Chapters 13 & 14

The Central Nervous System:

The Brain and Spinal Cord

BRAIN

The Brain

• 100 billion neurons

• 1.6 kg in males/1.45 kg in females(size is not representative of intelligence, only overall average body size)

• Complexity dictates processing power

Major Subdivisions of the Brain

1. Cerebrum

2. Cerebellum

3. Diencephalon– thalamus

– hypothalamus

4. Brain stem– midbrain

– pons

– medulla oblongata Fig. 14-2No functional area of the brain works alone

1. Cerebrum~ 80% of the brain’s mass; the

thinking center

2 cerebral hemispheres contain 4 distinct lobes:

• Frontal – motor cortex • Parietal – sensory cortex • Occipital – visual cortex • Temporal – auditory &

olfactory cortexFig. 14-8

Each hemisphere primarily controls the opposite side of the body

2. Cerebellum

• Coordination of movement

• Balance and posture

3. Diencephalon (INTERBRAIN)Thalamus - receives

sensory inputs and determines which of these signals to forward to the cerebral cortex

Hypothalamus - regulates the pituitary gland, body T, food intake, emotion, sleep-wake cycle and memory; controls autonomic functions (heart rate, respiration, blood pressure)

Limbic System

• The “emotional” center, important for perception of pleasure and pain & functions in memory formation

• Includes hypothalamus, hippocampus (long-term memory formation), amygdala (processing of emotions)

4. Brainstemlowest part of the brain where it connects to the

spinal cord

Midbrain – processing of visual & auditory data

Pons – contains respiratory center

Medulla oblongata – relays sensory info to thalamus & other parts of brainstem; controls cardiovascular, respiratory and digestive activities

Protection of the Brain

Several different mechanisms:• Skull & scalp hair • Meninges (connective tissue membranes wrapping

the CNS)• Cerebrospinal fluid (CSF) cushions and nourishes

the brain• Blood-brain barrier - separation of the CNS from

general circulation; composed of the least permeable capillaries; helps to maintain homeostasis in the brain

SPINAL CORD

Spinal Cord

• Connects the brain & PNS• Located within the

vertebral column • From brain stem through

foramen magnum to second lumbar vertebra (L2), ends as “horse tail”- cauda equina