Neural Tissue Flashcards
Nervous system characteristics
- System that coordinates all body systems
- Accomplished by the transmission of signals
- Body part —> central nervous system
- Central Nervous system –> body system
- Electrochemical signaling
What are the 2 communication systems?
- Nervous system
2. Endocrine System
Endocrine system characteristics
- Slower scaled system
- Uses chemicals in the blood stream called hormones
General make up of the nervous system (5)
- Organs
- Connective Tissue
- Blood Vessels
- Neurons
- Neuroglia
2 groups or divisions of the Nervous System
- Central Nervous System
2. Peripheral Nervous System
The brain and the spinal cord
Central Nervous System
The cranial and spinal nerves and ganglia
Peripheral Nervous System
Components of the Central Nervous System (5)
- Brain and Spinal Cord
- Covers by meninges
- Starts as a hollow tube
- Bathed in cerebrospinal fluid
- Integration center
Components of the Peripheral Nervous System (3)
- Consists of all cranial and spinal nerves that contain sensory and motor fibers
- Connects CNS to muscles, glands, and all sensory receptors
- Brings information to and from CNS
2 divisions of the Peripheral Nervous System
- Afferent Division = sensory
2. Efferent Division = motor
2 divisions of the Efferent Division
- Somatic Division
2. Autonomic Division
General function of the Nervous System (5)
- Receptors- detect stimuli
- Sensory- afferent PNS
- Integrative- CNS
- Motor- Efferent PNS
- Effector- Muscle/gland
2 types of Nervous Tissue
- Neurons
2. Neuroglial Cells
- Structural and functional units
- Excitable
- Amitotic
Neurons
- Accessory nerve cells
- Act like connective tissue
Neuroglial Cells
3 Parts of a Neuron
- Soma
- Dendrites
- Axon
What is the Soma
- Cell body
- Mononucleate
The soma consists of… (4)
- Nissl Bodies - ribosomes clusters, give gray color
- Axon Hillock- connects soma to axon
- Perikaryon- Region around the nucleus
- Neurofibrils- Cytoskeleton that extend into dendrites/axons and gives it its shape
Dendrite characteristics (4)
- Respond to neurotransmitters
- Short, branched, unmylelinated
- Specialized for contact with other neurons
- Conducts impulses toward the cell body
Axon characteristics (4)
- only 1 per cell
- Conducts nerve impulses AWAY from the soma
- Can give off collaterals
- Many wrapped in myelin sheath, glial cells wrapped around the axon
Where do axons end?
In synaptic terminals
What do axons produce?
Neurotransmitters
Neurotransmitters may contact these 3 things…
- Another neuron
- Muscle fibers
- Glands
The movement of cellular materials (NOT SIGNALS) through the axon
Axonal Transport
AKA Axoplasmic flow
Away from soma, neurotrasmitters, organelles, and nutrients
Anterograde
Towards soma, degraded materials to be recycled and extracellular substances
Retrograde
-Cytoplasm of the axon
Axoplasma
What does the axoplasma consist of? (2)
- Few organelles
- Cytoskeletal proteins
What is the role of the cytoskeletal proteins? (3)
- Form cytoskeleton
- Maintain shape
- Generate axonal transport
-Plasma membrane of axon
Axolemma
What does the axolemma consist of? (4)
- Collaterals
- Telodendria
- Synaptic terminal
- Synaptic Vesicles
Side branches of axolemma
Collaterals
Terminal Extensions of axolemma
Telodendria
Part of axolemma that contains synaptic vesicles where neuron contacts postsynaptic cell
Synaptic Terminal
Structural classification of neurons (4)
- Anaxonic
- Bipolar
- Unipolar
- Multipolar
- Small neurons
- Axons can not be distinguished from dendrites
- In CNS- especially interneurons that coordinate special senses
Anaxonic
- Several small dentrites converge onto one
- Dendrite and axon separated by soma
