Exam 3 Flashcards
(164 cards)
1
Q
Afferent
A
Toward CNS
2
Q
Efferent
A
Away from CNS
3
Q
Sensory
A
Signals picked up by sensory receptors (afferent)
4
Q
Motor
A
Signals carried away from the CNS (efferent)
5
Q
Somatic
A
skin, skeletal musculature, bones
6
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Visceral
A
digestive tube, lungs, heart, bladder, etc.
7
Q
Sensory input
A
receptors monitor stimuli inside and outside the body
8
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Integration
A
processes, interprets and assimilates experiences
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Motor output
A
Responds; muscle contraction, glandular secretion
10
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Functions of Nervous System
A
Sensory input, integration, motor output
11
Q
CNS
A
brain and spinal cord
12
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PNS
A
Cranial and spinal nerves, ganglia
13
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Sensory (Afferent signals)
A
Picked up by sensory receptors in the PNS and carried to the CNS
14
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Motor (Efferent signals)
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Carried away from the CNS to innervate muscles and glands
15
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Nuclei
A
Clusters of neuron bodies in the CNS
16
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Ganglia
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Clusters of neuron bodies in PNS
17
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Tracts
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Bundles of axons in CNS
18
Q
Fibers
A
Bundles of axons in PNS
19
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Gray matter
A
Short nonmyelinated interneurons, cell bodies of interneurons and motor neurons, neuroglia
20
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White matter
A
Fiber tracts of myelinated and nonmyelinated axons, neuroglia
21
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Somatic Sensory
A
Receives sensory information from skin, fascia, joints, skeletal muscles, special senses
22
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Visceral Sensory
A
Receives sensory information from viscera
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Somatic Motor
A
“Voluntary nervous system: innervates skeletal muscle
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Visceral Motor
A
“Involuntary” nervous system: innervates cardiac muscle, smooth muscle, glands
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Glials cells
Found in CNS/PNS, capable of mitosis, protect and nourish neurons, provide organized and supporting framework, more abundant than neurons, not capable of impulse transmission
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Astrocytes
Star shape
Most abundant of glial cells
Connect neurons to blood vessels, control flow of substances, control chemical composition, provide framework and support, replace neurons, resynthesize neurotransmitter, regulate neuron connect in the fetal brain
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Ependymal cells
Cuboidal epithelial cells found in ventricles/central canal of the spinal cord, have basal projections to contact other glial cells, have cilia to help circulate CSF, form choroid plexus along with blood vessels, produce CSF
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Microglia
Small cells with projections, not abundant, do not originate in nervous tissue, modified WBC, phagocytic activity: remove debris
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Oligodendrocytes
Large cells with globular bodies and slender projections, form myelin sheaths in axons for insulation, projection and nourishment. One cell can wrap around multiple axons
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Satellite cells
Flattened cells around neuronal body in ganglia, regulate nutrient and waste exchange, SIMILAR IN FUNCTION TO ASTROCYTES
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Neurolemmocytes
Surround axons to insulate, protect and nourish; form myelin sheaths. SIMILAR IN FUNCTION TO OLIGODENDROCYTES
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STRUCTURAL CLASSIFICATION OF NEURONS
Unipolar, bipolar, multipolar
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Unipolar neuron
typical sensory neuron
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Bipolar neuron
rare, found in retina, nose, inner ear
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Multipolar neuron
most common type, motor and interneurons, cell body mostly in CNS
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FUNCTIONAL CLASSIFICATION OF NEURONS
Sensory, motor, interneurons
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Sensory neurons
Originate in sensory receptors, respond to stimuli, travel to CNS
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Motor neurons
Originate in CNS, travel to an effector (muscle/gland)
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Interneurons
Located between motor and sensory neurons, found in CNS, make up 99.98% of neurons in the body
40
What is myelination?
The process by which part of an axon is wrapped with myelin sheath
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What is myelin?
