kinesiology quiz 2 (muscular and neuromuscular fund part 2)

What is muscle memory?

Not muscle itself, but the brain

Connection between the brain and body

Central nervous system consists of

the brain and spinal cord

Peripheral nervous system consists of

nerves (branch off from spinal cord)

Somatic (voluntary →muscles) and autonomic (involuntary → organs)

What are the parts of the central nervous system?

Cerebral cortex

• The cerebral cortex is the outer layer of the brain that plans, initiates, and consciously controls voluntary muscle movement (specifically in motor cortex)

• The lobes

Basal ganglia

• Deeper part of the brain

• Posture and equilibrium

• Learned movements

• Goes hand in hand with cerebellum→ have a network of connections that give each other feedback

Cerebellum

• Little brain

• Feedback control

• Timing and intensity of muscle movements

Brain stem

• Midbrain, pons, and medulla oblongata

• Integrates all CNS activity, signal has to go through a brain stem to go to the brain (highway)

• Arousal and maintenance of wakeful state (all of our basic functions: heart pressure, heart rate)

Parts of the peripheral nervous system

Everything outside the brain and spinal cord; anything that branches off the spinal cord

Cervical plexus (C1-C4), Brachial plexus (C5-T1), lumbar plexus (L1-L4), Sacral plexus (L4-S4h

Cervical nerves (8 pair), thoracic nerves (12 pair), lumbar nerves (5 pair), sacral nerves (5 pair) coccygeal nerves (1 pair)

Function of cervical nerves

Head movement (rotation, flexion, extension), neck and shoulder movement, upper limb movement

The higher the injury, the more severe outcome because it affects everything under it

Function of thoracic nerves

Rib movement and breathing, verbal column movement, and tone in postural back muscles

function of lumbar nerves

A little hip movement and lower limb movement

Function of sacral and coccygeal nerves

Lower limb movement

Three classifications of neurons

Sensory neurons (Carry senses: smell, taste, touch [pain] ; from body to brain;

Motor neurons (the movement and muscles)

Interneurons (the faster loophole for sensory and motor neuron; sensory neuron goes directly to synapsis at the spinal level for a quick reaction)

What is a neuron?

A nerve cell; basic functional units of nervous system

What are the parts of a neuron?

Dendrites ( receive messages from other cells)

Cell body (the cells life support center)

Axon (passes messages away from the cell body to other neurons, muscle, muscles, or glands)

Myelin sheath (covers the axons and helps for faster nerve impulses)

Nodes of Ranvier (in between each sheath, signal goes even faster because it jumps)

Axon terminal (form junctions with other cells, innervates (connects) the muscle or another neuron)

What is a motor unit

A single motor neuron in all the muscle fibers it innervates (a lot or a little fibers depending of muscle)

Functions as a single unit (all or none → every single muscle fiber the motor unit innervates will contract or none will contract)

Very in size and number (smaller motor unit with less fibers in hand, larger motor unit in leg)

Relationship between the muscle and the nerve it innervates

A particular muscle has a specific nerve that it works with in regards to control of firing (each nerve innervates specific muscle muscles/muscle groups)

Ex) long thoracic nerve and the serratus anterior

What is reciprocal inhibition

Antagonist muscles must relax and lengthen when agonist muscle group contract

Ex) when the bicep contracts in a bicep curl, the tricep must relax

Activation of motor units in agonist causes a reciprocal neural inhibition of motor units in antagonists

This reduction in neural activity of antagonists allow lengthening under less tension

• first to ninth week of training

Factors affect affecting muscle tension development

size of motor unit

Number of muscle fibers per motor unit very significantly within different muscle, muscles and body parts

• Less than 10 inch small muscles (precise movements such as typing or writing from small muscles in hands)

• More than 1000 in large muscle muscles (larger = less control over movement; less complex activities, Ex) quads)

Total number of muscle fibers recruited can be increased by

Activating larger motor units (smaller→ larger)

