Nervous System Flashcards
Nervous tissue is made up of just two principal types of cells:
- NEUROGLIA
- NEURONS
small cells that surround and wrap the more delicate
neurons
NEUROGLIA
nerve cells that are excitable (responsive to stimuli) and transmit electrical signals
NEURONS
is the master integrating and coordinating system, continuously monitoring and processing sensory information both from the external environment and from within the body
nervous system
Two primary divisions make up the nervous system:
- Central Nervous System (CNS)
- Peripheral Nervous System (PNS)
consisting of the brain and spinal cord
Central Nervous System (CNS)
include nerves, sensory receptors, and some clusters of neuron cell bodies
Peripheral Nervous System (PNS)
neuroglia or
glial cells
Neuroglia of the CNS include
- Astrocytes
- Microglial cells
- Ependymal cells
- Oligodendrocytes
The neuroglia found in the PNS include
Satellite cells
Schwann cells (neurolemmocytes)
are the most abundant CNS neuroglia
Astrocytes
are defensive cells in the CNS
Microglial cells
line cerebrospinal fluid–filled cavities
Ependymal cells
have processes that form myelin sheaths around CNS nerve fibers
Oligodendrocytes
Oligodendrocytes have processes that form ________________ around CNS nerve fibers
myelin sheaths
surround neurons in the PNS
Satellite cells and Schwann cells
form myelin in the PNS
Schwann cells
receptive regions
Dendrites
biosynthetic center and receptive region
Cell body
The nervous system has three overlapping functions:
- Sensory input
- Integration
- Motor output
In the PNS, clusters of neuron cell bodies are called
ganglia
The nervous system uses its millions of sensory receptors to monitor changes occurring both inside and outside the body. The gathered information is called
sensory input
The nervous system processes and interprets sensory input and decides what should be done at each moment—a process called
integration
The nervous system activates effector organs—the muscles and glands—to cause a response, called
motor output
what are the effector organs that the nervous system activates
muscles and glands
PNS includes
cranial nerves and spinal nerves
communication lines between the CNA and the rest of the body
Peripheral Nervous System (PNS)
sensory (afferent) division
somatic and visceral sensory nerve fibers
includes somatic and visceral sensory nerve fibers
sensory (afferent) division
conducts impulses from receptors to the CNS
sensory (afferent) division
includes motor nerve fibers
motor (efferent) division
motor (efferent) division includes
motor nerve fibers
conducts impulses form the CNS to effectors
motor (efferent) division
somatic motor is
voluntary
somatic nervous system includes
somatic motor
autonomic nervous system includes
visceral motor
visceral motor is
involuntary
conducts impulses from the CNS to the skeletal muscles
somatic nervous system
conducts impulses from the CNS to cardiac muscles, smooth muscles, and glad
autonomic nervous system
mobilizes body systems during activity
sympathetic division
- conserves energy
- promotes house-keeping functions during rest
parasympathetic division
A junction that mediates information transfer from one neuron to the next or from a neuron to an effector cell
Synapse
Types of Synapses:
A. Axodendritic Synapse
B. Axosomatic Synapse
C. Axoaxonal Synapse
the neuron conducting impulses toward the synapse
presynaptic neuron
the neuron transmitting the electrical signal away from the synapse
postsynaptic neuron
consist of gap junctions like those found between certain
other body cells
Electrical Synapses
Electrical Synapses contain protein channels, called
connexons
intimately connect the cytoplasm of adjacent neurons and allow ions and small molecules to flow directly from one neuron to the next
connexons
transmission across these synapses is very rapid
Electrical Synapses
In Electrical Synapses communication may be
unidirectional or bidirectional
communication may be unidirectional or bidirectional
Electrical Synapses
Found in regions of the brain responsible for certain stereotyped movements
Electrical Synapses
Electrical Synapses are found in regions of the brain responsible for certain stereotyped movements such as
normal jerky movements of the eyes
a brain region intimately involved in emotions and memory
hippocampus
also occur in axoaxonal synapses in the hippocampus, a
brain region intimately involved in emotions and memory.
