NERVOUS SYSTEM. Introduction Most highly organized system of the body Most highly organized system of the body Fast, complex communication system that.

NERVOUS SYSTEMNERVOUS SYSTEM

IntroductionIntroduction

Most highly organized system of the body Most highly organized system of the body Fast, complex communication system that Fast, complex communication system that

regulates thoughts, emotions, movements, regulates thoughts, emotions, movements, impressions, reasoning, learning, memory, impressions, reasoning, learning, memory, choices choices

Basic Characteristics Basic Characteristics Master control system Master control system

Master communication system Master communication system

Regulates, maintains homeostasis Regulates, maintains homeostasis

MajorMajor StructuresStructures andand DivisionsDivisions

Central nervous system (CNS)Central nervous system (CNS) Peripheral nervous system (PNS)Peripheral nervous system (PNS) Automatic Nervous System Automatic Nervous System

FunctionsFunctions

Monitors change Monitors change (stimuli) - (stimuli) - sensory input sensory input Integrates Integrates impulses - impulses - integration integration Effects Effects responses - responses - motor output motor output

Histology of Nervous TissueHistology of Nervous Tissue

Basic Characteristics Basic Characteristics Highly cellular Highly cellular

2 types of cells - neurons and supporting cells 2 types of cells - neurons and supporting cells (neuroglia)(neuroglia)

Neuroglia CharacteristicsNeuroglia Characteristics

Dense network of supporting cells for nerve tissue Dense network of supporting cells for nerve tissue

Over 900 billion Over 900 billion

CAN replace themselves CAN replace themselves

Also known as glia cells (glia = glue) Also known as glia cells (glia = glue)

Supportive scaffolding; insulation; neuron health Supportive scaffolding; insulation; neuron health and growth (and growth (act as “glue” to support, bind, act as “glue” to support, bind, repair, and protect neurons)repair, and protect neurons)

Neurons: Basic CharacteristicsNeurons: Basic Characteristics

Over 100 billion Over 100 billion Highly specialized Highly specialized Conduct messages in form of nerve impulses Conduct messages in form of nerve impulses Extreme longevity (>100 years) Extreme longevity (>100 years) High metabolic rate High metabolic rate 3 functional components in common: receptive/input 3 functional components in common: receptive/input regions, conducting component/trigger zone, regions, conducting component/trigger zone, secretory/output component secretory/output component Three typesThree types A = afferent (sensory)A = afferent (sensory) C = Connective (associative)C = Connective (associative) E = Efferent (motor)E = Efferent (motor)

Neurons: CharacteristicsNeurons: Characteristics

Excitability: the ability to react to a stimuli, Excitability: the ability to react to a stimuli, physical or chemical physical or chemical

Irritability: sensory adaptation, with prolonged Irritability: sensory adaptation, with prolonged stimulation, irritability is temporarily lost (i.e. stimulation, irritability is temporarily lost (i.e. smell) smell)

Conductivity: the ability to transmit an impulse Conductivity: the ability to transmit an impulse Nonmyelinated fibers = 0.5 - 1 meter /sec (1 mph) Nonmyelinated fibers = 0.5 - 1 meter /sec (1 mph) Myelinated fibers = 80 - 130 meters/sec (300 mph) Myelinated fibers = 80 - 130 meters/sec (300 mph)

The Hand as a NeuronThe Hand as a Neuron

A Closer Look:A Closer Look:Parts of a NeuronParts of a Neuron

nucleus

soma

dendrites

axon

myelin sheath

terminal axon

Myelin SheathMyelin Sheath

Whitish, fatty (protein lipoid) segmented covering Whitish, fatty (protein lipoid) segmented covering of axons of axons

Myelinated fibers: conduct nerve impulses rapidly; Myelinated fibers: conduct nerve impulses rapidly; electrical insulation electrical insulation

Unmyelinated fibers: conduct impulses slowly Unmyelinated fibers: conduct impulses slowly

White matter: myelinated sheaths around axons of White matter: myelinated sheaths around axons of the PNS gives the tissue a white color and forms the PNS gives the tissue a white color and forms myelinated nerves (axons = myelinated tracts) myelinated nerves (axons = myelinated tracts)

Gray matter: concentrations of cell bodies and Gray matter: concentrations of cell bodies and unmyelinated fibers ( in PNS = ganglia; in CNS = unmyelinated fibers ( in PNS = ganglia; in CNS = nuclei) nuclei)

