Neural control of movements (Week 3)

Central Nervous System (CNS)

The component of the nervous system consisting of the brain and spinal cord where all decisions are made.

Peripheral Nervous System (PNS)

The nervous system components attached to the CNS that act as communication lines and receptors to send signals.

Cerebral Hemisphere

The two symmetrical halves of the brain.

Hypothalamus

The part of the brain in charge of the cardiovascular system.

Cerebellum

The part of the brain in charge of our balance and movement systems.

Brainstem

Also known as the Pons and Medulla, it is in charge of our respiratory system.

Autonomic Nervous System

An involuntary system that occurs automatically involving smooth muscle, glands, and cardiac muscles.

Sympathetic Nervous System

A branch of the autonomic system responsible for the fight or flight response, increased breathing, and heart rate during exercise.

Parasympathetic Nervous System

A branch of the autonomic system active at rest, responsible for digestion and slowing down the heart rate.

Somatic Nervous System

Part of the nervous system that handles skeletal muscle, voluntary movements, sensory processing, and reflex arcs.

Cell Body

The core part of the nerve that contains the nucleus.

Nucleus

The relay station for information within the nerve cell.

Dendrites

Structures that send signals towards the nerve cell body.

Axon Hillock

The part of the neuron that triggers the signal.

Axon

A wire connection that generates the electrical signal.

Schwann Cell

Cells that wrap around the axon to help increase signal speed by preventing signals from escaping.

Node of Ranvier

Gaps between the Schwann cells where the electrical action potential signals occur.

Myelin Sheath

A protective fatty protein layer that wraps around axons to speed up reactions.

Reflex Arc

A rapid, involuntary, and automatic response involving a direct route from a receptor to a sensory neuron, interneuron, motor neuron, and effector.

Resting membrane potential

The electrical potential of a neuron at rest, typically at $-70\,mV$.

Threshold

The critical level to which a membrane potential must be depolarized to initiate an action potential, noted at $-55\,mV$.

Depolarization

The phase of an action potential where $Na^+$ enters the cell and membrane potential reaches approximately $+30\,mV$.

Repolarization

The phase of an action potential where $K^+$ leaves the cell.

Motor unit

The combination of a motor neuron and the muscle fibres it attaches to.

Recruitment

Increasing the number of motor units activated to increase force generation.

Rate of coding

Increasing the frequency of motor unit activation to increase force generation.

Flexion

Movement where the angle of a joint gets smaller.

Extension

Movement returning a joint to the starting position.

Adduction

Movement returning a limb back to the starting position, specifically for shoulder and hip joints.

Abduction

Movement moving a limb away from the starting position, specifically for shoulder and hip joints.

Circumduction

A circular motion combining flexion, extension, adduction, and abduction.

Dorsiflexion

Foot movement where the toes point up to the sky.

Plantarflexion

Foot movement where the toes point down towards the ground.

Supination

Hand position where the palms are facing up, similar to holding a bowl of soup.

Pronation

Hand position where the palms are facing down.

Inversion

Ankle movement where the big toe points up to the sky and the ankle rolls in.

Eversion

Ankle movement where the big toe points down to the ground and the ankle rolls out.

Opposition

Specific hand movement where the tip of a finger touches the tip of the thumb.

Motor unit

A motor neuron and all the muscle fibres it innervates.

Recruitment

The neural control of force involving the number of activated motor units; more or bigger units are switched on if more force is needed.

Rate coding

Also known as frequency of motor unit activation or firing; one of the primary methods for neural control of force.

Cycling cross-bridges

The ultimate factor to which all neural control of force is related, based on the total number activated.

Fused (complete) tetanus

A sustained maximal contraction where no relaxation occurs after each stimulus.

Isotonic contractions

Dynamic contractions that include both concentric and eccentric types.

Concentric contraction

A dynamic contraction where force develops as the muscle shortens.

Eccentric contraction

A dynamic contraction where force develops as the muscle lengthens.

Isometric (static) contraction

A contraction where force in the muscle increases but the muscle is unable to shorten.

Fascicle

A bundle of muscle fibres within a whole muscle.

Muscle fibre

A muscle cell, categorized as either fast-twitch or slow-twitch.

Myofilaments

The structural components of myofibrils, consisting specifically of Actin and Myosin.

Flexion

A type of body movement often involving the bending of a joint.

Extension

A type of body movement often involving the straightening of a joint.

Abduction

A body movement that involves moving a limb away from the midline of the body.

Adduction

A body movement that involves moving a limb toward the midline of the body.

Circumduction

A body movement involving a circular motion of a limb.

Dorsiflexion

A special movement of the ankle where the foot moves toward the shin.

Plantar flexion

A special movement of the ankle where the foot moves downward, away from the shin.

Inversion

A special movement where the sole of the foot turns medially.

Eversion

A special movement where the sole of the foot turns laterally.

Supination

A special movement of the forearm where the palm is turned upwards.

Pronation

A special movement of the forearm where the palm is turned downwards.

Opposition

A special movement involving the thumb and other fingers.

Peak tetanic force

A measurement used in force-frequency relationships, represented as a value up to $100\,\%$ in control and fatigued muscle.

EDL

A muscle type (Extensor Digitorum Longus) shown in force-frequency relationship graphs with frequencies up to $120\,Hz$.

Soleus

A muscle type shown in force-frequency relationship graphs with frequencies measured up to $200\,Hz$.

Central Nervous System (CNS)

The division of the nervous system consisting of the brain and spinal cord, acting as integration and control centres.

Peripheral Nervous System (PNS)

Nerves that extend from the CNS which act as communication lines and sensory receptors.

Sympathetic NS

The division of the Autonomic Nervous System responsible for the "fight or flight" response.

Parasympathetic NS

The division of the Autonomic Nervous System involved in "resting, digesting" and visceral functions.

Schwann cells

Cells that produce myelin sheaths in a jelly-roll like fashion to cover nerve axons.

Nodes of Ranvier

The gaps in the myelin sheath along the length of an axon.

Synaptic cleft

The physical gap between adjacent neurons.

Synapse

The junction between two neurons where signals are transmitted.

Reflex

Rapid, predictable, and involuntary responses to stimuli.

Reflex arc

The direct route of an impulse from a receptor, to a sensory neuron, to an interneuron, to a motor neuron, and finally to an effector.

Resting Membrane Potential

The inactive state of a cell where the inside is more negative than the outside, with $K^+$ as the major internal positive ion and $Na^+$ as the major external positive ion.

Depolarisation

The process where adequate stimulation causes $Na^+$ channels to open and $Na^+$ to diffuse into the cell, making the inside more positive.

Repolarisation

The phase where $K^+$ channels open with a delay, allowing $K^+$ to diffuse out of the cell.

Saltatory Conduction

The propagation of an action potential along a myelinated axon.

Axonal terminal

The end of an axon containing vesicles filled with neurotransmitters.