Download Spinal cord and reflexes

Spinal Cord and Reflexes
Muse: Lecture #14
7/7/10
Spinal cord, nerves and reflexes
Figure 13–1 An Overview of Chapters 13 and 14.
Central nervous system (CNS)
Peripheral nervous system (PNS)
Sensory (afferent)
division
Motor (efferent) division
Somatic nervous
system
Sympathetic
division
accelerator
Autonomic nervous
system (ANS)
Parasympathetic
division
brake
Figure 13.1
Spinal Cord
 Gross Anatomy of the Spinal Cord
 About 18 inches (45 cm) long
 1/2 inch (14 mm) wide
 Ends between vertebrae L1 and L2
 Bilateral symmetry
 Grooves divide the spinal cord into left and right
 Posterior median sulcus: on posterior side
 Anterior median fissure: deeper groove on anterior side
Spinal Cord
 Gross Anatomy of the Spinal Cord
 The Distal End
 Conus medullaris:
– thin, conical spinal cord below lumbar enlargement
 Filum terminale:
– thin thread of fibrous tissue at end of conus medullaris
– attaches to coccygeal ligament
 Cauda equina:
– nerve roots extending below conus medullaris
Spinal Cord
Figure 13–2 Gross Anatomy of the Adult Spinal Cord.
Spinal Cord
Figure 13–2 Gross Anatomy of the Adult Spinal Cord.
Made by Honda?
Spinal Cord
 31 Spinal Cord Segments
 Based on vertebrae where spinal nerves
originate
 Positions of spinal segment and vertebrae
change with age
 Cervical nerves:
– are named for inferior vertebra
 All other nerves:
– are named for superior vertebra
Spinal Cord
 Roots
 Two branches of spinal nerves
 Ventral root:
– contains axons of motor neurons
 Dorsal root:
– contains axons of sensory neurons
 Dorsal root ganglia
 contain cell bodies of sensory neurons
Spinal Cord
 The Spinal Nerve
 Each side of spine
 Dorsal and ventral roots join
 To form a spinal nerve
 Mixed Nerves
 Carry both afferent (sensory) and efferent (motor)
fibers
Spinal Cord
Figure 13–3 The Spinal Cord and Spinal Meninges
Spinal Cord
Figure 13–3 The Spinal Cord and Spinal Meninges
Spinal Cord
 The Spinal Meninges
 Specialized membranes isolate spinal cord from
surroundings
 Functions of the spinal meninges include
 Protect spinal cord
 Carry blood supply
 Continuous with cranial meninges
 Meningitis:
 Viral or bacterial infection of meninges
Spinal Cord
 The Three Meningeal Layers
 Dura mater
 Outer layer of spinal cord
 Arachnoid mater
 Middle meningeal layer
 Pia mater
 Inner meningeal layer
Spinal Cord
 The Dura Mater
 Tough and fibrous
 Cranially
 Fuses with periosteum of occipital bone
 Is continuous with cranial dura mater
 Caudally
 Tapers to dense cord of collagen fibers
 Joins filum terminale in coccygeal ligament
 The Epidural Space
 Between spinal dura mater and walls of vertebral canal
 Contains loose connective and adipose tissue
 Anesthetic injection site
Spinal Cord
 The Arachnoid Mater
 Middle meningeal layer
 Arachnoid membrane
 Simple squamous epithelia
 Covers arachnoid mater
Spinal Cord
 The Interlayer Spaces of Arachnoid Mater
 Subdural space
 Between arachnoid mater and dura mater
 Subarachnoid space
 Between arachnoid mater and pia mater
 Contains collagen/elastin fiber network (arachnoid trabeculae)
 Filled with cerebrospinal fluid (CSF)
 Cerebrospinal Fluid (CSF)
 Carries dissolved gases, nutrients, and wastes
 Spinal tap: withdraws CSF
Spinal Cord
 The Pia Mater
 Is the innermost meningeal layer
 Is a mesh of collagen and elastic fibers
 Is bound to underlying neural tissue
Spinal Cord
Figure 13–4 The Spinal Cord and Associated Structures
Gray Matter and White Matter
 Sectional Anatomy of the Spinal Cord
 White matter
 Is superficial
 Contains myelinated and unmyelinated axons
 Gray matter
 Surrounds central canal of spinal cord
 Contains neuron cell bodies, neuroglia, unmyelinated axons
 Has projections (gray horns)
Gray Matter and White Matter
 Organization of Gray Matter
 The gray horns
