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Chapter 12
Autonomic Nervous System
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.
Slide 1
Autonomic or Visceral Reflexes
• What They Do: Autonomic reflexes regulate
organ function
• Pathway: The sequence is receptor activation,
sensory input ( CNS), motor neuron
response, and effector response
Slide 2
Organization and Function of the
Autonomic Nervous System
• Divisions of the ANS: There are two divisions.
– Sympathetic nervous system, called “Fight or Flight.”
– Parasympathetic Nervous System, called “Feed and
Breed.”
• Autonomic Terminology and Autonomic
Pharmacology
– Drugs that affect the sympathetic nervous system are
called sympathomimetic and sympatholytic.
– Drugs that affect the parasympathetic nervous system
are called parasympathomimetic and parasympatholytic.
Slide 3
Organization and Function of the
Autonomic Nervous System - cont’d
• Autonomic Tone and Vasomotor Tone
– Background firing of the ANS causes autonomic
tone.
– Background sympathetic stimulation of the blood
vessels causes vasomotor tone.
Slide 4
ANS: Neurons
• Numbers and Ganglia
– Preganglionic fibers are fibers that extend from
the CNS to the ganglia.
– Postganglionic fibers are fibers that extend from
the ganglia to the effector organ.
Slide 5
ANS: Neurons - cont’d
• Neurons of the Sympathetic Nervous System
– The SNS is called the thoracolumbar outflow.
– The sympathetic ganglia are located in a chain
close to the spinal cord; the chain is called
paravertebral ganglia.
– The adrenal medulla secretes hormones that
mimic the SNS.
Slide 6
ANS: Neurons - cont’d
• Neurons of the Parasympathetic Nervous System
– The parasympathetic nervous system is called the
craniosacral outflow.
– Parasympathetic fibers travel with cranial nerves;
most parasympathetics run with the vagus nerve CN
X.
• Naming Fibers and Neurotransmitters
– Cholinergic fibers secrete acetylcholine (ACh).
– Adrenergic fibers secrete norepinephrine (NE).
Slide 7
ANS: Neurons - cont’d
• Neurotransmitters: Termination of Activity
– ACh is degraded immediately by
acetylcholinesterase.
– NE activity is ended primarily by reuptake of the
NE into the nerve terminal and by MAO activity
within the nerve terminal.
Slide 8
Receptors of the
Autonomic Nervous System
• Cholinergic Receptors
– These are activated by ACh.
– There are two types: muscarinic and nicotinic
(with subtypes).
• Adrenergic Receptors
– Activated by NE
– There are two types: alpha and beta
(with subtypes).
Slide 9
Receptors of the
Autonomic Nervous System - cont’d
• Receptor activation and blockade can be
determined by examining Tables 12-1, 12-3,
and 12-4.
• Autonomic Receptors: “Doing Autonomic
Pharmacology”
– Clinical examples where drugs target autonomic
receptors
Slide 10
Introduction
• The brain, spinal cord, and peripheral nervous
system act as a vast communication system.
The spinal cord transmits information to and
from the brain. The peripheral nervous system
brings information to the CNS (its sensory
role) and delivers information from the CNS to
the periphery (its motor role).
Slide 11
What the Spinal Cord Is
• The spinal cord is a tubelike structure located
in the spinal cavity, extending from the
foramen magnum (occipital bone) to L1
• Arrangement of Nervous Tissue
– The gray matter is a centrally located, butterflyshaped area.
– The white matter is composed of myelinated
fibers arranged in tracts. Ascending tracts are
sensory tracts. Descending tracts are motor tracts.
Slide 12
What the Spinal Cord Is - cont’d
• Arrangement of Nervous Tissue—cont’d
– Spinal nerves are attached to the spinal cord. All
spinal nerves are mixed (they contain sensory and
motor fibers).
– Sensory nerve fibers travel to the cord through the
dorsal root. Motor nerve fibers travel in the
ventral root.
Slide 13
What the Spinal Cord Does: Functions
• The spinal cord relays both sensory and motor
information.
• The spinal cord acts as a major reflex center.
Slide 14
Reflexes
• A reflex is an involuntary response to a
stimulus.
• The four components to a reflex are a sensory
receptor; an afferent (sensory) neuron; an
efferent (motor) neuron; and
an effector organ.
Slide 15
Peripheral Nervous System
• Nerve
– A nerve is a group of neurons, blood vessels,
and connective tissue.
– There are sensory nerves, motor nerves, and
mixed nerves.
