Central nervous system - spinal cord Flashcards
What two main body structures are in the central nervous system?
the brain and the spinal cord
What two main structures are in the peripheral nervous system?
nerves
sensory organs
what are the three segments of the spine?
cervical
thoracic
lumbar
What is the name of the spinal segment at the neck?
cervical spine
what is the name of the spinal segment by the lungs?
thoracic
What is the name of the spinal segment in the lower back/pelvis area?
lumbar
what is at the bottom of the lumbar spine?
sacrum
coccyx
what is in-between the vertebrae?
vertebral disks
Where does the spinal chord extend from?
the brain stem
What is the name of the hole in the vertebrae that the spinal chord passes through?
the vertebral foramen
What shape/structure is the spinal cord? (4)
elongated, almost cylindrical structure
slightly flattened posteriorly and anteriorly
that gives off nerve pairs throughout its length
45cm long in males approx thickness of little finger
the spinal cord and cranial nerves are the only nervous tissue link between what?
the brain and the rest of the body
why is the spinal cord like a motorway?
because it is the main route for nerves to convey impulses from the brain to the various organs and tissues, where the defending nerves leave the cord at appropriate levels to pass to the structure that they supply
where do the sensory nerves from organs and tissues enter to ascend to the brain?
the spinal cord
what are the three primary functions of the spinal chord?
- to relay impulses to and from the brain
- to relay impulses from brain to tissues/organs
- to give sensory information from organs and tissues to the brain
what is the secondary function of the spinal cord?
to provide spinal reflexes independent of the brain
where does the spinal cord extend from in the skull?
the foramen magnum of the skull
where does the spinal cord extend to?
the region of the disc between the first and second lumbar vertebrae
What is the film terminale?
the trend of connective tissue connecting the lower end of the spinal cord to the lower end of the sacrum and coccyx
What is the Cauda equina?
the region of nerve routes surrounding the film terminals
What is the vertebral canal?
an elongated body cavity enclosed within the vertebrae that stores the spinal cord
what are the 2 functions of the vertebral canal?
to offer bony protection
to allow for normal movement to occur without the cord being compromised
What is cerebrospinal fluid?
a clear, colourless body fluid found in the brain and spinal cord
what is the function of cerebrospinal fluid? (4)
as it goes around the brain and spinal chord it
1. cushions organs
2. picks up needed supplies from the blood
3. gets rid of waste products from brain cells
4. homeostasis
How can cerebrospinal fluid help doctors find things out?
if the CSF has viruses or bacteria that can attack the brain so the doctor can examine this to see what is going on
What happens if there is a loss of CSF? (2)
- it can cause the brain to sag inside the skull, causing headaches
- it can cause a lower of pressure in the skull (intracranial hypotension)
Can leaks occurs in CSF?
yes it can occur in the brain (cranial CSF leak) or any point along the spinal cord (spinal CSF leak)
How does CSF protect the brain from damage?
it acts as a shock absorber, preventing damage from occurring when the cranium is hit/jolted
How does CSF help with homeostasis?
it regulated the distribution of metabolites surrounding the brain, keeping the environment ideal to prevent any damage to the nervous system
How does CSF help with clearing waste?
waste products from brain move into the CSF which then clears out through the arachnoid granulations into the Venous sinus so it can be absorbed into the blood stream
How many membranes are there covering the spinal cord? what are the layers called as a group?
3
meninges
What is the outermost layer of the meninges?
The dura mater
What is the dura mater?
a tough, thick, fibrous membrane, densely packed with collagen and elastin that surrounds the brain and spinal chord
What does the collagen and elastin provide to the dura mater? (3)
protection (both)
strength (collagen)
elasticity and reciprocal property (elastin)
what is the middle layer of the meninges?
the arachnoid mater
What is the arachnoid mater?
the middle layer of the meninges, a delicate membrane that is separated from the dura water by a thin layer of fluid
what does the arachnoid mater provide?
a suspension system as it protects the spinal chord from sudden impact
what is the innermost layer of the meninges?
