Psy6105: Bio_O'callaghan_2/14/12_Lecture 4

Front 1

Action Potential

Back 1

Brief, but extremely large flip in the polarity of an axon's membrane
• Lasts about 1ms
• Voltage suddenly reverses, inside becomes positive, then abruptly reverses again and resting potential is restored.

Front 2

Threshold Potential

Back 2

When electrical stimulation produces a large graded potential that causes the membrane's potential to depolarize to Threshold Potential at about -50mV

Front 3

Depolarization Phase

Back 3

Na+ influx (sodium comes in)

Front 4

Hyperpolarization Phase

Back 4

K+ efflux (potassium goes out)

Front 5

Absolutely Refractory

Back 5

When the axon membrane is stimulated during the depolarizing or repolarizing phases of the action potential, it does not respond with a new action potential - the axon in this phase is called Absolutely Refractory (fig 4.19)

Front 6

Relatively Refractory

Back 6

If the axon membrane is stimulated during the hyperpolarization phase, a new action potential can be induced, but only if the intensity of stimulation is higher than that which initiated the first action potential (fig 4.19)

Front 7

Poisoning of the Action Potential

Back 7

Chemicals that can act as poisons or modify behavior through their influence on the electrical and chemical activity of neurons

Front 8

Poisoning of the Action Potential: 2 examples

Back 8

TEA
Tetrodotoxin

Front 9

Nerve Impulse

Back 9

• Induced when a full action potential has moved along the axon
• The propagation of an action potential on the axon membrane.

Front 10

Myelination

Back 10

Insulated axons (fig 4.22)

Front 11

Glial Cells

Back 11

Play a role in enhancing speed of nerve impulses

Front 12

Myelin Sheath

Back 12

• Insulation around an axon created by the Schwann cless in the PNS and the o.. in the CNS
• Insulated axons are Mylelinated

Front 13

Nodes of Ranvier

Back 13

• Uninsulated regions between the mylelinated segments of the axon
• Voltage sensitive ion channels

Front 14

Saltatory Conduction

Back 14

• Jumping of the action potential from one Node of Ranvier to the next
• Increases the rate of transmission of the action potential

Front 15

Diagnosing MS

Back 15

• Degenerative disease
• Attacks the myelin covering of axons
• Hard plaques form in the affected areas and disrupts the flow of neuronal info
• Symptoms: vision disturbances, fatigue, loss of balance, muscle stiffness, short-term memory problems
• Can be diagnosed using MRI

Front 16

Acetylcholine (ACh)

Back 16

• Loewi discovered
• A chemical that communicates a message to inhibit, or slow a frogs heart rate
• Inhibitory in the PNS
• Inhibitory in on organs in the ANS, but excitatory on body muscles

Front 17

Ephinephrine (EP)

Back 17

• Loewi discovered
• A chemical that communicates an excitatory message to speed up frog heart rate
• Excitatory in the SNS

Front 18

Cholinergic Neurons

Back 18

Neurons that release ACh are called Acetylcholine neurons

Front 19

Epinephrine Neurons

Back 19

Neurons that release EP

Front 20

Norepinephrine (NE)/Noradrenaline (NA)

Back 20

Replaces EP as the excitatory neurotransmitter in nonadrenergic neurons

Front 21

Presynaptic Membrane

Back 21

• Membrane on the axon terminal

Front 22

Synaptic Cleft

Back 22

• Space between the axon terminal and the dendrite spine

Front 23

Postsynaptic Membrane

Back 23

• Membrane on the dendritic spine

Front 24

Synaptic Vesicles and Storage Granules

Back 24

• Located inside the axon terminal
• Contain the neurotransmitter

Front 25

Steps in Neurotransmission (Fig. 5.2): 4 Steps

Back 25

1. Transmitter Synthesis and Storage
2. Neurotransmitter Release
3. Activation of Receptor Sites
4. Neurotransmitter Deactivation

Front 26

Steps in Neurotransmission (Fig. 5.2): Step 1 of 4

Back 26

1. Transmitter synthesis and storage
a) Neurotransmitter is created by the cell's DNA; or
b) Building blocks derived from food are imported and stored in the cell
• NT's are then gathered in synaptic vesicles that are stored:
- as storage granules
- attached to the microfilaments in the terminal button
- attached to presynaptic membrane, ready to release a NT into synaptic cleft

Front 27

Steps in Neurotransmission (Fig. 5.2): Step 2 of 4

Back 27

NT Release
• The action potential opens voltage-sensitive calcium channels in the presynaptic membrane
- > Influx of calcium (Ca2+) into the axon terminal
• Incoming calcium ions bind to a chemical - Calmodium
- > A molecular complex then triggers 2 chemical reactions
1. releases vesicles bound to the presynaptic membrane
2. Releases vesicles bound to filaments in the axon terminal
- Vesicles released from presynaptic membrane empty contents into synaptic cleft through exocytosis
- Vesicles from filaments travel to presynaptic membrane and replace vesicles that were previously there

