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Kinetic Anatomy - Nervous System
Dr Hoyt Anatomy Nervous System
61
Anatomy
Undergraduate 2
02/22/2011

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Term
Autonomic Nervous System (ANS)
Definition
• A system of motor neurons that innervate smooth muscle, cardiac muscle, and glands
• Maintains homeostasis
• No conscious control necessary
Term
Autonomic
Definition
• Autonomic (Involuntary)
– Smooth muscle (visceral)
– Cardiac muscle
– Glands
Term
Somatic vs Autonomic Nervous
Systems
Definition
• Somatic
– Single axon
– Cell bodies in CNS
• Autonomic
– Pre and post ganglionic neurons
– Cell bodies in and outside CNS
Term
Divisions of the ANS
Definition
• Parasympathetic
– Most active in nonstressful situation
– Concerned with keeping body energy use as low
as possible
• Sympathetic
– “Fight or flight” system
– Stimulated by vigorous physical activity
Term
Parasympathetic
Definition
– Slows heart rate
– Constricts peripheral blood vessels
– Constricts bronchi
– Constricts pupils
– Aids or speeds up digestion and absorption of
nutrients
Term
Sympathetic
Definition
– Accelerates heart rate
– Causes a release of epinephrine (adrenaline)
– Constricts visceral blood vessels
– Dilate bronchi
– Dilate pupils
– Slows down digestion
Term
Sensory Receptors
Definition
• Structures that are specialized to respond to changes
in their environment (stimuli)
• Their activation trigger nerve impulses along afferent
fibers that transmit the impulse toward the CNS
• Classified by type
Term
Types of Sensory Receptors
Definition
• Mechanoreceptors
– Touch, pressure (including blood pressure),
vibration, stretch, and itch
• Thermoreceptors
– Temperature
• Photoreceptors
– Respond to light (eye)
• Chemoreceptors
– Smell, taste, blood chemistry
• Nociceptors
– Respond to potentially damaging stimuli (pain)
Term
Nerves of the PNS
Definition
• A nerve consists of multiple nerve fibers or
neurons
• Nerves may be
– Sensory (afferent) nerves
– Motor (efferent) nerves
– Mixed nerves (most nerves are this type)
Term
Mixed Nerves
Definition
– Often carry both somatic and autonomic (visceral)
neurons
– Neurons may be classified according to the region
they innervate
• Somatic afferent; somatic efferent
• Visceral afferent; visceral efferent
Term
Cranial Nerves
Definition
• Associated with the brain
• Twelve pairs
• Each have a name and Roman numeral for
identification
• The first two pairs attach to the forebrain and
the rest originate from the brain stem
• Serve only the head and brain structures with
the exception of the Vagus nerve (X)
Term
Cranial Nerve
Olfactory (I)
Definition
- Originate in the cerebrum
– Sensory
– Carry afferent impulses for sense of smell
Term
Cranial Nerve
Oculomotor (III)
Definition
– Originate in the midbrain
– Motor
– Movement of the eye
– Part of the parasympathetic nervous system
Term
Cranial Nerve
Trigeminal (V)
Definition
– Originate from the pons
– Sensory and motor (mixed)
– Sensory – Conveys afferent impulses from the teeth, gums, & mucous membranes of the nose and mouth
– Motor – Efferent impulses to the muscles of mastication (chewing)
– Largest of the cranial nerves
Term
Cranial Nerve
Abducens (VI)
Definition
– Originate in the pons
– Motor
– Efferent impulses to the lateral rectus muscle of
the eye
Term
Cranial Nerve
Vestibulocochlear (VIII)
Definition
– Originate from the pons
– Sensory
– Afferent impulses for sense of equilibrium
(vestibular) and sense of hearing (cochlear)
Term
Cranial Nerve
Vagus (X)
Definition
– Originate from the medulla oblongata
– Sensory and motor (mixed)
– Afferent and efferent impulses from and to neck,
thorax, and abdomen
– A part and major contributor to the
parasympathetic nervous system
– Longest of the cranial nerves; has most extensive
distribution
Term
Cranial Nerve
Accessory (XI)
Definition
– Originate in the medulla oblongata
– Motor
– Efferent impulses to muscles of the larynx,
esophagus, and trapezius
Term
Spinal Nerves
Definition
• 31 pairs
• Arise from the spinal cord
• Supply all parts of the body except the head
and some areas of the neck
• All are mixed nerves
• Enlargements of the cervical and lumbar regions
Term
The Central Nervous System
Definition
The Brain and The Spinal Cord
Term
