Fundamentals of the Nervous System Flashcards
Nervous system:
- Master control and communication system
- Has three overlapping functions:
- Sensory ______ monitor _______ inside and outside the body
- – Change = a _______
- – Gathered information = _______ input
- -_______ and _______ sensory input
- – makes decisions - _______
- Dictates a _______ by activating _______ organs (muscle or glands)
- – Response = _______ output
receptors, changes
- stimulus
- sensory input
Gathers and processes
- decision - integration
Response
effector
motor
What are the most basic divisions of the nervous system?
CNS
PNS
The CNS consists of the ______ and ______ _____.
It is the ________ and _______ centre
The PNS is _______ the CNS
- Consists of ______ extending from the brain and spinal cord
- _______ nerves link all regions of the body to the _____
- _______ are clusters of neuronal _____ _____ outside the CNS
brain and spinal cord
integrating and command
outside
nerves
peripheral, CNS
ganglia, cell bodies in PNS
What are ganglia?
Clusters of neuronal cell bodies outside the CNS
Sensory ______ and motor ______:
Sensory (______) signals picked up by sensory ________.
- Carried by _____ fibres of the PNS to the CNS
Motor (_______) signals are carried away from the _____
- innervate _____ or ______
- — tell them to _______ or ______
Input, output
afferent, receptors
nerve
efferent, CNS
muscles, glands
contract, secrete
Whether sensory input or motor output, efferent and afferent always refer to what?
the CNS
The PNS is divided according to the region they serve:
- _______ body region
- consists of structures _____ to the _____ body cavity
- ________ body region
- consists of viscera ______ the _____ body cavity
Results in 4 main subdivisions of the PNS, which are?
Indicate which are outgoing motor commands, which are incoming sensory and from where they are coming from/where are they going to.
Somatic
- external to ventral body cavity
Visceral
- within the ventral body cavity
Somatic motor - outgoing motor command skeletal muscle - voluntary
visceral motor - outgoing motor commands to smooth muscle and cardiac and glands - involuntary
Somatic sensory - incoming sensory information from the outside
Visceral sensory - incoming sensory info from organs of the ventral body cavity
What are the viscera?
Organs of the ventral body cavity - abdominopelvic and thoracic
– heart, lungs, digestive organs
Draw out the complete nervous system organization.
Include a brief description of each and which organs are involved.
Refer to notes
What does somatic sensory detect?
What are the special somatic senses?
General somatic senses
- touch, pain, vibration, pressure, temperature, proprioceptive senses
Special somatic senses
- hearing
- balance/eqb
- vision
How are propioceptive senses detected?
What is it?
Detect stretch in tendons and muscle. (joints)
body sense - position and movement of body in space
What does visceral sensory detect?
General visceral senses:
- stretch, pain, temperature, nausea and hunger
Special visceral senses:
- taste, smell
Describe both somatic motor and visceral motor.
In your answer provide which is the effector organ, if it is under voluntary control or not and indicate any further subdivisions.
Somatic motor
- effectors are skeletal muscle
- voluntary control
Visceral motor
- effectors are smooth muscle, cardiac muscle, glands and visceral organs
- involuntary
- makes up the ANS
What are the two main cell types of nervous tissue?
Briefly describe them
Neurons - conduct electrical signals
- excitable cells
Neuroglia - support cells
- nonexcitable
- surround and wrap neurons
What is the basic unit of the nervous system?
What are its special characteristics?
Neuron
Special characteristics:
- longevity
- do not divide (exception are neural stem cells)
- high metabolic rate (require lots of oxygen and glucose)
What are the different parts of a typical neurons?
Briefly describe.
For the first, decscribe how it changes between CNS and PNS.
For the second, describe the function and the direction of impulse conduction.
For the third, describe how many a typical neuron has, and the direction of impulse conduction.
Cell body - soma
- contains a single nucleus surrounded by the cytoplasm
- most cell bodies are in the CNS, ganglia are cell body clusters in the PNS
Dendrites
- extensively branching from the cell body, receive signals from other neurons
- increases SA for receiving synaptic communication
- transmit signals toward the cell body
Axons
- neuron has only one
- impulse generator and conductor
- transmit impulses away from the cell body
Describe how the diameter of an axon is important.
