Test 2: Nervous System Flashcards
Name the major divisions of the nervous system, both anatomical and functional
Anatomically - Central and Peripheral NS
Functionally - Sensory and Motor of the PNS
Both sensory and motor divisions have somatic and visceral divisions
The visceral motor divison can be further divided into sympathetic or parasympathetic
What are the primary functions of the nervous system?
Receiving sensory input
Monitoring internal and external stimuli
Integrating information
Processing sensory input and initiating response
Controlling muscles and glands
Works with endocrine system to control all other organs
Maintains homeostasis
Establishes mental activity
Consciousness, thinking, memory, emotion
What are the organs of the Central Nervous System?
Brain and Spinal cord in the dorsal cavity
What are the organs of the Peripheral nervous system?
All nervous tissue outside brain and spinal cord; nerves, ganglia, enteric plexus, sensory receptors
What are the divisions of the PNS?
Somatic Nervous System
Autonomic Nervous System
Enteric Nervous System
Describe the divisions of the Somatic Nervous System
Somatic Afferent (sensory) - convey information from sensory receptors towards the CNS
Somatic Efferent (motor) - convey information away from the CNS towards skeletal muscles under voluntary control
Interneurons connect the two
Describe the divisions of the Autonomic Nervous System
Sensory neurons convey information to sensory receptors primarily in visceral organs, involuntary
Two branches:
Sympathetic division - (fight-or-flight): dilates pupils, inhibits saliva, raises heart rate, halts digestive organs, relaxes bladder
Parasympathetic division - (rest-and-digest): constricts pupils, increases saliva, reduces heart rate, stimulates digestive organs, constricts bladder
Describe the Enteric Nervous System
Used to be grouped with the autonomic nervous system, brain of the gut
Briefly describe the organization of the PNS with regards to neurons
Receptor -> sensory NS -> CNS -> motor NS - Effector
What are neurons? What are their universal properties?
Nerve cells in the CNS and PNS
Receive stimuli and transmit action potentials
Three Universal properties:
1) Excitability: response to stimulus (environmental changes)
2) Conductivity: Neuronal response to stimulus is production
3) Secretion: When the signal reaches the synapse a neurotransmitter is scereted and crosses the cleft
Describe Neuroglia
Helpers that do not generate or connect nerve impulses, but support and maintain neural networks
List the Neuroglia of the CNS
Astrocytes, Oligodendrocytes, Ependymal, Microglia
List the Neuroglia of the PNS
Satelitte cells, Schwann cells
Describe Astrocytes
In the CNS
Maintain BBB, provide structural support, regulate ion/nutrient/chemical concentrations
Absorb and recycle neurotransmitters
Form scar tissue
Have foot processes that cover surface of neurons and pia mater
Describe Oligodendrocyes
In the CNS
Myelinate CNS axons
Wraps around a bunch of axons at once, limited regenerative capcitiy
Describe Ependymal cells
In the CNS
Line ventricles of brain and central canal of spinal cord
Produce and maintain cerebrospinal fluid
have cilia that help move fluid
Describe Microglia
In the CNS
Remove cell debris, pathogens, waste by phagocytosis
Similar to macrophages, responds to inflammation
Describe Satellite cells
In the PNS
Surround neuron cell bodies, regulate nutrient and neurotransmitter levels around neurons in ganglia
Surrounds and insulates nerve soma
Similar to astrocytes
Describe Schwann cells
In the PNS
Surrounds axons, responsible for myelination of peripheral axons
Participate in repair process after injury
What’s the purpose of myelination?