Front 28

Exocytosis

Back 28

Process by which a cell directs the contents of secretory vesicles out of the cell membrane

Front 29

Steps in Neurotransmission (Fig. 5.2): Step 3 of 4

Back 29

Activation of Receptor Sites
• NT travels across the synapse and interacts with the receptors on the target cell
• Type of NT and kind of receptors determine whether the NT will:
- depolarize postsynaptic membrane = excitatory action
- hyperpolarize the postsynaptic membrae = inhibitory action
- initiate another chemical reaction
- create new synapses
- bring about other changes in the cell

Front 30

Autoreceptors

Back 30

Receptor on the presynaptic membrane that the NT can interact with

Front 31

Steps in Neurotransmission (Fig. 5.2): Step 4 of 4

Back 31

NT Deactivation
• Removal of the NT from the synapse after it has done its job
• Occurs through
- diffusion away from the synapse
- Enzymatyic degradation
- Reuptake into the axon terminal
- glial cell up take: further degrade NT into parts and may export NT or its parts back to axon terminal for reuse

Front 32

Excitatory Synapses - Type I

Back 32

• Typically located on the shafts or spines of dendrites
• Round synaptic vesicles
• Denser pre- and postsynaptic membranes
• Synaptic cleft is wider
• Larger active zone

Front 33

Inhibitory Synapses - Type II

Back 33

• Typically located on the cell body
• Flattened synaptic vesicles

Neurons divided into two zones:
• Excitatory dendritic tree
• Inhibitory cell body

Front 34

Two Types of Synapses:

Back 34

Excitatory Synapses - Type Inhibitory Synapses - Type II

Front 35

What do these two types of synapses do?
(1:20 on recorder)

Back 35

Enhance or lessen the probability...???

Front 36

Identifying NT's:
Four Criteria
(Know this!)

Back 36

1. Chemical must be synthesized in or be present in the neuron
2. Chemical must be released when the neuron is active and produce a response in some target
3. The same response must be obtained when the chemical is experimentally placed on the target
4. A mechanism for deactivatiing the chemical must exist

Front 37

Putative Transmitter

Back 37

A chemical is suspected to be a NT but has not yet met all the 4 criteria.

Front 38

Three classes of NT's

Back 38

• Small-Molecule Transmitters
• Peptide Transmitters
• Transmitter Gases

Front 39

Small Molecule Transmitters

Back 39

• Small orgain molecules
• Synthesized and mackaged in axon terminals
• When it is released from axon terminal, it can be quickly replaced at presynaptic membrane
• Derived from the foods we eat - can be influenced by diet
• Act quickly

Front 40

Small Molecule Transmitters:
• ACh

Back 40

ACh
• Made up of 2 enzymes

Front 41

Small Molecule Transmitters:
• Amines

Back 41

Amines
• Chemicals that contain an amine group, NH, in their structure
• KNOW THIS!!! Dopamine: involved in coordinating movement, attention, learning, behaviors that are reinforcing
Norepinephrine & Epinephrine excitatory transmitters in the mammalian and reptilian heart

Front 42

Small Molecule Transmitters:
• Amines continued

Back 42

• Rate limiting factor
- amount of TH inthe body is limited
- L-Dopa can be used to bypass the rate limiting factor (used in Parkinson's)
• Seratonin (5-HT)
- regulate mood, aggression, appetite, arousal, pain, and respiration
- derived from typtophan

Front 43

Small Molecule Transmitters:
• Amino Acids

Back 43

Glutamate
• Main excitatory transmitter
GABA
• Main inhibitory transmitter
Glutamate and GABA: "Workhorses of the nervous system;" Most common NT's in our body (KNOW THIS!!!)
• Glycine
- Inhibitory, common in brainstem and spinal cord
• Histamine
- Control of arousal and waking
- Constriction of smooth muscles, when activated in allergic reactions, contributes to asthma - constriction of the airways

Front 44

Neuropeptides

Back 44

Multifunctional chains of amino acids made by the cell's DNA

Front 45

Peptide Transmitters

Back 45

• Serve as hormones (growth hormone)
• Active in response to stress (corticotropin)
• Encourage mother-child bonding (ocytocin)
• Facilitate learning (glucogen-like peptide)
Regulate eating and drinking (cholecystokinin & vasopressin)
• Respond top pleasure and pain (beta-endorphin)

Front 46

Peptide Transmitter:
Active in response to stress:

Back 46

Corticotropin

Front 47

Peptide Transmitter:
Encourage mother-child bonding:

Back 47

Ocytocin

Front 48

Peptide Transmitter:
Facilitate learning:

Back 48

Glucogen-like peptide

Front 49

Peptide Transmitter:
Regulate eating and drinking:

Back 49

Cholecystokinin & Vasopressin

Front 50

Peptide Transmitter:
Respond to pleasure and pain:

Back 50

Beta-endorphin

Front 51

Transmitter Gases

Back 51

• Synthesized as need by the cell
• Can be produced in many regions of the cell
• After production diffuse away from the cell
• Nitric Oxide (NO)
• Carbon Monoxide

Front 52

Nitric Oxide (NO)

Back 52

• Serves as a messenger in many parts of the body
• Controls muscles in intestinal walls
• Dilates blood vessels in the brain and in the genital organs
Viagra - Enhances NO function

Front 53

Excitatory and Inhibitory Receptor Effects

Back 53

• No one NT is assoc. with a single kind of receptor or a single type of influence,
• A NT can bind to either ionotropic or metabolic receptors, which will result in either an excitatory or inhibitory effect on target cell, respectively.
• Ex. ACh has an excitatory effect on skeletal muscles where it activates an ionotropic receptor; has an inhibitory effect on the heart where it activates a metabotropic receptor.

Front 54

Neurotransmission in the PNS

Back 54

Motor neurons = Cholinergic neurons
• Primary NT is ACh
• Also use Calcitonin-gene-related-peptide (CGRP)
- increases force of muscle contraction

Front 55

Neurotransmitters in the PNS:
ANS - Parasympathetic division

Back 55

Cholinergenic neurons from the CNS synapse on cholinergenic neurons in the ANS to prepare body's organs to rest and digest.

Front 56

Neurotransmission in the PNS:
ANS - Sympathetic division

Back 56

Collinergenic neurons from the CNS synapse on noradrenergic neurons in the ANS to prepare body's organs for fight or flight
(See fig 5.1)

Front 57

Neurotransmitter in the CNS:

Back 57

• Some specific behaviors
- Ex. Endorphins, Oxytocin
• GABA and glutamate (small-molecule transmitters)
- Maintain arousal levels, vegitative behaviors
- Most common NT in brains of all animals
• Activating Systems
- System of neurons that coordinates wide areas of the brain to act in concert (small-molecule transmitters)
- Acetycholine
- Dopamine
- Norepinephrine
- Seratonin

Front 58

Neurotransmission in the CNS:
Some specific behaviors

Back 58

Examples: Endorphins, Oxytocin

Front 59

Neurotransmission in the CNS:
GABA & Glutimate (small-molecule transmitters)

Back 59

• Maintain arousal levels, vegetative behaviors
• Most common NT in the brains of all animals

Front 60

Neurotransmission in the CNS:
Activating systems

Back 60

• System of neurons that coordinates wide areas of the brain to act in concert (small-molecule transmitters)
- Acetylcholine
- Dopamine
- Norephineprine
- Seratonin

Front 61

Activating Systems

Back 61

• Cholinergic (ACh); Dopaminergic (dopamine); Noradrenergic (nonadrenaline); Serotonergic (seratonin)
• Cell bodies located in the brainstem, axons distributed throughout the brain
• Imaging can be used to identify location and organization of the systems

Front 62

Activating Systems:
Cholinergic System

Back 62

• Normal waking behavior and memory
• Degenerates during Alzheimer's disease (KNOW THIS!!!)

Front 63

Activating Systems:
Dopaminergic System

Back 63

• Nigrostriatial Pathway - Movement
• Mesolimbic Pathway

Front 64

What is the Nigrostriatial Pathway?

Back 64

Part of the Dopaminergic System:
• Nigrostriatial Pathway - Movement
- Degenerates during Parkinson's diease (KNOW THIS!!!)

Front 65

What is the Mesolimbic Pathway?

Back 65

Part of the Dopaminergic System:
• Affected by addictive drugs
• Produces pleasure
• Excessive dopamine may lead to Schizophrenia

Front 66

Activating Systems:
Noradreneric System

Back 66

• Learning and emotions
• Decreases may lead to major depression
• Increases may lead to mania

Front 67

Test Study
• Know terms for matching (20-30)
• Multiple choice (60-70)
• Labeling (rostral/caudal, know both terms

Back 67

except for different synapses
no cranial nerves
• Know terms for matching (20-30)
• Multiple choice (60-70)
- glial cells
- resting potential
- 4 steps
- what are the ions involved in resting potential/action potential
- know all brain structures
- know all diseases/disorders
- know fig. 5.17
• Labeling: fist & slide of guys head

Front 68

Activating Systems:
Serotonergic System

Back 68

• Waking pattern, learning, emotion
• Decreases are related to depression
• Increases are related to schizophrenia, OCD and sudden infant death syndrome