Myelin is mostly fat made of plasma membrane of glial cells. It give sthe white color in CNS/PNS. It insulates, protects and nourishes
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Structure of a Nerve
Cable-like oragns in the PNS
Consist of numerous axons wrapped in connective tissue
Most nerves contain both myelinated and nonmyelinated sensory and motor axons
Axon is surrounded by Schwann cells (neurolemmocytes)
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SYNAPSES
Specialized junctions where axons contact other neurons, muscle cells or glands
In neurons, synapses occur anywhere (body, dendrites, telodendria) except on regions covered by myelin sheath. Axon-dendrite synapse is more common
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What are the types of synapses?
Electrical, chemical
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Electrical synapse
Both membrane of pre- and postsynaptic neuron bond together
Closer than in a chemical synapse
BIDIRECTIONAL
Fast, secure flow of ions
NOT COMMON IN BRAIN TISSUE
FOUDN IN SMOOTH MUSCLE AND CARDIAC MUSCLE (AT INTERCALATED DISCS)
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Chemical synapse
More common,
signaling molecular
Ach is the most common
Unidirectional
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What factors influence rate of conduction and why?
AXON DIAMETER - the greater the diameter, the faster the conduction
PRESENCE OF ABSENCE OF MYELIN
CONTINUOUS CONDUCTION - nervous impulse must travel entire length of axon
SALTATORY CONDUCTION - only on exposed regions (node of Ranvier); less energy
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Monosynaptic reflexes
One synapse
No interneuron
Knee jerk
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Polysynaptic
Multiple synapses
Interneurons
Withdrawal
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General regions of brain
Cerebrum, cerebellum, diencephalon, brainstem
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Specific regions of diencephalon
thalamus, epithalamus, hypothalamus
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Specific regions of brainstem
midbrain, pons, medulla oblongata
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Types of cranial meninges
dura mater, arachnoid mater, pia mater
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Dura mater
Outermost, tough membrane; outer periosteal layer against the bone; forms dural venous sinuses draining blood from brain; supportive structure formed by dura mater (falx cerebri, tentorium cerebelli)
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Arachnoid mater
Spider web filamentous layer
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Pia mater
Thin vascular layer adherent to contours of brain
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Ventricles of the brain
Third ventricle, fourth ventricle, lateral ventricles, cerebral aqueduct
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Function of ventricles of the brain
Circulate CSF
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CSF
Clear liquid fills ventricles and canals, flows in SUBARACHNOID SPACE
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Functions of CSF
Functions: buoyancy – floats brain
Protection – cushions from hitting inside of skull
Chemical stability – rinses away waste
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Hydrocephalus
CSF cannot circulate or drain properly – fluid build up causes increased pressure on the brain
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Flow of CSF
Formed by choroid plexuses --> ventricles --> central canal of spinal cord --> subarachnoid space --> arachnoid villi of dural sinus
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Fissures
deep grooves
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Sulcus
shallow grooves
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Gyrus
elevated folds
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Cortex
surface layer of gray matter on brain
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Function of left cerebral hemisphere
Speech, verbalization, math, logic
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Function of right cerebral hemisphere
Visual-spatial skills, intuition, emotion
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Cerebral lobes
Parietal, frontal, occipital, temporal, insula
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Frontal
Voluntary motor for planning, mood, smell, social judgment
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Parietal
Integrates sensory in shapes, textures, speech
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Occipital
Optical
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Temporal
Hearing, emotional behavior, learning, memory, smell
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Insula
Memory and taste
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What consists of gray matter?
Neuron bodies, dendrites, unmyelinated axons, glial cells (LOCATED IN MIDDLE OF SPINAL CORD; LOCATED IN OUTSIDE AND INSIDE OF BRAIN)
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What consists of white matter?