Electrical Synapses
Allow the flow of ions between neurons
Chemical Synapses
Specialized to allow the release and reception of chemical
neurotransmitters
Chemical Synapses
Two parts of chemical synapse:
a. axon terminal of the presynaptic neuron
b. neurotransmitter receptor region
Classification of Neurotransmitters by Function:
- Effects: Excitatory Versus Inhibitory
- Actions: Direct Versus Indirect
are those that bind to and open ion channels
Direct Neurotransmitters
These neurotransmitters provoke rapid responses
in postsynaptic cells by altering membrane potential
Direct Neurotransmitters
promote broader, longer-lasting effects by acting through
intracellular second messenger molecules, typically via G protein pathway
Indirect Neurotransmitters
Indirect Neurotransmitters promote broader, longer-lasting effects by acting through intracellular __________________________ molecules, typically via G protein pathway
second messenger
promote broader, longer-lasting effects by acting through
intracellular second messenger molecules, typically via _____________________________
G protein pathway
Examples of Indirect Neurotransmitters
biogenic amines, neuropeptides, and dissolved Gases
the input travels along one pathway to a specific destination
Serial processing
the input travels along several different pathways to be integrated in different CNS regions
Parallel processing
the whole system works in a predictable all-or-nothing
manner
Serial processing
examples of serial processing are
spinal reflexes
In Serial processing, the whole system works in a predictable
all-or-nothing manner
Reflexes are rapid, automatic responses to stimuli, in which a particular stimulus always causes the same response.
Serial processing
Reflexes occur over neural pathways called
reflex arcs
five essential components of reflex arcs
- receptor
- sensory neuron
- Integration center
- Motor neuron
- effector
inputs are segregated into many pathways, and different parts of the neural circuitry deal simultaneously with the information delivered by each pathway.
Parallel processing
Parallel processing is
Not repetitious
is the ability to retain and recall information
Memory
Types of Memory:
- Sensory Memory (Working memory)
- Short-term Memory
- Long-term Memory
Memories are stored throughout the
cerebral cortex
Memories are stored throughout the cerebral cortex in pathways known as ________________
memory traces
one of the main areas in recalling long-term memory
hippocampus
shortest-term element of memory
working memory
is the ability to retain impressions of sensory information after the original stimuli have ended.
working memory
A cognitive system that holds and processes information
working memory
working memory involves
frontal lobes
Can hold only 7-12 pieces of information at a time
Short term Memory
Memory disappear unless an effort, such as repetition is
made, to put them into a more permanent .
Short term Memory
In short-term meory, memory disappear unless an effort, such as _____________ is made, to put them into a more permanent .
repetition
Capable of holding vast amounts of information
Long Term Memory
The processing of information that converts short-term memory into long-term memory is known as
consolidation
can take varying period of time from seconds to minutes
Long Term Memory
Islands of gray matter buried deep within the white matter of the cerebral hemispheres
Basal nuclei
regulate voluntary motor activities by modifying
instructions (particularly in relation to starting or stopping movement) sent to the skeletal muscles by the primary motor cortex
Basal nuclei
“emotional visceral brain” found in hypothalamus
LIMBIC SYSTEM
Limbic System evokes
thirst, appetite, sex, pain, and pleasure
Limbic system is the ______________________________ found in hypothalamus
“emotional visceral brain”
Limbic system is the “emotional visceral brain” found in
hypothalamus
Parts of Limbic system especially important in emotions:
- amygdala
- cingulate gyrus
deals with memory and anger, danger, and fear responses; helps to access memories
amygdala
plays a role in expressing emotions via gestures, and resolves mental conflict
cingulate gyrus
