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Physiology 1020 > Unit 2: Nerves, Muscles & the Nervous System > Flashcards

Unit 2: Nerves, Muscles & the Nervous System Flashcards

1
Q

Define Depolarization.

A

Depolarization is the process in which ions move in and out of the cell, and the inside of the cell becomes more positive relative to the RMP.

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2
Q

Why can’t an AP be fired during the absolute refractory period (depolarization and repolarization)?

A

This is due to the inactivation gate of the voltage-gated Na channel.

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3
Q

Why is it harder for an Ap to be fired during the relative refractory period (hyperpolarization?

A

This is because the inside of the cell is more negative relative to its RMP, therefore, a greater stimulus would be required.

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4
Q

What triggers the opening in both Na and K voltage-gated channels?

A

Change in voltage.
Na channels open at -55mV
K channels open at +35mV

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5
Q

Why is myelin important for saltatory conduction?

A

A myelinated neuron conducts an AP 10-15 times faster than an unmyelinated neuron, resulting faster transmission.

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6
Q

What are glial cells?

A

Glial cells make up 90% of the brain, and provide a necessary environment for neurons to function properly

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7
Q

What are the 3 types of neurons?

A

Bipolar: 2 processes extending from the cell body (1 axon and 1 dendrite), found in the retina of the eye.
Unipolar: 1 process (straight connection between axon and dendrites), sensory, transmit signals to the spinal cord.
Multipolar: CNS, connect CNS with effector organs.

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8
Q

What are the types of Neuroglia in the CNS?

A

Ependymal Cells: create CSF and circulate and absorb CSF, line the ventricles of the brain and spinal cord, help distribute hormones and signal molecules associated with the CNS.
Astrocytes: most abundant cell in the brain, provide nutritional support for neuron, clean-up brain debris, hold neurons in place, promote synaptic connections, respond to brain injury and inflammation.
Oligodendrocytes: myelin-forming cells in the CNS.
Microglia: remove foreign materials, cells or organisms, or previously formed synapses.

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9
Q

What are the types of Neuroglia in the PNS?

A

Schwaan Cells: cover the axons of neurons in myelin.
Satellite Cells: provide nutrients and structural support, ensheath the soma of neuron bodies in ganglions.

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10
Q

What are the 4 lobes of the brain, and their function?

A

Frontal Lobe: processes input from skeletal muscles (primary motor cortex), the premotor cortex and prefrontal cortex work together to integrate movement information with other sensory inputs to generate perception of stimuli.
Parietal Lobe: receives input from major senses (primary somatosensory cortex).
Occipital Lobe: responsible for vision, primary visual cortex receives input from the optic nerve, and the visual association areas process visual information and integrate it with other sensory inputs.
Temporal Lobe: consists of the primary auditory cortex and auditory associated areas, which receive and process signals from the auditory nerve and integrate it with other inputs, used for short-term memory and smell (olfaction).

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11
Q

Define the role of the cerebellum in the brain.

A

The cerebellum integrates coordinated movement, and receives sensory information, and coordinates the execution of movement in the body.

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12
Q

Define the role of the corpus callosum in the brain.

A

It is the connection site between both cerebral hemispheres. This connection integrates sensory and motor information, which results in whole-body movement.

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13
Q

What are the 3 sections of the brain stem?

A

Midbrain: controls eye movement, auditory, and visual motor reflexes.
Pons: transfers information between the cerebellum and the cerebral cortex, controls breathing.
Medulla: involuntary functions, fibres from corticospinal tract (motor cortex) cross over to innervate muscles on the opposite side of the body.

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14
Q

What are the 3 main components of a chemical synapse?

A

Pre-synaptic Neuron,
Synaptic Cleft
Post-synaptic Neuron

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15
Q

In a chemical synapse neurotransmitters are released from the pre-synaptic neuron into the synaptic cleft. From there, what are the 4 possible fates neurotransmitters have?

A

Bind to receptors on post-synaptic neuron
Diffuse out of the synapse
Get broken down by enzymes in the synaptic cleft
Re-uptake into pre-synaptic cleft (recycled)

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16
Q

Why can’t the dendrites or the soma elict an AP?

A

The dendrites and the soma do not have voltage-gated channels, which are essential for forming an AP.