Neurophysiology—Chemical Neurophysiology—Chemical Events At the SynapseEvents At the Synapse

The SynapseThe Synapse

the dynamic region between an axon terminal the dynamic region between an axon terminal and a receiving neuronand a receiving neuron

space between a terminal axon and receiving space between a terminal axon and receiving neuron is called the neuron is called the synaptic cleftsynaptic cleft

synaptic cleft is where electrochemical synaptic cleft is where electrochemical transmission takes place, thus communicationtransmission takes place, thus communication

Impulses from one neuron are transmitted Impulses from one neuron are transmitted across the synapse to another neuron by a across the synapse to another neuron by a chemical called a neurotransmitterchemical called a neurotransmitter

synapse4

Vesicles release Vesicles release NeurotransmittersNeurotransmitters

Inactivation of Inactivation of NeurotransmittersNeurotransmitters

The action of neurotransmitters can be The action of neurotransmitters can be stopped by four different mechanisms:stopped by four different mechanisms:

1.1. Diffusion – neurotransmitters drifts away Diffusion – neurotransmitters drifts away out of synaptic cleft out of synaptic cleft

2. Enzyme deactivation – specific enzyme 2. Enzyme deactivation – specific enzyme changes structure of neurotransmitter so it changes structure of neurotransmitter so it is not recognized by receptoris not recognized by receptor

3. Glia cells – astrocytes remove neurotransmitters from synaptic cleft

4. Reuptake – whole neurotransmitter molecule is taken back into axon terminal that released it

Inactivation of Neurotransmitters continued

Some of the Better Some of the Better Known Known

NeurotransmittersNeurotransmitters

AcetycholineAcetycholine

Contributes to movement, learning, Contributes to movement, learning, memory processes, and REM sleepmemory processes, and REM sleepOnly transmitter between motor Only transmitter between motor neurons and voluntary musclesneurons and voluntary musclesEXCESS: muscle paralysis or EXCESS: muscle paralysis or convulsions, sometimes deathconvulsions, sometimes deathDEFICIT: memory impairment DEFICIT: memory impairment (Alzheimer’s disease)(Alzheimer’s disease)

DopamineDopamine

Used by neurons that control Used by neurons that control voluntary movementsvoluntary movementsAlso used by neurons that are Also used by neurons that are important for learning, attention, important for learning, attention, thought & emotionthought & emotionEXCESS: irrational thought, EXCESS: irrational thought, delusion, and/or hallucinations delusion, and/or hallucinations (Schizophrenia)(Schizophrenia)DEFICIT: tremors, muscular rigidity, DEFICIT: tremors, muscular rigidity, (Parkinson’s disease)(Parkinson’s disease)

SerotoninSerotonin

Serotonin plays prominent role in Serotonin plays prominent role in regulation of mood, sleep, regulation of mood, sleep, impulsivity, aggression, and appetiteimpulsivity, aggression, and appetite

DEFICIT: related to depression, DEFICIT: related to depression, aggressive behavioraggressive behavior

NorepinephrineNorepinephrine

Plays a role in eating, sleep, and Plays a role in eating, sleep, and moodmood

DEFICIT: related toDEFICIT: related to depressiondepression

Gamma-Aminobutyric Acid Gamma-Aminobutyric Acid (GABA)(GABA)

Appears to have inhibitory effects at Appears to have inhibitory effects at synapsessynapses

Contributes to regulation of anxiety Contributes to regulation of anxiety & levels of activity& levels of activity

ABNORMALITY in GABA may cause ABNORMALITY in GABA may cause epilepsyepilepsy

EndorphinsEndorphinsOpiate-like substances produced in the Opiate-like substances produced in the bodybody

Provide relief from pain and produce Provide relief from pain and produce feelings of pleasure & well-beingfeelings of pleasure & well-being

Drugs such as opium, morphine, and Drugs such as opium, morphine, and heroin bind with receptors for endorphinsheroin bind with receptors for endorphins

Endorphins may explain “runner’s high” Endorphins may explain “runner’s high” experienced by long-distance runnersexperienced by long-distance runners

Divisions of the Nervous Divisions of the Nervous SystemSystem

Central Nervous System – Central Nervous System – Brain and the Spinal CordBrain and the Spinal Cord

