1. NERVOUS SYSTEM

2. Introduction Most highly organized system of the body
Fast, complex communication system that regulates thoughts, emotions, movements, impressions, reasoning, learning, memory, choices
Basic Characteristics
Master control system
Master communication system
Regulates, maintains homeostasis

3. Major Structures and Divisions
Central nervous system (CNS)
Peripheral nervous system (PNS)
Automatic Nervous System
Major structures are the brain, spinal cord, nerves and sensory organs
Organization of the Nervous System – CNS, PNS, and ANS

4. Functions Monitors change (stimuli) - sensory input
Integrates impulses - integration
Effects responses - motor output
The function of the nervous system is:
To sense, interpret, and respond to internal and external environmental changes in order to maintain a steady state in the body’s homeostasis

5. Histology of Nervous Tissue
Basic Characteristics
Highly cellular
2 types of cells - neurons and supporting cells (neuroglia)

6. Neuroglia Characteristics
Dense network of supporting cells for nerve tissue
Over 900 billion
CAN replace themselves
Also known as glia cells (glia = glue)
Supportive scaffolding; insulation; neuron health and growth (act as “glue” to support, bind, repair, and protect neurons)
Another type of cell in the nervous system besides neurons is Neuoglia or glial cells
Special nervous tissue cells that act as “glue” to support, bind, repair, and protect neurons

7. Neurons: Basic Characteristics
Over 100 billion
Highly specialized
Conduct messages in form of nerve impulses
Extreme longevity (>100 years)
High metabolic rate
3 functional components in common: receptive/input regions, conducting component/trigger zone, secretory/output component
Three types
A = afferent (sensory)
C = Connective (associative)
E = Efferent (motor)
-The brain is made of nerve cells (neurons) which communicate with each other at places called synapses.
-There are about 100 billion neurons in the human brain and each has about 10,000 contacts with other neurons.
Three types
A = afferent (sensory)
C = Connective (associative)
E = Efferent (motor)
Neurons
Characteristics
Excitability: the ability to react to a stimuli, physical or chemical
Irritability: sensory adaptation, with prolonged stimulation, irritability is temporarily lost (i.e. smell)
Conductivity: the ability to transmit an impulse
Nonmyelinated fibers = meter /sec (1 mph)
Myelinated fibers = meters/sec (300 mph)

8. Neurons: Characteristics
Excitability: the ability to react to a stimuli, physical or chemical
Irritability: sensory adaptation, with prolonged stimulation, irritability is temporarily lost (i.e. smell)
Conductivity: the ability to transmit an impulse
Nonmyelinated fibers = meter /sec (1 mph)
Myelinated fibers = meters/sec (300 mph)

9. The Hand as a Neuron

10. A Closer Look: Parts of a Neuron
nucleus
terminal axon
soma
axon
-The cell body is referred to as the soma. It contains the nucleus (DNA) of the cell. If the soma is damaged, a neuron will not recover.
-The dendrites are multiple branches that come off the soma. Dendrites
Short, tapering diffusely branched (tree-like) fibers
Carry impulses toward the cell body from sensory receptors or other axons
They receive nerve impulses from other neurons.
-The single fiber coming off the soma that is thicker and longer than then dendrites is called the axon. Axons convey information to adjacent neurons.
-Axons are Long, slender fiber that transmits impulses away from the cell body
One per neuron
Short, absent, or long (great toe - lumbar region: 3 to 4 feet = longest cells in body)
Long are called nerve fibers
Largest in diameter = most rapid conduction
Distal tip of axon ends in synaptic knob or end plate are covered in a lipid/protein called the myelin sheath. This sheath insulates the neuron and helps electrical impulses travel smoothly and quickly from one neuron to another.
myelin sheath
dendrites

11. Myelin Sheath
Whitish, fatty (protein lipoid) segmented covering of axons
Myelinated fibers: conduct nerve impulses rapidly; electrical insulation
Unmyelinated fibers: conduct impulses slowly
White matter: myelinated sheaths around axons of the PNS gives the tissue a white color and forms myelinated nerves (axons = myelinated tracts)
Gray matter: concentrations of cell bodies and unmyelinated fibers ( in PNS = ganglia; in CNS = nuclei)

12. Neurophysiology—Chemical Events At the Synapse

13. The Synapse
the dynamic region between an axon terminal and a receiving neuron
space between a terminal axon and receiving neuron is called the synaptic cleft
synaptic cleft is where electrochemical transmission takes place, thus communication
Impulses from one neuron are transmitted across the synapse to another neuron by a chemical called a neurotransmitter

14. Vesicles release Neurotransmitters4
synapse
-Chemicals are made in the soma (1 & 2) and stored in small vesicles at the tip of the axon (3).
-An electrical impulse (4) travels from the soma to the axon.
-Neurotransmitters are released (6) into the synapse (5).
-The neurotransmitters stick to receptor proteins in the neighboring dendrite (7) and trigger an impulse that travels down the dendrite, across the soma, and down another axon.

