CHAPTER 2

I. Gross and basic functional brain anatomy

{basic terminology: Afferent - towards CNS (e.g., sensory information; Efferent - away from CNS (e.g., motor information)}

A.Describing the body in 3-dimensional space.
1. Anatomical direction terms for planes used to divide body

a. dorsal-ventral plane
b. medial-lateral plane
c. anterior-posterior (also rostral-caudal (for tail)) plane

2.Planes of section: differ between animals with a straight neuraxis (like a rat) and humans.

a.for rat

i. Horizontal sections - divide brain along dorsal-ventral plane.
ii.Sagittal sections - divide brain along medial-lateral plane. Midsagittal section divides brain into two symmetrical halves.
iii.Coronal (for crown or corona) (also frontal) - divide brain along anterior posterior (also rostral-caudal) plane.

Coronal, horizontal, and sagittal planes for entire rat CNS.

b.For humans, coronal (also frontal), horizontal, and sagittal planes for brain, but coronal (frontal) becomes cross or transverse for spinal cord

For human brain:

i.Horizontal sections - same as rat, except plane directions are often called superior-inferior instead of dorsal-ventral.

ii.Sagittal sections - same as rat, divide brain along medial-lateral plane.

iii.Coronal - same as rat, except plane directions are often called anterior-posterior instead of rostral-caudal.

For human spinal cord:

i.Transverse - same as rat, where plane directions are usually called rostral caudal.

B. Subdivisions of nervous system
1. Central nervous system (CNS) - brain and spinal cord

2. Peripheral nervous system

a. somatic nervous system

b. autonomic nervous system (ANS)

i. sympathetic nervous system (SNS)

ii. parasympathetic nervous system (PNS)

C. Meninges
1. Dura mater

2. Arachnoid

3. Pia mater

D. Divisions of the adult brain
1. Forebrain (cerebrum)

a.telencephalon - cerebral cortex (neocortex), basal ganglia, olfactory bulbs, hippocampus, fornix, and amygdala. Many are C-shaped structures that surround the lateral ventricles.

b. diencephalon - thalamus, hypothalamus: structures that surround the third ventricle.

2.Midbrain or mesencephalon - tectum (roof, comprising the superior (vision) and inferior (audition) colliculi), tegmentum (floor, midbrain reticular formation (RF) and many other nuclei): structures that surround the cerebral aqueduct or aqueduct of Sylvius.

3. Hindbrain

a.metencephalon - pons (pontine RF), cerebellum: structures that surround the fourth ventricle.
b.myencephalon - medulla (medullary RF), pyramidal tract: structures that surround the central canal of the spinal cord.

E. Functional organization of the cortex

Cortex is convoluted, over two-thirds of the cortical area is hidden in the involutions. The bumps or hills of the convolutions are gyri (singular gyrus), and the valleys or depressions are sulci (singular sulcus). A fissure is a deep sulcus, but the terms are often used interchangeably.

1.Lobes of the cerebral hemispheres - medial longitudinal fissure separates the two hemispheres. Each hemisphere has the following lobes:

a.frontal lobe - defined by the central sulcus (of Rolando) and the lateral fissure (of Sylvius). Involved in attention, complex cognitive processing, and motor functions.

b.occipital lobe - defined by a line drawn from parieto-occipital fissure to preoccipital notch. Involved in vision.

c.parietal lobe - superior to a line drawn from the end of the lateral fissure to the middle of the line demarking the occipital lobe. Involved in somasthetic sensation and sensory integration.

d.temporal lobe - inferior to parietal lobe: the "thumb" of the cerebral hemisphere. Involved in audition and sensory integration.

2.Brodmann areas - alternative cortical classification scheme based upon the cellular structure (cytoarchitecture) of cortex.