- Unmyelinated
- Sensory neurons of special sensory organs
Bipolar
- Several small dendrites converge into one large one
- Dendrite and axon continuous
- Usually myelinated
- Majority of sensory neurons in PNS
Unipolar
- Many dendrites extend from soma
- Long axon
- Myelinated
- Majority of motor neurons in PNS
- Spinal interneurons in CNS
Multipolar
Characteristics of Afferent Neurons (4)
- Have sensory function
- Cell body usually are outside CNS
- Have receptor ends on dendrites or are associated with receptor cells in sense organs
- Carry impulses from peripheral body parts –> brain or spinal cord
Receptors in Afferent neurons… (3)
- Exteroceptors
- Proprioceptors
- Interoceptors
Receptor that does…
- touch
- temperature
- pressure
- light
- chemicals
Exteroceptors
Receptor that…
-monitors muscle and skeletal position
Proprioceptos
Receptor that…
-monitor internal systems (digestion, respiration, and urinary system)
Interoceptors
Neurons that…
- Only in CNS
- Classified based on effects (excitatory, inhibitory)
- Most abundant
- Link 2 or more neurons
Interneurons
Neurons that…
- Have motor function
- Cell body is usually inside CNS
- Carries impulses from the brain or spinal cord to peripheral body parts
Efferent Neurons
The 2 divisions of efferent neurons…
- Somatic
2. Autonomic/Visceral
Type of efferent neurons that controls skeletal muscle
Somatic Neurons
Type of efferent neurons that are in smooth muscle and glands
Autonomic/Visceral
Neuroglial Cells in PNS (2)
- Satellite Cells
2. Schwann Cells
Neuroglial Cells in CNS (4)
- Astrocytes
- Oligodendrocytes
- Ependymal Cells
- Microglia
CNS Neuroglial Cell that…
- Largest and most common
- Star shaped
Astrocytes
Functions of Astrocytes (5)
- Structure and repair
- Metabolism
- Regulate ions and nutrients
- Guide nutrients to targets
- From blood brain barrier
CNS Neuroglial Cell that…
-Like astrocytes but smaller
Oligodendrocytes
Functions of Oligodendrocytes (2)
- Form myelin in CNS
- Sequester debris
CNS Neuroglial Cell that…
- Smallest and least common
- Derived from myeloid cells
Microglia
Functions of Mircoglia (3)
- Help support neurons
- Phagocytosis
- Increase in number during injury or disease
CNS Neuroglial Cell that…
- Columnar/cuboidal
- Microvilli on luminal surface
- Joined by gap junctions
Ependymal
Functions of Ependymal (3)
- Help produce cerebrospinal fluid
- Form porous layer
- Monitor CSF composition
PNS Neuroglial Cell that…
- Associated with soma
- Assist with exchange of nutrients
- Isolates neuron from extraneous stimuli
Satellite
PNS Neuroglial Cell that…
- Produce myelin in PNS
- Encloses axons of longer peripheral nerves
Schwann Cells
Functions of Schwann cells… (3)
- Support neurons
- Prevent contact
- Myelinate large PNS axons
Characteristics of unmyelinated axons… (3)
- Appear gray
- Many axons associate with a single schwann cell
- CNS- no glial cells
Characteristics of Myelinated Axons… (3)
- Appear white
- CNS- Oligodendrocytes myelinate part of several axons
- PNS- Schwann cell myelinates part of one axon
Myelin Structure (3)
- Myelin
- Neurilemma
- Nodes of Ranvier
Part of myelin structure that…
-Plasma membrane of Schwann cell wrapped around an axon
Myelin
Part of myelin structure that…
-Part of the Schwann cell that contains the cytoplasm
Neurilemma
Part of myelin structure that…
-Gaps in myelin sheath
Nodes of Ranvier
Process that starts at week 14 and completed by age 2 or 3 years
Myelination process
Myelin Functions (2)
- Isolate Axons
2. Increase rate of action potential
Regeneration of Nerve fibers in PNS
- Can regenerate a fraction of the axons
- Schwann cells participate in process
- Called Wallerian degeneration
Process of Nerve Fiber Regeneration (9)
