Chap. 44 The Nervous System

Front 1

Path of nerve impulses
5

Back 1

Sensory cell (affector) → Sensory neuron (PNS) → Interneuron (CNS) → Motor neuron (PNS) → Muscle or gland (effector)

Front 2

Parts of the neuron
9

Back 2

1) Dendrites
2) Soma
3) Axon hillock
4) Axon
5) Terminal buttons
6) Myelin sheath
7) Schwann cells (PNS)
8) Oligodendrocytes (CNS)
9) Nodes of Ranvier

Front 3

Axon hillock

Back 3

• where the soma meets the axon
• where a graded potential either dies out or becomes a threshold potential to continue down axon

Front 4

Are all axons myelinated?

Back 4

No, only those that need to send impulses quickly

Front 5

Glial cells
Percentage
4 types

Back 5

Supportive cells that make up 90% of the nervous system, while the other 10% are neurons

1) Astrocytes
2) Microglia
3) Oligodendrocytes
4) Schwann cells

Front 6

Astrocytes
2

Back 6

• in contact with the capillaries of the brain
• reduce the permeability of the blood brain barrier

Front 7

Microglia

Back 7

Turn into macrophages and eat injured neurons or microbes

Front 8

Oligodendrocytes
Schwann cells

Back 8

Oligodendrocytes
• Make up the myelin sheath in the CNS
• 1 oligodendrocytes has extensions which insulate many axons

Schwann cells
• Make up the myelin sheath in the PNS

Front 9

Multiple schlerosis
Type of disease
Cause
What happens
Effect

Back 9

• an autoimmune disease
• blood-brain barrier isn't working efficiently, allowing T-cells into the nervous system
• T-cells attack the myelin sheath, leaving hard scar tissue
• impulse transmission impeded = loss of muscle control

Front 10

Tay Sachs
Type of disease
Cause
What happens
Effect

Back 10

• a recessive lethal disorder
• a gene that codes of enzyme metabolism is mutated
• fat builds up in the nodes of ranvier so that saltatory conduction is impeded
• leads to death

Front 11

Na+ / K+ pump
When is it activated? (1)
What is the result of this? (3)

Back 11

• Active while neuron is at rest
• 3 Na+ are transported out of the cell
• 2 K+ are transported into the cell
• The cytosol is negatively charged (less +) compared to highly positively charged ISF

Front 12

Permease

Back 12

Carrier protein of the Na+ / K+ pump

Front 13

Voltage
2

Back 13

• Potential difference of a concentration gradient
• The greater the potential difference, the more potential energy (free energy) to do useful work

Front 14

Ohm's Law
Equation
What the variables are in terms of neurons & impulses

Back 14

V = IR

V = voltage = potential difference
I = current = flow of electric charge = Na+ ions
R = resistance to current = cell membrane

Front 15

What is the source of resistance in neurons?
What happens when its high?

Back 15

Resistance is the closed ion channels

When resistance is high, current is low

Front 16

Polarized vs. depolarized membranes
Charges
When?
Due to...

Back 16

Polarized
• outside cell is + and inside cell is -
• when cell is at rest → resting potential
• due to K+ channels and Na+ / K+ pump

Depolarized
• charges flip; outside cell is - and inside cell is +
• when cell is at action potential
• due to impulse opening Na+ and K+ channels

Front 17

4 types of potentials for neurons and their values

Back 17

1) Resting = -70 mV
2) Graded = vary
3) Threshold = -50 mV
4) Action = +60 mV

Front 18

Resting potential
3

Back 18

• -70 mV
• when the cell is at rest
• cell is polarized (cytosol - and ISF +)

Front 19

What contributes to the charges of the resting potential
3

Back 19

1) Na+ / K+ pump
2) Cl- add to negative charge inside cell
3) Anionic proteins inside cytosol

Front 20

Graded potentials

Back 20

• short lived electrochemical impulses
• they will either die out at the axon hillock, or build up to an action potential and travel down the axon

Front 21

Threshold potential

Back 21

• -50 mV
• The minimum amount of stimulus needed for a nerve to depolarize and fire
• leads to the action potential

