KIN 3513 topic 4

neuromotor basis for motor control

neuron

basic component of the nervous system; nerve cell

dendrites

extensions from the cell body that receive information from other neurons

axon

one per neuron; carries electrical signals away from the cell body to other cells

myelin

cellular membrane that speeds up the transmission of neural signals along the axon

synapse

junction between the axon of a neuron and another neuron

sensory neurons (afferent)

send neural impluses to the CNS from sensory receptors

motor neurons (efferent)

send neural impluses from the CNS to the muscles and glands

alpha motor neurons

found mainly in the spinal cord; have long branching axons that connect directly with the skeletal muscle fibers

gamma motor neurons

located in the spinal cord; controls the sensitivity of muscle spindles by innervating intrafusal muscle fibers

interneurons

originate and terminate in the brain or spinal cord and function as connections between [axons descending from the brain and synapse on motor neurons] and [axons from sensory nerves and spinal nerves ascending to the brain]

central nervous system (CNS)

cerebrum, diencephalon, cerebellum, brainstem

cerebrum

right and left cerebral hemispheres connected by the corpus callosum that are covered by the cerebral cortex and responsible for higher-level functions like thinking, voluntary movement, language, and sensory processing

cerebral cortex

the wrinkled, outermost layer of grey matter of the brain that handles high-level thinking, language, memory, and sensory processing; frontal, parietal, occipital, and temporal lobes

sensory cortex

located posterior to the central sulcus; specific types of sensory information are transmitted via sensory nerves to the area of the cortex that receives that type of information

primary motor cortex (cerebral cortex)

frontal lobe, just anterior to central sulcus that contains motor neurons that send axons to specific skeletal muscles throughout the body; critical for movement initiation and the coordination for fine motor skills

premotor area (cerebral cortex)

controls the organization of movements before they are initiated and rhythmic coordination during movement; enables transitions between sequential movements of a serial motor skill (ex: typing, piano playing)

supplementary motor area (cerebral cortex)

plays a role in the control of sequential movements and preparation/ organization of movement; located medial surface of the frontal lobe

parietal lobe

interacts with the premotor cortex, primary motor cortex, and SMA before and during movement

basal ganglia

plays important role in planning and initiation of movement and control of antagonist muscles during movement

parkinson’s disease

common disease associated with dysfunctionof the basal ganglia; lack of dopamine production, slow movements, rigidity of muscles, tremor

thalamus

receives and integrates sensory info from the spinal cord and brainstem; passes them through the cerebral cortex

hypothalamus

critical brain center for the control of the endocrine system and the regulation of body homeostasis

the cerebellum

sensory neural pathways into __ _____ arise from the 3 principle regions; the spinal cord, cerebral cortex, and brainstem

cerebellum functions

control of smooth and accurate movements and serves as a type of movement error detection and correction system; control of hand-eye coordination, movement timing, force control, and posture control

pons

involved in control of various body functions and balance (ex: chewing)

medulla

regulatory center for internal physiologic processes (ex: breathing)

reticular formation

integrator of sensory and motor neural impulses

gray metter

H-shaped central portion of the cord consisting of cell bodies and axons of neurons that have 2 “horns”

dorsal (posterior) horns of gray matter

cells transmit sensory information

ventral (anterior) horns of gray matter

contains alpha motor neuron cell bodies whose axons terminate on skeletal muscles

sensory neural pathways

ascending tracts; pass through spinal cord and brainstem; dorsal column and anterolateral system

motor neural pathways

descending tracts; descend from brain through spinal cord; pyramidal and extrapyramidal tracts

all or none principle

when an alpha motor neuron fires, all its connected muscle fibers contract