Nerve tissue Flashcards
What is nervous tissue and what is its function?
-Main tissue component of NS
-Neural communication within the body via neurons - neurons generate, conduct and recieve info via electrical signals and generate appropriate response signal
What is the CNS composed of and does it contain connective tissue?
-Comprised of brain (encephalon) and spinal cord
-No connective tissue except meninges and walls of large blood vessels
What is the PNS comprised of?
-The branching peripheral cranial and spinal nerves and relay centres (ganglia)
What can the PNS be subdivided into?
-Somatic NS
-Autonomic NS
What is the Somatic NS?
-Under voluntary control
-Transmits signals from brain to end organs e.g skeletal muscle
What is the Autonomic NS
-Controls involuntary functions e.g heart rate blood pressure
-Smooth muscle, cardiac muscle, glands
What are the 2 basic types of cells in nervous tissue?
-Neurons - receive and transmit impulses
-Neuroglia - support, protect and assisr neurons in neural transmission - do not receive or transmit impulses
What are the 3 functional classifications of neurons?
-Sensory neurons
-Motor neurons
-Interneurons
What is the structural classification of neurons?
-Multipolar
-Bipolar
-Pseudounipolar
What are sensory neurons and what do they do?
Originate in sensory receptors
-Conducted via sensory (afferent) neurons to the CNS
-Sensory receptors detect taste, pressure, pain, touch, temp, sight, smell, hearing, body postition
What are motor neurons?
-Originate in the CNS
-Conducted via motor (efferent) neurons from CNS to the peripheral ns, muscle tissue or glands
What are interneurons?
-Form connections between neurons in CNS
What is the basic neuronal structure?
-Cell body
-Multiple dendrites
-Single axon
Note on Cell body/perikaryon/soma
-Contains nucleus and perinuclear cytoplasm
-Large, spherical to ovoid nucleus, centrally located
-RER and polyribosomes (rER+polyribosomes= nissl body)
-single axon and one or more dendrites extend from soma
What are Nissl bodies?
rER + polyribosomes
What is the axon hillock?
Region where axon arises
What is the cell body?
-Main nutritional and metabolic region of the neuron
-Receives signals from other cells and sends them towards the axon
What are dendrites and what are their functions?
-Most neurons have multiple dendrites
-Branching results in synaptic terminals
-Synaptic terminals allow a neuron to receive and integrate multiple impulses
-Dendrites function as the major sites of info input INTO the neuron
-Receives signals coming in from other cells and sends towards axon
What does the axon arise from?
Axon hillock
What is the initial segment?
Portion of axon from origin at axon hillock to the beginning of myelin sheath
What are terminal boutons?
Axons terminate on other neurons, effector organs as small branches ending in swellings called terminal boutons - form a synapse
What is the function of an axon?
-Conducts an action potential from soma
-Axonal transport of materials beztween soma and axon terminals
-Can be myelinated or unmylinated
What does anterograde vs retrograde mean?
Anterograde - from soma to axon terminal
Retrograde - axon terminal to soma
Grey vs white matter
Grey matter - cell bodies and dendrites (group of cell bodies = in CNS nucleus, in PNS ganglion)
White matter - axons
What are bipolar neurons?
-Single dendrite and single axon
-Located in vestibular and cochlear ganglia, olfactory epithelium of nasal cavity
What are unipolar (pseudounipolar) neurons?
-One process which branches into central and peripheral branch
-Originate as bipolar neurons but processes partially fuse during embryonic development
What are multipolar neurons?
-Most common
-Multiple dendrites, single axon
What happens at a chemical synapse?
-Most common
-Presynaptic membrane releases neurotransmitters into synaptic cleft
-Neurotransmitter diffuses across synaptic cleft to gated ion-channel receptors
-Binding results in ion channels opening, allowing passage of ions - reverses membrane potential
What are the different types of synaptic contacts between neurons?
-Axodendritic synapse - between axons and dendrite
-Axosomatic system - between axon and soma
-Axoaxonic synapse - between 2 axons
-Dendrodentritic synapse - between 2 dendrites
What happens if there is a maintenence of hyperpolarisation?
inhibitory
What is the most common neurotransmitter chemical?
Acetylecholine
