Nervous SystemNervous System

FunctionsFunctions

1. Sensory input1. Sensory input

2. Integration2. Integration

3. Homeostasis3. Homeostasis

4. Mental activity4. Mental activity

5. Control of 5. Control of muscles & glands.muscles & glands.

I. Division of the Nervous I. Division of the Nervous SystemSystem

A. Central Nervous A. Central Nervous System (CNS) System (CNS)

1. Brain1. Brain

2. Spinal cord2. Spinal cord

B. Peripheral Nervous B. Peripheral Nervous System( PNS)System( PNS)

1. Nervous that are 1. Nervous that are outside the CNSoutside the CNS

a. Cranial a. Cranial nervesnerves

b. Spinal b. Spinal nervesnerves

2. Sub divisions of the PNS2. Sub divisions of the PNS

a. Sensory (afferent)-conducts action potential from sensory a. Sensory (afferent)-conducts action potential from sensory receptors to the CNS.receptors to the CNS.

b. Motor (efferent) – conducts action potential from CNS to PNS. b. Motor (efferent) – conducts action potential from CNS to PNS. (muscle or glands)(muscle or glands)

a. Somatic - serves sensory nerves, a. Somatic - serves sensory nerves, receptors (skin) receptors (skin) sensory organs (head) & motor sensory organs (head) & motor nerves that stimulate nerves that stimulate the skeletal muscle - the skeletal muscle - voluntary nervous system voluntary nervous system

b. Autonomic - automaticb. Autonomic - automatic1. Sympathetic - involving 1. Sympathetic - involving stressful stressful

activitiesactivities2. Parasympathetic - normal 2. Parasympathetic - normal functioningfunctioning

II. Nerve TissueII. Nerve Tissue

A. Neuroglia - support & maintain A. Neuroglia - support & maintain neuronsneurons

1. Schwann Cells - Provide 1. Schwann Cells - Provide insulation covering around insulation covering around large axons.large axons.

2. Astrocytes - Anchor 2. Astrocytes - Anchor neurons neurons to blood capillaries.to blood capillaries.

3. Ependymal cells - form 3. Ependymal cells - form & & circulate cerebrospinal circulate cerebrospinal fluid.fluid.

4. Microglia - phagocytize 4. Microglia - phagocytize invading microorganisms.invading microorganisms.

5. Oligodendrocytes - 5. Oligodendrocytes - insulation insulation covering around the covering around the CNSCNS..

B. Neurons - functional unit of the nervous B. Neurons - functional unit of the nervous systemsystem

1. Structure1. Structurea. Dendrites - receive a. Dendrites - receive impulsesimpulses

b. Cell body - typical to b. Cell body - typical to other other

cellscells

1. Nissl bodies - 1. Nissl bodies - similar similar to RERto RER

2. Neurofibrils - 2. Neurofibrils - network of fine network of fine threadsthreads

c. Axon (nerve fiber) - carries impulse c. Axon (nerve fiber) - carries impulse away from the cell away from the cell

body.body.

1. One axon to every neuron1. One axon to every neuron

2. Collaterals – side branches2. Collaterals – side branches

3. Axon hillock – site of the 3. Axon hillock – site of the axon axon missing Nissl bodiesmissing Nissl bodies

d. Myelin sheath - d. Myelin sheath - insulating barrier from a insulating barrier from a schwann cell around a schwann cell around a axon.axon.

1. Nourishment1. Nourishment

e. Neurilemma - cytoplasm e. Neurilemma - cytoplasm & nuclei of the schwann & nuclei of the schwann cell on the outer covering.cell on the outer covering.

f. Nodes of Ranvier - gaps f. Nodes of Ranvier - gaps where myelin sheaths are where myelin sheaths are absent.absent.

g. Unmyelinated fibers - g. Unmyelinated fibers - gray mattergray matter

h. Myelinated fibers - white h. Myelinated fibers - white mattermatter

2. Types of Neurons2. Types of Neurons

a. Mutlipolar - many dendrites (signal to a. Mutlipolar - many dendrites (signal to muscles).muscles).

b. Bipolar 1 dendrtie & axon (eyes, ears, & nose).b. Bipolar 1 dendrtie & axon (eyes, ears, & nose).

c. Unipolar c. Unipolar

d. Sensory (afferent) to CNS.d. Sensory (afferent) to CNS.

e. Association (interneurons) with in the CNS.e. Association (interneurons) with in the CNS.

f. Motor (efferent) from CNSf. Motor (efferent) from CNS..