 Posterior gray horns: contain somatic and visceral
sensory nuclei
 Anterior gray horns: contain somatic motor nuclei
 Lateral gray horns: are in thoracic and lumbar
segments; contain visceral motor nuclei
 Gray commissures
 Axons that cross from one side of cord to the other
before reaching gray matter
Gray Matter and White Matter
 Organization of Gray Matter
 The cell bodies of neurons form functional
groups called nuclei
 Sensory nuclei:
– dorsal (posterior)
– connect to peripheral receptors
 Motor nuclei:
– ventral (anterior)
– connect to peripheral effectors
Gray Matter and White Matter
 Control and Location
 Sensory or motor nucleus location within the
gray matter determines which body part it
controls
Gray Matter and White Matter
 Organization of White Matter
 Posterior white columns: lie between posterior gray
horns and posterior median sulcus
 Anterior white columns: lie between anterior gray
horns and anterior median fissure
 Anterior white commissure: area where axons cross from one
side of spinal cord to the other
 Lateral white columns: located on each side of
spinal cord between anterior and posterior columns
Gray Matter and White Matter
 Organization of White Matter
 Tracts or fasciculi
 In white columns
 Bundles of axons
 Relay same information in same direction
 Ascending tracts:
– carry information to brain
 Descending tracts:
– carry motor commands to spinal cord
Gray Matter and White Matter
Figure 13–5a The Sectional Organization of the Spinal Cord.
Gray Matter and White Matter
Figure 13–5b The Sectional Organization of the Spinal Cord.
Spinal Cord Summary
 Spinal cord has a narrow central canal
 Surrounded by gray matter
 Containing sensory and motor nuclei
 Sensory nuclei are dorsal
SounD
 Motor nuclei are ventral
MoVe
Spinal Cord Summary
 Gray matter
 Is covered by a thick layer of white matter
 White matter
 Consists of ascending and descending axons
 Organized in columns
 Containing axon bundles with specific functions
 Spinal cord is so highly organized
 It is possible to predict results of injuries to specific
areas
Spinal Nerves and Plexuses
 Anatomy of Spinal Nerves
 Every spinal cord segment
 Is connected to a pair of spinal nerves
 Every spinal nerve
 Is surrounded by three connective tissue layers
 That support structures and contain blood vessels
Spinal Nerves and Plexuses
 Three Connective Tissue Layers of Spinal Nerves
 Epineurium
 Outer layer
 Dense network of collagen fibers
 Perineurium
 Middle layer
 Divides nerve into fascicles (axon bundles)
 Endoneurium
 Inner layer
 Surrounds individual axons
Spinal Nerves and Plexuses
Figure 13–6a A Peripheral Nerve.
Spinal Nerves and Plexuses
 Peripheral Nerves
 Interconnecting branches of spinal nerves
 Surrounded by connective tissue sheaths
Spinal Nerves and Plexuses
Spinal Nerves and Plexuses
 Peripheral Distribution of Spinal Nerves
 Sensory nerves
 In addition to motor impulses:
– dorsal, ventral, and white rami also carry sensory information
 Dermatomes
 Bilateral region of skin
 Monitored by specific pair of spinal nerves
Spinal Nerves and Plexuses
Figure 13–7b Peripheral Distribution of Spinal Nerves.
Spinal Nerves and Plexuses
Figure 13–8 Dermatomes.
Spinal Nerves and Plexuses
 Peripheral Neuropathy
 Regional loss of sensory or motor function
 Due to trauma or compression
 chronic can be due to diabetes
Spinal Nerves and Plexuses
 Nerve Plexuses
 Complex, interwoven networks of nerve fibers
 Formed from blended fibers of ventral rami of
adjacent spinal nerves
 Control skeletal muscles of the neck and
limbs
Spinal Nerves and Plexuses
 The Four Major Plexuses of Ventral Rami
 Cervical plexus
 Brachial plexus
 Lumbar plexus
 Sacral plexus
Spinal Nerves and Plexuses
Figure 13–10 Peripheral Nerves and Nerve Plexuses.
Spinal Nerves and Plexuses
Figure 13–10 Peripheral Nerves and Nerve Plexuses.
