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A&P.nervous.ch12
| Question | Answer |
|---|---|
| spinal cord - functions (3) | 1.major communication link between brain and PNS; 2. integrates incoming information and 3. produces responses through reflex mechanisms |
| spinal cord begins | at foramen magnum |
| spinal cord ends | at the level of the second lumbar vertebrea |
| how many pairs of spinal nerves? | 31 - remember nerves comes out in the intervertebral foramen & the sacral foramina |
| how many vertebrae are there? | 7 cervical; 12 thoracic; 5 lumbar; one sacral bone & 1 coccygeal bone for a total of 26 |
| how many openings are in the sacral bone? | 4 openings in the bone itself (remember that there is an additional intervertebral foramen between L5 and the sacral promontory |
| which is longer, the spinal cord or the vertebral column? | the vertebral column - the spine stops growing before the bones of the vertebral column |
| cervical enlargement of the spinal cord | corresponds to area where axons that supply the upper limbs enter and leave the spinal cord |
| where is the cervical enlargement? | inferior cervical region C2-C7 |
| lumbrosacral enlargement | inferior thoracic, lumbar and superior sacral regions-site where axons supplying the lower limbs enter or leave the cord |
| conus medullaris | the end of the spinal cord is a conelike region - |
| where is the tip of the spinal cord | the conus medullaris extends to the level of the second lumbar vertebra |
| cauda equina | horse tail - roots of spinal nerves extending inferiorly from the lumbosacral enlargement and conus medullaris resemble a horse's tail |
| meninges | spinal cord and brain are surrounded by connective tissue membranes (there are more than one) G. meninx "membrane" |
| what is the most superficial and also thickest membrane? | dura mater - l. dura "hard" Mater "mother" because it is "sheltering" the central nervous system |
| thecal sac | surrounds the spinal cord in continuous fashion |
| what separates that dura mater (outermost layer of spine?) from the periosteum of the vertebral canal? | epidural space - contains fat as a cushion |
| after the dura mater? | subdural space - contains small amount of serous fluid |
| what is next layer? | arachnoid "spiderlike" "cobwebs" |
| what is between arachnoid mater and the pia mater? | subarachnoid space |
| pia mater | "affectionate" - bound very tightly to the surface of the spinal cord |
| what is contained in the subarachnoid space? | blood vessels, weblike strands of arachnoid mater and cerebrospinal fluid (CSF) |
| why must great care be exercised when putting needles into the subarachnoid space? | sterile environment-don't want to introduce germs |
| sulcus | Latin a furrow or a ditch |
| cross section of spinal cord- | contains different areas |
| tracts | Latin "tractus" path, track or way - so "tracts" are on elongated area |
| what are the nerve tracts? | fasciculi or pathways within the white matter columns of the spinal cord |
| what is another name for the fasciculi? | nerve pathways |
| central gray matter of the spine is organized into | horns - a thin posterior (dorsal) horn and a larger anterior (ventral) horn |
| what are the small lateral horns of the gray matter of the spinal cord associated with? | the autonomic nervous system |
| what connects the two halves of the spinal cord? | they are connected by gray and white commissures - |
| what is a commissure and how is it spelled? | Latin "commissura" to send together; to combine (think commission) two "m" two "s" |
| how many commissures are there? | two - one gray, one white |
| what is the purpose of the commissures? | contain axons that cross from one side of the spinal column to the other |
| what is in the middle of the gray commissure? | the central canal |
| what is the Ventral root composed of? | spinal nerves arise from numerous rootlets; about six to eight of these rootlest combein to form the ventral root |
| what is dorsal root composed of? | about six to eight rootlets |
| what do the dorsal and ventral roots go? | ventral and dorsal roots extend laterally from the spinal cord, passing through the subarachnoid space, piercing the arachnoid mater and dura mater - then join one another to form a spinal nerve |
| what does each dorsal root have that ventral roots do not have? | dorsal root ganglion |
| what are the dorsal root ganglia? | G. ganglion "swelling or knot" |
| shwere are the cell bodies of motor neurons located? | in the anterior and lateral horns of the spinal cord gray matter |
| multipolar somatic motor neurons are in the | anterior horn |