The Brain
Definition
• Average adult man’s brain weighs about 1600
grams (3.5 lbs)
• Average adult woman’s brain weighs about
1450 grams
• Contains approximately 100 billion neurons
Term
Regions of the Brain
Definition
• Cerebral Hemispheres
• Diencephalon
– Thalamus, Hypothalamus, Epithalamus
• Brain Stem
– Midbrain, pons, medulla oblongata
• Cerebellum
Term
Cerebral Hemispheres
Definition
• Form the superior part of the brain
• Account for about 83% of total brain mass
• Marked by elevated ridges of tissue called gyri
• The gyri are separated by shallow grooves
(sulci) or deeper grooves (fissures)
Term
Basic Surface Anatomy
Definition
• Hemispheres
• Longitudinal Fissure
• Central Sulcus
• Lateral Sulcus
Term
Lobes of the Cerebrum
Definition
• Frontal – Anterior to the central sulcus and superior
to the lateral sulcus
• Parietal – Posterior to the central sulcus
• Temporal – Inferior to the lateral sulcus
• Occipital – Posterior to the parietal and temporal
lobes
• Insula – Deep within the brain covered by parts of
the frontal, parietal, and temporal lobes
Term
Diencephalon
Definition
• Forms the central core of the forebrain
• Consists of
– Thalamus
– Hypothalamus
– Epithalamus
Term
Brain Stem
Definition
• Consists of the
– Midbrain
– Pons
– Medulla Oblongata
Term
Brain Stem (continued)
Definition
• Midbrain
– Conduction pathway between higher and lower
brain centers
– Visual and auditory reflex centers
– Contains nuclei for cranial nerves III and IV (eye
movement)
Term
Brain Stem (continued)
Definition
• Pons
– Between the midbrain and medulla oblongata
– Conduction pathway between higher and lower
brain centers
– Relay information from the motor cortex of the
cerebrum to the cerebellum
– Contain nuclei that assist in respiration
– Contain nuclei for cranial nerves V, VI and VII
Term
Brain Stem (continued)
Definition
• Medulla Oblongata
– Conduction pathway between higher brain
centers and spinal cord
– Contains nuclei for cranial nerves VIII – XII
– These nuclei receive impulses from skin, control
heart rate & blood vessel diameter, and control
respiratory rate & depth of breathing
Term
Cerebellum
Definition
• Located dorsal to the pons and medulla
• Receives and processes information from the cerebral cortex and proprioreceptors throughout the body.
• Sends information to the cerebral cortex that helps maintain posture & balance and ensures smooth, coordinated movements
Term
Protection of the Brain
Definition
• The brain is protected by:
– Bone (skull)
– Membranes (meninges)
– Watery cushion (cerebrospinal fluid)
• Also protected from harmful substances in the blood by the blood-brain barrier
Term
The Meninges
Definition
• Three connective tissue membranes that
surround the brain and spinal cord
• The three meninges are the
– Dura mater
– Arachnoid
– Pia mater
Term
The Meninges (continued)
Definition
• Dura mater
– Two-layered sheet of fibrous connective tissue
– Subdural space
• Filled with cerebrospinal fluid
Term
The Meninges (continued)
Definition
• Arachnoid mater
– Thin layer of connective tissue
– Beneath the arachnoid membrane is the
subarachnoid space – weblike extensions span this space
– Cerebrospinal fluid fills this space
– The subarachnoid space contains the largest blood vessels serving the brain
Term
The Meninges (continued)
Definition
• Pia mater
– Very thin layer
– Clings to the brain
– Contains many tiny blood vessels
Term
Cerebrospinal Fluid
Definition
• Found in and around the brain and spinal cord
• Provides buoyancy to the brain
• Provides protection from blows and other
trauma
• Also helps to nourish the brain
Term
Blood-Brain Barrier
Definition
• A selective protective mechanism that inhibits the passage of materials from the blood into brain tissue
• Helps maintain a stable environment for the brain
• Brain capillaries are the least permeable capillaries in the body
Term
Spinal Cord
Definition
• Enclosed within the vertebral column
• About 17 inches long
• Provides a two-way conduction pathway to and from the brain
• A major reflex center
• Protected by bone, meninges, and
cerebrospinal fluid
Term
Anatomy of the Spinal Cord
Definition
• Gray matter
– Neuron cell bodies and their unmyelinated processes
– Posterior (dorsal) horns
• Dorsal roots (sensory)
