7a Flashcards
Sensory input
Getting info
What do sensory do?
Monitor stimuli in and out of body
Integration
Nervous system processes input and sees if you need to do anything
Motor output
Response or effect that activates muscles or glands
CNS
Central nervous system
Brain and spinal cord
Peripheral nervous system
Cranial and spinal nerves
Afferent
Sense organs
Efferent
Motor
Parts of efferent system
Somatic
Autonomic
Somatic
Voluntary
Skeletal muscle
Autonomic
Involuntary
Cardiac and smooth muscle
Parts of autonomic system
Parasympathetic and sympathetic
Function of CNS
Integration:command center
Interprets info
What is the PNS made of?
Nerves extending from brain and spinal cord
Spinal nerves
Carry messages to and from spine
Cranial nerves
Carry messages to and from brain
Function of PNS
Communicates sense organs, brain, spinal cord and glands or muscles
Sensory (afferent) division
Fibers carry info to CNS
Afferent somatic sensory fibers
Carry info from skin, skeletal muscles & joints
Visceral sensory fibers (afferent)
Carry info from visceral organs
Motor (efferent) division
Nerve fibers carry impulses away from CNS to affector organs
(Muscles and glands)
Neuroglia
support cells in CNS
What do neuroglia do?
Support
Insulate
Protect neurons
Which cells never lose the ability to divide?
Glia aka neuroglia aka glial cells
What do glial cells look like?
Neurons
How are glial cells different from neurons
Never lose ability to divide
Can’t conduct nerve impulses
Types of nervous tissue cells
1.Glia
2. Neurons
Astrocytes
1.Type of glial
2.Star shaped
3.Anchor neurons to capillaries
- Controls permeability, exchanges blood
- Protects from harmful chemicals
- Controls chemical environment
Most abundant glial cells
Astrocytes
Microglia
- Spidery phagocytes
- Check health of neurons
- Get rid of debris
Ependymal cells
1.Line cavities
2. Cilia help move cerebrospinal fluid
3. Found in ventricles
Oligodendrocytes
1.Make myelin sheath
2.wrap around nerve fibers
3. Insulates axons
Oligodendrocytes part of
CNS
Ependymal cells part of
CNS
Microglia part of
CNS
Astrocytes part of
CNS
Schwann cells part of
PNS
Satellite cells part of
PNS
Schwann cells
Make myelin sheath in PNS nerve fibers
Satellite cells
Protect and cushion neuron cell bodies
Neurons
Specialized cells to transmit messages
Regions on neurons
Cell body
Processes
Cell body of neurons
Nucleus and metabolic center of cell
Processes of neurons
Fibers that extend from cell body
Characteristic of neuron cell body
1.Nucleus w/ large nucleolus
2.Nissl Bodies
- Neurofibrils
Nissl bodies
Special rough ER
Neurofibrils
Keep cell shape intermediate filaments
Types of processes
1.Dendrites
2.Axons
3. Synapse
Dendrites
Messages toward cell body (bring messages)
One neuron may have hundreds
Axons
Take messages away
How many axons do neurons have?
One
Where is axon located?
At axon hillock
Where do axons end?
At axon terminals
What do axon terminals contain?
Vesicles w/ neurotransmitters
What separates axon terminals?
Gap
Synaptic cleft
Gap between axon terminals and next neuron
Synapse
Functional junction between nerves where nerve impulse is transmitted
Myelin
White fatty material
Covers axons
Protects, insulates and speeds transmission
Wrap axons in jelly roll fashion (PNS) to form myelin sheath
Schwann cells
Neurilemma
Part of Schwann cell outside of myelin sheath
Nodes of Ranvier
Gaps in myelin sheath along axon
Produce myelin sheath around axons of CNS
Oligodendrocytes
Which myelin sheath cells lack a neurilemma?
Oligodendrocytes
Nuclei
Clusters of cell bodies in CNS
Ganglia
Collections of cell bodies outside of CNS in the PNS
Tracts
Bundles of nerve fibers in the CNS
Nerves
Bundles of nerve fibers in the PNS
White matter
Collections of myelinated fibers (tracts)
Gray matter
Mostly unmyelinated fibers and cell bodies
Sensory afferent neurons
Take info from sense receptors to CNS
Afferent receptors include
1.Cutaneous sense organs
2.Proprioceptors (muscles, tendons)
Proprioceptors
Send info about position & movement of tendons and muscles to CNS
Free nerve endings
Pain and temp receptors in skin
Meissner’s corpuscles
Touch receptors
Lamellar corpuscles
Deep pressure receptors
Golgi tendon organ
Proprioceptor
Get stimuli from within body
Respond to position and movement
Muscle spindle
Proprioceptor
Get stimuli from within body
Respond to position and movement
Motor neurons (efferent)
Take orders from CNS to viscera, muscles, glands
Interneurons aka
Association neurons
Interneurons
Connect sensory and motor neurons
Cell bodies in the CNS
Reflexes
Multipolar neurons
Many extensions
Most common structural type
Motor and interneurons are all
Multipolar
Bipolar neurons
One axon
One dendrite
Where are bipolar neurons located?