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17
Q

Define an Excitatory Post-Synaptic Potential (EPSP).

A

EPSPs do not produce an AP but they bring the neuron closer to an AP, they are localized which leads to depolarization on one area of the plasma membrane. The magnitude of depolarization is equal to the magnitude of stimulus (higher the stimulus, higher the depolarization). They decay overtime, meaning the stimulus gets weaker overtime and distance. Produced by neurotransmitters that open NA and K channels.

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18
Q

Define an Inhibitory Post-Synaptic Potential (IPSP).

A

IPSPs bring the neuron farther away from an AP. They are localized, meaning it leads to the hyperpolarization of one area of the plasma membrane. The magnitude of the stimulus is equal to the magnitude of hyperpolarization (higher the stimulus, higher the hyperpolarization). They decay, and are produced by neurotransmitters that open K (in), and Cl (out) of the cell.

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19
Q

What are the 2 ways in which an EPSPs can be increased?

A

Temporal Summation: additive effect, one neuron is firing repeatedly on the pre-synaptic neuron.
Spatial Summation: additive effect, many neurons are firing at the same time on the post-synaptic neuron.

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20
Q

What is the name of the neurotransmitter at the NMJ?

A

Acetylcholine.

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21
Q

At the NMJ, once acyetlcholine moves into the post-synaptic membrane it can get broken down by acetylcholinesterase. What 2 particles form when ACh gets broken down, and what happens?

A

Acetate and Choline form once broken down by acetylcholinesterase. Choline is then recycled back into the pre-synaptic cell, and is used to produce more acetylcholine.

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22
Q

What may happen if acetylcholinesterase is blocked in the NMJ?

A

ACh will be present in the synaptic cleft longer, therefore increasing the chance that an AP will develop in the skeletal muscle cell.

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23
Q

What is a graded current called in skeletal muscles?

A

End plate current (EPC), which can generate end plate potentials (EPPs) that can lead to an AP.

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24
Q

What happens in your muscle cells if you’re diagnosed with myasthenia gravis?

A

Myasthenia gravis is an autoimmune disease, that causes weakness in the skeletal muscles. This weakness developed because the body elicits antibodies that restrict the binding of acetylcholine on nicotinic receptors.

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25
Q

What is the triad made up of in a muscle fibre?

A

Transverse Tubules and Terminal Cisternae.

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26
Q

What are the 3 associated proteins associated with the thin myofilament?

A

Actin (globular protein)
Tropomyosin (rod-shaped protein)
Tropinin (troponin A, troponin C, troponin T).

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27
Q

What happens to the sarcomere when a muscle contracts?

A

When a muscle contracts, the sarcomere shortens/constricts.

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28
Q

Where is the voltage sensor connected to on the transverse tubules?

A

It is located on the terminal cisternae of the SR.

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29
Q

Describe the role of the voltage sensors during excitation-contraction coupling.

A

Voltage sensors detect AP. The change in voltage causes the Ca channels to open, releasing Ca ions from the SR into the muscle cell.

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30
Q

What is the role of Ca ion in excitation-contraction coupling?

A

Ca ion binds to troponin C, which removes tropomyosin from the myosin binding sites of actin. Then, troponin changes shape, and moves exposing the myosin binding site.

31
Q

What happens when myosin attaches to actin (cross-bridge formation)?

A

A power stroke occurs. This causes the thin myofilament to slide past the thick myofilament towards the M-line. This causes the muscle to contract.

32
Q

What is the role of Calcium ATPase in excitation-contraction coupling?

A

When there is no longer a change in voltage, calcium ATPase pumps Ca ions back into the SR. This causes the concentration of Ca to decrease in the cytoplasm.

33
Q

What is Rigor Mortis?

A

The stiffening of the muscle after death. Actin and myosin remain fused to each other because no ATP can be produced to remove them from each other.

34
Q

Why is there a short delay in the latent period of a muscle twitch?

A

This is due to the time Ca ions are being released from the SR, and binding to troponin c. This causes tropomyosin to shift and expose myosin binding sites on actin (forming cross-bridge).

35
Q

Why do our muscles move smoothy without jerky movements?