Larger diameter axons will conduct impulses faster.
Resistance in an axon decreases as _______ increases.
diameter
What do myelin sheaths effectively do?
Increase speed of conduction
What are the two major classifications of neurons?
Structural - based on the number of processes extending from the cell body.
Functional - based on the direction the nerve impulse travels relative to CNS
What are the subdivisions of the structural neuron classification? Describe.
Structural
- Multipolar: more than two processes; numerous dendrites, one axon, most abundant
- bipolar: two processes; rare, found in special sensory organs
- unipolar - pseudounipolar: one short, single process
- starts off bipolar during development
- majority of sensory neurons
What is the functional neuronal classification subdivided into. Describe each.
Functional: Sensory (afferent) neurons: - impulses toward CNS - virtually all unipolar - cell bodies in ganglia outside PNS - Short single process divides into: -- central process - runs centrally to CNS -- peripheral process - extends peripherally to the receptors
Motor (efferent) neurons:
- carry impulses away from CNS to effector organs
- most are multipolar
- cell bodies within CNS
Interneurons:
- most are multipolar
- lie between motor and sensory neurons
confined to CNS
Neuroglia:
Six types of _______ cells.
- _ in the CNS
- _ in the PNS
Provide ______ for neurons by:
- ______ the neurons
- Keeping the electrical activities of ______ neurons from ________ with each other
supporting
4
2
support
insulating
adjacent
interfering
_________ are glial cells in the CNS.
- they are much _____ than neurons
- they _______ neurons (:)
- make up half the mass of the ______
- Can ______ throughout life
Neuroglia smaller outnumber, 10:1 brain divide
________ are the most abundant glial cell
- maintain close association between _______ and _______
- increase ______ ____ to active regions of the brain
- Take up and release ______ in order to control environment; also carry ______ to the blood
- Regulate _______ levels
- Aid in _______ formation and neuronal _______
- ____-shaped
- Essentially form the _____-______ ______
Astrocytes capillaries and neurons blood flow ions, wastes neurotransmitter synapse, growth star blood-brain barrier
_______ are the smallest and least abundant glial cells
- They are _______, essentially the _______ of the CNS
- Derive from blood cells called _______
- Thus, they do not originate in ______ tissue, instead they originate in the _____ ____
Microglia phagocytic, macrophages monocytes nervous tissue bone marrow
_________ cells line the ______ cavity of the spinal cord and brain
They bear _____ which help circulate the ____
ependymal
central
cilia
CSF
_____ nourishes brain tissue and increases the ________ of the brain.
_____ is a filtrate of the _______ and is constantly refreshed.
_____ _______ - this is what creates the barrier between the blood and CSF within the nervous system
Anything that gets filtered through the blood to the CSF gets processed by _________ cells.
CSF, lightness
CSF, blood
CSF barrier
ependymal
_________ wrap their cell processes around ______ in the ______ to produce _______ _______.
oligodendrocytes
axons
CNS
myelin sheaths
What increases signal conduction?
Myelin sheaths and nodes de Ranvier
What are the two neuroglia in the PNS?
What do they do?
Satellite cells - surround neuron cell bodies within ganglia
Schwann cells - surround axons in the PNS to form myelin sheaths
Where are myelin sheaths produced?
What do they do and what axons have them?
Produced in the CNS by oligodendrocytes.
Produced in the PNS by Schwann cells.
Surround thicker axons
Form an insulating layer to prevent cross-talk and increase the speed of conduction.
Myelin sheaths in the PNS:
- Formed by _______ cells
- develop during the _____ period and in the ______ year
- wrap in ________ layers around the axon
schwann
fetal, first
concentric
What are neurilemma?
material external to myelin layers containing the nucleus and cytoplasm of the cell.
Nodes of Ranvier are _____ along axon (myelinated).
Thick axons are _______ and go to ______ ______.
