anatomy & physiology lecture notes - the nervous system

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Warm-Up 1. Name the 2 main organs of the nervous system. 2. Draw and label the parts of a neuron.

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Page 1: Anatomy & Physiology Lecture Notes - The nervous system

Warm-Up

1. Name the 2 main organs of the nervous system.

2. Draw and label the parts of a neuron.

Page 2: Anatomy & Physiology Lecture Notes - The nervous system

Warm-Up

•Label the parts of the neuron below.

A

B

EF

C

G

D

Page 3: Anatomy & Physiology Lecture Notes - The nervous system

Warm-Up1. One neuron transmits a nerve impulse at 40

m/s. Another conducts at the rate of 1 m/s. Which neuron has a myelinated axon?

2. List the following in order:A. K+ channels open and K+ floods out of cellB. Membrane is polarized (resting potential)C. Neurotransmitters are released from vesicles into

synaptic cleftD. Na+ channels open and Na+ floods into cellE. Stimulus triggers membrane depolarization

3. What restores the resting potential of a neuron?

Page 4: Anatomy & Physiology Lecture Notes - The nervous system

The Nervous System

Page 5: Anatomy & Physiology Lecture Notes - The nervous system

Nervous System

•Master controlling and communicating system

Page 6: Anatomy & Physiology Lecture Notes - The nervous system

Basic Functions1.1. Sensory input Sensory input – gather information2.2. IntegrationIntegration – process and interpret

sensory input3.3. Motor output Motor output – response by muscles and

glands

Page 7: Anatomy & Physiology Lecture Notes - The nervous system

Organization

A.A. Central Nervous System (CNS)Central Nervous System (CNS)▫Brain & spinal cord▫Integrative and control centers

B.B. Peripheral Nervous System (PNS)Peripheral Nervous System (PNS)▫Nerves (spinal nerves, cranial nerves)▫Communication lines between CNS and rest of body▫Two Divisions:Two Divisions:

1.1. Sensory (afferent) DivisionSensory (afferent) Division: Sensory receptors CNS

2.2. Motor (efferent) DivisionMotor (efferent) Division: CNS effectors (muscles & glands)

Page 8: Anatomy & Physiology Lecture Notes - The nervous system

Motor Division

• Somatic nervous systemSomatic nervous system (voluntary) – control skeletal muscles

• Autonomic nervous systemAutonomic nervous system (ANS) (involuntary) – regulate smooth muscles, cardiac, glands▫Subdivisions: sympatheticsympathetic &

parasympatheticparasympathetic

Page 9: Anatomy & Physiology Lecture Notes - The nervous system
Page 10: Anatomy & Physiology Lecture Notes - The nervous system

Nervous TissueNervous Tissue1.1. NeuronsNeurons (nerve cells) - transmit message

Anatomy:▫ Cell bodyCell body – contains nucleus; metabolic center▫ DendriteDendrite – fiber that conveys messages toward

cell body▫ AxonAxon – conduct nerve impulses away from the

cell body▫ Axon terminalsAxon terminals – end of axon; contain

neurotransmitters & release them▫ Synaptic cleft/synapseSynaptic cleft/synapse – gap between neurons

Page 11: Anatomy & Physiology Lecture Notes - The nervous system
Page 12: Anatomy & Physiology Lecture Notes - The nervous system

Nervous TissueNervous Tissue2. Supporting cells (NeurogliaNeuroglia)CNSCNS: : astrocytes, microglia, ependymal cells, astrocytes, microglia, ependymal cells,

oligodendrocytesoligodendrocytes barrier between capillaries and neurons protect neurons immune/defense line brain and spinal cord cavities wrap nerve fibers produces myelin sheaths (covering)

PNSPNS: Schwann cells, satellite cells: Schwann cells, satellite cells surround large neurons protect & cushion

Page 13: Anatomy & Physiology Lecture Notes - The nervous system
Page 14: Anatomy & Physiology Lecture Notes - The nervous system

• MyelinMyelin:: whitish, fatty material that covers nerve fibers to speed up nerve impulses

• Schwann cellsSchwann cells:: surround axons and form myelin sheath

• Myelin sheathMyelin sheath:: tight coil of wrapped membranes• Nodes of RanvierNodes of Ranvier: gaps between Schwann cells

Page 15: Anatomy & Physiology Lecture Notes - The nervous system

• GangliaGanglia: collections of cell bodies• Bundles of nerve fibers = tractstracts (CNS) or

nervesnerves (PNS)• White matterWhite matter: dense collections of myelinated

fibers• Gray matterGray matter: unmyelinated fibers & cell bodies

Page 16: Anatomy & Physiology Lecture Notes - The nervous system

It’s a Mad, Mad, Mad Neuron

Page 17: Anatomy & Physiology Lecture Notes - The nervous system

Classification of Neurons

Page 18: Anatomy & Physiology Lecture Notes - The nervous system

1. Functional Classification: direction nerve impulse is traveling

Sensory neurons

Motor neurons

Interneurons

carry impulses from sensory receptors to

CNS

carry impulses from CNS to muscles &

glands

connect sensory & motor neurons

Vision, hearing, equilibrium, taste, smell,

pain, pressure, heat

Page 19: Anatomy & Physiology Lecture Notes - The nervous system
Page 20: Anatomy & Physiology Lecture Notes - The nervous system

2. Structural Classification: # processes extending from cell body

Multipolar Bipolar Unipolar

1 axon, several dendrites

1 axon, 1 dendrite

1 process

Most common (99%)

