Chapter 4: The Nervous System

Question 1

Neurons:

Answer 1

specialized cells that are capable of transmitting electrical impulses and then translating those electrical impulses to chemical signals.

Question 2

Parts of a neuron includes:

Answer 2

Nuclei, Dendrites, axon hillock, axons, myelins, myelin sheaths, Nodes of Ranvier, Nerve terminal, Synaptic Cleft, Synapses, Nerves, and Glial Cells

Question 3

Nuclei:

Answer 3

Nucleus that is located in the cell body. AKA (soma) § Soma has the E.R. and ribosomes.

Question 4

Dendrites:

Answer 4

These are appendages emanating directly from the soma. These receives incoming messages from other cells. Info received here are transmitted though the cell body before it reaches the axon hillock.

Question 5

Axon Hillock:

Answer 5

This is a specialized part of the cell body of a neuron that connects to the axon. This integrates incoming signals. □ Signals arriving from the dendrites can be either excitatory or inhibitory, the axon hillock will sum these signals, if its excitatory, it will start action potential.

Question 6

Axons:

Answer 6

These are long appendage that terminates in close proximity to a target structure.

Question 7

Myelins:

Answer 7

These prevents signal loss, or crossing of signals.

Question 8

Myelin Sheaths:

Answer 8

These maintains electric signal within neurons. § Is made by oligodendrocytes at the CNS, and Schwann cells in the PNS.

Question 9

Nodes of Ranvier:

Answer 9

These are small breaks in the myelin sheaths. § Rapid signal conduction.

Question 10

Nerve Terminal: AKA synaptic bouton (knob).

Answer 10

These are enlarged and flattened to maximize neurotransmission to the next neuron and ensure proper release of neurotransmitters.

Question 11

Synaptic Cleft:

Answer 11

This is the space between neurons, where terminal portion of axons releases neurotransmitters.

Question 12

Nerves:

Answer 12

These are multiple neurons that are bundled together in the peripheral nervous system.

Question 13

Glial Cells:

Answer 13

Aka neuralgia. These are neurons that are not only in the cells of nervous system. This includes Astrocytes, ependymal cells, and microglia.

Question 14

Astrocytes:

Answer 14

Glial cells that nourishes neurons and forms the blood-brain barrier, which controls the transmission of solutes from the bloodstream into the nervous tissue.

Question 15

Ependymal Cells:

Answer 15

Glial cells that lines the ventrical of the brain and produces cerebrospinal fluid. The cerebrospinal fluid physically supports the brain.

Question 16

Microglia:

Answer 16

These are phagocytic cells that injects or breakdown waste products and pathogens in the central nervous system.

Question 17

Action Potential:

Answer 17

This is an all or nothing messages use by neurons to relay electrical impulses down the axons to the synaptic bouton. • Also causes the release of neurotransmitters into synaptic cleft.

Question 18

Resting Membrane Potential:

Answer 18

This is the net electrical potential difference that exists across the cell membrane. This is created by the movement of charged molecules across that membrane. ○ For neuron potential is -70mV. 2 important ions involved in generating and maintaining it are potassium (K+) and sodium (Na+) or Na+/K+ ATPase.

Question 19

Potassium Leak Channels:

Answer 19

The cell membrane has this to facilitate the outward movement of potassium. § Allows the slow leak of potassium from the cells.

Question 20

Sodium Leak Channels:

Answer 20

This is the opposite of potassium, since this is being pushed inside the cell. § Potassium has a high concentration inside the cell and has a low one outside the cell, while sodium has a low inside and a high outside. § This is a slow leak of sodium into the cell that causers a buildup of electric potential.

Question 21

The Na+/K+ ATPase pumps what?

Answer 21

It pumps out 3 sodium ions out of the cell for every 2 potassium ions pumped in.

Question 22

Resting Membrane Potential Summarized:

Answer 22

It is a tug of war between potassium and sodium. Potassium movement pulls the cell potential and sodium 90 mV, while sodium movement pulls the cell potential opposite away towards 60 mV. No ions win the war, its balance and its reached at 70 mV. This balance is the resting membrane potential.

Question 23

Excitatory:

Answer 23

When the signals of the axon hillock are this. It causes depolarization of neurons. It makes neurons more likely to fire an action potential. It will fire an action potential only when its depolarization threshold value is in the -55 to -40 mV.

Question 24

Depolarization:

Answer 24

This is when the membrane potential is raised from its resting potential. When the signals in the axon hillock are excitatory.

Question 25

Inhibitory:

Answer 25

When the signals of the axon hillock are this. It causes a hyperpolarization of neurons. Which is when the membrane potential is lowered from its resting potential. It makes neurons less likely to fire an action potential.

Question 26

Summation: What are the two types:

Answer 26

When there are multiple signals. Temporal Summation: addition of multiple signals near each other in time. Spatial Summation: addition of multiple signals near each other in space.

Question 27

How action potential works:

Answer 27

It is used to propagate signals down the axon. It only works in one direction. • Needs to be enough excitatory signal, so the cells can depolarized, and the voltage-gated sodium channels open. • At a peak of action potential (+35 mV), the sodium channels will be inactivated, and the potassium channel will open. • Potassium will then flow out of the neuron, repolarizing the cell. This channel will be open until it overshoots the action potential, which will result in hyperpolarized neuron, and then this channel will close.

Question 28

What will happen when the voltage-gated sodium channels open up?

Answer 28

It will cause the sodium to flow into the neurons and it will continue to depolarize the neuron.

Question 29

Hyperpolarized:

Answer 29

It will be in its refractory period: □ Absolute Refractory Period: The cell is unable to fire another action potential. □ Relative Refractory Period: The cell requires a large than normal stimulus to fire an action potential.