Spinal Nerves and Plexuses
 The Cervical Plexus of the Ventral Rami
 Includes ventral rami of spinal nerves C1–C5
 Innervates neck, thoracic cavity, diaphragmatic
muscles
 Major nerve
 Phrenic nerve (controls diaphragm)
Spinal Nerves and Plexuses
Figure 13–11 The Cervical Plexus.
Spinal Nerves and Plexuses
Spinal Nerves and Plexuses
Includes ventral rami of spinal nerves C5–T1
 The Brachial Plexus of the Ventral Rami
 Major nerves of brachial plexus
 Musculocutaneous nerve (lateral cord)
 Median nerve (lateral and medial cords)
 Ulnar nerve (medial cord)
 Axillary nerve (posterior cord)
 Radial nerve (posterior cord)
Spinal Nerves and Plexuses
Figure 13–12a The Brachial Plexus.
Spinal Nerves and Plexuses
Figure 13–12b The Brachial Plexus.
Spinal Nerves and Plexuses
Figure 13–12c The Brachial Plexus.
Spinal Nerves and Plexuses
Spinal Nerves and Plexuses
 The Lumbar Plexus of the Ventral Rami
 Includes ventral rami of spinal nerves T12–L4
 Major nerves
 Genitofemoral nerve
 Lateral femoral cutaneous nerve
 Femoral nerve
Spinal Nerves and Plexuses
 The Sacral Plexus of the Ventral Rami
 Includes ventral rami of spinal nerves L4–S4
 Major nerves
 Pudendal nerve
 Sciatic nerve
 Branches of sciatic nerve
 Fibular nerve
 Tibial nerve
3D Rotation of Lumbar and Sacral Plexuses
Spinal Nerves and Plexuses
Figure 13–13b The Lumbar and Sacral Plexuses.
Spinal Nerves and Plexuses
Figure 13–13d The Lumbar and Sacral Plexuses.
Neuronal Pools
 Functional Organization of Neurons
 Sensory neurons
 About 10 million
 Deliver information to CNS
 Motor neurons
 About 1/2 million
 Deliver commands to peripheral effectors
 Interneurons
 About 20 billion
 Interpret, plan, and coordinate signals in and out
Neuronal Pools
 Neuronal Pools
 Functional groups of interconnected neurons
(interneurons)
 Each with limited input sources and output
destinations
 May stimulate or depress parts of brain or spinal cord
Neuronal Pools
Five Patterns of Neural Circuits in Neuronal
Pools
 Divergence
 Spreads stimulation to many neurons or neuronal
pools in CNS
 Convergence
 Brings input from many sources to single neuron
 Serial processing
 Moves information in single line
Neuronal Pools
 Five Patterns of Neural Circuits in Neuronal
Pools
 Parallel processing
 Moves same information along several paths simultaneously
 Reverberation
 Positive feedback mechanism
 Functions until inhibited
Neuronal Pools
Figure 13–14 Neural Circuits: The Organization of Neuronal Pools.
Reflexes
 Automatic responses coordinated within
spinal cord
 Through interconnected sensory neurons,
motor neurons, and interneurons
 Produce simple and complex reflexes
Reflex Arc
2 SENSORY NEURON
(axon conducts impulses from
receptor to integrating center)
1 SENSORY RECEPTOR
(responds to a stimulus
by producing a generator
or receptor potential)
Interneuron
3 INTEGRATING CENTER
(one or more regions within the CNS
that relay impulses from sensory to
motor neurons)
4 MOTOR NEURON
(axon conducts impulses from
integrating center to effector)
5 EFFECTOR
(muscle or gland that
responds to motor
nerve impulses)
Reflexes
 Neural Reflexes




Rapid, automatic responses to specific stimuli
Basic building blocks of neural function
One neural reflex produces one motor response
Reflex arc




The wiring of a single reflex
Beginning at receptor
Ending at peripheral effector
Generally opposes original stimulus (negative feedback)
Reflexes
 Five Steps in a Neural Reflex
 Step 1: Arrival of stimulus, activation of receptor
 Physical or chemical changes
 Step 2: Activation of sensory neuron
 Graded depolarization
 Step 3: Information processing by postsynaptic cell
 Triggered by neurotransmitters
 Step 4: Activation of motor neuron
 Action potential
 Step 5: Response of peripheral effector
 Triggered by neurotransmitters
Reflexes
Figure 13–15 Events in a Neural Reflex.