Dendrites, myelinated axons, glial cells (LOCATED ON OUTSIDE OF SPINAL CORD AND MIDDLE OF BRAIN)
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Classification of fibers within white matter of the cerebrum
Commissural fibers, association fibers, projection fibers
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Commissural fibers
Connecting cerebral hemispheres
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Association fibers
Connecting different parts of same hemisphere
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Projection fibers
Running vertically (ascending fibers carrying sensory information, descending motor information)
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Basal nuclei
Masses of gray matter deep to cerebral cortex
| Involved in motor control (start, stop and regulate intensity of voluntary movements ordered by cerebral cortex)
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Functions of gray matter
Basal forebrain nuclei: associated with memory, learning, arousal ,motor control, associated with synthesis and release of Ach
Claustrum: unknown function
Cerebral cortex: gyri and sulci increase SA
Area of complex functions (memory, abstraction, creativity, judgment)
Neurons arranged in layers; 47 structural areas based on thickness of layers
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Functional areas of the cerebral cortex
Sensory areas, association areas, motor areas
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Sensory areas
Conscious awareness of sensation
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Association areas
Integrate information
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Motor areas
Control voluntary motor functions
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Precentral gyrus
Located in the frontal lobe
| Primary motor cortex
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Postcentral gyrus
Located in the parietal, temporal and occipital lobes
| Primary somatosensory cortex
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Broca's Area
Generates motor program for larynx, tongue, cheeks and lips; transmits that to primary motor cortex for action
Lesion = motor (nonfluent) aphasia
Know what they want to say but can’t say it
Inability to coordinate muscles controlling speech
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Wernicke's Area
permits recognition of spoken & written
language
Fluent aphasia
Words are easily spoken but those used are incorrect
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Specific regions of diencephalon
Thalamus, hypothalamus, epithalamus
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Hypothalamus
Inferior to thalamus
Relay station for smell
LINKS NERVOUS SYSTEM TO ENDOCRINE SYSTEM VIA PITUITARY GLAND
Major regulator of homeostasis:
Controls/integrates ANS; seat of rage/aggression, body temp, hunger and the satiety, thirst; maintains waking state and sleep patterns thru pineal gland
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Epithalamus
Gets smaller with age (7)
Neural stimulus- sympathetic division of ANS
Melatonin helps regulate circadian rhythm
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Thalamus
Paired organ, located superior to midbrain
Contains 12 major nuclei
Relay station for all sensory EXCEPT SMELL to cerebral cortex
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Specific regions of the brainstem
Midbrain, pons, medulla oblongata
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Functions of the brainstem
Bidirectional passageway for tracts between cerebrum-spinal cord
Innervation of face/head; 10 of 12 cranial nerves attach here
Automatic behaviors necessary for survival
Integrates auditory and visual reflexes
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Midbrain
Lies between diencephalon and pons
| Mediates visual and auditory reflexes
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Pons
Pathway between cerebellum and cerebral cortex
Middle cerebellar peduncle connects pons to cerebellum
Relays nerve impulses related to voluntary skeletal movements from the cerebral cortex to the cerebellum
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Medulla Oblongata
Inferior cerebellar peduncle connects medulla to cerebellum
Projection fibers decussate here
Heart rate, respiratory rate
Adjusts blood vessel diameter
Reflex centers for coughin, sneezing, gagging, swallowing, vomiting, hiccupping
100
Cerebellum
Functions in the coordination of skeletal muscle contractions and MAINTENANCE OF NORMAL MUSCLE TONE, POSTURE AND BALANCE
Compares motor output of the primary motor area to sensory data from body (proprioceptors, vision, cochlea, etc)
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Functions of spinal cord
Involved in sensory and motor innervation of body below head
White matter: 2-way conduction pathway
Gray matter: major center of reflexes
Extends from foramen magnum to L2
Connected to 31 PAIRS of MIXED spinal nerves
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Cervical enlargement
supplies upper limbs
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Lumbar enlargement
supplies lower limbs
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Conus medullaris
Tapered inferior end
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Cauda equine
Individual spinal nerves within spinal canal
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Filum terminale
Filamentous end of meninges
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White matter of spinal cord
3 columns: posterior, lateral, anterior
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Fiber tracts
All axons within a tract relay the same information in the same direction
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Ascending tracts
carry sensory information toward the brain
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Descending tracts
carry motor commands to spinal cord
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Commissural tracts
carry information from one side of the spinal cord to the other
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Anterior horns
Cell bodies of somatic motor neurons
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Lateral horns
Cell bodies of autonomic motor
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Posterior horns
Axons of sensory neurons and cell bodies of int`erneurons
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Exteroceptors
Sensitive to stimuli arising from outside body
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Interoceptors
(Visceroreceptors) from internal viscera
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Propioceptors