Special sense organs
(Nose, eye)
Rare in adults
Unipolar neurons
Short, single process
Where are unipolar neurons found?
PNS ganglia
What do unipolar neurons do?
Conduct impulses toward and away from the body
Irritability
Respond to stimulus and turn into impulse
Conductivity
Ability to transmit impulse to other neurons ,
Muscles or glands
Electric condition of resting neuron membrane
Polarized
Membrane mostly impermaneable to Na+ and K+
Polarized
Inactive
In a resting neuron membrane, ion distribution
Less positive ions inside than outside
Major positive ion inside the cell
K+
Major positive ion outside the cell
Na+
When does the cell remain inactive?
When inside of membrane is more negative (less positive ions) than outside
What changes permeability of neuron’s membrane to Na ions ?
A stimulus
Step 2 of action potential and generation
Na channels open and Na+ enters neuron
Step 1 of action potential and generation
A stimulus changes permeability of membrane
Step 3 of action potential and generation
Influx of Na+ changes polarity
Depolarization
Caused by influx of Na+
No longer inactive
Step 4 of action potential and generation
Localized depolarization exists where inside is more positive than outside
Localized depolarization
Graded potential
Step 5 of action potential and generation
If depolarization is great enough, neuron is activated to conduct impulse
Propagation of the action Potential
If enough Na enters cell, impulse is started and is propagated over the entire axon
All or none response
Impulse is either propagated or not
Fibers with ______ ________ conduct impulses more quickly
Myelin sheaths
How is action potential propagated?
1st membrane patch makes adjacent membrane more permeable.
Repolarization
Opposite of depolarization
What happens during repolarization?
Becomes impermeable to Na and permeable to K
K+ is removed
Inside has - charge, outside has + charge
In which direction does repolarization occur?
Same direction as depolarization
What restores initial conditions of Na and K ?
Na K pump, uses ATP
___ ______ ions are ejected from the cell by the Na K pump
3 sodium
___ _______ ions are returned to the cell by the Na K pump
Two potassium
Neuron can’t conduct another impulse until
Repolarization is complete
Step 1 of transmission of signal at synapses
Action potential reaches the axon terminal,
Electric charge opens calcium channels
Step 2 of transmission of signal at synapses
Calcium kick-starts next part
Makes tiny vesicles containing neurotransmitter chemical to fuse w/ axonal membrane.
Step 3 of transmission of signal at synapses
Release neurotransmitters into synaptic cleft
Step 4 of transmission of signal at synapses
Neurotransmitters in synaptic cleft diffuse and bind to receptors on membrane of next neuron
Neurons not in direct contact, instead form
Synapses
Step 5 of transmission of signal at synapses
If enough neurotransmitter is released, graded potential is generated. Eventually, nerve impulse will occur beyond the synapse
Kick-starts entrance of Na+ into receiving cell
Step 6 of transmission of signal at synapses
Electrical changed during neurotransmitter binding are brief
NT removed from synapse
Ion channels closed, NT broken down and released
What removes NT from synapse ?
Reuptake
Enzymatic activity
Transmission down neuron is
Electrical
Transmission to next neuron is
Chemical
Reflexes
Rapid, predictable, involuntary responses
Reflexes occur over which neural pathways?
Reflex arcs
Types of reflexes
Somatic
Autonomic
5 elements of reflex arc
- Receptor
- Sensory neuron
- Integration center (spinal cord)
- Motor neuron
- Effector
Somatic reflexes
Stim skeletal muscles
Involuntary
Pulling hand away from fire
Autonomic reflexes
- Smooth muscle,
Heart,
Glands. - Regulation of smooth muscle, heart, BP, glands, digestive system
Sensory receptor
Reacts to stim
Sensory neuron
Carries message to integration center
Integration center (CNS)
Processed info and directs motor output
Motor neuron
Carries message to effector
Effector organ
Muscle or gland that’s stimulated
Two neuron reflex arcs
Simplest type
Patellar (knee jerk) reflex
3 neuron reflex arcs
Has all 5 parts of a reflex arc
Flexor: withdrawal (hot surfaces)