LAB 1 Flashcards
what is the function of the nervous system?
- receives sensory information
- integrates the sensory information
- initiates reactive measures
what do the many functions of the nervous system revolve around?
maintenance of homeostasis
what is homeostasis?
the ability of the body to maintain a controlled and stable internal environment by responding to internal and external stimuli
why is maintaining homeostasis important?
the majority of body functions can only occur if conditions such as:
- temp.
- pH
- solute concentrations
are maintained within specific physiological parameters
what are the two structural divisions of the nervous system?
- CNS: central nervous system
- PNS: peripheral nervous system
what constitutes the central nervous system?
- brain
- spinal cord
what constitutes the peripheral nervous system?
- cranial nerves
- spinal nerves
- ganglia
- sensory receptors
what does the central nervous system do?
- processes the information received by sensory receptors of the PNS
- controls actions of all parts of the body
- site of thoughts, emotions, memory
what are neurons?
cells that form the functional portion of the nervous system
- highly specialized for impulse conduction, possess electrical excitability
- responsible for all special attributes associated w/ nervous system (thinking, controlling muscles, regulating glands)
- cannot divide
what are the three classes of neurons based on function?
- sensory neurons
- interneurons
- motor neurons
what are sensory neurons?
afferent neurons that conducts impulse from sensory receptors to the CNS
what are interneurons?
association neurons that integrate information from sensory neurons and passes stimuli to motor neurons
what are motor neurons?
efferent neurons that conducts impulses from the CNS to an effector (muscle or gland)
what are dendrites?
processes found on neurons that receive signals from other neurons and carries them to cell body
- plasma membrane contains receptor sites for binding neurotransmitters from other neurons = dendritic spines
- cytoplasm has Nissl bodies, mitochondria, etc.
what are cell bodies?
main portion of neuron that contains nucleus surrounded by cytoplasm w/ organelles suspended in the cytosol
- has Nissl bodies, mitochondria, and other organelles that allow for protein synthesis
- cytoskeleton has neurofibrils (made from intermediate filaments) and microtubules
what is the axon hillock?
cone-shaped elevation where axon joins to the cell body
what is the axon collateral?
branchpoints along an axon’s length, usually at a right angle to the axon
what is an axon terminal?
processes at the ends of axons where synaptic vesicles undergo exocytosis to release neurotransmitters
what are synaptic end bulbs and varicosities?
bulb-shaped, or swollen bumps found at tips of axon terminals that contain synaptic vesicles with neurotransmitters inside
what are Schwann cells?
neuroglia in PNS that can myelinate one axon or enclose ~20 unmyelinated axons
- participates in axon’s regeneration
what is a myelin sheath?
multilayered lipid+protein covering around axons that:
- decreases capacitance (ability to retain charge) of the axolemma
- insulates axons
- increases speed of nerve impulse conduction
what is the neurolemma?
other, nucleated cytoplasmic layer of Schwann cell
- found only in axons of PNS
- forms regeneration tube that stimulates/guides axonal growth
what are myelin sheath gaps/Nodes of Ranvier?
space along myelinated axons btwn. Schwann cells
What are the three classes of neurons according to their structure?
- multipolar neurons
- bipolar neurons
- pseudounipolar neurons
what are multipolar neurons?
neurons that have several dendrites and one axon
- dominates the CNS
what are bipolar neurons
neurons w/ one dendrite and one axon
- found in retinas, inner ears, nasal epithelium
what are pseudounipolar neurons?
neurons w/ fused axon and dendrite that emerge from cell body as one process
- dendrites of these neurons form many of the sensory receptors of the PNS
what are neuroglia?
cells in nervous tissue that:
- provide structural support for neurons and protects them
- form myelin sheaths around axons
- engulfs microorganisms and cell debris
- forms CSF
- prevents some substances from entering CNS
- can divide
- maintains interstitial fluid of nervous tissue
what are astrocytes?
CNS neuroglia
- star-shaped
- largest, most numerous neuroglia
- Protoplasmic/Fibrous astrocytes
- supports neurons w/ its processes
- forms blood-brain barrier
- regulates growth in embryo
- help maintain appropriate chemical environment
- influences formation of neural synapses
what are oligodendrocytes?
CNS neuroglia
- smaller than astrocytes w/ fewer processes
- forms and maintains myelin sheath around CNS axons
what are microglia?
CNS neuroglia
- small, w/ slender processes
- function as phagocytes
- remove cellular debris
- phagocytize microbes and damaged tissue
what are ependymal cells?
CNS neuroglia
- cuboidal to columnar shaped
- arranged in single layer
- has both microvilli and cilia
- lines brain’s ventricles and spinal cord’s central canal as well as subarachnoid space
- produces CSF
- maintains the blood-cerebrospinal fluid barrier
what are schwann cells?
PNS neuroglia
- can myelinate one axon
- can enclose ~20 unmyelinated axons
- participates in regeneration of axons
what are satellite cells?
PNS neuroglia
- flat, surrounds cell bodies of PNS in ganglia
- provides structural support to the cell bodies
- regulates exchange of materials btwn cell bodies and interstitial fluid around them
what protects the spinal cord?
- bony vertebral column
- meninges
- CSF
what is the length of the spinal cord?
extends from medulla oblongata to L2 vertebrae
what is white matter in SC?
bundles of myelinated axons (ganglia) that make up white matter in SC carry sensory info to the brain and motor info back to the PNS
what is grey matter in SC?
contains cell bodies and axons of interneurons
what are spinal meninges?
three layers of connective tissue that surround the spinal cord, continuous w/ the cranial meninges that enclose the brain
what is the function of the spinal meninges?
- protects and cushions the spinal cord in the vertebral column
what is the dura mater?
- most superficial of the meninges
- composed of dense, irregular CT
- toughest, most protective layer of the meninges
what is the arachnoid mater?
- intermediate layer of the meninges
- composed of collagen and elastin fibres
- weblike structure
what is the pia mater?
- most deep layer of the spinal meninges
- squamous to cuboidal cells w/ interlacing bundles of collagen and elastin fibres
- adheres to the spinal cord
- highly vascular to nourish the tissues of the spinal cord
- has denticulate ligaments
what is the epidural space?
space btwn dura mater and vertebral column
- filled w/ fat + CT