The Nervous System
Functions
• Reception• Interpretation• Integration• Control of homeostasis• Mental Acuity• Control of Muscle and Glands
Anatomic Divisions of the Nervous System
The Central Nervous System Brain and Spinal Cord
The Peripheral Nervous System Nerves and Ganglia
Physiologic Divisions of the Peripheral Nervous System 1. Sensory- (Afferent) carries messages to the CNS
2. Motor- (Efferent) Somatic- Carries messages away from the CNS,
from the brain to the skeletal muscle. This is voluntary action
Autonomic –Controls cardiac muscle, smooth muscle and glands and is under involuntary control
Enteric- associated with digestive tract
The Nervous System Cell• The neuron Consists of a cell body,
dendrites and axons They receive the stimuli and
transmit the action potential
The Electrical Impulse
Resting Membrane PotentialAction PotentialThe SynapseReflexes
The Nervous System Tissue
• Neuron• Neuroglia- support cells• Myelin Sheaths – axon is either
myelinated or unmyelinated• White matter and Gray Matter- Gray- cortex and nuclei in the brain
and ganglia of PNS White_ nerve tracts in CNS and
nerves in PNS
The Neuralgia
The Brain Divisions
Cerebrum Diencephalon Cerebellum Brainstem
The Brain Division
• Cerebrum- Consists of Two Hemispheres Hemispheres are Subdivided
into Lobes Frontal Parietal Occipital Temporal
The Hemispheres of the cerebrum • Each hemisphere controls the
opposite half of the body• Commissures connect the two
hemispheres• The left hemisphere dominates in
analytical skills , the right dominates for spatial perception and musical ability
Divisions of the Brain
• Diencephalon Thalmus- main sensory
relay center Epithalmus- pineal gland Hypothalamus- maintains homeostasis
Brain divisions
• Cerebellum- in back attached to the brainstem
Cerebellum
• The Cerebellum is involved in balance and muscle coordination.
• An important function of the cerebellum is to compare the intended action with what is occurring and modify it
• If damage to the cerebellum, there is a decrease in muscle tone and, balance
Division of Brain Brainstem- Ascending and descending tracts
Divisions: Medulla Oblongata- heart rate , breathing, swallowing and
balance
Pons- relay nuclei between cerebrum and cerebellum
Midbrain- involved in visual and hearing reflexes
Reticular formation- maintains consciousness and sleep wake cycles
BRAINSTEM
The Twelve Cranial Nerves
I Olfactory II Optic III Oculomotor IV Trochlear V Trigeminal VI Abducens VII Facial VIII Vestibulocohlear IX Glossopharyngeal X Vagus XI Accessory XII Hypoglossal
The Cranial Nerves – nerves coming right off the brain
• There are twelve Cranial Nerves• 3 are sensory• 4 are motor• 1 both motor and sensory• 1 somatic motor and
parasympathetic• 3 with all three functions• 4 are parasympathetic
The Meninges or Coverings
• The Central Nervous System is covered by three protective layers:
• Dura Matter• Arachnoid Matter• Pia Matter
The Ventricles
• In the brain and spinal cord there are fluid filled cavities :
• lateral ventricle • third ventricle • cerebral aqueduct • fourth ventricle• central canal
The Cerebrospinal Fluid
• The Cerebrospinal Fluid is formed in the ventricles
• How does it circulate?• It is made by the choroid plexus then
exists through the fourth ventricle and it reenters the blood through the arachnoid granulations in the superior sagital sinus
The Spinal Cord
• Extends from the foramen magnum to the second lumbar vertebrae after which it is called the cauda equina
• Central part is Gray matter and the Peripheral part is White Matter forming the nerve tracts
• Roots of the Spinal Nerves Extend out of the cord
Spinal Nerves: 31 pairs of Spinal Nerves• Exit from the cervical, thoracic, and sacral regions
The nerves are grouped into Plexuses Cervical Plexus- contains Phrenic Nerve Brachial Plexus- nerves to upper limb Lumbosacral Plexus- nerves to the lower limb
How do we sense
Ascending Tracts transmit the action potential from
the periphery to the brain each tract contains a specific type
of sensory information• Project to the primary area of the
cerebral cortex
Ascending Tracts
• Spinothalmic- pain temp, light touch tickle itch
• Dorsal Column proprioception, deep pressure and vibration
• Spinocerebellar- proprioception to the cerebellum
How do we respond
Descending Tracts• Upper motor neurons in the cerebral
cortex connect to the lower motor neurons in the spinal cord, brainstem and cerebellum and send out a specific motor response
Descending Tracts for movement Table 8.5
• Direct lateral corticospinal anterior corticospinal Indirect Rubrospinal reticulospinal vestibulospinal
Ascending Descending
Simple Reflex
Autonomic Nervous System
• Divided into Sympathetic N.S. Parasympathetic N.S. Enteric N.S.
Sympathetic N.S.
• Prepares person for action by increasing heart rate, blood pressure and respiration rate. “The Fight or Flight Response”
• Associated with the thoracic and lumbar nerves ( T1- L2)
Parasympathetic N.S.
• Involved in vegetative activities such as digestion of food, defecation and urination. Slows heart rate and respiration
• Located in cranialnervesIII,VII,IX, X and sacral nerves S2-S4
Enteric N.S.
• Associated with the digestive tract
Neurotransmitters
• Acetylcholine-
• Norepinephrine-
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