1. Unit 1D: The Central Nervous System

2. Protective Tissues The CNS consists of the brain and spinal cord
The CNS is surrounded by layers of protective tissue known as the meninges.
Swelling of the meninges due to bacterial or viral infection is known as meningitis.

3. CSF and the Ventricles
The brain has a series of internal chambers that make and distribute CSF. They are known as the ventricles.
CSF is made from blood in the ventricles and resembles blood plasma
The CSF:
Supports weight of brain (makes it neutrally buoyant)
Cushions it (protects from injury)
Maintains chemical balance
If there is a blockage to the draining of the CSF, brain damage can result

4. Spinal cord
Long cable of axons that connects the brain to the peripheral nervous system.
Runs down the inside of the vertebral column
Size:
As thick as your pinkie finger
Only 2/3 the length of the vertebral column (17-18in)
Function
Carries information through motor neurons from brain to muscles and glands
Carries information through sensory neurons from sense organs to brain
Creates some reflexes

5. Spinal Nerves (PNS)
Nerves branch off of the spinal cord at each vertebral joint.
These nerves follow blood vessels and carry sensory and motor neuron axons
The extent of damage from injury can be determined by location of injury

6. Hindbrain
The hindbrain is responsible for life-saving functions common to all vertebrates.
Major areas:
Cerebellum
Receives visual, auditory, vestibular and somatosensory information and coordinates it.
Works to make muscle movement smooth and coordinated.

7. Hindbrain (cont)
Pons
Involved in sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture
Also controls switch from inhalation to exhalation
Damage to this area can lead to “locked-in syndrome”
Aware and awake but unable to communicate!

8. Hindbrain (cont) Medulla
Regulates vital functions such as breathing, heart rate, blood pressure, etc.
It is the brain’s connection to the spinal cord.

9. Midbrain
Functions:
primary processing of auditory and visual information (before it is passed to thalamus and cortex)
In lower vertebrates, these are the only processing areas.
Motor functions
Species-typical behaviors
Sleep/arousal

10. Forebrain
Thalamus
Major relay center of information coming into the brain from the senses
Regulates states of sleeping and wakefulness

11. Forebrain Hypothalamus
rests below the thalamus and above the pituitary
It is the link between the autonomic nervous system and the endocrine system
It is responsible for maintaining homeostasis
hunger, thirst, body temp, sleep

12. Forebrain Basal Ganglia Involved in movement selection and initiation
Allows muscles to relax in motion

13. Forebrain Amygdala Hippocampus
Responsible for fear, aggression, emotion
Hippocampus
Responsible for formation of long-term memories

14. Forebrain Cerebrum: Cerebral Cortex
Largest part of human brain (most evolved)
Where conscious “thinking” takes place
Cerebral Cortex
Outer 3mm of cerebrum (surface area = 2.5ft2)
Highly convoluted (2/3 of area is in folds)
Mostly made of cell bodies of neurons (grey matter)
The rest of the cerebrum is made of the myelinated axons of these neurons and the fat makes this area look white - “white matter”

15. Regions of the Cortex In all cases:
the “primary cortex” area for a sense receives input directly from sense organs
Damage causes loss of sense
The “association areas” get input from primary cortex areas and process it. Also where memories tied to those senses are stored.
Damage causes loss of understanding
With the exception of taste and smell, the cortex receives information from the contralateral side of the body

16. Regions of the Cortex Visual Cortex and Association Area
Sight
Auditory Cortex and Association Area
Sound
Motor Cortex and Prefrontal Cortex (Motor Assoc. Area)
Controls movement and planning for movement
Specific areas control specific body parts.

17. Regions of the Cortex Somatosensory Cortex and Association Area
Strip that transects the cerebrum is divided into areas that respond to specific body parts (touch, feel, etc.)
The more input and processing required for a region, the more area it is given
Tongue/mouth and thumb/hand get most

18. Regions of the Cortex
The Cerebral Cortex is often divided in lobes based upon the bones on top of the areas:
Frontal lobe
Higher thinking, morality, decision making
Parietal Lobe
Integrates sensory info and determines spatial sense and navigation
Temporal Lobe
Auditory and visual processing, speech and long-term memory
Occipital Lobe
Vision and dreams

19. Regions of the Cortex
Some tasks are shared equally by the hemispheres, and some tasks are lateralized. Each hemisphere has a majority of responsibility for the following:
Left:
Sequence
Analysis
Details
Talking
Understanding
Reading
Writing
Right
Synthesis
Perceiving shape and size
Read maps
Building objects
Creativity
The Corpus Callosum bridges the gap between the two hemispheres.