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OUTLINE
I. Organization of the Nervous System A. The Nervous System B. Structural Classification C. Functional Classification II. Nervous Tissue: Structure and Function A. Supporting Cells B. Neuron C. Electrical Signals and Neural Pathways III. Central Nervous System A. Anatomy of the Brain B. Spinal Cord IV. Peripheral Nervous System A. Structure of the Nerve B. Cranial Nerves C. Spinal Nerves D. Autonomic Nervous System
- The Nervous System is the master control and communication system
- Considered as the most COMPLEX system of the body
- It communicates with body cells with
electrical impulses, which are rapid, specific, and cause immediate response.
- Formed by a network of many billion nerve cells (neurons), all assisted by many more supporting cells (glial cells)
- The nervous tissue is distributed throughout the body as an integrated communication network
- The Nervous system’s function: o Sensory Input – monitor stimuli occurring inside and outside the body o Integration – process and interprets the sensory input and decides what should be done in each moment o Motor Input – cause a response/effect by activating muscles or effector glands
o The Nervous system is divided into two (2) General division: Central Nervous System 90(CNS) and the Peripheral Nervous System (PNS)
o Mainly consist of brain and spinal cord , which occupies the dorsal/posterior cavity of the body o Acts as integrating and command centers of the Nervous system o Interprets the incoming sensory information and issue instructions
o o Includes all parts of the nervous system outside of CNS o Consist mainly of spinal and cranial nerves o Spinal nerves carry impulses to and from the spinal cord while Cranial nerves carry impulses to and from the brain o Serve as the communication lines
- The functional classification scheme is concerned only with PNS structure, and it divides into two (2) principal subdivision: Sensory division and motor division
- Sensory division is also referred to as Afferent while for Motor division it is referred to as Efferent
HUMAN ANATOMY AND PHYSIOLOGY WITH
PATHOPHYSIOLOGY
THE NERVOUS SYSTEM
LECTURED BY: JUSTO GILVERT DE JESUS
Transcribed by: T.J.A
I. Organization of the Nervous System
Peripheral
Nervous System
Sensory/Afferent
Division
Motor/Efferent
Division
Autonomic
Nervous
System
Somatic
Nervous
System
Sympathetic Parasympathetic
A. THE NERVOUS SYSTEM
B. STRUCTURAL CLASSIFICATION
C, FUNCTIONAL CLASSIFICATION
Nervous System
Central Nervous
System
Peripheral
Nervous System
CENTRAL NERVOUS SYSTEM (CNS)
PERIPHERAL NERVOUS SYSTEM (PNS)
SENSORY/AFFERENT DIVISION
- It consists of nerves that convey impulses to the CNS from sensory receptors from various parts of the body
- The sensory division keeps the CNS constantly informed from both inside and outside of the body
MOTOR/EFFERENT DIVISION
- Carries impulses from CNS to effector organs,
muscle, and glands.
- The motor/effector division is divided into two (2) subdivision: Somatic NS and Autonomic NS Somatic Nervous System (SNS) o a.k.a VOLUNTARY Nervous system o allows us to control our skeletal muscle consciously/voluntarily Autonomic Nervous System (ANS) o a.k.a INVOLUNTARY Nervous System o Regulates events that are automatic or involuntary o Divided into two (2) parts: Sympathetic and Parasympathetic
1.) Sympathetic NS – controls the “fight- or-flight” response that prepares the body for strenuous physical activity
- Active in stressful condition 2.) Parasympathetic NS – regulate the “rest-and-digest” response and brings the body to a state of calm
- Active during relaxing time
- Neuroglia is supporting cells of the CNS. Together they are termed as Neuroglia (Nerve Glue)
- Sometimes referred to as Glial Cells or Glia
- CNS neuroglia consist of the following:
Astrocytes – Star-shaped cells that account for nearly half of the neural tissue recapturing chemicals released from communication (also formed blood-brain barrier
Microglia – spiderlike phagocytes that monitor the health or nearby neurons and dispose of debris, such as dead brain cells and bacteria
Ependymal Cells – neuroglia that line the central cavities of the brain and the spinal cord. The beating of their cilia helps to produce and circulate the CSF that fills those cavities and forms a protective watery cushion around the CNS.
