A View of Life

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Nervous System- Chapters 7, 8
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Surgical Papyrus

• Egyptian hieroglyphics.
• 17th Century B.C.
• Oldest known surgical treatise.
• 48 case histories are outlined.

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Organization of the Nervous System

• Consists of two divisions
• Central Nervous System (CNS).
• Brain and spinal cord.
• Peripheral Nervous System (PNS).
• All nervous tissue outside the
  CNS.

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• 1) Nervous tissue consists of _________ and
  ____________.
• A) neurons and ganglia
• B) neurons and meninges
• C) neurons and neuroglia
• D) neurons and nerves
• E) morons and gangly ganglia

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Nervous System

• Neurology- (neur- gr. nerve) the scientific study
  of the nervous system.
• Nervous Tissue
• Neurons (nerve cells)
• Neuroglia

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Neurons

• Neuron- the functional unit of the nervous
  system.
• Numbers
• 100 billion in the brain.
• 1 billion in the spinal cord.
• Neurons consist of dendrites, cell bodies, and
  axons.

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Dendrites
Synaptic end bulbs
Axon terminal
Nucleus
Cell Body
Nodes of Ranvier
Axon
Myelin Sheath
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Functional Classification of Neurons

• Based on the direction the neurons transmit nerve
  impulses.
• Sensory neurons
• Transmit nerve impulses from receptors in the
  skin, sense organs, muscles, joints, and organs
  toward the spinal cord and brain.
• Interneurons
• Transmit nerve impulses from one neuron to
  another.
• Motor neurons
• Transmit nerve impulses away from the spinal cord
  to muscles or glands.

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Types of Neurons
Dorsal-Root Ganglion
Sensory Receptor
Interneuron
Ventral-Root Ganglion
Effector
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Nervous System Functions

• Sensory
• Detecting internal and external stimuli.
• Sensory receptors and sensory neurons
• Integrative
• Processing sensory information by analyzing,
  storing, and making decisions regarding
  appropriate responses.
• Interneurons
• Motor
• Responding to integration decisions.
• Motor neurons

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Neuroglial Cells

• Neuroglia (glia gr. glue).
• Half the volume of the CNS.
• Smaller than neurons.
• 50X more numerous.
• Functions
• Support and protect the neurons.
• Maintain homeostasis in the fluid that bathes
  neurons.
• 6 types of neuroglia.

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• Which of the following is not considered a
  nervous system structure?
• A) spinal cord
• B) Jeffs brain
• C) ganglia
• D) heart
• E) enteric plexus
• F) sensory receptors

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Nervous System Structures

• Brain
• 12 pairs of cranial nerves and their branches.
• Spinal cord
• 31 pairs of spinal nerves and their branches.
• Ganglia- clusters of cell bodies in the
  peripheral nervous system.
• Enteric plexus- a network of nerves in the GI
  tract.
• Sensory receptors- parts of neurons or
  specialized cells that monitor changes in the
  internal or external environment.

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What is a nerve?

• Nerve- a bundle of long axons outside the central
  nervous system.

Axon
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Lining the Brain Spinal Cord Meninges

• Meninges- 3 layers of protective tissue lining
  the brain and spinal cord.
• Dura Mater
• Arachnoid Mater
• Pia Mater
• The spaces between the meninges are filled with
  cerebral spinal fluid.

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Gray and White Matter

• White matter- aggregations of myelinated
  processes.
• Gray matter- nerve fibers with little to no
  myelin.

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The Brain

• One of the largest organs in the body, 3 lbs.
• Average length- 7 inches, width- 5.5, height- 4.
• Center for registering sensations, correlating
  them with one another and with stored
  information.
• Center for intellect, emotions, behavior, and
  memory.
• Chemistry- 78 H2O, 12 lipids, 8 protein, 2
  other.
• Consists of four principal parts
• Cerebrum
• Cerebellum
• Diencephalon
• Brain stem

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4 Principal Parts of the Brain
Thalamus
Hypothalamus
Midbrain
Pons
Medulla Oblongata
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The Cerebrum

• The cerebrum is the largest portion of the human
  brain.
• Communicates with and coordinates activities of
  other parts of the brain.
• Divided into left and right cerebral hemispheres.
• The outer layer is termed the cerebral cortex.

