AAP Nervous System 2

Question 1

What is the voltage across the neuronal membrane when a neuron is at rest?

Answer 1

• -60 to -70 mV

- this is called resting membrane potential

Question 2

Distribution of ions across cell membrane

Answer 2

• the voltage difference between the 2 sides of the cell mbn in a neuron is largely due to distribution of different ions on the two sides of the membrane
• in the resting state, the outside has more positive charges
• the inside has more negative charges

Question 3

What is the membrane current?

Answer 3

• membrane current is known as the flow of ions (electrical charge) across the membrane
• there are ion channels located at the cell membrane
• ions such as sodium & potassium flow through the ion channels

Question 4

Types of ion channels

Answer 4

• Voltage-gated ion channels: open/close in response to the change in membrane potential(voltage)
• Ligand-gated ion channels: open/close in response to chemical binding (e.g. hormone, neurotransmitter)

Question 5

Depolarization

Answer 5

• redistribution/flow of ions across the cell membrane will increase/decrease the membrane potential
• the increase in the membrane potential (the inside becomes less negative, e.g. -70 becomes -20) is called depolarization
• depolarization leads to the activation of the neuron which increases the probability to fire

Question 6

Hyperpolarization

Answer 6

• decrease in membrane potential )the inside becomes more negative) is called hyperpolarization
• hyperpolarization leads to the inhibition of the neuron which decreases the probability to fire

Question 7

Action Potential

Answer 7

• depolarized neurons generate the electrical impulse travelling along the axon which is known as action potential or “spike”
• AP is mainly due to the flow of NA+ into the cells (through voltage-gated sodium channels)

Question 8

Repolarization

Answer 8

• the return of membrane potential from depolarized stage towards resting membrane potential (potassium ions flow out)

Question 9

What are the two major types of voltage-gated channels involved in the generation of action potential?

Answer 9

• sodium channels

- potassium channels

Question 10

Conduction of action potential along the axon

Answer 10

• As the axon is wrapped by myelin intermittently, the sodium channels are blocked by the myelin sheath
• therefore, action potential can only be generated in the gaps between the adjacent myelin sheath
• the gap between the myelin sheath is known as the nodes of Ranvier which is the area that the ion channels are not covered
• The ions (sodium and potassium) can flow through the membrane in the areas
• new action potential is always generated at the Ranvier node
• conduction of action potential along an axon is like “jumping” from one node of Ranvier to the next

Question 11

Conduction of action potential between the neurons (at a synapse)

Answer 11

• when an action potential reaches the axon terminal, neurotransmitter (NT) is released from the axon terminal
• NT is a molecule generated by a neuron
• the receptors on the dendrite of the next neuron are stimulated by the NT, leading to the excitation of the next neuron
• a new action potential would be generated in the next neuron

Question 12

What are the types of neurotransmitters?

Answer 12

• excitatory neurotransmitters: usually cause an influx of sodium so that the neurons will be depolarized (inside of cell more positive)
• inhibitory neurotransmitters: cause entry of chloride ions which leads to hyperpolarization (make inside of cell more negative)

Question 13

Common neurotransmitters that are excitatory NT

Answer 13

• Acetylcholine
• Catecholamines (Norepinephrine & Epinephrine)
• Dopamine
• Serotonin (5-HT)
• Glutamate

Question 14

Common inhibitory NTs

Answer 14

• gamma-aminobutyric acid (GABA)

- glycine

Question 15

What are the regions of the brain?

Answer 15

• cerebrum (cerebrum cortex)
• Diencephalon: thalamus & hypothalamus
• Brain stem: Midbrain, Pons, Medulla oblongata
• Cerebellum

Question 16

What is the brain ventricle?

Answer 16

• empty space below the cerebrum
• filled by fluid known as Cranial Spinal Fluid (CSF)
• continue at the back with spinal channel/spinal cavity

Question 17

How many pairs of spinal nerves are there in dogs?

Answer 17

-36 pairs of spinal nerves

Question 18

Cortex

Answer 18

• highly developed into different functional areas, especially in higher species
• the surface area of cortex in higher species is much larger than that of the lower species due to folds/gyrus

Question 19

What are the different areas of the cortex that have different functions?

Answer 19

• sensory areas: responsible for receiving and processing sensory information coming from the body
• motor areas: initiates/coordinates motor activity in the muscles
• auditory areas: receives hearing information from the ears
• visual areas: receive visual information from eyes
• higher functional areas (e.g. prefrontal cortex): solving complex tasks

Question 20

What does the cerebrum do?

Answer 20

• controls most key functions in the body: conscious activities, intelligence, memory, language, muscle movement

Question 21

What does the cerebellum do?

Answer 21

• area of the brain responsible for coordination of movement, balance, posture
• if the cerebellum is injured, movements become jerky

Question 22

What is the brain stem?

Answer 22

• consists of the medulla oblongata, pons and midbrain
• brain stem is responsible for vital life functions such as breathing, heartbeat, and blood pressure
• many of the cranial nerve pairs originate from the brain stem

Question 23

What is the diencephalon?

Answer 23

• key components below the cortex
• relay station between brain stem and cerebrum
• thalamus: acts as a relay station for sensory inputs to the cerebrum
• hypothalamus: interface between the nervous system and the endocrine system

Question 24

What are meninges?

Answer 24

• coverings of the brain and spinal cord
• three layers
• dura mater (surface): double-layered external covering below the bone of skull
• Arachnoid layer: middle web-like layer
• Pia mater: internal layer (blue)

Question 25

Cerebrospinal fluid (CSF)

Answer 25

• the composition of CSF is similar to blood plasma

- circulated in brain ventricles and spinal cavity in arachnoid space (space below the arachnoid layer)

Question 26

What are the functions of CSF?

Answer 26

• primary function is to cushion the brain within the skull and serve as a shock absorber for the central nervous system
• also circulates nutrients and chemicals, removes waste products from the brain and spinal cord

Question 27

How many cranial nerve pairs are there?

Answer 27

• 12 nerve pairs that originate directly from the brain stem

- each nerve may contain axons of motor neurons, axons of sensory neurons, or combinations of both

Question 28

State the names and the functions of the cranial nerves.

Answer 28

I: olfactory --> smell
II: optic --> sight
III: oculomotor --> moves eye, pupil
IV: trochlear  --> moves eye
V: trigeminal --> face sensation
VI: abducens --> moves eye
VII: facial --> moves face, salivate
VIII: vestibulocochlear --> hearing, balance
IX: glossopharyngeal --> taste, swallow
X: vagus --> heart rate, digestion
XI: accessory --> moves head
XII: hypoglossal --> moves tongue

Question 29

What is a reflex?

Answer 29

• an involuntary and nearly instantaneous movement/response to a stimulus
• a reflex is made possible by neural pathways called reflect arcs which are organized at the spinal cord level without involvement of brain
• protects the body against potential damage by its fast response, due to the short neuronal circuit involved

Question 30

Neuronal circuit involved in reflex

Answer 30

• sensory neuron forward sensory information to spinal cord via dorsal nerve root
• motor neurons located in spinal cord forward information to muscle (effectors)

Question 31

What does a reflex arc consist of?

Answer 31

• receptor (nerve endings)
• sensory neuron
• spinal cord
• motor neuron
• effector (muscles pulling back the hand

Question 32

Examples of relfex

Answer 32

• patella reflex: tapping the patella (ligament) results in extension of the leg due to muscle contraction
• Corneal reflex: gentle touch of the cornea results in reflex closure of the eyelids
• pupillary light reflex: constriction of pupil in response to shining light

Question 33

Review and identify pictures in anki

Answer 33

all done!