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Biology of the Mind Neural and Hormonal Systems Worth/Palgrave/Macmillan Publishers. Chapter Objectives. To be familiar with the different parts of a neuron, as well as it types and functions. To be able to trace how neurons communicate with one another.

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Biology of the Mind

Neural and Hormonal Systems

Worth/Palgrave/Macmillan Publishers


Chapter Objectives

To be familiar with the different parts of a neuron, as well as it types and functions.

To be able to trace how neurons communicate with one another.

To be familiar with different parts of the nervous system and their functions

To identify parts of the endocrine system and their influence in human behavior


Chapter Objectives Cont.

To be familiar with Neurotransmitters, neuromodulators, endorphins, and hormones and their function(s).

To be familiar with the different ways of measuring brain activity.


Neural Communication

  • Biological Psychology
    • branch of psychology concerned with the links between biology and behavior
    • Other titles for biological psychologists include: behavioral neuroscientists, neuropsychologists, behavior geneticists, physiological psychologists, or biopsychologists
  • Neuron
    • a nerve cell – the single smallest functioning component of the nervous system
    • Specialized to receive, process, integrate, and transmit information – classified by function.

Neural Communication: Parts of a Neuron

  • Dendrite
    • the bushy, branching extensions of a neuron that receive messages and conduct impulses toward the cell body
  • Axon
    • the extension of a neuron, ending in branching terminal fibers, through which messages are sent to other neurons or to muscles or glands
  • Myelin [MY-uh-lin] Sheath
    • a layer of fatty cells segmentally encasing the fibers of many neurons
    • enables vastly greater transmission speed of neutral impulses

Neural Communication: Parts of a Neuron

  • Soma (cell body)
    • Contains the nucleus; may be in the middle, along the main line of the neuron(bipolar neuron), or on a branch of a nerve cell (multipolar neuron)
  • Node of Ranvier
    • The small constricted part of the neuron’s myelin sheath that separate the axons along the cell’s length.
  • Schwann Cells
    • Wrap themselves around each segment of myelin sheath covering each axon segment of the nerve cells and constrict at the Nodes of Ranvier.
    • The neurons of the brain and spinal cord do not have such a cell layer covering their myelin sheaths.

Neural Communication: Parts of a Neuron

  • Terminal Branches
    • Hair-like ends of axons that transport synaptic vesicles containing neurotransmitters to the terminal buttons where they are secreted into the synaptic gap
  • Terminal Button
    • Knob-like structures that release chemicals, i.e., neurotransmitters, into the space between the neurons, i.e., synaptic cleft (synaptic gap).

Neural Communication

  • Synapse [SIN-aps]
    • junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron
    • tiny gap at this junction is called the synaptic gap or cleft
  • Neurotransmitters
    • chemical messengers that traverse the synaptic gaps between neurons
    • when released by the sending neuron, neurotransmitters travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing whether it will generate a neural impulse

Neural Communication: Identifying Differen Neurons




(Sensory neuron)


(Motor neuron)

Pyrimidal Cell


Neural Communication

  • Action Potential
    • a neural impulse; a brief electrical charge that travels down an axon
    • generated by the movement of positively charged ions in and out of channels in the axon’s membrane
  • Threshold
    • the lowest level of stimulation required to trigger a neural impulse

Neural Communication

This depolarization produces another action potential farther along the axon. Gates in the neighboring area open, and move positively charged ions in, while the positively charged ions in the previous sections of the axon exit.

Cell body end

of axon

Direction of neural impulse: toward axon terminals


Neural Communication

  • Neurons vary with respect to their function:
  • Sensory neurons: (Afferent) Carry signals from the outer parts of your body (periphery) toward the central nervous system. Gather info from the environment and transmit it to the brain.
  • Motor neurons: (motoneurons) (Efferent) Carry signals away from the central nervous system to the outer parts (muscles, skin, glands) of your body. Responsible for accomplishing muscle movement.
  • Receptors: Sense the environment (chemicals, light, sound, touch) and encode this information into electrochemical messages that are transmitted by sensory neurons.
  • Interneurons: (a.k.a. association neuron, connecting neuron) - these neurons connect one neuron with another. Can be found in the central nervous system; responsible for perceiving, learning, remembering, planning, and deciding among other important neural activities.