Integrates incoming pieces of sensory Integrates incoming pieces of sensory information, evaluates the information, information, evaluates the information, and initiates the outgoing responses and initiates the outgoing responses NO potential for regeneration NO potential for regeneration

BrainBrain

Largest structure of the nervous system Largest structure of the nervous system and one of the largest organs of the bodyand one of the largest organs of the body 12 billion neurons and neuroglia12 billion neurons and neuroglia The adult human brain weighs between 1300 g and The adult human brain weighs between 1300 g and

1400 g (approximately 3 lbs). A newborn human brain 1400 g (approximately 3 lbs). A newborn human brain weighs between 350 and 400 g. For comparison: weighs between 350 and 400 g. For comparison:

elephant brain = 6,000 gelephant brain = 6,000 gchimpanzee brain = 420 gchimpanzee brain = 420 grhesus monkey brain = 95 grhesus monkey brain = 95 gbeagle dog brain = 72 g beagle dog brain = 72 g cat brain = 30 gcat brain = 30 grat brain = 2 grat brain = 2 g

BrainBrain

Covered by three Covered by three layers of layers of membranes called membranes called meninges meninges Dura materDura mater ArachnoidArachnoid Pia mater Pia mater

Structure of the BrainStructure of the Brain

CerebrumCerebrum

Largest mass of brain (83% of brain mass); Largest mass of brain (83% of brain mass); uppermost and least protective layer of the brain; uppermost and least protective layer of the brain; responsible for higher mental functions and responsible for higher mental functions and distribution of impulses distribution of impulses

Cerebral cortex: outer layer of gray matter; short and long Cerebral cortex: outer layer of gray matter; short and long term memory term memory

Cerebral medulla: white matter, conduction pathways Cerebral medulla: white matter, conduction pathways

Divided into right and left hemispheres (left side governs Divided into right and left hemispheres (left side governs right side of body, right side governs left side of body)right side of body, right side governs left side of body)

Two hemispheres connected by the corpus callosum Two hemispheres connected by the corpus callosum

Each hemisphere has four lobesEach hemisphere has four lobes

Middle regions of the cerebrum are canals, called ventricles Middle regions of the cerebrum are canals, called ventricles

Right vs. LeftRight vs. Left HemisphereHemisphere

Left side processes:•Speech•Analysis•Time•Sequence

Right side processes:•Creativity •Patterns •Spatial Awareness •Context

It Recognizes:•Letters •Numbers •Words

It Recognizes:•Faces •Places •Objects

Lobes Lobes

Frontal: voluntary motor Frontal: voluntary motor control, learning, planning, L = control, learning, planning, L = motor, speechmotor, speech R = R = non-verbal abilities. non-verbal abilities.

Parietal: sensory, distance, Parietal: sensory, distance, size, shape, size, shape, cognitive/intellectual cognitive/intellectual processes processes

Occipital: vision, visual Occipital: vision, visual memory memory

Temporal: auditory, olfactory, Temporal: auditory, olfactory, speech, judgment, reasoning, speech, judgment, reasoning, will power will power

CerebellumCerebellum

Located in the lower back of the cranium; below Located in the lower back of the cranium; below and posterior to cerebrum and posterior to cerebrum

Coordinates muscular movement, posture, Coordinates muscular movement, posture, balance, running, walking balance, running, walking

Damage produces ataxia (lack of coordination due Damage produces ataxia (lack of coordination due to errors in speed, force, direction of movement to errors in speed, force, direction of movement

Brainstem (damage = comaBrainstem (damage = coma))Midbrain: upper part of brainstem Midbrain: upper part of brainstem

* Controls postural reflexes and walking* Controls postural reflexes and walking* Visual reflexes and auditory control, 3-4 * Visual reflexes and auditory control, 3-4 cranial nerves cranial nerves

Pons: (literally means “bridge”) a two-way Pons: (literally means “bridge”) a two-way conduction pathway that connect the conduction pathway that connect the cerebellum and the cerebrum with the rest of cerebellum and the cerebrum with the rest of the brain, mixed gray and white fibers the brain, mixed gray and white fibers * Controls inspiration* Controls inspiration* Transverse fibers give it a bridge * Transverse fibers give it a bridge appearance appearance * Reflex mediation for 5-8 cranial nerves* Reflex mediation for 5-8 cranial nerves