3. Function3. Function

a. Resting potential - a. Resting potential - Polarized -70 mvPolarized -70 mv-more sodium ions -more sodium ions

outside outside the neuron than the neuron than inside.inside.

-more potassium ions -more potassium ions inside inside the neuron than outside.the neuron than outside.

-this is maintained by the -this is maintained by the sodium potassium pump.sodium potassium pump.-but overall negative due -but overall negative due

to to the large negative the large negative chloride chloride ions stuck inside.ions stuck inside.

b. Action potential – (excitable) Nerve impulse + 30 b. Action potential – (excitable) Nerve impulse + 30 mvmv

Depolarization – sodium moves into the cellDepolarization – sodium moves into the cell

Repolarization – potassium moves outside the Repolarization – potassium moves outside the cell.cell.

c. Refractory period - c. Refractory period - hyperpolarized hyperpolarized - 80 mv. - 80 mv. Inside is more Inside is more negative .negative .

4. All or None Response4. All or None Response

a. Threshold a. Threshold Stimulus Stimulus - minimum - minimum strength strength that can that can cause an cause an action action potential.potential.

b. Subthreshold - b. Subthreshold - cannot initiate a cannot initiate a response.response.

c. Summation - c. Summation - series series of of subthreshold stimuli subthreshold stimuli

can have a can have a cumulative cumulative effect.effect.

5. Transmission of impulse5. Transmission of impulse

a. Synapsea. Synapseb. Presynapticb. Presynapticc. Postsynapticc. Postsynapticd. Synaptic end bulbd. Synaptic end bulbe. Synaptic vesiclese. Synaptic vesiclesf. Neurotransmitters f. Neurotransmitters

(50 (50 different)different)

6. Excitatory vs. Inhibitory 6. Excitatory vs. Inhibitory transmissionstransmissions

a. Excitatory causes a. Excitatory causes a a action potential action potential (more (more Na allowed to Na allowed to enter the enter the postsynaptic)postsynaptic)

b. Inhibitoryb. Inhibitory

III. The Central Nervous III. The Central Nervous SystemSystem

A. Spinal Cord - A. Spinal Cord - Conduction pathway for Conduction pathway for impulses between the impulses between the brain & the PNS, reflex brain & the PNS, reflex center.center.

Protected by bone, Protected by bone, fluid, membrane.fluid, membrane.

Compose of gray & Compose of gray & white matter.white matter.

Conduction pathway Conduction pathway between the brain & between the brain & nerves.nerves.

Reflex center 42 cm Reflex center 42 cm long.long.

B. Protective coverings - B. Protective coverings - Meninges - membrane Meninges - membrane layers.layers.

1. Dura mater - 1. Dura mater - outermost, thick, & outermost, thick, & tough.tough.

Epidural space - Epidural space - space space filled with filled with fat between fat between the bone & the bone & dura dura matter.matter.

2. Arachnoid - middle 2. Arachnoid - middle layer of collagen fibers.layer of collagen fibers.

Subarachnoid Subarachnoid space space filled filled with with Cerebrospinal Cerebrospinal fluid fluid (CSF) - shocking (CSF) - shocking

absorning & absorning & transporting.transporting.

3. Pia mater - inner 3. Pia mater - inner most, attached to the most, attached to the spinal cord.spinal cord.

C. StructuresC. Structures1. 31 segments each with a pair of 1. 31 segments each with a pair of spinal nerves.spinal nerves.

2. Gray Matter - center of the cord 2. Gray Matter - center of the cord (looks like an H).(looks like an H).

a. Posterior Horns - a. Posterior Horns - terminal endings of terminal endings of sensory sensory neurons.neurons.

b. Lateral Horns - motor b. Lateral Horns - motor neurons of the neurons of the autonomic autonomic nervous nervous system.system.

c. Anterior Horns - motor c. Anterior Horns - motor neurons to skeletal neurons to skeletal muscle.muscle.

3. White Matter - Surrounds the 3. White Matter - Surrounds the gray mattergray matter

a. Anterior Columns - a. Anterior Columns - b. Lateral Columns- b. Lateral Columns- c. Posterior Columns -c. Posterior Columns -

D. Conduction Pathways D. Conduction Pathways

1. Ascending Tracts - sensory info to the brain.1. Ascending Tracts - sensory info to the brain.

2. Descending Tracts - motor info from the brain.2. Descending Tracts - motor info from the brain.

neurons to the effectors.neurons to the effectors.