Oligodendrocytes - neuroglia that wrap their flat extensions (processes) tightly around the nerve fibers, producing fatty insulating coverings called myelin sheaths (Myelin sheaths for CNS)
- In the PNS, there are two (2) major supporting Cells: Schwann Cells and Satellite Cells
Schwann Cells – A type of glial cell of the peripheral nervous system that helps separate and insulate nerve cells. (Myelin sheaths for PNS)
Satellite Cells – Act as protective, cushioning cells for PNS
II. Nervous Tissue: Structure & Function
A. SUPPORTING CELLS
SENSORY/AFFERENT DIVISION
MOTOR/EFFERENT DIVISION
The Nerve Impulse
1.) Resting membrane is Polarized (at rest)
The external membrane is positive while the internal membrane is negative. The membrane is relatively impermeable to both ions (𝑁𝑎+and 𝐾+)
2.) Stimulus initiate local depolarization
A stimulus changes the permeability of a local patch of the membrane and Sodium ions will diffuse rapidly to the membrane. It will change the polarity of the membrane
3.) Depolarization and generation of an action potential
If the stimulus is strong enough, depolarization causes membrane polarity to be completely reversed, and an action potential is initiated.
4.) Propagation of the action potential
Depolarization of the first membrane patch causes permeability changes in the adjacent membrane. Thus, the action potential propagates rapidly along the entire length of the membrane.
5.) Repolarization
Potassium ions diffuse out of the cell as the membrane permeability changes again, restoring the negative charge on the inside of the membrane and the positive charge on the outside surface
6.) Initial ionic conditions restored
The ionic conditions of the resting state are restored later by the activity of the sodium- potassium pump. Three sodium ions are ejected for every two potassium ions carried back into the cell.
- Neurons are not properly connected but they signal each other
- Remember that electrical impulses DOES NOT travel from one neuron to another neuron.
- A Neurotransmitter chemical CROSSES the synapse to transmit the signal from one neuron to another
- Synapses: o A junction that mediates information from one neuron to another neuron or effector organ o Presynaptic Neuron – conduct impulses towards the synapse Postsynaptic Neuron – transmit the impulses away from the synapse o What separates these two synapses is the space between them and it is called the Synaptic Cleft
1.) Action Potentials or Nerve (electrical) Impulses reaches the axon terminal of the presynaptic neuron
2.) Calcium ions, in turn, cause the tiny vesicles containing neurotransmitter to fuse with the axonal membrane and releases neurotransmitter
3.) Neurotransmitter molecules diffuses from the presynaptic terminal to the synaptic cleft
4.) The neurotransmitter combines with the receptor site on the postsynaptic neurons
5.) Postsynaptic membrane permeability to ions changes, causing an excitatory or inhibitory effect depending on the ions controlled
THE NERVE IMPULSES
TRANSMISSION OF SIGNAL AT THE SYNAPSE
TRANSFERRING OF INFORMATION IN THE
SYNAPSES
Neurotransmitter
- Chemicals used for neuronal communication with the brain and the body
- 50 different neurotransmitters have been identified
- Chemical Neurotransmitter Acetylcholine – 1 st^ Neurotransmitter identified Biogenic Amines – Broadly distributed in the brain and responsible for emotional behaviors and our biological clock o Catecholamines – dopamine, norepinephrine, and epinephrine o Indolamines – serotonin and histamine Amino Acids - includes GABA, glycine, aspartate, and glutamate that are only found in the CNS Peptides Novel Messengers
- Functional Classification of Neurotransmitter Depolarization – cause from Excitatory Neurotransmitter Hyperpolarization – cause from Inhibitory Neurotransmitter
- The Brain is the biggest and complex mass of Nervous tissue in the body
- The Brain is divided into 4 major groups: Cerebral Hemisphere, Diencephalon, Cerebellum, and Brain stem
Cerebral Hemisphere
- Also called as TELENCEPHALON
- They are divided by left and right Hemisphere, and they are collectively called as Cerebrum
- It is the most superior part of the brain and together are a good deal larger than the other three brain regions combined.
