Chapter 3D Flashcards
The tactile sensations include PITTV
pressure, itch, tickle, touch, vibration
Cold thermoreceptors: activated by temperatures between 10 and 35°C.
* Warm thermoreceptors: activated by temperatures between 30 and 45°C. Less
abundant that cold receptors
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What does the free nerve ending sense?
PIT CW
pain, itch, tickle, cold or warmth
2 types of pain:
fast
slow
characteristics?
. Fast pain:
within 0.1 sec, acute, sharp, or pricking , not felt in deeper layers
- Slow pain:
second or more, chronic, burning,
aching, or throbbing pain. can occur everywhere
Superficial somatic pain: results from receptors on …
the skin
Deep somatic pain: results from stimulation of receptors in …
skeletal muscles, joints,
tendons, and fascia.
Visceral pain: results from stimulation of nociceptors in …
visceral organs.
x allow us to recognize that parts of our
body belong to us (self).
* Kinesthesia is the perception of body movements.
proprioception
There are three types of proprioceptors in the musculoskeletal system
Muscle spindles
tendon organs
Joint kinesthetic receptors
what do they do
Muscle spindles:
monitor changes in the length of skeletal
muscles, stretch reflexes
Tendon organs: at junction of a tendon, changes in muscle tension
- Joint kinesthetic receptors: at Joint ligaments, adjust reflex inhibition of muscles when excessive strain
is on the joint
SO FAR, WE HAVE STUDIED THE SENSATIONS AND THEIR
RECEPTORS, BUT WHERE DOES THE INFORMATION
REACH THE BRAIN?
(primary somatosensory area )of the cerebral cortex (about the middle of the brain)
cerebellum (which looks like the small brain)
First-order (primary) neurons are sensory neurons that conduct impulses from
…. receptors into …
somatic sensory
the brainstem or spinal cord
Second-order (secondary) neurons conduct impulses from the …. to the …
brainstem or spinal
cord
thalamus (center of brain)
Third-order (tertiary) neurons conduct impulses from the …. to the ….. on the same side. As the impulses reach the primary
somatosensory area, perception of the sensation occurs.
thalamus
primary
somatosensory area
What does decussate mean?
cross over to the other side of the brain
Because the axons of …
neurons decussate as they pass through
the brainstem or spinal cord, somatic
sensory information on one side of the
body is perceived by the primary
somatosensory area on the opposite
side of the brain.
second-order
What is Sensory homunculus ?
it maps sensory signals from
the left side of the body in the somatosensory
area of the right cerebral hemisphere
The relative sizes of these regions in the
somatosensory area are proportional to the
number of specialized sensory receptors within
the corresponding part of the body
Cerebellum receives most of proprioceptive impulses
true/false
true
Somatic sensory impulses reach the cerebellum via two spinocerebellar tracts:
- anterior spinocerebellar tract
- posterior spinocerebellar tract
- Although they are not consciously perceived, sensory impulses conveyed to the
cerebellum along these two path ways are critical for…
posture, balance, and
coordination of skilled movements.
SUMMARY: what you should know
Somatic sensory (somatosensory) pathways relay information from somatic sensory
receptors to:
1. The primary somatosensory area in the cerebral cortex through first-, secondand thrid-order neurons:
* First: from somatic sensory receptors into the brainstem or spinal cord.
* Second: from the brainstem or spinal cord to the thalamus (relay center).
* Third: from the thalamus to the primary somatosensory area
Localization of somatic sensations occurs when nerve impulses arrive at the
primary somatosensory area.
Each region in this area receives sensory input from a different part of the
body
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SUMMARY: what you should know
- The cerebellum receives most of proprioceptive impulses: critical for posture,
balance, and coordination of skilled movements.
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SUMMARY
The somatic nervous system consists of somatic motor neurons that innervate the
skeletal muscles of the body.
* When a somatic motor neuron stimulates a skeletal muscle, it contracts; the effect is
always excitation.
* If somatic motor neurons cease to stimulate a skeletal muscle, the result is a paralyzed,
limp muscle that has no muscle tone.
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SUMMARY
The somatic nervous system usually operates under voluntary (conscious) control.
Voluntary control of movement involves motor areas of the cerebral cortex that activate
somatic motor neurons whenever you have a desire to move.
* Exceptions: somatic motor neurons that innervate skeletal muscles involved in posture,
balance, breathing, and somatic reflexes (such as the flexor reflex) are involuntarily.
* The somatic nervous system can also receive sensory input from sensory neurons that
convey information for somatic senses (tactile, thermal, pain, and proprioceptive
sensations) or the special senses (sight, hearing, taste, smell, and equilibrium).
* All of these sensations normally are consciously perceived. In response to this sensory
information, somatic motor neurons cause the appropriate skeletal muscles of the body
to contract.
