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A&P 1
(2) Nervous Tissue
| Question | Answer |
|---|---|
| what are the 2 locations of nervous tissue | central nervous system (CNS) peripheral nervous system (PNS) |
| what is the central nervous system | brain and spinal cord |
| what is the peripheral nervous system | throughout the body's periphery in the form of nerves that come off the brain and spinal cord along with their ganglia |
| functions of nervous tissue | detect change in body's internal and external environment to relay to the CNS, the CNS interprets information, relays messages out to muscles and glands (effectors) to initiate a response to the stimuli |
| nervous tissue is composed of... | neurons |
| what are neurons | the cells that create nerve impulses to send and receive messages |
| what does the neuron cell membrane generate | a nerve impulse |
| what is a neuron cell body filled with | perikaryon |
| what does the neuron cell body contain | Nissl bodies: an arrangement of rough ER and ribosomes around the nucleus neurofibrils: provide internal support for the neuron, form cytoskeleton, provide intracellular transport of organelles and molecules |
| are neuron cells mitotic | no (at 20 weeks, you have all the neurons) |
| The Axon | forms tracts in the CNS and nerves in the PNS |
| where does the axon attach to the cell body | axon hillock |
| true or false: an impulse is generated at the axon hillock and is carried by the axon away from the cell body | true |
| the axon has a wrapping of... | myelin sheath |
| for axons located in the PNS, the sheath is formed from... | Schwann cells |
| true or false: the Schwann cells wrap themselves around the axon, pushing their nuclei and cytoplasm to the periphery | true |
| what is myelin | empty phospholipid bilayer (from Schwann cell) wrapping cell membrane of the axon |
| the "living" portion of the Schwann cell is outside the myelin is known as... | neurolemma |
| Schwann cell functions | nerve fiber regeneration, myelin acts as insulator that prevents ion flow, helping increase speed of impulse travel |
| the gaps of myelin between adjacent Schwann cells are known as... | nodes of Ranvier |
| true or false: nodes of Ranvier is where "leaping" (saltatory conduction) occurs, and allows the impulse to travel faster | true |
| can oligodendrocytes provide myelin around multiple axons simultaneously | yes |
| true or false: oligodendrocytes die at site of injury | true |
| growth of brain and spinal cord after 5 moths in utero to 20 years is due to the addition of... | myelin (90% of brain mass by 6 years) |
| what are the 3 classifications of neuron processes based on amount of myelin present and the diameter of their axons | A fibers, B fibers, C fibers |
| what fiber has the greatest diameter axon and most myelin giving them the fastest impulse speed (250 mph) | A fibers |
| what do A fibers include | sensory neurons that carry messages from the joints, also some senses from the skin (sharp pain, temperature), and motor neurons that supply impulses to skeletal muscle |
| what size diameter and amount of myelin do B fibers have | intermediate diameter axon and intermediate amount of myelin, slower speed (30 mph) |
| what do B fibers do | help deliver sensory and motor impulses to internal organs |
| which fiber has the smallest diameter and is unmyelinated | C fibers (1-5 mph) |
| true or false: C fibers do not have nodes of Ranvier, but can be supported by Schwann cells | true |
| what do C fibers do | deliver sensory and motor impulses to internal organs, and sensory messages from skin (throbbing pain, touch, itch pressure) |
| termination of axons consists of several terminal branches, each one with a... | terminal knob (axon terminal) at the end |
| each axon terminal houses... | synaptic vessels, which contain neurotransmitter |
| where do terminal knobs release neurotransmitter, and what does it cause | into they synaptic cleft that separates the terminal knob from the next neuron, causes exocytosis of the vesicles and releases the neurotransmitter into the synaptic cleft to stimulate the next neuron |
| how many dendrites can be on one cell | one to many (one on bipolar neurons, many on multipolar neurons) |
| what do dendrites transmit | graded potentials toward the cell body |
| do dendrites have a myelin sheath | no |
| do dendrites have receptors (binding sites) for neurotransmitters | yes |
| what are the 3 classifications of neurons by function | motor (efferent), sensory (afferent), interneurons |
| motor neurons carry impulses... | away from CNS (to supply muscle tissue or glands) |
| sensory neurons carry impulses... | toward the CNS |
| interneurons carry messages... | between sensory and motor neurons, and connect different regions within the spinal cord + brain |
| true or false: interneurons make up 99% of all neurons | true |
| what are the 3 classifications of neurons by number of processes | pseudounipolar (unipolar), bipolar, multipolar |
| pseudounipolar (unipolar) neurons | have one process consisting of an axon that connects to the cell body at 1 point. beginning of axon has receptive endings that start impulse on the axon. only found in invertebrates |
| true or false: pseudounipolar are sensory neurons that carry impulses for the general senses | true |
| what are the general senses | hot, cold, touch, pressure, pain, stretch |
| bipolar neurons | two processes, a single dendrite, and an axon |
| what do bipolar neurons carry impulses for | special senses |
| what are special senses | sight, hearing, smell, taste |
| multipolar neurons | multiple dendrites extending from cell body, along with 1 axon |
| what do multipolar neurons make up | all motor neurons and interneurons found in the CNS (99% of neurons are this type) |
| what do neuroglia cells outnumber neurons to | 20:1 |
| what are neuroglia cells | support cells for the neurons |
| what are the 4 types of neuroglia found in the CNS | microglia, astrocytes, oligodendrocytes, ependymal cells |
| what are microglia | WBCs that phagocytize microbes and clean up cellular debris |
| what are astrocytes | star shaped cells that connect neurons with blood vessels, participate in blood brain barrier, and control the permeability of vessels, and control potassium levels in interstitial spaces |
| what do astrocytes form | scar tissue when neurons are damaged in the CNS |
| which glial cell is the most abundant | astrocytes |
| what are oligodendrocytes | provide myelin in the CNS for neurons that have A or B fibers |
| what is multiple sclerosis | results when oligodendrocytes are attacked by the immune system and are replaced by astrocytes, which then forms scar tissue around neuron processes |
| where are ependymal cells | line canals and cavities of brain and spinal cord |
| what do ependymal cells help produce and move | cerebrospinal fluid |
| what are the 2 types of neuroglia found in the PNS | Schwann cells and satellite cells |
| what are Schwann cells | provide myelin and a neurolemma around axons in the periphery |
| what are satellite cells | wrap cell bodies of neurons found in the PNS |
| what do satellite cells help control | chemical environment of the cell |
Created by:
katiew0