Exploring the Nervous System

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Chapter 2

• Exploring the Nervous System

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Anatomical Views

• Horizontal section - Shows structures viewed from
  above
• Sagittal section - Divides structures into right
  and left parts
• Coronal section - Shows views from the front

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Anatomical Directions

• Anatomical directions are used for locating
  structures with the body
• Anterior - toward the front
• Posterior - toward the rear
• Ventral - toward the belly
• Dorsal - toward the back
• Rostral - toward the head
• Caudal - toward the tail
• Medial - toward the midline
• Lateral - away from the midline
• Superior - above a structure
• Inferior - below a structure

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The Importance of the Nervous System

1. Detect stimuli in the environment
2. Determine the significance of the environmental
   stimuli
3. Make a decision based on the stimuli
4. Execute a response

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Organization of the Nervous SystemTwo Major
Divisions

• Peripheral Nervous System (PNS)
• Detects environmental information inside and
  outside the body, which is transmitted to the CNS
  
• Executes responses to stimuli
• Central Nervous System (CNS)
• Recognizes and analyzes information from the PNS
• Makes and transmits decisions to glands, organs,
  and muscles for execution

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Cells of the Nervous System

• Nerve cells neurons perform the information
  processing and communication functions of the
  nervous system
• Glial cells - supportive cells in the nervous
  system. The glial cells surround neurons and
  provide support for and insulation between them. 

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Cells of the Nervous System Neurons

• Perform information processing
• and communications functions
• of the nervous system
• Consist of three major parts
• Soma - contains nucleus, mitochondria, and
  ribosomes
• Dendrites - portions of the neuron that transmit
  information toward the cell body
• Axon - a structure on the neuron which transmits
  information away from the cell body

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Cells of the Nervous SystemTerminology

• Groups of neurons form four functional groups
• A collection of axons
• Nerve in the Peripheral Nervous System (PNS)
• Tract in the Central Nervous System (CNS)

• A collection of cell bodies
• Ganglion within the PNS
• Nucleus - within the CNS

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Cells of the Nervous SystemFunctional Types of
Neurons

• Sensory neurons - carry information to the CNS
• Interneurons - connect sensory and motor neurons
  or communicate with other interneurons
• Motor neurons - carry information from the CNS to
  muscles, organs, and glands to control their
  functioning.

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PhysicalTypes ofNeurons
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Cells of the Nervous SystemTypes of Synapses

• Axodendritic - the axon synapses with dendrites
  of another neuron
• Axosomatic - the axon synapses with the cell body
  of another neuron
• Dendrodendritic synapse - occurs when the
  dendrites of one neuron synapses with the
  dendrites of another neuron
• Axoaxonic synapse - the axon of one neuron
  synapses with the axon of another neuron
• Neuromuscular junction - the axon synapses with a
  muscle

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Cells of the Nervous SystemGlial Cells

• Glial cells
• One-tenth the size of neurons
• Ten times as numerous as neurons
• Types of Glial cells
• Astrocytes - provide physical support to neurons,
  nourishment and other functions.
• Microglial cells - remove debris
• Oligodendrocytes - produce myelin which covers
  the axons of neurons in CNS
• Schwann cells - produce myelin which covers the
  axons of neurons in PNS

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Myelination
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Organization of the Nervous SystemThe
Peripheral Nervous System

• Detects internal and external environmental
  information relays information to CNS
• Executes CNS decisions in muscles, glands and
  organs
• Spinal nerves and Cranial nerves
• Peripheral Nervous System includes
• Somatic Nervous System - Includes both sensory
  and motor systems
• Autonomic Nervous System - Regulates the internal
  environment

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The Peripheral Nervous System Somatic Nervous
System

• Enables us to interact with the physical
  environment
• Afferent neurons transmit messages from sensory
  receptors to the CNS
• Efferent neurons transmit messages from the CNS
  to skeletal muscle
• Spinal nerves 31 pairs of nerves that send
  messages to/from the brain thru the spinal cord
• Cranial nerves 12 pairs of nerves that link
  sensory receptors in the head directly to the
  brain and the brain to certain muscles

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Cranial Nerves
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The Peripheral Nervous SystemAutonomic Nervous
System

• Primarily efferent neurons
• Controls internal environment - glands and
  internal organs
• Consist of two parts that are typically
  antagonistic
• Sympathetic
• Parasympathetic

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The Autonomic Nervous System
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Organization of the Nervous SystemThe Central
Nervous System

• Recognizes and analyzes information received from
  the PNS
• Makes and transmits decisions to glands, organs,
  and muscles for execution
• Central Nervous System includes
• Spinal cord - responsible for limited analysis
  and decision making, transmits information to and
  from the brain.
• Brain - responsible for analyzing sensory
  information and making appropriate responses to
  it.

