Divisions of the Divisions of the Nervous System Nervous System Chapter 7
Jan 19, 2018
Divisions of the Divisions of the Nervous SystemNervous System
Chapter 7
Divisions of the Nervous Divisions of the Nervous SystemSystem
• 2 major divisions:
Nervous System
Central Nervous System
Peripheral Nervous System
BrainSpinal Cord
Nerve cells
A. The Central Nervous System (CNS)• Control center of the
body• Relays messages,
processes & analyzes information
• Made of two parts:– BrainBrain– Spinal cordSpinal cord
• 1. The Brain1. 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 a. Cerebral Hemispheres (Cerebrum)(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 Fissures (deep grooves) (deep grooves) divide the cerebrum divide the cerebrum into four lobesinto four lobes
1.1. Occipital LobeOccipital Lobe: visual integration
2.2. ParietalParietal: spatial knowledge, math
3.3. TemporalTemporal: memories, auditory, language
4.4. FrontalFrontal: 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)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 Peripheral Nervous System (PNS)(PNS)
Sensory Division Motor Division
Somatic NS Autonomic NS
Sympathetic Parasympathetic
B. Peripheral Nervous System B. Peripheral Nervous System (PNS)(PNS)
• Peripheral Nervous System 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 Contains mostly motor and sensory neuronssensory neurons
Divisions of the PNSDivisions of the PNS•Sensory
division –transmits impulses from sense organs to the central nervous system
•Motor division –transmits impulses from the central nervous system to the muscles or glands
–Divided into 2 divisions•Somatic•Autonomic
Motor DivisionMotor Division•Somatic N.S.• Regulates activities
that are under conscious control
• Example: movement of muscles (wiggle toe)
• Involved in reflexes (quick, automatic response to stimulus)
•Autonomic N.S.• 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. DivisionAutonomic N.S. Division•Sympathetic• “Fight-or-Flight”• Takes over to
increase activities• Remember as the
“E” division = exercise, excitement, emergency, and embarrassment
•Parasympathetic
• “Rest and Digest• Conserves energy• Maintains daily
necessary body functions
• Remember as the “D” division = digestion, defecation, and diuresis (urination)
Peripheral Nervous Peripheral Nervous System & ReflexesSystem & 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 ArcReflex Arc
• Receptor (sense organ) sensory neuron spinal cord motor neuron effector (muscle)
Internal CommunicationInternal 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 SystemThe Nervous System
PNSPNSCNSCNS
Somatic NSSomatic NSVoluntary Movement
Autonomic NSAutonomic NSInvoluntary Movement
Sympathetic Sympathetic NSNS
fight or flight
ParasympatheParasympatheticticNSNS
rest & digest
BrainBrain Spinal Spinal CordCord