Front 22

Action potential

Back 22

• + 60 mV
• depolarization of neuron's membrane
• sets off a chain reaction, opening Na+ ion channels all the way down the axon

Front 23

How is an impulse passed down an axon once an action potential has been reached?
3

Back 23

• One region of the neuron's axon is depolarized and produces an action potential
• this stimulates depolarization of the next region
• this repeats until the length of the axon is traveled

Front 24

What is the mechanism of depolarization and repolarization?
4

Back 24

• Depolarization: Na+ channels open for Na+ to flow into the cell where K+ resides
• charges are now reversed: inside is positive and outside is negative
• Repolarization: K+ ion channels open and K+ flows out of cell, hyperpolarizing membrane to extreme values of resting potential charges
• BUT concentration gradients of Na+ / K+ are reversed, so the pump must return gradients to their original make ups

Front 25

Hyperpolarization
3

Back 25

• -80 mV
• the repolarizating of the membrane by K+ rushing out of cell produces an "undershoot"
• temporary state of greater negativity than is normal for the resting potential (-70 mV)

Front 26

Saltatory conduction
2

Back 26

• Na+ channels are only located at Nodes of Ranvier
• depolarization of one node quickly spreads under the myelin sheath to open the channels of the next node
• the impulse appears to jump because of the distance between the Na+ channels

Front 27

3 types of neurons
Examples

Back 27

1) Bipolar = visual and olfactory sensory cells
2) Psudounipolar / unipolar = sensory neurons (in ganglia)
3) Multipolar = interneurons and motor neurons

Front 28

Bipolar neurons
Which neurons
Structure

Back 28

• Sensory cells of the eye retina (cones and rods) and olfactory cells
• One dendrite → soma → one axon forming straight line

Front 29

Psudounipolar / unipolar
Which neurons
Structure (2)

Back 29

• sensory neurons
• somas are in ganglia of the PNS
• Structure:
1) Peripheral process = receiving end extending into PNS
3) central process = sending end extending into spinal cord (CNS)

Front 30

Multipolar neurons
Which neurons
Structure (2)

Back 30

• Motor neurons and interneurons of the CNS
• Many dendrites connecting to many terminal buttons
• but one long axon

Front 31

Functions of:
Sensory neurons
Interneurons
Motor neurons

Back 31

Sensory neurons = afferent neurons which pick up transduced electrochemical signals from the sense cells

Interneurons = Make up the CNS and integrate incoming info from sensory neurons

Motor neurons = efferent neurons; send signal to muscles and glands

Front 32

Tract
What
Where (which matter)
Function
Equivalent to...

Back 32

• A group of neuron axons wrapped in connective tissue
• In the white matter of the CNS
• Fxn = for signal transmission
• Equivalent to nerves in the PNS

Front 33

What is grey matter of the brain and spinal cord?
What is the white matter?

Back 33

Grey matter = axons

White matter = dendrites and soma

Front 34

Synapses
What
3 locations
2 types

Back 34

Connections between neurons

Locations:
1) axo-dendritic
2) axo-somatic
3) neuromuscular

2 types:
1) Electrical
2) Chemical

Front 35

Electrical synapse
4

Back 35

• Targets organs that always have to stay on; eg. heart and digestive tract
• pre-synaptic and post-synaptic neurons are physically connected by gap junctions
• no synaptic cleft or neurotransmitters involved
• action potentials are continuous from one neuron to next

Front 36

Chemical synapse

Back 36

• Has a synaptic cleft and involves neurotransmitters
• Action potential causes Ca+2 to open for the ions to enter pre-synaptic neuron
• Ca+2 cause synaptic vesicles to release their nt's into cleft to either excite or inhibit the post-synaptic neuron

Front 37

Excitatory vs. inhibitory neurotransmitters

Back 37

Excitatory = bind to and open Na+ channels for the ion to rush into post-synaptic neuron and cause an excitatory post-synaptic potential (action potential)

Inhibitory = bind to and open K+ channels for the ion to rush out of cell to cause hyperpolarization

Front 38

Cranial nerves vs. spinal nerves
How many pairs
Contain which types of neurons?
Function

Back 38

Cranial:
• 12 pairs
• contains sensory neurons
• for input and output to and from the brain

Spinal:
• 31 pairs
• contains both sensory and motor neurons
• carries info to and from the periphery of the body

Front 39

What develops into the nervous system in embryonic development?

