Nervous System Flashcards
- Acts as the integrating center
- Brain (80-100 billion neurons) and spinal cord (100 million neurons)
Central Nervous System
Cranial nerves and branches, spinal nerves and branches, ganglia, plexuses, and sensory receptors
Peripheral Nervous System
-Sends information to the CNS from sensory receptors through afferent (sensory)
neurons
Sensory
Takes information from the CNS to target cells via efferent neurons
- Autonomic neurons
- Sympatheitc
- Parasympathetic
- Somatic motor neurons
Efferent
-Basic signaling nits of the nervous system Components - Cell Body - Dendrites - Axons - Presynatic Terminals
Neurons
- Acts as the integrating center
- Contains the nucleus and protein synthesizing regions
Cell body (Soma)
Receive incoming signals from neighboring cells
Dendrites
Carry outgoing signals from the integrating center to target cells
Axons
Contain the transmitting elements that are transferred from the soma.
Presynatic Terminals
During development the dendrite fused with the axon
Pseudounipolar
Two relatively equal fibers extending off the soma
Bipolar
CNS interneurons that have no apparent axon
Anaxonic
- CNS interneurons that are highly branched but lack long extensions (OR)
- Efferent neurons that have five to six dendrites each branching four to
six times. A single long axon may branch several times and end at
enlarged axon terminals
Multipolar
-Carry information about temperature, pressure, light, and other stimuli to the
CNS
-Specialized receptors convert stimulus to electrical energy
Afferent Sensory
Complex branching neurons that facilitate communication between neurons
Interneurons
Usually have axon terminals or varicosities
Efferent
- Bundles of neurons
- May be Efferent, Afferent, or Mixed
Nerves
- Support cells
- Outnumber Neurons 10-50:1
- Physical and biochemical support as well as communication with neurons
- Myelin Forming Glia
Glia
Composed of multiple concentric layers of phospholipid membrane
wrapped around an axon
- Provides structural stability and insulates the neuron to speed up signals
(saltatory conduction)
Myelin
Multiple Sclerosis caused by
Demyelination of brain and spinal cord
- Line fluid filled cavities in the brain and spinal cord
- Functions
- Produce most cerebral spinal fluid that fills the cavities
- Protection
- Chemical stability
- Clear waste
- Possibly a source of neural stem cells
Ependymal
Highly branched glial cells believed to make up half of all cells in the
brain
- Several subtypes, forms a functional sub-network
Functions
- Take up and release chemicals at synapses
- Provide neurons with substrates for ATP production
- Help maintain homeostasis in ECF (take up K+ and H2O)
- Surround vessels
- Part of the blood brain barrier
- Influence vascular dynamics
Astrocytes
-Specialized immune cells
-Functions
-Protect and preserve neuronal cells from pathogens and facilitate recovery from metabolic insults
-If activated past a threshold or remain active too long they
display detrimental properties
Microglia
- Exist within ganglia (bundles of cell bodies) in the PNS
Functions - Form a supportive capsule around the cell bodies of neurons
- Supply nutrients
- Structural cushioning support
Satellite Cells
5 Majors types of Gated Channels
- Na+ channels
- K+ channel
- Ca2+ channel
- Cl- channels
- Monovalent cation channels (allow Na+ and K+ to pass)
- Open in response to physical forces (pressure or stretch)
- Found in sensory neurons
Mechanically Gated
Respond to ligands including: extracellular neurotransmitters and neuromodulators or intracellular signaling molecules
Chemically Gated
Change in response to changes in the cells membrane potential
Voltage Gated
- Disorders in channels that disrupt normal ion flow
- Activation, inactivation, permeation
- Cystic fibrosis, congenital insensitivity to pain, muscle disorders
Channelopathies
-Current (I) is directly proportional to the electrical potential difference (in volts, V)
between two points and inversely proportional to the resistance
Ohm’s Law
Major pathway for information flowing between the brain and the skin,joints, and
muscles of the body
Spinal Cord
Major Regions of the Spinal Cord
- Cervical (8 segments)
- Thoracic (12 segments)
- Lumbar (5 segments)
- Sacral (5 segments)
Sensory and motor nuclei
Gray Matter
- Somatic seonsory nuclei as well as a visceral sensory nuclei
- Afferent (in)
Dorsal Horn
-Autonomic efferent (out) nuclei
-Spinal reflex
-The spinal cord acts as an integrating center to initiate a response
to a stimulus without receiving input from the brain
Lateral Horn
- Somatic motor nuclei
- Efferent (out)
Ventral Horn
- Tracts of axons carrying information to and from the brain
- Ascending tracts
- Carry sensory information to the brain
- Dorsal and external lateral
- Descending tracts
- Carry commands to motor neurons
- Ventral and Interior lateral
White Matter
- Oldest and most primitive region of the brain
-Ascending and descending tracts run through the brain stem
-11 of 12 cranial nerves that carry sensory and motor info for head and
neck (does not have the olfactory nerve)
-Contains many nuclei
-Involved in many basic processes: arousal and sleep, muscle tone and stretch
reflexes, coordination of breathing, blood pressure regulation, and modulation of
pain
Brainstem
-Extends throughout the brain stem
-small clusters of neuronal cell bodies interspersed among
ascending and descending tracts
-Important in consciousness, arousal, attention and alertness
-Reticular Activating System inactivated during sleep; damage can induce
a coma
-Regulates muscle tone, assists in vital functions
Reticular Formation
-White matter containing all ascending somatosensory tracts and descending
corticospinal tracts
-90% of corticospinal tracts decussate (crossover) at the pyramids
-Nuclei in the medulla include the cardiovascular center and the medullary
respiratory center
-Contains the vomiting and swallowing center and controls coughing, sneezing
and hiccuping
Medulla
- Bulbous protrusion containing nuclei and tracts
- Relays information between the cerebellum and cerebrum
Pons
- Junction between lower brain stem and diencephalon (nuclei and tracts)
- Primary function is controlling eye movement
- Also relays auditory and visual reflexes
- Movement of the body in response to visual and auditory stimuli
- Contains the substantia nigra
Midbrain
-Second largest brain structure
-Two cerebellar hemispheres
-Processes sensory information and coordinates the execution of movement
-Sends feedback signals to motor areas of the cerebral cortex via its connections
to the thalamus to help correct errors and smooth the movements
-Regulates posture and balance
Cerebellum
Lies between the brain stem and cerebrum
Diencephalon
-Relay center
-Receives sensory info from the optic tract, ears, spinal cord, and motor
info from the cerebellum and projects the info to the cerebrum for
processing
Thalamus
-The center for homeostasis
-Body osmolarity, food intake, cardiovascular control,body
temperature
-Influences autonomic and endocrine function
-Activates sympathetic nervous system, controls reproductive
functions, interacts with limbic system to influence behavior and
emotions, secretes trophic hormones that control release from
anterior pituitary gland
Hypothalamus
Cyclically releases melatonin involved in sleep/wake
Pineal Gland
Connected to brain via the infundibulum
Pituitary Gland
- Neural tissue
- Extension of the brain that secretes neurohormones made in the
hypothalamus
Posterior Pituitary Gland
-Endocrine tissue
-Releases peptide hormones into a second set of capillaries for
distribution to the rest of the body
Anterior Pituitary Gland