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The Protective Features of the Central Nervous
System

• Protecting the spinal cord
• Vertebral Column - outer bony covering that
  encases the spinal cord
• Protecting the brain
• Skull - outer bony covering that encases the
  brain
• Ventricular system
• Meninges protects both
• Dura matter
• Arachnoid matter
• Pia mater

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The Central Nervous System Spinal Cord

• Serves as a conduit to and from
• the brain
• Controls spinal reflexes

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The Central Nervous System The Brain

• Three main functions
• Recognizing stimuli detected by the PNS
• Analyzing the information
• Initiating the appropriate response
• Three main areas
• Hindbrain
• Midbrain
• Forebrain

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The Brain The Hindbrain

• Myelencephalon
• Medulla oblongata, which controls basic life
  functions
• Metencephalon
• Pons - a bridge for fibers passing from one
  side of the brain to the other. Sensory fibers,
  fibers from the cortex to cerebellum, and fibers
  that relay information on sleep, arousal and
  dreaming pass through it.
• Cerebellum - involved in the development and
  coordination of movement
• Reticular formation
• Involved in arousal, begins in the medulla and
  extends to other areas of the brain

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The Hindbrain
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The Brain The Midbrain

• Mesencephalon
• Tectum - relays visual and auditory information
  and controls simple reflexes, eye and ear
  orientation movements
• Tegmentum -
• substantia nigra - integration of voluntary
  movements
• red nucleus - controls basic body movements
• reticular formation - controls arousal and
  consciousness
• Brain stem midbrain hindbrain not including
  the cerebellum

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The Brain Forebrain

• Diencephalon
• Epithalamus - contains habenula (olfactory
  functions) and pineal gland
• Thalamus - major relay station for sensory
  information
• Hypothalamus - detects need states, controls the
  autonomic nervous system, and controls pituitary
  hormone production and release
• Pituitary - regulates other glandular activity
  of the body often called the master gland

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The Diencephalon
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The Brain Forebrain

• Telencephalon
• Limbic System
• The limbic system is a group of structures
  surrounding the brain stem.
• The limbic system structures include the
  amygdala, cingulate gyrus, and hippocampus.
• Governs emotions such as anger, fear, and
  happiness, and is involved in the storage and
  retrieval of memories.

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The Limbic System
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The Brain Forebrain

• Telencephalon
• Basal Ganglia - have widespread connections to
  the cortex and forebrain and are involved in the
  initiation of voluntary movements, maintaining
  muscle tone and posture

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The Brain Forebrain

• Telencephalon
• Cerebral Cortex - the convoluted outer layer of
  the forebrain that processes sensory information,
  controls thinking, decision making, stores and
  retrieves memory, and initiates motor responses
• The cortex is divided into two hemispheres
  connected by the corpus callosum and each
  hemisphere has four lobes

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The Cerebral Cortex
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The Brain Lobes of the Cerebral Cortex

• Occipital lobe - primary function is the analysis
  of visual information
• Parietal lobe - The anterior portion analyses
  sensory information such as pain, pressure and
  body position. The posterior portion is involved
  in spatial perception.
• Temporal lobe - includes the primary auditory
  cortex, a visual area and language centers

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The Brain Lobes of the Cerebral Cortex

• Frontal lobe -
• Brocas area - area for programming and
  sequencing of motor movements for speech
  production
• Prefrontal cortex - controls complex intellectual
  functioning such as planning and sequencing of
  behavior.
• Motor cortex - area of the frontal lobe anterior
  to the central sulcus.

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Representation of body parts in the somatosensory
cortex and motor cortex