| what is the anterior horn also called? | the motor horn |
| dorsal roots contain ________ axons? | sensory axons - going to the brain (afferent or ascending) |
| ventral roots contain ______ axons? | motor axons - message from the brain to the muscles or glands (efferent - they have an effect on something) |
| what is the basic functional unit of the nervous system? and is the smallest, simplest portion capable of receiving a stimulus and producing a response? | a reflex arc |
| reflex arc has 5 basic components: | 1) a sensory receptor, 2) a sensory neuron 3) an interneurons 4) a motor neuron and 5) an effector organ |
| reflex (def.) | an automatic response to a stimulus prodcued by a reflex arc; occurs without conscious thought |
| reflex arc (3 steps) | 1. stimulus detected by a sensory receptor 2. sensory neuron conducts an action potential to the spinal cord 3 |
| next 3 steps | . in the spinal cord, the sensory neuron synapses with an interneuron 4. the interneuron synpases with a motor neuron 5. a motor neuron axon projects to an effector ogran |
| different reflexes are simple, some complex | monosynaptic reflexes - simple neuronal pathways |
| somatic reflexes | remove body from painful stimuli that could cause tissue damage; prevent falls; or move quickly away from danger |
| many kinds of reflexes- major types include | 1. the stretch reflex 2 the Golgi tendon reflex, the withdrawal reflex and the crossed extensor reflex |
| stretch reflex | 1. muscle spindles detect stretch of a muscle 2. sensory neurons conduct action potentials to the spinal cord 3. sensory neurons synapse directly with alpha motor neurons 4. stimulation of alpha motor neurons causes the muscle to contract |
| stretch reflex (ex.) | muscles that hold up head - we don't feel them until we fall asleep; when the head rolls forward, the reflex wakes us up & the head is restored to proper posture |
| golgi tendon reflex | prevents contracting muscles from applying excessive tension to tendons |
| golgi tendon organs | are encapsulated nerve endings that have numerous terminal branches with small swellings associated with bundles of collagen fibers in tendons |
| where are golgi tendon organs located? | near the muscle-tendon junction |
| withdrawal reflex or "flexor" | remove a limb from painful stimulus |
| stretch reflex sensory receptors | muscle spindle; consists of 3-10 small, specialized muscle cells |
| stretch reflex - where do axons synapse? | alpha motor neurons |
| what do the "alpha" & "gamma" refer to? | size of the motor neurons |
| Part 3 - crossed extensor reflex | when a withdrawal reflex is initiated in one lower limb, the crossed extensor reflex cause extenstion of the oposit lower limb-to prevent falls |
| peripheral nerves consist of (3) | axons, Schwann cells, and connective tissue - but not neurons??? |
| epi | prefix meaning on, following, or subsequent to Gr. |
| epineurium | the outermost supporting structure of peripheral nerve tranks; the connective tissue of the epineurium is continuous with the dura mater surrounding the CNS |
| perineurium | surrounds groups of axons to form nerve fascicles |
| endoneurium | each axon, or nerve fiber and its Schwann cell sheath are surrounded by a delicate connective tissue layer |
| stroma | the framework, usually of connective tissue, of the organ, gland or other structure |
| dermatonal map | nerves arising from each region of the spinal cord and vertebral column supply specific regions of the body; the dermatonal map supply sensory cutaneous distribution of the spinal nerves |
| dermatome | area of skin supplied with sensory innervation by a pair of spinal nerves |
| ramus | "branch" L. |
| each spinal nerve has a dorsal and ventral | ramus (the singular) |
| dorsal rami | innervat most of the deep muscles of the dorsal trunk responsible for movement of the vertebral column |
| ventral rami - distributed in two ways | 1.) in thoracic region, ventral rami form intercostal nerves 2. ventral rami of remaining nerves form plexuses |
| plexus | means "braid" - a network of interjoing of nerves & blood vessels |
| phrenic nerve | controls breathing - damage to phrenic nerver during open heart surgergy must be avoided; some cancers can depress the phrenic nerve |
| phrenic | Gr. diaphragmatic -- also -phrenia - relating to the diaphrams, mind, heart (as the seat of emotions) |
| where is phrenic nerve located? | originates from spinal nerves c3-c5; derived from both the cervical & brachial plexus |
| brachial plexus | fomred by ventral rami of the spinal nerves C5-T1 |
| brachial plexus contains what important nerves? | radial nerve, median nerve & ulnar nerve |
Created by:
walterina4327