F. Limbic System

Also called limbic "lobe," a term used to describe the structures surrounding the superior brainstem. There is some disagreement over precisely which structures should be included as part of the limbic system. However, the following areas surrounding the corpus callosum (the main structure consisting of axons that interconnect the two cerebral hemispheres):

1. Septum
2. cingulate gyrus
3. hippocampus
4. dentate gyrus
5. rentrospenial cortex

The main distinguishing feature of these areas is that they are "old" cortex, not neo cortex. The limbic system also includes the following nuclei that are related to the structures above:

6.amygdala
7. hypothalamus
8. anterior thalamus
9. sometimes the basal ganglia

Because the limbic system is so intimately related to the hypothalamus, and because neocortex has few direct projections to the hypothalamus, the limbic system is sometimes referred to as the "visceral brain." The limbic system is very important for the regulation of arousal and emotions.

G.Arterial blood supply

Strokes caused by blockage or rupture of a blood vessel supplying the brain. Loss of function is determined by which artery is compromised because different arteries supply specific brain areas. The extent and severity of the functional loss depends upon the location blockage or rupture in the artery and the severity of the insult.

1. Internal carotid arteries - supply most of cerebral hemispheres

a. anterior cerebral artery - supplies medial aspect of frontal and parietal lobes.
b.middle cerebral artery - runs along lateral fissure and supplies convexity between temporal and frontal lobes.

2. Vertebral-basilar system - the two vertebrals join to become the basilar artery.

a. vertebrals - supplies medulla, caudal cerebellum, and cervical spinal cord.
b. basilar - supplies pons, cerebellum and midbrain areas. Branches include:

i. superior cerebellar artery
ii. anterior inferior cerebellar artery
iii. posterior inferior cerebellar artery

c.posterior cerebral artery -(developed as part of internal carotid system, but functionally a part of the vertebral-basilar system) supplies occipital and temporal lobes

3.Circle of Willis - ring formed by artery system that becomes extremely important if a major (i.e., internal carotid or the basilar) artery gets blocked.

a. basilar
b. posterior cerebral
c. posterior communicating
d. internal carotid
e. anterior communicating

Normally very little flow in anterior and posterior communicating except when major artery gets blocked.

H.Cranial nerves

Have sensory (afferent), somatomotor (efferent), and parasympathetic (efferent) functions. The nuclei (collection of cell bodies) for these nerves are widely distributed throughout the RF (except for olfactory and optic).

1.Olfactory (sensory) -

2. Optic (sensory) - really part of diencephalon

3.Oculomotor (motor and PNS) - eye movements; pupillary constriction and light and accommodation reflexes

4. Trochlear (motor) - oblique eye movements

5.Trigeminal (sensory and motor) - touch sensations from face, scalp, teeth, motor to chewing mussels and some auditory muscles (e.g., tensor tympani)

6. Abducens (motor) - horizontal eye movements

7.Facial (sensory, motor, and PNS) - pain and temperature sensations from the ear, taste; facial muscles; salivation

8.Auditory-vestibular (sensory) - hearing(cochlea) and balance semicircle canals, utricle, saccule)

9.Glossopharyngeal (sensory, motor, and PNS) - taste; vocal muscles; salivation and barorecptors (stretch of artery) in carotid

10.Vagus (sensory, motor, and PNS) - widely distributed throughout the thorax and abdomen. Sensation from taste, viscera of throat (pharynx and larynx), heart, lungs, stomach and other digestive organs; motor to viscera of throat (pharynx and larynx); PNS to heart, lungs, digestive organs

11. Spinal-accessory (motor) - vocal, head, backs muscles

12. Hypoglossal (motor) - tongue muscles

I. Spinal cord

Collects sensory afferents and distributes motor efferents. Like rest of CNS, it consists of white and gray matter, but is organized with gray matter on the inside completely surrounded by white matter. Principal function is to transmit sensorimotor information, but also has rudimentary information processing capabilities in the form of reflex arcs. Spinal cord is supported by the vertebral column and is divided into segments according to the vertebra

Table 3
Veterbra, No. of Vertebra, No. of Nerve Pairs
Cervical, 7, 8
Thoracic, 12, 12
Lumbar, 5, 5
Sacral, 5, 5
Coccygeal, 1, 1