Reflexes
 Four Classifications of Reflexes
 By early development
 By type of motor response
 By complexity of neural circuit
 By site of information processing
Reflexes
 Development
 How reflex was developed
 Innate reflexes:
– basic neural reflexes
– formed before birth
 Acquired reflexes:
– rapid, automatic
– learned motor patterns
Reflexes
 Motor Response
 Nature of resulting motor response
 Somatic reflexes:
– involuntary control of nervous system
» superficial reflexes of skin, mucous membranes
» stretch or deep tendon reflexes (e.g., patellar, or “kneejerk”, reflex)
 Visceral reflexes (autonomic reflexes):
– control systems other than muscular system
Reflexes
 Complexity of Neural Circuit
 Monosynaptic reflex
 Sensory neuron synapses directly onto motor neuron
 Polysynaptic reflex
 At least one interneuron between sensory neuron and motor
neuron
 Site of Information Processing
 Spinal reflexes
 Occurs in spinal cord
 Cranial reflexes
 Occurs in brain
Reflexes
Figure 13–16 The Classification of Reflexes.
Spinal Reflexes
 Spinal Reflexes
 Range in increasing order of complexity
 Monosynaptic reflexes
 Polysynaptic reflexes
 Intersegmental reflex arcs:
– many segments interact
– produce highly variable motor response
Spinal Reflexes
 Monosynaptic Reflexes
 A stretch reflex
 Have least delay between sensory input and motor
output:
 For example, stretch reflex (such as patellar reflex)
 Completed in 20–40 msec
 Receptor is muscle spindle
Spinal Reflexes
Figure 13–17 A Stretch Reflex.
Spinal Reflexes
 Postural reflexes
 Stretch reflexes
 Maintain normal upright posture
 Stretched muscle responds by contracting
 Automatically maintain balance
Spinal Reflexes
 Polysynaptic Reflexes
 More complicated than monosynaptic reflexes
 Interneurons control more than one muscle
group
 Produce either EPSPs or IPSPs
Excitory post synaptic potentials
Spinal Reflexes
 The Tendon Reflex
Polysynaptic
 Prevents skeletal muscles from
 Developing too much tension
 Tearing or breaking tendons
 Sensory receptors unlike muscle spindles or
proprioceptors
To brain
Inhibitory
interneuron
5 EFFECTOR
(muscle attached
to same tendon)
relaxes and
relieves excess
tension
4 MOTOR NEURON
inhibited
+
++
2 SENSORY
NEURON
excited
–
Increased tension
stimulates
1 SENSORY
RECEPTOR (tendon)
+
Spinal
nerve
3 Within INTEGRATING
+
Antagonistic
muscles
contract
CENTER (spinal cord),
sensory neuron activates
inhibitory interneuron
Motor neuron to
antagonistic
muscles is excited
Excitatory
interneuron
Spinal Reflexes
 Withdrawal Reflexes
 Move body part away from stimulus (pain or pressure)
 For example, flexor reflex:
– pulls hand away from hot stove
 Strength and extent of response
 Depends on intensity and location of stimulus
Spinal Reflexes
Figure 13–19 A Flexor Reflex.
Spinal Reflexes
 Reciprocal Inhibition
 For flexor reflex to work
 The stretch reflex of antagonistic (extensor)
muscle must be inhibited (reciprocal inhibition) by
interneurons in spinal cord
Spinal Reflexes
 Reflex Arcs
 Ipsilateral reflex arcs
 Occur on same side of body as stimulus
 Stretch, tendon, and withdrawal reflexes
 Crossed extensor reflexes
 Involve a contralateral reflex arc
 Occur on side opposite stimulus
Spinal Reflexes
 Crossed Extensor Reflexes
 Occur simultaneously, coordinated with flexor reflex
 For example, flexor reflex causes leg to pull up
 Crossed extensor reflex straightens other leg
 To receive body weight
 Maintained by reverberating circuits
Spinal Reflexes
Figure 13–20 The Crossed Extensor Reflex.
