The Nervous System

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The Nervous System
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The Reflex Arc

• Reflexrapid, predictable, and involuntary
  response to a stimulus
• Occurs over pathways called reflex arcs
• Reflex arcdirect route from a sensory neuron, to
  an interneuron, to an effector

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The Reflex Arc
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The Reflex Arc
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The Reflex Arc
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The Reflex Arc
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The Reflex Arc
Figure 7.11a, step 4
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The Reflex Arc
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Simple Reflex Arc
Sensory receptors(stretch receptorsin the
quadricepsmuscle)
Sensory receptors(pain receptors inthe skin)
Sensory (afferent)neuron
Spinal cord
Sensory (afferent)neuron
Synapse inventral horngray matter
Inter-neuron
Motor(efferent)neuron
Motor(efferent)neuron
Effector(quadricepsmuscle ofthigh)
Effector(bicepsbrachiimuscle)
(b)
(c)
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Sensory receptors(stretch receptorsin the
quadricepsmuscle)
Spinal cord
(b)
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Sensory receptors(stretch receptorsin the
quadricepsmuscle)
Sensory (afferent)neuron
Spinal cord
(b)
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Sensory receptors(stretch receptorsin the
quadricepsmuscle)
Sensory (afferent)neuron
Spinal cord
Synapse inventral horngray matter
(b)
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Sensory receptors(stretch receptorsin the
quadricepsmuscle)
Sensory (afferent)neuron
Spinal cord
Synapse inventral horngray matter
Motor(efferent)neuron
(b)
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Sensory receptors(stretch receptorsin the
quadricepsmuscle)
Sensory (afferent)neuron
Spinal cord
Synapse inventral horngray matter
Motor(efferent)neuron
Effector(quadricepsmuscle ofthigh)
(b)
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Sensory receptors(pain receptors inthe skin)
Spinal cord
(c)
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Sensory receptors(pain receptors inthe skin)
Spinal cord
Sensory (afferent)neuron
(c)
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Sensory receptors(pain receptors inthe skin)
Spinal cord
Sensory (afferent)neuron
Inter-neuron
(c)
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Sensory receptors(pain receptors inthe skin)
Spinal cord
Sensory (afferent)neuron
Inter-neuron
Motor(efferent)neuron
(c)
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Sensory receptors(pain receptors inthe skin)
Spinal cord
Sensory (afferent)neuron
Inter-neuron
Motor(efferent)neuron
Effector(bicepsbrachiimuscle)
(c)
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Sensory receptors(stretch receptorsin the
quadricepsmuscle)
Sensory receptors(pain receptors inthe skin)
Sensory (afferent)neuron
Spinal cord
Sensory (afferent)neuron
Synapse inventral horngray matter
Inter-neuron
Motor(efferent)neuron
Motor(efferent)neuron
Effector(quadricepsmuscle ofthigh)
Effector(bicepsbrachiimuscle)
(b)
(c)
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Types of Reflexes and Regulation

• Somatic reflexes
• Activation of skeletal muscles
• Example When you move your hand away from a hot
  stove

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Types of Reflexes and Regulation

• Autonomic reflexes
• Smooth muscle regulation
• Heart and blood pressure regulation
• Regulation of glands
• Digestive system regulation

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Types of Reflexes and Regulation

• Patellar, or knee-jerk, reflex is an example of a
  two-neuron reflex arc

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Central Nervous System (CNS)

• Ventricles
• Four chambers within the brain
• Filled with cerebrospinal fluid

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Regions of the Brain

• Cerebral hemispheres (cerebrum)
• Diencephalon
• Brain stem
• Cerebellum

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Cerebrum
Figure 7.14
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Regions of the Brain Cerebrum

• Cerebral areas involved in special senses
• Gustatory area (taste)
• Visual area
• Auditory area
• Olfactory area

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Regions of the Brain Cerebrum
Figure 7.13c
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Cerebrum

• Layers of the cerebrum
• Gray matterouter layer in the cerebral cortex
  composed mostly of neuron cell bodies
• White matterfiber tracts deep to the gray matter
• Corpus callosum connects hemispheres
• Basal nucleiislands of gray matter buried within
  the white matter

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Cerebrum
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Regions of the Brain Diencephalon
Figure 7.16
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Diencephalon (Interbrain)

• On top of the brain stem
• Enclosed by the cerebral hemispheres
• Made of three parts
• Thalamus
• Hypothalamus
• Epithalamus

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Diencephalon
Figure 7.12b
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Diencephalon
Figure 7.16a
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Diencephalon
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Diencephalon

• Thalamus
• The relay station for sensory impulses
• Pleasant vs. unpleasant
• Transfers impulses to the sensory cortex

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Diencephalon

• Hypothalamus
• Important autonomic nervous system center
• Regulate body temperature
• Controls water balance
• Regulates metabolism

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Diencephalon

• Hypothalamus (continued)
• An important part of the limbic system (emotions)
• The pituitary gland is attached to the
  hypothalamus

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Diencephalon

• Epithalamus
• Forms the roof of the third ventricle
• Houses the pineal body (an endocrine gland)
• Choroid plexusforms cerebrospinal fluid

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Brain Stem

• Attaches to the spinal cord
• Parts of the brain stem
• Midbrain
• Pons
• Medulla oblongata

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Brain Stem
Figure 7.16a
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Brain Stem

• Midbrain
• Mostly composed of tracts of nerve fibers
• Has two bulging fiber tractscerebral peduncles
• Has four rounded protrusionscorpora
  quadrigemina
• Reflex centers for vision and hearing

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Brain Stem

• Pons
• The bulging center part of the brain stem
• Mostly composed of fiber tracts
• Includes nuclei involved in the control of
  breathing

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Brain Stem

• Medulla Oblongata
• The lowest part of the brain stem
• Merges into the spinal cord
• Includes important fiber tracts
• Contains important control centers
• Heart rate control
• Blood pressure regulation
• Breathing
• Swallowing
• Vomiting

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Regions of the Brain Brain Stem

• Reticular Formation
• Diffuse mass of gray matter along the brain stem
• Involved in motor control of visceral organs
• Reticular activating system (RAS) plays a role in
  awake/sleep cycles and consciousness

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RETICULAR FORMATION OF THE BRAIN STEM
Figure 7.16b