15. Inactivation of Neurotransmitters The action of neurotransmitters can be stopped by four different mechanisms:
Diffusion – neurotransmitters drifts away out of synaptic cleft
2. Enzyme deactivation – specific enzyme changes structure of neurotransmitter so it is not recognized by receptor
Reuptake is a common way that action of neurotransmitters norepinephrine, dopamine, and serotonin are stopped.

16. Inactivation of Neurotransmitters continued
Glia cells – astrocytes remove neurotransmitters from synaptic cleft
4. Reuptake – whole neurotransmitter molecule is taken back into axon terminal that released it

17. Some of the Better Known Neurotransmitters

18. Acetycholine
Contributes to movement, learning, memory processes, and REM sleep
Only transmitter between motor neurons and voluntary muscles
EXCESS: muscle paralysis or convulsions, sometimes death
DEFICIT: memory impairment (Alzheimer’s disease)

19. Dopamine Used by neurons that control voluntary movements
Also used by neurons that are important for learning, attention, thought & emotion
EXCESS: irrational thought, delusion, and/or hallucinations (Schizophrenia)
DEFICIT: tremors, muscular rigidity, (Parkinson’s disease)

20. Serotonin
Serotonin plays prominent role in regulation of mood, sleep, impulsivity, aggression, and appetite
DEFICIT: related to depression, aggressive behavior

21. Norepinephrine Plays a role in eating, sleep, and mood
DEFICIT: related to depression

22. Gamma-Aminobutyric Acid (GABA)
Appears to have inhibitory effects at synapses
Contributes to regulation of anxiety & levels of activity
ABNORMALITY in GABA may cause epilepsy

23. Endorphins Opiate-like substances produced in the body
Provide relief from pain and produce feelings of pleasure & well-being
Drugs such as opium, morphine, and heroin bind with receptors for endorphins
Endorphins may explain “runner’s high” experienced by long-distance runners

24. Divisions of the Nervous System

25. Central Nervous System – Brain and the Spinal Cord
Integrates incoming pieces of sensory information, evaluates the information, and initiates the outgoing responses
NO potential for regeneration
The CNS - Integrates incoming pieces of sensory information, evaluates the information, and initiates the outgoing responses
NO potential for regeneration

26. Brain
Largest structure of the nervous system and one of the largest organs of the body
12 billion neurons and neuroglia
The adult human brain weighs between 1300 g and 1400 g (approximately 3 lbs). A newborn human brain weighs between 350 and 400 g. For comparison:
elephant brain = 6,000 g chimpanzee brain = 420 g rhesus monkey brain = 95 g beagle dog brain = 72 g cat brain = 30 g rat brain = 2 g
Central Nervous System
Brain: mass of 12 billion neurons and neuroglia weighing approximately 3 pounds, protected by cranial bones

27. Brain Covered by three layers of membranes called meninges Dura mater
Arachnoid
Pia mater
Meninges: 3 membranous coverings with spaces between each
Dura mater: “tough mother”; strong, white, fibrous tissue that lines the skull bones; has inward extensions into the fissures
Epidural space: between the bone and the dura mater
Subdural space: between the dura and arachnoid layers
Arachnoid: resembles fine cobwebs with fluid (CSF) filling the spaces a. Subarachnoid space: between the arachnoid and pia layers
Pia mater: “tender mother”; covers brain and spinal cord surface
CSF: bathes the skull, brain, and spinal cord
Serves as shock absorber for the brain and spinal cord
ml produced daily, yet only 140 ml is circulating at any time
Circulates through the ventricles and into the central canal and subarachnoid spaces and is absorbed back into the blood
Provides nutrients and waste removal for brain tissues
It is clear, colorless, and composed of water, 40-60% glucose, NaCl, K+, protein, and a few white blood cells

