physiology exam 2- movement

smooth muscles

digestive system and other organs

skeletal/striated muscles

control movement of the body in relation to the environment

cardiac muscles

heart muscles with the properties of skeletal and smooth muscles

muscle fibers

each muscle fiber receives information from only one axon, but a single axon may innervate many muscle fibers

neuromuscular junction

synapse between a motor neuron axon and a muscle fiber

acetylcholine

muscle contracts

antagonistic muscles

movement requires the alternating contraction of opposing sets of muscles

flexor

flexes or raises appendage

extensor

extends or straightens appendage

fast twitch

fibers produce fast contractions but fatigue rapidly, anaerobic, do not require oxygen

slow twitch

fibers produce less vigorous contraction without fatigue, aerobic, require oxygen

proprioceptors

receptors that detect the position or movements of a part of the body

muscle spindles

proprioceptors parallel to the muscle that respond to a stretch: cause a contraction of the muscle

stretch reflex

proprioceptors detect the stretch and tension of a muscle and send message to the spinal cord to contract it

golgi tendon organ

• proprioceptor that responds to an increase muscle tension,

• located in the tendons at the opposite ends of the muscle,

• acts as a brake against excessively vigorous contraction by sending an impulse to the spinal cord where motor neurons are inhibited.

reflexes

involuntary, consistent, automatic

ballistic muscles

cannot be changed once initiated

central pattern generators

neural mechanisms in the spinal cord that generate rhythmic patters of motor output

motor program

fixed sequence of movements that is either learned or built into the nervous system. Once begun, the sequence is fixed from beginning to end.

primary motor cortex location

located: precentral gyrus in the frontal lobe → brain steam → spinal cord → generate impulses that control the muscles

primary motor cortex

active when ppl intend a movement

posterior parietal

keeps track of position of the body relative to the world

premotor cortex

active during preparation for movement- organizes the direction of the movement in space

supplementary motor cortex

organizes rapic sequence of movements in a specific order, and active following an error so you can inhibit the incorrect movement next time

prefrontal cortex

active during a delay before movement. Stores sensory information relative to a movement

messages from the brain

must reach the medulla and spinal cord to control the msucles

corticospinal tracts

paths from the cerebral cortex to the spinal cord

lateral corticospinal tract

sex of axons from the primary motor cortex, surrounding areas, and red nucleus in the spinal cord

• controls movement in peripheral areas

red nucleus

midbrain area with output mainly to arm muscles

medial corticospinal tract

set of axons from many parts of the cortex that controls the muscles of the neck, shoulders, and trunk. responsible for bilateral movements

cerebellum

balance and coordination - more neurons than all other brain areas combined

• important for establishment of new motor programs

• vital for attention

basal ganglia

critical for learning motor skills, organizing sequences of movement, “automatic” behaviors, and new habits

Parkinson’s disease

A movement disorder characterized by muscle tremors, rigidity, slow movements, and difficulty initiating physical and mental activity, also depression, memory and reasoning deficits, loss of smell, etc…

immediate cause of parkinson’s

gradual and progressive death of neurons, especially in the substantia nigra

substantia nigra

sends dopamine-releasing axons to caudate nucleus and putamen

loss of dopamine

less stimulation in the motor cortex and slower onset of movements

treatment of parkinson’s

L-dopa is the primary treatment, often ineffective, does not prevent the continued loss of neurons

L-dopa

precursor to dopamine that easily crosses the blood-brain barrier

other possible treatments for parkinson’s

• drugs that directly stim dopamine receptors

• implanting electrodes to stimulate areas deep in the brain

huntington’s disease

neurological disorder characterized by various motor symptoms, gradual and extensive brain damage in the basal ganglia but also in the cerebral cortex

huntington’s disease motor symptoms

arm jerks, facial twitches, tremors and writhing

huntington’s psychological disorders

Depression, memory impairment, anxiety, hallucinations/delusions, poor judgment, alcoholism, drug abuse, sexual disorders

heredity of huntington’s

controleld by an autosomal dominant gene on chromosome #4

• higher the repeats of the combination C-A-G, the more certain and earlier the person is to develop the disease