PY460: Biological Bases of PY460: Biological Bases of Behavior Behavior Chapter 2: Chapter 2: Nerve Cells & Nerve Impulses Nerve Cells & Nerve Impulses • The Cells of the Nervous System The Cells of the Nervous System • The Nerve Impulse The Nerve Impulse
24
Embed
PY460: Biological Bases of Behavior Chapter 2: Nerve Cells & Nerve Impulses The Cells of the Nervous System The Cells of the Nervous System The Nerve Impulse.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
PY460: Biological Bases of BehaviorPY460: Biological Bases of Behavior
Chapter 2:Chapter 2: Nerve Cells & Nerve ImpulsesNerve Cells & Nerve Impulses• The Cells of the Nervous SystemThe Cells of the Nervous System
• The Nerve ImpulseThe Nerve Impulse
Slide 2: The Cells of the Nervous System 2 Basic cell types in the NS
Neurons- receive and transmit electrical and chemical process of transmission
Glia- “glue” multiple functions (discussed later in detail) structural support, waste removal
Numbers Cerebral Cortex
15 billion neurons Cerebellum
70 billion neurons Spinal Cord
1 billion neurons
Slide 3: Parts of the Neuron: On the Outside
Soma- the cell body (.005mm to 1 mm) Cell Membrane (bi-lipid layer[2 fat molecules]) “Protein Channels”control flow of ions in/out of
cell
Dendrites- “tree”- receive incoming messages Synapses- location at which info is received from other
neurons Dendritic Spines- short outgrowths on dendrites-
increase dendrites surface area Axon- long fiber (typically) down which electrical
message (impulse) is sent. Myelin Sheath- fatty insulating material around axon. Presynaptic Terminal (End Bulb)- axon release of
chemical that cross synapse excite next neuron.
Slide 4: Parts of the Neuron: On the Inside
Cytoplasm- viscous fluid in cell Cell Nucleus- “the nut”- area containing genetic material
DNA- long strands of amino acids Chromosomes- strands of DNA. Important in
protein production- (genes are here) Mitochondria-“powerhouse” to cell (aerobic energy) Ribosomes- synthesis on newest building material
(protein for cell) Endoplasmic Reticulum- thin tubes that transport proteins Lysosomes (recycler)- enzymes that break chemicals
into their component parts to be recycled for later use. Golgi Complex- homonal preparation for secretion
Sensory Neurons- highly sensitive and specialized to receive a particular stimulus (wavelength of sound, light, type of touch);sends msg. away from site for processing soma usually of the trunk of the main axon Afferent axons
Motor Neurons- excited by other neurons which results in excitation of muscle or glands cells soma at one end of cell. Impulse moves from soma to
axon hillock Efferent axons
Interneruons- (Most numerous). In between sensory and motor processing
Intrinsic Neurons- neuron that exists only within a singular structure
Slide 8: Got to Get Me Some GLIA!
Glia- the other cell size volume numbers early theory
Types- Astrocytes: chemical storage
star shaped
Oligodendrocytes: waste removal brain and spinal cord
Schwann Cells: build myelin sheath around axons Radial Glia: guiding neural and axon growth during
embryonic development (also Schwann Cells)
Slide 9: Neural Exercise II
1
2
3
4
5
6
7
Slide Slide 1010: Changes in Neural Structure: Changes in Neural Structure
Neuron Replacement- what happens when neurons die? A few exceptions (olfactory receptors)
Brain Cancer- an abnormal proliferation of cells, but not neurons...
Plasticity- production of new neural connections Changes in Cell Structures with Aging
dendrites shrinkage branching
– more– wider
senility patterns
Slide 11: Blood-Brain Barrier
Slide 12: The Blood-Brain Barrier
Tightly packed endothelial cells results- “little shall pass” oxygen, CO2, fatty soluble molecules active transport mechanism- pumps in necessary
molecules (glucose=brain food) Protection of the brain from “invaders”
viruses and natural killer cells (NKCs) cell death
viruses in the nervous system herpes
The price of protection.
Slide 13: The Action Potential
Electricity in a carbon-based being (that’s us) decay of signal need for specialized “wires” need for specialized “transmitters”
eye The concept of “potential energy”- “the capacity to be” The Resting Potential (-70 mV): the polarized cell
at rest, the cell is more negative on the inside than the outside
Microelectrode, see page 40 in Kalat
Slide 14: Forces Behind the Resting Potential
How does a cell maintain its resting potential (i.e., how is it that the cell doesn’t become neutrally
charged?) CONCENTRATION GRADIENT: the difference in
distribution of ions between inside and outside [balloon]
20x more Na+ on Outside 10x more K+ on Inside more Cl- on inside of cell
Selective Permeability- the bilipid layer membrane-larger ions (Na+) cannot pass at all.. A few (Cl-
and K+) pass through specialized “channels”. Sodium Potassium Pump (3 NA+ out, 2 K+ in )
active transport system- use of a lot of energy
Slide 15: Forces Behind the Resting Potential
ELECTRICAL GRADIENT (electrostatic pressure): differences in electrical charge between one ion and another. Will attract positive ion into the cell, and negative ions
out of the cell excess Na+ on outside
Putting it together--- CLICK HERE boardwork?
Why is it important that there be an action potential what happens if membrane become more permeable? “the poised bow & arrow”
Slide 16: The Action Potential- cell firing
Hyperpolarization- increased polarization
Depolarization- action potential moves toward a charge of zero mV (no longer polarized) Threshold- a certain level of depolarization in which an action potential (nerve impulse) will occur
All or None Law- if threshold is met, nerve impulse is generate, if not (subthreshold stimulation).. cell will not fire. Think about flushing the toilet
Slide 17: The Action Potential: why the change?
Voltage Activated Channels- permeability to sodium changes if a certain (more depolarized) is reached.
Typically flow of sodium is balanced by exit of potassium. At a given level, “throw open the Na gates and shut the K+ gates” (figure 1)
Excess concentration of K+ drives K+ out, voltage channels close stopping more NA+ from coming in (Fig 2).
The sodium-potassium pump--back toward the incr. AP
Figure 1 Figure 2
Slide 18:Anesthetics: Changing Nerve Permeability
What happens the flow of if K+ and Na+ is affected? Scorpion Venom