28. Structure of the Brain
The three main parts of the brain are the cerebrum, cerebellum and brain stem

29. Cerebrum
Largest mass of brain (83% of brain mass); uppermost and least protective layer of the brain; responsible for higher mental functions and distribution of impulses
Cerebral cortex: outer layer of gray matter; short and long term memory
Cerebral medulla: white matter, conduction pathways
Divided into right and left hemispheres (left side governs right side of body, right side governs left side of body)
Two hemispheres connected by the corpus callosum
Each hemisphere has four lobes
Middle regions of the cerebrum are canals, called ventricles
Cerebrum: largest mass of brain (83% of brain mass); responsible for higher mental functions and distribution of impulses
Cerebral cortex: outer layer of gray matter; short and long term memory
Cerebral medulla: white matter, conduction pathways
Divided into right and left hemispheres (left side governs right side of body, right side governs left side of body)
Cerebellum: below and posterior to cerebrum
Right and left hemispheres connected by central vermis
Outer gray, inner white forms arbor vitae
Coordinates muscular movement, posture, balance, running, walking
Damage produces ataxia (lack of coordination due to errors in speed, force, direction of movement
Brainstem (damage = coma)
Midbrain: upper part of brainstem
Controls postural reflexes and walking
Visual reflexes and auditory control, 3-4 cranial nerves
Pons: a two-way conduction pathway, mixed gray and white fibers
Controls inspiration
Transverse fibers give it a bridge appearance
Reflex mediation for 5-8 cranial nerves
Medulla oblongata: the bulb (lowest part before the foramen magnum) made of white and gray fibers called reticular formation
75% of fibers cross here
Controls vital functions: respiration and circulation
Pyramids: bulges of white tracts on ventral surface
Diencephalon: area between cerebrum and midbrain
Thalamus: gray matter, relay station for sensory incoming and motor outgoing impulses; damage - increased sensitivity to pain, loss of consciousness
Hypothalamus: forms floor of third ventricle
Regulates autonomic control
Cardiovascular control: dilates/constricts
Temperature control
Controls appetite: hunger and thirst
Water balance
GI control: peristalsis, intestinal secretions
Emotional states: fear, anger, pleasure, pain, sexual reflexes
Sleep control
Regulates pituitary secretions
CHO and fat metabolism
Epithalamus: contains the pineal body/gland (melatonin)

30. Right vs. Left Hemisphere
Left side processes:
Speech
Analysis
Time
Sequence
                                 
Right side processes:
Creativity
Patterns
Spatial Awareness
Context
It Recognizes:
Letters
Numbers
Words
Faces
Places
Objects
There are several myths associated with hemispheric dominance. Myths related to:
Handedness - No correlation between hemispheric dominance and being right handed vs. left handed.
Intelligence - No evidence to support right-sided hemispheric dominance is superior to left side hemispheric dominance and vice versa. There is no correlation to intelligence.
Genetics - No evidence that dominance is hereditary.
Gender - Females tend to be more left hemispheric dominant and males tend to be more right hemispheric dominant.

31. Lobes
Frontal: voluntary motor control, learning, planning, L = motor, speech R = non-verbal abilities.
Parietal: sensory, distance, size, shape, cognitive/intellectual processes
Occipital: vision, visual memory
Temporal: auditory, olfactory, speech, judgment, reasoning, will power
There are important asymmetrical differences in the frontal lobes. The left frontal lobe is involved in controlling language related movement, whereas the right frontal lobe plays a role in non-verbal abilities. Some researchers emphasize that this rule is not absolute and that with many people, both lobes are involved in nearly all behavior.

32. Cerebellum
Located in the lower back of the cranium; below and posterior to cerebrum
Coordinates muscular movement, posture, balance, running, walking
Damage produces ataxia (lack of coordination due to errors in speed, force, direction of movement
Pons: a two-way conduction pathway, mixed gray and white fibers
Controls inspiration
Transverse fibers give it a bridge appearance
Reflex mediation for 5-8 cranial nerves
Medulla oblongata: the bulb (lowest part before the foramen magnum) made of white and gray fibers called reticular formation
75% of fibers cross here
Controls vital functions: respiration and circulation
Pyramids: bulges of white tracts on ventral surface
Diencephalon: area between cerebrum and midbrain
Thalamus: gray matter, relay station for sensory incoming and motor outgoing impulses; damage - increased sensitivity to pain, loss of consciousness
Hypothalamus: forms floor of third ventricle
Regulates autonomic control
Cardiovascular control: dilates/constricts
Temperature control
Controls appetite: hunger and thirst
Water balance
GI control: peristalsis, intestinal secretions
Emotional states: fear, anger, pleasure, pain, sexual reflexes
Sleep control
Regulates pituitary secretions
CHO and fat metabolism
Epithalamus: contains the pineal body/gland (melatonin)

