Chapter 4 - Nervous System

Question 1

At resting membrane potential, the voltage = ___?

Answer 1

-70 mV

Question 2

What is a receptor potential?

Answer 2

A receptor potential happens when a sensory neuron is activated by external stimuli like light or sound, but the activation is transient lasting only for a fraction of a second.
Essentially it’s a brief change of the resting membrane potential.

Question 3

What is a synaptic potential?

Answer 3

These potentials occur at synaptic contacts between neurons and are a means of communication between the synaptic cleft.
The more synapses activated, the higher the amplitude of the synaptic potential.

Question 4

What is an action potential?

Answer 4

An all or none signal that travels along the axon if a neuron

Question 5

The more intense a stimulus is that is the stronger the receptor potential, the higher the (amplitude/frequency) of action potentials.

Answer 5

Frequency.
The amplitude of an action potential doesn’t change depending on stimulus intensity.

Question 6

Important characteristics of neurons:

Answer 6

-Are frozen in G0 phase
-Depend entirely on glucose for energy
-Don’t respond to insulin for glucose uptake, insulin has no effect
-Have very low glycogen & oxygen storage capability

Question 7

What happens if the external potassium concentration is increased?

Answer 7

The resting membrane potential becomes less negative because not as much potassium will leak out of the cell, making the inside of the cell more positive.

Question 8

What is the main contributor to the resting membrane potential?

Answer 8

The high resting membrane permeability to K+ caused by the permeable K leak channels and the K concentration gradient

Question 9

Depolarization of the membrane results in a rise in permeability of ____

Answer 9

Na+

Question 10

If you lower the external Na+ concentration, how is the resting membrane potential and action potential of a cell affected?

Answer 10

The resting membrane potential is not affected but the amplitude of the action potential decreases.

Question 11

What is the equilibrium potential of an ion?

Answer 11

It is the membrane potential for a given ion where there is no net ionic movement across the membrane for that ion.

Question 12

What is a graded potential and what are the two types?

Answer 12

It is a temporary transient change in the membrane voltage and varies, depending on the intensity of the external stimulus. This isn’t “all or none” like an action potential.
The two types are receptor potential or synaptic potential .

Question 13

Why do action potentials only travel one way?

Answer 13

As current travels down an axon, subsequent regions are depolarized in order. The previous region goes into a refractory period (inactivation of Na channels) preventing re-excitation of this part of the membrane and causes the signal to move in a forward manner.

Question 14

How is an action potential propagated?

Answer 14

It is propagated through a process called impulse propagation. A graded potential depolarizes the membrane to the absolute threshold, causing voltage gated sodium channels to open and sodium to rush into one segment of the axon. This depolarization causes the next region to depolarize which allows sodium channels to open in that segment and sodium to rush in. The action potential travels in a wave-like fashion until it reaches the axon terminal.

Question 15

When the reaches about +35 mV, what happens in the cell?

Answer 15

Sodium channels are in activated and voltage gated potassium channels are slowly starting to open, which causes repolarization of the cell when potassium ions flow outward.

Question 16

What causes hyperpolarization of the membrane after an action potential?

Answer 16

The efflux of potassium ions out of the cell causes the membrane potential to become very negative, essentially allowing the neuron to become refractory to further action potentials.

Question 17

What is the difference between an absolute refractory period and a relative refractory period?

Answer 17

During an absolute refractory period no amount of stimuli can cause another action potential to occur. This period occurs during the actual depolarization phase of an action potential.
During a relative refractory period, there must be greater than normal stimulus to cause an action potential. This period occurs during the hyperpolarization phase of the action potential.

Question 18

What are the two types of summation?

Answer 18

Temporal and spatial summation

Question 19

What is the equilibrium potential for potassium?

Answer 19

-90 mV

Question 20

What is the equilibrium potential for sodium?

Answer 20

+65 mV

Question 21

What is the purpose of myelin?

Answer 21

It acts as a insulator, preventing the dissipation of ions from the neuronal membrane, allowing for faster conduction of the signal.

Question 22

What is the function of the nodes of Ranvier?

Answer 22

They have Na+ channels which are in contact with the extracellular fluid. This allows for rapid entry of Na into the axon & depolarization at each node. This causes the electric current to hop from node to node allow for faster rate at which neural impulses are conducted.

Question 23

What is the axon hillock and its function?

Answer 23

It is the region where the axon joins the cell body. It has a high concentration of voltage gated Na channels which makes it sensitive to APs.

