PREFI: NERVOUS SYSTEM Flashcards by Sunwoo's Berry

Most complex system formed by a network of nerve cells (neurons) assisted by many more supporting cells (glial cells)

NERVOUS SYSTEM

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CNS IS CONSIST OF?

BRAIN AND SPINAL CORD

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white matter?

axons predominate

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grey matter?

neuronal perikaryal predominates

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PERIPHERAL NERVOUS SYSTEM IS CONSIST OF?

cranial, spinal, and peripheral nerves; ganglia

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FUNCTIONAL DIVISION
a. Somatic: sensory input perceived
consciously
b. Visceral: sensory input not perceived
consciously

SENSORY DIVISION (afferent)

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FUNCTIONAL DIVISION
a. Somatic: motor output controlled
consciously or voluntarily
b. Autonomic: motor output not
controlled consciously

MOTOR DIVISION (efferent)

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gathers information

SENSORY INPUT

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process and interpret sensory input; decides if action is needed

INTEGRATION

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RESPONSE to integrated stimuli by activating muscles or glands

MOTOR INPUT

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Develops from the ectoderm
Begins in 3rd-4 th week of development

NERVE TISSUE

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gives rise to both spinal cord and brain

Neural plate

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functional unit of nervous system

NEURONS

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has one axon and two or more dendrites; most common

MULTIPOLAR NEURON

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has one axon and one dendrite

BIPOLAR NEURONS

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has all other sensory neurons with each having a single process

UNIPOLAR OR PSEUDOUNIPOLAR NEURONS

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has many dendrites but no true axon

ANAXONIC NEURONS

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SUPPORT NEURONAL SURVIVAL and activities
Share the same development with
neurons, from the embryonic neural plate

GLIAL CELLS

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GLIAL CELLS IN THE CNS
* Unique feature: proximal regions are
reinforced with bundles of intermediate filaments (glial fibrillary acid protein)
a. Helps form the blood-brain barrier
b. Regulates the ISF composition
c. Provides structural support and
organization to the CNS
d. Assists the neuronal development
e. Replicates to occupy space of dying neurons

ASTROCYTES

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TYPE OF ASTROCYTES
- long processes, ABUNDANT IN WHITE MATTER

FIBROUS ASTROCYTES

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TYPE OF ASTROCYTES
- short processes, abundant in gray matter

PROTOPLASMIC ASTROCYTES

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GLIAL CELLS IN THE CNS
- Lines ventricles of brain and central canal of spinal cord
- Assists in production and circulation of CSF

EPENDYMAL CELLS

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GLIAL CELLS IN THE CNS
* EVENLY DISTRIBUTED within WHITE and GRAY MATTER
* Originate from circulating blood monocytes
a. Phagocytic cells moving through CNS
b. PROTECTS CNS by engulfing infectious
agents and other potentially harmful
substances

MICROGLIAL CELLSL

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GLIAL CELLS IN THE CNS
* PREDOMINANT glial cell in white matter
* White color: due to lipid concentrated in the wrapped myelin sheaths
a. Myelinates and insulates CNS axons
b. Allows faster action potential propagation along axons in the CNS

OLIGODENDROCYTE

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GLIAL CELLS IN THE PNS - Electrically insulates PNS cell bodies - Regulates nutrient and waste exchange for cell bodies in ganglia

SATELLITE CELLS

GLIAL CELLS IN THE PNS * Found only in the PNS * Named after Theodor Schwann a. Surround and insulate PNS axons and myelinate those with large diameters b. Allows faster action potential propagation along an axon in the PNS

NEUROLEMMOCYTE (SCHWANN CELLS)

Clinical Significance - Brain tumor originating from fibrous astrocytes - Symptoms: headaches, seizures, nausea, vomiting, vision problems, cognitive and behavioral changes

ASTROCYTOMA

CLINICAL SIGNIFICANCE - Common type of dementia in the elderly, affecting both neuronal perikaryal and synapses within the cerebrum * Functional defects are caused by neurofibrillary tangles (accumulation of tau protein) and neuronal plaques (dense aggregates of β-amyloid protein)

Alzheimer’s disease

GLIAL CELL TYPE Origin: neural tube Location: CNS Main functions: myelin production, electrical insulation