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….. in the brain and spinal cord orchestrate all voluntary movements
neural circuits
Ultimately, all excitatory and inhibitory signals that control movement converge on the
…… that extend out of the brainstem and spinal cord to innervate
skeletal muscles in the body
lower motor neurons
These neurons are known as lower motor neurons (LMNs) because ….
they have their cell
bodies in the lower parts of the CNS (brainstem and spinal cord):
From the brainstem, axons of LMNs extend through ….. nerves to innervate
skeletal muscles of the face and head.
* From the spinal cord, axons of LMNs extend through …. nerves to innervate
skeletal muscles of the limbs and trunk.
cranial nerves
spinal nerves
Lower motor neurons provide output from the CNS to skeletal muscle fibers. For
this reason, they are also called the …. pathway
final common
Axon of a single, myelinated somatic lower motor neuron extends from the CNS
all the way to the skeletal muscle fibers in its motor unit.
* Somatic nervous system stimulation always excites its effectors (skeletal muscle
fibers).
* Somatic motor neurons release only ….
acetylcholine
Neurons in four distinct but highly interactive
neural circuits participate in control of movement
by providing input to lower motor neurons:
- Local circuit neurons in brainstem and
spinal cord - Upper motor neurons from cerebral
cortex (pyramidal pathway) and
brainstem (extrapyramidal pathway) - Basal nuclei neurons
- Cerebellar neurons
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…… area: the idea or desire to move a part of the body is generated and
the information is processed and sent to the premotor area where a motor
plan is developed.
* …. cortex: is the major control region for the execution of
voluntary movements. Electrical stimulation of any point in the primary motor
area causes contraction of specific muscles on the opposite side of the body.
Premotor
Primary motor
What is the motor homunculus
This distorted muscle map of the body is
called the motor homunculus
control of movement by the cerebral cortex:
X cells of the primary motor area of the cerebral cortex extend their
axons to directly provide input to lower motor neurons.
* The direct motor pathways consist of two pathways:
- corticobulbar pathway: conducts impulses for
the control of skeletal muscles [where?].
Some of the axons of the corticobulbar tract
decussate; others do not. - corticospinal pathways: conduct impulses for the
control of muscles of [where?].
X Pyramidal
[in the head]
[the limbs and trunk]
Which of the following motor neurons fits this description?
Originate in cerebral cortex (next, we will see that others upper motor neurons originate at
brainstem).
* Synapses with a lower motor neuron farther down in the CNS (brainstem or spinal cord).
* Control the lower motor neurons: nerve action potential to occur in the axon of the upper
motor neuron, followed by neurotransmitter release generates a graded potential in a lower
motor neuron.
Upper motor neuron in SNS (pyramidal pathway)
Lower motor neuron in SNS (pyramidal pathway):
upper motor neuron
Which of the following motor neurons fits this description?
Originate in brainstem (cranial nerves ) or spinal cord (spinal nerves).
* Inervate muscle directly.
* Are under the influence of upper motor neurons: the graded potential triggers the formation
of a nerve action potential and then release of the neurotransmitter at neuromuscular
junctions (Chapter 4).
Upper motor neuron in SNS (pyramidal pathway)
Lower motor neuron in SNS (pyramidal pathway):
Lower motor neuron
Lower motor neuron in SNS:
The axons of motor neurons are non-myelinated/myelinated and have small/large diameters for fast/slow conduction
of action potentials.
* Always/not always excites its effectors (skeletal muscle fibers).
* Release only acetylcholine/more than only acetylcholine.
- myelinated
- large
- fast
- always
- only acetylcholine
CONTROL OF MOVEMENT BY THE CEREBRAL CORTEX:
SUMMARY
Voluntary movements are conveyed through the pyramidal tract, which arises
from the pyramidal cell in the primary motor cortex.
* The pyramidal system is a two neuron system consisting of upper motor
neurons in the primary motor cortex and lower motor neurons.
* Pyramidal tract divides into the corticospinal tract, which synapses with the
lower motor neurons innervating the muscles in the limbs and trunk, and the
corticobulbar tract, which synapses with the cranial nerves to control muscular
movements of the face, head, and neck.
* Damage to the pyramidal tract result in spastic paralysis
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The pyramidal system provides voluntary control of all our muscular movements, but
very roughly.
* ….pathway refines the ”raw” movements provided by the pyramidal
system and control involuntary movements.
Extrapyramidal
The extrapyramidal system accompanies the pyramidal, but also acts on its own.
true/false
true
- Automations and involuntary movements are included in the extrapyramidal
pathways.
true/false
true
- The extrapyramidal is not connected to the limbic system (emotions).
true/false
false
- In addition to the extrapyramidal pathway (motor centers in the brainstem), only one
pathway contributes to the movement by affecting upper motor neurons: basal
nuclei, cerebellum etc.
true/false
multiple
CONTROL OF MOVEMENT BY THE BRAINSTEM:
INDIRECT OR EXTRAPYRAMIDAL PATHWAY
* This pathway includes all/some somatic motor tracts other than the pyramidal tracts.
* Motor centers in the brainstem convey action potentials to upper/lower motor neurons to
cause involuntary/voluntary movements that regulate posture, balance, muscle tone, and
reflexive movements of the head and trunk.
all
lower
involuntary
