Nervous System Part 3: Central Nervous System & Peripheral Nervous System

Study Notes

Central Nervous System

Brain:
- Weighs 1.4 kg
- Lies in the cranial cavity
- Composed of:
  - Cerebrum
  - Thalamus
  - Hypothalamus
  - Midbrain
  - Pons
  - Medulla oblongata
  - Cerebellum
Cerebrum:
- Largest part of the brain
- Has 3 main functional areas associated with:
  - Mental activities (memory, intelligence, problem-solving, reflection, judgement, thinking, reasoning, initiative, inhibition, moral sense of responsibility, and learning)
  - Sensory perception (perception of pain, temperature, and touch)
  - Initiation and control of voluntary muscle contraction
- Cerebral cortex is highly wrinkled, increasing surface area and neuron density
- Divided into two hemispheres (left and right) by a deep furrow
  - Corpus callosum connects both hemispheres
Thalamus:
- Small structure that receives sensory information from the skin, viscera, and special sense organs
- Processes rudimentary perception of touch, pain, temperature
- Plays a role in arousal and the processing of emotions and complex reflexes
Hypothalamus:
- Situated within the cerebrum
- Attached to the pituitary gland
- Controls hormone release
- Controls autonomic nervous system effectors
- Involved in emotional reactions, hunger and thirst, body temperature regulation, and biological clocks
Midbrain:
- Composed of nuclei and nerve fibers that connect the cerebrum with lower parts of the brain and spinal cord
- Contains relay stations for ascending and descending nerve fibers
- Important for auditory and visual reflexes
Pons:
- Contains nerve fibers that form a bridge between the two hemispheres of the cerebrum
- Processes information from several cranial nerves
Medulla Oblongata:
- Continuous with the spinal cord
- Controls effectors (cardiovascular center, respiratory center)
- Contains reflex centers for coughing, vomiting, sneezing, and swallowing
Spinal Cord:
- Nerves carry impulses from the brain to organs and tissues
- Descend through the spinal column
- Starts in the medulla oblongata
- Elongated, cylindrical part of the CNS
- Suspended in the vertebral canal
- Surrounded by meninges and cerebrospinal fluid
- Approximately the thickness of a little finger (about 45 cm long)

Cerebrospinal Fluid

Clear, colorless fluid
Occupies the subarachnoid space in the brain
Acts as a cushion or buffer for the cortex
Renewed 4 times daily
Contains proteins, glucose, and lymphocytes

Functions of Cerebrospinal Fluid

Protection:
- Acts as a buffer that lessens the impact of blows to the head
Buoyancy:
- Reduces the brain's weight (from 1400g to 50g) to minimize pressure on the base of the brain
Excretion of waste products:
- One-way flow from the CSF to the blood takes away potentially harmful metabolites, drugs, and other substances from the brain
Endocrine medium for the brain:
- Transports hormones to specific areas of the brain