Chapter 12 Flashcards
Ab-
From
Ad-
To, toward
Ante-
Before
Arthro-
Joint
Burs-
Bag, sac
Circum-
Around
Emmetro-
In proper measure
Fil-
Thread
Gran-
Grain
Ipsi-
Itself
Lacun-
Space, hollow
Oligo-
Little, few
Para-
Beyond
Presby-
Old
Sutur-
Sewing
-itis
Inflammation
-malacia
Softening
-opia
Eye
-ostium
Door, opening
What 2 types of cells is nervous tissue composed of?
Neurons & glial cells
Neurons
- Cells that send and receive electrical signals
- Irritable
- Responsive
What are the two divisions of the nervous system?
Central nervous system & peropheral nervous system
What is the central nervous system made up of?
Brain & spinal cord
What is the peripheral nervous system made up of?
Sensory & motor
Afferent-sensory
Carries information from receptors to brain or spinal cord
Efferent motors
Carries info from brain or spinal cord to muscles or glands
What are receptors?
-Neurons and specialized cells that detect changes
- May be in specialized structures such as the tongue, eye, ear
What are the functional divisions of the PNS?
Somatic & autonomic
Somatic
- Controls skeletal muscle contractions
- Voluntary and reflexive
Autonomic
Controls subconscious actions of cardiac and smooth muscles
What are the two autonomic nervous system?
Sympathetic & parasympathetic
Sympathetic
Stimulative
Parasympathetic
Relaxing
Neurons-structure
- Soma
- Dendrites
- Axons
What are the major organelles of neuron?
- Neurolemma
- Nucleus
- Mitochondria
- Smoot and rough ER
- Ribosomes
- Perikaryon - cytoplasm
- Cytoskeleton
Nissl bodies
- Dense areas of RER and ribosomes
Dendrites
Receive information
Axons
- Carry the action potential away from the neuron body
What are the 3 synapse?
- Pre-synaptic cell
- Post-synaptic cell
- Synaptic cleft
Synapse
- Contains synaptic vesicles of neurontransmitters
Neurotransmitters
- are chemical messengers
What are the 4 types of neurons?
- Anaxonic neuron
- Bipolar neuron
- Unipolar neuron
- Multipolar neuron
What are the three functional classifications of neurons?
- Sensory neurons
- Motor neurons
- Interneurons
Sensory neurons
Afferent neurons of PNS
Motor neurons
Efferent neurons of PNS
Interneurons
Association neurons
Three types of sensory receptors
- Interceptors, monitor internal systems, internal senses
What are exteroceptors?
- External sense (touch, temp, pressure)
- Distance senses (sight, smell, hearing)
What are proprioceptors?
- Monitor position and movement (skeletal muscles and joints)
Two groups of efferent axons
- Preganglionic fibers
- Postganglionic fibers
Most located in brain, spinal cord, and autonomic ganglia (between sensory and motor neurons)
Interneurons
Are responsible for
- Distribution of sensory information
- Coordination of motor activity
Interneurons
Are involved in high functions
- Memory, planning, learning
Interneurons
Neuroglia
- Half the volume of the nervous system
- Many types of neuroglia in CNS and PNS
Four types of neuroglia in the CNS
- Ependymal cells
- Astrocytes
- Oligodendrocytes
- Microglia
Ependymal cells
- Form epithelium called ependyma
- Line central canal of spinal cord and ventricles of brain:
secrete cerebrospinal fluid (CSF)
have cilia or microvilli that circulate CSF
monitor CSF
contain stem cells for repair
Astrocytes
- Maintain blood - brain barrier (isolates CNS)
- Create three-dimensional framework for CNS
- Repaid damaged neural tissue
- Guide neuron development
- Control interstitial enviroment
Oligodendrocytes
- Process contact other neuron cell bodies
- Wrap around axons to form myelin sheaths
Microglia
- Migrate through neural tissue
- Clean up cellular debris, waste product, and pathogens
What are the neuroglia of the peripheral nervous system?
