What does a Nervous System do for you?
•Detect (sense) changes in the
environment (light, sound, smell,
taste, touch, heat)
•Detect (sense) changes in the
internal environment (blood
pressure, blood chemistry,
temperature, etc.)
•Integrate and evaluate sensory
information
•Plan, problem-solve, predict
•Store and retrieve information
(memory)
•Control contractions of skeletal
muscles (movements / behavior)
•Control internal glands, muscles
(heart rate, hormone secretions,
metabolism)
The Nervous System Organization
Central Nervous System
- completely surrounded by bone
- suspended in cerebrospinal fluid
- covered by meninges
- protected by “blood-brain barrier”
Peripheral Nervous System
- nerves leaving and entering the
CNS
- motor nerves = control muscles
and glands
- sensory nerves = transmit
information to the CNS from sensory
receptors.
- emerge from cranial and spinal
nerves
How the Peripheral and Central Nervous Systems Interact
Cells of The Nervous System
Two neurons releasing
neurotransmitters that act on a
third neuron. The first two
neurons could be in the Central
Nervous System, and the third
might be a motor neuron leading
out to a muscle or gland.
Neurons
Neuroglia (supporting cells)
- Detect physical and chemical changes in their
environment
- Provide physical support to neurons
-Transmit electric impulses (action potentials) from
one end to the other (one cell may be more than 3
feet long)
- May be involved in processes such as
memory.
- Communicates with other neurons, muscles and
glands using chemicals called neurotransmitters.
- Provide electrical insulation to neurons
Motor neurons have their cell bodies in the spinal cord, but their
axons extend outward into the body to stimulate muscles or glands.
Spinal cord smear
Dendrites
Microglia
Terminal of a motor neuron axon - where the neuron stimulates
the muscle cell to contract.
Axon
Axon
terminus
Muscle
cell
Neuromuscular junction
(motor end plate)
Pyramidal cells (neurons) of the cerebral cortex
Action potentials are tiny electric impulses produced by neurons.
They are used for transmitting information away from the cell body
and toward the axon terminals. When they reach the axon
terminals, the action potentials cause the release of
neurotransmitter from the terminals.
When a neuron is stimulated, not every stimulus will cause an
action potential. The stimulus must be sufficient to cause the neuron
to reach threshold. Only then will an action potential be produced.
Cells of the
Central Nervous
System
Microglia immune-like cells
Oligodendrocyte
produce myelin
sheath
Astrocyte - blood
brain barrier
Ependymal cells
- line ventricles
and help produce
cerebrospinal fluid
A Single Action Potential
The Na/K ATPase pumps set up the necessary conditions
across the membrane of a neuron so that the neuron will
be capable of producing an action potential.
A. High Na outside (3 ions pumped out)
B. High K inside (2 ions pumped in)
C. Produces a transmembrane potential (-70 mV)
P
ATP
P
ADP
The Ventricles of the Brain Are Shown in Dark Blue
Lateral
Ventricle
Third
Ventricle
Fourth
Ventricle
Transverse Section Showing Lateral Ventricles
Central Sulcus
Gyrus (ridge)
Sulcus (groove)
Parietal
lobe
Occipital
lobe
cerebellum
Frontal
lobe
Temporal
lobe
cerebrum
Central Sulcus
Gyrus
(ridge)
Sulcus
(groove)
Transverse
Fissure
cerebellum
Lateral Fissure
Pons
Medulla oblongata
Post-Central Gyrus
Pre-Central Gyrus
Parietal Lobe
Frontal Lobe
Occipital Lobe
Temporal Lobe
Basal Nuclei are Found Deep Below the Cerebrum
Limbic System
- amygdala
- hippocampus
- cingulate gyrus
- hypothalamus
Corpus Callosum
Thalamus
Hypothalamus
Pituitary
Pons
Midbrain
Medulla oblongata
Olfactory
bulb
Optic
nerve
pons
cerebellum
Medulla
oblongata
Inferior View of Brain and Cranial Nerves
Nervous System showing
spinal nerves emerging
from the spinal cord
Small segment of spinal cord
Showing two pair of spinal nerves
Location of spinal cord inside
canal of vertebra
White matter
Ventral root
Gray matter
Dorsal root ganglion
Dorsal root
Organization of the Spinal Cord
dorsal root
Sensory neuron
cell body
Dorsal root
ganglion
sensory
Spinal nerve
Ventral
root
motor
Motor neuron
cell body
Simple Knee Jerk Reflex Coordinated by the Spinal Cord
Dorsal root
Dorsal root ganglion
Sensory neuron
Quadriceps muscle
Motor neuron
Ventral root
Withdrawal Reflex
interneuron