Biopsych Lecture 6

Front 1

What do movement properties tell us about brain mechanisms

Back 1

1) Organized
2) Complex, high level

Can't be replicated in the lab!

Front 2

Parts important to movement in brain

Back 2

Motor cortex (on cerbrum) - affected in strokes

Basal ganglia - affected in parkinsons, hutingtons. Movement not main job

Cerebellum - has many jobs

Spinal cord - no thinking necessary, quick response

Front 3

Spinal cord

Back 3

Where all motor neurons must go through ventral root

Front 4

Two main muscles in arm, how they work together

Back 4

biceps - flexion, agonist muscle
triceps + gravity = extension, antagonist muscle

Acts together like a spring - brain can control stiffness of these springs

Front 5

Movement depends on...

Back 5

relative forces in agonist an antagonist muscles

Front 6

Muscles are based on muscle activation patterns that are either...(2 types of muscle activation)

Back 6

1) Phasic (short) periods of muscle activation to move body part (reaching, walking)

2) Tonic (sustained) muscle activation for posture control (standing, holding)

Front 7

Note

Back 7

Even in phasic periods, you need to sustain posture, balance, etc.

Front 8

Muscle structure

Back 8

Muscle
Muscle fiber (single large cell w/many nuclei)
Myofibril
Sarcomere
Myofilament (Actin or myosin - thick/thin)

Front 9

Know steps of muscle contraction + cross bridge cycle!!

Back 9

See video, covered in phys HW2

Front 10

Muscle length tension relationship

Back 10

Too short = too much overlap = 0 tension

Too long = no overlap = 0 ACTIVE tension, but there is PASSIVE (rubber band/elasticity/stiffness) tension

Total force betwen passive (overap/sarcomere) and active (rubber band concept) increases, dips, then increases again

Front 11

Muscle length velocity force relationship

Back 11

Less strength when you want to move fast because you need more time for molecules to interact **go over slide

Front 12

Name 3 adaptations in the cell that causes widespread activation, contraction in many muscle fibers

Back 12

1) Axons spread over many fibers, another specialization to quickly activate entire unit

2) Motor end plate is very wide/spread out, specialized to affect lots of the fiber rapidly

3) Compound action potentials: Depolarizations in one fiber cause depolarizations in neighboring fibers to produce synchronization

Front 13

Muscle contraction is...

Back 13

synchronized across many bundles of fibers

Front 14

Spinal cord is organized how?

Back 14

so that particular motor neurons have their own territory within the muscle, have own pattern of activity

Front 15

Widespread activation causes

Back 15

contraction in many muscle fibers

Front 16

Muscle contraction is also sychronized across

Back 16

entire muscle itself.

Front 17

EMG can be used to measure

Back 17

compound (synchd) action potentials across the muscle by placing surface electrodes at different locations on it

EMGs are hard to use over single contractions in hands, small digits

Front 18

What might you look for when analyzing an EMG in the lab?

Back 18

When does activity start?
How big is activity?
How does pattern compare to other muscles/other movements?

To study locomotion, studying sets of muscles like in front/back of leg




Note: lab proccesing flips to positive, processes info first

Front 19

Stretch reflex

Back 19

1) Patellar tendon is struck
2) Muscle stretches (attached to tendon, what is this called?)
3) Stretch receptor message travels to muscle spindle in quad muscles
4) Travels to sensory neuron
5) Travels to ventral spinal cord where motor neurons are located
6) Makes monosynaptic (very quick, large axon) contraction w/ extensor motor neuron
7) Also, message flows to inhibitory interneuron, preventing movement of hamstring/flexor muscle

very fast!! Myelinated, large axons
Sensory cells synapse directly onto motoneurons
ionotropic synapses used = fast

Used for orientation, movement, space

Front 20

Proprioception, two main types of proprioception receptors

Back 20

Collection of info about body movements, position, where limbs are; muscle spindles and golgi tendon organs are critical parts of the proprioception system

Front 21

Muscle spindles

Back 21

1) Stretch extrafusal muscle
2) Intrafusal muscle stretches as well, pushed by large EF muscles
3) Spindle stretches, sending signals through primary afferent fiber
4) Involved in stretch reflex (knee)


**brain can control tension on intrafusal cell, influencing sensitivity of receptor

Front 22

Golgi tendon organ

Back 22

Responds to stretch, especially when in "danger zone"

Front 23

Explain what happens to muscle spindles/gogli tendon organ when muscle is:
Relaxed
Stretched
Contracted

Back 23

Relaxed: none activated
Stretched: Both activate
Contracted:
Only tendon organ excited
In spindle, only alpha motor neurons activated and not gamma, causing "slacking"
Not realistic though

Front 24

Gama motor neurons vs alpha motor neurons

Back 24

Nerves that go to intrafusal fibers

Nerves that go to main muscle

Need both to activate spindles - alpha-gamma-coactivation**go over - overall spindle gets shorter but middle part stretched, does not slack - reset spindle sensitivity to new length
GO OVER

Front 25

Stability is achieved by...

Back 25

controlling joint stiffness using proprioception (it is a tonic movement)

Front 26

Primary motor cortex (M1)

Back 26

Located in prefrontal gyrus
Controls individual muscles

Front 27

Basal ganglia

Back 27

Affected in parkinsons
Connects to M1
Has input to striatum (caudate nucleus, putamen) - projects to globus pallidus, thalamus, and M1

Front 28

Effect of parkinsons

Back 28

Substantia nigra cells die (dopamine neurons die)

Increased activity in GPi and STN - cells fire faster than normal

Front 29

Symptoms of parkinsons

Back 29

rigicity
tremors
flexed elbows, wrists
stooped posture
masklike face

Front 30

Deep brain stimulations

Back 30

Implant electrode in subthalamic nucleus, which is attached to pacemaker which continuously sends message to subthalamic nucleus

Front 31

Cerebellum

Back 31

conversation with motor/sensory cortex (doesn't directly control), takes a lot of sensory input,

monitors muscle spindle activity to make corrections/movements

Attuned to local effects, while basal ganglia is slower/modulatory effects

Front 32

Sequence of brain activation

Back 32

1) Response selection - select appropriate response among many, context matters

2) Motor plan - determine appropriate muscle activation pattern

3) Execute the plan - appropriate motor neurons activated in correct time order

Front 33

Feedforward control + preperation for movement

Back 33

depends on internal representation/ anticipatory response

An internal model allows predictions for a motor plan

Front 34

Innervation ratio

Back 34

Number of muscle fibers per motor neuron

Small = more fine movement
Large = coarse movement

Front 35

Topics to go over

Back 35

Functions of brain parts: Basal ganglia, M1, Cerebellum

Alpha-gamma-coactivation

Muscle contraction/crossbridge cycle

Hierarchy!!!