Monitor degree of stretch in skeletal muscles, tendons, joints and ligaments
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Mechanoreceptors
Respond to touch, pressure, vibrations
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Baroreceptors
Respond to changes in blood pressure
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Thermoreceptors
Respond to temperature changes
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Chemoreceptors
Respond to molecules tasted or smelled and changed in blood chemistry
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Photoreceptors
Respond to light
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Nocireceptors
Respond to harmful stimuli (extreme heat and cold) that result in pain
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I
Olfactory, sensory
| V.S.: Smell, damage impairs sense of smell
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II
Optic, sensory
| Vision, not a true nerve, damage causes blindness (no regeneration)
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III
Oculomotor, mixed
| VM/SM: Provides eye movement, damage causes ptosis (drooping eyelid) and double vision
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IV
Trochlear, mixed
| Moves eye down and out
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V
Trigeminal, both
Main sensory nerve to face and muscles of mastication
Damage produces loss of sensation and impaired chewing/increased pain
Largest of cranial nerves
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VI
Abducens, mixed
Moves eye laterally (abduction)
Damage results in ability to move eye latearlly
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VII
Facial, both
Facial expressions, sense of taste on front 2/3 of tongue, salivary glands/tear, nasal/palatine glands
Damage = sagging facial muscles and disturbed sense of taste (called Bell’s Palsy
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VIII
Vestibulocochlear, sensory
Provides hearing/balance
Damage = deafness, dizziness, nausea, loss of balance
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IX
Glossopharyngeal, both
Control over swallowing, salivation, gagging, sensations from back of tongue, control of BP and respiration
Damage = loss of bitter/sour tastes and impaired swallowing
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X
Vagus, both
Only cranial nerve that extends beyond neck
Provides swallowing, speech, regulation of 2/3 of GI tract
Damage = impaired voice, swallowing/digestion
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XI
Accessory, mixed
Arises from BOTH brain/spinal cord
Contracts upper trap muscles
Damge = impaired shoulder movement
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XII
Hypoglossal, mixed
Provides tongue movements of speech, food manipulation and swallowing
Damge = inability to protrude tongue
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How many spinal nerves do we have?
31 pairs
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What are dermatomes? Why are they clinically important?
Area of skin innervated by a single spinal nerve
Used in determining level of spinal injuries
Anesthetic injection for surgery
SHingles
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Posterior (dorsal) ramus
Innervate deep muscles of the trunk responsible for movements of the vertebral column and the connective tissue and the skin near the midline of the back
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Anterior (ventral) ramus
```
Thoracic region: form intercostal nerves the innervate the intercostal muscles and the skin over the thorax
C1-C4 = cervical plexus
C5-T1 = brachial plexus
L1-L4 = lumbar plexus
L4-S4 = sacral plexus
S4-S5 = coccygeal plexus
```
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Nerve plexus
Networks of successive ANTERIOR rami that exchange fibers (crisscross and redistribute)
Mainly innervate the limbs
THORACIC ANTERIOR RAMI DO NOT FORM NERVE PLEXUSES
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Cervical plexus
Formed by ventral rami of C1-C4
Motor: Innervates muscles of the neck
Sensory: skin of upper chest, shoulder, neck and ear
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Brachial plexus
Formed by ventral rami of spinal nerves C5-T1
Serves upper limbs and shoulder girdle
Main branches/nerves: axillary, radial, musclocutaneous, ulnar, median
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Lumbar plexus
Formed by ventral rami of spinal nerves L1-L4
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Sacral plexus
Formed by ventral rami of L4-S4
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Lumbosacral plexus
Usually considered together because of close relationship. Contains four major nerves to the lower limb
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Phrenic nerve
Cervical plexus; from c3-c5, innervates diaphragm, neck injuries can be lethal
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Axillary nerve
Brachial plexus; motor: innervates deltoid/teres minor; sensory: from skin of the lateral shoulder
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Radial nerve
Brachial plexus; motor: stimulates extensor muscles of arm, forearm and hand
Sensory: from skin on posterior surface of arm/forearm, lateral 2/3 of dorsum of hand
Damage due to compression which results in crutch paralysis; major symptom is ‘wrist drop’
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Musculotaneous nerve
Brachial plexus; motor: stimulates flexors in anterior arm (causes flexion movements at shoulder/elbow); sensory: from skin along lateral surface of forearm
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Ulnar nerve
Brachial plexus: Motor: Stimulates flexor muscles in anterior forearm; Sensory: from skin on medial surface of hand, little finger, medial surface of ring finger
Most easily damaged
Hitting funny bone excites it
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Medial nerve
Brachial plexus; Motor; innervates all but one of the flexors of the wrist/fingers and thenar muscles at the base of the thumb; Sensory: from skin of anterolateral 2/3 palm, thumb, index and middle fingers; lateral surface of ring finger
Damaged in carpal tunnel and suicide attempts
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Femoral nerve
Lumbar plexus; Motor: innervates anterior muscles of thigh/flexors and adductors of the hip; Sensory: from skin of the anterior/lateral thigh, medial surface of leg/foot
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Sciatic nerve
Sacral plexus; THICKEST AND LONGEST NERVE OF THE BODY; innervates posterior thigh/entire lower leg.