RareShort with 2

branches (sensory, CNS)

Eg. Motor neurons,

interneurons

Eg. retina, nose, ear

Eg. PNS ganglia

Page 21: Anatomy & Physiology Lecture Notes - The nervous system
Page 22: Anatomy & Physiology Lecture Notes - The nervous system

Nerve Impulses

Page 23: Anatomy & Physiology Lecture Notes - The nervous system

Neuron Function

1.1. IrritabilityIrritability: ability to respond to stimulus & convert to nerve impulse

2.2. ConductivityConductivity: transmit impulse to other neurons, muscles, or glands

Page 24: Anatomy & Physiology Lecture Notes - The nervous system

Exciting a Neuron:•Cell membrane at rest = polarizedpolarized

▫Na+ outside cell, K+ inside cell▫Inside is (-) compared to outside

•Stimulus excited neuron (Na+ rushes in) becomes depolarizeddepolarized

•Depolarization activates neuron to transmit an action potential action potential (nerve impulse)▫All-or-none response▫Impulse conducts down entire axon

•K+ diffuses out repolarizationrepolarization of membrane

•Na+/K+ ion concentrations restored by sodium-potassium pumpsodium-potassium pump (uses ATP)

Page 25: Anatomy & Physiology Lecture Notes - The nervous system

Resting membrane potential (-70mV)

Page 26: Anatomy & Physiology Lecture Notes - The nervous system

Gated Ion Channels (Na+ and K+)

Page 27: Anatomy & Physiology Lecture Notes - The nervous system

Depolarization

Page 28: Anatomy & Physiology Lecture Notes - The nervous system
Page 29: Anatomy & Physiology Lecture Notes - The nervous system
Page 30: Anatomy & Physiology Lecture Notes - The nervous system

• Saltatory conductionSaltatory conduction: electrical signal jumps from node to node along myelinated axon (30x faster!)

Page 31: Anatomy & Physiology Lecture Notes - The nervous system

Multiple Sclerosis (MS)•Autoimmune disease•Myelin sheaths destroyed reduced to

hardened lesions (scleroses)•Blindness, muscle weakness, speech

disturbance, urinary incontinence•Treatment: interferons, glatiramer (hold

off attacks)

Page 32: Anatomy & Physiology Lecture Notes - The nervous system
Page 33: Anatomy & Physiology Lecture Notes - The nervous system

Nerve Conduction• Action potential

reaches axon terminal vesicles release neurotransmittersneurotransmitters (NT) (NT) into synaptic cleftsynaptic cleft

• NT diffuse across synapse bind to receptors of next neuron

• Transmission of a nerve impulse = electrochemical eventelectrochemical event

Page 34: Anatomy & Physiology Lecture Notes - The nervous system

Neuron Talk

Page 35: Anatomy & Physiology Lecture Notes - The nervous system

Neurotransmitters• 50+ identified• ExcitatoryExcitatory: cause depolarization• InhibitoryInhibitory: reduce ability to cause action

potential• Eg. acetylcholine, serotonin, endorphins

Page 36: Anatomy & Physiology Lecture Notes - The nervous system

Mouse Party

Page 37: Anatomy & Physiology Lecture Notes - The nervous system

NeurotransmittersNeurotransmitt

erNeurotransmitt

erActionAction Affected by:Affected by:

Acetylcholine muscle contraction botulism, curare (paralytic), nicotine

Dopamine “feeling good” cocaine, amphetamines

Serotonin sleep, appetite, nausea, mood, migraines

Prozac, LSD, ecstasy

Endorphins inhibit pain morphine, heroin, methadone

GABA main inhibitory NT alcohol, Valium, barbiturates

Page 38: Anatomy & Physiology Lecture Notes - The nervous system
Page 39: Anatomy & Physiology Lecture Notes - The nervous system

Reflexes

•Rapid, predictable, involuntary responses to stimuli

1.Somatic Reflexes: stimulate skeletal muscles▫ Eg. jerking away hand from hot object

2.Autonomic Reflexes: regulate smooth muscles, heart, glands▫ Eg. salivation, digestion, blood pressure,

sweating

Page 40: Anatomy & Physiology Lecture Notes - The nervous system

Reflex Arc (neural pathway)

Five elements:1. Receptor – reacts to stimulus2. Sensory neuron3. CNS integration center4. Motor neuron5. Effector organ – muscle or gland

Page 41: Anatomy & Physiology Lecture Notes - The nervous system
Page 42: Anatomy & Physiology Lecture Notes - The nervous system
Page 43: Anatomy & Physiology Lecture Notes - The nervous system

Reflex ActivitiesPatellar (Knee-jerk)

ReflexPupillary Reflex

Page 44: Anatomy & Physiology Lecture Notes - The nervous system

Patellar (Knee-jerk) Reflex

Pupillary Reflex

• Stretch reflex• Tapping patellar

ligament causes quadriceps to contract knee extends

• Help maintain muscle tone, posture, & balance

• Optic nerve brain stem muscles constrict pupil

• Useful for checking brain stem function and drug use

Page 45: Anatomy & Physiology Lecture Notes - The nervous system

Flexor (withdrawal) reflex:painful stimulus withdrawal of threatened body part▫Pin prick

Plantar reflex:draw object down sole of foot curling of toes▫Babinski’s sign: check to see

if motor cortex or corticospinal tract is damaged

Page 46: Anatomy & Physiology Lecture Notes - The nervous system

Voluntary Reactions

•More neurons and synapses are involved longer response times

Reflex = Involuntary Reaction Voluntary Reaction