Nervous System Flashcards
objective of the nervous (and endocrine) systems
keep controlled conditions within limits that maintain life
- nervous system regulates body activities by responding rapidly using nerve impulses
- endocrine system responds by releasing hormones
four things the nervous system is responsible for
- perceptions
- behaviors
- memories
- initiating voluntary movements
TRUE OR FALSE: The nervous system is one of the smallest and yet the most complex of the 11 body systems.
TRUE.
two main subdivisions of the nervous system
- central nervous system (CNS)
2. peripheral nervous system (PNS)
_______ deals with normal functioning and disorders of the nervous system.
neurology
composition of the central nervous system (CNS)
brain and spinal cord
____ is the part of the CNS that is located in the skull and contains about 85 billion neurons
brain
____ is connected to the brain through the _____ of the _______ and is encircled by the bones of the vertebral column
spinal cord
foramen magnum
occipital bone
number of neurons that the spinal cord contains
about 100 million neurons
processes that are done by CNS
- processes incoming sensory information
- source of thoughts, emotions, and memories
- processes signals that stimulate muscles to contract
- processes signals that stimulate glands to secrete
composition of the peripheral nervous system (PNS)
all nervous tissue outside the CNS
- nerves
- sensory receptors
____ is a bundle of hundreds to thousands of axons plus associated connective tissue and blood vessels that lies outside the brain and spinal cord
nerve
cranial nerves : ______ :: spinal nerves : ______
cranial nerves : 12 PAIRS :: spinal nerves : 31 PAIRS
sensory receptors
refers to a structure of the nervous system that monitors changes in the external or internal environment
examples of sensory receptors
- touch receptors in the skin
- photoreceptors in the eye
- olfactory (smell) receptors in the nose
two divisions of the PNS
- sensory
2. motor
sensory division of PNS
sensory or afferent division
- conveys input into the CNS from sensory receptors in the body
- provides the CNS with sensory information about the somatic senses (tactile, thermal, pain, and proprioceptive sensations)
- provides the CNS with sensory information about the special senses (smell, taste, vision, hearing, and equilibrium)
motor division of PNS
motor or efferent division
- conveys output from the CNS to effectors (muscles and glands)
two divisions of the motor division of PNS
- somatic nervous system
2. autonomic nervous system
somatic nervous system (SNS)
- conveys output from the CNS to skeletal muscles only
- because its motor responses can be consciously controlled, the action of this part of the PNS is voluntary
autonomic nervous system (ANS)
- conveys output from the CNS to smooth muscle, cardiac muscle, and glands
- because its motor responses are not normally under conscious control, the action of ANS is involuntary
- composed of three main branches
three branches of ANS
- sympathetic nervous system
- parasympathetic nervous system
- enteric nervous system
TRUE OR FALSE: With a few exceptions, effectors receive innervation from both of the branches of ANS, and usually the two branches have opposing actions.
TRUE.
example of the opposing actions; neurons of the sympathetic nervous system increase heart rate WHILE neurons of the parasympathetic nervous system slow it down
compare the sympathetic and parasympathetic nervous system
sympathetic nervous system helps support exercise or emergency actions such as the fight-or-flight response
parasympathetic nervous system takes care of rest-and-digest activities
enteric nervous system (ENS)
- extensive network of over 100 million neurons confined to the wall of the GI tract
- helps regulate the activity of the smooth muscles and glands of the GI tract
- ENS can function independently but communicates with and is regulated by other branches of the ANS
three main functions of the nervous system
- sensory function
- integrative function
- motor function
sensory function of the nervous system
- sensory receptors detect internal stimuli (e.g. increase in bp) or external stimuli (e.g. raindrop landing in your arms)
- sensory information is carried into the brain and spinal cord through cranial and spinal nerves
integrative function of the nervous system
- nervous system processes sensory information by analyzing it and making decisions for appropriate responses (integration)
motor function of the nervous system
- happens after integration
- nervous system may elicit an appropriate motor response by activating effectors (muscles and glands) through cranial and spinal nerves
- stimulation of the effector causes muscles to contract and glands to secrete
example of how the three basic functions of the nervous system occur
answering the cellphone after hearing it ring
- sound of the ringing cellphone stimulates sensory receptors in the ears (sensory function)
- auditory information is subsequently relayed into the brain where it is processed and the decision to answer the phone is made (integrative function)
- the brain then stimulates the contraction of specific muscles that will allow you to grab the phone and press the appropriate button to answer it (motor function)
nervous tissue comprises two types of cells: ____ and ____
neurons and neuroglia
neurons
- forming the complex processing networks within the brain and spinal cord
- connect all regions of the body to the brain and spinal cord
- provide most of the unique functions of the nervous system (i.e. sensing, thinking, remembering, controlling muscle activity, and regulating glandular secretions)
TRUE OR FALSE: Because of neurulation, most neurons have lost the ability to undergo mitotic divisions.
FALSE. Because of SPECIALIZATION, most neurons have lost the ability to undergo mitotic divisions.
neuroglia
- smaller cells but outnumber neurons by appx. 25 times
- support, nourish, and protect neurons, and maintain the interstitial fluid that bathes them
- continue to divide throughout an individual’s lifetime
TRUE OR FALSE: Only neuroglia differ structurally depending on whether they are located in the CNS or PNS.
TRUE OR FALSE: BOTH neurons and neuroglia differ structurally depending on whether they are located in the CNS or PNS.
the differences in structure correlate with the differences in the function of the CNS and the PNS
neurons (nerve cells) possess ______, the ability to respond to a stimulus and convert it into an action potential
electrical excitability
stimulus
any change in the environment that is strong enough to initiate an action potential
action potential (nerve impulse)
- an electrical signal that propagates (travels) along the surface of the membrane of a neuron
- begins and travels due to the movement of ions (i.e. sodium and potassium) between interstitial fluid and the inside of a neuron through specific ion channels in its plasma membrane
- once begun, a nerve impulse travels rapidly and at a constant strength
three parts of most neurons
- cell body
- dendrites
- axon
cell body in the neuron
- aka perikaryon or soma
- contains a nucleus surrounded by cytoplasm that includes typical cellular organelles (lysosomes, mitochondria, a Golgi complex)
- also contain free ribosomes and prominent clusters of endoplasmic reticulum called Nissl bodies
what happens to the newly synthesized proteins produced by Nissl bodies?
- used to replace cellular components as material for the growth of neurons
- used to regenerate damaged axons in the PNS
the cytoskeleton includes both ____ and ____
- neurofibrils composed of bundles of intermediate filaments that provide the cell shape and support
- microtubules that assist in moving materials between the cell body and axon
lipofuscin
- contained in aging neurons
- a pigment that occurs as clumps of yellowish-brown granules in the cytoplasm
- product of neuronal lysosomes that accumulates as the neuron ages, but does not seem to harm the neuron
ganglion
- collection of neuron cell bodies outside the CNS