Download Cognitive Neuroscience

2: The Brain and
Nervous System
Cognitive Neuroscience
David Eagleman
Jonathan Downar
Chapter Outline
An Overview of the Nervous System
 The Peripheral Nervous System
 The Spinal Cord
 The Brainstem
 The Cerebellum
 The Diencephalon
 The Telencephalon
 Uniting the Inside and Outside Worlds

2
An Overview of the Nervous
System
Why Put Your Neurons in a Brain At All?
 The Common Features of Every Central
Nervous System
 Getting Oriented in the Brain

3
Why Put Your Neurons in a Brain
At All?
The nervous system is made of the brain,
spinal cord, and peripheral nerves.
 Bilateral symmetry provides several
survival advantages.
 For animals with bilateral symmetry, a
centrally-located nervous system is more
efficient.

4
The Common Features of Every
Central Nervous System
Precursors of neurons evolved about 600
million years ago.
 Neuronal circuits first appeared about 500
– 550 million years ago.
 Similar genes and proteins are used in
many animals to guide the development of
the nervous system.

5
The Common Features of Every
Central Nervous System
6
The Common Features of Every
Central Nervous System
Central nervous system interacts with the
rest of the body via the peripheral nervous
system.
 The brain develops from three bulges

 Prosencephalon
(forebrain)
 Mesencephalon (midbrain)
 Rhombencephalon (hindbrain)
 These bulges subdivide to form the adult
brain.
7
The Common Features of Every
Central Nervous System
8
The Common Features of Every
Central Nervous System
All neurons connect to and interact with
other neurons.
 The function of the neuron within the
nervous system depends on the
connections to that neuron.
 The functions and structure of the brain
have been shaped by evolution.

9
Getting Oriented in the Brain

There are specialized terms for directions
within the nervous system
– Caudal: Nose – tail axis
 Dorsal – Ventral: Back – belly axis
 Anterior – Posterior: Front – back axis
 Superior – Inferior: Top – bottom axis
 Rostral
10
Getting Oriented in the Brain
 Medial:
Towards the middle
 Lateral: Towards the side
 Ipsilateral: On the same side
 Contralateral: On the opposite side
 Distal: Far end of the limb
 Proximal: Nearest point of the limb, where it
attaches to the body
11
Getting Oriented in the Brain
12
Getting Oriented in the Brain

Three common planes are used to
describe images of the brain.
 Axial:
A horizontal slice, parallel to the floor
when standing up, from the front to the back
of the brain.
 Sagittal: A vertical slice through the brain,
separating the left side from the right side.
 Frontal (Coronal): A vertical slice, separating
the front from the back of the brain.
13
Getting Oriented in the Brain
14
The Peripheral Nervous System
Separate Systems for the Inner and Outer
Environments
 A Nervous System with Segmental
Organization

15
Separate Systems for the Inner
and Outer Environments
Sensory neurons collect information from
outside and inside the body.
 Motor neurons carry signals to the
muscles to enable movement.
 Neurotransmitters are specialized
chemicals released by neurons to
communicate with other cells.

16
Separate Systems for the Inner
and Outer Environments
17
Separate Systems for the Inner
and Outer Environments

Peripheral nervous system has two parts
 Somatic
nervous system
Deals with external world.
 Sensory and motor neurons carry information
about voluntary movement and conscious
awareness.

 Autonomic
nervous system
Deals with internal world.
 Sensory and motor neurons guide automatic
processes.

18
Separate Systems for the Inner
and Outer Environments

Autonomic nervous system is divided into
two components.
 Sympathetic
branch
Gets the body ready to react to threats.
 Increases heart and respiration rates and
increases blood pressure.

 Parasympathetic
branch
Calms the body down.
 Slows heart and respiration rate and increased
digestion.

19
Separate Systems for the Inner
and Outer Environments
20
A Nervous System with
Segmental Organization

The spine is divided into four segments
 Cervical
 Thoracic
 Lumbar
 Sacral

Peripheral nerve roots emerge from
between the vertebrae on both sides of the
spine and project out to the body.
21
A Nervous System with
Segmental Organization
22
A Nervous System with
Segmental Organization
Sensory input and motor output are
separated close to the spinal cord.
 Each peripheral nerve relates to a
particular part of the body, known as a
dermatome.

23
A Nervous System with
Segmental Organization
24
The Spinal Cord
Circuits within a Segment: Spinal Reflexes
 Complex Circuits across Segments:
Central Pattern Generators

25
Spinal Reflexes

The spinal cord is divided into gray matter
and white matter.
 The
gray matter contains the cell bodies and
dendrites of the neurons and is found near the
center of the cord.
 The white matter contains the electricallyinsulated long distance connections between
neurons.
26
Spinal Reflexes
27
Spinal Reflexes
The spinal cord is divided into laminae,
with sensory input occurring on the dorsal
side and motor output occurring from the
dorsal side.
 The dorsal root ganglia house the cell
bodies for the peripheral sensory neurons.

28
Spinal Reflexes
29
Spinal Reflexes
In a reflex arc, a sensory neuron connects
with a motor neuron, allowing the sensory
stimulation to trigger a movement.
 The knee-jerk reflex, where you extend
your leg after the doctor taps your knee
with a hammer, is an example of this.

30
Spinal Reflexes
31
Spinal Reflexes
Reflexes can have one or more
connections (synapses) between the
sensation and the motor response.
 Interneurons are neurons that are between
the sensory input and the motor output.
 Interneurons can be excitatory or
inhibitory.

