Lecture 1 Flashcards
The vertebral column is divided into 5 sections:
Cervical (7) Rostral
Thoracic (12)
Lumbar (5)
Sacrum (Composite, 5 pieces)
Coccyx (Composite, 4 pieces) Caudal
The curved shape of the spine is created when infants:
Are learning to look up and sit up (Born with a straight/non curved vertebral column
Name the 3 anatomical sections of the vertebral column (Transverse view)
Body (Large anterior section), Spinous process (Posterior bony projection), Vertebral canal (Hollow center section holding the spinal cord - only about 50-75% of the space taken up by it)
The spinal nerves (Off of the spinal cord) are divided into 5 sections:
Cervical (8 pairs) - C1->C7 above vertebrae, C8->S5 below vertebrae
Thoracic (12 pairs)
Lumbar (5 pairs)
Sacral (5 pairs)
Coccygeal (1 pair)
Name and locate the landmarks of the spinal cord (4)
Cervical Enlargement - C4 vertebrae, C5 nerves (Brachial plexus)
Lumbar Enlargement - T12 vertebrae, L1/L2 nerves (Lumbar plexus)
End of the spinal cord - L2 vertebrae (S5 nerves)
Cauda Equina - No longer spinal cord, but spinal nerves off the spinal cord extend creating this “horses tail”
Spinal cord cross section: Ventral roots
Anterior side
Carries motor info out towards muscle
Spinal cord cross section: Dorsal roots
Posterior side
Carries sensory info back towards spinal cord
Spinal cord cross section: Gray matter
Anterior horn - muscle contraction
Lateral horn - cell bodies, autonomic nervous system
Posterior horn - taking in sensory info
Gray due to cell bodies of the neurons
Spinal cord cross section: White matter
Dorsal, ventral, lateral columns
White due to axons travelling down covered in myelin sheath
Types of info carried in spinal cord
Motor travels DOWN the spinal cord
Sensory travels UP the spinal cord
2 types of motor information and differences between them
Somatic
- Contraction of:
-Skeletal muscle
-Joints
-Aware and in control/voluntary
Autonomic
- Smooth muscle, cardiac muscle, or gland
-Not always in control/involuntary (Not
consciously in control
-Ex. Contraction of bladder
- 2 types of autonomic info
2 types of autonomic information and differences between them
Sympathetic
- Fight or flight
Parasympathetic
- More important at rest
What is a dermatome?`
An area of skin supplied by a group of sensory axons (the same group) of a particular spinal segment (all innervated by the same nerve)
Explains where sensory info goes to first before travelling to brain (T3 = nipple line, T10 = belly button
What is a myotome?
The group of muscles innervated by a particular segment
Most segments innervate more than one muscle, and most muscles are innervated by more than one segment
What are the tracts of the spinal cord?
Very organized multi-lane highway going up and down bringing specific info in each lane
Ascending tract - sensory info to brain
Descending tract - motor info from brain to muscles
Ascending tracts of spinal cord have how many neurons to reach the brain? Examples?
Sensory info takes primary, secondary and tertiary neurons
Most names explain where it travels to (Spinothalamic tract - spinal cord to thalamus, etc)
Dorsal column**
Descending tracts of spinal cord have how many neurons to go from brain to muscles? Examples?
Motor info takes just 2 neurons to get to the muscles (Upper and lower motor neurons AKA spinal, or peripheral nerves)
Corticospinal tract - cortex to spinal cord info transfer
What are the 3 different groups of Ascending tracts in the spinal cord?
- Spinothalamic system
- Lateral spinothalamic
- Anterior spinothalamic - Dorsal Columns (medial-Lemniscal system)
- Fasciculus gracilis
- Fasciculus cuneatus - Spinocerebellar system
- Posterior spinocerebellar tract
- Anterior spinocerebellar tract
What are the 2 different groups of Descending tracts in the spinal cord?
- Direct pathways (Pyramidal)
- Corticospinal - Indirect pathways (Extrapyramidal)
- Rubrospinal tract
What are the 2 sections of the Spinothalamic system (Ascending tract) and their purposes?
- Lateral spinothalamic tract
- Carries pain and temperature sensations from periphery to brain - Anterior spinothalamic tract
- Carries light touch (Wind, light brushing, NOT poking), pressure, tickle and itch sensations from periphery to brain
What are the 2 sections of the dorsal column (Medial-Lemniscal), their level of sensation, and purpose? (Ascending tract)?
