Chapter 11 - Nervous System continued Flashcards
Central nervous system (CNS):
- Consists of brain and spinal cord.
- Brain is largest and most complex portion of nervous
system - Brain controls sensation, perception, movement, thinking
- Brain consists of 2 cerebral hemispheres, diencephalon,
brainstem, cerebellum - Brainstem connects the brain to the spinal cord
- Both brain and spinal cord connect to the peripheral
nervous system (PNS) by way of peripheral nerves - Meninges
Meninges
membranes that protect brain and spinal cord;
lie between bone and soft tissues of nervous system
The meninges:
* Membranes that protect brain and spinal cord
* Consist of 3 layers which are…?
Dura Mater
Arachnoid Mater
Pia Mater
Dura Mater
- Outer layer
- Tough, dense connective tissue
- Dural sinuses
- Epidural space
Arachnoid mater:
- Middle layer; web-like
- Subarachnoid space contains cerebrospinal fluid (CSF)
Pia Mater
- Inner layer; attached to surface of brain, spinal cord
- Contains blood vessels and nerves
- Nourishes CNS
CSF is produced in 4…
ventricles, interconnected cavities
within cerebral hemispheres, and brainstem
-Ventricles are continuous with the central canal of the spinal
cord
what are the 4 Ventricles
- 2 Lateral ventricles (called the first and second ventricles)
- Third ventricle
- Fourth ventricle
Interventricular foramina
connect third to lateral ventricles
Cerebral aqueduct
connects third and fourth ventricles
Cerebrospinal Fluid
- Secreted by the choroid plexuses, special capillaries of
pia mater covered by ependymal cells - Selective transfer of substances from the blood to form
CSF - Nutritive and protective of CNS neurons
- Helps maintain stable ionic concentrations in the CNS
- Circulates in ventricles, central canal of spinal cord, and
subarachnoid space - After exchanging substances, CSF is absorbed by the
arachnoid granulations - Volume is about 140 mL at any time
The brain contains centers for/performs the following
functions…?
- Neural centers for sensory function
- Sensations and perceptions
- Motor commands to skeletal muscles
- Higher mental functions, such as memory, reasoning
- Neural centers for coordinating muscular movement
- Neural centers for regulating visceral activities
- Personality
Neural tube gives rise to…?
CNS
Brain forms from 3 Vesicles (cavaties)
- Forebrain (prosencephalon)
- Midbrain (mesencephalon)
- Hindbrain (rhombencephalon)
3 vesicles facts
-Forebrain divides into the telencephalon and diencephalon
-Mesencephalon persists
-Hindbrain divides into metencephalon and myelencephalon
-These 5 cavities persist in mature brain as ventricles and tubes that
connect them:
* Forebrain becomes cerebrum, basal nuclei, and diencephalon
* Mesencephalon remains as midbrain
* Hindbrain becomes cerebellum, pons, and medulla oblongata
10
what are the Major portions of the adult brain
- Cerebrum
- Diencephalon
- Cerebellum
- Brainstem
Cerebrum is the _______ part of the brain
Largest
Structures of the Cerebrum
Cerebral hemispheres: 2 halves, separated by falx
cerebri
* Corpus callosum: Connects cerebral hemispheres
* Gyri: Ridges or convolutions
* Sulci: Shallow grooves in surface; example: Central
sulcus
* Fissures:
* Deep grooves in surface
* Longitudinal: separates the cerebral hemispheres
* Transverse: separates cerebrum from cerebellum
What are the 5 lobes of the cerebral of hemispheres?
- Frontal lobe
- Parietal lobe
- Temporal lobe
- Occipital lobe
- Insula (Island of Reil): Deep within lateral sulcus
4 of the lobes are named for the bones that they underlie
Cerebral Cortex:
- Thin layer of gray matter, which
makes up outermost layer of all outer
lobes of the cerebrum - Contains almost 75% of neuron cell
bodies in nervous system
White Matter of Cerebrum:
- Lies under cerebral cortex
- Makes up most of cerebrum
- Contains bundles of myelinated axons
that connect neuron cell bodies in
cerebral cortex to other portions of
nervous system
What is the Cerebral Cortex responsible for?