- Injury separates axon from the cell body (distal portion of the axon will deteriorate along with myelin sheath
- Macrophages clean up
- Some Schwann cells remain and reproduce
- Get thin basement membrane & layer of CT around Schwann cells
- Forms hollow tube leading to original connection of axon
- Proximal end sprouts
- Sprout may grow into tube
- Remaining Schwann cells produce new myelin around growing axon
- New axon grows 3-4 mm/day
Characteristics of repair in CNS (5)
- More limited
- Degeneration occurs after injury
- Oligodendrocytes do not proliferate
- Proximal end sprouts but has no tube that follows
- Astrocytes produce scar tissue and chemicals blocking regrowth
4 Factors of Nerve Impulse
- Irritability
- Excitability
- Action Potential
- Nerve Impulse
Ability to respond to stimuli
Irritability
Ability to transmit an impulse
Excitability
An electrical impulse changing the permeability of a membrane
Action potential
Action potential moving down an axon
Nerve Impulse
Impulse travels faster when… (2)
- Axon is myelinated
2. Has a larger diameter
Functions of synapse
Control and transmission point
Synapse is the site of communication between… (4)
- Sensory structure and neuron
- Neuron & effector
- 2 neurons
- Any 2 cells with gap junctions
2 types of Synapses
- Electrical
2. Chemical
Characteristics of Electrical Synapse
- Gap functions cause the exchange of charged ions between 2 cells
Example of Electrical Synapse
Intercalated disks in cardiac muscle
Characteristics of Chemical Synapse
-Chemicals are released by one cell and travel to another
Examples of Chemical Synapses (2)
- Neuromuscular Junction
2. Neuron-neuron contact
How chemical synapses work
- Synaptic vesicles house neurotransmitter
- Only exist in the presynaptic cell
- Release neurotransmitter into the synaptic cleft
- Receptors on post-synaptic membrane register the neurotransmitter
- Proliferates AP from one cell to the next
- Communication in one direction only
- Receive impulses from afferent fibers (input)
- Impulses carried away on efferent neurons (output)
- Afferent fibers can branch many times as they enter a pool
Neuronal Pool
Types of Neuronal Pools (5)
- Convergence
- Divergence
- Serial Processing
- Parallel Processing
- Reverberation
Type of Neuronal Pool that…
-One neuron to another in a series
Serial Processing
Type of Neuronal Pool that…
- When impulse leaves a pool it may spread out into several output fibers
- Allows impulse to be amplified
Divergence
Type of Neuronal Pool that…
- Single nerve in pool may receive impulses from 2 or more incoming fibers
- if lead to the same nerve, they are said to converge
- Allows summation o impulses from different sources
Convergence
Type of Neuronal Pool that…
-Processing information from several neurons at once
Parallel Processing
Type of Neuronal Pool that…
-Positive feedback continues activity of circuit
Reverberation
- Process in which one neuron may receive either excitatory & inhibitory stimuli from multiple neurons
- The net effect of all this input results in a net charge and if this charge is positive enough it will result in an AP
Facilitation
The point where an action potential can be produced is…
Threshold
- If a neuron is excited but still below threshold
- No impulse but the nerve is more excitable to next impulse
- This nerve is said to be….
Facilitated
Central Nervous System Structures… (3)
- Nuclei
- Center
- Tracts
Collection of neuron cell bodies
Nuclei
Collection of neuron cell bodies working together
Center
Bundles of axons
Tracts
Peripheral Nervous System structures
- Ganglia
2. Nerves
Collection of cell bodies (PNS)
Ganglia
Bundles of axons (PNS)
Nerves