Lets the electrical signal skip across the axon
Describe the structure of myelin in the PNS
Neurilemma - thick outermost coil of myelin sheath that contains nucleus and most of cytoplasm of Schwann cells
Basal lamina - basement membrane that surrounds myelin sheath, Schwann cells
Endoneurium covers basal lamina, thin exterior layer of fibrous connective tissue (collagen and elastin)
Myelination in the CNS
Oligodenrocyte wraps around multiple axons, but multiple are needed to cover each fiber
Starts 14 weeks after fertilization, breast milk is important for development
Describe the segmented properties of the Myelin sheath
Nodes of Ranvier are gaps between segments
Internodes are the myelin covered segments
Initial segment is the short secition of nerve fiber between axon hillock and 1st glial cell
Trigger zone is the axon hillock and inital segment, role in initating nerve signal
White matter vs gray matter; function and structure
White matter is formed from aggregations of myelinated axons
Gray matter lacks myelin, is formed from neuronal cell bodies and dendrites
Anatomy of a neuron, organelles
Dendrites - highly branches structures that receive signals and conudcts impulses toward Soma
more dendrites = more information
Soma is control center, contains a nucleus, nucleolus, cytoplasm, lysosomes, golgi complex, has extensive RER granules called Nissl bodies which produce neurotransmitters
Cytoskeleton of microtubules and actin, lots of stuff traveling thorugh
Axon conducts impulses away from cell body
Parts of an axon, named portions
Axoplasm - cytoplasm
Axolemma - membrane of axon
Enclosed by Schwann cells and myelin sheath
Axon hillock is space between axon and soma
Initial segment is beginning of axon
Trigger zone is site where action potentials are generated; axon hillock and part of axon nearest cell body
Axon terminal is full of neurotransmitters, sometimes swells into synaptic end bulbs
List the types of neurons, anatomically
Multipolar, bipolar, unipolar, anaxonic
List the types of neurons, physiologically
Afferent, efferent, interneuron
could also be classfied by secretion of neurotransmitter
Describe a multipolar neuron
Has several dendrites and only one axon, located within brain and spinal cord, most common
Describe a Bipolar neuron, what are they used for
Have two rows coming off, the dendrite has just one row before it branches
One main dendrite and one axon
Used for special senses: sight, smell, hearing, balance
retina, eye, inner ear, olfactory area of brain
Describe a unipolar neuron
has one axon that extends from body and divides, goes both directions, functions as both axon and dendritic root depending on direction
touch or stretching
Describe an Anaxonic neuron
many dendrites but no axon
No action potentials
Helps in visual processes
Describe the factors behind conduction speed
Fiber diameter and presence of myelin, temperature also plays a role
Larger fibers have more surface area and conduct signals more rapidly
Myelin further speeds conduction
Different areas need different speeds
How many cranial nerves and spinal nerves are there?
12 pairs of cranial nerves, 31 pairs of spinal nerves
What is necessary for the regneration of nerve fibers
Soma is intact
Some neurolemma remains
Nerve growth factor
What happens to the portion of the nerve fiber distal to the injury during regeneration?
It degenerates
Describe the general steps with regeneration of a nerve fiber?
Normal nerve fiber is cut - degerantion of distal portion, muscle wasting
Regrowth - schwann cells, regeneration tube
Late regeneration - Regeneration tube guides axon
Describe in detail what happens when a normal nerve fiber is cut
without new proteins distal portion degenerates
Macrophages clear debris
Muscle wasting
Soma gets swollen as it can’t send its signals
Nerve growth factor from target cells ceases, must find new source
Describe in detail what happens in the regrowth step of nerve regeneration
Schwann cells come in, produce cell adhesion molecules and nerve growth factor
Regeneration tube forms from schwann cells, basal lamina, neurilemma
Describe in detail what happens during the late regeneration stage of nerve fiber regeneration
Regeneration tube guides growing axon sprout back to synapse and target cell
The nerve is unlikely to innervate the same muscle fiber in the same way, likely attaches to another one
Soma shrinks to its original size, reinnervated fibers regrow
Describe Nerve Growth Factor
Protein secreted by glands, muscles, glial cells that binds to receptors on axon terminals
Prevents apoptosis in growing neurons
Enables growing neurons to make contact with their target cells
Rita Levi-Montalcini isolated in 1950s
What are the two possible types of signals a neuron can communicate with?
Graded potentials/local potentials and action potentials
Compare a graded potential with an action potential
Graded potentials / Local Potentials-
Short-distance communication; signals from dendrites
Reversible, graded
Can be either excitatory or inhibitory, if the graded potential is high enough to make it to the trigger zone an action potential occurs down the axon
Action potentials-
Long-distance communication
Non-reversible
Occurs if the graded potential is high enough
List the steps of an action potential
The resting membrane potential is the level at which the neuron normally sits at.