Thin axons are _______ and conduct impulses more _______.
gaps
myelinated - skeletal muscles
unmyelinated
slowly
__________ form the myelin sheaths in the CNS
- have ________ processes
- coil around _______ ______ axons
oligodendrocytes
multiple
several different
Multiple sclerosis:
- common cause of _______ disability
- an _________ disease
- immune system attacks the _______ around axons in the CNS
- More _______ are affected than _____
- Treatment is designed to relieve the _______ and lessen the ______ and duration of relapses but not reduce the _______ of attacks
neural autoimmune myelin women, men symptoms, severity, duration frequency
Where are the effects of MS normally seen?
effector muscles
Describe how women with MS, when they are pregnant, feel better.
Are immunosuppressed, body has time to heal itself, neuroglial cells can divide and repair.
If attacks too frequent, get scarring and plaque.
What does sclerosis mean?
What is used to identify sclerosis?
Buildup of plaque
MRI
What are nerves?
Cable-like organs in the PNS
- consist of numerous axons wrapped in CT
What is endoneurium?
layer of delicate, loose CT surrounding the axon
What is Perineurium?
CT surrounding a nerve fascicle
- groups of axons bound into bundles = nerve fasciscle
What is epineurium?
Whole nerve is surrounded by tough fibrous sheath.
What are the three layers of nerves?
Endoneurium, perineurium, epineurium
Neuron - _____ cell
Nerve fibre - long _____
Nerve - collection of _____ _____ in the PNS
nerve
axon
nerve fibres
Describe the regeneration of the peripheral nerve fibre.
1 - Axon becomes fragmented at site of injury
2 - macropahges clean out the dead axon distal to injury
3 - axon sprouts or filaments, grow through a regeneration tube formed by Schwann cells
4 - axon regenerates, new myelin sheath formed
Why is the PNS often recoverable after injury, but not the CNS?
PNS has schwann cells
Neuroglia in CNS never form bands to guide regrowth and may hinder axon growth with growth-inhibiting chemicals
What is the current treatment for damaged axons in the CNS?
What are future treatments?
Anti-inflammatory drugs to prevent production of free radicals and cell death
Future:
- neuronal stem cells
- Schwann cell implants
- identifying and blocking chemicals inhibiting axon growth
Nerves of the PNS:
- information pathways to and from the body periphery
- ________ PNS fibres response to sensory stimuli and carry information to the _____
- ________ PNS fibres transmit motor stimuli from ____ to ______ and _______
afferent, CNS
efferent, CNS, muscles, glands
Nerves of the CNS:
- composed of ________ that
- receive and process ______ information
- direct information to specific ______ regions
- transport information from one area of the _____ to another
- initiate appropriate _______ responses
interneurons sensory CNS CNS motor
______ _____ - simple chain of neurons that exhibits the structural link between the CNS and PNS
- responsible for _____
Reflex arcs
reflexes
What are reflexes?
Rapid, automatic motor responses
can be somatic (patellar tendon reflex) and visceral (vomiting)
What are the five essential components of a reflex arc?
Describe each briefly
Receptor - site of stimulus
Sensory neuron - transmit afferent impulse to CNS
integration sensor - one or more synapses in the CNS
motor neuron - conduct efferent impulses to effector
effector - muscle or gland cell
What are the different types of reflexes?
Give an example of each and briefly describe.
Monosynaptic
- simplest
- one synapse
- fastest
ex: knee-jerk reflex
Polysynaptic:
- more common
- most have a single interneuron between the sensory and motor neuron
ex: withdrawal reflex
Why is there a delay in feeling pain for certain reflexes?
Delay due to the time it takes to get information to the cerebral cortex.
Simplified design of the nervous system:
Sensory neurons are located ______
- cell bodies are outside the _____ in sensory ______
- central processes enter ______ aspect of the spinal cord
Motor neurons are located ______
- axons exit the _______ aspect of the spinal cord
Interneurons are located _______.
- confined to _____
- comprise ____ of all neurons
dorsal
CNS
ganglia
dorsal
ventral
ventral
central
CNS
99%
Incoming sensory goes into the spinal cord _______, outgoing motor goes out ______.
Interneurons are ________.
Motor neurons are ______.
Sensory neurons are _______.
dorsally, ventrally
multipolar, multipolar, unipolar
