functional anatomy of the spinal cord

Question 1

what does the cord contain?

Answer 1

-spinal nerves which contain reflex circuits that control rapid reactions to environmental changes
-grey matter
-white matter

Question 2

what is the grey matter of the spinal cord?

Answer 2

-a site for integration of postsynaptic potentials
-it contains the neuron cell bodies and synapses and also has horns

Question 3

what is the white matter of the spinal cord?

Answer 3

-contains major sensory and motor tracts(bundles of axons) that transmit info between the brains and limbs, trunk and organs of the body

Question 4

what are the regions of the spinal cord?

Answer 4

-the spinal cord begins as a. continuation of the medulla oblongata to the conus medullaris
-it has a cauda equine (horses tail)=roots of the lower spinal nerves
-it has cervical,thoracic,lumbar and sacral regions
-has plexuses where the nerves join together

Question 5

what are spinal nerves?

Answer 5

bundles of sensory and motor axons that are paths of communication between the spinal cord and specific regions of the body

Question 6

how are spinal nerves divided?

Answer 6

nerves divide into the anterior (ventral) and posterior (dorsal) roots as they connect to the spinal cord

Question 7

how do ventral and dorsal roots differ?

Answer 7

-ventral roots contain axons of motor neurones which conduct nerve impulses from the CNS to effectors (muscles and glands)
-dorsal roots contain sensory axons, which have terminals at sensory receptors with cell bodies in the dorsal root ganglion and axons synapse in the spinal cord

Question 8

state the different coverings(layers) of the spinal cord?

Answer 8

-spinal meninges
-dura mater
-arachnoid mater
-pia mater

Question 9

what is the spinal meninges?

Answer 9

-tissue coverings that protect the cord and provide physical stability

Question 10

what is the dura mater?

Answer 10

-the thought mother which forms a sac that encloses the entire spinal cord, there is epidural space that lies between the dura and the inner surface of the bony vertebrae

Question 11

what is the arachnoid mater?

Answer 11

-it is attached to the inside of the dura and forms the roof of the subarachnoid space in which cerebral spinal fluid (CSF) circulates

Question 12

what is the Pia mater?

Answer 12

-the pia mater is pressed-up against the cord and is filled with blood vessels that supply nutrients to it

Question 13

how is epidural anaesthesia administered?

Answer 13

-a needle is placed between the bones of the posterior spine until it just penetrates the ligaments flavour yet remains superficial to the dura mater

Question 14

when and why is anaesthetic given?

Answer 14

-epidural anaesthesia is given to women who atrophy about to go on labour
-local anaesthetic is given to provide pain relief whilst complete anaesthesia can also be given if a caesarean section is needed

Question 15

where is the site used for most lumbar (lower back) punctures?

Answer 15

-between the 3rd and 4th (or 4th and 5th) and the lumbar vertebrae-below the termination of the actual cord in the region of the cauda equina

Question 16

how can CSF be sampled and anaesthetic be given?

Answer 16

-with a needle in the subarachnoid space,CSF can be sampled and anaesthetic can also be given but only using 1/10th of the dose required for epidural anaesthesia

Question 17

what type of neurones do the dorsal and ventral horns contain?

Answer 17

dorsal=sensory neurons
ventral=motor neurons

Question 18

state and describe the white matter tracts

Answer 18

-the spinothalamic tract-it transmits sensory info from the spinal cord to the brain (ascending)
-the corticospinal tract-it transmits motor info from the brain to the spinal cord (descending)

Question 19

how do white matter tracts carry specific kinds of information?

Answer 19

-the different motor tracts carry nerve impulses from specific areas of the brain to the body e.g
-the lateral corticospinal tract controls precise, agile,highky skilled movements of the hands and feet
-the ventricular (anterior) corticospinal tract controls movement pf the trunk and limbs

Question 20

what types of sensory information are carried by the dorsal (posterior) column?

Answer 20

-mainly carries touch and proprioception

Question 21

which sensory information is primarily transmitted by the lateral tracts?

Answer 21

the lateral tracts carry mainly pain and temperature senses

Question 22

what is the role of first-order sensory neurons?

Answer 22

-they are PNS and transmit sensory information from the receptor to the spinal cord

Question 23

where are the cell bodies of first-order sensory neurons located?

Answer 23

-the cell bodies of first order sensory neurons are located in the dorsal root ganglion (DRG)

Question 24

how does the axon of a first-order sensory neuron contribute to the transmission of sensory signals?

Answer 24

the axon of the first order neuron carries the sensory signal from the receptor to the spinal cord where it synapses onto a second-order neuron

Question 25

where are the cell bodies of second order sensory neurons located?

Answer 25

-in the dorsal horn of the spinal cord

Question 26

what pathway is taken by the axons of secondary-order sensory neurons?

Answer 26

they travel up the spinal cord and decussate (cross) in the brainstem

Question 27

what happens when the icons of second-order neurons decussate in the brainstem?

Answer 27

their axons cross to the opposite side of the brainstem before continuing to the thalamus and synapsing onto third order neurons

Question 28

what is the role of second-order sensory neurons?

Answer 28

they ansmit sensory info from the spinal cord to the thalamus

Question 29

what is the role of third order sensory neurons?

Answer 29

they conduct impulses from the thalamus ti the primary somatosensory area of the cortex