Special senses-general senses

what are some examples of general senses?

cold, hot, touch, pressure, pain

what is a sensory projection pathway?

a route by which sensory signals are sent from receptors to specific part of the cerebral cortex

How many neurons are involved in most somatic sensory pathways?

Three neurons

1. first-order

2. second-order

3. third-order

what does the first-order neuron do?

carries signals from the sensory receptor to the spinal cord or brainstem

which fibers are fast in 1st-order neurons: touch or temperature?

Touch, pressure, and proprioception are fast because they are large and myelinated. Unlike temp fibers, they are small and unmyelinated meaning they are slower

what does the second neuron do?

carries the signal from the spinal cord to the thalamus (or cerebellum for proprioception)

where does decussation (crossing sides) occur in the pathway?

In the spinal cord, medulla, or pons (usually with the second-order neurons)

What tract is responsible for carrying pain to the brain?

spinothalamic tract

what does the third-order neuron do?

carries signals from the thalamus to the cerebral cortex

where in the brain do most sensory signals end?

primary somatosensory cortex

what is the primary somatosensory cortex and what does it do?

It is a region in the parietal lobe (postcentral gyrus) that receives and interprets sensory information from the body like touch, pressure, pain, and body position.

what type of sensory information does the spinothalamic tract carry?

pain, temp, crude touch, and itch/tickle

where does the spinothalamic tract cross to the opposite side of the body?

the Spinal cord

what neuron is the spinothalamic tract part of?

2nd-order neuron (spinal cord—> thalamus)

where does the spinothalamic tract end?

in the thalamus (b4 the 3rd order neuron carries it to the cortex)

what is pain?

an unpleasant perception of actual or potential tissue damage

what are the two categories of pain?

Nociceptive pain and neuropathic pain

what is nociceptive pain?

pain caused by injury to body tissues; includes visceral, deep somatic, and superficial somatic pain

what is visceral pain and what does it feel like?

pain from internal organs; feels dull crampy, and hard to localize

what is deep somatic pain and what does it feel like?

Pain from bones, joints, and muscles; feels deep and aching (e.g. fractures and sprains)

what is superficial somatic pain and what does is feel like?

pain from the skin: feels sharp or burning (e.g. cuts, burns)

what is neuropathic pain?

pain caused by damage to nerves, spinal cord, or brain (nervous system as a whole); often described as burning, stabbing, or shooting

pain signals from head travel to brainstem via?

cranial nerves

what cranial nerves carry pain signals from the head?

cranial nerves: 5(trigeminal), 7 (facial), 9 (glossopharyngeal), and 10 (vagus)

The first order neurons for pain in the head travel from where to where?

in the cranial nerves and end in the medulla

where do the 1st-order pain neurons from the head end?

in the medulla

where do the 2nd order pain neurons i the head start and go?

in the medulla and ascend to the thalamus

where do the 3rd-order pain neurons in the head start and go?

from the thalamus and reach cerebral cortex

pain signals from the neck and below travel through what?

3 ascending tracts

which three ascending tracts are involved with the pain signals from the neck and below?

1. spinothalamic tract

2. spinoreticular tract

3. gracile fasciculus

what is the function of the spinothalamic tract?

carries raw, conscious feeling of somatic pain to the thalamus and cortex

what is the spinoreticular tract and what does it do?

it carries pain to the reticular formation and connects to the hypothalamus and limbic system; its involved in emotional and associative pain processing

what is the function of the gracile fasciculus in pain projection?

it carries visceral pain signals (from organs) to the thalamus

which pain tract is primarily involved in emotional response to pain?

spinoreticular tract

what part of the brain processes emotional and associative aspects of pain?

Hypothalamus and limbic system

what is referred pain?

visceral pain that is perceived as coming from a superficial or somatic location due to shared neural pathways in the CNS

why does referred pain happen?

because visceral and somatic sensory neurons converge onto the same neural pathways ways in the spinal cord, and the brain cannot distinguish the true source of the pain

what is an example of referred pain from the heart?

pain felt in the left arm, chest, or jaw

where is pain from the diaphragm or lungs often referred to?

the shoulder or neck

what part of the brain gets “confused” in referred pain?

the cerebral cortex because of mixed signals from the spinal cord

true or false: In CNS modulation of pain, pain is subjective, highly variable, and influenced by physical and mental state.

True

True or false: CNS does not have analgesic mechanisms

False

analgesic

pain-relieving

what is a neuromodulator?

a chemical that changes the strength or likelihood of a nerve signal rather than sending a direct message or influencing the activity of neurotransmitters and receptors.

what are endogenous opioids?

Natural pain-relieving peptides made by the body, like endorphins, enkephalins, and dynorphins

where does spinal gating of pain occur?

in the posterior horn of the spinal cord

what do enkephalins do in spinal gating?

They inhibit 2nd-order pain neurons, reducing or blocking the pain signal

what are examples of endogenous opioids?

Enkephalins, endorphins, and dynorphins

what is spinal gating?

a mechanism where interneurons release opioids to block pain signals before they reach the brain.

opioids block pain through what mechanism?

through spinal gating

what is the function of the spinothalamic tract?

it carries most concious somatic pain signals to the thalamus

what are the two spinal gating methods that reduce pain?

1. inhibit the second-order neuron from firing

2. inhibit the first-order neuron from releasing neurotransmitter.

which part of the brain receives the pain signal after the thalamus?

The cerebral cortex

which areas help modulate pain by sending signals back down to the spinal cord?

the midbrain, medulla oblongata, and hypothalamus

what is the role of the reticulospinal tract in pain modulation?

it carries descending inhibitory signals from the medulla to the spinal cord to block pain

what are enkephalins and what do they do?

they are endogenous opioids that block pain by inhibiting pain neurons in the spinal cord

which tract carries descending inhibitory pain signals from the brain?

the reticulospinal tract (descending)

which tract carries concious somatic pain to the brain?

Spinothalamic tract (ascending)

what type of pain does the spinothalamic tract carry?

Raw, conscious pain —especially pain and temperature

which tract is involved in spinal gating to block pain?

reticulospinal tract

which tract carries signals from the medulla to the spinal cord to trigger enkephalin release?

reticulospinal tract

which tract would be most active when you are conciously aware of stepping on a tack?

spinothalamic

which tract helps reduce pain perception through descending inhibition?

reticulospinal

true or false: the reticulospinal tract is part of the ascending pain pathway

False—its part of the descending modulation pathway

true or false: the spinothalamic tract transmits signals involved in spinal gating.

False—it transmits the pain signal up, not blocks it