Spinal Reflexes
 Five General Characteristics of Polysynaptic
Reflexes
 Involve pools of neurons
 Are intersegmental in distribution
 Involve reciprocal inhibition
 Have reverberating circuits
 Which prolong reflexive motor response
 Several reflexes cooperate
 To produce coordinated, controlled response
The Brain Can Alter Spinal Reflexes
 Integration and Control of Spinal Reflexes
 Reflex behaviors are automatic
 But processing centers in brain can facilitate or
inhibit reflex motor patterns based in spinal cord
The Brain Can Alter Spinal Reflexes
 Voluntary Movements and Reflex Motor
Patterns
 Higher centers of brain incorporate lower,
reflexive motor patterns
 Automatic reflexes
 Can be activated by brain as needed
 Use few nerve impulses to control complex motor
functions
 Walking, running, jumping
The Brain Can Alter Spinal Reflexes
 Reinforcement of Spinal Reflexes
 Higher centers reinforce spinal reflexes
 By stimulating excitatory neurons in brain stem or
spinal cord
 Creating EPSPs at reflex motor neurons
 Facilitating postsynaptic neurons
The Brain Can Alter Spinal Reflexes
 Inhibition of Spinal Reflexes
 Higher centers inhibit spinal reflexes by
 Stimulating inhibitory neurons
 Creating IPSPs at reflex motor neurons
 Suppressing postsynaptic neurons
The Brain Can Alter Spinal Reflexes
 The Babinski Reflexes
 Normal in infants
 May indicate CNS damage in adults
The Brain Can Alter Spinal Reflexes
Figure 13–21 The Babinski Reflexes.
An Introduction to the Brain and Cranial
Nerves
 The Adult Human Brain
 Ranges from 750 cc to 2100 cc
 Contains almost 97% of the body’s neural
tissue
 Average weight about 1.4 kg (3 lb)
The Brain
 Six Regions of the Brain
 Cerebrum
 Cerebellum
 Diencephalon
 Mesencephalon
 Pons
 Medulla oblongata
The Brain
Figure 14–1 An Introduction to Brain Structures and Functions.
The Brain
Figure 14–2 Ventricles of the Brain.
Brain Protection and Support
 Physical protection
 Bones of the cranium
 Cranial meninges
 Cerebrospinal fluid
 Biochemical isolation
 Blood–brain barrier
Brain Protection and Support
 Cerebrospinal Fluid (CSF)
 Surrounds all exposed surfaces of CNS
 Interchanges with interstitial fluid of brain
 Functions of CSF
 Cushions delicate neural structures
 Supports brain
 Transports nutrients, chemical messengers, and
waste products
Brain Protection and Support
Figure 14–4 The Formation and Circulation of Cerebrospinal Fluid.
Brain Protection and Support
 Blood Supply to the Brain
 Supplies nutrients and oxygen to brain
 Delivered by internal carotid arteries and
vertebral arteries
 Removed from dural sinuses by internal
jugular veins
Brain Protection and Support
Figure 21–23 Arteries of the Brain.
Brain Protection and Support
 Blood–Brain Barrier
 Isolates CNS neural tissue from general circulation
 Formed by network of tight junctions
 Between endothelial cells of CNS capillaries
 Lipid-soluble compounds (O2, CO2), steroids, and
prostaglandins diffuse into interstitial fluid of brain and
spinal cord
 Astrocytes control blood–brain barrier by releasing
chemicals that control permeability of endothelium
Brain Protection and Support
 Blood–CSF Barrier
 Formed by special ependymal cells
 Surround capillaries of choroid plexus
 Limits movement of compounds transferred
 Allows chemical composition of blood and CSF to
differ
Brain Protection and Support
 Four Breaks in the BBB
 Portions of hypothalamus
 Secrete hypothalamic hormones
 Posterior lobe of pituitary gland
 Secretes hormones ADH and oxytocin
 Pineal glands
 Pineal secretions
 Choroid plexus
 Where special ependymal cells maintain blood–
CSF barrier
The Medulla Oblongata
 The Medulla Oblongata
 Allows brain and spinal cord to communicate
 Coordinates complex autonomic reflexes
 Controls visceral functions
 Nuclei in the Medulla
 Autonomic nuclei: control visceral activities
 Sensory and motor nuclei: of cranial nerves
 Relay stations: along sensory and motor pathways
The Medulla Oblongata
Figure 14–5a The Diencephalon and Brain Stem.