A

This is due to the motor unit ordering and firing.
Ordering - interspread arrangement of muscle cells ensures the muscle contracts smoothy, even if not all motor units are contracting at the same time.
Firing - motor units fore asynchronously

36
Q

Why might more motor units need to be recruited during a muscle contraction?

A

This is due to an increased load or demand on the muscle to generate force

37
Q

What is the difference between unfused tetanus and complete tetanus?

A

Unfused Tetanus - when the frequency of the AP still allows for partial relaxation between twitches. this causes tension in the muscle to plateau.
Complete Tetanus - when AP frequency is so high, there is no relaxation between muscle twitches. All twitches summate to provide smooth, sustained movements.

38
Q

Is the somatic motor system control voluntary or involuntary movement to the skeletal muscles?

A

Voluntary movement.

39
Q

Explain the function of the premotor cortex.

A

Located in the frontal lobe of the brain, and it is responsible for developing the appropriate strategy for movements that are necessary to perform a task (origin of the sequence of events).

40
Q

Explain the function of the supplementary cortex.

A

Information from the premotor cortex travels here, (frontal lobe of the brain) and it programs the motor sequences needed to perform and action.

40
Q

Explain the function of the primary motor cortex.

A

Responsible for activating the neurons needed for the appropriate muscles to perform an action/task. Includes the motor homunculus as well.

41
Q

Explain the function of the motor homunculus.

A

Illustrates/projection of the brain areas that are responsible for motor function in different parts of the body. Medial to lateral.

42
Q

Explain the function of the primary somatosensory cortex.

A

Receives information from the thalamus, and detect sensory information from the body (temperature, proprioception, touch, texture, and pain).

43
Q

What is the main function of the corticospinal tract?

A

Major pathway from the primary motor cortex to the motor neurons that innervate the muscle cells.

44
Q

In the corticospinal tract, where does the splitting of the nerve fibres occur?

A

At the decussation of the pyramids.

44
Q

If a nerve cell is activated in the left pre central gyrus near the midline (top and central region) of the brain what will occur?

A

Muscle contraction will occur in the right leg.

45
Q

What is the main function of the muscle spindles?

A

Detect muscle stretch, length, and the rate of change in the skeletal muscle. The muscle spindle can sense when the muscle is over stretch, and send signals to our brain to increase force production (increasing frequency of the AP) to reduce injury/damage to our muscles. The more stretched the muscle, the more stretched the region, resulting in a higher. frequency of the AP.

46
Q

What is the main function of the Golgi tendon organ?

A

Detect muscle tension and signals information about the load or force applied to a muscle. When force is applied to the muscle, the collagen fibres squeeze and distort the plasma membranes, causing a depolarization of the afferent neuron, firing an AP.

47
Q

What is the difference between a primary afferent and a secondary afferent stretch receptor?

A

Primary afferents provide information about length and velocity of a muscle, and they fire at high rates during stretching of the muscle (firing rate depends on the rate of change of the muscle length). Secondary Afferents provide information about length of a muscle only. The firing rate depends only on the immediate length of the muscle, not the rate of change of the muscle length. However, they both send sensory information from the spindle to the CNS.

48
Q

Define alpha-gamma coactivation.

A

Needed for the muscle to function properly, and for the brain to always know where the muscle is in space and how much power it needs to perform an action. In order for this to occur, commands are sent simultaneously through the gamma motor neurons to the intrafusal fibres, causing a contraction within the infrafusal fibres. This contraction maintains stretch on the central region where central receptors are located, therefore the muscle spindles can send information to the brain about muscle and limb position.

49
Q

What is the difference between an alpha motor nueron and a gamma motor neuron?

A

Alpha motor neurons innervate extrafusal fibers, which are the fibres that contract to generate power. It can also innervate many muscle fibres at the same time. Gamma motor neurons innervate intrafusal fibres, which are the fibres that keep the muscle sensitive to stretch. They allow the intrafusal fibres to stretch along the extrafusal fibres, allowing for continuous communication with the CNS.

50
Q

True or False.
In the reflex arc, information is carried to your brain, and afferent neurons synapse with efferent neurons.