Puts emotional responses to odors – e.g., skunks smell bad
cingulate gyrus
large, cauliflower-like
CEREBELLUM
projects dorsally from under the occipital lobe of the cerebrum
CEREBELLUM
has two hemispheres and a convoluted surface
CEREBELLUM
CEREBELLUM has
two hemispheres and a convoluted surface
provides the precise timing for skeletal muscle activity and controls our balance and equilibrium
CEREBELLUM
Responsible for smooth and coordinated muscle movement
CEREBELLUM
Plays its role less well when it is sedated by alcohol
CEREBELLUM
Homeostatic imbalance of Cerebellum: movements become clumsy and disorganized a condition called
ataxia
Protection of the Central Nervous System
- Cerebrospinal fluid
- Blood brain barrier
Types of Meninges
- dura mater
- arachnoid
- pia mater
Double-layered external covering
dura mater
attached to surface of the skull
periosteum
outer covering of the brain
Meningeal layer
Folds inward in several areas
Dura mater
- Middle layer (meninx)
- Web-like
Arachnoid layer
- Internal layer
- Clings to the surface of the brain
Pia mater
is between Arachnoid and Pia mater
Cerebrospinal fluid
Cerebrospinal fluid is between
Arachnoid and Pia mater
contains more Na+, Cl-, and H+ than does blood plasma, and less Ca2+ and K+
CEREBROSPINAL FLUID
Cerebrospinal Fluid is continually formed by the
choroid plexus
Formed by the choroid plexus
Cerebrospinal Fluid
Forms a watery cushion to protect the brain
Cerebrospinal Fluid
Circulated in arachnoid space, ventricles, and central canal of the spinal cord
Cerebrospinal Fluid
(2) in each hemisphere
lateral ventricles
in slit between thalamic halves
third ventricle
between brain stem and cerebellum
fourth ventricle
channel between lateral -> 3rd ventricle
Foramen of Monro
channel between 3rd ventricle -> 4th ventricle
cerebral aqueduct
4th ventricle -> other spaces
median & lateral apertures -
Clusters of capillaries that form tissue fluid filters, which hang from the roof of each ventricle
Choroid Plexuses
Have ion pumps that allow them to alter ion concentrations of the CSF
Choroid Plexuses
Help cleanse CSF by removing wastes
Choroid Plexuses
The brain and spinal cord are covered and protected by
three connective tissue membranes called
meninges
Nerves and ganglia outside the central nervous system
PERIPHERAL NERVOUS SYSTEM
bundle of neuron fibers
Nerve
are bundled by connective tissue
Neuron fibers
Endoneurium surrounds each fiber
Nerve
Groups of fibers are bound into fascicles by
perineuriuma
surrounds each nerve fiber
Endoneurium
Fascicles are bound together by
epineurium
Classification of Nerves
- Mixed nerves
- Afferent (sensory) nerves
- Efferent (motor) nerves
both sensory and motor fibers
Mixed nerves
carry impulses toward the CNS
Afferent (sensory) nerves
carry impulses away from the CNS
Efferent (motor) nerves
12 pairs of nerves that mostly serve the head and neck
Cranial Nerves
In Cranial Nerves, most are _____________, but three are
____________ only
mixed nerves; sensory
sensory for smell
Olfactory nerve
sensory for vision
Optic nerve
motor fibers to eye muscles (III)
Oculomotor nerve
motor fiber to eye muscles (IV)
Trochlear
sensory for the face
Trigeminal nerve
motor fibers to chewing muscles
Trigeminal nerve
motor fibers to eye muscles (VI)
Abducens nerve
sensory for taste
Facial nerve
motor fibers to the face
Facial nerve
sensory for balance and hearing
Vestibulocochlear nerve
sensory for taste; motor fibers to the pharynx
Glossopharyngeal nerve
sensory and motor fibers for pharynx, larynx, and viscera
Vagus nerves
motor fibers to neck and upper back
Accessory nerve
motor fibers to tongue
Hypoglossal nerve
Form the superior part of the brain and make up 83% of its mass
CEREBRAL HEMISPHERES
ridges of the cortex
gyrus (gyri)
groove or valley in the cortex
sulcus (sulci)
long deeper groove
fissure
Deep sulci divide the hemispheres into several lobes:
Frontal, parietal, temporal, & occipital
separates the frontal and parietal lobes
Central sulcus
separates the parietal and occipital lobes
Parieto-occipital sulcus
separates the parietal and temporal lobes
Lateral sulcus
border the central sulcus
precentral gyrus and postcentral gyrus
superficial gray matter; accounts for 40% of the mass of the brain
