
Chapter 35-3
Divisions of the Nervous
System
• 2 major divisions:
Nervous
System
Central
Nervous
System
Peripheral
Nervous System
Brain
Spinal Cord
Nerve cells
A. The Central Nervous
System (CNS)
• Control center of the
body
• Relays messages,
processes & analyzes
information
• Made of two parts:
– Brain
– Spinal cord
• 1. The Brain
– Impulses flow to and from the brain
– 100 billion neurons, mainly
interneurons
• 2. Spinal Cord
– Main communication
link between brain
and the rest of the
body
– Processes
information such as
reflexes
1. Protection of the CNS
• Brain and spinal cord are protected by:
• a) Bone – skull and vertebrae
• b) Meninges – layers of connective
tissue that surround the organs
• c) Cerebrospinal fluid – fluid found in
between meninges and organ
– Acts as a shock absorber
– Continually circulates around the brain
• DISEASE: Meningitis
– Inflammation of the meninges
– Can be caused by an viral ,
bacterial or microorganism
infection
– Causes headaches, neck
stiffness, confusion, sensitivity
to light and sound
– Can be life threatening
• DISEASE: Hydrocephalus
(“water on the brain”)
– Accumulation of CSF in the brain
– Exerts pressure on the brain
causing brain damage
2. Regions of the Brain
• Regions of the Brain
– Cerebral hemispheres (Left & Right)
– Diencephalon
– Brain stem
– Cerebellum
a. Cerebral Hemispheres
(Cerebrum)
• Left and right
hemispheres
– Left brain – logic,
language, math
– Right brain – creativity
• Connected by the
corpus callosum
(communication link
between right and
left)
• The surface is
made of ridges
(gyri) and
grooves (sulci)
Fissures (deep grooves)
divide the cerebrum
into four lobes
1. Occipital Lobe: visual
integration
2. Parietal: spatial
knowledge, math
3. Temporal: memories,
auditory, language
4. Frontal: emotion, future
planning, judgment,
muscle movements,
language
• Limbic System –
involved in emotion,
motivation, arousal,
memory, and learning
– Amygdala – fear
– Hippocampus –
memory formation
b. Diencephalon
• Relay and control center
• Sits on top of brain stem
• Two main parts:
– 1) Thalamus – relay
between sensory
areas and cerebrum
– 2) Hypothalumus –
regulates involuntary
responses & hormone secretions of the
pituitary gland
c. Brain Stem
• Attaches brain to spinal
cord
• Parts of the brain stem
– Midbrain – vision,
hearing, motor control
– Pons – breathing, sleep
– Medulla oblongata involuntary activities
(breathing, heart rate,
blood pressure)
d. Cerebellum
• “Little brain” inferior
to and posterior to
cerebral cortex
• Coordination,
posture, motor
learning
3. Spinal Cord
• Cylinder of nervous
tissue that begins at
base of brain
• Protected by the
vertebral column and
meninges
• Spinal nerves extend
from the cord
through each
vertebrae
• Main communication
link between brain
and the body
4. Traumatic Brain Injuries & Diseases
• Concussion
– Slight or mild brain injury
– Bleeding & tearing of nerve fibers happened
– Recovery likely with some memory loss
• Contusion
– A more severe TBI
– Nervous tissue destruction occurs
– Nervous tissue does not regenerate
• Cerebral edema
– Swelling from the inflammatory response
– May compress and kill brain tissue
• Cerebrovascular Accident (CVA)
– Commonly called a stroke
– The result of a blocked or ruptured
blood vessel supplying a region of
the brain
– Brain tissue supplied with oxygen
from that blood source dies
– Loss of some functions or death may
result
Alzheimer’s Disease
• Progressive degenerative brain
disease
• Mostly seen in the elderly, but may
begin in middle age
• Structural changes in the brain include
abnormal protein deposits and twisted
fibers within neurons
• Victims experience memory loss,
irritability, confusion and ultimately,
hallucinations and death
Peripheral Nervous System (PNS)
Sensory Division
Motor Division
Somatic NS
Autonomic NS
Sympathetic
Parasympathetic
B. Peripheral Nervous System
(PNS)
• Peripheral Nervous System is
made up of all the nerves and
ganglia (nerve cell bodies) that
carry messages between the body
and the CNS
• Receives info from the
environment
• Transmits commands from CNS to
organs and glands
• Contains mostly motor and
sensory neurons
Divisions of the PNS
• Sensory division • Motor division
– transmits
– transmits
impulses from
impulses from
sense organs to
the central
the central
nervous system
nervous system
to the muscles
or glands
– Divided into 2
divisions
• Somatic
• Autonomic
Motor Division
• Somatic N.S.
• Autonomic N.S.
• Regulates activities
that are under
conscious control
• Example: movement of
muscles (wiggle toe)
• Involved in reflexes
(quick, automatic
response to stimulus)
• Regulates activities
that are automatic or
involuntary
• Example: heart rate
• Consists of only motor
nerves
• Divided into two
divisions
– Sympathetic division
– Parasympathetic
division
Autonomic N.S. Division
• Sympathetic
• Parasympathetic
• “Fight-or-Flight”
• Takes over to increase
activities
• Remember as the “E”
division = exercise,
excitement,
emergency, and
embarrassment
• “Rest and Digest
• Conserves energy
• Maintains daily
necessary body
functions
• Remember as the “D”
division = digestion,
defecation, and
diuresis (urination)
Peripheral Nervous System
& Reflexes
• The peripheral nervous system
is also involved in reflexes.
• A reflex is a quick and
unconscious response to a
stimulus
• The brain is not involved with
reflexes.
• The impulse travels up sensory
neurons, to the spinal cord
(interneuron), then immediately
travels down motor neurons for a
response.
• The pathway the impulse travels is
called the reflex arc
Reflex Arc
• Receptor (sense organ)  sensory neuron 
spinal cord  motor neuron  effector (muscle)
Internal Communication
• Internal communication is critical
to maintain homeostasis.
• Sensory neurons are constantly
sending information to the brain
about the internal environment.
• The brain responds by sending
signals through the motor neurons
to maintain homeostasis.
The Nervous System
CNS
Brain
Spinal
Cord
PNS
Somatic NS
Voluntary
Movement
Autonomic NS
Involuntary
Movement
Sympathetic
Parasympathetic
NS
NS
fight or flight
rest & digest
Reflex Pathway
• Sensory input >
– Sensory Neuron >
• Spine (Interneuron) >
–Motor neuron
»> Involuntary Reflex
(response)
Conscious Response
Pathway
• Sensory Input >
– Sensory Neuron >
• Brain (Interneurons) >
–Motor Neuron >
»Voluntary Movement
(Response)