Termination of

Post-synaptic Potentials

  • Reuptake - a rapid removal of neurotransmitter from the synaptic cleft by the terminal buttons
  • Enzymatic deactivation - enzymes destroy some neurotransmitter molecules into its constituents

Neural Communication

Serotonin Pathways

Dopamine Pathways

Neurotransmitters travel from one neuron to another. Changes occur in the receiving neuron’s membrane,

The ultimate effect is either:

Excitatory: the probability that the receiving neuron will fire increases

Inhibitory: the probability that the receiving neuron will fire decreases


Sleep, appetite, sensory perception, temperature regulation, pain suppression, and mood


Voluntary movement, learning, memory, and emotion


Muscle action, cognitive functioning, memory, and emotion


Increased heart rate and the slowing of intestinal activity during stress, learning, memory, dreaming, waking from sleep, and emotion


(gama-aminobutyic acid)

The major inhibitory neurotransmitter in the brain


Neural Communication

  • Acetylcholine [ah-seat-el-KO-leen]
    • a neurotransmitter that, among its functions, triggers muscle contraction; when inhibited, paralysis occurs
  • Endorphins [en-DOR-fins]
    • Short for endogenous (produced within) morphine
    • natural, opiate-like neurotransmitters
    • linked to pain control and to pleasure
  • They have an effect similar to that of opiates.
  • They reduce pain and promote pleasure.
  • They play a role in appetite, sexual activity, blood pressure, mood, learning, and memory.
  • Some endorphins function as neurotransmitters.
endorphins neuromodulators
Endorphins Neuromodulators

Most endorphins act as neuromodulators, which alter the effect of neurotransmitters by limiting or prolonging their effects.

**Neuromodulators are chemicals released by neurons in larger amounts and diffused for the longer distances, modulating the activity of many neurons in a particular part of the brain.

**Many neurons contain hormone receptors, thus influencing their activity.

how drugs and other chemicals alter neurotransmitters
The agonist molecule excites. It mimics the effects of a neurotransmitter on the receiving neuron.

Morphine mimics the action of neurotransmitters by stimulating receptors in the brain involved in mood and pain sensation.

The antagonist molecule inhibits by blocking the neurotransmitters or by diminishing their release.

Botulin poison causes paralysis by blocking receptors for acetylcholine (a neurotransmitter that produces muscle movement)

How Drugs and Other Chemicals Alter Neurotransmitters

Neural Communication



Receiving cell


Agonists excite: Morphine mimics the action of endorphins

Agonist mimics


Receptor site on

receiving neuron




Antagonists inhibit: Botulin (botox) paralyses muscle

neurotransmitters hormones

Shortage in acetylcholine may be associated with Alzheimer’s disease


The degeneration of brain cells that produce and use another neurotransmitter, dopamine, appears to cause symptoms of Parkinson’s disease.

Low levels of dopamine may cause ADHD

Neurotransmitters & Hormones
neurotransmitters hormones30

Decrease in norepinephrine and serotonin is associated with depression. Elevated levels along with other biochemical and brain abnormalities have been implicated in childhood autism.


Norepinephrine, epinephrine, and adrenaline are associated with excitement and stress.

Neurotransmitters & Hormones
neurotransmitters hormones31

Cortisol is associated with stress. Increase in cortisol damages the brain and may be associated with posttraumatic stress.


Abnormal GABA levels have between implicated in sleep and eating disorders and in compulsive disorders.


Glutamate, serotonin, and high levels of dopamine have been associated with schizophrenia

Neurotransmitters & Hormones

Produced by the pancreas

Regulates the body’s use of glucose & affects appetite


Secreted by the pineal gland

Helps to regulate daily biological rhythms and promotes sleep.

Sex Hormones

Are secreted by the gonads and by the adrenal glands


Masculinizing Hormones


Feminizing Hormones



  • When one brain area is damaged, other areas may in time reorganize and take over some of its functions.
  • If neurons are destroyed, nearby neurons may partly compensate for the damage by making new connections that replace the lost ones.
  • Examples:
    • How the sense of touch in blind men invades the visual part of the brain.
    • How the brain struggles to recover from a minor stroke.