33. Brainstem (damage = coma)
Midbrain: upper part of brainstem
* Controls postural reflexes and walking
* Visual reflexes and auditory control, 3-4 cranial nerves
Pons: (literally means “bridge”) a two-way conduction pathway that connect the cerebellum and the cerebrum with the rest of the brain, mixed gray and white fibers
* Controls inspiration
* Transverse fibers give it a bridge appearance
* Reflex mediation for 5-8 cranial nerves
Medulla oblongata: the bulb (lowest part before the foramen magnum) made of white and gray fibers called reticular formation
* 75% of fibers cross here
* Controls vital functions: respiration center, cardiac center, and vasomotor center (constricts or dilates the muscles in the blood vessel’s walls; thus influences BP

34. Diencephalon: area between cerebrum and midbrain
Thalamus: gray matter, relay station for sensory incoming and motor outgoing impulses; damage - increased sensitivity to pain, loss of consciousness
Hypothalamus:
Regulates autonomic control
Cardiovascular control: dilates/constricts
Temperature control
Controls appetite: hunger and thirst
Water balance
GI control: peristalsis, intestinal secretions
Emotional states: fear, anger, pleasure, pain, sexual reflexes
Sleep control
Regulates pituitary secretions
CHO and fat metabolism

35. Spinal Cord
Deep grooves: anterior median fissure (deeper) and posterior median sulcus
2 bundles of nerve fibers called roots project from each side of cord
Dorsal nerve root: sensory afferent fibers
Dorsal root ganglion: sensory cell bodies
Ventral nerve root: motor efferent fibers
The nerve roots join together to form a single mixed nerve called a spinal nerve

36. Peripheral nervous system (PNS)
Made of 12 pairs of cranial nerves and 31 pairs of spinal nerves
Afferent (sensory) division
Carries impulses toward the CNS
Somatic (skin, skeletal muscles, joints)
Visceral (organs within the ventral cavity)
Connecting (associative) neurons
Carry impulses from one neuron to another
Efferent (motor) division
Somatic: carries information from CNS to skeletal muscles (reflex and voluntary control)

37. Functions of the Peripheral Nervous System
Cranial Nerves (12 pairs: “On Old Olympus’ Towering Top, A Finn and German Grew Some Hops”, “Some Say Marry Money But My Brother Says, Bad Business, Marry Money”)
Olfactory: I, sensory, smell
Optic: II, sensory, vision
Oculomotor: III, motor, eye movement and pupil
Trochlear: IV, motor, eye movement, peripheral vision
Trigeminal: V, both, ophthalmic maxillary, mandibular (sensory); face and head (motor)
Abducens: VI, motor, abducts eye
Facial Nerve: VII, both, facial expression, taste, tongue movement
Vestibulocochlear: VIII, sensory, hearing and balance
Glossopharyngeal: IX, both, tongue, throat, swallowing
Vagus: X, both, organ sense (thoracic and abdominal) inhibitor
Accessory: XI, motor, spinal accessory, shoulder and head movement
Hypoglossal: XII, motor, tongue and throat movement

38. Spinal Nerves
31 pairs of mixed nerves attached to spinal cord by ventral and dorsal roots
8 cervical 12 thoracic, 5 lumbar 5 sacral, 1 coccygeal
Each nerve forms several large branches + rami, which subdivide to four complex networks called plexuses (cervical, brachial, lumbar, sacral)
Dermatome: mapping of skin surface of nerve intervention
Spinal Nerves: 31 pairs of mixed nerves attached to spinal cord by ventral and dorsal roots
8 cervical (pass through intervertebral foramina), 12 thoracic, 5 lumbar (exit cord at 1st lumbar vertebra, but do not exit spinal canal until reaching their intervertebral foramina so gives cord a “cauda equina” look), 5 sacral, 1 coccygeal
Each nerve forms several large branches + rami, which subdivide to four complex networks called plexuses (cervical, brachial, lumbar, sacral)
Dermatome: mapping of skin surface of nerve intervention

39. The Autonomic Nervous System
Sympathetic system
The sympathetic nerves are stimulated in situations that require action like the fight-or-flight reaction
Parasympathetic system
The parasympathetic nervous system functions in response to normal everyday situations
Autonomic: includes peripheral nerves and ganglia on either side of the spinal cord; responsible for involuntary, regulates smooth muscles, cardiac muscle, glands
Sympathetic: exit thoracic area of spinal cord and involved in preparing body for “fight or flight”
Parasympathetic: exit cervical and lumbar areas of spinal cord and coordinates the body’s normal resting activities (“resting and digesting-repairing”)