E. Spinal nervesE. Spinal nerves

1. Mixed nerves because they contain both sensory 1. Mixed nerves because they contain both sensory and motor neurons.and motor neurons.

2. Organizied into regions that they emerge.2. Organizied into regions that they emerge.C – cervicalC – cervicalT – thoracicT – thoracic L – LumbarL – LumbarS – SacralS – SacralCo – CoccygealCo – Coccygeal

3. Plexus – nerves come together and separate.3. Plexus – nerves come together and separate.a. three main onesa. three main ones

cervical c1-c4cervical c1-c4brachial – c5-t1brachial – c5-t1lumbosacral – l1-s4lumbosacral – l1-s4

E. Reflex CenterE. Reflex Center

1. Reflex is an extremely 1. Reflex is an extremely rapid way of responding to an rapid way of responding to an emergency situation.emergency situation.

a. Receptor at the end a. Receptor at the end of of the sensory neuron.the sensory neuron.

b. Sensory neuron to b. Sensory neuron to the the CNS Associated CNS Associated neuron in neuron in the spinal the spinal cord (reflex cord (reflex center).center).

c. Motorc. Motor

2. Types of reflexes2. Types of reflexesa. Somatic - actions involve a. Somatic - actions involve skeletal muscles.skeletal muscles.

1. Withdrawal – 1. Withdrawal – protectiveprotective

2. Pattellar - knee 2. Pattellar - knee jerk (2 jerk (2 neurons, sensory to neurons, sensory to the the motor)motor)

3. Stretch reflex3. Stretch reflex

b. Visceral - smooth & b. Visceral - smooth & cardiac to cardiac to

maintain maintain homeostasis.homeostasis.

1. 1. Breathing, Breathing, vomiting, vomiting,

sneezing, & sneezing, &

coughingcoughing

IV Brain - integrative center of the IV Brain - integrative center of the nervous systemnervous system

100 billion neurons.100 billion neurons.One of the largest internal organs.One of the largest internal organs.

A. Protective coverings - A. Protective coverings - Meninges - membrane layers.Meninges - membrane layers.

1. Dura mater - outermost, 1. Dura mater - outermost, thick, & tough.thick, & tough.

Epidural space - space Epidural space - space filled filled with fat between the bone with fat between the bone & & dura matter.dura matter.

2. Arachnoid - middle 2. Arachnoid - middle layer of layer of collagen fibers.collagen fibers.

Subarachnoid space filled Subarachnoid space filled with with Cerebrospinal fluid Cerebrospinal fluid

(CSF) (CSF) - - shocking shocking absorbing & absorbing & transporting.transporting.

3. Pia mater - inner most, 3. Pia mater - inner most, attached to the spinal attached to the spinal

cordcord

B. Cerebrum “higher brain”- Largest B. Cerebrum “higher brain”- Largest structure in the brainstructure in the brain

1. Cerebral hemispheres1. Cerebral hemispheres

2. Convolutions2. ConvolutionsGyri - upwards foldsGyri - upwards foldsSulci - inward foldsSulci - inward folds

3. Fissures3. FissuresLongitudinalLongitudinalTransverseTransverse

4. Four lobes4. Four lobesa. Frontal – smell, a. Frontal – smell,

motivation, aggression, motivation, aggression, mood.mood.b. Parietal – touch, pain, b. Parietal – touch, pain,

temperature, balance, tastetemperature, balance, tastec. Occipital – sightc. Occipital – sightd. Temporal – smell, d. Temporal – smell, hearing, hearing,

memorymemory

5. Sensory Functions5. Sensory Functions

a. small portion of the sensory input a. small portion of the sensory input results in sensation.results in sensation.

b. ascending tracts – sends signals to b. ascending tracts – sends signals to the brain.the brain.

-each tract is limited ex…-each tract is limited ex…

ex. ex. Lateral spinothalamic Lateral spinothalamic tracttract

pain & temperature.pain & temperature.

ex. ex. Dorsal columnDorsal column

touch, position, touch, position, pressurepressure

-most tracts have 2 or 3 -most tracts have 2 or 3 neurons to the neurons to the

brain.brain.

