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Pathways
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50
Anatomy
Undergraduate 1
12/08/2008

Additional Anatomy Flashcards

 


 

Cards

Term
What are the 2 main pathways of the somatosensory system?
Definition

DCML - dorsal column medial lemniscus

spinothalamic tract

Term
Somatosensory information goes to what part of the thalamus?
Definition

VPL - body

VPM - head

Term
What are the receptors of the spinothalamic system?
Definition

nocioceptors - pain

thermoreceptors - temperature

mechanoreceptors - crude touch

Term

what is the periaqueductoral grey?

Definition

Periaqueductal gray (PAG; also called the "central gray") is the midbrain grey matter that is located around the cerebral aqueduct within the midbrain. It plays a role in the descending modulation of pain and in defensive behaviour.

From Wikipedia.

Term
What three types of interneurons provide inhibitory mechanisms for pain?
Definition

substantia gelatinosa

periaqueductal grey-raphe nuclei pathway

spinomesencephalic fibers, hypothalamus or cortex

Term
which pathway is refered to as the tactile pathway?
Definition

DCML

Term

what receptors are part of the DCML?

Definition

cutaneous mechanoreceptors:

touch - Meissner, Merkel, hair

vibration - Pacinian

pressure - Ruffini

 

muscle spindles:

muscles spindle (Ia)

golgi tendon (Ib)

Term
What are the primary somatic sensory afferents of the head?
Definition

from cranial nerve:

V

trigemincal (gasserian) ganglion

mesencephalic nucleus

 

VII

facial (geniculate) ganglion

 

IX

superior ganglion of IX

 

X

superios of X

Term
What are the primary visceral sensory afferents of the head?
Definition

from cranial nerve:

 

VII

geniculate ganglion

 

IX

inferior ganglion of IX

 

X

inferior ganglion of X

Term
What is the spinal trigeminal nucleus?
Definition

The spinal trigeminal nucleus is a nucleus in the medulla that receives information about deep/crude touch, pain, and temperature from the ipsilateral face.

From Wikipedia

spinothalamic homologue.

Term
What are the three distinct regions of the spinal nucleus?
Definition

1. oral nucleus

2. interpolar nucleus

3. caudal nucleus

Term
What is the pathway for pain and temperature from the face?
Definition
primary afferent neurons from face --> synapse of spinal nucleus (e.g. caudal nucleus) --> secondary neurons cross midline --> joins spinothalamic tract --> VPM --> tertiary neurons goto IC --> post central gyrus
Term
What are the two ascending pathways of the trigeminal tract?
Definition

1. medial lemniscus (ventral trigeminothalamic) tract

 

Major

crosses then joins medial lemniscus

 

2. dorsal trigeminothalamic) tract

 

Minor

does not cross

ascends to ipsilateral VPM and post-central gyrus

Term
What are the 4 main connections of the trigeminal nerve?
Definition

1. peripheral branches of the mesecephalic neurons - connect to mesencephalic nucleus

2. tactile afferents - either join the medial lemniscus (ventral trigeminothalamic) or the dorsal trigeminal tract

3. axons of trigeminal motor connect with motor nucleus

4. pain-temperature afferents connect to spinal nucleus (e.g. caudate)

Term
What are the 2 main pathways for the motor sytem?
Definition

lateral corticospinal tract

corticobulbar tract

Term
What are the 4 extrapyramidal tracts?
Definition

vestibulospinal tract - mediate postural adjustments and head movements

 

reticulospinal tract - major alternate route to spinal cord in humans

 

rubrospinal tract - minor alternate route to spinal cord in humans

 

tectospinal tract - eye movements

 

Term
What are the effects of a lesion in lower motor neurons (alpha motor neurons innervating striated muscle)?
Definition
paralysis, eventually muscle atrophy
Term
What are the effects of a lesion in upper motor neurons (alpha motor neurons innervating striated muscle)?
Definition
hyperactive reflex, paralysis or weakness (paresis)
Term
What would result from unilateral corticobulbar damage?
Definition

1. Inability to contract muscle (e.g., contralateral lower face)

2. may have some transient contralateral weakness

3. no asymmetry at all

 

Term
Trace the rubrospinal tract.
Definition
secondary neurons originate in red nucleus --> crosses at same level --> descends lateral part of brainstem tegmentum --> runs down SC along with CST --> synapse in cervical SC
Term
What is the function of the rubrospinal tract?
Definition

minor alternate route to spinal cord

limb movements and posture

tract very small in humans

Term
trace the path of the reticulospinal tract.
Definition
secondary neurons originate in reticular formation --> descends anterior (ipsilateral) or lateral (bilateral) funiculi of spinal cord --> synape in all levels of SC
Term
what is the function of the reticulospinal tract?
Definition

alternate pathway for motor movements (e.g. walk, postural)

