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Nervous System. Chapter 7. Three Basic Functions:. Sensory Input Uses millions of sensory receptors to monitor changes occurring both inside and outside the body…these changes are called stimuli and the gathered information is called sensory input Integration - PowerPoint PPT Presentation
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Nervous System
Chapter 7
Three Basic Functions:
Sensory Input Uses millions of sensory receptors to monitor changes
occurring both inside and outside the body…these changes are called stimuli and the gathered information is called sensory input
Integration Processes and interprets the sensory input and makes
decisions about what should be done at each moment…a process called integration
Motor Output Effects a response by activating muscles or glandes
(effectors) through motor output
Organization of Nervous System:
Structural Structures
Functional Activities
Structural Organization: Includes all nervous
system organs 2 subdivisions:
Central Nervous System (CNS)
Peripheral Nervous System (PNS)
Central Nervous System (CNS): Consists of the brain and spinal cord
Peripheral Nervous System (PNS): Consists mainly of nerves that
extend from the brain and spinal cord
Spinal nerves: carry impulses to and from the spinal cord (31 pairs)
Cranial nerves: carry impulses to and from the brain (12 pairs)
These are the communication lines…linking all parts of the body by carrying impulses from sensory receptors to the CNS and from the CNS to appropriate glands/muscles
Cranial Nerves: Listed on pages 250-251 and picture on page
252 12 pairs Serve the head and neck Most are mixed nerves (send impulses both
ways…to and from CNS) Only 1 pair-the vagus nerve-extends to the
thoracic and abdominal cavities
Giraffe Vagus Nerve Dissection
Spinal Nerves: Listed on page 255 31 pairs of human spinal nerves are formed by the combination
of the ventral and dorsal roots of the spinal cord Each spinal nerve is only about ½ inch long and almost
immediately after being formed divides into dorsal and ventral “rami”
The rami contain both motor and sensory fibers…thus damage to a spinal nerve or its “rami” results in loss of sensation and paralysis of area of body served
Smaller dorsal rami serve the skin and muscles of the posterior body trunk
Ventral rami of spinal nerves T1-T12 supply the muscles between the ribs and skin and muscles of the anterior and lateral trunk
The ventral rami of all other spinal nerves form the complex networks or nerves called plexuses, which serves the motor and sensory needs of the limbs.
Functional Classification: Concerns only PNS structures Divides them into 2 principal
subdivisions Sensory (or afferent) division Motor (or efferent) division
Functional Subdivisions:Sensory (Afferent):
Consists of nerve fibers that convey impulses to the CNS from sensory receptors
Motor (Efferent):
Carry impulses from the CNS to effector organs, muscles, and glands
These impulses activate muscles and glands…they “effect” a motor response
Has 2 subdivisions…
2 subdivisions of Motor division:
Somatic Nervous System Allows us to consciously,
or voluntarily, control our skeletal muscles
Often referred to as “voluntary nervous system”
Autonomic Nervous System Regulates events that are
automatic or involuntary such as the activity of smooth and cardiac muscles and glands
Referred to as “involuntary nervous system”
Has 2 parts: Sympathetic &
Parasympathetic: Bring about opposite
effects…one stimulates while one inhibits
Nervous Tissue: Structure & Function Nervous tissue is made up of just 2
types of cells…supporting cells and neurons
You should remember neurons from the tissue chapter….probably easiest slide to ID!
“Neuroglia” (supporting cells) Neuroglia literally
means “nerve glue” 6 types:
1. Astrocytes2. Microglia3. Ependymal cells4. Oligodendrocytes5. Schwann cells6. Satellite cells
Neurons (nerve cells) Highly specialized to
transmit messages (nerve impulses) from one part of the body to another
Neurons can differ structurally, but have many common features like the cell body (that includes the nucleus and is metabolic center of cell)and one or more processes (or fibers)…
Processes: Vary in length from microscopic to 3
or 4 feet…longest ones in humans reach from lumbar region of the spine to the great toe!
