Nervous System

Question 1

Central Nervous System

Answer 1

Structural and functional center of the nervous system.

Consists of the brain and spinal cord

Question 2

Peripheral Nervous System

Answer 2

Nerves that lie in the “outer regions” of the nervous system.

Includes 12 cranial nerves and 31 spinal nerves

Question 3

Afferent Neurons

Answer 3

Incoming sensory pathways; carries signal towards the spinal cord and brain

Question 4

Efferent Neurons

Answer 4

Outgoing motor pathways; carries signal away the spinal cord and brain

Question 5

Interneurons

Answer 5

Conduct signals from afferent to efferent neurons

Question 6

Phrenic Nerve

Answer 6

Originate from the cervical spine (C 3-5)

Innervates the diaphgram

Question 7

Injury to the Phrenic Nerve

Answer 7

Paralysis of diaphragm (breathing may still be possible if accessory nerves are still intact)

Question 8

Intercostal Nerves

Answer 8

Spinal nerves that innervate the intercostal muscles

Question 9

Cervical Nerve Plexus

Answer 9

The phrenic nerve will exit this plexus from C3, C4, and C5 levels. Spinal cords that are injured above the C3 level will paralyze the diaphragm and all other ventilatory muscles

Question 10

Autonomic Nervous System

Answer 10

Major Functions (involuntary)-Regulate HR, smooth muscle contraction, glandular secretions

Divided into sympathetic and parasympathetic nervous system

Question 11

Sympathetic Division

Answer 11

Fight or Flight response

_Innervated:_4-5 thoracic nerves (spinal nerves)

Target Organs: Adrenal medulla (secretes epi, NE, and dopamine)

Neurotransmitter: Norepinephrine

Overstimulation: Will stimulate ß₂ receptors in the airway causes bronchodilation

*DOES NOT INNERVATE SMOOTH MUSCLE rather the airway smooth muscle contained adrenergic receptors which respond to epinephrine secreted by the adrenal gland

Question 12

Parasympathetic Division

Answer 12

Rest and Digest

Innervated: Right and left vagus nerve (crania nerve)

Target Organs: Smooth airway muscles, mucous glands, [pulmonary vasculature

Neurotransmitter: Acetylcholine

Overstimulation: Bronchospasm, increased mucous production and thickness

Question 13

Pulmonary Plexus

Answer 13

The anterior and posterior pulmonary plexus will innervate the bronchial tree and visceral pleura

Question 14

Preganglionic Neurons

Answer 14

All preganglionic neurons are cholinergic and will secrete acetylcholine (Ach) which will bind to nicotinic receptors and postganglionic fibers

Question 15

Sympathetic post-ganglionic fibers

Answer 15

Sympathetic post-ganglionic fibers are adrenergic and secrete norepinephrine (NE) which binds with adrenergic alpha and beta receptors

Question 16

Parasympathetic post-ganglionic fibers

Answer 16

Parasympathetic post-ganglionic fibers are cholinergic and secrete Ach which binds with muscarinic receptors on the effector’s cells

Question 17

Parts of a Neuron

Answer 17

Cell Body-Provide protein molecules (neurotransmitter), which are packaged into vesicles

Dendrites-Branch off the cell body and receive nerve signals and transmit them towards the cell body

Axon-Conducts nerve impulses away from cell body. Terminates in synaptic knob. Cover with a thin fatty layer known as a myelin sheath.

Synapse-Where nerve signals are transmitted either chemically or electrically

Question 18

Functional Region of a Neuron

Answer 18

• Input Zone-*Dendrites and cell body
• Summation Zone-*Axon Hillock
• Conduction Zone-*Axon
• Output Zone-*Synaptic Knobs of axon

Question 19

Membrane Potential

Answer 19

Slight positive charge on outside of membrane, compared to the inside of the cell with the different in positive and negative energy resulting in potential energy

Question 20

Resting Potential

Answer 20

Resting potential (-70 mV) is maintained via non-conducting membrane

The slight excess of positive ion on the membrane’s outer surface is produced by ion transport and the membrane’s permeability characteristics

Some K channels will be open at resting membrane allowing K to diffuse down the concentration gradient (out of the cell), and add to the excess of positive ions on the outer surface of the plasma membrane.

Diffusion of Na in the opposite direction would counteract this effect by is prevented due to the closed Na channels

Question 21

Sodium Potassium Pump

Answer 21

Active transport mechanism in plasma membrane that transports Na and K ions in opposite directions and at different rates (3 NA out and 2 K in)

Maintains an imbalance in the distribution of positive ions resulting in the inside surface becoming slightly negative compared with the outer surface

Question 22

Action Potential Sequence

Answer 22

1. Adequate stimulus to trigger the opening of Na channels, allowing Na to diffuse rapidly into the cells producing local depolarization
2. As threshold potential is reached voltage gated Na channels open and more Na enters the cell causing further depolarization
3. After peak of action potential is reached the membrane will move back towards resting as when K⁺ channels open, allowing outward diffusion of K⁺; process is known as repolarization.
4. Brief period of hyperpolarization occurs, before the resting membrane potential is restored by the Na-K pumps.
5. The reversal in polarity causes electrical current to flow between the site of the action potential and the adjacent regions of membrane and triggers voltage-gated Na⁺ channels in the next segment to open; this next segment exhibits an action potential.
6. This cycle continues to repeat.

Question 23

Refractory Period

Answer 23

The action potential never moves backward because of the refractory period.

In myelinated fibers, action potentials in the membrane only occur at the nodes of Ranvier; this type of impulse conduction is called saltatory conduction.

Question 24

Absolute Refractory Period

Answer 24

Brief period during which a neuron will not respond to a stimulus, no matter how strong

Question 25

Relative Refractory Period

Answer 25

Time when the membrane is repolarized and restoring the resting membrane potential; will respond only to a very strong stimulus

Question 26

Synaptic Transmission Sequence of Events

Answer 26

1. Action potential reaches a synaptic knob, causing calcium ions (Ca⁺⁺) to diffuse into the knob rapidly
2. Increased Ca⁺⁺ concentration triggers the release of neurotransmitter by exocytosis
3. Neurotransmitter molecules diffuse across the synaptic cleft and bind to receptor molecules, causing ion channels to open
4. Opening of ion channels produces a postsynaptic potential, either an excitatory postsynaptic potential or an inhibitory postsynaptic potential
5. The neurotransmitter’s action is quickly terminated by neurotransmitter molecules being transported back into the synaptic knob (reuptake) and/or metabolized into inactive compounds by enzymes and/or diffused and taken up by nearby glia

Question 27

Acetlycholine

Answer 27

Acetylcholine is deactivated by acetylcholinesterase, with the choline molecules being released and transported back to presynaptic neuron to combine with acetate.

Present at various locations, sometimes in an excitatory role and other times inhibitory.

Question 28

Amines

Answer 28

Amines: Dopamine, Norepinephrine, serotonin, histamine

Synthesized from amino acid molecules.

Two categories: monoamines and catecholamines

Found in various regions of the brain, affecting learning, emotions, motor control.

Question 29

Amino Acids

Answer 29

Amino acids: Glutamate, Gaba

Believed to be among the most common neurotransmitters of the CNS.

In the PNS, amino acids are stored in synaptic vesicles and used as neurotransmitters.