- The surface of the Cerebrum exhibits elevated ridges of tissue called gyri (plural), separated by shallow grooves called sulci - The deeper grooves or sulci are called fissures. This separates large regions of the brain. - The cerebral hemisphere is separated by a single deep fissure called Longitudinal Fissure - Other fissures or sulci divide the cerebral hemisphere into number of lobes
The red line shows the deep fissure of the brain called Longitudinal Fissure
- Cerebral Hemisphere is divided into 3 regions:
Cerebrum Regions
Functions
Cerebral Cortex (Gray Matter)
- Located at outer layer of the cerebrum
- Higher level of human processes such as speech, memory, interpretation, movements, etc. Cerebral White Matter
- Lies within the deep cerebral hemisphere
- Its job is to process, conduct, send nerve signals up and down of the spinal cord Basal Nuclei - Buried within the white matter
- Helps to regulate voluntary motor activities by modifying instructions
- HOMOESTATIC IMBALANCE When a person has problems to their BASAL NUCLEI, this person is unable to walk properly or carry out voluntary movement’s examples are Huntington’s Disease and Parkinson’s Disease
- The brain is divided into left and right hemisphere and the Corpus Callosum is a large fiber tract that connects the Left and right Hemisphere (located in the white matter)
- The brain is divided by lobes
A. ANATOMY OF THE BRAIN
III. Central Nervous System
NEUROTRANSMITTER
CEREBRAL HEMISPHERE / TELENCEPHALON
the diencephalon to the fourth ventricle below. Cerebral Peduncles – two bulging fiber tract that convey ascending and descending impulses
Pons - rounded structure that protrudes just below the midbrain
- Pons means ‘bridge’
- Consist of mostly fiber and providing route for signals to travel to and from the brain
Medulla Oblongata
- a.k.a MYLENENCEPHALON
- Most inferior part of the brain stem
- It merges into the spinal cord without any obvious change
- Controls AUTONOMIC function such as controls heart rate, blood pressure, breathing (respiration), and swallowing
Cerebellum
- Also called as METENCEPHALON
- A large cauliflower-like cerebellum and it
projects dorsally from the under the occipital lobe of the cerebrum
- It is also known as “Little Brain”
- The cerebellum has the same characteristic of the cerebrum such as having two hemispheres. It also has an outer cortex made up of gray matter and the inner region which is the white matter
- The cerebellum provides the precise timing for skeletal muscle activity and controls our balance. EQUILIBRIUM
- HOMOESTATIC IMBALANCE If the Cerebellum is damaged, movements of a human body become clumsy and disorganized – this condition is called Ataxia
- Take note that SPINAL COLUMN/SPINE is the connected and stacked BONES while SPINAL CORD is the NERVES
- Long, thin, tubular bundle of nerves that is an extension of the CNS from the brain and is enclosed in and protected by the bony vertebral column
- Provides two-way conduction pathway to
and from the brain, and it is a major reflex center.
- Connects the brain and the PNS
- 45cm long in men while 43cm for women
- Cushioned and protected by MENINGES
- The Meninges is consisting of three layers: 1.) Dura Mater (Tough Mother)
- Superficial and the thickest layer 2.) Arachnoid Dura Mater (Spider web-like) -2nd^ layer of the meninges 3.) Pia Mater (Tender Mother) -3rd^ layer and the surface of the spinal nerve/brain
Gray Matter of The Spinal Cord
- The gray matter of the spinal cord looks like a butterfly shaped or letter H in cross sections
- It contains the following parts:
1.) Dorsal/Posterior Horns – contains axon which synapse with interneurons
2.) Ventral/Anterior Horns – contains somatic neurons
3.) Lateral Horns – contains autonomic neurons
4.) Central Canal – fluid filled space in the center or the cord which contains the CSF
White Matter of The Spinal Cord
- White matter of the spinal cord is composed of myelinate fiber tracts
- It is composed of nerve fibers carrying ascending and descending information and makes up the outer regions of the cord
- Ascending tracts: action potential TOWARDS the brain
- Descending tracts: action potentials AWAY from the brain
- Divided into three (3) regions:
1.) Dorsal Column 2.) Lateral Column 3.) Ventral Column
B. SPINAL CORD
CEREBELLUM / METENCEPHALON
SPINAL CORD SEGMENT
- There are 31 pairs of spinal nerves arise from the cord and exit from the vertebral column to serve the body area close by.
