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125 terms

Chapter 23 Nervous System

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Functions of the nervous system are?
Sensory input, Interpretive functions, Motor output, Higher mental functioning, Emotional responsiveness
There are 2 basic divisions of the nervous system?
Central and peripheral nervous system
Central Nervous System (CNS) Functions?
Interprets sensory info, Initiates motor responses, Center for thoughts & emotions.
CNS major components are
Brain, spinal cord, meninges, cerebrospinal fluid.
All of these are surrounded by bones of the skull and spinal column
Peripheral Nervous System (PNS) cranial nerves exit?
Brain
Peripheral Nervous System (PNS) spinal nerves exit?
Spinal cord
Subdivisions of PNS are?
Somatic nervous system: Voluntary
Autonomic nervous system: Involuntary
PNS has how many pairs of nerves?
43
PNS has how many pairs of cranial nerves?
12
PNS has how many pairs of spinal nerves?
31
There are 2 types of cells of the nervous system?
Neuroglia
Neurons
Neuroglia or glia cell is
Connective tissue that supports, nourishes, protects, insulates and organizes neurons.
Neuroglia cell make up more than?
50% of CNS
Glia cells in the CNS are?
Astrocytes, Ependymocytes, Microglia, Oligodendrocytes
Glia cells in the PNS are?
Schwann cells, Satellite cells
Neurons
Basic impulse-conducting cells possessing specialized properties.
Neuron Properties include?
Excitability, Conductibility, Secretion
Parts of a Neuron?
Cell body (cyton), Dendrites, Axon
Cell Body(cyton)
Contains nucleus and other organelles
Dendrites
Transmits impulses toward cell body
Axon
Transmits impulses from cell body
Structures associated with axons?
Telodendria, Synaptic bulb, Synaptic vesicles
Telodendria
Short filaments on ends of axons
Synaptic bulb
Located at end of telodendria
Contain synaptic vesicles
Synaptic vesicles
Store neurotransmitters
Sensory = afferent
Carry impulses to CNS
Motor = efferent
Carry impulses from CNS
Interneuron = association
Carry impulses between sensory & motor neurons
Perform integrative functions
Nerve Impulses
Electrical signals that convey information along a neuron.
Action Potential
Change in the electrical charge of a neural membrane caused by movement of charged particles (ions)
Action Potential is needed
to conduct an impulse
Polarization
Membrane's resting state not conducting an impulse
Polarization has inside and outside charges what are they?
Inside bears negative (-) charge
Outside bears positive (+) charge
Sodium-potassium pump
Produces & maintains polarization and pumps ions in opposite direction at an unequal rates.
Depolarization
When stimulated, channels open and Na flows into cell. Cell interior changes from (-) to (+)
Depolarization occurs in
segments down length of axon
All-or-none Response
Impulse is conducted along entire neuron at maximum capacity.
Impulse continues until it reaches end of neuron
Repolarization
Membrane quickly becomes impermeable to Na
K channels open
Cell membrane repolarizes
Another term for myelinated axon is?
Fast-conducting nerve fibers
Synapse
The junction between 2 neurons or between a neuron an a muscle or gland. Impulses are transmitted across sysapse by action of neurotransmitters
Synaptic Structures
Synaptic bulb (presynaptic neuron)
Synaptic cleft
Plasma membrane (postsynaptic neuron)
Synaptic bulb (presynaptic neuron)
Located at end of axon
contains neurotransmitters
Synaptic cleft
Space between synaptic bulb and plasma membrane
Plasma membrane (postsynaptic neuron)
Dendrites of postsynaptic neuron contain binding sites for neurotransmitters
Synaptic Transmission
1. Impulse travels down axon to synaptic bulb (neurotransmitters are released)
2. Neurotransmitters cross synaptic cleft
3. Neurotransmitters bind to receptors on plasma membrane of postsynaptic neuron
*Neurotransmitter action does not last long
continuously removed from synaptic cleft by enzymes or reuptake.
Neurotransmitters
Chemical messengers involved in nerve transmission are stored in vesicles and can be either excitatory or inhibitory
Most common neurotransmitter is?
Acetylcholine(ACh)
Other Neurotransmitter are?
Epinephrine & norepinephrine
Serotonin
Dopamine
Central Nervous System (CNS) consists of?
Brain & Spinal cord
Brain & spinal cord are all protected by?
Skull, Vertebral column, Meninges, Cerebrospinal fluid
Brains has 4 main sections?
Cerebrum, Diencephalon, Cerebellum, Brain stem
What is the largest area of the brain?
Cerebrum
Cerebrum contains?
Sensory & motor areas
Language centers
Limbic system (governs many certain emotions)
Cerebral Cortex
Outer region of cerebrum.
Sulci
grooves in the outer later of the cerebral cortex
Fissure
a deep sulcus that separate the cerebrum into lobes.
Gyri
elevated ridge of tissue
Cerebral Hemispheres
Cerebrum contains right and left hemispheres
Longitudinal fissure
Corpus callosum
Longitudinal fissure
Separates hemispheres
Corpus callosum
Transverse fibers connection hemispheres
Right Hemispheres Specialization
Music, Art & spatial relationships, emotional expression
Left Hemispheres Specialization
Language; receptive and expressive
Reasoning and analytical skills such as math