Slide 16
Peripheral Nervous System - cont’d
• Structural Classification of Nerves
– A classification of nerves on the basis of structure
divides nerves into cranial nerves and spinal nerves.
There are 12 pairs of cranial nerves (Table 11-3) and
31 pairs of spinal nerves
(Table 11-5).
– Spinal nerves are sorted out at nerve plexuses. The
three major plexuses are the cervical plexus, the
brachial plexus, and the lumbosacral plexus.
– A dermatome is the area of skin innervated by each
spinal nerve.
Slide 17
Peripheral Nervous System - cont’d
• Functional Classification of Nerves
– Somatic afferent nerves carry sensory information
to the CNS.
– Somatic efferent nerves carry motor information
to skeletal muscles.
– Autonomic nerves carry motor information to the
organs (viscera).
Slide 18
Introduction
• The purpose of the nervous system is to bring
information to the central nervous system,
interpret the information, and enable the
body to respond to the information.
Slide 19
The Nervous System: Overview
• Divisions of the Nervous System
– The central nervous system (CNS) includes the
brain and the spinal cord.
– The peripheral nervous system includes the
nerves that connect the CNS with the rest of
the body.
Slide 20
The Nervous System: Overview - cont’d
• Cells That Make Up the Nervous System
– Neuroglia (glia) support, protect, and nourish the
neurons.
– Neurons conduct the nerve impulse.
– The three parts of a neuron are the dendrites,
cell body, and axon.
Slide 21
The Nervous System: Overview - cont’d
• Types of Neurons
– Sensory, or afferent, neurons carry information
toward the CNS.
– Interneurons are located in the CNS
(make connections).
– Motor, or efferent, neurons carry information
away from the CNS toward the periphery.
Slide 22
The Nervous System: Overview - cont’d
• White Matter and Gray Matter
– White matter is due to myelinated fibers.
– Gray matter is composed primarily of cell bodies,
interneurons, and unmyelinated fibers.
– Clusters of cell bodies (gray matter) are called
nuclei and ganglia.
Slide 23
The Neuron Carrying Information
• Nerve Impulse
– The electrical signal is called the action potential or
nerve impulse.
– The nerve impulse is due to the following changes
in the neuron: polarization, depolarization, and
repolarization.
– The nerve impulse is due to flow of ions:
polarization (outward flux of K+), depolarization
(influx of Na+), and repolarization (outward flux of
K+).
Slide 24
The Neuron Carrying Information - cont’d
• Nerve Impulse—cont’d
– The refractory period is the unresponsive period
of the neuron.
– The nerve impulse jumps from node to node as it
travels along a myelinated fiber. Myelination
increases the speed of the nerve impulse.
– The nerve impulse causes the release of a
neurotransmitter.
Slide 25
The Neuron Carrying Information - cont’d
• Synapse
– The synapse is a space between two neurons.
– The nerve impulse of the first (presynaptic)
neuron causes the release of neurotransmitter
into the synaptic cleft. The neurotransmitter
diffuses across the synaptic cleft and binds to the
receptors on the second (postsynaptic)
membrane. The activation of the receptors
stimulates a nerve impulse in the second neuron.
Slide 26
Brain: Structure and Function
• Cerebrum
– The right and left hemispheres are joined by the
corpus callosum.
– The four main cerebral lobes are the frontal,
parietal, temporal, and occipital lobes. Functions
of each lobe are summarized in Table 10-2.
– Large areas of the cerebrum, called association
areas, are concerned with interpreting,
integrating, and analyzing information.
Slide 27
Brain: Structure and Function - cont’d
• Diencephalon
– The thalamus is a relay station for most sensory
tracts traveling to the cerebrum.
– The hypothalamus controls many body functions
such as water balance, temperature, and the
secretion of hormones from the pituitary gland; it
exerts an effect on the autonomic nervous system.
Slide 28
Brain: Structure and Function - cont’d
• Brain Stem
– Brain stem: midbrain, pons, and medulla
oblongata.
– The medulla oblongata is called the vital center
because it controls the heart rate, blood pressure,
and respirations (the vital functions).
– The vomiting center is located in the medulla
oblongata; it receives input directly and indirectly
from activation of the chemoreceptor trigger zone
(CTZ).
Slide 29
Brain: Structure and Function - cont’d
• Cerebellum
– The cerebellum is sometimes called the little
brain.
– The cerebellum is concerned primarily with the
coordination of voluntary muscle activity.