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Lobes of Cerebrum
Sensory
Motor
Visual
Auditory
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• True or False
• If you eat right hemispheric sheep brains
  biweekly, while watching the movie The Man With
  Two Brains, you will be more creative than
  someone who eats left hemispheric brains and
  watches the movie The Wedding Crashers.

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Hemispheric Lateralization
Verbal Logical Analytical Rational
Nonverbal Intuitive Creative
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Higher Mental Functions

• Memory is the ability to hold a thought in the
  mind or to recall events from the past.
• Short-term- prefrontal lobe.
• Long-term- hippocampus.
• Amygdala- adds emotional overtones to memories.

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Limbic System- long-term memory
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Brain Stem

• Functions
• Acts as a relay station between the cerebrum and
  the spinal cord and cerebellum.
• Reflex center for visual, auditory, and tactile
  responses.

Midbrain
Pons
Medulla Oblongata
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Cerebellum

• Functions
• Acts as an integration center for sensory input
  from the eyes, ears, joints, and muscles that
  relates to body position.
• Sends motor impulses to skeletal muscles that
  maintain posture and balance.

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Diencephalon

• Consists of the hypothalamus and thalamus.
• Functions
• Homeostasis for hunger, sleep, temp, water
  balance.
• Receiving center for all sensory input, except
  smell.
• Plays a role in memory and emotions.

Thalamus
Hypothalamus
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Alzheimers Disease

• Presence of abnormal neurons in the brain.
• Amyloid plaque envelopes axons.
• Tangled axons (neurofibrillary tangles).
• 5 of adults 65-74 years in age. 50 of those 85
  and over.
• Appears to be partly genetic, APOE4.

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Parkinsons Disease

• Characterized by trembling or shaking.
• Due to the degeneration of dopamine-releasing
  neurons in the brain.
• The lack of dopamine results in the sending out
  of excess signals to effectors (muscles).
• 1 of those over the age of 60.
• Treatment is with L-dopa.

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Cranial and Spinal Nerves
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Spinal Cord

• Anatomy
• Flattened cylinder, 16-18 inches in length and
  3/4 inch diameter.
• In adult ends at L2.
• Functions
• Provides communication between the brain and the
  peripheral nerves.
• Spinal cord reflexes.

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Spinal Nerve
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Peripheral Nervous System (PNS)

• Somatic Nervous System (somat-body)
• Neurons that conduct impulses from somatic and
  special sense receptors to the CNS.
• Enteric Nervous System (enter-intestines)
• Two plexuses that extend the length of the
  gastrointestinal tract.
• Autonomic Nervous System (auto-self, nomic-law)
• Motor neurons that convey impulses from the CNS
  to smooth muscle tissue, to cardiac tissue, and
  to glands.

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Somatic vs. Autonomic

• The ANS pathway is a 2 neuron pathway, while the
  SNS is a 1 neuron pathway.

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Divisions of the ANS
Sympathetic
Parasympathetic

• 2 Major Divisions
• Sympathetic
• Speeds up the visceral effector.
• Parasympathetic
• Slows down the visceral effector.
• Most body organs receive dual innervation.
• Hypothalamus regulates balance between these two
  divisions.

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Sympathetic Responses

• The sympathetic system dominates during physical
  or emotional stress conditions.
• E situations- emergency, embarrassment,
  excitement, exercise.
• Alarm reaction- flight or fight response.
• Dilation of pupils.
• Increase of heart rate and blood flow to muscles.
• Decrease in blood flow to nonessential organs.
• Increase in blood flow to skeletal and cardiac
  muscles.
• Airways dilate and respiratory rate increases.
• Blood glucose level increases.
• Decrease in intestinal activity and inhibition of
  urination.
• Causes genital erection.

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Parasympathetic Responses

• Rest-and-digest activities.
• Mechanisms that help conserve and restore body
  energy during times of rest.
• SLUDD responses
• Salivation
• Lacrimation
• Urination
• Digestion
• Defecation
• 3 decreases- decreased
• Heart rate, diameter of airways, and diameter of
  pupils.

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Development of the Nervous System

• Appears around 3-4 weeks.