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The Nervous System and Nervous Tissue. Chapter 11. Functions of the Nervous System. Uses its millions of sensory receptors to monitor changes occurring both inside and outside the body. This gathered information is called sensory input.

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Functions of the Nervous System

  • Uses its millions of sensory receptors to monitor changes occurring both inside and outside the body. This gathered information is called sensory input.
  • Processes and interprets sensory input and decides what should be done at each moment- a process called integration.
  • Causes a response, called motor output, by activating effector organs.
divisions of the nervous system
Divisions of the Nervous System
  • Central Nervous System (CNS)
    • Brain and Spinal Cord
  • Peripheral Nervous System (PNS)
    • Sensory (afferent) division
    • Motor (efferent) division
      • Somatic Nervous System
      • Autonomic Nervous System (ANS)
        • Sympathetic division
        • Parasympathetic division

Functions of the Divisions

Nervous System Quiz


Histology of Nervous Tissue

  • Nervous tissue is made up of two types of cells
    • Supporting cells- Surround the wrap the neurons
    • Neurons- excitable nerve cells that transmit electrical signals

Neuroglia (Glial Cells)

  • Central Nervous System Glial Cells
    • Astrocytes
      • Most abundant
      • Anchor neurons to blood vessels
      • Regulate transport of nutrients and wastes to and from neurons
    • Microglia
      • Phagocytic to defend against pathogens
      • Protect and monitor health of neurons

Neuroglia (Glial Cells)

  • Central Nervous System Glial Cells
    • Ependymal cells
      • Line the fluid-filled cavities of the brain and spinal cord
      • Play a role in production, transport, and circulation of the cerebrospinal fluid
    • Oligodendrocytes
      • Produces myelin sheath which insulates and protects axons


Neuroglia (Glial Cells)

  • Peripheral Nervous System Glial Cells
    • Satellite Cells
      • Surround neuron cell bodies
    • Schwann Cells
      • Surround and form myelin sheaths around the larger nerves in the PNS
      • Function is similar to oligodendrocytes


  • Nerve cells that are the structural units of the nervous system
  • Conduct messages in the form of nerve impulses from one part of the body to another
  • More special characteristics:
    • Have extreme longevity
    • Amitotic- lose their ability to divide
    • High metabolic rate

Neuron Structure

  • Composed of:
    • Cell Body- Part that contains the nucleus
    • Dendrites- Carries a nerve impulse towards the cell body
    • Axons- Carries a nerve impulse away from the cell body and toward the dendrite of the next neuron
      • Myelin sheath- protects and electrically insulates fibers; increases speed of nerve impulse transmission


Neuron Classification

  • Structural Classification
    • Multipolar= have 3 or more processes. Most common neuron type (more than 99% of neurons)
    • Bipolar= have two processes: an axon and a dendrite. Only found in some special sense organs
    • Unipolar=Single short process that emerges from cell body in PNS

Neuron Classification

  • Functional Classification
    • Groups neurons according to the direction in which the nerve impulse travels relative to the CNS
    • Sensory
    • Motor
    • Interneuron

Neuron Classification

  • Sensory (afferent)- transmit impulses from sensory receptors in the skin or internal organs toward or into the CNS. Usually unipolar.
  • Motor (efferent)- carry impulses away from the CNS to the effector organs (muscles or glands). Most are multipolar.
  • Interneuron- lie between motor and sensory neurons and shuttle signals through CNS pathways where integration occurs




Other Aspects associated with Neurons

  • Receptors
    • Beginnings of dendrites or sensory neurons
  • Ganglion
    • A group of nerve-cell bodies located in the PNS
  • Effector
    • Muscles or gland that motor neuron axons form a synapse with

Other Aspects associated with Neurons

  • Nerve Impulse (or action potential)
    • An electrochemical charge that travels (about 200 meters per second!) along a nerve fiber.
  • Synapse
    • A gap between an axon of one neuron and the dendrite of another neuron
  • Reflex Arc
    • Type of neuron pathway that allows a nerve impulse to travel in only one direction. EX: Knee jerk



  • Chemical Synapse
    • Release and reception of chemical neurotransmitters
  • Electrical Synapse
    • Less common than chemical
    • Important in CNS arousal from sleep


Glial Cells and their functions

  • Neuron Classification
  • Nerve Cell Quiz
  • Glial Cells
  • Brain Games
  • The Synapse

The Central Nervous System

  • Consists of the brain and spinal cord
  • Command center of the nervous system
  • Interprets sensory input and dictates motor responses


The Brain

  • Composed of four major regions:
    • Cerebral Hemispheres (Cerebrum)
      • Coordinates sensory data and motor functions
      • Governs intelligence, reasoning, and learning
      • Controls skeletal muscle movement
      • Contains the cerebral cortex, where our conscious mind is found and makes up the outer layer of the brain

The Brain

  • Diencephalon
    • Hypothalamus- regulates homeostasis (body temperature, thirst, hunger, blood pressure) and links nervous system to the endocrine system
    • Involved in memory processing and emotions (Limbic system)
  • Brain stem
    • Maintains cerebral alertness and helps regulate skeletal muscle activity
    • Responsible for the most basic functions of life such as breathing and heart rate
    • Consists of:
      • Midbrain, Pons, Medulla oblongata

The Brain

  • Cerebellum
    • Comes from the Latin word for "little brain."
    • Functions for muscle coordination
    • Coordinates balance
    • Long Term Memory

Lobes of the Brain

  • Frontal Lobe- Concerned with reasoning, planning, parts of speech and movement, emotions, and problem-solving
  • Parietal Lobe- Concerned with perception of stimuli related to touch, pressure, temperature, and pain


Lobes of the Brain

  • Temporal Lobe- Concerned with perception and recognition of auditory stimuli (hearing) and memory
  • Occipital Lobe- Concerned with many aspects of vision


