spinal cord : sensory and motor systems Flashcards
what are the two major parts of the nervous system ?
CNS - brain and spinal cord
PNS - nerves that are connected to tissues
what are the motor components of the nervous system ?
. voluntary ( somatic ) - innervates skeletal muscle
. involuntary ( autonomic ) - innervates smooth and cardiac muscle and glands
what is the function of baroreceptor?
located in the walls of large arteries ( aorta and carotid artery ) and they monitor blood pressure by monitoring the strength of the pulse
e.g baroreceptors will signal to the central nervous system that blood pressure is high , so motor nerves that come from particular motor neurons that come from the CNS that innervate heart muscle to slow heart muscle down .
what do the 12 cranial nerves do?
12 pairs of cranial nerves connect face, head and neck to the brain
what do the 31 pairs of spinal nerves do ?
31 pairs of spinal nerves connecting rest of the body to the spinal cord
what is the peripheral and central nervous system relations and functions ?
- stimulus
- receptors which are responsive to certain stimuli , transduction occurs which is converting stimuli into electrical activity
- send electrical activity via sensory/afferent nerves to the CNS
- interneurons in the CNS are able to instruct and command via the motor/efferent nerve that innervate effector tissues in body
- effector tissue is a general term for muscle and for glands that produce a response
what is the basic structure and function of the spinal cord ?
. part of CNS
. enclosed by bones of the vertebral column
. long ( 0.5 - 0.75 m ) extends from the base of the brain to the level of 1st lumbar vertebrae
. bilaterally symmetrical , has a left and right side ( anatomically and functionally )
. connected to body tissues ( e.g. skin , muscle ) by spinal nerves passing between vertebral bones
. involved in sensory and motor functions of the body below the neck
. comprises 29 adjoining segments : similar structure
. top-to-bottom functional map of adjoining body parts
what brainstem ?
. lowest part of the brain and is connected to the spinal cord
how do spinal nerves exit/enter spinal cord ?
spinal nerves enter/exit between vertebral bones held apart by cartilage discs
what happens if cartilage disc collapses ?
spinal nerves passing through get crushed and causes loss of function and pain
e.g. sciatica
how many spinal segments do we have in the spinal cord ?
29 spinal segments
what is the function of the 29 spinal segments ?
. mediate sensory and motor functions related to different body parts , top-to-bottom
what is the basic structure of 29 spinal segments ?
. 8 cervical - concerned with sensory/motor functions coming from ( neck , upper limbs )
. 12 thoracic - concerned with sensory/motor functions coming from ( trunk )
. 5 lumbar - concerned with sensory/motor functions coming from front pelvis and lower limb
. 4 sacral - concerned with sensory/motor functions coming from ( back pelvis and lower limb )
. all segments have a common structural plan
. but with subtle regional differences in anatomy because of their relations to different body parts
how do spinal nerves get in and out form peripheral tissues into the spinal cord through the gaps in the discs ?
each spinal segment has a pair of spinal nerves one on the left and one on the right , when spinal nerves get through gaps in the cartilage they divide in 2 inside the vertebral column to form dorsal ( back ) and a ventral (front )nerve root
what is the function of dorsal root ?
send input into spinal cord : sensory input from receptors via axons of dorsal root ganglion ( DRG ) cells
what is the function of ventral root ?
sends outputs from spinal cord : voluntary and involuntary motor outputs mainly to skeletal and smooth muscle
what are examples of somatic sensory inputs that travel into dorsal part of spinal cord ?
. merkels disc - signal texture
. free nerve ending - signal pain or thermal
. meissner’s corpuscle - signal light pressure
. pacinian corpuscle - signal vibration and deep pressure
. ruffini endings - signal skin stretch
what is the common structure in each spinal cord segment ?
inner = grey matter outer = white matter
what is the structure and function of inner = grey matter in spinal cord segment ?
. contains spinal neuron cell bodies and dendrites
. H-shaped with 3 pairs of horns
. dorsal horn : touch , pain and kinesthetic sensory inputs
. ventral horn : send voluntary motor output to skeletal muscle
. lateral horn : send autonomic output to smooth muscle and glands
what is the function and structure of outer white matter in spinal cord segment ?
. axon pathways ( tract )
. sends somatic sensory information up to the brain
. sends motor instructions from the brain to ventral or lateral horn motor neurons
why is white matter in spinal segment white ?
white because axons in spinal cord have myelin around them
what is myelin and its function ?
. membrane of particular type of glial cell that wrap repeatedly around axons to insulate them
. function is to speed velocity of impulse conduction in axon
how does a typical cross section of cord segment look like ?
. dorsal = posterior
. ventral = anterior
. h- shaped grey matter has 9 layers of separate cell bodies of spinal cord which are numbered form 1-9 in roman numerals
- layer 1-6 : have dorsal horn , all nuerons are concerned with somatic sensations ( touch , pain )
- layer 8-9 : contain ventral horn of spinal cord , contain motor neuron that innervate skeletal muscle ( voluntary motor )
layer 7 : contains ( autonomic motor )
where does each segment receive sensory input and send motor output from ?
. each segment receives sensory input and sends motor output to the same regions of the body via its pair of spinal nerves organised in the strips