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Which systems control homeostasis?
Endocrine and Nervous
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Nervous system
bodys principle control and integrating system. Endocrine is similar, but less important.
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Sensory
detecting changes inside and outside the body.
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integrative
Interpreting the changes detected by the sensory mechanisms
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Motor
Reacting to the changes through the action of organ systems such as glands and muscles.
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2 major divisions in the breakdown of nervous system?
- Central nervous system (CNS)
- Peripheral nervous system (PNS)
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Central nervous system (CNS) consists of?
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PNS consists of?
- Cranial nerves
- Spinal Nerves
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CNS is divided into?
- Afferent/ascending/sensory-nerve cells that conduct impulses toward the brain.
- Efferent/descending/motor- impulses from the brain to muscles and glands.
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Afferent and efferent system can be subdivided into?
- Somatic Nervous System (SNS)
- Autonomic Nervous System (ANS)
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SNS?
Neurons that conduct impulses to the skeletal muscles only.
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ANS
Nervous tissues that convey impulses from the brain.
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ANS conveys impulses from brain to:
- Smooth Muscles
- Cardiac muscles
- glands
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ANS divided into
- Sympathetic division- increases an organs activity.
- Parasympathetic division- decreases an organs activity.
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Two types of nerve cells
- Neurons
- Neuroglia (glial cells)
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Neurons
cells that conduct nerve impulses.
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Neuroglia
cells that support and protect neurons.
5 main types: Oligodendrocytes, astrocytes, neurolemmocytes, microglia, ependymal cells
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Oligodendrocytes
form a supporting network for the individual neurons.
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Astrocyes
attach to blood vessels forming a blood-brain barrier BBB that prevents harmful substances from reaching the brain.
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Neurolemmocytes (schwann cells)
produce the myelin sheath that surrounds many nerve fibers.
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microglia
engage in phagocytosis
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Ependymal cells
Produce the cerebrospinal fluid of the CNS.
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Parts of the neuron
- Cell body (soma)- contains a well defined, single nucleus within the nucleus of a granular cytoplasm
- Dendrites- pick up and convey nerve impulses to soma.
- Axon- conducts impulses from the neuron to the dendrites of another neuron or an affector organ
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what does the white color of the periferal nerve come from?
Myelin
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Gray matter
Unmyelinated nerves
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What increases the speed of a nerve impulse?
Myelin
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What is comprised of almost exclusively of myelinated nerve fibers?
The PNS
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Incapable of regeneration? (Nerve fibers)
Unmyelinated
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Nodes of Ranvier (neurofibriril nodes)
gaps in the myelin sheath between the schwann cells
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axon terminals
fine filaments that the axon terminates at.
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axon terminals terminate in
synaptic end bulbs
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multiple dendrites and 1 axon?
multipolar neurons
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1 dendrite and 1 axon
bipolar neurons
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1 process extending from the cell body with a central branch (axon) and a peripheral branch (dendrite)
unipolar neurons
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interneurons
- purkinje cell- numerous dendritic fibers
- pyramidal cell- body is shaped like a pyramid
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nerves
bundles of neurons outside the spinal cord
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fiber tracts
neurons inside the CNS
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resting nonconducting neuron
- +charged outside and - charged inside
- Polarized
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What maintains the positive and negative balance of a neuron?
Sodium potassium pump
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outside of resting neuron is positive and inside is negative
- resting membrane potential.
- polarized
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occurs when the inside of the nerve becomes positive and the outside becomes negative
de-polarization
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when the channels close after the impulse has passd and the sodium is pumped back out of the nerve fiber.
re-polarization
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the period of time during which the membrane recovers and cannot initiate another action potential is?
absolute refractory period
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If a stimulus is strong enough to generate action potential it will maintain constant ___ and max ___
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a stronger stimulus will/will not cause a greater impulse?
will not
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continuous conduction
- occurs only in unmyelinated
- slower
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saltatory conduction
- occurs only in myelinated fibers
- slower
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why is saltatory conduction faster? Besides being myelinated.
because it skips the schwann cells and goes from node of ranvier to the next
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fibers with a greater diameter conduct faster/slower?
cold nerve fibers faster/slower?