Processes that convey incoming messages toward the cell body are dendrites (dendr=tree)
Processes that generate nerve impulses and conduct them away from the cell body are axons (a&a)
Neurons may have hundreds of the branching dendrites, depending of the neuron types, but each neuron has only one axon…all axons branch profusely at their terminal end…forming hundreds to thousands of axon terminals!
Axons continued…. Axon terminals contain hundreds of tiny vesicles, or
membranous sacs that contain chemicals called neurotransmitters
As said earlier, axons transmit nerve impulses away from the cell body…when these impulses reach the axon terminals, they stimulate the release of neurotransmitters into extracellular space
Each axon terminal is separated from the next neuron y a tiny gap called the synapse
Although they are close, neurons never actually touch other neurons!
More Neuron Anatomy: Myelin:
Whitish, fatty material that covers long nerve fibers Protects and insulates the fibers and increases the
transmission rate of nerve impulses Schwann cells:
Specialized supporting cells that wrap themselves tightly around the axon jelly-roll fashion
When the wrapping process is done, a tight coil of wrapped membranes, the myelin sheath, encloses the axon
Nodes of Ranvier: Since the myelin sheath is formed by many
individual Schwann cells, it has gaps or indentations, called nodes of Ranvier at regular internals
Nerve Impulses: 2 major functions:
1. irritability The ability to respond to a stimulus and convert it into a
nerve impulse 2. conductivity
The ability to transmit the impulse to other neurons, muscles or glands.
*Figure 7.9, pg.232 describes how nerve impulses work in a step by step manner. Here are some videos:
Nerve Impulse Animation Animation: Transmission Across a Synapse Nerve impulse Animation - YouTube
Reflexes Rapid, predictable, and involuntary
responses to stimuli Like one way streets-once it begins,
always goes in the same direction Occur over neural pathways called
reflex arcs Involve both CNS and PNS
Types of Reflexes:Somatic
All reflexes that stimulate skeletal system Ex: When you pull your hand away from hot object
Autonomic Regulate activity of smooth muscles, heart, and
glands Regulate digestion, elimination, blood pressure,
and sweating Ex: Changes in size of pupil
Reflex Arcs 5 Elements:1. Receptor2. Effector organ3. Sensory neuron4. Integration center5. Motor neuron
Brain Anatomy:4 major regions:
1. Cerebral hemispheres2. Diencephalon3. Brain stem4. Cerebellum
Cerebral Hemispheres “cerebrum”
Most superior part of brain and together are larger than the other 3 brain regions combined!
Controls sensory and motor functions and higher mental function like memory and reasoning and higher mental function (like memory and reasoning).
Diencephalon (interbrain): Sits atop the brain
stem and is enclosed by the cerebral hemispheres
Includes: Thalamus,
hypothalamus, and epithalamus
Brain Stem: About the size of a thumb
in diameter and about 3 inches long
Includes:1. Midbrain: reflex centers
involved with vision and hearing
2. Pons: nuclei involved in the control of breathing
3. Medulla oblongata: contains centers that control heart rate, blood pressure, breathing, swallowing, vomiting, and others.
Cerebellum: Large, cauliflower-like
structure that projects dorsally
Has 2 hemispheres (like cerebrum)
Provides the precise timing for skeletal muscle activity and controls our balance and equilibrium…Because of its activity, body movements are smooth and coordinated
Meninges (Protection of CNS) 3 connective tissue membranes that
cover and protect the CNS Dura mater
Outermost layer “tough or hard mother” Arachnoid mater
“spider” some think it looks like web Pia mater
Innermost layer “gentle mother”-clings tightly to surface of brain and spinal chord
Spinal Cord: About 17in, glistening white
continuation of brain stem Provides a 2-way conduction
pathway to and from the brain Major reflex center Is enclosed within the vertebral
column Extends from the foramen
magnum of the skull to the first or second lumbar vertebra, where it ends just below the ribs
Also protected by meninges In humans, 31 pairs of spinal
nerves arise from the cord and exit from the vertebral column to serve the body area close by!