1) The local potential rises as Na+ slowly depolarize the membrane
2) Threshold is at -55mv, once the threshold is reached voltage-regulated Na+ gates open rapidly, all or none
3) Depolarization of membrane produces a spike in voltage, Na+ gates close as potential passes 0 mV, K+ gates start to open slowly
4) Peak at 35 mV
5) Repolarization as K+ leaves neuron to drop membrane potential back toward RMP
6) Hyperpolarization as K+ stay open long enough to drop potential slightly below RMP
7) Return to RMP
8) Refractory periods
Describe the two refractory periods
Absolute - voltage gated na channels are open, K channels are open, na channels are inactivating
Relative - voltage gated k channels are still open, na channels are resting
Where are the channels needed for an action potential to occur?
Voltage gated are found on axon and axon hillock, needed for action potential
Very few in myelin covered regions, many in nodes of Ranvier
- Fast Na+ diffusion occurs between nodes
- Saltatory conduction is the signal jumping from node to node
How does the body determine perception of stimulus or extent of response
Frequency of neuron firing, number of neurons recruited
Describe the three types of Fibers
A Fibers
-Large, fast, myelinated neurons that carry touch and pressure sensations; many motor neurons are also of this type
B Fibers
-Medium size and speed, myelinated visceral sensory and autonomic preganglionic neurons
C Fibers
-smallest and slowest
Structure of a synapse
Presynaptic neurons have synaptic vesicles containing neurotransmitter
Postsynaptic neurons have receptors and ligand-regulated ion channels
Chemical conduction at a neuron synapse
Calcium converts electrical signals into protein signals, vesicles release their neurotransmitters into synapse, Ligand gated channels on other side
Excitatory and inhibitory neurotransmitters
Both excitatory and inhibitory neurotransmitters are present in the CNS and PNS
Same neurotransmitter may be excitatory in some locations and inhibitory in others
Ex: ACh is released by many PNS neurons, excitatory at some locations and inhibitory in others
Integration
Integration is the process of combining excitatory and inhibitory inputs and responding accordingly
Occurs repeatedly as interneurons are activated in higher parts of the brain (thalamus, cerebral cortex)
Four major parts of the brain
Brainstem, Cerebullum, Diencephalon, Cerebrum
Describe the brainstem, subsections
Containuation of spinal cord with different anatomy and physiology
Medulla oblongata, pons, midbrain, reticular formation
Describe the Medulla oblongata
Contains all ascending and descending tracts between spinal cord and cerebrum
Regulates mandatory body functions
- Cardiovascular center
- Respiratory rhythmicity center
- Vomiting, coughing, sneezing centers
Describe the Pons
Directly above medulla, connects spinal cord with brain
Breathing (inhalation and exhalation)
Describe the Midbrain
Hard to see without dissection, above pons
Contains:
Red nucleus
-Voluntary movements
Cerebral aqueduct for CSF formation and circulation (ependymal cells)
Superior and inferior colliculi
-Visual auditory reflexes
Substantia nigra
- Produces L-dopa -> dopamine
- Parkinson’s association
Describe the Reticular formation
Dorsal to rest of brainstem
Reticular activating system is the ascending portion
- Sensory axons project to cerebral cortex
- Coordinates what goes where, filters out insignificant information
- Maintains consciousness, wake, alertness, sleep
Describe the Cerebellum
“Little Brain”, second largest part
Posture, equilibrium, balance
What three things make up the Diencephalon
Thalamus, Epithalamus, Hypothalamus
Describe the function of the thalamus
Pain, sleep, temperature, pressure is related to thalamus en route to cerebral cortex
Conjunction with attendant memories and emotions evoked
Describe the function of the epithalamus
secretes melatonin; sleep and biological clock
Describe the function of the hypothalamus
Controls homeostatic functions
- Autonomic nervous system
- Coordinates between NS and endocrine system
- Body temperature
- hunger/thirst
- Internal clock