Slide 30
Brain: Structure and Function - cont’d
• Structures Involving More than One Lobe
– The limbic system is sometimes called the
emotional brain.
– The reticular formation is concerned with the
sleep/wake cycle. It keeps us conscious and
prevents us from slipping into a coma state.
– The “memory areas” handle short-term and
long-term memory.
Slide 31
Protection of the CNS
• Bone: cranium and vertebral column
• Meninges: pia mater, arachnoid, and dura
mater
• Cerebrospinal fluid (CSF) that circulates within
the subarachnoid space
• Blood-brain barrier
Slide 32
Introduction
• The purpose of muscle is to contract and to
cause movement.
Slide 33
Muscle Function: Overview
• Types and Functions of Muscles
– Skeletal muscle is striated and voluntary; its
primary function is to produce movement.
– Smooth (visceral) muscle is nonstriated and
involuntary; it helps the organs perform their
functions.
– Cardiac muscle is striated and involuntary; it is
found only in the heart and allows the heart to
function as a pump.
Slide 34
Muscle Function: Overview - cont’d
• Structure of the Whole Muscle
– A large muscle consists of thousands of single
muscle fibers (muscle cells).
– Connective tissue binds the muscle fibers (cells)
together (forming compartments in the limbs) and
attaches muscle to bone and other tissue
(by tendons and aponeuroses).
Slide 35
Muscle Function: Overview - cont’d
• Structure and Function of a Single Muscle Fiber
– The muscle fiber (cell) is surrounded by a cell
membrane (sarcolemma). The cell membrane
penetrates to the interior of the muscle as the
transverse tubule (T tubule).
– An extensive sarcoplasmic reticulum (SR) stores
calcium.
– Each muscle fiber consists of a series of sarcomeres.
Each sarcomere contains the contractile proteins
actin and myosin.
Slide 36
Muscle Function: Overview - cont’d
• How Muscles Contract
– Muscles shorten or contract as the actin and myosin
(in the presence of calcium and ATP) interact through
crossbridge formation, according to the sliding filament
theory.
– For skeletal muscle to contract, it must be stimulated
by a motor nerve. The nerve impulse releases
acetycholine (ACh) from the nerve terminal. ACh
diffuses across the neuromuscular junction (NMJ),
binds to the muscle membrane and causes an electrical
signal to form in the muscle membrane.
Slide 37
Muscle Function: Overview - cont’d
• How Muscles Contract—cont’d
– The electrical signal enters the T-tubular system
and stimulates the SR to release calcium.
– Actin, myosin, and ATP interact to form
crossbridges, which cause sliding or shortening.
– Calcium is pumped back into the SR and the
muscles relax.
Slide 38
Muscle Function: Overview - cont’d
• Responses of a Whole Muscle
– A single muscle fiber contracts in an all-or-nothing response;
a whole muscle can contract partially
(i.e., not all-or-nothing).
– A whole muscle increases its force of contraction by
recruitment of additional muscle fibers.
– Two terms describe the contractile activity of a whole muscle:
twitch and tetanus. Tetanus refers to a sustained muscle
contraction.
– Energy for muscle contraction can be obtained from three
sources: burning fuel aerobically, burning fuel anaerobically,
and metabolizing creatine phosphate.
Slide 39
Muscle Function: Overview - cont’d
• Terms That Describe Muscle Movement
– Origin and Insertion: The attachments of the
muscles.
– Prime mover: The muscle most responsible for the
movement achieved by the muscle group
– Synergist and Antagonist: Works with, or has an
opposing action.
Slide 40
Muscles from Head to Toe
• Skeletal muscles are named according to size,
shape, direction of fibers, location, number of
origins, place of origin and insertion, and
muscle action.
• See Table 9-1 for a list of the body’s muscles.
Slide 41
Introduction
• The skeletal system supports the weight of the
body, supports and protects body organs,
enables the body to move, acts as storage site
for minerals, and produces blood cells.
Slide 42
Bones: An Overview
• Sizes and Shapes
– Bones are classified as long, short, flat, and irregular.
– Bone markings function as sites of muscle attachments and passages
for nerves and blood vessels.
– A long bone has a diaphysis (shaft) and two epiphyses (ends). Articular
cartilage is found on the outer surface of the epiphyses.
– The diaphysis is composed of compact or hard bone. The epiphysis
consists of spongy or soft bone; red marrow is found in the holes of
spongy bone.