General morphology of the spinal cord is similar throughout its length: "butterfly-shaped" grey matter surrounding the central canal (which is filled with CSF and is continuous with the ventricular system) which is surrounded by white matter. Dorsal part is afferent: sensory neurons have their cell bodies in the dorsal root ganglion (collection of cell bodies outside of CNS) and synapse in posterior horn (dorsal) of the grey matter. Lateral grey matter is where the SNS preganglionic cell bodies are located. Anterior horn (ventral) grey matter is where the somatomotor cell bodies (alpha and gamma motor neurons) are located. SNS and somatomotor axons exit via the ventral root of the spinal nerve. Each spinal nerve innervates a specific area of the body (the dermatome).

J.ANS

Unlike the peripheral somatomotor nervous system (with cell bodies in the anterior horn and axons terminate at striated muscle), the peripheral ANS consists of a two neuron chain from the CNS to the effector organ. Cell bodies for the first neuron (preganglionic neuron) are in the CNS and the cell bodies for the second neuron in the chain are located in a peripheral ganglion (postganglionic neuron).

1.PNS (craniosacral) - most PNS preganglionic cell bodies are located in the cranial nerve nuclei, others are in the sacaral spinal cord. PNS ganglion are located close to organ so the axon for the preganglionic neuron can be quite long, but the axon for the postganglionic neuron will be quite short. PNS innervation is very specific and is usually said the be restorative, that is it increases the body's energy supply (slows heart rate, aids in digestion, etc.).

2.SNS (thoracolumbar) - SNS preganglionic cell bodies are located in the lateral grey matter of the spinal cord. SNS ganglion are located close to the spinal cord in the sympathetic chain of ganglion so the axon for the preganglionic neuron can be either short or long, enters the ganglion by the white ramus, synapses on the postganglionic neuron, and the axon for the postganglionic neuron exits the ganglion via the grey ramus and can be quite long. SNS innervation very diffuse (cell bodies from same location in the spinal cord can go to adjacent or distal ganglion) and usually increases the body's energy expenditure (increases heart rate, distributes blood to the muscles, etc.).

PNS and SNS are also distinguished by the postganglionic neuron's neurotransmitter: acetylcholine (muscarinic) for PNS (called the cholinergic system) and epinephrine (beta) and/or norepinephrine (alpha and beta) for the SNS (called the adrenergic system - except for sweat glands which are cholinergic). Preganglionic neuron for both systems emits acetylcholine (nicotinic).

II.Neuroanatomy

Perhaps 50 to 100 billion neurons in human nervous system. Each neuron may make from 1 to possibly 100's of connections with other neurons.

A.Parts of the neuron

1.Soma or cell body - metabolic functions of the cell and often where neurotransmitter substance is manufactured.

2. Dendrites (afferent to soma) - may be one or many

3. Axons (efferent to soma) -only one, but may branch at end to form collaterals

a.axonal hillock - where axon exits soma and where post-synaptic potential are summed to determine whether neuron will generate action potential.
b. terminal button (or buton) - neurotransmitter is stored here in vesicles and released
c.synapse - gap between terminal button and dendrite of next neuron. Synapses are not just of the axodendritic type, they can also be axoaxonic, somatoaxonic, somatosomatic, dendrodendritic, etc.

B. Support cells - myelination, acts like electrical insulator

1. Schwann cells - in periphery

2. Glia in brain - may also aid neuron metabolism

a. oligodendrocyte
b. astrocyte

C. Synaptic transmission

When action potential reaches terminal button, the change in potential causes synaptic vesicles to merge with terminal button (presynaptic) membrane (exocytosis) and release neurotransmitter into synaptic cleft to join with postsynaptic membrane. Some neurotransmitter are excitatory (increase the likelihood that the postsynaptic neuron will generate and action potential) and others are inhibitory (decrease the likelihood that the postsynaptic neuron will generate and action potential). Some major types of neurotransmitter are:

1. Amino acids - glutamate (E), aspartate (E), glycine (I), gama-amniobutyric acid (GABA) (I).
2.Monoamines - acetylcholine (E in CNS, I in PNS), dopamine (I), norepinephrine (E & I in CNS, SNS), epinephrine (E), serotonin (I).
3. Peptides - endorphins (E), substance P (E)
E = generally excitatory I = generally inhibitory

Neurons can release multiple neurotransmitters, and the neurotransmitter released can change with experience (type of transmitter and neuromodulator substances can both change), and the neurotransmitter released can differ according to the firing rate of the neuron (at least in ANS, but probably CNS, too).