Composed of 2 nerves.
Sciatic nerve injury: (fall, disc herniation) leg is nearly useless, cannot be flexes, foot/ankle movement is lost, footdrop
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Breakdown of spinal nerve pairs
```
Cervical - 8
Thoracic - 12
Lumbar - 5
Sacral - 5
Coccygeal - 1
```
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Differences between the ANS/SNS
ANS
Effector: glands/smooth muscle/cardiac muscle
Ganglia: yes
Neurotransmitter: Ach/Norepinephrine/Epinephrine
Myelin cover: pre-ganglionic
Number of motor neurons: two
Structure of motor neuron: one in myelinated (pre-ganglionic), one is not. There is a ganglion in between them.
```
SNS
Effector: skeletal muscle
Ganglia: No
Neurotransmitter: Ach
Myelin cover: yes
Number of motor neurons: one
Structure of motor neuron: one myelinated motor neuron
```
156
Differences between the sympathetic/parasympathetic divisions
SYMPATHETIC:
Fight, flight, fright
Thoracolumbar: all neurons in the lateral horn of gray matter T1-L2
Lead to every part of the body
Norepinephrine is neurotransmitter released by most postganglionic fibers
Anatomically and functionally more complex than parasympathetic: two types of sympathetic ganglia (trunk/collateral ganglia), rami communicantes
PARASYMPATHETIC
Rest and digest
Craniosacral system because all preganglionic neurons are in brain steam or sacral levels of spinal cord
Only innervate internal organs
Ach is neurotransmitter at end organ as well as preganglionic synapse
157
Synapse in trunk ganglion at the same level
Begins in lateral horn of gray matter, goes thru ventral root, crosses thru white ramus communicans, synapses, crosses thru gray ramus communicans, thru ventral ramus, to effector organ
158
Synapse in trunk ganglion at a higher/lower level
Begins in lateral horn of gray matter, crosses through ventral root, crosses thru white ramus communicans, moves up (or down) to next ganglion where it synapses, then crosses thru that gray ramus communicans, thru ventral ramus, to effector organ
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Pass thru sympathetic trunk to synapse in a collateral ganglion anterior to the vertebral column
Begins in lateral horn of gray matter, crosses thru ventral root, crosses thru white ramus, bypasses ganglion to a collateral ganglion where it synapses, to effector organ
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Cranial outflow
OCULOMOTOR NERVE – pupils constrict
FACIAL NERVE – tears, nasal mucus, saliva
GLOSSOPHARYNGEAL NERVE – parotid salivary gland
VAGUS NERVE – visceral organs of thorax and abdomen (stimulates digestive glands, increases motility of smooth muscle of digestive tract, decreases heart rate, causes bronchial constriction)
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Antagonistic effects
Oppose each other
Exerted thru dual innervation of same effector (heart rate decreases is para, hear rate increases is sympa)
Exerted because each division innervated different cells (pupillary dilator muscle (sympa) dilates pupil, constrictor pupillae (parasympa) constricts pupil
162
Cooperative effects
Best seen in external genitalia – parasympathetic fibers cause vasolidation and are responsible for erection of the penis and clitoris, sympathetic fibers cause ejaculation of semen in males and reflex peristalsis in females
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Vasoconstriction
increase in firing frequency
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Vasodilation
decrease in firing frequency
