The nervous system is divided into the central nervous system (CNS) and peripheral nervous system (PNS). The CNS includes the brain and spinal cord. The PNS includes nerves connecting the CNS to other parts of the body. The PNS is further divided into the somatic and autonomic nervous systems. The autonomic nervous system regulates involuntary body functions and is divided into the sympathetic and parasympathetic nervous systems. The brain contains several parts that each have specific functions like processing sensory information, motor control, and regulating homeostasis. Neurons transmit signals as electrical impulses through a process involving ion exchanges across the cell membrane.

1. Unit 10 - The Nervous System
CNS, PNS, and associated components

2. The Big Picture
Nervous system is divided into two main categories:
Central Nervous system (CNS): Brain and Spinal Chord
Peripheral Nervous system (PNS): Nerves to/from CNS
PNS is further divided into:
Somatic (SoNS): Connects the CNS to voluntary
muscles
Autonomic (ANS): Regulates involuntary body functions

3. Big Picture Cont.
Autonomic is further divided into:
Sympathetic (SNS): “fight or flight”
Parasympathetic (PSNS): “rest and digest”

4. Nervous System Flow Chart

5. CNS
Parts and Functions

6. The Brain
The main components of the brain include:
cerebrum
corpus callosum
cerebellum
thalamus
hypothalamus
pituitary gland
medulla oblongata
meninges

7. Cerebrum

8. Cerebrum
ANATOMY
2 hemispheres
4 lobes (Frontal,
Parietal, Occipital,
Parietal) separated by
sulci.

9. Cerebrum
PHYSIOLOGY
Two hemispheres:
Right: creativity
Left: logic
Connected by the corpus callosum
CC is associated with integration of motor,
sensory, and cognitive functions between the
hemispheres.

10. Cerebrum
PHYSIOLOGY
Sulci differentiate the cerebrum into 4 lobes
Frontal Lobe: Reasoning, Movement, Problem
Solving
Parietal Lobe: Perception, Orientation, Recognition
Occipital Lobe: Visual processing
Temporal Lobe: Auditory stimuli, Speech, Memory

11. Cerebellum
ANATOMY
“Little Brain”
Two hemispheres with a highly folded surface.

12. Cerebellum
PHYSIOLOGY
Regulate eye movements
Coordinate limb movements
Maintain posture and balance
Motor decision making

13. Thalamus
Relays sensory
information from
the body to the
cerebral cortex.
Hypothalamus
Involved in: homeostasis, emotion, thirst, hunger,
circadian rhythms, and control of the autonomic nervous
system.
Control of the pituitary gland

14. Pituitary Gland
“Master
Gland” of the
endocrine
system
Under control
of the
hypothalamus

15. Pituitary Gland

16. Medulla Oblongata

17. Medulla Oblongata
Controls involuntary functions such as:
Respiration
Heart Rate
Digestion
Relays higher level brain centers with the spinal
chord.

18. Meninges
3 Layers
Dura Mater: outer layer closest to skull
Arachnoid Mater: provides cushioning effect for CNS
Pia Mater: attached to brain, contains capillaries
Subdural haematoma (btwn dura and arachnoid)
resulting from traumatic event causes bleeding and
inter cranial pressure and brain trauma

19. Remember...
The Peripheral Nervous System is composed of:
Sensory Neurons (Afferent Neurons)
Motor Neurons (Efferent Neurons)
What are these made of and how do they transport
signals?

20. Parts of Neurons
Receive signals from other nerve cells
Covered in synapses

21. Parts of Neurons
Conveys electrical signals (range from 0.1mm to 2m)
Point of contact w/ cell body = Axon Hillock

22. Parts of Neurons
Carry out basic life functions of the neuron, including
production of proteins and ATP.

23. Parts of Neurons
Protective covering of long Axons
Gaps btwn Schwann Cells are called Nodes of Ranvier

25. Sensory (Afferent) Neuron
Take information from
sensory receptors to
the CNS
Chemoreceptors are
specific to the function
they perform (taste,
pain, etc.)

27. Interneuron
Act as middle men
between sensory and
motor neurons
Reside completely
within the CNS
Have many varieties
and are multipolar
(more than one
dendrite)

29. Motor (Efferent) Neuron
Carry signals from CNS
to effectors
Effectors can be
glands or muscles as
examples.

30. Signal Generation
Electrical activity is due to movement of ions past
the cell membrane (Na+ and K+)
Neurons have an Electrical Charge Different from
the Extracellular Fluid that surrounds them. A
difference in electrical Charge between Two
Locations is called a POTENTIAL

31. Signal Generation
RESTING POTENTIAL
Positively charged Na+ pumped out of cell, K+ “leak” out
passively.
Causes a negative charge inside cell
Cell is now polarized and maintains this situation until
stimulated.

32. Signal Generation
THRESHOLD
Stimulation of the nerve is required to begin an
impulse down the nerve
One sufficient stimulation occurs we can say that a
THRESHOLD has been met
Once an impulse begins it can not be stopped,
hence an “all or none” system is employed by
neurons.

33. Signal Generation
ACTION POTENTIAL
Stimulation of the
nerve causes gates in
the neuron to open.
Gates allow positive
ions (Na+) to enter
neuron causing the
neuron to
DEPOLARIZE.

34. Signal Generation
ACTION POTENTIAL
After the impulse
passes K+ gates allow
K+ to leave cell
This causes
REPOLARIZATION of
the neuron.

35. Signal Generation
ACTION POTENTIAL
This depolarization
and repolarization is
what we call an action
potential or nerve
impulse.

36. Signal Generation
ACTION POTENTIAL
Na+/K+ pumps now
return the respective
ions to the proper side
of the cell membrane
This is called the
REFRACTORY period
No nerve signal can
propagate during this
period.

37. Signal Propagation
MYELINATION
Axons that are
myelinated propagate
signals faster
Signals jump between
the myelination
(nodes of ranvier)
Speeds of 200 m/s
can occur

38. The Synapse
Axons ends are slightly swollen and are called
AXON TERMINALS.
These terminals transmit signals with dendrites,
effectors (muscles) or receptors (sensors).
Small vesicles at the axon terminals contain
NEUROTRANSMITTERS.

39. The Synapse
NEUROTRANSMITTERS
Chemicals that are released into the synapse
Ex: Acetylcholine (ACh)
Join to receptors on neuron receiving the impulse
Cause membrane to become permeable to Na+ and a
depolarization of the neuron
Threshold is met, and a signal propagates along the
neuron.
Acetylocholinesterase rapidly breaks down ACh so that
the chemical signal stops

41. Reflex Arc

42. Reflex Arc
Sensory neurons are stimulated and send a signal
to the spinal chord
Interneurons relay the stimuli to motor neurons
Motor neurons send the signal to the effector
muscles
The Brain does not receive a signal before the
movement occurs and pain is not sensed until
after the effector has been stimulated

43. SYMPATHETIC
Fight or Flight
Increases HR
Inhibits digestion
Dilates pupils
Vasoconstriction
Increases respiration
PARASYMPATHETIC
Rest and Digest
Pupil constriction
Promotes digestion
Controls resting HR
Relaxes muscles
ANS BRANCHES