1.) 8 Cervical Segment
- Cervical nerves exit spinal column above C1 and below C1-C
2.) 12 Thoracic Segments
- Thoracic nerves exit spinal column and below T1-T
3.) 5 Lumbar Segments
- Lumbar nerves exit spinal column and below L1-L
4.) 5 Sacral Segments
- Sacral nerves exit spinal column and below S1- S
5.) 1 Coccygeal Segments
- Coccygeal nerves exit spinal column and below at coccyx
- Consist of nerves ang scattered ganglia (groups of neuronal cell bodies found outside the CNS)
- It exposed to toxins and mechanical injuries
- Provides communication lines between CNS and the body’s muscle, glands, and receptors
- It puts the Brain in touch with the physical environment, and allows it to respond
- A nerve is a bundle of neuron fibers found outside the CNS.
- Within a nerve, neuron fibers , or processes , are wrapped in protective connective tissue coverings.
- The armlike processes, or fibers, vary in length from microscopic to about 7 feet in the tallest humans. The longest ones in humans reach from the lumbar region of the spine to the great toe.
- Each nerve is surrounded by delicate connective tissue sheath called endoneurium
- Group of fibers are bound by a coarser connective tissue by perineurium to form fiber bundle or fascicles
- All fascicles are bound together by tough fibrous sheath called the epineurium
- Nerves are classified by their transmission of impulses.
Sensory (afferent) nerves – carry impulses towards CNS Motor (efferent) nerves – carry impulses with the information from CNS towards the muscles or skeletal. Mixed Nerves – carries both sensory and motor fibers
- There are primarily 12 pairs of Cranial Nerves that serves the head and the neck
- Only the Vagus nerves extends to thoracic and abdominal cavities
- Cranial nerves are numbered in sequence , and most of their names reveals the most important structure they control
- Most cranial nerves are mixed nerves; however, only three pairs of nerves are purely sensory in function such as: Optic, Olfactory, and Vestibulocochlear
- Other name for Vestibulocochlear is Acoustic nerve (pertaining only for the sense of hearing )
- Below are the 12 cranial nerves arranging in sequence:
CRANIAL Origin/Function CN I. Olfactory Nerve
- Carry impulses for the sense of smell
CN II. Optic Nerve
- Carry impulses for the sense of vision
CN III. Oculomotor Nerve
- controls lens shape and pupil size (Pupil dilation)
- For eye movement (eyeball, eyelids, and internal eye muscle)
CN IV. Trochlear Nerve
- motor fibers for the superior oblique eye muscle (For vertical eye movement)
CN V. Trigeminal Nerve
- conduct sensory impulses from the skin of the face (Skin sensation)
- motor fibers that activate the chewing muscle
CN V1. Abducens Nerve
- motor fibers to lateral rectus muscle (For lateral movement of eye) CN V11. Facial Nerve
- Activates muscles for facial expression.
IV. Peripheral Nervous System
A. STRUCTURE OF THE NERVE
B. CRANIAL NERVES
pupils, cold, sweaty skin, and dilates the bronchioles.
Parasympathetic Division
o They are the ‘housekeeper’ of the body o It is most active during when the body is at rest and not threatened in any way. o Often referred to as the ‘rest-and-digest’ or ‘rest-and-repose’ response o Conserves the body energy o Chiefly concerned with promoting normal digestion and elimination of feces and urine and with conserving body energy, particularly by decreasing demands on the cardiovascular system
Pathophysiology of the Nervous System
(Based on the Lecture/PPT provided)
Multiple Sclerosis
- An autoimmune disease that mainly affects young adults Symptoms include visual disturbances, weakness, loss of muscular control, and urinary incontinence
- Nerve fibers are severed and myelin sheaths in the CNS become nonfunctional scleroses
- Shunting and short-circuiting of nerve
impulses occurs
- Treatments include injections of methylprednisolone and beta interferon
- The cause of this disease is UNKNOWN
Neurotransmitter Deficiencies
- Norepinephrine Deficiency
- leads to insatiable hunger, inability to focus or concentrate, exhaustion and carbohydrate cravings.