Pia mater
What is the Pia mater? (4)
- the inner most of the meninges,
- a thin, loose membrane
- made of connective tissue
- that covers the whole of the brain and spinal cord
why is the Pia mater a vascular membrane?
because it has a rich network of blood vessels
What is the epidural space?
the space between the dura mater and the wall of the vertebral canal
What is in the epidural space?
fat, connective tissue and blood vessels
What is the function of the epidural space?
serves as padding around the spinal cord
What is the internal structure of the spinal cord?
it consists of grey matter and white matter
the grey matter is the shape of a letter H
it has a large anterior cleft
What is the grey matter of the spinal cord mainly made up of?
mainly cell bodies
What is the white matter in the spinal cord mainly made up of?
myelinated axon bundles
What is the grey matter pierces by in the spinal cord?
the central canal
What are the top parts of the letter H in the grey matter of the spinal cord called?
the dorsal horns
what are the dorsal horns stimulated by?
sensory impulses
What are the bottom parts of the letter H in the grey matter of the spinal cord called?
the ventral horns
What are the ventral horns stimulated by?
upper motor or connector neurones
What do the ascending tracts do in the white matter of the spinal cord?
carry sensory information from the body up the spinal cord to the brain
What do the descending tracts in the white matter of the spinal cord do?
carry motor information from the brain down the spinal cord to the body
What are the three ascending tracts in the white matter of the spinal cord?
Doral columns
Lateral spinothalamic tract
ventral spinothalamic tract
Where do the ascending tracts get information from? (4)
the skin (cutaneous receptors)
tendons
muscles
joints
what sensory information is the (ascending) Doral columns responsible for? (3)
fine touch
proprioception
vibration
What sensory information is the (ascending) lateral spinothalamic tract responsible for? (2)
pain and temperature
what sensory information is the ventral spinothalamic tract responsible for?
light touch
what are the two types of neurones in the central nervous system?
afferent neurones
efferent neurones
What do afferent neurones do?
carry sensory impulses from around the body to the central nervous system
What do efferent neurones do?
carry motor information away from the central nervous system to the muscles and glands to cause and effect and initiate action
what order is information received in the process of decision making regarding the CNS?
stimulus
receptor
sensory neruon
brain
motor neuron
effector
response
What order is information received in the process of the spinal reflex arc (involuntary)?
stimulus
receptor
sensory neuron
spinal reflex arc
motor neuron
effector
response
What are reflexes?
immediate and involuntary responses to changes in the internal or external environment that allow the body to maintain homeostasis
What is a reflex action?
an involuntary and immediate motor response to a sensory stimulus that initially bypasses the brain
What actions in the body is associated with reflex action?
skeletal muscle contractions
body functions (eg heart rate)
what are the 5 components of the reflex arc? in order (excluding stimulus and response)
receptor/sensor
afferent pathway
integrating center
efferent pathway
effector organs
What is the stretch reflex?
the contraction of a muscle in response to its passive stretching, involves only a sensory and motor neurone, a somatic reflex
What is an example of a stretch reflex?
the patellar tap (knee jerk)
What is the function of the stretch reflex?
to protect our joints from moving too far and damaging our muscles, ligaments and tendons
where can the stretch reflex happen?
anywhere a stretched tendon crosses a joint
what is an autonomic/visceral reflex?
autonomic, an contraction of smooth or cardiac muscle
what is the function of an autonomic/visceral reflex?
to maintain balance or function within the organ systems of the body
what is the difference between a visceral/autonomic and somatic reflex?
the visceral reflex happens internally in soft tissue organs
the somatic reflex happens in skeletal muscles
how many pairs of spinal nerves are there?
31 pairs
where do spinal nerves originate?
from the spinal cord
how are the spinal cords named and numbered?
according to the region and level the cord emerges
How many pairs of cervical spinal nerves are there?
8
How many pairs of thoracic spinal nerves are there?
12
How many pairs of lumbar nerves are there?
5
how many pairs of sacral nerves are there?
5
how many pairs of coccygeal nerves are there?
1
how many points of attachment to the spinal cord does each spinal nerve have?
2
What are the names of the points of attachment on each spinal nerve?
the posterior root (sensory fibres)
the anterior root (motor fibres)
where do each of the spinal nerves unite?
at the intervertebral foramen
Each spinal nerve contains a mixture of _______ and ________ fibres.
motor
sensory
how many roots does each spinal cord segment have?
4
2 anterior
2 posterior
what are anterior roots of the spinal nerves and what do they do?
efferent nerve fibres that carry stimuli away from the central nervous system
what are the posterior roots of the spinal nerves and what do they do?
afferent nerve fibres that return stimuli to the central nervous system
