nervous system physiology pt 1 Flashcards
What is the function of the nervous system?
- Detects changes, makes decisions, stimulates muscles and glands to respond and maintains homeostasis
What 2 types of cells do neural tissue contain?
- Neurons
- Neuroglia
What is the function of neurons?
- reacts to changes
- send nerve impulses for communication
What is the function of neuroglia?
- surround and support neurons
- nourishes neurons
- help maintain blood-brain barrier
What is the division of the nervous system?
- Central nervous system (CNS)
- Peripheral nervous system (PNS)
What is the CNS?
- brain
- spinal cord
What is the PNS?
- connects CNS to other body parts
- cranial nerves
- spinal nerves
How is the nervous system functionally divided?
- sensory function
- integrative function
- motor function
What is sensory function?
- nervous system receives info
- sensory receptors gather info by detecting changes
- info is carried to the CNS
What is integrative function?
- nervous system coordinates sensory info to create sensations memory, thoughts
- nervous system makes decisions on body’s response to sensory info
What is motor function?
- decisions are acted upon
- impulses are carried to effectors (muscles or glands)
- divisions of motor portion of PNS
What is the somatic nervous system?
- transmits voluntary instructions to skeletal muscles
What is the autonomic nervous system?
- transmits involuntary instructions from the CNS to smooth muscles, cardiac muscle and glands
What are some features of a neuron’s cell body?
- (soma)
- contains nucleus, cytoplasm, organelles, neurofilaments, chromatophilic subtance (Nisse bodies)
- integrate info that comes into the cell body and determines if a single needs to be communicated to another cell
What are some features of a neuron’s dendrite?
- branched receptive surfaces; a neuron many have many
- receives signals from other cells and sends that info to the cell body
What are some features of an axon?
- transmits impulses and releases neurotransmitters to another neuron or effectors (another neuron, muscle cell or a gland cell)
- A neuron many have only 1 axon
- sends the signal from the cell body to another cell
What are the structures of a neuron’s cell body?
- neurofibrils: fine threads that extend into nerve fiber. Provides support for axon hillock and axon
- Chromatophilic substance/Nissl bodies (RER)
What are the structures of a neuron’s dendrite/ axon
- axon hillock
- collaterals
- axon terminal
- synaptic knob
What are the structures of Schwann cells?
- myelin
- myelin sheath
What are the 3 classifications of neurons by structure?
- multipolar neurons
- bipolar neurons
- unipolar neurons
What is the structure of a multipolar neuron?
- 99% of neurons
- many processes
- most neurons of CNS
What is the structure of a bipolar neuron?
- two processes
- eyes, ears, nose
What is the structure of unipolar neurons?
- one process
- cell bodies are in ganglia
- sensory
What are the classifications of neurons by function?
- sensory
- interneurons
- motor
What is the function of sensory neurons?
- afferent neurons
- carry impulse to CNS
- most are unipolar
- some are bipolar
What is the function of interneurons?
- association neurons
- link neurons
- multipolar
- located in CNS
What is the function of motor neurons?
- multipolar, efferent
- carry impulses away from CNS
- carry impulses to effectors
What are sensory neurons also called?
- afferent
- they’re sending info TO the CNS
What are efferent neurons?
- they’re neurons that send signal OUT out of the CNS
- effectors
What are the general functions of neuroglia?
- provide structural support for neurons
- in embryo, guide neurons into position, may stimulate specialization
- produce growth factors to nourish neurons and remove excess ions and neurotransmitters
- aid in formation of synapses
What are the neuroglia of the CNS?
- astrocytes
- oligodendrocytes
- microglia
- ependyma
What is the general characteristics of astrocytes?
- connected neurons to blood vessels; exchange nutrients and growth factors
- form scar tissue
- aid metabolism of certain substances
- regulate ion concentrations, such as K+
- part of blood brain barrier
What are the general characteristics of oligodendrocytes
- mylinate CNS axons; also provide structural support
What are the general characteristics of microglia?