Higher Mental Functions
What are the functions of the Cerebral Cortex?
- Interpreting impulses from sensory organs
- Initiating voluntary movements
- Storing information as memory
- Retrieving stored information
- Reasoning
- Seat of intelligence and personality
-The cerebral cortex can be divided into sensory, association
and motor areas; some overlap exists
-Each area contains a group of neurons working together to
perform a particular function
Cutaneous sensory area: (sensory)
- Parietal lobe
- Interprets sensations on skin
Sensory speech area (Wernicke’s area): (sensory)
- Temporal/parietal lobe, usually left hemisphere
- Understanding and formulating language
Visual area: (sensory)
Occipital lobe
* Interprets vision
Auditory area: (sensory)
- Temporal lobe
- Interprets hearing
Sensory area for taste: (sensory)
- Near base of the central sulcus
- Includes part of insula
Sensory area for smell: (sensory)
Arises from centers deep within temporal lobes
Frontal lobe association areas: (assosiation area of the cortex)
- Concentrating, planning, complex problem solving
- Emotional behavior, judging consequences of behavior
Parietal lobe association areas: Association Areas of the Cortex
- Understanding speech
- Choosing words to express thoughts and feelings
Temporal lobe association areas: Association Areas of the Cortex
- Interpret complex sensory experiences (understanding speech,
reading) - Store memories of visual scenes, music, and complex patterns
Occipital lobe association areas: Association Areas of the Cortex
Analyze and combine visual images with other sensory experiences
Insula: Association Areas of the Cortex
Translating sensory information into proper emotional responses
Primary motor areas (motor cortex): Motor Areas of the Cortex
- Frontal lobes
- Control voluntary muscles
- Most nerve fibers cross over in brainstem
Broca’s area: Motor Areas of the Cortex
- Frontal lobes
- Control voluntary muscles
- Most nerve fibers cross over in brainstem
Broca’s area: - Anterior to primary motor cortex
- Usually in left hemisphere
- Controls muscles needed for speech
Frontal eye field: Motor Areas of the Cortex
Frontal eye field:
* Above Broca’s area
* Controls voluntary movements of eyes and eyelids
The ____ hemisphere is dominant in most people
LEFT
Dominant hemisphere controls:
- Language skills of speech, writing, reading
- Verbal, analytical, and computational skills
Nondominant hemisphere controls
- Nonverbal tasks
- Motor tasks involving orientation in space
- Understanding and interpreting musical and visual
patterns - Provides emotional and intuitive thought processes
What is the Diencephalon between?
cerebral hemispheres and
above the brainstem
Diencephalon facts
Surrounds the third ventricle
* Composed of gray matter
* Portions of the diencephalon:
* Thalamus
* Hypothalamus
* Optic tracts
* Optic chiasma
* Infundibulum
* Posterior pituitary
* Mammillary bodies
* Pineal gland
Diencephalon
Thalamus
- Gateway for sensory impulses ascending to cerebral cortex
- Receives all sensory impulses (except for sense of smell)
- Channels impulses to appropriate part of cerebral cortex for interpretation
Diencephalon
Hypothalamus
- Maintains homeostasis by regulating visceral activities, such as heart rate,
blood pressure, body temperature, water and electrolyte balance, hunger,
body weight, movement and glandular secretion in digestive tract, sleep and
wakefulness, pituitary gland function - Links nervous and endocrine systems
Diencephalon
Limbic System
- Consists of several structures in various parts of brain, including diencephalon
- Controls emotional responses, feelings, behavior oriented toward survival
- Reacts to potentially life-threatening upsets (physical or psychological)
Brainstem
- Connects brain to the spinal cord.