 

related to many cerebellar functions and motor control functions

 

autonomic functions (e.g., breathing, heart rate)

Term
trace the path of the lateral and medial vestibulospinal tract.
Definition

secondary neurons originate in the lateral vestibular nuclei --> ipsilateral ventral funiculus --> synapses in all levels of SC

 

secondary neurons originate in the medial vestibular nuclei --> bilateral medial longitudinal fasciculus --> synapses in all levels of SC

 

Term
what is the function of the vestibulospinal tract?
Definition

lateral: postural control (e.g., antigravity muscles)

medial: establishing head when walking, coordinating head with eye movements

Term
trace the tectospinal tract.
Definition
secondary neurons from the superior colliculus --> cross in superior colliculus --> descends contralateral anterior funiculus --> synapses on cervical spind cord.
Term
what is the function of the tectospinal tract?
Definition
eye movements
Term
Where do nerve bodies of motor neurons lie?
Definition
CNS - brain and spinal chord
Term
Where do nerve bodies of sensory neurons lie?
Definition
PNS - in ganglia
Term

What are the functional divisions of the PNS?

Definition

autonomic and somatic

Term
What structures does the autonomic nervous system control?
Definition

cardiac muscle, smooth muscle and glands

Also recieves sensory input from these structures

Term
How many pairs of spinal nerves are there?
Definition

31 pairs

cervical - 8

thoracic - 12

lumbar - 5

sacral -5

coccygeal - 1

Term
What type of neurons do dorsal root ganglia have?
Definition

pseudounipolar cells (there are no synapses within the DRG)

Term

Through what do spinal nerves exit the vertebral canal?

Definition
intervertebral foramen
Term

Spinal nerves are composed of many _?

Definition
fasccicles
Term
Fascicles are composed of many _?
Definition
nerve fibers
Term
What factors affect nerve fiber conduction?
Definition

Myelination 

 

greater diameter/cross-section results in smaller longitudinal resistance --> greater velocity

 

Thicker nerves have a higher membrane capacity which increases resistance, but this effect is outweighed by the smaller longitudinal resistance.

Term
What are modalities?
Definition

A stimulus modality is a type of physical phenomenon that can be sensed.

 

Term
What are the 4 types of sensory receptors?
Definition

1. chemoreceptors, baroreceptors?

2. photoreceptors

3. thermoreceptors

4. mechanoreceptors, baroreceptors

   – nociceptors

Term
What are the two classifications of cutaneous receptors?
Definition
encapsulated and non-encapsulated
Term
Describe the 3 encapsulated mechanoreceptors.
Definition

1. Pacinian corpuscle (vibration)

- subcutaneous all over body

- layers of thin epithelial cells

- rapidly adapting, very sensitive

 

2. Meissner corpuscle (fine touch /discrimination)

- just under epidermis (dermal papillae of hairless   skin); fingertips

- elongated endings, oriented perpendicularly

- a thin outer capsule, layer of stacked Schwann cells inside capsule

- rapidly adapting, fine discrimination

 

3. Ruffini endings (pressure)

- in dermis and subcutaneous and other CT sites

- cigar-shaped capsule

-slowly adapting

Term
Describe the 3 non-encapsulated mechanoreceptors.
Definition

4. endings around hair (touch)

- rapidly adapting

- detects bending of hair

 

5. Merkel endings (touch)

- disc-shaped expansion of terminal of

sensory fibre

- ending is applied to base of Merkel cell

- Merkel cells at basal layer of epidermis

- role is uncertain

- slowly adapting

 

(free endings)

Term

What mechanoreceptors have free endings?

Definition

nociceptors, thermoreceptors and some mechanoreceptors

 

Term
What are the three muscle receptors?
Definition

muscle spindles

golgi tendon organs

free nerve endings

Term
What are the three divisions of the ANS?
Definition

sympathetic

parasympathetic

enteric

Term
What is the NT used preganglionic and post ganglionic PS neurons?
Definition
Ach
Term
What is the NT used preganglionic and post-ganglionic SS neurons?
Definition

preganglionic - Ach

post-ganglionic - norepinepherine

Term
What are the preganglionic PS nerves?
Definition

cranial nerves:

III-Edinger-Westphal

VII-superior salivatory nucleus

IX-inferior salivatory nucleus

X-nucleus ambiguous, dorsal motor nucleus

sacral nerves:

S2-S4

Term
What are the post-ganglionic PS nerves?
Definition

cranial nerves:

III - iris and lens apparatus

VII - lacrimal, nasal, submandibular and sublingual glands

IX - parotid gland

X - heart and other organs

 

sacral nerves:

S2-S4

Term
From what spinal chord regions do preganglionic SS neurons emerge?
Definition
T1-L3
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