Cerebral Lobes contain 4 they are?
Frontal, Parietal, Temporal, Occipital
Frontal Lobes
Regulates motor output and cognition.
Contains:
Broca's areas - speech production
Prefrontal cortex - where emotion are processed
Precentral gyrus - called primary motor area
Parietal Lobes
Regulates proprioception, reading and taste.
Governs sensory input (mainly skin & muscles)
Contains:
Postcentral gyrus
Temporal Lobes
Contains:
auditory & olfactory areas
Wernicke area - Language comprehension
Occipital Lobes
Visual areas
Consciousness
degree of mental alertness and responsiveness
The 4 levels of consciousness recorded as brain wave patterns are?
Beta, Alpha, Theta, Delta
Beta
Wakeful consciousness & mental activity
REM sleep appears as beta waves
Alpha
Awake & relaxed
Theta
Drowsiness & dreamlike awareness
used in hypnosis to access deep-rooted memories
Delta
deep sleep from which the subject is not easily aroused
Diencepholon is located in
the center of the brain
Thalamus
nearly 80% of diencephalon
Relays sensory information to appropriate part of cerebrum
Hypothalamus
Regulates ANS and endocrine system
Controls hunger and thirst, anger and aggression, hormones, sexual behavior and sleep patterns
Pituitary Gland
Sits in sella turcica of sphenoid bone
Pineal Gland
Located below corpus callosum
Cerebellum is located?
posterior and inferior to cerebrum
Cerebellum regulates?
muscle tone, posture, balance
Brainstem is continuous with
the spinal
There are 3 main divisions of the Brainstem
Mid-brain
Pons
Medulla oblongata
Mid-brain
conducts impulses from cerebrum to pons
conducts impulses from spinal cord to thalamus
Pons
bridges cerebellum and cerebrum with spinal cord
Medulla oblongata is located?
inferior portion of brainstem
Medulla oblongata
conducts sensory & motor impulses between brain & spinal cord
Medulla oblongata contains?
Respiratory center
Cardiovascular center
Vasomotor center
This contains may crossing over fibers called Decussation
Medulla oblongata
Blood-Brain Barrier
Semipermeable wall of blood capillaries. Prevents or slows passage of some chemicals and pathogens from blood into CNS
This has thick basement membrane and glial cells
Blood-Brain Barrier
Spinal Cord
Exits skull via foramen magnum and is known as the information highway and a integrating center.
Cauda Equina
lower portion of cord shaped like a horse tail
Filum terminale
Fibrous extension of cauda equina
A cross section of the spinal cord reveals this?
White matter located on periphery and Gray matter located in center(H-shaped)
Gray matter in H contains 3 regions called horns?
Anterior horn
Lateral horn
Posterior horn
White matter found in the spinal cord is called
Columns
There are 3 columns in the spinal cord column?
Anterior column
Lateral column
Posterior Column
Tracts
Collection of nerves running up and down spine
There are types of tracts
Ascending - Sensory (afferent) impulses travel up cord
Descending - Motor (efferent) impulses travel down cord
Meninges
connective tissue coverings surrounding brain and spinal cord. It has 3 layers
Meningeal layers are?
Pia Mater, Arachnoid, Dura mater
Pia Mater
Innermost delicate layer
attaches to brain and spinal cord
Arachnoid
Middle later resembling a spider's web
Dura mater
Outermost dense layer
lies against skull and spinal column
Meningeal spaces
Subarachnoid, Subdural, Epidural
Cerebrospinal Fluid
Fluid circulating around brain and spinal cord
Functions of the Cerebrospinal Fluid
Supplies O2 and nutrients, Carries away wastes, Acts as a shock absorber
Cranial nerves
Arise from brain
12 pairs
Spinal nerves
arise from spinal cord
31 pairs
CN V(5) Trigeminal
contains 3 branches; pain, temperature and motor innervation for muscles of mastication.
CN VII(7) Facial
Facial expression and produces both saliva and tears.
CN X(10) Vagus
Receives sensations from external ear and external auditory canal and thoracic and abdominal organs. Aids digestion. Regulates heart activity
Nerve Roots
part of spinal nerve that connects to spinal cord.
2 types of nerve roots
Ventral (anterior)
Dorsal (posterior)
Gaglion
Cluster of nerve cell bodies in PNS
Nerve Plexuses
Network of intersecting nerves in PNS
There are 3 major plexuses?
Cervical, Brachial, Lumbosacral
Dermatomes
Area of skin supplied by specific sensory nerve root
Reflexes
Involuntary, predictable response to a stimulus
Reflex arc
carries stimulus to spinal cord
connects motor neuron to appropriate muscle or gland
Autonomic Nervous System has 2 divisions?
Sympathetic & Parasympathetic
Parasympathetic Nervous System
Supports functions that conserve & restore energy - (Maintains homeostasis and regulates urinary & digestive processes, pooping and storing nutrients)

Most active under calm conditions

Referred to as craniosacral outflow
Sympathetic Nervous System
Uses body energy for periods of physical exertion or emotional stress

Adrenals secrete ephinephrine

Referred to as thoracolumbar outflow
Called "fight-or-flight
Sympathetic Nervous System
Law of Facilitation
When an impulse has passed once through a certain set of neurons to the exclusion of others, it tends to take the same course of future occasions and each time it traverses this path the resistance is less.