OLIGODENDROCYTE

GLIAL CELL TYPE Origin: neural type Location: CNS Main functions: structural and metabolic support of neurons, especially at synapses; repair processes

ASTROCYTE

GLIAL CELL TYPE Origin: neural type Location: line ventricles and central canal of CNS Main functions: aid production and movement of CSF

EPENDYMAL CELL

GLIAL CELL TYPE Origin: bone marrow (monocyte) Location: CNS Main functions: defense and immune-related activities

MICROGLIA

GLIAL CELL TYPE Origin: neural crest Location: peripheral nerves Main functions: myelin production, electrical insulation

SCHWANN CELL

GLIAL CELL TYPE Origin: neural crest Location: peripheral ganglia Main functions: structural and metabolic support for neuronal cell bodies

SATELLITE CELLS (of ganglia)

- Gradual destruction of myelin sheaths around the axons by an autoimmune mechanism - Myelin sheaths are converted into hardened sheaths or scleroses

MULTIPLE SCLEROSIS

- Electrical charge travelling along the membrane of a neuron - Converts electrical signal from the presynaptic cell into a chemical signal that affects postsynaptic cell

NERVE IMPULSE/ ACTION POTENTIAL

sites where nerve impulse are transmitted from one neuron another or to effector cells

SYNAPSES

action of nerve impulse

release NEUROTRANSMITTERS

used at neuromuscular junctions

ACETYLCHOLINE

CAUSES Na CHANNELS TO OPEN = Na influx initiates depolarization wave

Excitatory synapses

CAUSES Cl OR OTHER ANION CHANNELS TO OPEN= anions influx and hyperpolarization ofthe postsynaptic cell

Inhibitory synapses

Clinical Significance * GRADUAL LOSS BY APOPTOSIS of DOPAMINE producing neurons whose cell bodies lie within the nuclei of the CNS (substantia nigra) * Slowly progressing disorder AFFECTING MUSCULAR ACTIVITY * TREMORS, , reduced activity of the facial muscles, loss of balance, postural stiffness * Treatment: ʟ-dopa (L-3,4 dihydroxyphenylalanine): precursor of dopamine augmenting the declining production of this neurotransmitter

Parkinson’s disease

* Neuronal pathway by which a REFLEX OCCURS

REFLEX ARC

stimulate the SKELETAL muscles

Somatic reflex

regulate the activity of SMOOTH muscles, heart, and glands

Autonomic reflex:

CNS - found in DEEPER REGIONS with myelinated axons (tracts) and oligodendrocytes

White matter:

CNS - makes up the CORTEX or the SURFACE LAYER OF THE BRAIN with unmyelinated axons, abundant cell bodies, dendrites, astrocytes, and microglial cells

Gray matter

DARKER AREA OF THE BRAIN containing large numbers of cell bodies

CEREBRAL NUCLEI

REGIONS OF THE BRAIN: o “cerebrum”, “seat of intelligence” o Largest part of the brain o Cortex: superficial, gray matter o White matter: internal area o Basal nuclei: islands of gray matter deep within the white matter

CEREBRAL HEMISPHERE

REGIONS OF THE BRAIN: o Deep within the brain o Responsible for relaying sensory information between brain regions

Diencephalon “interbrain”

Diencephalon “interbrain”: - RELAY STATION for sensory impulses passing upward to the sensory cortex

THALAMUS

Diencephalon “interbrain”: - REGULATES BODY TEMPERATURE, WATER BALANCE , and METABOLISM - center for many drives and emotions - REGULATES PITUITARY GLAND and produce two hormones of its own

HYPOTHALAMUS

Diencephalon “interbrain”: - : forms the ROOF of the 3rd ventricle ▪ Important parts: pineal gland and choroid plexus of the 3rd ventricle

EPITHALAMUS

REGIONS OF THE BRAIN: o Attached to the spinal cord o Responsible for controlling many VITAL FUNCTIONS needed for SURVIVAL: heart rate, breathing, and blood pressure o Important parts: midbrain, pons, and medulla oblongata

BRAIN STEM

BRAIN STEM IMPORTANT PARTS: - contains VISUAL and AUDITORY reflex centers - contains subcortical motor centers

MIDBRAIN

BRAIN STEM IMPORTANT PARTS: - relays information from the cerebrum to the cerebellum - cooperates with the medullary centers to control respiratory rate and depth