Slide 43
Bones: An Overview - cont’d
• Bone Formation and Growth
– Bones ossify in two ways. In the skull, osteoblasts
replace thin connective tissue membrane, forming flat
bones. Other bones form on hyaline cartilage models
as osteoblasts replace cartilage with bone.
– Bones grow longitudinally at the epiphyseal disc, to
determine height; bones also grow thicker and wider
to support the weight of the body.
– Bone growth and reshaping occur throughout life and
depend on many factors, including diet, exercise, and
hormones.
Slide 44
Divisions of the Skeletal System
• The names of the 206 bones of the skeleton
are listed in Table 8-2.
Slide 45
Divisions of the Skeletal System - cont’d
• Axial Skeleton
– The axial skeleton includes the bones of the skull
(cranium and face), hyoid bone, bones of the
middle ear, bones of the vertebral column, and
the thoracic cage.
– The skull of a newborn contains fontanels, which
are membranous areas that allow brain growth.
– The skull contains air-filled cavities called sinuses.
Slide 46
Divisions of the Skeletal System - cont’d
• Axial Skeleton—cont’d
– The vertebral column is formed from 26
vertebrae, one sacrum, and one coccyx. The
vertebrae are separated by cartilaginous discs. The
vertebral column of the adult has four curvatures:
cervical, thoracic, lumbar, and sacral.
– The thoracic cage is a bony, cone-shaped cage
formed by the sternum, 12 pairs of ribs, and
thoracic vertebrae.
Slide 47
Divisions of the Skeletal System - cont’d
• Appendicular Skeleton
– The appendicular skeleton includes the bones of
the extremities (arms and legs), and the bones of
the hip and shoulder girdles.
– The shoulder girdle consists of the scapula and the
clavicle.
– The pelvic girdle is formed by the two coxal bones
and is secured to the axial skeleton at the sacrum.
Slide 48
Joints
• A joint or articulation is the site where two
bones meet.
Slide 49
Joints - cont’d
• Types of Joints
(based on the degree of movement)
– Immovable joints.
– Slightly movable joints.
– Freely movable joints or synovial joints. Structures
within a synovial joint (knee): articular cartilage, the
joint capsule, synovial membrane, synovial fluid,
bursae, and supporting ligaments.
– The types of freely movable joints include hinge, ball
and socket, pivot, gliding, saddle, and condyloid.
Slide 50
Joints - cont’d
• Joint Movement
– Freely movable joints are capable of different
types of movement.
– Types of movements at freely movable joints
include flexion and extension, abduction and
adduction, inversion and eversion, supination
and pronation, and circumduction.
Slide 51
Introduction
• The integumentary system includes the skin,
which covers the body, protects the internal
organs, and plays an important role in the
regulation of body temperature.
Slide 52
Structures: Organs of the
Integumentary System
• The integumentary system includes the skin,
accessory structures, and subcutaneous tissue
beneath the skin.
Slide 53
Structures: Organs of the
Integumentary System - cont’d
• Skin
– The skin is called the cutaneous membrane.
– The skin has two layers, an outer layer called the
epidermis and an inner layer called the dermis.
– The epidermis has five layers. The stratum
germinativum is the layer in which cell division takes
place. The new cells produce keratin (waterproofing)
and die as they are pushed toward the surface. The
outer layer is the stratum corneum and consists of
flattened, dead, keratinized cells.
Slide 54
Structures: Organs of the
Integumentary System - cont’d
• Skin—cont’d
– The dermis lies on the subcutaneous tissue.
– Skin color is determined by many factors: some
genetic, some physiologic, and some due to disease.
Melanin causes skin to darken. Carotene causes skin
to appear yellow. The amount of blood in the skin
affects skin color (e.g., flushing) as does the
appearance of abnormal substances such as
bilirubin (jaundice) and a low blood oxygen content
(cyanosis).
Slide 55
Structures: Organs of the
Integumentary System - cont’d
• Accessory Structures of the Skin
– Hair is unevenly distributed over the skin. The location
of the hair determines its function. Eyebrows and
eyelashes protect the eyes from dust and perspiration.
– The main parts of a hair are the shaft and root.
– Hair color is determined by the amount and type of
melanin.
– Nails are thin plates of stratified squamous epithelial
cells that contain a hard form of keratin.
– There are two major exocrine glands in the skin:
sebaceous glands and sweat glands.
Slide 56
Structures: Organs of the
Integumentary System - cont’d
• Accessory Structures of the Skin—cont’d
– The sebaceous glands (oil glands) secrete sebum. The
sebum lubricates hair and skin. In the fetus, these
glands secrete vernix caseosa, a cheeselike substance
that coats the skin of a newborn.