- Consists of:
- Midbrain
- Pons
- Medulla oblongata
- Contains nerve fiber tracts and gray matter masses
Midbrain
Short section of brainstem
* Lies between diencephalon and pons
* Contains bundles of fibers that join lower parts of
brainstem and spinal cord with higher part of brain
Midbrain
Cerebral aqueduct:
Connects 3rd to 4th ventricle
Midbrain
Cerebral peduncles:
Main motor pathways that connect
cerebrum to lower portions of nervous system
Midbrain
Corpora quadrigemina:
Centers for visual and auditory
reflexes
Midbrain
Red Nucleus
role in postural reflexes
Pons
- Rounded bulge on underside of brainstem
- Between midbrain and medulla oblongata
- Relays nerve impulses between medulla oblongata and
cerebrum - Relays impulses from cerebrum to cerebellum
- Helps regulate rhythm of breathing
Medulla oblongata:
- Enlarged continuation of spinal cord
- Conducts ascending and descending impulses between
brain and spinal cord - Contains cardiac, vasomotor, and respiratory control
centers - Contains various nonvital reflex control centers (coughing,
sneezing, swallowing, and vomiting) - Injuries are often fatal
Reticular Formation:
- Also called Reticular Activating System
- Complex network of nerve fibers scattered throughout
brainstem - Extends into the diencephalon
- Connects to centers of hypothalamus, basal nuclei,
cerebellum, and cerebrum with ascending and descending
tracts - Filters incoming sensory information, passing some to
cerebral cortex, and discarding unimportant information - Arouses cerebral cortex into state of wakefulness
- Decreased activity causes sleep
What are the 2 types of sleep?
Non-rapid Eye Movement (Non-REM) Sleep:
Rapid Eye Movement (REM) Sleep:
Non-rapid Eye Movement (Non-REM) Sleep:
- Slow wave sleep
- Person is tired
- Decreasing activity of reticular formation
- Restful and dreamless
- Reduced blood pressure and respiratory rate
- 3 stages, ranging from light to heavy
- Alternates with REM sleep
Rapid Eye Movement (REM) Sleep:
- Called paradoxical sleep, because some areas of brain are active
- Heart and respiratory rates irregular
- Dreaming occurs
Sleep is a…?
normal, recurring, and reversible state of unconsciousness
characterized in part by limited sensory input and inhibited skeletal muscle
activity
Cerebellum
- Inferior to occipital lobes
- Dorsal to pons and medulla oblongata
- Two hemispheres separated by falx cerebelli
- Vermis connects hemispheres
- Cerebellar cortex (gray matter)
- Arbor vitae (white matter)
- Cerebellar peduncles
- Dentate nucleus (largest nucleus)
- Integrates sensory information concerning position of body parts
- Coordinates skeletal muscle activity
- Maintains posture
- Recent studies suggest other possible roles for the cerebellum. These include
interaction with other parts of cerebral cortex, such as the limbic system and
the auditory areas
Spinal Cord:
- Slender column of nervous tissue continuous with brain
and brainstem - Extends downward through vertebral canal
- Begins at the foramen magnum and terminates at the first
and second lumbar vertebrae (L1 to L2) space - Consists of 31 segments; each gives rise to a pair of
spinal nerves - Spinal nerves are grouped according to the level of the
vertebra with which they are associated - Within each group, the pairs of nerves are numbered in
sequence from superior to inferior
What is the schematic of Reflex Arc?