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Electrical synapse
- impuses pass from 1 cell to another using gap junctions.
- 2 way transmissions
- very rare, found in brain and cardiac muscle.
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Chemical synapse
- Neuron secretes a chemical substance called a neurotransmitter that acts upon receptor sites of the next neuron.
- 1 way direction, very common
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Synaptic vessicles
packeges within the synaptic end bulb of the telodendria. They contain the neurotransmitter substance for conduction of the impulse.
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Space in each synapse?
synaptic cleft
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The synaptic cleft is filled with extracellular fluid and separates the?
synaptic end bulb of a neuron (pre-synaptic neuron) from the next (post synaptic neuron)
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Multiple Sclerosis
scarring develop in the brain and spinal cord
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____competes thith ACh for receptor ites and prevents muscular contractions?
Curare
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Bacteria that inhibits release of ACh to prevent muscle contraction.
Botulism toxin
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inhibit synaptic conduction?
Downer
Barbituites
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Increase synaptic conductions?
Upper
Amphetamines
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Substances are picked up periferally and taken back to the nerve cell body
Axonial transport
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What protects the spinal cord?
- vertebral bones
- vertebral ligaments
- ligamentum flavum
- posterior longitudinal ligament
- Cerebral spinal fluid
- Meninges
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Where is the spinal cord located?
Within the spinal canal of the vertebral column
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dura matter contains?
- Epidural space- between the wall of vertebral canal and dura mater
- subdural space- beneath the dura matter and contains serous fluid
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3 coverings of the meninges
- Dura mater- outer most
- arachnoid mater- middle- contains CSF
- pia mater - innermost- transparent and adheres to the brain/spinal cord
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What are the membraneous extensions of the Pia mater that suspend the spinal cord in the middle of the spinal canal?
Denticulate ligaments
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Removal of CSF is called?
Spinal tap, taken within the arachnoid space in the area of L4
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anesthesias introduced into the epidural space in the area of L2 is called?
Epidural block- used for childbirth.
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Where does the spinal cord begin and end?
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What are the 2 enlargements in the spinal cord and where are they?
- Cervical-C4-T1
- Lumbar-T9-T12
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What is the tapered portion of the spinal cord called?
Conus Medullaris
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what originates at the L2 and ends at the Coccyx?
Filum terminale
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Collection of nerves at the distal part of the spinal cord
cauda equina
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Where are spinal taps performed?
between L4 and L5
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spinal cord is divided into
- anterior median fissure
- posterior median sulcus
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outer portion of spinal cord?
white matter called columns
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inner portion of spinal cord?
Gray matter called horns
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Gray matter is in the shape of?
Butterfly of capitol "H"
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The legs of the H are the?
anterior gray horns, and posterior gray horns
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the middle of the H is
Lateral gray horns
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the crossbar of the H is called the
Gray commisure
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IN the middle of the gray commisure and runs the length of the spinal cord is the
Central canal
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What is the myelinated fiber in the spinal cord called
- columns
- Anterior white
- posterior white
- lateral white
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ascendin/afferent/sensory tracts
conduct sensory info to the brain
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descending/efferent/motor tracts
conduct motor impulses from the brain outward
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Each pair of spinal nerves is connected to the spinal cord by?
Nerve roots
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Dorsal nerver roots
contain sensory nerve fibers only
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Ventral root
contains motor axons only
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Enlarged portion of the dorsal root is called? what does it contain?
- dorsal root ganglion
- unipolar cell bodies of the sensory nerves
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ganglions
collections of unmyelinated nerves that lie outside of the CNS
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Reflex
a quick, involuntary response to a stimulus.
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Reflex Arc
shortest route that can be taken by an impulse from a receptor to an effector.
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Receptor
Dendrite that senses a change in the environment.
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sensory neuron
passes the impulse to the end of the Axon
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integrating center
place where association neurons inhibit, transmit, and reroute the impulse
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Motor neuron
transmits an impulse to an effector organ for a response
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Effector
a muscle or organ of the body that responds to a nerve impulse
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2 basic types of reflexes
monosynaptic and polysynaptic
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stretch reflex AKA___ is often called a ___because
there is ___ synapse(s)
- tendon jerk
- monosynaptic reflex arc
- 1
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the stretch reflex or tendon jerk or monosynaptic reflex arc involves.