Describe the cerebrum
Largest part
Consists of external gray matter cerebral cortex, internal cerebral white matter, and gray matter nuclei deep within white matter
Mountains: gyri, Valleys: Sulci, Canyon: Fissure
Integration of senses with behavior
Longitudinal fissure separates into right and left hemispheres
Central sulcus divides anterior frontal lobe from parietal lobe
Occipital, parietal, frontal, temporal lobe
Describe the dentate gyrus
part of hippocampal circuit, thought to contribute to formation of new memories in spontaneous exploration of novel environments
Describe the hippocampus
Learning and memory, partially affected in alzheimers
Describe the cranial meninges, list them
Continues with spinal meninges
Mirror their structure and function
Anchors the brain in space
Dura, arachnoid, and pia mater
Dura mater
tough outer layer
external periosteal layer, internal meningeal layer
dense irregular connective tissue, similar to skin
surrounds and supports venous channels carry blood toward the brain
Arachnoid mater
spidery, elastic (dense connective tissue)
Subarachnoid space is filled with cerebrospinal fluid
Pia Mater
thin and delicate
Blood Brain Barrier
Simple squamous vascular endothelium
Astrocytes
Tight junctions
Oxygen, CO2, Water, lipid soluble freely enter and leave CNS; not water soluble
Some travel across through active transport
Cerebral Spinal fluid, 3 Properties
Clear, colorless, produced by ependymal cells
Circulates through brain ventricles and spinal cord and flows over and around the brain and cord in the subarachnoid space
1) Mechanical protection
Brain floats in it, CSF absorbs shock
2) Homeostatic
PH affects bloodflow, etc
3) Circulation
Medium for nutrient and waste transportation
Cranial Nerve I
Olfactory
Cranial Nerve 2
Optic
Cranial Nerve III
Oculomotor
Cranial Nerve IV
Trochlear
Cranial Nerve V
Trigeminal
Cranial Nerve VI
Abducens
Cranial Nerve VII
Facial
CNVIII
Vestibulocochlear
CNIX
Glossopharyngeal
Cranial Nerve X
Vagus
Cranial Nerve XI
Spinal Accessory nerve
Cranial Nerve XIII
Glossopharyngeal nerve
Multiple sclerosis
Oligodendrocytes and mylein sheaths in the CNS deteriorate
Nerve conduction disrupted
Autoimmune disease, BBB breaks down and macrophages come into nerves tissue, destroys myelin
Tay-Sachs disease
Hereditary disorder
Abnormal accumulation of glycolipid called GM2 in myelin sheath
Blindness, loss of coordination, dementia
Fatal before age 4
Leu Gehrigs Disease or ALS
Similar to CET
Correlated to concussions, high contact sports
Nerve fiber dyes, waste of skeletal muscle
Alzheimers Disease
100,000 deaths a year
Memory loss, moody, combative,
Deficiences of ACh and nerve growth factor
Buildup of B-amyloid plaques
Parkinsons
Loss of motor function with no recovery
Degeration of dopamine releasing neurons
Treatment is L-dopa
Brain tumors
Tumors are masses of rapidly dividing cells
Interfere with circuitry
Difficult to treat with BBB
Gliomas are malignant and rapid growth
Einsteins brain, theories of intelligence
Theory 1: More glial cells
Theory 2: Less pronounced Corpus callosum, left and right brain friends
Serial killer brain, theories
Theory 1: Frontal lobe abnormality, less active
Theory 2: Takes multiple parts, orbital cortex involved in ethics and decision making; Warrior gene MAO-A that regulates serotonin; funky childhood
Belief in God, brain activity
Religious people have increased activity in frontal lobe and language areas when in prayer, praying to god is similar to talking to people
Thinking about god alters neural circuitry
Chapman’s Protocol
Sodium pentothal - first used, renders someone unconscious
Pancuronium bromide - paralyzing agent, arrests breathing
Potassium chloride - lowers resting electrical potential, stops heart
Spinal Cord motor vs sensory tracts location
More motor tracts superior, more sensory tracts inferior
Spinal meninges
Dura mater - encloses entire cord
Arachnoid mater - delicate, avascular, attached to dura and forms roof of subarachnoid space where CSF circulates
Pia mater - deepest, transparent, filled with blood and nutrients
Epidural space
between the dura mater and more superficial ligamentum flavum