Precursor Cells(Immature Cells)

  • Precursor cells can give birth to new neurons when immersed in a growth-promotion protein
  • Physical and mental exercise promote the survival and the production of new precursor cells
  • Stress can prohibit the production of new cells
  • Nicotine can kill precursor cells

Directions Relative

to the Neuroaxis

  • Anterior or Rostral- front end
  • Posterior or Caudal – the tail
  • Dorsal- the back surface
  • Ventral- front surface
  • Lateral-toward the side
  • Medial- toward the midline
  • Ipsilateral – same side of the body
  • Contralateral- opposite sides of the body
  • Cross section- slice transversely
  • Horizontal section-slice parallel to the ground (the brain)
  • Sagittal section- slice perpendicular to the ground and parallel to the neuroaxis

The Nervous System




(Cranial and Spinal nerves)


(brain and

spinal cord)

Autonomic (controls

self-regulated action of

internal organs and glands)

Skeletal (controls

voluntary movements of

skeletal muscles)






The Nervous System

  • Nervous System
    • The body’s fast and efficient, electrochemical communication system
    • Consists of all the nerve cells of the peripheral and central nervous systems
    • The human brain has approximately 100 billion neurons

The Nervous System: Structural Divisions

  • Central Nervous System (CNS)
    • the brain and spinal cord
  • Peripheral Nervous System (PNS)
    • the sensory and motor neurons that connect the central nervous system (CNS) to the rest of the body

The Nervous System: Functional Divisions

  • Voluntary Nervous System (a.k.a. Somatic)
    • Responsible for the willful control of skeletal muscles and conscious perception
    • Mediates voluntary reflexes

The Nervous System: Functional Divisions

  • Autonomic Nervous System (ANS)
    • Responsible for the self-regulating aspects of the body’s nervous network
    • Regulates involuntary smooth muscle movement, heart, glands
    • Comprised of 2 sub-systems:
      • Sympathetic
      • Parasympathetic

The Nervous System: Functional Divisions

  • Sympathetic Nervous System (SNS)
    • Causes the “fight or flight” responses in moments of stress or stimulus
      • Increasing heart rate
      • Saliva flow
      • Perspiration
      • Constriction of blood vessels
      • Contraction of involuntary smooth muscle
      • Dilating bronchial tubes
    • Excitatory

The Nervous System: Functional Divisions

  • Parasympathetic Nervous System (PNS)
    • Responsible for counter-balancing the effects of the SNS
      • Slows heart and respiration rates
      • Dilates blood vessels
      • Relaxes smooth involuntary muscles
    • Responsible for conserving and restoring energy in the body following a sympathetic response to stress
    • Inhibitory

The Nervous System


Sensory neuron

(incoming information)


Motor neuron




Spinal cord




Neural and Hormonal Systems

  • Hormones
    • Chemical messengers that travel through the bloodstream to target cells of body organs (including the brain).
    • Some are chemically identical to neurotransmitters
    • Target cells have receptors that latch only onto specific hormones
    • Influences growth, reproduction, metabolism, mood, response to stress, response to exertion, and response to one’s own thoughts.
    • When hormone level reach a certain normal or necessary amount, further secretion is controlled by important body mechanisms - negative feedback system
the hypothalamus
The Hypothalamus
  • The primary link between the endocrine and nervous systems
  • Controls the pituitary gland
  • Releasing hormones - signal the pituitary gland to secrete stimulating hormones
  • Somatostatin - causes the pituitary gland to stop the release of growth hormone
the pituitary gland
The Pituitary Gland
  • “Master gland” because it makes hormones that control several other endocrine glands
  • Can be influenced by factors such as emotions and seasonal changes
  • Hypothalamus relays these information
  • anterior lobe , posterior lobe
anterior lobe
Anterior lobe
  • Regulates the activity of the thyroid, adrenals, and reproductive glands
  • Growth hormone
  • Prolactin
  • Thyrotropin
  • Corticotrophin
  • Follicle-stimulating hormone
  • Leutinizing hormone
  • Endorphins
  • Gonadotropic hormones
posterior lobe
Posterior Lobe
  • Antidiuretichormone (vasopressin)
  • Oxytocin
the thyroid gland
The Thyroid Gland
  • Shaped like a bowtie or butterfly
  • Thyroxine , triiodothyronine - regulate metabolism; body temperature and weight
  • Iodine
  • If iodine lacks in his/her diet, the thyroid cannot make the hormones – Goiter
  • Calcitonin - regulation (reduction) of calcium level in the blood
the parathyroid gland
The Parathyroid Gland
  • Secrete parathyroid hormone, or parathormone
  • Parathormone - regulation (increase) of calcium level in the blood
  • Hypoparathyroidism - insufficient secretion of parathyroid hormone leading to increased nerve excitability.
adrenal glands
Adrenal Glands
  • Adrenal cortex
  • Adrenal medulla
adrenal cortex
Adrenal cortex
      • corticosteroids such as cortisone - influences or regulates salt and water balance in the body; body’s response to stress, metabolism, the immune system and sexual development -- Cortisol helps to generate energy; regulates conversion of carbs into glucose; suppresses inflammation
  • Steroid hormones in three classes:
    • Mineralocorticoids maintain electrolyte balance
    • Glucocorticoids produce a long-term, slow response to stress by raising blood glucose level through the breakdown of fats and proteins
    • Sex hormones
adrenal medulla
Adrenal medulla
  • Catecholamines, such as epinephrine / adrenolin - increases blood pressure and heart rate when the body experiences stress


