Nervous Integration Flashcards
How many spinal nerves are there and what is their distribution?
31 pairs of spinal nerves
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal
How are the spinal nerves named?
Cervical nerves named for the vertebra below them
- except for cervical nerve 8 b/c theres only 7 cervical vertebrae
- Cervical nerve 8 exits below C7 and above T1
- Cervical nerve 1 below occiput and abov 1st cervical vertebra
Thoracic, Lumbar, Sacral, and coccygeal nerves are named for the vertebra above them
What composes a typical spinal nerve?
A mixed nerve with efferent and afferent neurons
Contains Connective tissues
- endoneurium
- perineurium
- epineurium
What purpose does insulation serve in a typical spinal nerve?
allows you to disrciminate between sensory input
- one axon per region
- impulse on axon doesn’t stimulate other axons because of insultation
What are dermatomes? What are the dermatomes in the picture?
Every piece of skin has adesignated spinal nerve that innervates it
-except face
What are the cranial nerves and hw many of them are there?
12 pairs of cranial nerves
Motor components
-arise from brainstem gray matter
Sensory components
-arise from ganglia outside brain
What is the cranial nerve mnemonic?
What is the cranial nerve function mnemonic?
Draw the weird cranial nerve picture
What are the essential functions of the nervous system?
- Sense changes in the internal and external environments
- Integrate and interpret incoming sensory information
- Respond, if necessary to environmental changes
What is a sensation?
stimulus sensed and sent to CNS
How is a sensation different from perception?
a perception is a sensation that is also routed to cerebral cortex and you are aware of it
What are the levels sensation?
- spinal (reflex only)
- brainstem (reflex only)
- thalamus (crude perception)
- cerebral cortex (precise perception)
What is sensory modality?
Specific types of receptor based on sense
-eg can’t feel cold with heat receptors
What are the components of sensation?
- Stimulation - stimulus + Receptor
- Transduction - receptor tranduces stimulus to sensory neuron
- Conduction - conduction of nerve impulse
- Translation - synapse in CNS not necessarily consciousness
What are generator potentials?
- stimulation of receptor directly causes depolarization of sensory neuron
- action potential is initiated if the stimulus is a threshold stimulus
- all receptors do this except those for the special senses
What is a Receptor potential?
- receptor cell releases neurotransmitter onto first neuron in pathway
- neurotransmitter will produce depolarization or hyperpolarization of a bipolar neuron
- bipolar neuron is the 1st neuron on pathway to CNS
- can inhibit/excite the 1st neuron
- used by the receptors for the special senses
What is the receptor difference between generator and receptor potentials?
Generator potential
-receptor is dendritic end of sensory neuron
Receptor potential
-receptor is separate cell
How does amplitude of potentials vary?
Amplitude of both types of potentials vary with stimulus intensity
- high amplitude = high frequency of firing in pathway
- low amplitude = low frequency of firing in pathway
more ap/sec that reach CNS are interpreted as more intense
-too strong = pain stimulus
What are the types of recetors based on the location in the body and based on the type of stimulus it detects?
Based on Location in the Body
- interoceptors (visceroceptors)
- exteroceptors
- proprioceptors
Based on Type of Stimulus Detected
- mechanoreceptors
- thermoreceptors
- chemoreceptors
- photoreceptors
- nociceptors
What are the different types of adapting receptors?
Fast-adapting (phasic) receptors
- Adapt very quickly
- Specialized for signaling changes in a particular stimulus
- Pressure, touch, hot, smell
Slow-adapting (tonic) receptors
- Adapt slowly, continuing to initiate impulses as long as stimulus persists
- Pain, body position, cold, chemical composition of blood
What is an afterimage?
after removal of stimulus the receptors are still sending info down signal pathway
What is projection?
each receptor has corresponding neuron in cerebral cortex
Where does adaptation occur?
Most at receptor level but further adaptation ocurs during central processing
What are cutaneous sensations?
- tactile, thermal and pain sensations
- located in the edge of dermis/epidermis
- higher distribution of receptors in areas where you need more sensation like fingertips
What are the types of nociceptors?
Fast (first) pain = sharp, localized, stabbing felt at time of injury
Second (slow) pain = longer-lasting, dull, diffuse feeling
What is the difference between somatic and visceral pain?
Somatic pain - muscle, skin, tendons, bone
Visceral pain - organs
What chemicals are released at injury sites and what do they do?
Bradykinin, serotonin, protaglandins, histamine, K+ and ATP
-stimulate nociceptors and activate cascade of rxns related to healing
What is referred pain?
Somatic and visceral pain share tracts so sometimes pain can be misinterpreted as coming from other regions
What is the spinal gating of pain?
Stop perception of pain by releasing analgesics to inhibit the synapse at the spine
-sensation still ocurring but not travelling to cerebrum
What are proprioceptive sensations?
Proprioceptors are located in the muscle, joint, tendons
- know how the body is oriented in space
- adapt slowly
What three neurons are involved in somatosensory pathways?
From receptor to cerebrum
- First-order neuron = sensory neuron
- dendrite attached to peripheral receptor
- dendritic fiber passes through spinal or cranial nerve to synapse in CNS
- Second-order neuron = association neuron
- cell body in CNS; receives synapses from 1st order neuron
- axon always decussates as it ascends to thalamus where it synapses
- Third-order neuron = association neuron
- cell body in thalamic gray matter; synapse w/ 2nd order neuron
- axon passes thru cerebral white matter
- synapses w/ somatosensory neuron = perception
What are the different sensory pathways?
Dorsal Column Pathway
-Fine touch, kinesthesia, vibration, weight discrimination
Anterolateral Pathway
- Lateral spinothalamic tract - pain, heat
- Anterior spinothalamic tract - crude touch
How does the sensory information ascend the dorsal column pathway?
- Ascend to nucleus gracilis and nucleus cuneatus in dorsal root ganglion
- Decussation in medulla
- Ascend through mdial lemniscus to thalamus
- Ascend to somatosensory cortex
How does the sensory information ascend the anterolateral pathway?
- Decussates at gray commisure
- Ascend to thalamus
- Ascend to somatosensory cortex
What are the general features of the somatosensory cortex?
Greatest concentration of receptors/cortical neurons are for feet, hands and lips
- sensory homunculus
- receptor to cortical neuron = 1:1
What is the difference between reflexes and voluntary activity in regards to the motor cortex?
Reflex = don’t need cerebrum
Voluntary Activity = need motor cortex in cerebrum
What are the general features of the motor cortex?
Motor units innervate multiple muscle cells
motor homunculus
motor neuron to motor unit ratio = 1:1
Upper motor neuron leaves cortex
Lower motor neuron leaves spinal cord
Pre motor cortex in front of precentral gyrus creates initial desire to move
What are the direct motor pathways?
Lateral corticospinal tracts
- 90% of UMNs decussate in medulla
- descend contralateral
- synapse on LMNs in spinal cord
Anterior corticospinal tracts
- 10% of UMNs descend ipsilateral
- decussate at gray commissure
- synapse on LMNs in spinal cord
Corticobulbar tracts
-descend to brainstem
-synapse on LMNs for cranial nerves 3-7, 9-12
Which motor pathways work together?
Lateral and anterior corticospinal tracts work together
Corticobulbar tracts are motor component of cranial nerves
What is the indirect, extrapyramidal, motor pathway?
Don’t go thru pyramid of medulla
-separate pathways
