Transcript The Biological Basis of Behavior

The Biological Basis
of Behavior
The Nervous System and
Neural Transmission
Functions of the Nervous
System (NS)
1. The NS governs voluntary behaviors
(walking, talking) and thought processes.
2. The NS controls involuntary functions
needed for survival (breathing, cardiac
activity).
Branches of the Nervous System
The Nervous System
Central Nervous System
Peripheral Nervous System
Brain and Spinal Cord
Autonomic Nervous System
Parasympathetic NS
Sympathetic NS
(Fight or Flight)
Somatic Nervous System
CNS

The CNS is the body’s executive control
center.

It consists of the brain and spinal cord.
Peripheral Nervous System

Anything not encased in bone

Two branches: somatic and autonomic NSs

Somatic NS controls voluntary actions

Autonomic NS governs organ and gland
function
Symptoms of the Sympathetic NS:
“Fight” or “Flight” response

HR increases

Breathing increases

Sweating increases

Pupils dilate

Dry mouth
Symptoms of the Parasympathetic NS

HR decreases

Breathing decreases

Sweating decreases

Pupils constrict

Saliva is normal
Neurons: What are they?
 The
 We
cells of the NS.
have over 100 billion of these!!!
Types of Neurons

Sensory neurons -receive information from
environment.

Motor neurons – send signals to muscles
and glands to ready organism for action.

Interneurons – receive & send information
to other neurons.
Neuron Shapes
Parts of the Neuron cell

1. Cell body – control center for cell;
contains nucleus.

2. Dendrites – “tree-like” branches that
receive signals from other cells.

3. Axon – long branching arm where
impulses travel down cell.
Motor Neuron
Neural transmission

Communication “within” cells is
“electrical.”

Communication “between” cells is
“chemical.”
Resting neurons
A neuron at rest is more negatively charged
inside the cell than outside the cell.
The difference in voltage between the inside
and outside of the cell is called its resting
potential.
Forces to keep a cell at rest

1. Concentration gradient

2. Electrical gradient

3. Selective permeability

4. Sodium-Potassium pump
Summary

1. Na+, K+, & Cl- are unequally distributed
across the cell.

2. Na+ is driven to enter cell due to cell’s internal
negative charge & heavy concentration outside
cell.

3. K+ is driven to leave cell due to heavy
concentration inside the cell.

4. Na+ kept out through resistance of membrane
& pump. K+ kept in due to pump.
Action potentials
The cell fires, or sends an impulse
down its axon.
Operates according to the “all-or-none”
rule.
Summary: Action potentials

1. Na+ ions rush into cell driving charge up
from –70mV to +50 mV.

2. K+ ions leave cell due to their heavy
concentration inside the cell and the cell’s
new + charge. Cl- ions enter cell drawn by
cell’s + charge.

3. Na+ influx ceases, while K+ exflux
continues. Cell’s charge is now –72 mV
(hyperpolarized).
Synaptic transmission

Neurons communicate with one another by
releasing chemicals called
neurotransmitters.

Neurotransmitters: dopamine,
acetylcholine, serotonin, & norepineprhine
Otto Leowi’s work (1920)
Sequence of events in synaptic
transmission

1. Cell synthesizes neurotransmitters (NTs).

2. NTs transported down axon to end
buttons.
 3. NTs released from terminals.

4. NTs attach to receptors of postsynaptic
cell.
 5. NTs broken down and reabsorbed by
presynaptic neuron.
Synaptic transmission

When cell’s fire, Ca++ channels open in the
end terminal, release Ca++ ions.

Ca++ ions cause release of NTs at synaptic
cleft.
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This is why you should drink milk!!!!