-almost all end in the -almost all end in the thalamus.thalamus.

C. Diencephalon – between brain stem & cerebrumC. Diencephalon – between brain stem & cerebrum1. Thalamus - relay station for sensory impulses 1. Thalamus - relay station for sensory impulses

(except (except smell) smell) entering the brain.entering the brain.2. Epithalamus – pineal body (puberty)2. Epithalamus – pineal body (puberty)2. Hypothalamus - Primary control for the autonomic 2. Hypothalamus - Primary control for the autonomic nervous system (homeostasis).nervous system (homeostasis).

a. Thermostat control for body a. Thermostat control for body temptemp

b. regulates food & water uptakeb. regulates food & water uptakec. maintain walking & sleeping patterns.c. maintain walking & sleeping patterns.d. associated with emotion (rage, d. associated with emotion (rage, aggression, sex aggression, sex drivesdrives

1. Pituitary glands - endocrine glands1. Pituitary glands - endocrine glands

D. Midbrain - reflexes for rapid eye, head & trunk D. Midbrain - reflexes for rapid eye, head & trunk movementsmovements

E. Pons - Bridges the cerebrum & cerebellumE. Pons - Bridges the cerebrum & cerebellum

F. Medulla Oblongata - part of the brain stem & most F. Medulla Oblongata - part of the brain stem & most inferior brain structuresinferior brain structures

1. Cardiac & respiratory center1. Cardiac & respiratory center

G. Cerebellum - sends signals to the skeletal musclesG. Cerebellum - sends signals to the skeletal muscles

Cranial NervesCranial Nerves

Cranial NervesCranial Nerves

V. DisordersV. Disorders

A. Encephalitis – inflammation of the brainA. Encephalitis – inflammation of the brain

B. Meningitis – inflammation of the meninges.B. Meningitis – inflammation of the meninges.

C. Rabies – viral disease transmitted by saliva of a animal C. Rabies – viral disease transmitted by saliva of a animal bite.bite.

D. Tetanus – bacterial disease that produces a neurotoxin D. Tetanus – bacterial disease that produces a neurotoxin that affect lower motor neurons in the spinal cord & brain that affect lower motor neurons in the spinal cord & brain stem.stem.

E. MS – autoimmune disorder caused by a viral infectionE. MS – autoimmune disorder caused by a viral infection

F. Cerebral palsy – general, defects in motor functions from F. Cerebral palsy – general, defects in motor functions from several types of brain damage or birth related injury.several types of brain damage or birth related injury.

G. Parkinsons – muscular rigidity, lack of movementG. Parkinsons – muscular rigidity, lack of movement

H. Stroke H. Stroke

I. Alzheimer’s disease – mental deterioration (dementia).I. Alzheimer’s disease – mental deterioration (dementia).

J. Epilepsy – group of brain disorders that cause seizuresJ. Epilepsy – group of brain disorders that cause seizures

K. Herpes - shinglesK. Herpes - shingles

VI. Effects of AgingVI. Effects of Aging

A. Natural decline in functioning neurons, including sensory A. Natural decline in functioning neurons, including sensory neurons.neurons.

(balance loss, coordination, blood pressure, bladder)(balance loss, coordination, blood pressure, bladder)

B. By the age of 60 up to 50% loss of lower motor neurons in lumbar B. By the age of 60 up to 50% loss of lower motor neurons in lumbar region.region.

(loss of muscle mass & increase fatigue)(loss of muscle mass & increase fatigue)

C. Size and weight of the brain decreases, but other neurons can C. Size and weight of the brain decreases, but other neurons can compensate for this loss.compensate for this loss.

D. Short term (problem solving, thinking) memory decreases slowly D. Short term (problem solving, thinking) memory decreases slowly until the age of 60. Afterwards increase rate of memory loss, until the age of 60. Afterwards increase rate of memory loss, especially after 70.especially after 70.

E. Long term memory seems to be unaffected.E. Long term memory seems to be unaffected.

F. More time to fall asleep, more walking periods during the night, F. More time to fall asleep, more walking periods during the night, and longer amount of time being awake at night.and longer amount of time being awake at night.

G. Many older people shoe no change and some show a 10% G. Many older people shoe no change and some show a 10% increase in thinking ability due to education, health, motivation.increase in thinking ability due to education, health, motivation.