***(Cortisol; Epinephrine; Adrenolin)

the pineal body
The Pineal body
  • Stimulated by the nerves from the eye
  • Melatonin - a hormone that may help regulate the wake-sleep cycle (circadian rhythm)
  • Secreted at night, when it is dark
  • Depressing the activity of the gonads
  • Affects thyroid and adrenal cortex functions
  • Seasonal affective disorder
  • Main source of sex hormones
    • Testes located in the scrotum
      • Androgens most important of which is testosterone
      • regulate body changes associated with sexual development
      • supports the production of sperm
gonads cont
Gonads cont.
  • Main source of sex hormones cont.
    • Ovaries, are located in the pelvis
      • Produce eggs
      • Estrogen - involved in the development of female sexual features
      • Progesterone - causes the uterine lining to thicken in preparation for pregnancy
      • Estrogen and progesterone - pregnancy and the regulation of the menstrual cycle
the pancreas
The Pancreas
  • Islets of Langerhans
  • Glucagon - tells the liver to take carbohydrate out of storage to raise a low blood sugar level
  • Insulin - tells the liver to take excess glucose out of circulation to lower a blood’s sugar level that’s too high
  • Diabetes mellitus

This signal that is picked up by each electrode is then amplified, stored and displayed on a monitor. We also measure several other physiological signals in conjunction with the EEG such as the ECG (heart function), respiration (lung function) and EMG (muscle function), as these recordings can influence the EEG.

We then analyse the EEG by visual inspection to assist in the diagnosis and prognosis of the newborn. Our analysis usually involves locating abnormal EEG in a recording. The normal EEG appears to be a random signal without any obvious pattern. The EEG becomes abnormal when certain patterns appear in the EEG and it loses the underlying randomness of a normal recording. The normal EEG pattern and several abnormal EEG patterns are shown in this figure .


Computerized Axial Tomography (CAT)

• CAT (or CT) scans use an X-ray source

that is moved around the head by steps.

• Detectors on the opposite side detect the

amount of radiation that is absorbed.

• This measures the density of brain



Magnetic Resonance Imaging (MRI)

• More detailed than CAT scans.

• The head is placed into a powerful magnetic field

(strong enough to lift a car!).

􀂃 This aligns all the brain’s protons in one


• The protons are then knocked over by a powerful

pulse of radio waves (loud!).

• The pulse is turned off and protons relax back to

their original position, giving off radio waves.

• Detectors around the head detect those waves.of radiation that is absorbed.

• This measures the density of brain



MRI scan of patient

with incipient Alzheime’s

Disease: Notable neural atrophy of the right hemisphere


Positron Emission Tomography (P.E.T.)

• Measures activity, not structure.

• A radioactive form of glucose is injected into the bloodstream.

• A ring of detectors maps the location of the radioactivity, as the glucose is taken up for energy.

• Subject may perform a task.

• Color is used to distinguish different levels of radioactive emissions.


Functional Magnetic Resonance Imaging(fMRI)

• Similar to regular MRI, except that high-powered, rapidly alternating magnetic fields are used to detect small changes in oxygen use.

• Good spatial and temporal resolution


Further reading on neonatal EEG can be found in,

G.B. Boylan, "Principles of EEG and CFM" in Neonatal Cerebral Investigation, Chapter 2, Eds:  J.M. Rennie, Robertson and Hagmann. Cambridge University Press, UK, 2008.

G.B. Boylan, J.M. Rennie, and D.M. Murray. "The normal neonatal EEG" in Neonatal Cerebral Investigation, Chapter 6, Eds:  J.M. Rennie, N.J. Robertson and C.F. Hagmann. Cambridge University Press, UK, 2008.

G.B. Boylan, "Neurophysiology in the Neonatal Period", in Neonatal and Paediatric Clinical Neurophysiology,  Eds: R.M. Pressler, C.D. Binnie, R. Cooper and R. Robinson, Churchill Livingstone Elsevier, The Netherlands, 2007