Anatomy of the Central Nervous System
Divisions of the Mammalian Nervous System
Central Nervous System = the brain and the spinal cord
Peripheral Nervous System = the nerves outside the brain and
spinal cord
Two Divisions of the PNS
Somatic Nervous System - the nerves that convey messages
from the sense organs to and from the CNS
Autonomic Nervous System - a set of neurons that control the
heart, the intestines, and other organs
Nervous System
PNS
SNS
CNS
ANS
sympathetic
Brain
parasympathetic
Spinal Cord
The Nervous System
The Spinal Cord-part of the CNS found within the spinal column
The spinal cord communicates with the sense organs and
muscles below the level of the head
Bell-Magendie Law-the entering dorsal roots carry
sensory information …and the exiting ventral roots
carry motor information to the muscles and glands
Dorsal Root Ganglia - are clusters of neurons outside the
spinal cord
Figure 4.3 Diagram of a cross section through the spinal cord
The dorsal root on each side conveys sensory information to the spinal cord; the
Autonomic Nervous System
Sympathetic - prepares the Parasympathetic - facilitates
vegetative, non-emergency
body for activity
responses by the body’s organs
Increased breathing,
Increase digestive activity,
and heart rate,
activities opposing
decreased digestive
sympathetic system
activity
Consists of cranial nerves and
Form chain of ganglia
nerves from sacral spinal cord
just outside spinal
cord
Long preganglionic axons
extend from the spinal cord to
Short preganglionic
parasympathetic ganglia
axons release
close to each internal organ;
norepinephrine
release norepinephrine
Long postganglionic
Shorter postganglionic fibers
axons release
then extend from the
norepinephrine
parasympathetic ganglia in
the organs; release
acetylcholine
The Mammalian Brain
There are 4 main parts to the brain:
1. Hindbrain (cerebellum + medulla
oblongata)
2. Midbrain
3. Diencephalon ( thalamus +
hypothalamus)
4. Forebrain (cerebral hemispheres)
The Brain
The Hindbrain ( Posterior part of brain )
Medulla Oblongata - controls vital reflexes like
breathing,
heart beat
Blood pressure
(all via sympathetic and parasympathetic n.s.)
Cerebellum – controls movement, shifts of attention, balance and
coordination. Works by comparing intended with actual
movement.
Medulla oblongata
Para-sympathetic slows
down
Sympathetic speeds
up
Sino Atrial Node (SAN)
The Brain
The Midbrain - middle of the brain
Connects fore and hind brains.
Mainly responsible for movements such as head and eyes
focussing on an object.
The diencephalon
Thalamus
Centre of forebrain
Relay Station for sensory information (‘switchboard’)
Hypothalamus
Regulates homeostasis, sexual behavior, fighting,
feeding
Pituitary Gland
Endocrine gland attached to the base of the
hypothalamus (ADH, GH, FSH, TSH)
The Brain
The Forebrain - most anterior and most
prominent part of the mammalian brain,
comprising the…
Cerebrum (left and right cerebral hemispheres)
Figure 4.12 A sagittal section through the human brain
The Cerebrum
The cerebral hemispheres contain 109 nerve
cells in a layer only 3mm thick.
Left and Right hemispheres are linked by the
CORPUS CALLOSUM.
Each hemisphere has 4 LOBES:
i) Frontal
ii) Parietal
iii) Temporal
iv) Occipital
Frontal Lobe
The Frontal Lobe-extends from the central sulcus
(groove) to the anterior limit of the brain
Contains Primary Motor Cortex – responsible
for fine movements
Contributes to shifting attention, planning of
action, delayed response tasks as examples
Parietal Lobe
The Parietal Lobe - between occipital lobe and the
central sulcus
Contains the primary somato-sensory cortex –
i.e. receiving touch sensation, muscle-stretch
information and joint position information
Also, 3-D processing (visualisations, face
recognition etc)
Temporal Lobe
The Temporal Lobe - lateral portion of each
hemisphere, near the temples
Contains targets for hearing, essential for
understanding spoken language (Wernicke’s
Area), complex visual processes, emotional
and motivational behaviors
Occipital Lobe
The Occipital Lobe - posterior end of cortex
Contains primary visual cortex
Figure 4.20 Some major subdivisions of the human cerebral cortex
The four lobes: occipital, parietal, temporal, and frontal.
Which part of the brain contains:
The cerebrum?
Forebrain
The cerebellum?
Hindbrain
The medulla oblongata?
Hindbrain
Pituitary gland?
Diencephalon.
Which lobe of the cerebrum deals
with:
a)
b)
c)
d)
e)
memory
vision
language
hearing
spatial awareness
Essay for next week:
a) Outline the functions of the cerebrum in
the human brain.
b) Describe the changes that occur in the
cerebrum of a person with Alzheimer’s
disease and discuss the possible causes
of the disease.
Try a web search eg www.alz.org or
www.alzheimers.org