– The two types of sweat glands (sudoriferous glands)
are the apocrine glands and the eccrine glands. The
eccrine sweat glands play a crucial role in temperature
regulation.
– The mammary glands (which secrete milk) and the
ceruminous glands (which secrete ear wax) are
modified sweat glands.
Slide 57
Structures: Organs of the
Integumentary System - cont’d
• Subcutaneous Tissue
– Subcutaneous tissue anchors the dermis to
underlying structures.
– Subcutaneous tissue acts as an insulator; it
prevents heat loss.
Slide 58
Regulation of Body Temperature
• Heat Production
– Heat produced by metabolizing cells constitutes
the body temperature.
– Most of the heat is produced by the muscles and
the liver.
• Heat Loss
– Most of the heat (80%) is lost through the skin.
– Heat loss occurs through radiation, conduction,
convection, and evaporation.
Slide 59
Regulation of Body Temperature - cont’d
• Heat Loss—cont’d
– Normal body temperature is set by the body’s
thermostat in the hypothalamus.
– Heat is lost through sweating and vasodilation.
Heat is conserved by vasoconstriction and
produced by shivering.
Slide 60
When Skin Is Burned
• Physiological Effects
– Short-term effects: fluid and electrolyte losses,
shock, inability to regulate body temperature,
infection
– Long-term effects: scarring, loss of function, and
cosmetic and emotional problems
• Classification of Burns
– Classified according to the thickness of the burn
(partial, full); also first, second, and third degree.
– The rule of nines is a way to evaluate burns.
Slide 61
Introduction
• Tissues are groups of cells similar to each
other in structure and function.
• Membranes are thin sheets of tissue that
cover surfaces, line body cavities, and
surround organs.
Slide 62
Types of Tissue
• Epithelial Tissue Types
– Epithelial tissue covers surfaces, lines cavities, and
engages in secretion/absorption and protective
functions.
– Epithelial tissue is classified according to cell shape
(squamous, cuboidal, and columnar) and layers
(simple and stratified).
– The types and functions are summarized in Table 61.
Slide 63
Types of Tissue - cont’d
• Connective Tissue
– The primary function of connective tissue is to bind
together the parts of the body. Other functions
include support, protection, fat storage, and transport
of substances.
– Connective tissue has an abundant intercellular matrix
that fills spaces between cells. The intercellular matrix
may be liquid, gel-like, or hard. The matrix often
contains protein fibers that are secreted by the cells.
– There are three types of loose connective tissue:
areolar, adipose, and reticular.
Slide 64
Types of Tissue - cont’d
• Connective Tissue—cont’d
– Dense fibrous connective tissue forms tendons, ligaments,
capsules, and fascia, and is found in the skin (dermis).
– Types of cartilage include: hyaline, elastic, and
fibrocartilage.
– Bone (osseous tissue) is connective tissue formed by
osteocytes. Bone cells have a hard intercellular matrix that
includes collagen, calcium salts, and other minerals.
– Blood and lymph are types of connective tissue that have a
watery intercellular matrix.
Slide 65
Types of Tissue - cont’d
• Nervous Tissue
– Nervous tissue is found in the peripheral nerves,
brain, and spinal cord.
– The two types of nervous tissue are neurons,
which transmit electrical signals, and neuroglia,
which support and take care of the neurons.
• Muscle Tissue
– Muscle cells contract, thereby causing movement.
– The three kinds of muscle are skeletal, smooth,
and cardiac.
Slide 66
Tissue Repair
• Tissue Repair by Regeneration
– Replacement of tissue by cells that undergo
mitosis
• Tissue Repair by Fibrosis
– Formation of scar tissue
Slide 67
Membranes
• Epithelial Membranes
– The cutaneous membrane is the skin.
– Mucous membranes are epithelial membranes that line all
body cavities that open to the exterior of the body.
– Serous membranes are epithelial membranes that line the
ventral body cavities, which are not open to the exterior of
the body.
– Serous membranes form two layers: a parietal layer that lines
the wall of the cavity and a visceral layer that covers the
outside of an organ.
– The three serous membranes are the pleura, the
pericardium, and the peritoneum.
Slide 68
Membranes - cont’d
• Connective Tissue Membranes
– Synovial membranes are connective tissue
membranes.
– Other connective tissue membranes are listed in
Table 6-3.
Slide 69