A

False. Information is carried to your spinal cord via afferent pathways, and the afferent neuron synapses with an interneuron within the spinal cord. From there, the interneuron will synapse with and efferent neuron, and travel to affector organ via efferent pathways.

51
Q

Does the autonomic nervous system control voluntary or involuntary movement?

A

Involuntary movement.

52
Q

What is the main functions of the hypothalamus?

A

The control centre. It makes decisions on the course of action and information sent from the CNS out to effector organs via efferent pathways. It performs important functions through negative feedback control.

52
Q

What is the difference between sympathetic and parasympathetic nervous systems?

A

The sympathetic nervous system responds to fight or flight situations, and parasympathetic responds to rest and digest/relaxation situations.

53
Q

How does the cerebellum correct movement?

A

The cerebellum integrates information, by comparing It to the information it gets from the proprioceptors. Feedback received from sensory input gives the cerebellum additional information for making adjustments initially sent by the motor cortex.

54
Q

Define the autonomic ganglion.

A

In both the sympathetic and parasympathetic nervous systems, and it is a group of cell bodies that the preganglionic neuron synapses onto to relay information to target organ(s).

55
Q

True or false.
The post ganglionic neuron in the sympathetic nervous system is long, myelinated, and releases epinephrine and noradrenaline onto the target organ.

A

True.

56
Q

What is the main neurotransmitter released at the target organ of the postganglionic neuron of the parasympathetic nervous system?

A

Acetylcholine.

57
Q

True or false.
The preganglionic neuron of the parasympathetic nervous system is short and closer to the CNS.

A

False. The perganglionic neuron of the parasympathetic nervous system is long, and closer to the target organ.

58
Q

What are the 4 types of environmental stimuli?

A

Mechanical (touch, pressure, vibration, sound), chemical (taste, odours, pains), electromagnetic (light), other stimuli (gravity, motion, acceleration, heat).

59
Q

Define an adequate stimulus.

A

It is a particular form of environmental stimulus to which the sensory receptor is most sensitive.

60
Q

Define the somatosensory system.

A

Detects and processes sensations of touch, vibration, temperature and pain. Majority of these sensations originate in the skin.

61
Q

True or false.
Free nerve endings detect deep pressure and high frequency vibrations.

A

False. Free nerve endings detect pain, temperature, and light touch.

62
Q

What type of sensations do the Ruffini corpuscles detect?

A

Sustained pressure and skin stretch. Slow/continuous response.

63
Q

How do these sensory nerves respond to a stimulus?

A

They release neurotransmitters, which stimulate the dendrites of a sensory neuron, then gets translated into an AP.

64
Q

True or false.
Receptor generated potentials proportional to the stimulus; they themselves are not AP.

A

True.

65
Q

What is neural coding?

A

It is a response to stimulus. It elicts fewer or more AP, and the Brin interprets the frequency of the AP.

66
Q

True or false.
The spinothalamic tract brings fine detail, proprioception and vibration to the brain.

A

False. The spinothalamic tract brings pain, crude touch, and temperature information to the brain. The dorsal column-medial lemniscal system takes fine detail, proprioception and vibration to the brain.

67
Q

What are the 3 photopigments that the cones contain?

A

S-cones (short wavelengths, blue). M-cones (medium wavelengths, green). L-cones (long wavelengths, red).

68
Q

What is the difference between rod cells and cone cells?

A

Rod cells function best under low-light, and do not detect colour or fine detail. Cone cells function best under bright light, and detect colours and fine details.

69
Q

What happens to both rod and cone cells in complete darkness?

A

In complete darkness, both cells will depolarize and release neurotransmitters that inhibits bipolar cells. Na/K pumps are open, and Na enters the cell and K exits the cell.

70
Q

What happens to both rod and cone cells in bright light?

A

In bright light, both cells will hyperpolarize, and stop releasing neurotransmitters. This causes bipolar cells to release neurotransmitters to ganglion cells, and have a graded potential. Na channel is closed, no Na movement, K channel is open, K is leaving the cell.

71
Q

What are the 4 types of eye movement?

A

Saccades (rapid, jerky movements), smooth pursuit (smooth movement), Vestibular Ocular Reflex (eye is focus when head is moving), Vergences (movement when an object is approaching or moving away)

Physiology 1020 (2 decks)

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