ANPS Block 2

What types of cells make up the nervous system?

1. neurons

2. glial cells/neuroglia

what is the ratio between neurons and neuroglia in the body?

1:1

Neuron

main structural and functional unit of the nervous system (information processing)

about 50% of the cells in the nervous system are ______

neurons

glial cells/neuroglia

• carry out diverse functions (i.e. providing support for neurons)

• 4 types

4 types of glial cells?

1. astrocytes

2. microglia

3. oligodendrocytes

4. Schwann cells

structure of neurons determines ______

function

the ability of the nervous system to process information is dependent on ______

rapid intercellular communication between neurons

anatomy of a neuron: dendrite

information receiving (info from other neurons)

anatomy of a neuron: axon

information transmitting

anatomy of a neuron: axon hillock

part of axon that extends from cell body, where an action potential starts

anatomy of a neuron: cell body (soma)

biosynthetic center of the cell, contains nucleus and other organelles.

anatomy of a neuron: axon terminal

contains neurotransmitters, which are released into the synapse.

when will the axon terminal release neurotransmitters into the synapse?

after the action potential spreads down the axon and reaches the axon terminal

a synapse includes 3 things?

1. presynaptic neuron

2. synaptic cleft

3. postsynaptic neuron

synaptic vesicle is filled with what?

neurotransmitter

receptors for neurotransmitter are on

postsynaptic neuron

4 functions regions of neurons

1. receptive region

2. impulse-generating region

3. conducting region

4. secretory region

receptive region

dendrites and cell body receive signals

impulse-generating region

action potential is generated at the axon hillock (aka trigger zone)

conducting region

action potential travels down axon

secretory region

neurotransmitters are released from axon terminal into synapse

the neuron cell body (soma) is the main site what kind of synthesis?

protein

dendritic spines

tiny extensions on dendrites that increase surface area of plasma membrane

dendritic spines allow for the cell to _______

receive more inputs

how do neurons differ from each other?

• morphology

• function

• gene expression

neuron morphology

multipolar, bipolar, pseudounipolar

most neurons are what morphology?

multipolar

neurofilaments

intermediate (in size) filaments filaments of the neuronal cytoskeleton

axonal transport

• how the cell body communicates with the axon terminal

• bidirectional

2 types of axonal transport

1. anterograde transport

2. retrograde transport

anterograde transport

movement of materials from cell body to axon terminals

retrograde transport

movement of materials from axon terminals to cell body

anterograde transport examples

• neurotransmitters

• new membrane

• mitochondria

• enzymes

• vesicles

retrograde transport examples

• organelles for recycling

• signalling molecules brought in at terminal

• potentially hazardous molecules can be brought into terminals

glial cells

carry out diverse functions, including providing support for neurons

astrocytes

diverse functions, regulation of extracellular space

microglia

immune cells of the nervous system

oligodendrocytes

myelinating cells of central nervous system (CNS)

Schwann cells

myelinating cells of peripheral nervous system (PNS)

vascular cells

make up blood vessels

astrocytes are only found where?

central nervous system

satellite cells

• similar to astrocytes (but not the same)

• found in the peripheral nervous system

what do astrocytes regulate?

the level of chemicals (ex. neurotransmitters) and ions (ex. K⁺) in the environment surround neurons (at nodes of Ranvier and synapses)

astrocytes help to form

blood-brain-barrier

through what process can microglia remove microbes and debris?

phagocytosis

myelination dramatically increases

the speed of electrical signalling in neurons

processes of oligodendrocytes

reach out and wrap lipid-rich myelin around axons of multiple neurons

processes of Schwann cells

wrap lipid-rich myelin around axons of a single neuron

How many Schwann cells wrap around one neuron’s axon?

multiple

ependymal cells

• 5th type of glial cells

• produce cerebrospinal fluid

neurons differ from glia because

• they are excitable cells

• do not divide after developmental period

3 general functions of the nervous system

1. collect sensory input

2. integrate information

3. produce motor output

information is sent to the central nervous system via

sensory division (afferent) of PNS

central nervous system (CNS)

• brain and spinal cord

• integrates information

the CNS stimulates a response by

activating the motor division efferent) of the PNS

somatic motor divison

control of voluntary movement

autonomic (visceral motor) division

alteration of organ function

2 systems of the autonomic division

1. sympathetic nervous system

2. parasympathetic nervous system

sympathetic nervous system

stimulates “fight or flight” response (i.e. increase heart rate and respiratory rate)

parasympathetic nervous system

stimulates “rest and digest” response (i.e. decrease heart rate, increase digestive function)

afferent

• coming IN towards brain

• sensory information

efferent

• going OUT and away from brain

• motor info

a collection of axons in the PNS

nerve

a collection of axons in the CNS

tract

a collection of cell bodies in the PNS

ganglion

a collection of cell bodies in the CNS

nucleus

grey matter

contains cell bodes, dendrites, and axon terminals

white matter

contains myelinated axons

when stimulated, excitable cells can produce an electrical signal called

action potential

ions move across the cell membrane to

carry electrical charge

ions are

electrolytes

ion channel

integral membrane protein that allows ions to pass thru a pore between intra/extracellular environments

gated =

not always open

leakage =

always open

receptor

integral membrane protein that produces a physiological change in a cell after a ligand binds

pores in ion channels are

selectively permeable

selectivity regulates the passage of ions based on

size and charge

ion flow across the membrane will change the

membrane potential

membrane potential

difference in electrical potential between inside and outside of cell

gated ion channels open and close in response to

specific stimuli

gated ion channels control _____ for an ion

permeability

while open, gated channels allow for _____ movement of ions down their gradients

passive

2 types of gated ion channels

1. voltage gated (VG)

2. Chemically (Ligand) gated (LG)

VG ion channels open in response to

a change in membrane voltage

LG ion channels open in response to

binding of a specific extracellular signal (ligand)

what are the ligands that bind to the LG ion channels?

neurotransmitters

examples of VG ion channels

• Na+

• K+

• Ca2+

ionotropic receptors are what type of gated ion channel?

ligand gated

metabotropic receptors are

membrane proteins that respond to an extracellular signal by altering the metabolism in the cell (NOT LIGAND GATED)

ionotropic receptors open ion channels that

allow specific ions to flow into or out of cell

G-protein-coupled receptors

metabotropic receptors that activate a G-protein when neurotransmitter binds

after the G-protein is activated, it can

stimulate intracellular signalling pathways

the response of a metabotropic receptor is ____ but _____

slower but more widespread (and potentially longer lasting)

most neurotransmitters fit into one of two categories

1. small molecule neurotransmitters

2. neuropeptides

small molecule neurotransmitters

1. Glutamate

2. GABA

3. Glycine

Glutamate

• generally excitatory

• principle excitatory neurotransmitter in the brain

GABA

• generally inhibitory

• principle inhibitory neurotransmitter in the brain

Glycine

• inhibitory

• major inhibitory neurotransmitter in spinal cord and brain stem

neuropeptides

small chains of amino acids made in the rER/Golgi at cell body