cortex
It enables sensation, communication, memory, understanding, and voluntary movements
CEREBRAL CORTEX
Each hemisphere acts contralaterally (controls the
opposite side of the body)
CEREBRAL CORTEX
controls the opposite side of the body
contralaterally
The three types of functional areas of the cerebral cortex are:
– Motor areas
– Sensory areas
- Association areas
control voluntary movement
Motor areas
conscious awareness of sensation
Sensory areas
integrate diverse information
Association areas
Located in the precentral gyrus
Primary Motor Cortex
Primary Motor Cortex is located in the
precentral gyrus
Composed of pyramidal cells whose axons make up the corticospinal tracts
Primary Motor Cortex
Allows conscious control of precise, skilled, voluntary movements
Primary Motor Cortex
Controls learned, repetitious, or patterned motor skills
PREMOTOR CORTEX
Coordinates simultaneous or sequential actions
PREMOTOR CORTEX
Involved in the planning of movements
PREMOTOR CORTEX
Sensory Areas
- Primary somatosensory cortex
- Somatosensory association cortex
- Wernicke’s area
- Visual areas
- Auditory areas
Located in the postcentral gyrus
Primary Somatosensory Cortex
Receives information from the skin and skeletal muscles
Primary Somatosensory Cortex
Exhibits spatial discrimination
Primary Somatosensory Cortex
Integrates sensory information
Somatosensory Association Cortex
Forms comprehensive understanding of the stimulus
Somatosensory Association Cortex
Determines size, texture, and relationship of parts
Somatosensory Association Cortex
Seen on the extreme posterior tip of the occipital lobe
Primary visual cortex
Receives visual information from the retinas
Primary visual cortex
Surrounds the primary visual cortex
Visual association area
Interprets visual stimuli (e.g., color, form, and movement)
Visual association area
Located at the superior margin of the temporal lobe
Primary auditory cortex
Receives information related to pitch, rhythm, and loudness
Primary auditory cortex
Located posterior to the primary auditory cortex
Auditory association area
Stores memories of sounds and permits perception of
sounds
Auditory association area
ability sound out new words/sounds
Wernicke’s area
Located in the anterior portion of the frontal lobe
Prefrontal Cortex
Involved with intellect, cognition, recall, and personality
Prefrontal Cortex
Necessary for judgment, reasoning, persistence, and conscience
Prefrontal Cortex
closely linked to the limbic system (emotional part of the
brain)
Prefrontal Cortex
Language Areas
- Wernicke’s area
- Broca’s area
Located in a large area surrounding the left (or language dominant) lateral sulcus
Language Areas
involved in sounding out unfamiliar words
Wernicke’s area
speech preparation and production
Broca’s area
Present in one hemisphere (usually the left)
Broca’s area
A motor speech area that directs muscles of the tongue
Broca’s area
Is active as one prepares to speak
Broca’s area
each hemisphere has abilities not shared with its partner
Lateralization
designates the hemisphere dominant for language
Cerebral dominance
“controls” or involved in language, math, and logic
Left hemisphere
“controls” or involved in visualspatial skills, emotion, and artistic skills
Right hemisphere
Consists of deep myelinated fibers and their tracts
Cerebral White Matter
It is responsible for communication between:
– The cerebral cortex and lower CNS center, and areas of the cerebrum
Cerebral White Matter
Central core of the forebrain that encloses the third ventricle
Diencephalon
Diencephalon consists of three paired structures:
- thalamus
- hypothalamus
- epithalamus (w/ pineal gland)
Paired, egg-shaped masses that form the superolateral walls of the third ventricle
Thalamus
Thalamus Contains four groups of nuclei
anterior, ventral, dorsal, and posterior
Afferent impulses from all senses converge and synapse in the
Thalamus
All inputs ascending to the cerebral cortex pass through
the
Thalamus
Plays a key role in mediating sensation, motor activities, cortical arousal, learning, and memory
Thalamus
Located below the thalamus
Hypothalamus
it caps the brainstem and forms the inferolateral walls of the third ventricle