Which ends of it develops into which parts of the nervous system?

Back 39

The neural tube aka nerve cord

Anterior end develops into the brain
Caudal end develops into the spinal cord

Front 40

Ventricles of the brain

Back 40

• Hollow chambers filled with CSF
• are continuous with the central canal of the spinal cord

Front 41

1st level of brain development
What (1) develops into what (3)?

Back 41

Anterior end of the nerve cord develops into:
1) Forebrain (face)
2) Midbrain
3) Hindbrain (back of head)

Front 42

The forebrain developments into...
2

Use tricks to remember =)

Back 42

1) Telencephalon = cerebrum
2) Diencephalon = thalamus and hypothalamus

Hint 42

T for top, cerebrum is top of brain
Di for 2, diencephalon develops into the TWO structures which are in cerebrum (kinda?)

Front 43

The midbrain developments into...
1

Use tricks to remember =)

Back 43

Mesencephalon = corpora quadrigemina

Hint 43

Mesa = steep sides! = use reflexes to not fall = corpora quadrigemina for reflex response

Front 44

The hindbrain developments into...
2

Use tricks to remember =)

Back 44

1) Metenchephalon = cerebellum and pons
2) Myelencephalon = medulla oblongata

Hint 44

Met like metronome = keeps rhythm for music = pons keeps rhythm of breath
Met like meter = meter scale should be balanced = cerebellum for balance

Myel like myelin sheath for speeding rate of impulses = medulla oblongata for rate (speed) of breathing

Front 45

2 divisions of the efferent component of the PNS
Which neuron is BOTH composed of?
Definitions

Back 45

Both composed of motor neurons

1) Somatic division
• under voluntary control
• carry signals from CNS to skeletal muscle

2) Autonomic division
• involuntary
• signals sent to smooth muscle, cardiac muscle, and glands
• split into the sympathetic and parasympathetic nervous systems

Front 46

Sympathetic division of the autonomic nervous system
Dominates during...
Results in (5)

Back 46

• Dominates during stress, anger, excitement, or strenuous activity
• Results in fight or flight:
1) Blood directed to muscles
2) increases heart rate, BP, & metabolism
3) Dilated pupils & bronchi
4) Releases cortisol which decreases immunity
5) Decreases activity of digestive system

Front 47

Parasympathetic division of the autonomic nervous system
Dominates during...
Results in (2) --- hint

Back 47

• Dominates during non-stressful situations, relaxing, eating
• Results in rest and digest:
1) Blood directed to digestive system
2) Decreases heart rate and bp

Connection: Decreased heart rate and BP contributes to why you get tired after eating a lot

Hint 47

connection between results and sleepiness

Front 48

Which are the 2 main structures that protect the brain and spinal cord?

Back 48

1) Meninges = 3 layers of CT that surround and cushion the brain and spinal cord

2) Cerebral spinal fluid (CSF) = nourishes CNS by circulating around and through ventricles of brain and central canal of spinal cord

Hint 48

Mininges and CSF
What are they / what do they do?

Front 49

Spinal cord
Function
2 types of matter and what they're composed of

Back 49

• Fxn = carries impulses between brain and PNS
• Grey matter = consists of somas and dendrites
• White matter = consists of axons

Front 50

Mechanism of reflexes
3

Back 50

1) One interneuron stimulates a motor neuron to contract a flexor muscle
2) A second interneuron stimulates a motor neuron to relax an extensor muscle
3) Other interneurons send signals to brain to let you know what happened - delayed rxn

Hint 50

Involves multiple interneurons

Front 51

Hindbrain consists of
Brainstem consists of

Back 51

Hindbrain:
1) Cerebellum
2) Medulla
3) Pons

Brainstem:
1) Midbrain
2) Medulla
3) Pons

Front 52

Cerebellum
Fxn
Receives input from receptors in (5)
Input tells brain (3)

