MMED1005 Lecture Notes - Lecture 9: Basal Ganglia, Cerebral Cortex, Nociceptor
7 Jun 2018
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The CNS and everyday life:
Control of movement and position
Main points:
- Negative feedback control as a way of maintaining constant values for physiological
variables
- Movement as the coordinated actions of many muscles to change the position of
parts of the body
- The monosynaptic stretch reflex as a control system for limb position
- The Golgi tendon organ reflex as a control system for muscle force
- The flexor withdrawal reflex as a protective mechanism
Control of movement:
Body movement involves putting and maintaining the parts of the body in a particular
position.
It involves:
- Conscious decisions to change position
- Conscious decisions to do something that changes position
o E.g. stand up
o Play this tune on the violin
- Unconscious adaptations to maintain position
o E.g. remain standing up, even when someone bumps into you
Terminology:
Movement of limbs are often classed as flexion or extension.
Flexion bends the limb (decreases the joint angle)
Extension straightens the limb (increases the joint angle)
Movements are usually brought about by groups of muscles working together. They are
referred to as synergists. Muscles which perform the opposite action are their antagonists.
find more resources at oneclass.com
find more resources at oneclass.com
Control systems:
- Often mentioned in physiology, usually as egatie feedak otol sstes for
homeostasis.
- They are a strategy for keeping things constant
Control of movement involves negative feedback control. For control of
limb position there are several loops acting at once, but for the main one
the components are:
- Receptor: (something called a usle spidle), sense muscle length
- Afferent pathway: via dorsal roots
- Integrating centre: in CNS (spinal cord)
- Efferent pathway: via ventral roots
- Effector: skeletal muscle groups
Muscle spindle:
- A group of small modified muscle fibres around their central region
- When the spindle is lengthened (stretched), firing rate in the
sensory nerve increases
- Every muscle contains dozens of muscle spindles
- The muscle spindle output goes to the spinal cord via the dorsal
root, and makes an excitatory connection with the alpha
motoneurons of the muscle that contains the spindle
- Alpha motoneurons are the cells in the spinal cord that
drive the skeletal muscles
- The muscle spindles also connect, via chains of
interneurons in the spinal cord, to the alpha motoneurons
of antagonist muscles
- The effects is inhibitory, reducing drive to the antagonists
as the spidles o usle otats
- *(note that books tend to show a single inhibitory
interneuron as above, but there are actually several in a
chain)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Negative feedback control as a way of maintaining constant values for physiological variables. Movement as the coordinated actions of many muscles to change the position of parts of the body. The monosynaptic stretch reflex as a control system for limb position. The golgi tendon organ reflex as a control system for muscle force. The flexor withdrawal reflex as a protective mechanism. Body movement involves putting and maintaining the parts of the body in a particular position. Conscious decisions to do something that changes position: e. g. stand up, play this tune on the violin. Unconscious adaptations to maintain position: e. g. remain standing up, even when someone bumps into you. Movement of limbs are often classed as flexion or extension. Flexion bends the limb (decreases the joint angle) Extension straightens the limb (increases the joint angle) Movements are usually brought about by groups of muscles working together. Muscles which perform the opposite action are their antagonists.