Carries fine touch, proprioception, pressure and vibration sensations from the periphery to brain
- Fasciculus Gracilis
- Sensation below T6 dermatome - Fasciculus Cuneatus
- Sensation from dermatome T6 and above
What are the 2 sections of the Spinocerebellar system (Ascending tract) and their purposes?
Carries proprioceptive information from periphery to cerebellum (Used for coordination of movements and maintenance of posture
- Posterior spinocerebellar tract
- Info from lower extremities - Anterior spinocerebellar tract
- Info from L2 and above
What are the purposes of the direct (pyramidal) pathways, and why are they direct? (Descending tract)
Maintenance of muscle tone and controlling the speed and precision of skilled movements
- Direct since upper motor neurons synapse directly with lower motor neurons in spinal cord
What are the purposes of the indirect (extrapyramidal) pathways and why are they indirect? (Descending tract)
Involved in less precise motor control such as overall body coordination
- Indirect since upper motor neurons synapse in some intermediate nucleus (Group of cell bodies) rather than directly synapsing with lower motor neurons
What are the 2 sections of the corticospinal system and their purposes?
(Direct, Descending tract)
Upper motor neurons originate in cerebral cortex, descend in brainstem until caudal medulla
- Lateral corticospinal tract
- 75-85% of the neurons cross at pyramidal decussation and descend into this lateral corticospinal tract
- Used in contralateral limb movements (Since crosses over) - Anterior corticospinal tract
- 15-25% of the neurons descend uncrossed in spinal cord as the anterior corticospinal tract
- Used in trunk neck and shoulder movements
Both used for maintenance of muscle tone and controlling the speed and precision of skilled movements
How does the Autonomic nervous system function? (4 steps)
Preganglionic neuron
Synapses
Autonomic ganglia (Group of cell bodies)
Synapses
Postganglionic neuron
Synapses
Effector organ
What is a ganglion?
A group of neuron cell bodies (connected by synapses to different systems)
- Like a PRE drink
- Excites the transmission sending a signal to a specific area
Sympathetic nervous system divergence and ganglionic neurons and purpose?
This system prepares body for fight or flight
- Excitatory towards things that will be helpful (heart rate)
- Inhibitory towards things that won’t be (digestion)
Preganglionic neurons originate in gray matter between T1 and L2
There is a lot of divergence from preganglionic -> postganglionic
- Mass activation, so one preganglionic leads to many postganglionic
Has short preganglionic neurons, and long postganglionic neurons
- Due to preganglionic neurons being close to spinal cord, so longer to reach the target organs from there, but signal is fast to get to cord
Parasympathetic nervous system divergence, ganglionic neurons and purpose?
This system is predominant at rest
- Excitatory towards things that will be helpful (Bile secretion, blinking)
- Inhibitory towards things to relax better (Decrease heart rate)
Preganglionic neurons originate in brainstem and gray matter between S2 and S4
There is less divergence from preganglionic -> postganglionic
- Due to picking and choosing what is activated at rest, not mass activation/everything at once like sympathetic
Has long preganglionic neurons and short postganglionic neurons
- Due to being postganglionic neurons being close to target organs, so longer to get to spinal cord, but very close to organs after
75% of outflow is from the vagus nerve
What happens if only one system is affected by a spinal cord injury (Ex. Just the sympathetic nervous system?)
Still causes many issues since usually a good balance of the two working, causing different issues through the organs and body
What is a reflex and give an example of the process of a somatic reflex (5 steps)
An involuntary motor response to a sensory stimulus
- Sensory receptor (Feel tap on patellar tendon)
- Afferent neuron (Sends message to cord)
- Association neuron (Allows synapse)
- Efferent neuron (Message to kick out leg)
- Effector cells (Contracts muscles to kick the leg out)
Afferent vs. Efferent
Afferent
- Sends sensory feedback to spinal cord/towards CNS
Efferent
- Motor neurons that carry impulses from CNS to muscles to cause movement
What could an example of an autonomic reflex/baroreflex be?
Balancing blood pressure by increasing or decreasing heart rate whenever the baroreceptors detect a large enough change
