Comprehensive section

Question 1

Be able to Describe in detail how/ when an action potential (AP) is generated.

Answer 1

Action Potential is generated when the membrane potential reaches a threshold.
1. resting potential- maintained by Na+/K+ pump
2. Depolarization phase- voltage-gated Na+ channels open;
3. Repolarization Phase- voltage-gated K+ channels open; Na+ channels close
4. Undershoot- Voltage-gated, K+ channels close, K+ diffuses across the membrane ( Conc. Gradient)

Question 2

Be able to describe Spatial summation and Temporal summation of PSPs and their role in AP generation

Answer 2

Spatial Summation- ( multiple neurons firing at the same time) when multiple postsynaptic potentials from different synapses arrive at the axon hillock simultaneously.

Temporal Summation- ( single neuron firing at a time) when multiple PSPs from the same synapse arrive at the axon hillock rapidly.

If they reach the threshold, an AP is generated

Question 3

Describe saltatory conduction and continuous conduction along an axon and the role of myelin.

Answer 3

Saltatory conduction- has to insulate myelin (make it faster); myelin- insulates nerves and goes faster to the node of the ravier. ( myelinated)

Continuous conduction- Slowly does every step ( unmyelinated)

Question 4

Describe the structure and neurotransmitter involved in the neuromuscular junction and what makes it unique compared to neuron-neuron synaptic connections

Answer 4

The neuromuscular junction (NMJ) is a chemical synapse between an alpha motor neuron and a muscle fiber. The neurotransmitter involved is acetylcholine. At the NMJ, acetylcholine binding opens sodium channels, generating an end-plate potential (EPP). This triggers calcium channels to open in the sarcoplasmic reticulum, leading to muscle contraction. The NMJ differs from neuron-neuron synapses because the EPP is always large enough to trigger an action potential in the muscle fiber, ensuring reliable muscle activation.

Question 5

how do mechanoreceptors transmit information/generate APs? what are the four steps?

Answer 5

1. Stimulus applied- mechanical energy, i.e. physical deformation
2. Deformation of receptors or nerve endings ( or nerves)
3. Receptors potential generated
4. Action Potential generated

Question 6

what is the origin, termination, decussation level, and function of the corticospinal tract?

Answer 6

Corticospinal tract lateral:
-origin; primary motor cortex
-Termination; Spinal Motor Nuclei
-Decussation; medulla
-Function; Controls limb muscles
Corticospinal tract Ventral/ anterior:
-Origin; Primary Motor Cortex
-Decussation; terminal level
-Function; controls trunk/axial muscles; some bilateral control

Question 7

What is the origin, termination, decussation level, and function of the Vestibular tract?

Answer 7

Vestibular tract Lateral:
-Origin; Vestibular nuclei
-Termination: Lower motor neurons
-decussation; ipsilateral ( does not cross)
-Function; stabilizes head, coordinates head and body orientation

Vestibular tract medial;
-origin; Vestibular nuclei
-Termination; LMN for neck muscles
-Decussation; Bilateral input
-Function: stabilizes head, coordinates head and eye movements

Question 8

Describe and use the concepts of size principle, motor unit rotation, and motor synergies to describe how smooth voluntary movement could be produced.

Answer 8

Size Principle- Motor units are recruited in order of increasing size ( smaller motor units first) to meet force demands. Small motor units are recruited at low forces, and larger motor units are recruited as force increases.

Motor Unit Rotation- muscle force is kept constant. A change in the number of recruited motor units correlates (negatively) with their mean frequency of firing.

Motor Synergies- a neural organization of signals sent to elements ( muscles, joints, effectors, etc) of multi-element system that assures stable performance of a task

Question 9

Describe how equilibrium is maintained through postural control using concepts from class. Also, know specifics from the equilibrium triad, including influence of optic flow, mechanoreceptors, vestibular signals, and predictive/ reactive strategies.

Answer 9

Equilibrium is maintained by integrating information from the equilibrium triad: somatosensory, visual, and vestibular systems.
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Somatosensory: Proprioceptors provide information about body position and movement.
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Visual: Optic flow, the apparent motion of objects in the visual field, helps perceive self-motion and environmental stability.
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Vestibular: The vestibular system detects head position and movement relative to gravity and space.
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The nervous system uses predictive strategies to anticipate and counteract potential disturbances, such as activating calf muscles before a forward lean. When disturbances exceed the predictive capacity, reactive strategies, like automatic postural responses (APRs), are employed to regain balance. These include ankle, hip, stepping, weight-shift, and suspension strategies. The specific strategy depends on factors like perturbation size and sensory information available. The sources mention examples such as the “moving room experiment,”