Activating more motor units

Diagram: Simple twitch- recruiting one more motor unit

Summation- activating more and larger motor units until peak

Tetanus- peak and steady state force; multiple motor units activated and in synch (needed to hold the force and tension)

What is the muscle length- tension relationship

The greatest tension is at resting length (at 100%, optimal, most cross bridges)

Tension is proportional to the number of cross bridges is connected (overlap of myosin and actin)

Too long: cannot overlap and no cross bridges form (passive insufficiency); nothing to pull

Too short: overlap too much and shortening cannot occur (active insufficiency)

What is the muscle force- velocity relationship?

The faster the eccentric (lengthening) motion, the more force

The faster the concentric (shortening) motion, the less force

What is proprioception?

Allows us to know where our body is in space (where things are in relation to our body)

Subconscious mechanism that causes posture and movement

Response to stimuli originating in proprioceptor of the joints, tendons, muscle, muscles, and inner ear (vestibular system)

What is dependent on proprioceptive feedback from muscles and joints?

Quality of movement and reaction to position change

Can proprioception be enhanced?

Yes, through specific training that can improve reaction time and agility

What are the proprioceptors?

Specific to the muscles:

Muscle spindles - detect muscle length

Located in muscle belly and run parallel with fibers

. Ex) when stretching hamstring, the muscle spindles turn on telling hamstrings to contact to prevent tearing

Golgi tendon organs (GTO)- detect muscle tension (or force)

Located in tendon close to muscle tendon junction; where muscle meet tendon

.Ex) If you put too much weight when doing a bicep curl, this receptor will release tension to prevent eruption of tendon

→ protective mechanism

Joint receptor

Kinesthetics receptors:

Ruffini receptors: within joint capsule -stretch, possible mechanical pressure (when pressure is put on joint)

Free nerve endings: connective tissue - physical, touch, pain, mechanical pressure (sense pain and pressure)

Pacinoform Corpuscles: skin, tendon, joint capsules, vibrations (detects vibrations)

How does muscle spindles relate to the stretch reflex

1. Rapid muscle stretch occurs (stimulus)

2. Impulse is sent to CNS (through sensory nerve fiber)

3. CNS activates motor neurons of agonist muscle and causes it to contract (is a protective/defense mechanism; if we did not have the proprioceptors the muscle could tear)

Activate motor neuron to excite

Example and describe the stretch reflex

Ex) knee jerk or patella tendon reflex (test for healthy reflex, stimulates stretch, reflex)

Reflex hammer strikes patella tendon

Causes a quick stretch of quadricep (stimulus for quad)

Then activates the muscle spindle (sends signal to sensory neruron)

. 2 options: Can either go to brain or synapse on a interneuron within the spinal cord which will send a quick response through the motor neuron out the spinal nerve to the innervation if the quad (happens in a reflex)

In response, what is that the fires and the knee extends

More on the tap, more significant the reflexive contraction

More depth on Goldi tendon organ

Tension increasing as the muscle contracts activates GTO

1. GTO stretch threshold is reached (when we get to a certain tension because of a certain amount of stretch)

2. Impulse is sent to CNS

3. CNS causes agonist muscle to relax and activates antagonist as a protective mechanism

Ex) when the bicep has too much weight on it during a curl, the bicep relaxes and the tricep activates to protect it

→ GTO’s protect us from excessive tension

→ Muscle contraction stretches Golgi tendon organ

From image: sends signal from GTO through sensory neurons into spinal cord and synapse on interneuron. Then it will synapse of the alpha motor neuron to inhibit (relax)

Why is it important to have proprioreceptors?

It decreases the amount time for our brain to process what is happening in our body

Reflxes

Reflexes will protect us from harm and damage to the body

→ These signals dont have to go to brain, be processed and be sent down→ it can happen locally at synapses at interneurons in the spinal cord

→ Quickest reflexes in the body are the eyes because the higher up and smaller the muscle the faster the reflexes