Receptor to Central Nervous System to Effector
Monosynaptic (stretch) reflex:
- Contains 2 neurons, sensory and motor
- Has only 1 synapse in spinal cord
- Example: Patellar or knee-jerk reflex
- Helps maintain an upright posture
Withdrawal Reflex:
- Occurs when person touches or steps on something painful (stove,
tack) - Prevents or limits tissue damage, by removing limb from painful
stimulus - Polysynaptic: contains sensory neuron, interneuron, motor neuron
- Reciprocal innervation: flexors contract, extensors are inhibited
Crossed Extensor Reflex:
- During withdrawal reflex, flexors on affected (ipsilateral)
side contract, and extensors are inhibited - At same time, extensors on opposite (contralateral) side
contract, flexors are inhibited - Also shifts body weight, so person remains upright
Peripheral Nervous System (PNS):
Consists of nerves that connect CNS to other body parts;
PNS includes
Cranial nerves arise from…
the brain
Spinal Nerves arise from…
the spinal cord
Subdivisions of the PNS :
- Somatic nervous system: cranial and spinal nerves that connect
CNS to the skin and skeletal muscles (conscious activities) - Autonomic nervous system: cranial and spinal nerves that
connect CNS to viscera (subconscious activities)
Somatic nervous system:
cranial and spinal nerves that connect
CNS to the skin and skeletal muscles (conscious activities)
Autonomic nervous system:
cranial and spinal nerves that
connect CNS to viscera (subconscious activities)
Structure of Peripheral Nerves
Nerves are bundles of axons
Nerve “fibers” are axons
What are the 3 connective tissue coverings
Endoneurium
Perineurium
Epineurium
Endoneurium
Loose connective tissue that surrounds
individual axons
Perineurium
Loose connective tissue that surrounds
fascicles
Epineurium
Dense connective tissue that surrounds a
group of fascicles
Nerve Fiber Classification
Classification by Function
- Sensory nerves:
- Conduct impulses into brain or spinal cord
- Motor nerves:
- Conduct impulses to muscles or glands
- Mixed nerves:
- Contain both sensory and motor nerve fibers
- Most nerves are mixed nerves
- All spinal nerves are mixed nerves (except the first pair
Nerve Fiber Classification
Classification by origination:
- Cranial nerves: Originate from brain
- Spinal nerves: Originate from spinal cord
Cranial Nerves:
- 12 pairs on underside of brain
- Most are mixed nerves
- Some are sensory, associated with special senses
- Some are primarily motor, innervate muscles or
glands - Most are attached to the brainstem, with 2
exceptions - First pair has fibers that start in the nasal cavity
- Second pair originates in eyes, fibers synapse in thalamus
- Cranial nerves are numbered with Roman numerals
(I to XII), from anterior to posterior (for the two pairs
associated with the cerebrum), and from superior to
inferior (for the remaining pairs)
Spinal Nerves
All are mixed nerves, except first pair (which is entirely motor)
Originate from spinal cord
31 pairs of spinal nerves:
* 8 cervical nerves, (C1 to C8)
* 12 thoracic nerves (T1 to T12)
* 5 lumbar nerves (L1 to L5)
* 5 sacral nerves (S1 to S5)
* 1 coccygeal nerve (Co)
Cauda equina: Formed by descending roots of lumbar, sacral,
and coccygeal nerves
Dermatome: An area of skin innervated by the sensory nerve
fibers of a particular spinal nerve (in all spinal nerves below C1)
Cauda equina:
Formed by descending roots of lumbar, sacral,
and coccygeal nerves
Dermatome
An area of skin innervated by the sensory nerve
fibers of a particular spinal nerve (in all spinal nerves below C1)
Autonomic Nervous System (ANS):
- An efferent (motor) part of the peripheral nervous system
(PNS) - Functions without conscious effort
- Controls visceral activities
- Regulates smooth muscle, cardiac muscle, and glands
- Helps maintain homeostasis
- Helps body respond to stress
- Prepares body for exercise, intense physical activity
what are the 2 divisions of the autonomic nervous system:
sympathetic and parasympathetic division
Sympathetic division:
- Prepares body for “fight or flight” situations
- Most active under energy-requiring, stressful, emergency situations
Parasympathetic division:
Prepares body for “rest and digest” activities
* Most active under resting, non-stressful conditions
Most organs receive input from both divisions
Life-Span Changes
- Brain cells begin to die before birth, due to apoptosis, a form of normal
programmed cell death - Over average lifetime, brain shrinks 10%
- More gray matter than white matter is lost with aging
- Many cells die in temporal lobes, but few in brainstem
- By age 90, frontal cortex has lost half its neurons
- Number of dendritic branches in cerebral cortex decreases
- Decreased levels of neurotransmitters
- Action potentials propagation rate declines by 5 to 10%
- Fading memory
- Slowed responses and reflexes
- Increased risk of fainting, falling
- Changes in sleep patterns that result in fewer sleeping hours