Question 24

Spatial summation

Answer 24

Refers to the impulses received at different places on the neuron which can add up to make the neuron fire. These impulses can’t cause firing on their own however.

Question 25

Temporal summation

Answer 25

Refers to multiple graded potentials/stimulation received at the same place within close timing of each other can add up to cause an action potential

Question 26

How is blood flow to the skin affected by sympathetic and parasympathetic stimulation?

Answer 26

Sympathetic stimulation causes decreased blood flow to the skin.
Parasympathetic stimulation causes increased blood flow to the skin.

Question 27

How are neurotransmitters removed from the synaptic cleft?

Answer 27

1. Broken down by enzymes such as acetylcholinesterase
2. Brought back into the presynaptic neuron using reuptake carriers
3. Some neurotransmitters can simply diffuse out of the synaptic cleft

Question 28

Which neurotransmitter can diffuse out of the synaptic cleft?

Answer 28

Nitric oxide

Question 29

Mneumonic to remember afferent and efferent neurons

Answer 29

Afferent neurons ascend in the spinal cord to the brain.
Efferent neurons exit the spinal cord going to the effector targets.

Question 30

What makes up the peripheral nervous system?

Answer 30

31 pairs of spinal nerves and 10/12 pairs of cranial nerves (excluding the old factory and optic nerves)

Question 31

What is the somatic nervous system made of?

Answer 31

It is made of sensory and motor neurons distributed throughout the skin, joints, and skeletal muscles. Controls voluntary movement and conscious perception of pain, heat, and pressure.

Question 32

Mneumonic for remembering function of somatic nervous system.

Answer 32

Somatic = skeletal muscles

Question 33

What are the functions of the autonomic nervous system?

Answer 33

Heartbeat regulation, respiration, digestion, glandular secretions, and temperature control.

Question 34

The ______________ causes bladder contraction,while the ____________ inhibits bladder contraction.

Answer 34

parasympathetic nervous system, sympathetic nervous system

Question 35

Main difference between the somatic and autonomic nervous system?

Answer 35

The somatic nervous system has motor neurons which go directly from the spinal cord to the muscle.
The autonomic nervous system has 2 neurons working in series that synapse on a ganglion (a presynaptic neuron and postsynaptic neuron).

Question 36

What are the neurotransmitters released by the parasympathetic nervous system?

Answer 36

Acetylcholine is released by both the preganglionic and postganglionic neurons.

Question 37

What are the neurotransmitters released by the sympathetic nervous system?

Answer 37

Preganglionic neurons release acetylcholine while postganglionic neurons release norepinephrine.

Question 38

The knee jerk reflex is an example of what type of reflex arc?

Answer 38

Monosynaptic reflex arc
(Example of a SOMATIC reflex arc because it activates skeletal muscle)

Question 39

Differentiate between somatic vs. autonomic reflexes

Answer 39

Somatic reflexes - activate response to skeletal muscle; reflex arc involves either afferent +efferent neuron OR afferent, interneuron, & efferent neuron

Autonomic reflexes - activate response to glands, smooth muscle, cardiac muscle; reflex arc always involves 3 neurons (afferent, interneuron (preganglionic neuron) & efferent (postganglionic neuron)

Question 40

Autonomic reflexes are always (monosynaptic/polysynaptic), whereas somatic reflexes can be either mono or polysynaptic.

Answer 40

polysynaptic

Question 41

If blood flow to the brain is interrupted, why do neurons die and brain damage occurs rapidly?

Answer 41

Unlike in other cells of the bodies, neurons have very LITTLE glucose stored in their cells and essentially no oxygen storage capability. That is why a continuous & rapid rate of blood flow to the brain is required to bring oxygen to the tissues.

Question 42

Glucose uptake in a neuron would increase if …..?

Answer 42

1. The neuron was excited
2. Blood glucose concentration increased (allow glucose to be taken in by facilitated transport down its concentration gradient)
3. The number of Glucose transporters in the neuronal membrane increased

Question 43

For a sympathetic response _________ neurotransmitter is used at the ganglionic synapse, while the __________ neurotransmitter is used at the effector region.

Answer 43

Acetylcholine, norepinephrine

Question 44

Adrenergic receptors bind what kinds of neurotransmitters?

Answer 44

Norepinephrine and epinephrine

Question 45

There are two types of cholinergic receptors, what are they?

Answer 45

Nicotinic and muscurinic