Chapter 11 - Nervous System and Nervous Tissue Flashcards
Functions of the Nervous System
A. Sensory input – gathered information; it uses its sensory receptors to monitor changes inside and outside body
B. Integration – it processes and interprets input and decides what to do with it
C. Motor output – causes a response by activating effectors muscles or glands
Organization of the Nervous System
A. Central nervous system (CNS) – brain and spinal cord, found in the dorsal cavity; it’s the command center of the nervous system, it receives sensory input and dictates response
B. Peripheral nervous system (PNS) – nervous system outside the CNS, mainly nerves (bundles of axons) that extend from brain and spinal chord
PNS
- Sensory (afferent) division – includes nerve fibers that convey or take impulses to the CNS from sensory receptors that are located throughout the body
a. Visceral (afferent) – transmit fibers from visceral organs (ventral body cavity)
b. Somatic (voluntary) nervous system – skin skeletal muscles and joints - Motor (efferent) division – transmits impulses from the CNS to effecter organs (muscles and glands)
a. Somatic nervous system (voluntary system) – has somatic nerve fibers that conduct impulse from the CNS to skeletal muscle
b. Autonomic (involuntary) nervous system (ANS) – consists of visceral motor nerve fibers and regulates the activity for smooth muscle (digestive tract, cardiac and glands)
i. Sympathetic division – mobilize body systems during actives or under stress (fight or flight)
ii. Parasympathetic division – conserve energy and it promotes actives that occur at rest; rest or digest (salivation, urination, digestion, and defecation)
Cells of Nervous Tissue: Neuroglia of CNS - Astrocytes
Astrocytes – most abundant and versatile glia cell
i. Structure – star shape, they’re connected together by gap junctions and they signal to each other both by taking in calcium and releasing chemical messengers
ii. Function – support and brace neurons and anchor them to their nutrient supply line (capillary); the radiating processes cling to neurons and capillaries, they control the chemical environment around neurons and they mop up leaked potassium ions and neurotransmitters, they influence the neuronal function, and participates in information processing that occurs in the brain
Cells of Nervous Tissue: Neuroglia of CNS - Microglia
i. Structure – small ovoid cells with long thorny processes
ii. Function – monitor neurons health and they behave as macrophages (eat up dead material/ microorganisms)
Cells of Nervous Tissue: Neuroglia of CNS - Ependymal Cells
i. Structure – range from squamous to columnar and many can be ciliated,
ii. Function – line central cavities of brain and spinal cord where they form a permeable barrier between the cerebral spinal fluid (that fills cavities) and tissue fluid that’s bathing in the cells of the CNS
Cells of Nervous Tissue: Neuroglia of CNS - Oligo Dendrocytes
i. Structure – fewer processes than astrocites
ii. Function – produce myline in the CNS
Cells of Nervous Tissue: Neuroglia of PNS - Satellite Cells
i. Location – surrounding cell bodies located in the PNS
ii. Function - support and brace neurons and anchor them to their nutrient supply line (capillary); the radiating processes cling to neurons and capillaries, they control the chemical environment around neurons and they mop up leaked potassium ions and neurotransmitters, they influence the neuronal function, and participates in information processing that occurs in the brain
Cells of Nervous Tissue: Neuroglia of PNS - Satellite Cells
i. Location – surrounding the nerve fibers in the PNS
ii. Function – produce myline in the PNS
Neurons: Characteristics
a. Longevity – good nutrients can function a life time
b. Amitotic – loose ability to divide and cannot be replaced if destroyed
c. Metabolic rate – require high amounts of oxygen and glucose
Neurons: Regions - Cell Body
Cell body – soma, spherical nucleus and conspicuous nucleolus which are surrounded by cytoplasm
i. Function – major biosynthetic center and receptive region of the neuron
ii. Structures
A. Nucleus – contains genetic information
B. Nissl bodies – rough endoplasmic reticulum of a neuron and it produces protein
C. Nueuro Fibers – nuero filaments and they are important in maintaining cell shape and integrity
iii. Classification
A. Nuclei
B. Ganglia
Neurons: Regions - Processes
Processes – extensions from the cell body of neurons
i. Classification
A. Tracts – bundles of neuron processes that are in the CNS
B. Nerves – bundles of neuron processes that are in the PNS
ii. Dendrites – branches
A. Function – main receptive or input regions, they provide an enormous surface area for receiving signals
B. Structures – short tapering diffusely branching extensions
iii. Axon
Neurons: Regions - Processes - Axon
A. Function – long arm of the neuron – aka nerve fiber
B. Structures – conducting region that generates and transmits nerve impulses
1. Axon hillock – cone shaped initial region of the axon where action potentials start
2. Schwann cells – produces myline
a. Myelin sheath – whiteist fatty segmented nerve fiber covering
b. Nodes of Ranvier – gaps between the myline along the mylinated axon (unmyliated regions)
3. White matter – regions of brain and spinal cord which contain dense collections of mylinated fibers
4. Gray matter – regions of brain and spinal cord that contain mostly nerve cell bodies and unmyliated fibers
5. Terminal branches – extensions from the ends of axons
6. Axon terminals – aka terminal boutons – knob like distal endings of the terminal branches
7. Synapse – junction that mediates information transfer from one neuron to the next or from a neuron to an effector cell
