T H E B R A I N C O N T I N U E D

Nervous System

Review

White versus grey matter

Ventricles

4 brain regions

4 lobes of cerebral hemispheres

3 layers of cerebrum

Cortex

Motor

Sensory

Association

White matter tracts

Gray matter

Brain Regions

4 Adult brain regions 1. Cerebral hemispheres (cerebrum)

2. Diencephalon 3. Cerebellum

4. Brain stem (midbrain, pons, and medulla)

Diencephalon

Three paired structures

Thalamus

Hypothalamus

Epithalamus

Encloses the third ventricle

Figure 12.12

Corpus callosum

Choroid plexus Thalamus

(encloses third

ventricle)

Pineal gland

(part of epithalamus)

Posterior commissure

Corpora

quadrigemina Cerebral aqueduct Arbor vitae (of cerebellum)

Fourth ventricle Choroid plexus Cerebellum

Septum pellucidum

Interthalamic

adhesion

(intermediate

mass of

thalamus) Interven-

tricular

foramen

Anterior

commissure

Hypothalamus

Optic chiasma

Pituitary gland

Cerebral hemisphere

Mammillary body Pons

Medulla oblongata

Spinal cord

Mid-

brain

Fornix

Diencephalon

Thalamus

Several nuclei

Gateway of the cerebral cortex

Major relay station for most

sensory impulses

Diencephalon

Thalamus

Relay center for cerebral activation

Associated with reticular formation

Relay center for somatosensory information

Except olfaction

Coma is associated with thalamic injury

Vegetative state = damage to cortical pathways

Refer to diagram on CNS 8

Diencephalon

Hypothalamus

Inferior to the thalamus

Forms portions of walls of the third ventricle

Consists of a number of nuclei

Diencephalon

Hypothalamus Infundibulum

Mammillary bodies

Responsible for most neurogenic homeostasis of the body

Diencephalon

Hypothalamic function

Autonomic control center for many visceral functions

Examples

Blood pressure, rate and force of heartbeat

Regulates body temperature

Hunger and G.I tract regulation

Center for emotional response

Example

Tactile sexual response

Diencephalon

Hypothalamic Function

Water balance and thirst

Controls release of hormones by the anterior pituitary and produces posterior pituitary hormones

Regulation of sleep-wake cycles

Diencephalon

Epithalamus

Forms roof of third ventricle

Pineal gland, choroid plexus

Melatonin

We’ll discuss it’s endocrine function later….

Brain Regions

4 Adult brain regions 1. Cerebral hemispheres (cerebrum)

2. Diencephalon

3. Brain stem (midbrain, pons and medulla) 4. Cerebellum

The Brain Stem

Functions

Supports most of basic life functions

Pathway for fiber tracts

Origin for most cranial nerves

The Brain Stem

Midbrain

Associated with visual and auditory reflexes

Pupillary reflex

Cranial nerves III and IV

Red nucleus

Descending motor pathways involved in voluntary movement

Figure 12.14

Frontal lobe

Olfactory bulb

(synapse point of

cranial nerve I) Optic chiasma

Optic nerve (II)

Optic tract

Mammillary body

Pons

Medulla

oblongata

Cerebellum

Temporal lobe

Spinal cord

Midbrain

Figure 12.15a

Optic chiasma View (a)

Optic nerve (II)

Mammillary body

Oculomotor nerve (III)

Crus cerebri of

cerebral peduncles

(midbrain)

Trigeminal nerve (V)

Abducens nerve (VI) Facial nerve (VII)

Vagus nerve (X)

Accessory nerve (XI)

Hypoglossal nerve (XII)

Ventral root of first

cervical nerve

Trochlear nerve (IV)

Pons Middle cerebellar peduncle

Pyramid

Decussation of pyramids

(a) Ventral view

Spinal cord

Vestibulocochlear

nerve (VIII)

Glossopharyngeal nerve (IX)

Diencephalon

• Thalamus • Hypothalamus

Diencephalon

Brainstem

Thalamus

Hypothalamus

Midbrain

Pons

Medulla

oblongata

Figure 12.15b

View (b)

Crus cerebri of

cerebral peduncles

(midbrain)

Infundibulum

Pituitary gland

Trigeminal nerve (V)

Abducens nerve (VI)

Facial nerve (VII)

Vagus nerve (X)

Accessory nerve (XI)

Hypoglossal nerve (XII)

Pons

(b) Left lateral view

Glossopharyngeal nerve (IX)

Diencephalon

Brainstem

Thalamus

Hypothalamus

Midbrain

Pons

Medulla

oblongata

Thalamus

Superior colliculus

Inferior colliculus

Trochlear nerve (IV)

