The Central Nervous System
The central nervous system (CNS)
consists of the spinal cord and brain.
The CNS receives and sends sensory
input and coordinates motor output.
17-1
Central Nervous System
17-2
The human brain
17-3
Fig. 49-15
Frontal lobe
Parietal lobe
Speech
Frontal
association
area
Somatosensory
association
area
Taste
Reading
Speech
Hearing
Smell
Auditory
association
area
Visual
association
area
Vision
Temporal lobe
Occipital lobe
The Cerebral Cortex
The cerebral cortex is a thin, highly
convoluted outer layer of gray matter
covering both hemispheres.
17-5
Parts of the Brain
Cerebrum is the forebrain
• Contains two hemispheres for coordinating
sensory and motor information
• Speech, reasoning, memory, personality,
may be located on one side only
Cerebral hemispheres
17-7
Cerebrum (Forebrain) Continued
- The two hemispheres are connected by the corpus
callosum allowing info to be shared between the
hemispheres
The cerebrum can be subdivided into 4 lobes
1. Frontal (walking, speech, intellect, judgment,
personality),
2. Temporal (hearing, smell, memory,
interpretation),
3. Parietal (interpreting sensory info receptors,
spatial understanding) and
4. Occipital (vision) lobes
Cerebrum Parts and Functions
17-9
Speech Centers in Cerebrum
-Broca’s area - part of the left hemisphere
where speech center is located
-part of the frontal lobe
-Wernicke’s area – understanding speech;
located in the temporal lobe
17-10
The lobes of a cerebral hemisphere
17-11
Other Parts of the Brain
• Brainstem: thalamus, pons, medulla
Pons and medulla control heart rate and
respiratory rate
• Cerebellum- balance and coordination
• Limbic System: memory, emotions, and
emotional memory
Older Brain Structures
The Brainstem
Older Brain Structures
The Thalamus
• Thalamus
–All the senses
EXCEPT smell
Older Brain Structures
The Cerebellum
• Cerebellum
–“Little brain”
-Controls balance,
agility, and
voluntary
movement with
the pons
Older Brain Structures
The Limbic System
• Limbic System
–Hippocampus
is involved with
memory
Older Brain Structures
The Limbic System:
The Amygdala
• Amygdala
–Aggression,
fear, & emotional
memories
and
Older Brain Structures
The Limbic System:
The Hypothalamus
• Hypothalamus
–Influence on the
pituitary gland
The Spinal Cord
The spinal cord extends from the base of
the brain through the vertebral canal.
A central canal holds cerebrospinal fluid.
Gray matter of the spinal cord forms an
“H” and contains neurons
White matter consists of nerve fibers
called “tracts” to and from the brain
17-19
Spinal cord
17-20
17-21
Functions of the Spinal Cord
-The spinal cord is the center for many
reflex arcs.
-It sends sensory information to the brain
and receives motor output from the brain
to the peripheral nerves for both control of
voluntary skeletal muscles and involuntary
internal organs.
-Severing the spinal cord produces
paralysis.
17-22
Reflex Arc
17-23
The Peripheral Nervous System
The peripheral nervous system (PNS)
contains nerves to the whole body
-Sensory nerves carry information to the
CNS, motor nerves carry information
away
-Humans have 12 pairs of cranial nerves
and 31 pairs of spinal nerves.
17-24
Cranial nerves
17-25
Spinal nerves
17-26
Somatic System
The somatic system means nerves to the skin and
skeletal muscles
17-27
Autonomic Nervous System
• All autonomic nerves are motor nerves that
regulate the organs of the body without
conscious control; involuntary
• Control exists in the medulla
• They work on smooth muscle (digestive system),
cardiac muscle (heart) and glands (exocrine &
endocrine)
• Responsible for maintaining homeostasis during
times of rest and during emergencies
Consists of two parts:
Sympathetic
– prepares the body for stress, including “fight or flight”
response
Parasympathetic
– restores normal balance; times of relaxation
– Functions are opposite those of the sympathetic nervous
system
Fig. 49-8
Sympathetic division
Parasympathetic division
Action on target organs:
Action on target organs:
Constricts pupil
of eye
Dilates pupil
of eye
Stimulates salivary
gland secretion
Inhibits salivary
gland secretion
Constricts
bronchi in lungs
Cervical
Sympathetic
ganglia
Relaxes bronchi
in lungs
Slows heart
Accelerates heart
Stimulates activity
of stomach and
intestines
Inhibits activity
of stomach and
intestines
Thoracic
Stimulates activity
of pancreas
Inhibits activity
of pancreas
Stimulates
gallbladder
Stimulates glucose
release from liver;
inhibits gallbladder
Lumbar
Stimulates
adrenal medulla
Promotes emptying
of bladder
Promotes erection
of genitals
Inhibits emptying
of bladder
Sacral
Synapse
Promotes ejaculation and
vaginal contractions