Unit 5 muscles Flashcards
What are the steps of voluntary control of muscles?
The primary motor cortex, an area of the brain initiates movement and sends a signal through the spinal cord through the motor neuron and finally to the skeletal muscle.
What is the general pathway of involuntary control of muscles?
Such a pathway is called a reflex arc. A stimulus is first detected by a receptor. An afferent (sensory) neuron then sends a signal from the receptor to the CNS. An integrating center, be it the brain stem OR the spinal cord receives a signal from the sensory neuron and sends a signal to the motor neuron. The efferent (motor) neuron sends a signal from integrating center to muscle. The effector is the muscle that moves.
What happens if the primary motor cortex on the left side is damaged?
There is no control or less control of movement on the right side of the body. Specific area of motor cortex controls specific motor neurons and thus specific muscles.
What are somatic reflexes?
These are the reflexes where the effector are the skeletal muscles and the integrating center is the spinal cord.
Give an example of a specific type of somatic reflex and explain it.
A specific type of somatic reflex is the stretch reflex. An specific instance of this is the patellar reflex where the receptors are the muscle spindles (they detect changes in muscle length) and the integrating center is the spinal cord. It helps maintain body position.
What is a withdrawal reflex also known as flexor reflex?
A withdrawal reflex is a type of reflex where more than one neuron is used to withdraw a hand or a foot and more than one muscle group. It also sends additional signals to brain independent of reflex arc.
Describe the crossed extensor reflex.
It occurs with the flexor reflex. It involves the movement of muscle on the opposite side of the body.
What does action potential and impulse conduction?
They are the processes that send signal along the length of one neuron using an electrochemical gradient (ions and flow of electric charges).
What is the first step of the action potential?
It is the resting membrane potential, the charge across neuron membrane at rest, which is 70 mV. It is more negative inside the neuron.
What is the second step of an action potential?
It is the initiation of the impulse. Sodium ions enter through the sodium channels in neuron membrane (receptor).
Name the five types of receptors and their trigger.
Mechanoreceptors (physical change), thermoreceptors (temperatue change), electroreceptors (change in charge voltage gated), chemorecpetors (respond to specific chemicals ligand gated), photoreceptors (light), nociceptors (pain or excess stimulation)
How does a signal gets initiated?
To initiate a signal, the membrane potential must reach -55 mV, the threshold. This potential stimulates the opening of the voltage-gated NA+ channels.
What is the third step of an action potential?
The depolarization: impulse is transferred along the neuron membrane as adjacent voltage-gated sodium ion channels open.
By what steps does the depolarization occur?
a. voltage-gated Na+ channels are stimulated to open by increase in membrane potential
b. gates open quickly
c. Na+ rush into neuron
d. membrane potential increases dramatically
e. when membrane potential reaches between 0 and +30 mV, voltage-gated Na+ channels close to prevent further influx of Na+
f. membrane potential near +30 mV will stimulate K+ channels to open
What is the fourth step of an action potential?
It is the repolarization.
a. K+ flow out of cell
b. at about -55 mV, K+ channels will start to close but a hyperpolarization will occur (membrane potential of less than -70mV)