Functional Regions of the Cerebral Cortex

  • Sensory Areas
    • Where sensations are perceived
  • Motor Areas
    • Conscious muscle movements
  • Association Areas
    • Near sensory areas which recognize and analyze incoming information

Functional Regions of the Cerebral Cortex

  • Sensory Areas
  • Primary somatic sensory cortex= General sensory input (touch, temperature, pressure, pain) from all parts of the body
  • Gustatory cortex= Located in the parietal lobe; taste sensations are perceived here
  • Auditory cortex= Located in the temporal lobe; auditory stimuli are processed here
  • Visual cortex= Located in the occipital lobe; visual images are perceived here


Functional Regions of the Cerebral Cortex

  • Motor Areas
  • Primary motor cortex= Controls voluntary muscle movements
  • Premotor cortex= Decides which muscle groups will be used and how they will be used prior to stimulating the primary motor cortex
  • Motor speech area (Broca’s area)= Controls and coordinates the muscles involved in normal, fluent speech
  • Frontal eye field= Controls muscle movements of the eye


Functional Regions of the Cerebral Cortex

  • Association Areas
  • Prefrontal area= Most highly developed in humans since it regulates emotional behavior and mood. Also is involved in planning, learning, reasoning, personality, motivation, and intellect
  • Somatic sensory association area= Area that allows you to predict that sandpaper is rough even without looking at it. Stores memories about previous sensory experiences.

Functional Regions of the Cerebral Cortex

  • Association Areas
  • Sensory speech area (Wernicke’s area)= Important in language development
  • Auditory association area= Allows us to comprehend, interpret, analyze, and question what we are hearing.
  • Visual association area= Allows us to connect the words to what we see (the image)

Protection of the Brain:


  • Three sheets of connective tissue
  • From superficial to deep:
    • Dura mater- pressed against the bony surface of the cranium
    • Arachnoid- forms a web-like, loose brain covering
    • Pia mater- composed of tiny blood vessels and clings tightly to the brain
  • Cerebrospinal Fluid (CSF)= region between the arachnoid and pia mater



The Spinal Cord

  • A long, thin, tubular bundle of nervous tissue and support cells that extends from the brain (the medulla specifically).
  • Conducts sensory information from the PNS (both somatic and autonomic) to the brain


The Spinal Cord

  • Conducts motor information from the brain to our various effectors (muscles and glands)
  • Serves as a minor reflex center
  • 31 pairs of spinal nerves, which contain both sensory and motor axons.


White matter VS. Gray matter

  • White matter= Bundles of axons each coated with a sheath of myelin
  • Gray matter= Masses of the cell bodies and dendrites- each covered with synapses
  • In the spinal cord, white matter is at the surface; gray on the inside.
  • In the brain of mammals, the pattern is reversed.


The Peripheral Nervous System

  • Types of cells:
    • Sensory nervous cells carry information to the CNS from internal organs or external stimuli
    • Motor nervous cells carry information from the CNS to the effectors (muscles or glands)

The Peripheral Nervous System

  • The PNS can be divided into two divisions:
    • Sensory Division- nerve fibers in the peripheral nervous system that carry information from receptors to the brain and spinal cord
    • Motor Division- Refers to peripheral nerves that carry signals away from the brain and spinal cord to organs, muscles, and glands

The Motor Division

  • Motor division is divided into the:
    • Somatic nervous system- controls skeletal muscle; Voluntary system
    • Autonomic nervous system- controls involuntary muscles (smooth and cardiac); Involuntary system

The Autonomic Nervous System

  • The autonomic nervous system can be divided into the:
    • Parasympathetic division- controls inhibiting heart rate, contracting the bladder, and other nonemergency functions; Conserves energy
    • Sympathetic division- speeds up heart rate, relaxes the bladder, and responds in emergency situations


Overview of the Nervous System


The Chemical Senses:

Taste and Smell

  • Gustatory (taste) cells are located in the taste buds, primarily on the tongue.
  • The four major taste sensations:
    • Sweet
    • Salty
    • Sour
    • Bitter
  • Taste and appreciation of foods is influenced by the sense of smell and the temperature and texture of foods.

The Chemical Senses:

Taste and Smell

  • Olfactory (smell) receptors are located in the superior aspect of each nasal cavity
  • Sniffing helps to bring more air (containing odors) over the olfactory mucosa.
  • Olfactory pathways are closely linked to the limbic system; odors recall memories and arouse emotional responses.

The Eye and Vision

  • After light enters the pupil, it hits the lens, which sits behind the iris and is clear and colorless.
  • The lens’ job is to focus light rays on the back of the eyeball– a part called the retina.
  • Lens- Movie Projector
  • Retina- Film Screen

The Eye and Vision

  • Retina processes light by using special cells called rods and cones.
    • Rods- see in black, white, and shades of gray and tell us the form or shape that something has. Allow us to see in the dark
    • Cones- Sense color and need more light than rods to work well (most helpful in normal or bright light).


The Ear: Hearing

  • Outer Ear
    • Auricle- outermost part. Made of elastic cartilage.
    • External auditory canal- tube that extends from the auricle to the eardrum (tympanic membrane), which transmits sound waves to the middle ear

The Ear: Hearing

  • Middle Ear
    • Tympanic Cavity- small cavity that houses the ossicles(small bones inside the ear)
      • Malleus- “hammer”
      • Incus- “anvil”
      • Stapes- “stirrup”

The Ear: Hearing

  • Inner Ear
    • Vestibule- central egg-shaped cavity that contains receptors that respond to the pull of gravity and report changes of head position
    • Semicircular Canals- receptors respond to rotational movements of the head
    • Cochlea- “Snail” like chamber that houses the hearing receptor