The response is generated by
The stretch reflex controls
It enters and exits ___ so it is ___
- sensory and motor neurons only.
- rapidly stretching a tendon or ligament
- muscle length
- on the same side, ipsilateral
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To test the ___ the patellar ligament is tapped with a percussion hammer
The quad responds by
This is monosynaptic/polysynaptic?
- knee jerk reflex
- extending the lower leg
- monosynaptic
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polysynaptic reflex arc involves
3 types:
- sensory, association, and motor neurons
- tendon reflex, flexor reflex, crossed extensor reflex
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tendon reflex is mono/poly?
it operates as a ___ mechanism. its job is_________
It involves what kind of neurons
- polysynaptic
- feedback
- to protect muscles from damage due to excessive tension EX arm wrestling
- motor neurons and inhibitory association neurons
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the tendon reflex is on the ___ side so is ___
its sensors are called ___ are located in the tendons signal ______
- same, ipsilateral
- Golgi tendon organs
- the muscle to relax if too much tension develops
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flexor reflex is poly/mono?
it is a ___ reflex
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How does a flexor reflex work?
A sensory neuron sends pain sensation to association neurons. Some ass.neurons stimulate flexor muscles and others inhibit extensor muscles so you can recoil from the pain.
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When a flexor reflex from a single sensory neuron causes association neurons to be affected at several levels of the spinal cord, the response is called an
intersegmental reflex arc
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what occurs where the impulse crosses to the other side of the spinal cord and involves muscles on the opposite side of the body where both extremities are effected?
crossed extensor reflex
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crossed extensor reflex is an example of ____ (impulse enters one side of SC and leaves the other)
contralateral reflex arc
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superficial reflexes are ___ reflexes
EX:
- withdraw
- pin prick, ab reflex, cremasteric reflex, anal wink
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deep tendon reflexes involve ___ and are used for___
EX:
- tendon stretch, testing the integrity of the reflex arcs
- knee jerk, ankle jerk, Babinski sign
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How many of each
cervical spinal nerves
thoracic
lumbar
sacral
coccygeal
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal
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spinal nerves are mixed bc they contain
sensory and motor neurons
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entire nerve is covered by___
bundles of nerves called__ is covered by __
individual nerve fibers are covered by___
- epineurium
- fascicles, perineurium
- endoneurium
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The part of the spinal cord that leaves the intervertebral foramen and divides into branches is called__
The largest branch is__
The dorsal aspect is __
- rami
- ventral ramus
- dorsal ramus
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Rami networks are called
plexus
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innervates the skin, muscles of the head, neck and upper shoulders and the diaphram
cervical plexus
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innervates most of the arm and many neck and shoulder muscles
brachial plexus
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innervates the ab wall, pelvic area and muscles of the thighs. includes the femoral nerve
lumbar plexus
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innervates the genitalia, butt and most of the lower extremities
sacral plexus
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innervates the external genitalia
pudendal nerve
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What nerve is sometimes blocked during childbirth (saddleblock)
Why are they somethimes used?
- pudendal anesthesia nerve blocks
- much less general than epidural
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largest nerve of the sacral plexus and longest in the body
it is formed from __ and __
- sciatic
- tibial and common peroneal
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what can be caused by damage to the sciatic nerve
foot drop or tabes dorsalis
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all spinal nerves except c1 have sensory innervations in specific segments. these are called___.
They can also help detect
- dermatomes
- which segment of the spinal cord has been damaged
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an acute infection of the periphrial nerves by herpes zoster
chicken pox causes shingles
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spinal cord injuries are usually caused by__ or __
trama or tumors
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spinal cord injuries termed:
- monoplegia- paralysis of 1 extremity
- paraplegia- both legs
- hemiplegia- one side
- quad
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severed peripherial nerves that have myelin sheaths can__ bc_
reattach itself because myelin is capable of limited regenerative growth
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cutting the spinal cord in half results in
loss of all sensations and motor control from the cut distally
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inflammation of the nerves
neuritis
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neuritis of the sciatic nerve is
sciatica
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