N
dorsal horn: sensory or motor?
sensory
ventral horn: sensory or motor?
motor
nucleus vs nerve?
group of cell bodies in the CNS; bundle of axons found in the PNS
dermatomes?
region of skin innervated by the pair of dorsal roots from one
spinal segment (afferent sensory fibers)
What is Somatosensation?
the sense of touch, proprioception, vibration, pain and temperature
why is the cervical and lumbosacral spinal cords enlarged?
increased input and output related to the limbs
afferent fibers?
fibers bringing input to a structure (periphery to CNS)
dorsal root ganglion?
cluster of sensory neurons within the dorsal horn
what roots is the brachial plexus formed by? and where does it extend? what does it provide?
C5-T1; between the anterior and middle scalene muscles, and travels in the axilla to supply the upper extremity with sensory and motor innervation
what are the two neural pathways that carries the somatosensory information from the periphery to the brain?
Dorsal Column Medial Lemniscus System (DCML)
Anterolateral System
efferent fibers?
fibers carrying output from a
structure (motor output from CNS to muscles)
white vs gray matter?
myelinated axons; cell bodies in the PNS
cauda equina and filum terminale
nerve roots at the lower end of the spinal cord; a thickening of the pia (anchors the spinal cord to the coccyx)
How does sensory input get from
the periphery, to the spinal nerves,
and eventually to the primary
somatosensory cortex? (3)
1) Sensory Stimulus (origin) = Touch
2) Sensory Nerve (bundle of peripheral axons) = Supraclavicular Nerve
3) Termination = Primary Somatosensory Cortex (processes the touch)
what is the set of three neural pathways carry unconscious proprioception (somatosensory?
Dorsal Spinocerebellar Tract
Cuneocerebellar Tract
Ventral Spinocerebellar Tract
Dorsal Column Medial Lemniscus System (DCML)
Primary pathway that carries information about discriminative touch, conscious proprioception, and vibration
Anterolateral System
Pain, temperature, crude touch (sense touch but do not locate)
what are mechanoreceptors? superficial receptors (3)? deep receptors (3)?
The sensory receptors mediating tactile senses
Meissner Corpuscle, Merkel Disk, Free Nerve Endings
Pacinian Corpuscle, Ruffini Ending, Hair Follicle
what are the two things sensory receptors are responsible for?
Responsive to internal or external stimuli
Responsible for transduction of environmental energy into
electrical/chemical signal in the CNS
what are the four features of the sensory receptors?
1) Modality/Specificity: respond best to one type of stimulus (mechanical, thermal, chemical, visual, auditory)
2) Sensitivity: intensity of stimulus needed for the receptor to detect the stimulus
■ Low threshold = respond more easily (less intensity needed)
■ High threshold = stronger/more intense input needed to respond
3) Receptive Field: the surface area in which the receptor is located and where stimuli will activate a specific receptor
■ Tactile acuity is determined by size of the receptive field and density of the receptors (small sizer, more precise)
4) Adaptation Rate: the period of time the sensory stimulation continues; how quickly a receptor ceases to fire with ongoing input
■ Usually, the intensity diminishes when a stimulus is continuous for an extended period of time
what information does proprioception provide? (4)
Body, head, limb position
Muscle length
Muscle tension and force
Rate, timing, and sequencing of
movements
what is conscious proprioception? two types? joint receptors?
Awareness of where the body is in space (joint position, direction, velocity of joint
movements) >> Receptors relay impulses to the cerebral cortex
Static Kinesthesia: judge position of joint without seeing it or moving it
Dynamic Kinesthesia: perceive movement of a joint and judge direction and velocity
Ruffini, Pacinian, Free Nerve Endings
unconscious proprioception (3)? receptors (2)?
Detect changes in muscle length and muscle tension, regulate muscle tone, protect against excessive force generation in muscle
○ Receptors relay impulses to the cerebellum
● Receptors:
○ Muscle Spindles - detect muscle length
○ Golgi Tendon Organs (GTOs) - detect muscle tension
what fibers does the mechanoreceptors of the skin go down?
AB
what is the three neuron system of the DCML? and which way do they terminate?
o 1st Order Neuron: periphery --> spinal cord --> medulla (brainstem)
o 2nd Order Neuron: medulla --> thalamus
o 3rd Order Neuron: thalamus --> cortex
contralaterally to stimulus