Back 52

• For proprioception = balance
• Receives input from receptors in muscle, semicircular canals, touch, vision, hearing
• Input tells brain:
1) Orientation in space
2) Degree of muscle contraction
3) Which limbs are moving

Hint 52

Doesn't receive input from taste and smell

Front 53

Proproception

Back 53

Balance

Front 54

Telencephalon
AKA
Composition of grey and white matter

Back 54

• AKA cerebrum
• Made up of:
1) Cerebral cortex = grey matter
2) White matter
3) Deep grey matter

Front 55

Lateralization of the 2 hemispheres of the brain
4

Back 55

• Each hemisphere of the brain responds to sensory info from the opposite side of the body
• Hemispheres joined by the corpus collosum tract to coordinate their functioning
• Right hemisphere = intuitive thinking and artistic abilities
• Left hemisphere = mathematical and analytical thinking

Front 56

Grey matter of the brain
What occurs here
Structures located here (4)

Back 56

Where thinking occurs in the brain

Consists of:
1) At the periphery: cerebral cortex

Deep in brain:
2) Thalamus
3) Hypothalamus
4) Basal nuclei

Front 57

Cerebral cortex
What
Function
Divisions & their fxns (4)

Back 57

• Highly folded grey matter → soma and dendrites
• "Higher centers of the brain" where all higher thought processes occur
• Divided into the 4 lobes:
1) Frontal = motor skills
2) Parietal = somatosensory area → touch, temp, pressure, etc.
3) Temporal = auditory & smell; associated w/ olfactory bulb
4) Occipital = visual cortex

Hint 57

Frontal = in front to be on point ex. good HAND-eye coordination

Parietal = parent's loving touch

Temporal = near ears for hearing; closest to olfactory bulb

Front 58

Thalamus
3

Back 58

• In grey matter deep in brain
• Switch board that sends signals from spinal cord to rest of brain
• Filters information to prevent info overload

Hint 58

Can't remember b/c there's too much info

Front 59

Reticular formation

Back 59

Neurons in the brain stem that convey signals from spinal cord to thalamus

Hint 59

Reticulum = a network = conveys info

Front 60

Hypothalamus
Where
What
Contains what other structure?

Back 60

• In grey matter deep in brain
• Only part of brain unprotected by the blood-brain barrier b/c it has to "taste" the blood to see which hormones are needed
• contains the suprachiasmatic nucleus → regulates circadian rhythm

Front 61

Basal nuclei
3

Back 61

• In grey matter deep in brain
• surrounds thalamus on each side
• manages intensity of voluntary movements (smooths out muscle movements)

Hint 61

Nuclei = groups of somas = neurons

Think acts in conjunction with motor neurons

Front 62

Blood-brain barrier
What can (7) and can't pass (3) through
What 2 things add to the protection

Back 62

• Prevents toxins, microbes, and other irritants from entering CNS
• Glucose, amino acids, alcohol, ions, O2, CO2, medications for depression can diffuse through

1) Capillaries in CNS contain tight junctions between cells
2) Astrocytes wrap around capillaries an reduce permeability

Front 63

Limbic system
What
Where
Includes (3)

Back 63

• Reward and emotional center of brain
• Located in grey matter
• Includes:
1) Amygdala = memory triggers which elicit present-day reactions
• routs info to the hippocampus
2) Hippocampus = memory center
3) Olfactory bulb

Hint 63

Amygdala
Hippocampus
Olfactory bulb

Functions of each

Front 64

Wernicke's area
Location
Function
Damage causes...

Back 64

• Boardering temporal and parietal lobes
• Fxn = integrates info from visual, auditory, and somatosensory area (parietal lobe) to:
1) Understand language
2) Speak
3) Write

Lesions lead to no comprehension

Front 65

Broca's area
Location
Function
Damage causes

Back 65

• In frontal lobe
• Fxn = sends signals to motor area (frontal lobe) to move tongue, lips, jaw to speak
• Lesions lead to comprehension but can't speak