the sensorimotor system Flashcards
what is motor control?
regulation of movement. conscious and unconscious regulation of muscle force. complex sensory feedback system involved.
what are the different types of motor control?
- voluntary: running/walking/talking
- goal directed: conscious, explicit, controlled
- habit: unconscious, implicit, automatic
- involuntary (no control): eye movements, facial expressions, diaphragm, cardiac
what is the vestibular system?
a sensory system that is responsible for providing our brain with information about motion, head position, and spatial orientation
-helps us keep balance
description of sensorimotor system
- hierarchial
- motor control by lower (cell body that projects from brainstem/spinal cord to muscle) and upper motor neurons (higher centres e.g. brain and project to meet lower at spine)
- descending control system with ascending feedback from sensory systems, basal ganglia and cerebellum
muscles
- contract/relax
- cardiac, smooth and skeletal
- activation of muscle fibres is all or none
- antagonistic arrangement
how do muscles contract?
when muscle contracts, myosin heads move across actin and form myosin cross-bridges
-atp (produced by oxidative metabolism) provides energy for bond to be broken
purpose of ATP and rigor mortis
without ATP due to no oxygen (death), myosin molecules stay bound to actin filaments and the muscles become rigid (stay contracted)
-calcium released from packets inside of muscle cells causes rigor mortis
slow twitch muscle fibres
can combine lots of force and sustain over a long period of time e.g. posture
fast fatigue resistant muscle fibres
cannot sustain force for long period of time - will tire e.g. jogging, running
fast fatigable muscle fibres
sustain force for very short period of time e.g. jumping, fast movements
the motor unit
a motor unit = single alpha motor neuron + muscle fibres that it innervates
- fewer fibres means greater movement resolution e.g. finger tips/tongue
- more motor neurons –> more fibres contract –> greater power
what is a motor pool?
- all the lower alpha motor neurons that activate a muscle
- different number of motor pools for different muscle fibres
what senses tension/force?
golgi tendon organs
- where the muscle joins the bone
- sends ascending sensory info to brain via spinal cord about how much force there is in the muscle
- under extreme tension–>they inhibit muscle fibres to prevent damage
what senses length (amount of stretch on the muscle)?
muscle spindles
reflex circuit
- extrafusal muscle fibres give force
- intrafusal muscle fibres (have muscle spindles wrapped around them) sense stretch - innovated by separate motor neuron –> gamma motor neurons
what is reciprocal innervation?
- antagonistic muscles, contraction of one and relaxation of another
- allows smooth movements
why do cats always land on their feet?
- righting reflex/vestibular system detects body isn’t upright and gravity
- info integrated from visual, somatosensory and proprioceptive sensory input
- cerebellum important
what are brainstem structures?
- pathways and nuclei within brainstem connect sensory input to motor output in direct ways
- old (cortex is new bit)
primary motor cortex
exerts direct top down control over muscular activity with as few as one synapse in spine between cortical neuron and innervation of muscle cells
-has direct affect on lower motor neurons
basal ganglia and cerebellum role in motor control
- basal ganglia sends inhibitory signals to motor cortex
- cerebellum sends excitatory signals to motor cortex
what is the homunculus?
representation of body parts in relation to sensory/motor function
-it is an oversimplification because if you damage part of finger it doesn’t mean you lose control over all of it
dorsolateral tracts
- innervate contralateral side of one segment of spinal cord
- sometimes project directly to alpha motor neuron
- project to distal muscles e.g. fingers
ventromedial tracts
- diffuse innervation projecting to both sides and multiple segments of spinal cord
- project to proximal muscles of trunk and limbs