Medulla oblongata: the bulb (lowest part before Medulla oblongata: the bulb (lowest part before the foramen magnum) made of white and the foramen magnum) made of white and gray fibers called reticular formation gray fibers called reticular formation * 75% of fibers cross here * 75% of fibers cross here * Controls vital functions: respiration center, * Controls vital functions: respiration center, cardiac center, and vasomotor center cardiac center, and vasomotor center (constricts or dilates the muscles in the (constricts or dilates the muscles in the blood vessel’s walls; thus influences BPblood vessel’s walls; thus influences BP

Diencephalon: area between Diencephalon: area between cerebrum and midbraincerebrum and midbrain

Hypothalamus:Hypothalamus: Regulates autonomic Regulates autonomic

control control Cardiovascular control: Cardiovascular control:

dilates/constricts dilates/constricts Temperature control Temperature control Controls appetite: Controls appetite:

hunger and thirst hunger and thirst Water balance Water balance GI control: peristalsis, GI control: peristalsis,

intestinal secretions intestinal secretions Emotional states: fear, Emotional states: fear,

anger, pleasure, painanger, pleasure, pain, , sexual reflexes sexual reflexes

Sleep control Sleep control Regulates pituitary Regulates pituitary

secretions secretions CHO and fat metabolismCHO and fat metabolism

Thalamus: gray matter, Thalamus: gray matter, relay station for sensory relay station for sensory incoming and motor incoming and motor outgoing impulses; outgoing impulses; damage - increased damage - increased sensitivity to pain, loss of sensitivity to pain, loss of consciousnessconsciousness

Spinal CordSpinal Cord

Deep grooves: anterior Deep grooves: anterior median fissure (deeper) and median fissure (deeper) and posterior median sulcus posterior median sulcus 2 bundles of nerve fibers 2 bundles of nerve fibers called roots project from called roots project from each side of cord each side of cord Dorsal nerve root: sensory Dorsal nerve root: sensory

afferent fibers afferent fibers Dorsal root ganglion: Dorsal root ganglion:

sensory cell bodies sensory cell bodies Ventral nerve root: motor Ventral nerve root: motor

efferent fibers efferent fibers The nerve roots join The nerve roots join

together to form a single together to form a single mixed nerve called a spinal mixed nerve called a spinal nerve nerve

Peripheral nervous system Peripheral nervous system (PNS)(PNS)

Made of 12 pairs of cranial nerves and 31 pairs of Made of 12 pairs of cranial nerves and 31 pairs of spinal nerves spinal nerves

Afferent (sensory) division Afferent (sensory) division Carries impulses toward the CNS Carries impulses toward the CNS Somatic (skin, skeletal muscles, joints) Somatic (skin, skeletal muscles, joints) Visceral (organs within the ventral cavity) Visceral (organs within the ventral cavity)

Connecting (associative) neuronsConnecting (associative) neurons Carry impulses from one neuron to anotherCarry impulses from one neuron to another

Efferent (motor) division Efferent (motor) division Somatic: carries information from CNS to skeletal Somatic: carries information from CNS to skeletal

muscles (reflex and voluntary control)muscles (reflex and voluntary control)

Functions of the Functions of the PPeripheral Nervous eripheral Nervous

SystemSystem

Spinal NervesSpinal Nerves

31 pairs of mixed nerves 31 pairs of mixed nerves attached to spinal cord by attached to spinal cord by ventral and dorsal roots ventral and dorsal roots

8 cervical 12 thoracic, 5 lumbar 8 cervical 12 thoracic, 5 lumbar 5 sacral, 1 coccygeal 5 sacral, 1 coccygeal

Each nerve forms several Each nerve forms several large branches + rami, large branches + rami, which subdivide to four which subdivide to four complex networks called complex networks called plexuses (cervical, plexuses (cervical, brachial, lumbar, sacral) brachial, lumbar, sacral) Dermatome: mapping of Dermatome: mapping of skin surface of nerve skin surface of nerve intervention intervention

The Autonomic Nervous The Autonomic Nervous SystemSystem

Sympathetic systemSympathetic system The sympathetic nerves are stimulated The sympathetic nerves are stimulated

in situations that require action like the in situations that require action like the fight-or-flight reaction fight-or-flight reaction

Parasympathetic systemParasympathetic system The parasympathetic nervous system The parasympathetic nervous system

functions in response to normal functions in response to normal everyday situationseveryday situations