The Medulla Oblongata
Figure 14–5c The Diencephalon and Brain Stem.
The Cerebellum
 Functions of the Cerebellum
 Adjusts postural muscles
 Fine-tunes conscious and subconscious
movements
The Cerebellum
 Structures of the Cerebellum
 Purkinje cells
 Large, branched cells
 Found in cerebellar cortex
 Receive input from up to 200,000 synapses
 Arbor vitae
 Highly branched, internal white matter of cerebellum
 Cerebellar nuclei: embedded in arbor vitae:
– relay information to Purkinje cells
The Cerebellum
 Structures of the Cerebellum
 The peduncles
 Tracts link cerebellum with brain stem, cerebrum, and spinal
cord:
– superior cerebellar peduncles
– middle cerebellar peduncles
– inferior cerebellar peduncles
The Cerebellum
 Disorders of the Cerebellum
 Ataxia
 Damage from trauma or stroke
 Intoxication (temporary impairment)
 Disturbs muscle coordination
The Cerebellum
Figure 14–7a The Cerebellum.
The Cerebellum
Figure 14–7b The Cerebellum.
The Diencephalon
 Integrates sensory information and motor
commands
 Thalamus, epithalamus, and hypothalamus
 The pineal gland
 Found in posterior epithalamus
 Secretes hormone melatonin
The Diencephalon
 The Thalamus
 Filters ascending sensory information for primary
sensory cortex
 Relays information between basal nuclei and cerebral
cortex
 The third ventricle
 Separates left thalamus and right thalamus
 Interthalamic adhesion (or intermediate mass):
– projection of gray matter
– extends into ventricle from each side
The Diencephalon
 The Thalamus
 Thalamic nuclei
 Are rounded masses that form thalamus
 Relay sensory information to basal nuclei and
cerebral cortex
The Diencephalon
 The Hypothalamus
 Mamillary bodies
 Process olfactory and other sensory information
 Control reflex eating movements
 Infundibulum
 A narrow stalk
 Connects hypothalamus to pituitary gland
 Tuberal area
 Located between the infundibulum and mamillary bodies
 Helps control pituitary gland function
The Diencephalon
Figure 14–10a The Hypothalamus in Sagittal Section.
The Diencephalon
 Eight Functions of the Hypothalamus
 Provides subconscious control of skeletal muscle
 Controls autonomic function
 Coordinates activities of nervous and endocrine
systems
 Secretes hormones
 Antidiuretic hormone (ADH) by supraoptic nucleus
 Oxytocin (OT; OXT) by paraventricular nucleus
The Diencephalon
 Eight Functions of the Hypothalamus
 Produces emotions and behavioral drives
 The feeding center (hunger)
 The thirst center (thirst)
 Coordinates voluntary and autonomic functions
 Regulates body temperature
 Preoptic area of hypothalamus
 Controls circadian rhythms (day–night cycles)
 Suprachiasmatic nucleus
The Limbic System
 The Limbic System
 Is a functional grouping that
 Establishes emotional states
 Links conscious functions of cerebral cortex with autonomic
functions of brain stem
 Facilitates memory storage and retrieval
The Limbic System
 Components of the Limbic System
 Amygdaloid body
 Acts as interface between the limbic system, the
cerebrum, and various sensory systems
 Limbic lobe of cerebral hemisphere
 Cingulate gyrus
 Dentate gyrus
 Parahippocampal gyrus
 Hippocampus
The Limbic System
 Components of the Limbic System
 Fornix
 Tract of white matter
 Connects hippocampus with hypothalamus
 Anterior nucleus of the thalamus
 Relays information from mamillary body to
cingulate gyrus
 Reticular formation
 Stimulation or inhibition affects emotions (rage,
fear, pain, sexual arousal, pleasure)
The Limbic System
Figure 14–11a The Limbic System.
The Limbic System
Figure 14–11b The Limbic System.
The Limbic System
The Cerebrum
 The Cerebrum
 Is the largest part of the brain
 Controls all conscious thoughts and
intellectual functions
 Processes somatic sensory and motor
information
The Cerebrum
 Gray matter
 In cerebral cortex and basal nuclei
 White matter
 Deep to basal cortex
 Around basal nuclei
The Cerebrum
Figure 14–12c The Brain in Lateral View.