- phagocytic cell; also provides structural support
What are the general characteristics of ependyma cells?
- line central canal of spinal cord and ventricles of brain, cover choroid plexuses
- help regulate composition of cerebrospinal fluid
- cuboidal or columnar cells; ciliated
What are the 2 neuroglia cells of the PNS?
- satellite cells
- Schwann cells
What are the general characteristics of satellite cells?
- support clusters of neuron cell bodies (ganglia)
What are the general characteristics of Schwann cells?
- produce myelin sheath found on some peripheral axons
- speed up nerve impulse transmission
What is the structure of myelination of axons?
- PNS neuroglia that encase axons in sheath
- Schwann cells wrap tightly around axon in layers composed of myelin, lipoprotein mixture
- coating is called the myelin sheath
- nodes of ranvier: raps in myelin sheath between Schwann cells
- neurilemma: cell membrane of the Schwann cell that contains the cytoplasm and encloses the myelin
What are myelinated axons?
- in the PNS have a series of Schwann cells lined up long the axon, each having a wrapped coating of myelin insulating the axon
What are unmyelinated axons?
- are encased by Schwann cell cytoplasm, but there is no wrapped coating of myelin surround the axons
What is gray matter?
- contains neuron cell bodies, axon terminal and dendrites
What is white matter?
- axons coated with myelin
What is neuron regeneration in the PNS?
- if a peripheral axon is injured, it may regenerate
- Axon separated from cellb body and its myelin sheath will degenerate
- Schwann cells and neurolemma remain
- Remaining Schwann cells provide guiding sheath for growing axon
- If growing axon establishes former connections, function will return; if not, function may be lost
What is neuron regeneration in the CNS?
- CNS axons lack neurilemma to act as guiding sheath
- Oligodendrocytes do not proliferate after injury
- Regeneration is unlikely
What is a neuron?
- a single nerve cell
What is a nerve fiber?
- is the axon of a neuron
What is a nerve?
- a bundle of axons from many neurons
What is the flow of info in the nervous system?
- sensory input flows from sensory receptors to the brain or spinal cord for integrating and process
- followed by motor output to an effectors that elicits a response
What is an axon terminal?
- a specialized ending of an axon.
- Ends as a synaptic knob close to the receptive surface of another cell
- Is separated by a space called the synaptic cleft
Explain how an axon in the peripheral nervous system becomes myelinated
- in the PNS, neuroglia called Schwann cells encase axons of certain peripheral neurons in layers of cell membrane filled with a fatty material called myelin, to form myelin sheaths
- A myelin sheath is an electrical insulator for myelinated axons
What are the specialized masses of nervous tissue that cell bodies of interneurons aggregate?
- nuclei
- Similar to ganglia, but are within the CNS
What is the structure of multipolar neurons?
- cell body with many processes
- One of which is an axon
- The rest are dendrites
- found in brain/spinal cord/ganglia of autonomic nervous system
What is the structure of bipolar neurons?
- Cell body with a process arising from each end, one axon and one dendrite
Location: in specialized parts of the eyes, nose and ears
What is the structure of a unipolar neuron?
- Cell body with a single process that divides into two branches and functions as an axon
Location: found in ganglia
What is the function of astrocytes?
- Provide structural support, formation of scar tissue, transport of substance between blood vessels and neurons, communicate with one another and with neurons, mop up excess ions and neurotransmitters, induce synapse formation
What is the function of oligodendrocytes?
- form myelin sheaths in the brain and spinal cord, produce nerve growth factors
What is the function of microglia?
- provide structural support and phagocytosis (immune protection)
What is the function of ependyma?
- form a porous layer through which substances diffuse between the interstitial fluid of the brain and spinal cord and the cerebrospinal fluid
What is the function of Schwann cells?
- form myelin sheaths, mop up excess ions and neurotransmitters, support neuronal regeneration in PNS
What is the function of satellite cells?
- support ganglia, mop up excess ions and neurotransmitters