Epidural anesthesia has a needle placed between bones of posterior spine until it penetrates the ligamentum yet remains superficial to dura mater
Subdural space
Between dura and arachnoid
Potential, dura and arachnoid firmly attached
Lumbar puncture
a needle inserted into the subarachnoid space to withdraw CSF and diagnose or reduce pressure
Typically around L3,L4; below spinal cord
Two enlargements of spine
Cervical area C4 - T1
Motor output and sensory input to/from arms
Lumbar area T9 - T12
Motor output and sensory input to/from legs
Roots
Bundles of axons that connect spinal nerve to cord
Posterior root ganglion contain sensory neurons
ganglion is a group of cell bodies
Anterior root contains motor neurons
Gray and white matter, spinal cord
Gray matter is interior in butterfly shape, integration of IPSPs and EPSPs
Anterior (larger wings), Posterior, Lateral gray horns
White matter contains major sensory and motor tracts
Anterior and posterior lateral columns
Central canal
entire length of cord down the center, filled with CSF
Tracts
Tracts are bundles of neuronal axons all traveling to the same place. PNS
Names combine words that denote origin and ending place
Spinothalamic tract
spinal cord to brain, afferent tract
sensations of pain, warmth, coolness, itching, tickling, deep pressure
Corticospinal tract
brain to spinal cord, efferent tract
Voluntary movement of skeletal muscles
Vestibulospinal tract
brain to spinal cord, efferent tract
Visual stimulus
Spinal Nerves Designation
C1-8, T1-12, L1-5, S1-5, Co1
Spinal Nerve Pairs
Cervical
8 Pairs, C1 - C8
Thoracic
12 Pairs, T1 -T12
Lumbar
5 Pairs, L1 - L5
Sacral
5 Pairs, S1 - S5
Coccygeal
1 Pair
Spinal nerve structure
Axon - ensheathed by endoneurinum
formed by collagen fibers and elastin
Fasicles - surrounded by perineurium
formed by collagen fibers and elastin
Entire nerve - ensheated by epineurium
Formed by fibrous tissue
Branches of spinal nerves
Spinal nerves exit CNS into PNS, split into 3 major branches
Anterior Ramus, Posterior ramus, Rami communicantes
Rami are anterior division of spinal nerves
Nerve Plexuses
A long braided rope of nerves
All anterior to spine
Cervical Plexus, brachial plexus, Celiac solar plexus, Lumbar plexus, Sacral plexus, Coccygeal plexus
Cervical plexus
Anterior rami of C1 - C5
Serves head, neck, diaphragm
Highlighted nerve: Phrenic nerves supply major muscle of respiration
Brachial plexus
Anterior rami of C5-C8 and T1
Serbes shoulders and upper limbs
Divided into roots -> trunks -> divisions -> cords -> nerves
risk takers don’t cautiously behave
Erb’s palsy
paralysis of arm as infants head and neck pulled toward side at same time as shoulders pass through birth canal
Paralysis of arm at any age following trauma
Carpal tunnel syndrome
median nerve injury due to repetive motions of hand and wrist
Highlighted nerve: Ulnar nerve
largest unprotected nerve in human, supplies medial half of hand
striking medial epicondyle of humerus = funny bone
Highlighted nerve: Long thoracic nerve
Supplies serratus anterior
Damage cause winged scapula, arm cannot be abducted byond horizontal position
Lumbar plexus
Anterior rami of L1 - L4
Supplies anterolateral abdominal wall, external genitalia, lower limbs
Highlighted nerve: Femoral and obturator nerves
Sacral plexus
Anterior rami of L4-L5, S1-S4
Sciatic nerve is largest in body
Coccygeal plexus
Anterior rami of S4-S5
Small area of skin in coccygeal region
Damage to the spinal cord
Transection of spinal cord means severing of ascending and descending tracts
At base of skull - death by asphyxiation
Upper cervical area - quadriplegia
Between the cord enlargements - parplegia
Less sensation, can’t sweat, less body hair, can’t cough
Tracts, Nerves, Ganglion, Nucleus, Plexus
Bundle of Axons
Tracks (CNS): A series of axons grouped together in CNS
Nerves (PNS): A bundle of axons and their sheaths that connects CNS to sensory receptors, muscles, and glands
Group of cell bodies
Nucleus (CNS): clusters of neurons
Ganglion (PNS): collection of neuron/nerve cell bodies
Plexus (PNS): extensive network of axons, sometimes neuron cell bodies