PONS

BRAIN STEM IMPORTANT PARTS: - relays ASCENDING SENSORY PATHWAY impulses from skin and proprioceptors - contains nuclei controlling heart rate, blood vessel diameter, respiratory rate, vomiting, etc - relays sensory information to the cerebellum

MEDULLA OBLONGATA

REGIONS OF THE BRAIN: o Has two hemispheres and a convoluted surface o Provides INVOLUNTARY COORDINATION of body movements, controlling BALANCE & EQUILIBRIUM

CEREBELLUM

Clinical Significance * Inflammation of the meninges * May be caused by viruses, bacteria, or other microorganisms

Meningitis

inflammation due to spread of meningitis to the nervous tissue of CNS

Encephalitis

* Neurological disorder characterized by CLUMSY or DISORGANIZED MOVEMENTS * May be a result of DAMAGED CEREBELLUM * Individuals cannot keep their balance and may appear to be drunk because of the loss of muscle coordination

Ataxia

* Genetic disease leading to MASSIVE DEGENERATION OF THE BASAL NUCLEI and later of the CEREBRAL CORTEX * Initial symptoms: wild, jerky movements, and chorea * Later symptoms: marked mental deterioration occurs * Terrible three: along with Alzheimer’s disease and Parkinson’s disease

Huntington’s disease

Protection of the CNS: - Connective tissue between the bone and nervous tissue

Meninges

Thick EXTERNAL LAYER made of dense irregular connective tissue

Dura mater

o WEBLIKE MIDDLE LAYER with avascular connective tissue o Has two components: ▪ Sheet of connective tissue in contact with the dura mater ▪ System of loosely arranged trabeculae that is continuous with the pia mater layer o Subarachnoid space: large, spongelike cavity filled with CSF surrounding the trabeculae

Arachnoid

o INNERMOST LAYER o Does not directly contact nerve cells or fibers, clings to the brain surface

Pia mater

* Functional barrier designed to PROTECT THE BRAIN AND SPINAL CORD from potentially harmful substances and microorganisms * Useless against fats, respiratory gases, and fat-soluble molecules: alcohol, nicotine, anesthesia

Blood-Brain Barrier

Main structural component of Blood-Brain Barrier

capillary endothelium

* REMOVES WATER FROM BLOOD and release it as CSF * Consists of highly vascular tissue, elaborately folded and projecting into the large ventricles of the brain * Found in the roofs of the 3rd and 4th ventricle and in parts of the two lateral ventricular walls

Choroid Plexus

similar to blood plasma in composition and forms a WATERY CUSHION to protect the brain

CSF

contains a THIN LAYER of WELL VASCULARIZED PIA MATER covered by cuboidal ependymal cells

Villus

Clinical Significance - DECREASE IN THE ABSORPTION OF CSF or excess accumulation of CSF in the ventricles during fetal or postnatal development * Promotes progressive enlargement of the head followed by mental impairment * Treatment: surgery by INSERTING SHUNT to drain excess fluid

Hydrocephalus

Consists of nerves, ganglia, and nerve endings

PNS (Peripheral Nervous System)

- BUNDLE OF NEURON FIBERS - Contains axons enclosed with sheaths of glial cells specialized to facilitate axonal function

NERVES

Connective tissue sheath: - surrounds each FIBER

Endoneurium

Connective tissue sheath: - surrounds EACH fascicle

Perineurium

Connective tissue sheath: - surrounds ALL fascicle

Epineurium

CLASSIFICATION OF NERVES: - carry impulses TOWARDS CNS

Afferent (sensory) nerve:

CLASSIFICATION OF NERVES: - carry impulses AWAY from the CNS

Efferent (motor) nerve

CLASSIFICATION OF NERVES: - both sensory and motor fibers

Mixed nerve

Autonomic Nervous System: o “fight-or-flight” response: ▪ Response to unusual stimulus ▪ Takes over to increase activities o “E” division: exercise, excitement, emergency, and embarrassment

Sympathetic division

Autonomic Nervous System: o Allows us to UNWIND and CONSERVE ENERGY o “resting-and-digesting” system: ▪ Response to usual stimulus ▪ Maintains daily necessary body functions o “D” division: digestion, defecation, and diuresis (urination)

Parasympathetic division