nervous tissue Flashcards
The most complex system in the body, that is formed by a network of many-billion nerve cells (aka neurons) assisted
by many more supporting cells (aka glial cells/ neuroglial cells) forming a very complex system for processing information and generating responses .
Nervous tissue
CNS vs PNS
CNS
- brain and spinal cord
- receive and respond to sensory information
PNS
- all nervous tissue, nerve endings and ganglia
- carries sensory information from receptors located in different organs
- transmit motor commands from spins to muscles and glands
Processing center of the body
Central nervous system
Purpose of Nervous Tissue
- Carry sensory information from sensory organs to brain
- Process sensory information in the brain
- to produce perceptions, memories, decisions and plans - Carry motor information from brain to skeletal muscles
It is the functional units of nervous tissue
Neurons (nerve cell)
- exhibit
irritability (able to react to stimulus)
conductivity (transmit stimulus)
limited cell division - irreplaceable when it dies
- building blocks of nervous system
How many does neurons are our body composed of
Around 100 billion
Briefly explain the main parts of Neuron
- Cell body (perikaryon/ soma)
- Axon
E. Dendrites
*has 1 axon and multiple dendrites
contains the nucleus and most of the cell’s organelles and serves as the synthetic or trophic center for the entire neuron
Cell body
(Perikaryon/ soma)
Nucleus is surrounded by neuroplasm (neuron’s cytoplasm)
- the neuroplasm is basophilic = stain well with basic dye
which is a single long process ending at synapses (gaps) specialized to generate and conduct nerve impulses to other cell
Axon
numerous elongated processes extending from the perikaryon and specialized to receive stimuli from unique sites called synapses
Dendrites
[Many short, branch-like processes that extend from the cell body.]
Granular sturucture made of RER and ribosomes and they help with protein synthesis in neurons
Nissl bodies
*golgi apparatus works with rough ER to synthesize and ship proteins
They are structures that include pigments
Neuronal inclusions
- melanin and iron
- also lipofuscin (aging)
It provides structural support and helps transport substance within the neuron
Cytoskeleton
How does the axon conducts impulses
Away from the cell body and transmit them to the next neurons cell body or dendrites through synapses
Plasma membrane of the axon
Axolemma
- internal contents is axoplasm
Longest axon in the human body
Sciatic nerve
- can exceed 1 meter in length
Classification of neurons according to the structure
- Multipolar neuron
- most common neuron
- 1axon and 2 or more
dendrites - Bipolar neuron
- 1 axon and 1 dendrite - Unipolar neuron
- includes all other sensory neuron - Anaxonic neuron
- no axon, many dendrites
- regulates electrical changes of CNS neurons
Most common neurons in the CNS interverbrates
Unipolar neurons
Are unipolar neurons but appears like bipolar neuron
Pseudopolar
Functional classifications of neurons
- Sensory neurons
- afferent neurons (carry signals to the brain and spinal cord)
- receive stimuli and transmit it to CNS - Motor neurons
- efferent neurons
- transmit impulses form the CNS to effector cells - Interneurons
- association neurons
- convey impulses form from one neuron to another
- found in brain and spinal cord
What are the representative neurons
Purkinje cell
- found in cerebellar cortex
Pyramid cell
-cerebral cortex (part of the cerebrum)
Point of contact and site of transmission of nerve impulse and another cell
Synapse
- Action potential is an electrical signal that travels along axon
- At end of axons (axon terminal),triggers the release of neurotransmitters
3.it crosses the synapse to reach the next neuron
Excitatory synapse vs inhibitory synapse
Excitatory synapse:
- Neurotransmitters opens tiny gates (sodium channels) on the next neurons cell body to let +ve Na ions flow = making it less negative (DEPOLARIZATION)
- if enough +ve charge builds up/ exceeds a certain threshold, the neurons fires its own electrical signal
inhibitory synapse:
- opposite, making the neuron more negative (HYPERPOLARIZATION)
- hard for neuron to reach the threshold needed
* common inhibitory neurotransmitters: GABA, gamma-aminobutyric-acid and glycine
Major components of synapse
Axon terminal
- end of axons
- neurotransmitters are stored in vesicles (contains mitochondria to release it)
Presynaptic membrane
Synaptic cleft
Postsynaptic membrane
Glial cells of the CNS
Also known as Synaptic cells
- glial cells/ neuroglial: provide a variety of support and functions for the neurons [support crew for the brain and spinal cord]
Glial cells composed of:
Astrocytes
Ependymal cells
Microglial cells
Oligodendrocytes
Glial cells of the PNS
Composed of:
Satellite cell
Neurolemmocyte (aka Schwann cells)
Divisions of the Nervous system
Anatomic division:
CNS (brain, spinal cord)
PNS ( nervous tissue in the body)
Functional division:
Somatic nervous system (muscle, skin sense organs)
Autonomic nervous system (regulation of visceral organs)
layer of densely packed neurons about 2 mm thick that forms the surface of the hemispheres of the brain.
Cerebral cortex
it’s 3 layers
I - dendrites and axon of neurons running horizontally
II, IV & VI - tiny granules cells
II &
II & V - large pyramidal cells that are key for sending messages
Cerebral cortex is protected by what
By lining called meninges and bones (skull and brain)
layer of densely packed neurons about 2 mm thick that forms the surface of the hemispheres of the brain.
Cerebellum (little brain)
its layers:
Granule cell layer
Purkinje cell layer
Molecular layer
It consists of large bundles of myelinated and unmyelinated axons arranged into ascending and descending tracts
Spinal cord
Gray matter -
Anterior horn -
Posterior horn -
White matter -
Gray matter - neuron cell bodies
Anterior horn - motor neurons that innervate muscle fibers
Posterior horn - interneurons in both sensory and motor pathways
White matter - nerve fibers
Brain hemispheres and spinal cord covering with three layers of connective tissue membrane that
Meninges
- protect nervous system
- provide mechanical stability - provide a support framework for arteries and veins
- enclosed a space that is filled with CSF
Meninges is composed of
Dura mater
Arachnoid
Lia mater
Collection of axons that carry action potentials from one place to another called nerves in the PNS and tracts within the cells
Peripheral nervous system
Posterior root ganglia
- carry sensory info
- body to CNS
Anterior root ganglion
- carry motor signals
- CNS to muscle internal organs
Clusters of neuron cell bodies called
- in PNS
- in CNS
- ganglia
- nuclei
Clusters of axons that are bundled together with a nerve
Fascicles
Small glial cells, surround the neuronal bodies and regulate the extracellular ionic environment
Satellite cells
Consists of a tight spiral wrapping of the lipid-rich cell membrane of ___ in PNS or ___ in CNS
Myelin sheath
- Schwann cell
- oligodendrocyte
- for insulin and faster nerve conduction
A gap between each pair of Schwannce,Les where the bare axon membrane is exposed to extracellular environment
Node of Ranvier
What are the 2 neurons that ANS goes through
Preganglionic neuron
- with the cell body in the CNS
postganglionic neuron
- with the cell body in a ganglion
2 divisions of the ANS
Parasympathetic division
- ganglia within or near the effector organs maintains normal body homeostasis
- resting and relaxing situations
Sympathetic division
- ganglia close to the CNS
- controlled the bid’s response during emergencies and excitement (fight or flight)
ANS components located in the wall of the digestive tract are sometimes referred to as the enteric nervous syste
Enteric autonomic