- Satellite cells
- Schwann cells
Satellite cells
- Surround ganglia
- Regulate environment around neuron
Schwann cells
- Form myelin sheath around peripheral axons
- One Schwann cells sheaths one segment of axon:
- many Schwann cells sheath entire axon
Neural responses to injuries
Wallerian degeneration
- Axon distal to injury degenerates
Schwann cells
- Form path for new growth
- Wrap new axon in myelin
Transmembrane potential
Ion movements & electrical signals
- all plasma (cell) membranes produce electric signals by ion movements
- transmembrane potential is particularly important to neurons
Three requirements for transmembrane potential
- concentration gradient of ions (Na+, K+)
- selectively permeable through channels
- maintains charge difference across membrane (resting potential - 70 mV)
Passive forces acting across the membrane
Chemical gradients
- concentration gradients of ions (Na+, K+)
Electrical gradients
- separate charges of positive and negative ions
- result in potential difference
Equilibrium
- the transmembrane potential at which there is no net movement of a particular ion across the cell membrane
Examples
K+ = -90 mV
Na+ = +66 mV
Active forces across the membrane
Sodium-potassium ATPase (exchange pump)
- is powered by ATP
- carries 3 Na+ out and 2 K+ in
- balances passive forces of diffusion
- maintains resting potential (-70 mV)
Graded potential
Temporary, localized change in the transmembrane potential produced by a stimulus
Action potential
Electrical impulse produced by a graded potential, propagated down an axon
Chemical gradients
Concentration gradients of ions (Na+, K+)
Electrical gradients
- Separate charges of positive and negative ions
- Result in potential difference
K+
Potassium
Na+
Sodium
Changes in transmembrane potential
Transmembrane potential rises or falls
Another name for passive channels
Leak channels
Another name for active channels
Gated channels
Passive channels?
Are always open
Permeability changes with conditions
Active channels?
Open and close in response to stimuli
At resting potential, most gated channels are
What are the three classes of gated channels?
Chemically gated channels
Voltage-gated channels
Mechanically gated channels
What are chemically gated channels?
Open in presence of specific chemicals
Found on neuron cell body and dendrites
Voltage-gated channels
Respond to changes in transmembrane potential
Have activation gates (open) and inactivation gates (closes)
What is depolarization?
Going more postivie
Repolarization
Going negative
Hyperpolarization
Going even more negative
What are the four steps in generation of action potentials?
Step 1: Depolarization to threshold
Step 2: Activation of Na+ channels
Step 3: Inactivation of Na+ channels, activation of K+ channels
Step 4: Return to normal permeability
What does the refractory period include?
The time period, absolute refractory period, & relative refractory period
What is the time period?
During which membrane will not respond normally to additional stimuli
What is the absolute refractory period?
- Sodium channels open or inactivated
- No action potential possible
What is the relative refractory period?
- Membrane potential almost normal
- Very large stimulus can initiate action potential
What is propagation?
- Moves action potentials generated in axon hillock
- Along entire length of axon
- A series of repeated actions, not passive flow
What are the two methods of propagating action potentials?
- Continuous propagation: unmyelinated axons
- Saltatory propagation: myelinated axons
Saltatory propagation
- Faster and uses less energy than continuous propagation
- Local current “jumps” from node to node
Axon diameter and propagation speed
- the larger the diameter, the lower the resistance
What are the three groups of axons?
Type A fibers
Type B fibers
Type C fibers
What is chemical synapses?
- Signal transmitted across a gap by chemical neurotransmitters
- Synaptic delay
What is electrical synapses?
- Direct physical contact between cells
- Continuous local current and action potential propagation
Gamma
Most common inhibitory neurotransmitter in the CNS
Endorphins & enkephalins
- Inhibit spinal neurons from transmitting pain signals to the brain
What is EPSP?
Excitatory postsynaptic potential
What does EPSP do?
Graded depolarization of postsynaptic membrane
What is IPSP?
Inhibitory postsynaptic potential
Define IPSP
Graded hyperpolarization of postsynaptic membrane
What are the types of axons?
- Axolemme
- Axoplasm
- Axon Hillock
- Telodenria
- Synaptic terminals
What is the synapse?
Area of communication between two cells
What is the synapse?
Area of communication between two cells