- Serotonin Deficiency
- leads to runaway levels of epinephrine and norepinephrine resulting in depression, anxiety, panic attacks, cravings, irritability, aggressiveness, and phobias.
- Dopamine Deficiency
- linked with depression, burn-out, lack of motivation, and decreased libido (or sexual desire) also cravings.
- Epinephrine Deficiency
- is seen in cases of adrenal exhaustion.
Parkinson’s Disease
- A progressive, degenerative disease-causing destruction of nerve cells in the basal ganglia of the brain caused by a deficiency of dopamine
ALS Amyotrophic Lateral Sclerosis
- is a rare neurological disease that primarily affects the nerve cells (neurons) responsible for controlling voluntary muscle movement
Action potential - Nerve impulse Afferent neuron - Sensory nerve that carries impulses toward the central nervous system
Autonomic nervous system - Subdivision of the nervous system responsible for regulating activities that maintain homeostasis; also called visceral motor system Axon - Fiber extending from a neuron’s cell body that conducts impulses Brainstem - Stem-like portion of the brain that connects the cerebral hemispheres to the spinal cord; consists of the midbrain, pons, and medulla oblongata Central nervous system - Portion of the nervous system consisting of the brain and spinal cord Cerebellum - Portion of the brain responsible for coordination of voluntary movement and balance Cerebral cortex - The surface of the cerebrum consisting of a thin layer of gray matter Cerebrospinal fluid - Clear, colorless fluid that fills the brain’s ventricles and central canal and also bathes the outside of the brain and spinal cord Cerebrum - Largest portion of the brain Cranial nerves - Nerves of the peripheral nervous system that arise directly from the brain (instead of from the spinal cord)
Efferent neuron - Motor nerve that carries impulses away from the central nervous system Frontal lobe - Portion of the cerebrum responsible for decision making, reasoning, memory, and voluntary movements Gray matter - Nervous tissue containing mostly cell bodies of motor neurons and interneurons Hypothalamus - The bottom half of the diencephalon of the brain, which is responsible for many vital body functions Limbic system - Complex set of structures in the brain responsible for emotion and learning Medulla oblongata - Attaches brain to spinal cord; contains centers that govern heart rate, blood pressure, and breathing Meninges - Layer of fibrous connective tissue covering the brain and spinal cord Mixed nerve - Nerve that contains both sensory and motor fibers
TERMINOLOGIES TO REMEMBER
PARASYMPATHETIC DIVISION
Myelin - Fatty sheath encasing the axons of many neurons; formed by Schwann cells in the peripheral nervous system and oligodendrocytes in the central nervous system
Nerve - A bundle of neurons that transmits impulses between the brain and spinal cord and the rest of the body
Neuroglia - Cells in the nervous system that support neurons but do not conduct impulses
Neurons - Nervous system cells that conduct impulses
Occipital lobe - Portion of the cerebrum responsible for analyzing and interpreting visual information
Parasympathetic division - Division of the autonomic nervous system that primarily has a calming effect; also called craniosacral division
Parietal lobe - Portion of the cerebrum concerned with bodily sensations and proprioception
Peripheral nervous system - Portion of the nervous system consisting of the network of nerves throughout the body
Plexus - A network of nerves
Polarization - The electrical state of a cell membrane that has an excess of positive ions on one side of the membrane and an excess of negative ions on the other
Reflex arc - A neural circuit that bypasses regions of the brain were conscious decisions are made
Somatic reflex - Reflex involving contraction of a skeletal muscle after being stimulated by a somatic motor neuron
Sympathetic division - Division of the autonomic nervous system responsible for “fight or flight” response; also called thoracolumbar division
Synapse - Space between the junction of two neurons in a neural pathway
Temporal lobe - Portion of the brain responsible for hearing, smell, and visual recognition
Tracts - Bundles of axons in the spinal cord that serve as routes of communication to and from the brain
Visceral reflexes - Reflex of the autonomic nervous system affecting organs
White matter - Nervous tissue containing bundles of axons that carry impulses from one part of the nervous system to another