Hypothalamus
Small, paired nuclei bulging anteriorly from the hypothalamus
Mammillary bodies
Relay station for olfactory pathways
Mammillary bodies
stalk of the hypothalamus; connects to the pituitary gland
Infundibulum
Main visceral control center of the body
Infundibulum
Regulates blood pressure, rate and force of heartbeat, digestive tract motility, rate and depth of breathing, and many other visceral activities
Hypothalamus
Is involved with perception of pleasure, fear, and rage
Hypothalamus
Controls mechanisms needed to maintain normal body temperature
Hypothalamus
Regulates feelings of hunger and satiety
Hypothalamus
Regulates sleep and the sleep cycle
Hypothalamus
Most dorsal portion of the diencephalon; forms roof of the
third ventricle
Epithalamus
extends from the posterior border and secretes melatonin
Pineal Gland
a hormone involved with sleep regulation, sleep-wake cycles, and mood
Pineal Gland
Brain Stem Consists of three regions:
- Midbrain
- Pons
- medulla oblongata
Similar to spinal cord but contains embedded nuclei
Brain Stem
Controls automatic behaviors necessary for survival
Brain Stem
Provides the pathway for tracts between higher and lower brain centers
Brain Stem
Associated with 10 of the 12 pairs of cranial nerves
Brain Stem
Located between the diencephalon and the pons
Midbrain
Midbrain structures include:
- Cerebral peduncles
- Cerebral aqueduct –
- Various Nuclei
two bulging structures that contain descending pyramidal motor tracts from the cortex
Cerebral peduncles
hollow tube that connects the third and fourth ventricles
Cerebral aqueduct
Midbrain Nuclei includes:
- Corpora quadrigemina
- Superior colliculi
- Inferior colliculi
- Substantia nigra
four domelike protrusions of the dorsal midbrain
Corpora quadrigemina
visual reflex centers
Superior colliculi
auditory relay centers
Inferior colliculi
functionally linked to basal nuclei
Substantia nigra
area affected by Parkinson’s disease
Substantia nigra
Bulging brainstem region between the midbrain and the
medulla oblongata
Pons
Contains nuclei of the reticular formation which is
involved in general arousal of the brain
Pons
Fibers of the pons:
- Connect higher brain centers and the spinal cord
- Relay impulses between the motor cortex and the
cerebellum
Three paired fiber tracts that connect the cerebellum to the
brain stem
Cerebellar Peduncles
All fibers in the cerebellum are
ipsilateral (same side)
3 Cerebellar Peduncles
- Superior peduncles
- Middle peduncles
- Inferior peduncles
connect the cerebellum to the midbrain
Superior peduncles
connect the pons to the cerebellum
Middle peduncles
connect the medulla to the cerebellum
Inferior peduncles
Most inferior part of the brain stem
Medulla Oblongata
Medulla Oblongata has two major tracts of nerve fibers with motor info:h
- Pyramids
- Decussation of the pyramids
two longitudinal ridges formed by corticospinal tracts
Pyramids
crossover points to other side of spinal cord for the corticospinal tracts
Decussation of the pyramids
Medulla Nuclei
- Inferior olivary nuclei
- Vestibular nuclear complex
- Ascending sensory tract nuclei (nucleus cuneatus and
nucleus gracilis) - Cardiovascular control center
- Respiratory centers
gray matter that relays sensory information
Inferior olivary nuclei
synapses that mediate and maintain equilibrium
Vestibular nuclear complex
adjusts force and rate of heart contraction
Cardiovascular control center
control rate and depth of breathing
Respiratory centers
Located dorsal to the pons and medulla
Cerebellum
rotrudes under the occipital lobes of the cerebrum
Cerebellum
Makes up 11% of the brain’s mass
Cerebellum
Provides precise timing and appropriate patterns of skeletal
muscle contraction
Cerebellum
Cerebellar activity occurs
subconsciously
receives impulses of the intent to initiate voluntary muscle contraction
Cerebellum
“inform” the cerebellum of the body’s condition
Proprioceptors and visual signals
calculates the best way to perform a movement
Cerebellar cortex
A “blueprint” of coordinated movement is sent to the
cerebral motor cortex
impulse generating and conducting region
axon
myelin sheath gap
node of ranvier
secretory region
axon terminals