32
Central Pattern Generators
More complex actions, such as walking,
are build from more simple spinal reflexes.
 Central pattern generators are functional
units of cells that guide these rhythmic
actions.

33
Central Pattern Generators
An excitatory neuron fires spontaneously,
until becoming fatigued and stopped by an
inhibitory interneuron.
 After a recovery time, the excitatory
neuron resumes firing.
 Inhibitory interneurons cross the midline to
inhibit the central pattern generator on the
contralateral side, to allow for rhythmic
muscle contractions.

34
Central Pattern Generators
35
The Brainstem
Medulla Oblongata and Pons
 Midbrain
 Most Cranial Nerves Emerge from the
Brainstem

36
Medulla Oblongata and Pons
The hindbrain is formed by the medulla
oblongata and the pons.
 The medulla controls involuntary functions
that are important for life, such as
breathing and heart rate.
 The pons relays information between the
cerebrum and the cerebellum.
 Cells within the pons are important for
sleep, arousal, and sensory functions.

37
Medulla Oblongata and Pons
38
Medulla Oblongata and Pons
Clusters of cells, called nuclei, process
sensory, motor, and visceral information.
 Circuits in the hindbrain are central pattern
generators for swallowing, yawning,
coughing, breathing, etc.

39
Midbrain
The superior colliculus locates visual
stimuli to help coordinate complex
movements.
 The inferior colliculus locates auditory
stimuli.
 Command generators influence activity of
central pattern generators in brain stem
and spinal cord.

40
Midbrain
Periaqueductal gray matter influences
complex behaviors such as defense,
aggression, or reproduction.
 Reticular formation regulates
consciousness.
 Locus coeruleus alerts the brain.
 Substantia nigra influences motor control
and cognition.

41
Midbrain
42
Most Cranial Nerves Emerge
from the Brainstem

Twelve pairs of cranial nerves transmit
sensory and motor information between
the brain and face.
43
Most Cranial Nerves Emerge
from the Brainstem
44
The Cerebellum
Circuitry of the “Little Brain”
 Functions of the Little Brain

45
Circuitry of the “Little Brain”
The cerebellum contains more neurons
than does the cortex.
 Neurons are densely packed into folia,
which are packed into lobules.
 Inputs come from brainstem nuclei.

46
Circuitry of the “Little Brain”
47
Functions of the Little Brain
Damage to cerebellum interferes with
coordinated movement to external targets.
 Cerebellum may make predictions about
expected outcomes of motor actions and
use these predictions to refine plans.
 Cerebellum is also important in language,
memory, attention, and emotion.

48
The Diencephalon
Hypothalamus: A Keystone Structure in
Homeostasis
 Thalamus

49
Hypothalamus: A Keystone
Structure in Homeostasis
Homeostasis is the process of maintaining
the body within a narrow range of
physiological parameters, such as
temperature, thirst, hunger, etc.
 Hypothalamus is important for
homeostasis.
 Nuclei within the hypothalamus regulate
homeostasis by comparing the body’s
state with set points.

50
Hypothalamus: A Keystone
Structure in Homeostasis
51
Hypothalamus: A Keystone
Structure in Homeostasis
If the body deviates from the set point,
compensation can happen via autonomic
responses, endocrine responses, or
behavioral responses.
 Hypothalamus releases hormones via the
pituitary gland to influence cells throughout
the body.

52
Hypothalamus: A Keystone
Structure in Homeostasis
53
Thalamus
The thalamus relays sensory signals to the
brain and motor signals to the body.
 More than 50 thalamic nuclei serve
sensory, motor, motivational, and
associational functions through reciprocal
connections with the cortex.

54
Thalamus
55
Thalamus
56
The Telencephalon
Cerebral Cortex
 Basal Ganglia

57
Cerebral Cortex
The cortex is the thin outer covering of the
brain that is necessary for human
cognition.
 The cortex contains six layers of cells,
known as gray matter, surrounding the
inner white matter.

58
Cerebral Cortex

Surface features of the cortex
 Gyri
(singular: gyrus): The rounded
convolutions of the cortex.
 Sulci (singular: sulcus): The grooves between
the gyri.
There are two hemispheres connected by
the corpus callosum.
 Each hemisphere has four lobes

59
Cerebral Cortex
60
Cerebral Cortex
61
Cerebral Cortex
62
Cerebral Cortex

Frontal Lobe
 Important

for motor control and planning.
Parietal Lobe
 Important
for processing somatosensory
information.

Occipital Lobe
 Processes

visual information.
Temporal Lobe
 Processes
auditory information.
63
Basal Ganglia
Gray matter structures within the white
matter of the cortex.
 Important for initiating and maintaining
activity in the cortex, particularly in motor
areas.

64
Basal Ganglia
Made up of the caudate and putamen,
known together as the striatum, and the
globus pallidus.
 Nearby structures, including the
subthalamic nucleus and the substantia
nigra, are functionally connected to the
basal ganglia.

65
Basal Ganglia
66
Uniting the Inside and Outside
Worlds
The Limbic System
 The Ventricular System and Brain
Function

67
The Limbic System
Combines sensory inputs from external
and internal environments to help control
the internal environment.
 Hypothalamus and limbic nuclei of
thalamus project to the limbic system.
 Amygdala is important for emotional
evaluation and learning.
 Hippocampus is also important for learning
and memory.

68
The Limbic System
69
The Limbic System
70
The Ventricular System and
Brain Function
Four spaces filled with cerebrospinal fluid
can be found at the center of the brain.
 Known as the lateral ventricles, the third
ventricle, and the fourth ventricle.

71
The Ventricular System and
Brain Function
72
The Four-Sided Brain
73