The Cerebrum
 Special Sensory Cortexes
 Visual cortex
 Information from sight receptors
 Auditory cortex
 Information from sound receptors
 Olfactory cortex
 Information from odor receptors
 Gustatory cortex
 Information from taste receptors
The Cerebrum
Figure 14–15a Motor and Sensory Regions of the Cerebral Cortex.
The Cerebrum
The Cerebrum
 The Left Hemisphere
 In most people, left brain (dominant hemisphere)
controls
 Reading, writing, and math
 Decision making
 Speech and language
 The Right Hemisphere
 Right cerebral hemisphere relates to
 Senses (touch, smell, sight, taste, feel)
 Recognition (faces, voice inflections)
The Cerebrum
Figure 14–16 Hemispheric Lateralization.
The Cerebrum
 Monitoring Brain Activity
 Brain activity is assessed by an
electroencephalogram (EEG)
 Electrodes are placed on the skull
 Patterns of electrical activity (brain waves) are
printed out
The Cerebrum
 Four Categories of Brain Waves
 Alpha waves
 Found in healthy, awake adults at rest with eyes closed
 Beta waves
 Higher frequency
 Found in adults concentrating or mentally stressed
 Theta waves
 Found in children
 Found in intensely frustrated adults
 May indicate brain disorder in adults
 Delta waves
 During sleep
 Found in awake adults with brain damage
The Cerebrum
Figure 14–17a-d Brain Waves.
The Cerebrum
 Synchronization
 A pacemaker mechanism
 Synchronizes electrical activity between
hemispheres
 Brain damage can cause desynchronization
 Seizure
 Is a temporary cerebral disorder
 Changes the electroencephalogram
 Symptoms depend on regions affected
Cranial Nerves
 12 pairs connected to brain
 Four Classifications of Cranial Nerves
 Sensory nerves: carry somatic sensory information,
including touch, pressure, vibration, temperature, and
pain
 Special sensory nerves: carry sensations such as
smell, sight, hearing, balance
 Motor nerves: axons of somatic motor neurons
 Mixed nerves: mixture of motor and sensory fibers
Cranial Nerves
Figure 14–18 Origins of the Cranial Nerves.
Cranial Nerves
 Optic Nerves (II)
 Primary function
 Special sensory (vision)
 Origin
 Retina of eye
 Pathway
 Optic canals of sphenoid
 Destination
 Diencephalon via optic chiasm
Cranial Nerves
 Optic Nerve Structures
 Optic chiasm
 Where sensory fibers converge
 And cross to opposite side of brain
 Optic tracts
 Reorganized axons
 Leading to lateral geniculate nuclei
Cranial Nerves
Figure 14–20 The Optic Nerve.
Cranial Nerves
 The Vagus Nerves (X)
 Primary function
 Mixed (sensory and motor)
 Widely distributed in thorax and abdomen
 Origins
 Sensory:
–
–
–
–
part of pharynx
auricle and external acoustic meatus
diaphragm
visceral organs of thoracic and abdominopelvic cavities
 Motor:
– motor nuclei in medulla oblongata
Cranial Nerves
 The Vagus Nerves (X)
 Pathway
 Jugular foramina
 Between occipital and temporal bones
 Destination
 Sensory:
– sensory nuclei and autonomic centers of medulla
oblongata
 Visceral motor:
– muscles of the palate and pharynx
– muscles of the digestive, respiratory, and cardiovascular
systems in thoracic and abdominal cavities
Cranial Nerves
Figure 14–26 The Vagus Nerve.
Cranial Nerves
Figure 14–26 The Vagus Nerve.
Cranial Nerves
 The Accessory Nerves (XI)
 Primary function
 Motor to muscles of neck and upper back
 Origin
 Motor nuclei of spinal cord and medulla oblongata
 Pathway
 Jugular foramina between occipital and temporal bones
 Destination
 Internal branch:
– voluntary muscles of palate, pharynx, and larynx
 External branch:
– sternocleidomastoid and trapezius muscles
Cranial Nerves
Cranial Nerves
Cranial Reflexes
 Cranial Reflexes
 Monosynaptic and polysynaptic reflex arcs
 Involve sensory and motor fibers of cranial nerves
 Clinically useful to check cranial nerve or brain
damage
Cranial Reflexes