WEEK 10 NERVOUS SYSTEM INTEGRATION NOTES
Some review and misc. parts
White matter. Made up of myelinated sheaths (which cover axons and dendrites). It
looks while because these sheaths are quite fatty.
Gray matter. This consists mostly of nerve cell bodies, as well as axons and dendrites
without the myelinated sheath.
Ventricles. These are spaces in the CNS that contain cerebrospinal fluid.
o Cerebrospinal fluid moves nutrients, hormones, and other substances around.
o It also acts as a shock absorber, particularly in the brain
o Nervous tissue generally has the consistency of watery jello. It’s very fragile.
o Meninges are made up of tough connective tissue and surround nervous tissue.
This helps protect nervous tissue; it also allows for cerebrospinal fluid to
o In the brain, meninges consist of:
The dura mater, which is an outer covering
The arachnoid membrane, which is a space in the middle and is also filled
with cerebrospinal fluid
The pia mater, which is the inner membrane lying right over the brain
The PNS, or Peripheral Nervous System:
This consists of paired spinal nerves and paired cranial nerves
o Spinal nerves come/go to the spinal cord, cranial nerves come/go to the brain
They are actually quite similar in structure
o Each set comes/goes to different structures. Except for a few cranial nerves (i.e.
optic nerves), each set contains both sensory and motor components
o Mammals have 12 pairs of cranial nerves (other groups like reptiles only have 10)
The PNS is divided into two broad groups:
o 1. Somatic – has sensory and motor nerves,
these are the ones that you have voluntary control over and that sense
the external environment.
o 2. Autonomic – generally not voluntary
this includes nerves that serve the internal organs
the autonomic system is actually divided into three parts, but let’s
skip the details
Integration – or, how does this work and fit together?
Example: a reflex arc (knee jerk reflex)
o Sensory neuron CNS motor neuron
o This is a very simple, straight forward pathway A reflex is a response that does not involve the brain
o Your leg responds without the brain being involved
o But – you can feel the response. So the signal does eventually get to the brain
How does a sensory signal get to the brain
o There are two pathways that lead to the brain. Both cross over to the other side
in the spinal cord
1. Sensory neuron thalamus sensory cortex
thalamus. This coordinates information coming from different
parts of the body and sends it to the correct spot in the cortex
cortex. This is the outer layer of the cerebrum
o cerebrum – higher functions take place here (more on this
o the sensory cortex is a special part of the cerebrum
2. Sensory neuron cerebellum
the cerebellum is a major area of motor coordination and motor
o for example, learning how to walk, play the piano or ride a
o sensory cortex
this receives information from different parts of the body. Each part of
the body can be represented on the surface of the sensory cortex.
The area on the sensory cortex is related to the # of receptors at
each part of the body
o For example, the fingers have many more receptors, and
also a much greater area on the sensory cortex
There are other pathways going into the brain as well:
Optic nerve (eventually) thalamus primary visual cortex
Taste receptors brainstem (pons, medulla) thalamus parietal lobe
Auditory nerve “superior olive” thalamus primary auditory cortex
o “superior olive” helps determine direction of sound
smell receptors cortex thalamus other parts of cortex
to summarize, all these pathways eventually wind up in the cortex, which as mentioned, is the
outer part of the cerebrum
o this is a highly folded structure: it is surface area rather than volume that
appears to contribute to intelligence
o no other animal has as many ridges and grooves as man. Next in line are actually
The cerebrum processes and integrates information from all parts of the body o Different areas of the cortex can be mapped to different functions such as
speech, pattern recognition, etc.
The cortex, particularly the frontal part, is where “intelligence” resides
So, information is received and processed
Then, if needed, the appropriate action can be taken
Another important part of the brain is the corpus callosum
o This moves information between the two halves of the cerebrum
If some action (response) is taken or needed, then the motor cortex receives information from
1. Occipital lobe
2. Temporal (hearing, memory, emotion)
3. Parietal lobes (sensory, spatial)
o all via the frontal association cortex, or lobe
o very similar to the sensory cortex – it maps parts of the body on it’s s