The Nervous System
Part III
The central nervous system
• The central nervous system consists of the brain and
spinal cord.
The spinal cord
• The spinal cord carries sensory information from receptors
all over the body to the brain, and relays motor information
from the brain to muscles, organs, and glands.
The brain
• Enclosed within the skull, the brain is surrounded by a
tough three-layer protective membrane called the
meninges.
• The meninges form the blood-brain barrier, which
determines what substances will reach the brain through
the circulatory system.
• Cerebrospinal fluid circulates between the innermost and
middle meninges of the brain and through the central canal
of the spinal cord.
Spinal tap
The brain
• Brain complexity is one characteristic that distinguishes
humans from other animals.
The forebrain
• The forebrain contains paired olfactory lobes, which
receive information about smell.
• The cerebrum consists of two very large hemispheres that
act as a major coordinating centre from which sensory
information and accompanying motor actions originate.
• The cerebral hemispheres are the “location” of speech,
reasoning, memory, and personality.
• The surface of the cerebrum is called the cerebral cortex.
• The cortex has many folds that increase surface area.
The corpus callosum
• Information stored on one side of the brain is not
necessarily present on the the other side.
• The corpus callosum is a large bundle of nerves that
allow communication between the two cerebral
hemispheres.
The lobes of the cerebrum
The lobes of the cerebrum
(forebrain)
Lobe
Function
Frontal lobe
• Motor areas control movement of voluntary muscles
(e.g., walking and speech).
• Association areas are linked to intellectual activities and
personality.
Temporal lobe • Sensory areas are responsible for vision and hearing.
• Association areas are linked to memory and
interpretation of sensory information.
Parietal lobe
• Sensory areas are responsible for touch and
temperature awareness.
• Association areas are linked to emotions and
interpreting speech.
Occipital lobe
• Sensory areas are responsible for vision.
• Association areas interpret visual information.
The primary motor cortex and
primary somatosensory cortex
Other parts of the forebrain
• Below the cerebrum is the thalamus, and immediately
below the thalamus is the (you guessed it!) hypothalamus.
A direct connection between the hypothalamus and the
pituitary gland unites the nervous system with the
endocrine system.
The midbrain and hindbrain
• The midbrain is less developed than the forebrain.
• The midbrain acts as a relay centre for eye and ear
reflexes.
• The hindbrain is found posterior to the midbrain and joins
with the spinal cord.
• The cerebellum, located underneath the cerebral
hemispheres, is the largest section of the hindbrain.
• The cerebellum coordinates all muscle actions, and
controls and synchronizes limb movements, balance, and
muscle tone.
The midbrain and hindbrain
• The pons (meaning “bridge”) is largely a relay station that
passes information between regions of the cerebellum and
between the cerebellum and the medulla.
• The posterior region of the hindbrain is the medulla
oblongata. Nerve tracts from the spinal cord and higher
brain centres run through the medulla, which acts as a
connection between the PNS and CNS.
• The medulla controls involuntary muscle action (including
breathing movements, muscles controlling blood vessel
diameter, and the maintenance of heart rate).
Anatomy of the human brain
Anything after here is just fun
stuff to know (i.e. it won’t be
on the quiz)
*WARNING: Graphic images
ahead. Viewer discretion is
strongly advised…
Human brain mapping
“That’s odd, I smell freshly
baked
peanut
butter
cookies….”
Human brain mapping
Phineas Gage - unintentional self-inflicted
frontal lobotomy, involving a tamping rod
and some dynamite…
Human brain mapping
Magnetic Resonance Image (MRI) of
a normal human brain
The autonomic nervous
system and homeostasis
• The autonomic system is made up of two distinct (and
often opposing) units: the sympathetic nervous system
and the parasympathetic nervous system.
Organ
Sympathetic
Parasympathetic
Heart
↑ heart rate
↓ heart rate
Digestive system
↓ peristalsis
↑ peristalsis
Liver
↑ release of glucose
Storage of glucose
Eyes
Dilates pupils
Constricts pupils
Bladder
Relaxes sphincter
Contracts sphincter
Skin
↑ blood flow
↓ blood flow
Adrenal gland
Causes release of
epinephrine
No effect
Drugs and the brain
• Many types of drugs (pharmaceutical or otherwise) mimic
naturally occuring neurotransmitters – these include painkillers, stimulants, depressants, and anaesthetics (both
general and local).
THE END