D.Types of neuronal potentials
1. Resting potential

Determined by the permeability of the cellular membrane to Na+, K+, Cl-, and large anions (negative) so that inside of cell is about -70 mV relative to the outside.

2.Graded potentials - determined by the neurotransmitter. Proportional to size of the triggering stimulus. Decrease as they spread from point of origin

a.Excitatory postsynaptic potentials (EPSPs) - depolarization , where potential inside of cell becomes more positive (less negative) caused mainly by an increased membrane permeability to Na+ (because K+ is near equilibrium).
b.Inhibitory postsynaptic potentials (IPSPs) - hyperpolarization potential inside of cell becomes more negative caused mainly by an increased membrane permeability to Cl- (because K+ is near equilibrium).

3. Action potentials

a.threshold - if sum of EPSPs and IPSPs (over time and space) at axonal hillock exceeds a critical value (usually on the order of +30 mV), then an action potential will be generated along the entire length of the axon.
b.all-or-none - -70 mV to +40 mV change within 0.5 to 5 ms for different types of cells.
c.saltatory conduction - action potential "jumps" from node of Ranvier to node of Ranvier
d.conduction velocity - determined by myelination and diameter of the axon, faster with myelination and large diameter.
e. refractory periods - Na+/K+ pump takes time to restore resting potential

i. absolute - neuron cannot generate another action potential
ii.relative - neuron can only generate another action potential if a greater than "normal" depolarization

E.Physiological psychology is interested in "behavior" of individual neuron. Psychophysiology is interested in populations of neurons that respond in synchrony (EEG, ECG, EMG).

III. Electrophysiological measurement
A.Functional components need for psychophysiological assessment. Three categories of detection procedures: 1) measurement of biopotentials that originate in body tissue (e.g., EEG, ECG, EMG, EOG); 2) measurement of bioelectrical phenomena other than potentials (e.g., EDA); 3) measurement of physical (nonelectric) change (e.g., BP, respiration, temperature, activity).

1.Sensors for biopotentials that originate in body tissue

a. electrodes

2.Sensors of bioelectrical phenomena other than potentials

a. electrodes
b.transducer - = "sense organ for the electronic processing equipment" (Geddes & Baker, 1975, p. 3), usually taking advantage of Ohm's Law V=IR. Transducer converts one type of energy to resistance. V = volts, I = amperes, R = Ohms

3.Measurement of physical (nonelectric) change

a.Transducer

B.Purpose of biomedical instrumentation is to convert physiological phenomena to voltage that varies as a function of time. Need to know the electrical characteristics of the phenomenon of interest so that the signal can be properly conditioned. Need to separate signal from noise (artifact).
[

1. Gain (amplitude)

2. Filtering - frequency response

a. High-pass - cut-off frequency above which signals are permitted to pass.
b. Low-pass - cut-off frequency below which signals are permitted to pass.
c. Band-pass -cut-off frequencies between which signals are permitted to pass.

3. Common-mode rejection

C. Physiological phenomena can then be quantified to terms of their:

1. Frequency - spectral decomposition with FFT
2. Amplitude
3. Temporal characteristics

Figure 1. Sine wave parameters

D.Measurement units - can affect conclusions drawn about physiological phenomena. Compare two responses measured as skin resistance (in KW) versus skin conductance (in mS).
W = ohms (resistance unit) S = Siemans (conductance unit)

Table 4
Common Prefixes
10E3 thousand times kilo k
10E-3 thousandth milli m
10E-6 millionth micro m

Figure 2. Hypothetical skin resistance response

Figure 2

Figure 3. Hypothetical skin conductance response