Download Nervous System

Nervous System
Page 203
Nervous System
• Directs the functions of all human body systems
• 100 billion nerve cells
• Divided into two sections
▫ Central Nervous System
▫ Peripheral Nervous System
 Somatic
 Autonomic
Neurons
• Contain 3 parts
▫ Cell body
▫ Dendrites
▫ Axon
 Covered by ‘Myelin Sheath’
• Two basic properties
▫ Excitability – the ability to respond to a stimulus
▫ Conductivity – the ability to transmit a signal
Neuroglias
• Cells in the nervous system
▫
▫
▫
▫
Support
Connect
Protect
Remove
 Debris from the nervous system
• Do NOT transmit impulses
• Form “blood-brain barrier”
Central Nervous System
▫ Composed of brain and spinal cord
▫ Brain has 4 major divisions




Brainstem
Cerebellum
Cerebrum
Diencephalon
Brainstem
• Midbrain
▫ Visual reflexes
• Pons
▫ Controls respiratory functions
• Medulla oblongata
▫ Regulate heart and lung functions
▫ Swallowing, vomiting, coughing, sneezing
Cerebellum
• Coordinates musculoskeletal movement to
maintain posture, balance, and muscle tone
Cerebrum
• Cerebral cortex
▫ Decision making
• Frontal lobe
▫ Voluntary motor movements
▫ Emotional expression
▫ Moral behavior
• Parietal lobe
▫ Controls and interprets the senses and tastes
• Temporal lobe
▫ Controls memory, equilibrium, emotion, and hearing
• Occipital lobe
▫ Controls vision and various forms of expression
Diencephalon
• Contains
▫ Thalamus
▫ Hypothalamus
• Serves as relay center for sensations
• Works with the Autonomic nervous system to
control heart rate, blood pressure, temperature,
electrolyte balance, digestive functions,
behavioral responses, and glandular activities
Central Nervous System
• Cerebrospinal fluid (CSF)
▫ Watery fluid- flows in and around brain and spinal
cord
▫ Cradles and cushions the brain
• Spinal cord
▫ Extends from the base of the brain – L1
Meninges
• Three layers of membranes that cover the brain
and spinal cord
▫ Dura mater
 Tough, fibrous membrane that contains channels for
blood to enter brain tissue
▫ Arachnoid membrane
 Weblike structure that runs across the space
containing CSF
▫ Pia mater
 Innermost layer, a thin membrane containing many
blood vessels that nourish the spinal cord
Peripheral Nervous System
• 12 pairs of cranial nerves
▫ Carry impulses to and from the brain
• 31 pairs of spinal nerves
▫ Carry messages to and from the spinal cord and
extremities of the body
• Somatic Nervous System
• Autonomic Nervous System
Somatic Nervous System
• Receive and process sensory
input from
▫
▫
▫
▫
▫
▫
▫
Skin
Muscles
Tendons
Joints
Eyes
Nose
Ears
• Excite the voluntary contraction
of skeletal muscles
Autonomic Nervous System
• Carry impulses from the central nervous system
to
▫ Glands
▫ Involuntary muscles
▫ Cardiac muscle
• Sympathetic
▫ Operates when the body is under stress
• Parasympathetic
▫ Operates to keep the body in homeostasis