– Anterior (ventral) horns
• Ventral roots (motor)
• White matter (Funiculi)
– Myelinated nerve fibers that make up nerve tracts
Term
Fundamentals of the Nervous
System and Nervous Tissue
Definition
Nervous System
Term
Nervous System
Definition
The master controlling and communicating
system of the body
-Three functions
Sensory input
Integration
Motor output
Term
Organization of the Nervous
System
Definition
Central Nervous System (CNS)
-Brain and Spinal Cord

Peripheral Nervous System (PNS)
-Outside the CNS
-Consists of the cranial and spinal nerves
Term
Peripheral Nervous System
Definition
Sensory (Afferent) Division
-Keeps CNS informed
Towards CNS
-Motor (Efferent) Division
Transmits impulses from the CNS to the
muscles and glands
-sends messages away from CNS
Term
Organization of the Nervous
System (continued)
Definition
Motor Division of the PNS
-Somatic Nervous System
 Voluntary
-Autonomic Nervous System
 Involuntary
 Subdivisions
• Sympathetic nervous system
• Parasympathetic nervous system
Term
Nervous Tissue
Definition
-Nervous tissue is highly cellular
Densely packed (< 20% of CNS is
extracellular space)
Two principal types of cells
Neurons
Supporting cells
Term
Supporting Cells
Definition
 t Referred to as neuroglia or glial cells
 CNS (4)
 Astrocytes
Microglia
 Ependymal cells
 Oligodendrocytes
 PNS (2)
 Satellite cells
 Schwann cells
Term
Neurons
Definition
 Neurons = Nerve cells
 Structural units of the nervous system
 React to physical and chemical changes occurring the body, conducting nerve impulses
 Long lifespan
 Have a nucleus but do not divide or reproduce (amitotic)
 High metabolic rate – require continuous and abundant supply of oxygen and glucose
Term
Neurons
Definition
 Cell body
 Contains a nucleus and other cellular organelles
 Dendrites
 Receptor surfaces of the neuron; transmit nerve impulse toward the cell body
 Axon
 Generate nerve impulses and transmit them away from the cell body
Term
Classifications of Neurons
Definition
Structure
Multipolar Neurons
 Bipolar Neurons
 Unipolar Neurons
Function
 Sensory (Afferent) Neurons
Motor (Efferent) Neurons
 Interneurons
Term
Types of Neurons – General Structures
Definition
 General Somatic Efferent
Signal runs from brain or spinal cord to
muscles
 General Visceral Efferent
Signal runs from brain or spinal cord to smooth muscles and glands
 General Somatic Afferent
Signal runs from muscles to brain and spinal
cord
 General Visceral Afferent
Signal runs from organs to brain or spinal cord
Term
Types of Neurons – Cranial Structures
Definition
 Special Visceral Afferent
Signal runs from senses of taste and smell to the brain
 Special Somatic Afferent
Signal runs from senses of sight, hearing, and equilibrium to the brain
Term
Somatic Motor Systems
- Effectors
Definition
• Somatic (Voluntary)
– Skeletal Muscles
Term
Types of Neurons – Cranial Structures (a
Definition
 Special Visceral Efferent
Signal runs from the brain to control chewing, swallowing, expression, and speaking
Term
Types of Neurons – General Structures (a
Definition
 General Visceral Efferent
Signal runs from brain or spinal cord to smooth muscles and glands
Term
Cranial Nerve
Optic (II)
Definition
– Originate in the cerebrum
– Sensory
– Carry afferent impulses for vision
Term
CRANIAL NERVE
Trochlear (IV)
Definition
– Originate in the midbrain
– Motor
– Eye movement
– Smallest of the cranial nerves
Term
CRANIAL NERVE
Facial (VII)
Definition
– Originate in the pons
– Sensory and motor (mixed)
– Sensory – Afferent impulses from the tongue
(taste)
– Motor – Efferent impulses to the muscles of facial
expression
– Part of the parasympathetic nervous system
Term
CRANIAL NERVE
Glossopharyngeal (IX)
Definition
– Originate in the medulla oblongata
– Sensory and motor (mixed)
– Sensory – Afferent impulses for taste, touch,
pressure, & pain from back of tongue and pharynx
– Motor – Efferent impulses to small muscles &
glands on back of tongue
– Part of the parasympathetic nervous system
Term
CRANIAL NERVE
Hypoglossal (XII)
Definition
– Originate in the medulla oblongata
– Motor
– Efferent impulses to muscles of the tongue
Term
CRANIAL NERVE
OPTICAL II
Definition
Originates in Cerebrum
Sensory
Carr Afferent Impulses for Vision
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