Superior cerebellar peduncle

Middle cerebellar peduncle

Inferior cerebellar peduncle

Vestibulocochlear nerve (VIII)

Olive

The Brain Stem

Pons

Bridge between midbrain and medulla oblongata

Connects cerebellum to cerebrum and spinal cord

Cranial nerves V- VIII (vestibular branch)

Figure 12.15b

View (b)

Crus cerebri of

cerebral peduncles

(midbrain)

Infundibulum

Pituitary gland

Trigeminal nerve (V)

Abducens nerve (VI)

Facial nerve (VII)

Vagus nerve (X)

Accessory nerve (XI)

Hypoglossal nerve (XII)

Pons

(b) Left lateral view

Glossopharyngeal nerve (IX)

Diencephalon

Brainstem

Thalamus

Hypothalamus

Midbrain

Pons

Medulla

oblongata

Thalamus

Superior colliculus

Inferior colliculus

Trochlear nerve (IV)

Superior cerebellar peduncle

Middle cerebellar peduncle

Inferior cerebellar peduncle

Vestibulocochlear nerve (VIII)

Olive

The Brain Stem

Medulla

Continuous with spinal cord

Passage of motor & sensory impulses between brain & spinal cord

Decussation of tracts in pyramids

Figure 12.10a

Corona radiata

Projection

fibers

Longitudinal fissure

Gray matter

White matter

Association

fibers

Lateral

ventricle

Fornix

Third

ventricle

Thalamus

Pons

Medulla oblongata Decussation

of pyramids

Commissural

fibers (corpus

callosum)

Internal

capsule

Superior

Basal nuclei

• Caudate

• Putamen

• Globus

pallidus

(a)

The Brain Center

Medulla

Vital centers

Cardiac

Vasomotor

Respiratory

Swallowing

Vomiting

Cranial nerves VIII (cochlear branch) -XII

Brain Regions

4 Adult brain regions 1. Cerebral hemispheres (cerebrum)

2. Diencephalon

3. Brain stem (midbrain, pons, and medulla)

4. Cerebellum

The Cerebellum

Dorsal to the pons & medulla

Subconsciously provides precise timing & appropriate patterns of skeletal muscle contraction

Contains both white & gray matter

Figure 12.17b

(b)

Medulla

oblongata Flocculonodular

lobe

Choroid

plexus of

fourth

ventricle

Posterior

lobe

Arbor

vitae

Cerebellar cortex

Anterior lobe

Cerebellar

peduncles • Superior • Middle • Inferior

The Cerebellum

Functions

Proprioception

Prime mover inhibition and antagonist activation

Dysmetria

Progression

Dysarthria

Functional Brain Systems

Networks of neurons that work together & span wide areas of the brain

Limbic system

Reticular formation

Functional Brain Systems

Limbic system

Structures on the medial aspects of cerebral hemispheres and diencephalon

Includes parts of the diencephalon and some cerebral structures that encircle the brain stem

Figure 12.18

Corpus callosum

Septum pellucidum

Olfactory bulb

Diencephalic structures

of the limbic system

•Anterior thalamic nuclei (flanking 3rd ventricle)

•Hypothalamus •Mammillary

body

Fiber tracts

connecting limbic system structures

•Fornix •Anterior commissure

Cerebral struc-

tures of the limbic system

•Cingulate gyrus •Septal nuclei •Amygdala •Hippocampus •Dentate gyrus •Parahippocampal gyrus

Functional Brain Systems

Limbic system Emotional brain

Recognizes angry or fearful facial expressions

Assesses danger & elicits the fear response

Plays a role in expressing emotions via gestures and resolves mental conflict

Connection to pre-frontal cortex allows us to “count to ten”

Puts emotional responses to odors

Example: skunks = smell bad

Functional Brain Systems

Reticular formation

Broad columns of nuclei along the length of the brain stem

Far-flung axonal connections with hypothalamus, thalamus, cerebral cortex, cerebellum & spinal cord

Figure 12.19

Visual impulses

Reticular formation

Ascending general sensory tracts (touch, pain, temperature)

Descending motor projections to spinal cord

Auditory impulses

Radiations to cerebral cortex

Functional Brain Systems

Functions of the reticular formation

1. Somatic motor control

Reticulospinal tract = improves smoothness of movement

2. Autonomic control

Respiratory and cardiovascular centers

3. Arousal

RAS = filter

4. Pain modulation

Can block pain transmission

Questions?

Homework due in Lab

PreLab #2

HW #2 – Synapses (page 1 and 2 in HW section)