Question 30

Synapse:

Answer 30

This is a structure in the nervous system that permits a neuron to pass an electrical or chemical signal to another neuron or to the target effector cell. It includes Synaptic cleft, presynpatc cleft, postsynpatic cleft and an effector.

Question 31

Presynaptic Cleft:

Answer 31

Part of the Synapse. This is the neuron that is proceeding the synaptic cleft.

Question 32

PostSynaptic Cleft:

Answer 32

Part of the Synapse. This is the neuron after the synaptic cleft.

Question 33

Effector:

Answer 33

Part of the Synapse: This is if the neuron signals to a gland or a muscle, rather than another neuron.

Question 34

Neurotransmitters:

Answer 34

Are stored in membrane-bound vesicles in the nerve terminal, before being released into the synapse. They cause the voltage-gated calcium channels open up, when the action potential arrives at the nerve terminal. These bind to receptors on the postsynaptic cell,and will eventually be removed from the postsynaptic receptors.

Question 35

The increase in intracellular calcium will cause what?

Answer 35

It will the cause the fusion of membrane-bound vesicles with the cell membrane in the synapse causing exocytosis of the neurotransmitter into the synaptic cleft. •

Question 36

When the Neurotransmitter binds to receptors on the postsynaptic cell what will happen?

Answer 36

When it binds to receptors on the postsynaptic cell, it will allow the message to be passed from one neuron to the next by: Ligand-gated Ion Channels or G-Coupled Protein Receptor.

Question 37

Ligand-gated Ion Channel:

Answer 37

In this, the postsynaptic cell will either be depolarized or hyperpolarized.

Question 38

G protein-coupled receptor:

Answer 38

In this, the postsynaptic cell will cause either changes in the levels of cyclic AMP (cAMP) or an influx of calcium.

Question 39

Why are neurotransmitters removed from the postsynaptic receptors:

Answer 39

They are removed to stop the propagation of the signal. (3 mechanisms)

Question 40

3 mechanisms to remove neurotransmitters from the postsynaptic receptor:

Answer 40

Neurotransmitters must be broken down by enzymatic reactions. § Example: Acetylcholine (ACh) by acetylcholinesterase (AChE) Neurotransmitters must be brought back into presynaptic cells using reuptake carriers. § Example: serotonin, dopamine, and norepinephrine. ○ Neurotransmitters must diffuse out of the synaptic cleft. § Example: Nitric Oxide.

Question 41

The Nervous System:

Answer 41

Maintains Homeostasis. Functions are motor functions, cognitive thinking, problem solving, planning, language, sensation and perception, memory, coordination (body), emotion, hear rates, breathing, temperature, endocrine organs, etc.. Consists of 3 types of nerve cells in the nervous system are: A. Sensory, B. Motor, & C. Interneurons. Can be divided into the Central Nervous System and the Peripheral Nervous System.

Question 42

Central Nervous System (CNS):

Answer 42

It includes the brain and the spinal cord.

Question 43

Brain:

Answer 43

Is part of the CNS and has the grey + white matter. § Grey: unmyelinated cell bodies and dendrites. § White: Axons encased in myelin sheaths.

Question 44

Spinal Cord:

Answer 44

Is part of the CNS that extends downward from the brainstem and is divided into 4 parts. § Four parts are: cervical, thoracic, lumbar, & sacral. § This is protected by the vertebral column.

Question 45

Vertebral Column:

Answer 45

This protects the spinal cord. This transmits nerves at the space between adjacent vertebrae. ® Also white + grey matter.

Question 46

Peripheral Nervous System (PNS):

Answer 46

This made of nerve tissue and fiber outside the brain and spinal cord. It includes the Somatic and the Autonomic. This connects the CNS to the rest of the brain.

Question 47

Somatic Nervous System:

Answer 47

Part of the peripheral nervous system. This includes the sensory + motor neurons in the skin, joints, and the muscles. This transmits information through afferent fibers.

Question 48

Autonomic Nervous System:

Answer 48

Part of the peripheral nervous system and can be further subdivided into 2(parasympathetic and sympathetic), that act in opposition to each other.

Question 49

Parasympathetic Nervous System:

Answer 49

Part of the Autonomic Nervous System. This conserves energy. □ Acetylcholine is the neurotransmitter is responsible. □ Functions include: constrict pupils, stimulate salvia, constrict bronchi, slow heartrate, stimulate bile, constrict bladder, reduce heartrate, resting and sleeping states.

Question 50

Sympathetic Nervous System:

Answer 50

Part of the Autonomic Nervous System. This is activated by stress. □ Associated with rage and fear reactions. (fight or flight) □ Opposite of parasympathetic functions. □ Increases heartrate, relaxes bronchi, decreases digestion, dilates pupils, and inhibits salivation.

Question 51

Difference between the parasympathetic and sympathetic nervous system include:

Answer 51

Difference between parasympathetic and sympathetic nervous system, are that the parasympathetic contains 2 neurons, which are: § Pre-Ganglionic Neurons § Post-Ganglionic Neurons

Question 52

Reflex Arcs:

Answer 52

Neural Circuits that control reflexive behavior. § Uses the ability of interneurons in the spinal cord to relay information to the source of a stimulus while simultaneously routing it to the brain. § Two types: A. Monosynaptic & B. Polysynaptic

Question 53

Monosynaptic Reflex Arc:

Answer 53

This reflex arc uses sensory neurons that fires onto a motor neuron.

Question 54

Polysynaptic Reflex Arc:

Answer 54

This reflex arc uses sensory neurons that fires a motor neuron, and interneurons to motor neurons.